Σάββατο, 14 Απριλίου 2018

Quantitative evaluation of the tracer distribution in dopamine transporter SPECT for objective interpretation

Abstract

Purpose

Quantification of the tracer distribution would add objectivity to the visual assessments of dopamine transporter (DAT) single photon emission computed tomography (SPECT) data. Our study aimed to evaluate the diagnostic utility of fractal dimension (FD) as a quantitative indicator of tracer distribution and compared with the conventional quantitative value: specific binding ratio (SBR). We also evaluated the utility of the combined index SBR/FD (SBR divided by FD).

Materials and methods

We conducted both clinical and phantom studies. In the clinical study, 150 patients including 110 patients with Parkinsonian syndrome (PS) and 40 without PS were enrolled. In the phantom study, we used a striatal phantom with the striatum chamber divided into two spaces, representing the caudate nucleus and putamen. The SBR, FD, and SBR/FD were calculated and compared between datasets for evaluating the diagnostic utility. Mann–Whitney test and receiver-operating characteristics (ROC) analysis were used for analysis.

Results

ROC analysis revealed that the FD value had high diagnostic performance [the areas under the curve (AUC) = 0.943] and the combined use of SBR and FD (SBR/FD) delivered better results than the SBR alone (AUC, 0.964 vs 0.899; p < 0.001). The sensitivity, specificity, and accuracy, respectively, were 79.1, 85.0, and 80.7% with SBR, 84.5, 97.5, and 88.0% with FD, and 92.7, 87.5, and 91.3% with SBR/FD.

Conclusion

Our results confirmed that the FD value is a useful diagnostic index, which reflects the tracer distribution in DAT SPECT images. The combined use of SBR and FD was more useful than either used alone.



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Comparison of 125 I- and 111 In-labeled peptide probes for in vivo detection of oxidized low-density lipoprotein in atherosclerotic plaques

Abstract

Objective

Oxidized low-density lipoprotein (OxLDL) plays a pivotal role in atherosclerotic plaque destabilization, which suggests its potential as a nuclear medical imaging target. We previously developed radioiodinated 125I-AHP7, a peptide probe carrying a 7-residue sequence from the OxLDL-binding protein Asp-hemolysin, for specific OxLDL imaging. Although 125I-AHP7 recognized OxLDL, it had low stability. Thus, to improve stability, we designed radiolabeled 22-residue peptide probes, 125I-AHP22 and 111In-AHP22, which include the entire AHP7 sequence, and evaluated the stability, activity, and applications of these probes in vitro and in vivo.

Methods

Probes consisting of a 21-residue peptide derived from the Asp-hemolysin sequence and an N-terminal Cys or aminohexanoic acid for labeling with 125I-N-(3-iodophenyl)maleimide or 111In diethylene triamine pentaacetic acid were termed 125I-AHP22 and 111In-AHP22. An in vitro-binding inhibition assay with OxLDL was performed using 125I-AHP7 as a radiotracer. Radioactivity accumulation in the atherosclerotic aorta and plasma intact fraction was evaluated 30 min after intravenous administration of probes in myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits.

Results

125I-AHP22 and 111In-AHP22 were synthesized in ~ 360 and 60 min, respectively, with > 98% radiochemical purities after RP-HPLC purification. An in vitro-binding assay revealed similar or greater inhibition of OxLDL binding by both In-AHP22 and I-AHP22 compared to I-AHP7. The fraction of intact 125I-AHP22 and 111In-AHP22 in plasma was estimated to be approximately tenfold higher than that of 125I-AHP7. Both probes were rapidly cleared from the blood. 111In-AHP22 had a 2.3-fold higher accumulation in WHHLMI rabbit aortas compared to control rabbits, which was similar to 125I-AHP7. However, 125I-AHP22 accumulated to similar levels in aortas of WHHLMI and control rabbits due to high nonspecific accumulation in normal aortas that could be due to high lipophilicity.

Conclusions

111In-AHP22, easily prepared within 1 h, showed moderate affinity for OxLDL, high stability in vivo, and high accumulation in atherosclerotic aortas. 111In-AHP22 could be a potential lead compound to develop future effective OxLDL imaging probes.



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Multi-center reproducibility of structural, diffusion tensor, and resting state functional magnetic resonance imaging measures

Abstract

Purpose

The aim of this study is to assess multi-center reproducibility and longitudinal consistency of MRI imaging measurements, as part of a phase III longitudinal multi-center study comparing the neurotoxic effect following prophylactic cranial irradiation with hippocampal avoidance (HA-PCI), in comparison with conventional PCI in patients with small-cell lung cancer.

Methods

Harmonized MRI acquisition protocols from six participating sites and two different vendors were compared using both physical and human phantoms. We assessed variability across sites and time points by evaluating various phantoms and data including hippocampal volume, diffusion metrics, and resting-state fMRI, from two healthy volunteers.

Results

We report average coefficients of variation (CV) below 5% for intrascanner, intravendor, and intervendor reproducibility for both structural and diffusion imaging metrics, except for diffusion metrics obtained from tractography with average CVs ranging up to 7.8%. Additionally, resting-state fMRI showed stable temporal SNR and reliable generation of subjects DMN across vendors and time points.

Conclusion

These findings indicate that the presented multi-site MRI acquisition protocol can be used in a longitudinal study design and that pooling of the acquired data as part of the phase III longitudinal HA-PCI project is possible with careful monitoring of the results of the half-yearly QA assessment to follow-up on potential scanner-related longitudinal changes in image quality.



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Brain morphological and microstructural features in cryptogenic late-onset temporal lobe epilepsy: a structural and diffusion MRI study

Abstract

Purpose

Although epilepsy in the elderly has attracted attention recently, there are few systematic studies of neuroimaging in such patients. In this study, we used structural MRI and diffusion tensor imaging (DTI) to investigate the morphological and microstructural features of the brain in late-onset temporal lobe epilepsy (TLE).

Methods

We recruited patients with TLE and an age of onset > 50 years (late-TLE group) and age- and sex-matched healthy volunteers (control group). 3-Tesla MRI scans, including 3D T1-weighted images and 15-direction DTI, showed normal findings on visual assessment in both groups. We used Statistical Parametric Mapping 12 (SPM12) for gray and white matter structural normalization and comparison and used Tract-Based Spatial Statistics (TBSS) for fractional anisotropy and mean diffusivity comparisons of DTI. In both methods, p < 0.05 (family-wise error) was considered statistically significant.

Results

In total, 30 patients with late-onset TLE (mean ± SD age, 66.8 ± 8.4; mean ± SD age of onset, 63.0 ± 7.6 years) and 40 healthy controls (mean ± SD age, 66.6 ± 8.5 years) were enrolled. The late-onset TLE group showed significant gray matter volume increases in the bilateral amygdala and anterior hippocampus and significantly reduced mean diffusivity in the left temporofrontal lobe, internal capsule, and brainstem. No significant changes were evident in white matter volume or fractional anisotropy.

Conclusions

Our findings may reflect some characteristics or mechanisms of cryptogenic TLE in the elderly, such as inflammatory processes.



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Outcome of endovascular treatment for acute basilar artery occlusion in the modern era: a single institution experience

Abstract

Purpose

The beneficial effect of endovascular treatment (EVT) for patients with acute basilar artery occlusion (ABAO) remains uncertain. The purpose of the present study was to evaluate clinical outcome of EVT for patients with ABAO and analyze prognostic factors of good outcome.

Methods

From our prospectively established database, we reviewed all patients with ABAO receiving EVT during January 2014 to December 2016. Baseline characteristics and outcomes were evaluated. Favorable functional outcome was defined as modified Rankin Scale score of 0 to 3 assessed at 3-month follow-up. The association between clinical and procedural characteristics and functional outcome was assessed.

Results

Of the 68 patients included, 50 patients (73.5%) received mechanical thrombectomy with stent retriever device. Successful reperfusion (thrombolysis in cerebral infarction grades 2b–3) was achieved in 61 patients (89.7%). Overall favorable functional outcome was reached by 31 patients (45.6%). In univariate analysis, Glasgow Coma Scale sum score, baseline National Institutes of Health stroke scale score (NIHSS), and baseline glycemia level were identified predicting good clinical outcome. Multivariate analysis showed that lower NIHSS was the only independent risk factor of favorable functional outcome (OR 0.832; 95% CI, 0.715–0.968; p = 0.018). No difference of favorable outcomes was observed between the subgroups of time to EVT < 6 h and ≽ 6 h.

Conclusions

Data in the present study suggests that EVT for ABAO patients should be reasonable within 24 h of symptom onset. The most important factor determining clinical outcome is initial stroke severity.



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Stent placement in patients with acute subarachnoid haemorrhage: when is it justified?

Abstract

Purpose

Endovascular stents are widely used for the elective treatment of cerebral aneurysms. Acute stenting is performed in the management of dissections, pseudo-aneurysms, broad-based aneurysms or as a 'bail out' measure after coil migration. The purpose of this study is to review the safety of using stents in acute subarachnoid haemorrhage.

Methods

The stent registry of our institution was reviewed for procedures in patients with acute subarachnoid haemorrhage. Imaging studies were reviewed on the hospital's PACS system and the patients' notes were retrieved to assess complications and clinical outcomes. Procedures were analysed according to the type of stent, treatment indication, antiplatelet regime, complications and outcomes.

Results

Between 2008 and 2016, 51 stents were placed during 50 stenting procedures in 49 patients with acute subarachnoid haemorrhage. This included 24 patients with saccular aneurysms, 10 with blister aneurysms, 10 dissections and five fusiform aneurysms. Stents were deployed in 'bail out' situations on eight occasions. In six cases, flow-diverting stents were used. Eighteen patients (37%) in the cohort suffered a stroke. Nine patients (18%) suffered persistent clinical deficits as a result of the stenting procedure, all but one of which occurred within 24 h. Two patients had a transient ischaemic episode, and there was evidence of asymptomatic ischaemia on imaging in four cases (8%). Five patients died, three (6%) as a result of procedural complications. Twelve patients (25%) required a further embolisation procedure.

Conclusion

The use of stents in acute subarachnoid haemorrhage incurs a considerable complication risk and should be reserved for exceptional circumstances.



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Message from the Editor-in-Chief: Theranostic Imaging in 2018



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Elucidating early CT after pancreatico-duodenectomy: a primer for radiologists

Abstract

Pancreatico-duodenectomy (PD) represents the standard surgical treatment for resectable malignancies of the pancreatic head, distal common bile duct, periampullary region and duodenum, and is also performed to manage selected benign tumours and refractory chronic pancreatitis. Despite improved surgical techniques and acceptable mortality, PD remains a technically demanding, high-risk operation burdened with high morbidity (complication rates 40–50% of patients). Multidetector computed tomography (CT) represents the mainstay modality to rapidly investigate the postoperative abdomen, and to provide a consistent basis for an appropriate choice between conservative, interventional or surgical treatment. However, radiologists require familiarity with the surgically altered anatomy, awareness of expected imaging appearances and possible complications to correctly interpret early post-PD CT studies. This paper provides an overview of surgical indications and techniques, discusses risk factors and clinical manifestations of the usual postsurgical complications, and suggests appropriate techniques and indications for early postoperative CT imaging. Afterwards, the usual, normal early post-PD CT findings are presented, including transient fluid, pneumobilia, delayed gastric emptying, identification of pancreatic gland remnant and of surgical anastomoses. Finally, several imaging examples review the most common and some unusual complications such as pancreatic fistula, bile leaks, abscesses, intraluminal and extraluminal haemorrhage, and acute pancreatitis.

Teaching Points

• Pancreatico-duodenectomy (PD) is a technically demanding surgery burdened with high morbidity (40–50%).

• Multidetector CT is the mainstay technique to investigate suspected complications following PD.

• Interpreting post-PD CT requires knowledge of surgically altered anatomy and expected findings.

• CT showing collection at surgical site supports clinico-biological diagnosis of pancreatic fistula.

• Other complications include biliary leaks, haemorrhage, abscesses and venous thrombosis.



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Imaging of urgencies and emergencies in the lung cancer patient

Abstract

Lung cancer patients often experience potentially life-threatening medical urgencies and emergencies, which may be a direct or indirect result of the underlying malignancy. This pictorial review addresses the most common thoracic, neurological and musculoskeletal medical emergencies in lung cancer patients, including superior vena cava syndrome, pulmonary embolism, spontaneous pneumothorax, cardiac tamponade, massive haemoptysis, central airway obstruction, oesophagorespiratory fistula, malignant spinal cord compression, carcinomatous meningitis, cerebral herniation and pathological fracture. Emphasis is placed on imaging findings, the role of different imaging techniques and a brief discussion of epidemiology, pathophysiology and therapeutic options. Since early diagnosis is important for adequate patient management and prognosis, radiologists have a crucial role in recognising and communicating these urgencies and emergencies.

Teaching points

• Multiplanar multidetector computed tomography is the imaging examination of choice for thoracic urgencies and emergencies.

• Magnetic resonance imaging is the imaging modality of choice for investigating central nervous system emergencies.

• Urgencies and emergencies can be the initial manifestation of lung cancer.

• Radiologists have a crucial role in recognising and in communicating these urgencies/emergencies.



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Imaging the operated colon using water-enema multidetector CT, with emphasis on surgical anastomoses

Abstract

Water-enema multidetector CT (WE-MDCT) provides a detailed multiplanar visualisation of mural, intra- and extraluminal abnormalities of the large bowel, relying on preliminary bowel cleansing, retrograde luminal distension, pharmacological hypotonisation and intravenous contrast enhancement. In patients with a history of colorectal surgery for either carcinoma or Crohn's disease (CD), WE-MDCT may also be performed via a colostomy, which allows depicting the anatomy and position of the residual large bowel and evaluates the calibre, length, mural and extraluminal features of luminal strictures. Therefore, WE-MDCT may prove useful as a complementary technique after incomplete or inconclusive colonoscopy to assess features and suspected abnormalities of the surgical anastomosis, particularly when endoscopic or surgical interventions are being planned. This pictorial essay presents the WE-MDCT technique and pitfalls, the expected appearances after different colic surgeries and the imaging features of benign anastomotic disorders (fibrotic stricture, kinking, inflammatory ulcer) and of locally recurrent tumours and CD.

Teaching points

Water-enema multidetector CT (WE-MDCT) effectively visualises the operated colon

Complementary to endoscopy, WE-MDCT may helpfully depict abnormalities of surgical anastomoses

WE-MDCT allows assessment of strictures' features and abnormalities of the upstream bowel

Technical pitfalls, normal postsurgical findings and benign anastomotic disorders are presented

WE-MDCT allows detecting relapsing Crohn's disease, recurrent and metachronous tumours



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Multidetector CT of expected findings and complications after hysterectomy

Abstract

Indicated to manage a variety of disorders affecting the female genital tract, hysterectomy represents the second most common gynaecological operation after caesarean section. Performed via an open, laparoscopic or vaginal approach, hysterectomy is associated with non-negligible morbidity and occasional mortality. Iatrogenic complications represent a growing concern for gynaecologists and may result in prolonged hospitalisation, need for interventional procedures or repeated surgery, renal impairment and malpractice claims. As a result, radiologists are increasingly requested to investigate patients with suspected complications after hysterectomy. In the vast majority of early postoperative situations, multidetector CT represents the ideal modality to comprehensively visualise the surgically altered pelvic anatomy and to consistently triage the varied spectrum of possible injuries. This pictorial review provides an overview of current indications and surgical techniques, illustrates the expected CT appearances after recent hysterectomy, the clinical and imaging features of specific complications such as lymphoceles, surgical site infections, haemorrhages, urinary tract lesions and fistulas, bowel injury and obstruction. Our aim is to increase radiologists' familiarity with normal post-hysterectomy findings and with post-surgical complications, which is crucial for an appropriate choice between conservative, interventional and surgical management.

Teaching points

Hysterectomy via open, laparoscopic or vaginal route is associated with non-negligible morbidity.

• Multiplanar CT imaging optimally visualises the surgically altered pelvic anatomy.

• Familiarity with early post-hysterectomy CT and expected findings is warranted.

• Complications encompass surgical site infections, haemorrhages, bowel injury and obstruction.

• Urological complications include ureteral leakage, bladder injury, urinomas and urinary fistulas.



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Image-guided minimally invasive treatment for small renal cell carcinoma

Abstract

Surgical partial nephrectomy is still considered as the "gold standard" for the definitive management of small malignant renal masses, whereas treatment with image-guided percutaneous ablation is still mainly reserved for those patients who cannot undergo nephron-sparing surgical resection due to advanced age, underlying comorbidities or compromised renal function. Nonetheless, the recent evidence that underlines the long-term oncological equipoise of percutaneous ablation methods with surgical resection in combination with the reduced complication rate and cost supports the use of an image-guided minimally invasive approach as a first-line treatment. The purpose of this review is to offer an overview of the most widely used percutaneous renal ablation treatments (radiofrequency, microwave and cryoablation) with a focus on their main technical aspects and application techniques for curative ablation of small renal cell carcinoma (stage cT1a). The authors also provide a critical narrative of the relevant medical literature with an emphasis on outcomes of comparative effectiveness research, and appraise the percutaneous methods compared to surgery in the context of evidence-based practice and future research studies.

Teaching Points

RCC is a common cancer and is increasingly detected incidentally at early stages.

There is long-term oncological equipoise of percutaneous ablation compared to surgical resection.

Large-scale trials are required to produce Level 1a evidence.



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Abdominal imaging findings in adult patients with Fontan circulation

Abstract

The Fontan procedures, designed to treat paediatric patients with functional single ventricles, have markedly improved the patient's survival into adulthood. The physiology of the Fontan circuit inevitably increases systemic venous pressure, which may lead to multi-system organ failure in the long-term follow-up. Fontan-associated liver disease (FALD) can progress to liver cirrhosis with signs of portal hypertension. Focal nodular hyperplasia-like nodules commonly develop in FALD. Imaging surveillance is often performed to monitor the progression of FALD and to detect hepatocellular carcinoma, which infrequently develops in FALD. Other abdominal abnormalities in post-Fontan patients include protein losing enteropathy and pheochromocytoma/paraganglioma. Given that these abdominal abnormalities are critical for patient management, it is important for radiologists to become familiar with the abdominal abnormalities that are common in post-Fontan patients on cross-sectional imaging.

Teaching points

• Fontan procedure for functional single ventricle has improved patient survival into adulthood.

• Radiologists should be familiar with unique imaging findings of Fontan-associated liver disease.

• Focal nodular hyperplasia-like nodules commonly develop in Fontan-associated liver disease.

• Hepatocellular carcinoma, protein-losing enteropathy, pheochromocytoma/paraganglioma may develop.



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Malformed vertebrae: a clinical and imaging review

Abstract

A variety of structural developmental anomalies affect the vertebral column. Malformed vertebrae can arise secondary to errors of vertebral formation, fusion and/or segmentation and developmental variation. Malformations can be simple with little or no clinical consequence, or complex with serious structural and neurologic implications. These anomalies can occasionally mimic acute trauma (bipartite atlas versus Jefferson fracture, butterfly vertebra versus burst fracture), or predispose the affected individual to myelopathy. Accurate imaging interpretation of vertebral malformations requires knowledge of ageappropriate normal, variant and abnormal vertebral morphology and the clinical implications of each entity. This knowledge will improve diagnostic confidence in acute situations and confounding clinical scenarios.

This review article seeks to familiarize the reader with the embryology, normal and variant anatomy of the vertebral column and the imaging appearance and clinical impact of the spectrum of vertebral malformations arising as a consequence of disordered embryological development.

Teaching points

• Some vertebral malformations predispose the affected individual to trauma or myelopathy.

• On imaging, malformed vertebrae can be indistinguishable from acute trauma.

• Abnormalities in spinal cord development may be associated and must be searched for.

• Accurate interpretation requires knowledge of normal, variant and abnormal vertebral morphology.



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How to use the Kaiser score as a clinical decision rule for diagnosis in multiparametric breast MRI: a pictorial essay

Abstract

Due to its superior sensitivity, breast MRI (bMRI) has been established as an important additional diagnostic tool in the breast clinic and is used for screening in patients with an elevated risk for breast cancer. Breast MRI, however, is a complex tool, providing multiple images containing several contrasts. Thus, reading bMRI requires a structured approach. A lack of structure will increase the rate of false-positive findings and sacrifice most of the advantages of bMRI as additional work-up will be required. While the BI-RADS (Breast Imaging Reporting And Data System) lexicon is a major step toward standardised and structured reporting, it does not provide a clinical decision rule with which to guide diagnostic decisions. Such a clinical decision rule, however, is provided by the Kaiser score, which combines five independent diagnostic BI-RADS lexicon criteria (margins, SI-time curve type, internal enhancement and presence of oedema) in an intuitive flowchart. The resulting score provides probabilities of malignancy that can be used for evidence-based decision-making in the breast clinic. Notably, considerable benefits have been demonstrated for radiologists with initial and intermediate experience in bMRI. This pictorial essay is a practical guide to the application of the Kaiser score in the interpretation of breast MRI examinations.

Teaching Points

• bMRI requires standardisation of patient-management, protocols, and reading set-up.

• Reading bMRI includes the assessment of breast parenchyma, associated findings, and lesions.

• Diagnostic decisions should be made according to evidence-based clinical decision rules.

• The evidence-based Kaiser score is applicable independent of bMRI protocol and scanner.

• The Kaiser score provides high diagnostic accuracy with low inter-observer variability.



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Learning-based endovascular navigation through the use of non-rigid registration for collaborative robotic catheterization

Abstract

Purpose

Endovascular intervention is limited by two-dimensional intraoperative imaging and prolonged procedure times in the presence of complex anatomies. Robotic catheter technology could offer benefits such as reduced radiation exposure to the clinician and improved intravascular navigation. Incorporating three-dimensional preoperative imaging into a semiautonomous robotic catheterization platform has the potential for safer and more precise navigation. This paper discusses a semiautonomous robotic catheter platform based on previous work (Rafii-Tari et al., in: MICCAI2013, pp 369–377. https://doi.org/10.1007/978-3-642-40763-5_46, 2013) by proposing a method to address anatomical variability among aortic arches. It incorporates anatomical information in the process of catheter trajectories optimization, hence can adapt to the scale and orientation differences among patient-specific anatomies.

Methods

Statistical modeling is implemented to encode the catheter motions of both proximal and distal sites based on cannulation data obtained from a single phantom by an expert operator. Non-rigid registration is applied to obtain a warping function to map catheter tip trajectories into other anatomically similar but shape/scale/orientation different models. The remapped trajectories were used to generate robot trajectories to conduct a collaborative cannulation task under flow simulations. Cross-validations were performed to test the performance of the non-rigid registration. Success rates of the cannulation task executed by the robotic platform were measured. The quality of the catheterization was also assessed using performance metrics for manual and robotic approaches. Furthermore, the contact forces between the instruments and the phantoms were measured and compared for both approaches.

Results

The success rate for semiautomatic cannulation is 98.1% under dry simulation and 94.4% under continuous flow simulation. The proposed robotic approach achieved smoother catheter paths than manual approach. The mean contact forces have been reduced by 33.3% with the robotic approach, and 70.6% less STDEV forces were observed with the robot.

Conclusions

This work provides insights into catheter task planning and an improved design of hands-on ergonomic catheter navigation robots.



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Can tumor coverage evaluated 24 h post-radiofrequency ablation predict local tumor progression of liver metastases?

Abstract

Purpose

To assess the predictive value for local tumor progression (LTP) of geometrical tumor coverage using the contrast-enhanced (ce-)CT images acquired before and within 24 h after radiofrequency (RF) ablation.

Methods

Twenty patients (6 male and 14 female, median age 62 years) with 45 focal hypovascular liver metastases (16 colorectal carcinoma, 3 melanoma and 1 breast carcinoma) underwent RF ablation under CT-guidance and received a ce-PET/CT scan within 24 h post-procedure. Pre- and post-ablation ce-CT-images were aligned using an interactive procedure and used to verify the tumor coverage of the RF ablation. Results were correlated to LTP as recorded during follow-up performed every 2–3 months after the intervention (mean follow-up of 110 weeks) and compared to standard reading performed by three readers of the ce-CT images.

Results

Eleven tumors (25%) showed LTP during the follow-up period. One lesion, which did not show LTP, was excluded from analysis due to the poor quality of the alignment. For the remaining, 29 (66%) tumors were completely covered by the ablation zone, 9 (20%) were not, and for 6 (14%) tumors the edges coincided with the edge of the ablation zone. The sensitivity, specificity, PPV and NPV for LTP of having incomplete tumor coverage or no apparent ablative margin versus standard reading of ce-CT were 100, 88, 73 and 100% versus 42, 88, 58 and 82%, respectively.

Conclusions

Verifying the tumor coverage of liver metastases by an ablation zone through alignment of pre- and early post-ablation ce-CT images has a high predictive value for LTP.



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A photon recycling approach to the denoising of ultra-low dose X-ray sequences

Abstract

Purpose

Clinical procedures that make use of fluoroscopy may expose patients as well as the clinical staff (throughout their career) to non-negligible doses of radiation. The potential consequences of such exposures fall under two categories, namely stochastic (mostly cancer) and deterministic risks (skin injury). According to the "as low as reasonably achievable" principle, the radiation dose can be lowered only if the necessary image quality can be maintained.

Methods

Our work improves upon the existing patch-based denoising algorithms by utilizing a more sophisticated noise model to exploit non-local self-similarity better and this in turn improves the performance of low-rank approximation. The novelty of the proposed approach lies in its properly designed and parameterized noise model and the elimination of initial estimates. This reduces the computational cost significantly.

Results

The algorithm has been evaluated on 500 clinical images (7 patients, 20 sequences, 3 clinical sites), taken at ultra-low dose levels, i.e. 50% of the standard low dose level, during electrophysiology procedures. An average improvement in the contrast-to-noise ratio (CNR) by a factor of around 3.5 has been found. This is associated with an image quality achieved at around 12 (square of 3.5) times the ultra-low dose level. Qualitative evaluation by X-ray image quality experts suggests that the method produces denoised images that comply with the required image quality criteria.

Conclusion

The results are consistent with the number of patches used, and they demonstrate that it is possible to use motion estimation techniques and "recycle" photons from previous frames to improve the image quality of the current frame. Our results are comparable in terms of CNR to Video Block Matching 3D—a state-of-the-art denoising method. But qualitative analysis by experts confirms that the denoised ultra-low dose X-ray images obtained using our method are more realistic with respect to appearance.



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An intraoperative fluoroscopic method to accurately measure the post-implantation position of pedicle screws

Abstract

Purpose

Pedicle screw malplacement, leading to neurological symptoms, vascular injury, and premature implant loosening, is not uncommon and difficult to reliably detect intraoperatively with current techniques. We propose a new intraoperative post-placement pedicle screw position assessment system that can therefore allow surgeons to correct breaches during the procedure. Our objectives were to assess the accuracy and robustness of this proposed screw location system and to compare its performance to that of 2D planar radiography.

Methods

The proposed system uses two intraoperative X-ray shots acquired with a standard fluoroscopic C-arm and processed using 2D/3D registration methods to provide a 3D visualization of the vertebra and screw superimposed on one another. Point digitization and CT imaging of the residual screw tunnel were used to assess accuracy in five synthetic lumbar vertebral models (10 screws in total). Additionally, the accuracy was evaluated with and without correcting for image distortion and for various screw lengths, screw materials, breach directions, and vertebral levels.

Results

The proposed method is capable of localizing the implanted screws with less than 2 mm of translational error (RMSE: 0.7 and 0.8 mm for the screw head and tip, respectively) and less than \(2.3^{\circ }\) angular error (RMSE: \(1.3^{\circ }\) ), with minimal change to the errors if image distortion is not corrected. Breaches and their anatomical locations were all correctly visualized and identified for a variety of screw lengths, screw materials, breach locations, and vertebral levels, demonstrating the robustness of this approach. In contrast, one breach, one non-breach, and the anatomical location of three screws were misclassified with 2D X-ray.

Conclusion

We have demonstrated an accurate and low-radiation technique for localizing pedicle screws post-implantation that requires only two X-rays. This intraoperative feedback of screw location and direction may allow the surgeon to correct malplaced screws intraoperatively, thereby reducing postoperative complications and reoperation rates.



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Automated muscle segmentation from CT images of the hip and thigh using a hierarchical multi-atlas method

Abstract

Purpose

Patient-specific quantitative assessments of muscle mass and biomechanical musculoskeletal simulations require segmentation of the muscles from medical images. The objective of this work is to automate muscle segmentation from CT data of the hip and thigh.

Method

We propose a hierarchical multi-atlas method in which each hierarchy includes spatial normalization using simpler pre-segmented structures in order to reduce the inter-patient variability of more complex target structures.

Results

The proposed hierarchical method was evaluated with 19 muscles from 20 CT images of the hip and thigh using the manual segmentation by expert orthopedic surgeons as ground truth. The average symmetric surface distance was significantly reduced in the proposed method (1.53 mm) in comparison with the conventional method (2.65 mm).

Conclusion

We demonstrated that the proposed hierarchical multi-atlas method improved the accuracy of muscle segmentation from CT images, in which large inter-patient variability and insufficient contrast were involved.



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Patient-specific catheter shaping for the minimally invasive closure of the left atrial appendage

Abstract

Purpose

The minimally invasive closure of the left atrial appendage is a promising alternative to anticoagulation for stroke prevention in patients suffering from atrial fibrillation. One of the challenges of this procedure is the correct positioning and the coaxial alignment of the tip of the catheter sheath to the implant landing zone.

Method

In this paper, a novel preoperative planning system is proposed that allows patient-individual shaping of catheters to facilitate the correct positioning of the catheter sheath by offering a patient-specific catheter shape. Based on preoperative three-dimensional image data, anatomical points and the planned implant position are marked interactively and a patient-specific catheter shape is calculated if the standard catheter is not considered as suitable. An approach to calculate a catheter shape with four bends by maximization of the bending radii is presented. Shaping of the catheter is supported by a bending form that is automatically generated in the planning program and can be directly manufactured by using additive manufacturing methods.

Results

The feasibility of the planning and shaping of the catheter could be successfully shown using six data sets. The patient-specific catheters were tested in comparison with standard catheters by physicians on heart models. In four of the six tested models, the participating physicians rated the patient-individual catheters better than the standard catheter.

Conclusion

The novel approach for preoperatively planned and shaped patient-specific catheters designed for the minimally invasive closure of the left atrial appendage could be successfully implemented and a feasibility test showed promising results in anatomies that are difficult to access with the standard catheter.



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Registration of 3D freehand ultrasound to a bone model for orthopedic procedures of the forearm

Abstract

Purpose

For guidance of orthopedic surgery, the registration of preoperative images and corresponding surgical plans with the surgical setting can be of great value. Ultrasound (US) is an ideal modality for surgical guidance, as it is non-ionizing, real time, easy to use, and requires minimal (magnetic/radiation) safety limitations. By extracting bone surfaces from 3D freehand US and registering these to preoperative bone models, complementary information from these modalities can be fused and presented in the surgical realm.

Methods

A partial bone surface is extracted from US using phase symmetry and a factor graph-based approach. This is registered to the detailed 3D bone model, conventionally generated for preoperative planning, based on a proposed multi-initialization and surface-based scheme robust to partial surfaces.

Results

36 forearm US volumes acquired using a tracked US probe were independently registered to a 3D model of the radius, manually extracted from MRI. Given intraoperative time restrictions, a computationally efficient algorithm was determined based on a comparison of different approaches. For all 36 registrations, a mean (± SD) point-to-point surface distance of \(0.57\,(\pm \,0.08)\,\hbox {mm}\) was obtained from manual gold standard US bone annotations (not used during the registration) to the 3D bone model.

Conclusions

A registration framework based on the bone surface extraction from 3D freehand US and a subsequent fast, automatic surface alignment robust to single-sided view and large false-positive rates from US was shown to achieve registration accuracy feasible for practical orthopedic scenarios and a qualitative outcome indicating good visual image alignment.



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Self-guided training for deep brain stimulation planning using objective assessment

Abstract

Objective

Deep brain stimulation (DBS) is an increasingly common treatment for neurodegenerative diseases. Neurosurgeons must have thorough procedural, anatomical, and functional knowledge to plan electrode trajectories and thus ensure treatment efficacy and patient safety. Developing this knowledge requires extensive training. We propose a training approach with objective assessment of neurosurgeon proficiency in DBS planning.

Methods

To assess proficiency, we propose analyzing both the viability of the planned trajectory and the manner in which the operator arrived at the trajectory. To improve understanding, we suggest a self-guided training course for DBS planning using real-time feedback. To validate the proposed measures of proficiency and training course, two experts and six novices followed the training course, and we monitored their proficiency measures throughout.

Results

At baseline, experts planned higher quality trajectories and did so more efficiently. As novices progressed through the training course, their proficiency measures increased significantly, trending toward expert measures.

Conclusion

We developed and validated measures which reliably discriminate proficiency levels. These measures are integrated into a training course, which quantitatively improves trainee performance. The proposed training course can be used to improve trainees' proficiency, and the quantitative measures allow trainees' progress to be monitored.



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Ultrasound thermal monitoring with an external ultrasound source for customized bipolar RF ablation shapes

Abstract

Purpose

Thermotherapy is a clinical procedure which delivers thermal energy to a target, and it has been applied for various medical treatments. Temperature monitoring during thermotherapy is important to achieve precise and reproducible results. Medical ultrasound can be used for thermal monitoring and is an attractive medical imaging modality due to its advantages including non-ionizing radiation, cost-effectiveness and portability. We propose an ultrasound thermal monitoring method using a speed-of-sound tomographic approach coupled with a biophysical heat diffusion model.

Methods

We implement an ultrasound thermometry approach using an external ultrasound source. We reconstruct the speed-of-sound images using time-of-flight information from the external ultrasound source and convert the speed-of-sound information into temperature by using the a priori knowledge brought by a biophysical heat diffusion model.

Results

Customized treatment shapes can be created using switching channels of radio frequency bipolar needle electrodes. Simulations of various ablation lesion shapes in the temperature range of 21–59  \(^\circ \) C are performed to study the feasibility of the proposed method. We also evaluated our method with ex vivo porcine liver experiments, in which we generated temperature images between 22 and 45  \(^\circ \) C.

Conclusion

In this paper, we present a proof of concept showing the feasibility of our ultrasound thermal monitoring method. The proposed method could be applied to various thermotherapy procedures by only adding an ultrasound source.



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Biomechanics-based graph matching for augmented CT-CBCT

Abstract

Purpose

Augmenting intraoperative cone beam computed tomography (CBCT) images with preoperative computed tomography data in the context of image-guided liver therapy is proposed. The expected benefit is an improved visualization of tumor(s), vascular system and other internal structures of interest.

Method

An automatic elastic registration based on matching of vascular trees extracted from both the preoperative and intraoperative images is presented. Although methods dedicated to nonrigid graph matching exist, they are not efficient when large intraoperative deformations of tissues occur, as is the case during the liver surgery. The contribution is an extension of the graph matching algorithm using Gaussian process regression (GPR) (Serradell et al. in IEEE Trans Pattern Anal Mach Intell 37(3):625–638, 2015): First, an improved GPR matching is introduced by imposing additional constraints during the matching when the number of hypothesis is large; like the original algorithm, this extended version does not require a manual initialization of matching. Second, a fast biomechanical model is employed to make the method capable of handling large deformations.

Results

The proposed automatic intraoperative augmentation is evaluated on both synthetic and real data. It is demonstrated that the algorithm is capable of handling large deformations, thus being more robust and reliable than previous approaches. Moreover, the time required to perform the elastic registration is compatible with the intraoperative navigation scenario.

Conclusion

A biomechanics-based graph matching method, which can handle large deformations and augment intraoperative CBCT, is presented and evaluated.



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Experimental validation of robot-assisted cardiovascular catheterization: model-based versus model-free control

Abstract

Purpose

In cardiac electrophysiology, a long and flexible catheter is delivered to a cardiac chamber for the treatment of arrhythmias. Although several robot-assisted platforms have been commercialized, the disorientation in tele-operation is still not well solved. We propose a validation platform for robot-assisted cardiac EP catheterization, integrating a customized MR Safe robot, a standard clinically used EP catheter, and a human–robot interface. Both model-based and model-free control methods are implemented in the platform for quantitative evaluation and comparison.

Methods

The model-based and model-free control methods were validated by subject test (ten participants), in which the subjects have to perform a simulated radiofrequency ablation task using both methods. A virtual endoscopic view of the catheter is also provided to enhance hand-to-eye coordination. Assessment indices for targeting accuracy and efficiency were acquired for the evaluation.

Results

(1) Accuracy: The average distance measured from catheter tip to the closest lesion target during ablation of model-free method was 19.1% shorter than that of model-based control. (2) Efficiency: The model-free control reduced the total missed targets by 35.8% and the maximum continuously missed targets by 46.2%, both indices corresponded to a low p value ( \(\le 0.05\) ).

Conclusion

The model-free method performed better in terms of both accuracy and efficiency, indicating the model-free control could adapt to soft interaction with environment, as compared with the model-based control that does not consider contacts.



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Agile convolutional neural network for pulmonary nodule classification using CT images

Abstract

Objective

To distinguish benign from malignant pulmonary nodules using CT images is critical for their precise diagnosis and treatment. A new Agile convolutional neural network (CNN) framework is proposed to conquer the challenges of a small-scale medical image database and the small size of the nodules, and it improves the performance of pulmonary nodule classification using CT images.

Methods

A hybrid CNN of LeNet and AlexNet is constructed through combining the layer settings of LeNet and the parameter settings of AlexNet. A dataset with 743 CT image nodule samples is built up based on the 1018 CT scans of LIDC to train and evaluate the Agile CNN model. Through adjusting the parameters of the kernel size, learning rate, and other factors, the effect of these parameters on the performance of the CNN model is investigated, and an optimized setting of the CNN is obtained finally.

Results

After finely optimizing the settings of the CNN, the estimation accuracy and the area under the curve can reach 0.822 and 0.877, respectively. The accuracy of the CNN is significantly dependent on the kernel size, learning rate, training batch size, dropout, and weight initializations. The best performance is achieved when the kernel size is set to \(7\times 7\) , the learning rate is 0.005, the batch size is 32, and dropout and Gaussian initialization are used.

Conclusions

This competitive performance demonstrates that our proposed CNN framework and the optimization strategy of the CNN parameters are suitable for pulmonary nodule classification characterized by small medical datasets and small targets. The classification model might help diagnose and treat pulmonary nodules effectively.



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Landmark-based evaluation of a deformable motion correction for DCE-MRI of the liver

Abstract

Purpose

Annotation of meaningful landmark ground truth on DCE-MRI is difficult and laborious. Motion correction methods applied to DCE-MRI of the liver are thus mostly evaluated using qualitative or indirect measures. We propose a novel landmark annotation scheme that facilitates the generation of landmark ground truth on larger clinical datasets.

Methods

In our annotation scheme, landmarks are equally distributed over all time points of all available dataset cases and annotated by multiple observers on a per-pair basis. The scheme is used to annotate 26 DCE-MRI of the liver. A subset of the ground truth is used to optimize parameters of a deformable motion correction. Several variants of the motion correction are evaluated on the remaining cases with respect to distances of corresponding landmarks after registration, deformation field properties, and qualitative measures.

Results

A landmark ground truth on 26 cases could be generated in under 12 h per observer with a mean inter-observer distance below the mean voxel diagonal. Furthermore, the landmarks are spatially well distributed within the liver. Parameter optimization significantly improves the performance of the motion correction, and landmark distance after registration is 2 mm. Qualitative evaluation of the motion correction reflects the quantitative results.

Conclusions

The annotation scheme makes a landmark-based evaluation of motion corrections for hepatic DCE-MRI practically feasible for larger clinical datasets. The comparably large number of cases enables both optimization and evaluation of motion correction methods.



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The role of exposure time in computerized training of prostate cryosurgery: performance comparison of surgical residents with engineering students

Abstract

Purpose

This study aims at the evaluation of a prototype of a computerized trainer for cryosurgery—the controlled destruction of cancer tumors by freezing. The hypothesis in this study is that computer-based cryosurgery training for an optimal cryoprobe layout is essentially a matter of exposure time, rather than trainee background or the specific computer-generated planning target. Key geometric features under considerations are associated with spatial limitations on cryoprobes placement and the match between the resulted thermal field and the unique anatomy of the prostate.

Methods

All experiments in this study were performed on the cryosurgery trainer—a prototype platform for computerized cryosurgery training, which has been presented previously. Among its key features, the cryosurgery trainer displays the prostate shape and its contours and provides a distance measurement tool on demand, in order to address spatial constraints during ultrasound imaging guidance. Another unique feature of the cryosurgery trainer is an output movie, displaying the simulated thermal field at the end of the cryoprocedure.

Results

The current study was performed on graduate engineering students having no formal background in medicine, and the results were benchmarked against data obtained on surgical residents having no experience with cryosurgery. Despite fundamental differences in background and experience, neither group displayed superior performance when it comes to cryoprobe layout planning.

Conclusions

This study demonstrates that computer-based training of an optimal cryoprobe layout is feasible. This study demonstrates that the training quality is essentially related to the training exposure time, rather than to a specific planning strategy from those investigated.



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Kalman filter-based EM-optical sensor fusion for needle deflection estimation

Abstract

Purpose

In many clinical procedures such as cryoablation that involves needle insertion, accurate placement of the needle's tip at the desired target is the major issue for optimizing the treatment and minimizing damage to the neighboring anatomy. However, due to the interaction force between the needle and tissue, considerable error in intraoperative tracking of the needle tip can be observed as needle deflects.

Methods

In this paper, measurements data from an optical sensor at the needle base and a magnetic resonance (MR) gradient field-driven electromagnetic (EM) sensor placed 10 cm from the needle tip are used within a model-integrated Kalman filter-based sensor fusion scheme. Bending model-based estimations and EM-based direct estimation are used as the measurement vectors in the Kalman filter, thus establishing an online estimation approach.

Results

Static tip bending experiments show that the fusion method can reduce the mean error of the tip position estimation from 29.23 mm of the optical sensor-based approach to 3.15 mm of the fusion-based approach and from 39.96 to 6.90 mm, at the MRI isocenter and the MRI entrance, respectively.

Conclusion

This work established a novel sensor fusion scheme that incorporates model information, which enables real-time tracking of needle deflection with MRI compatibility, in a free-hand operating setup.



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Classification of uterine artery angiographic images: a predictive factor of failure in uterine artery embolization for postpartum hemorrhage

Abstract

Purpose

To justify a classification system for angiographic images of uterine artery embolization (UAE) for postpartum hemorrhage (PPH) and identify new risk factors associated with failed embolization.

Materials and methods

A retrospective analysis of 63 consecutive patients who underwent UAE for severe PPH was performed. Uterine artery angiography (UA) before embolization was classified into two types: type 1 was defined as complete staining and type 2 was defined as partial staining of the uterine arteries. The clinical outcome, UA classification, and other possible factors previously reported were evaluated. Univariate and multivariate analyses were performed to determine the factors related to clinical outcomes.

Results

Sixty-three patients were enrolled (type 1, 22; type 2, 41). The clinical success rates of the primary UAE session were 90.9% (20/22) for type 1 and 61.0% (25/41) for type 2 (p = 0.018). Univariate and multivariate analyses demonstrated that the only UA classification was significantly associated with primary UAE failure (p = 0.033).

Conclusions

The UA classification is an independent predictive factor of the clinical success rate of the primary UAE session for PPH; thus, it is an intuitive and optimal predictor for interventional radiologists to decide whether additional therapy is necessary.



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Evaluation of adaptive radiotherapy (ART) by use of replanning the tumor bed boost with repeated computed tomography (CT) simulation after whole breast irradiation (WBI) for breast cancer patients having clinically evident seroma

Abstract

Purpose

The aim of this study is to evaluate adaptive radiotherapy (ART) by use of replanning the tumor bed boost with repeated computed tomography (CT) simulation after whole breast irradiation (WBI) for breast cancer patients having clinically evident seroma.

Materials and methods

Forty-eight patients with clinically evident seroma at the time of planning CT simulation for WBI were included. Two RT treatment plannings were generated for each patient based on the initial CT simulation and tumor bed boost CT simulation to assess seroma and boost target volume (BTV) changes during WBI. Also, dosimetric impact of ART was analyzed by comparative evaluation of critical organ doses in both RT treatment plannings.

Results

Median time interval between the two CT simulations was 35 days. Statistically significant reduction was detected in seroma volume and BTV during the conventionally fractionated WBI course along with statistically significant reduction in critical organ doses with ART (p < 0.0001).

Conclusion

Our data suggest significant benefit of ART by use of replanning the tumor bed boost with repeated CT simulation after WBI for patients with clinically evident seroma.



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Automatic spectral imaging protocol selection combined with iterative reconstruction can enhance image quality and decrease radiation and contrast dosage in abdominal CT angiography

Abstract

Purpose

To investigate the effect of automatic spectral imaging protocol selection (ASIS) and adaptive statistical iterative reconstruction (ASIR) technology in reducing radiation and contrast dosage.

Methods

Sixty-four patients were randomly divided into two groups for abdominal computed tomography (CT): the experiment group with ASIS plus 50% ASIR and the control with 120 kVp voltage.

Results

The CT dose-index volume decreased by 23.68 and 23.57% and the dose-length product dropped by 25.59 and 18.45% in the arterial and portal venous phases, respectively, in the experiment than control group. The contrast dose was reduced by 16.86% in the experiment group. In the 55 keV + 50% ASIR group, the arterial contrast-to-noise ratio and scores were significantly (P < 0.05) higher than in the control group in the arterial phase while the portal contrast-to-noise ratio and scores were not significantly different between the two groups (P > 0.05).

Conclusion

The ASIS technique plus 50% ASIR can enhance image quality of the abdominal structures while decreasing the radiation and contrast dosage compared with the conventional scan mode.



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Techniques of adrenal venous sampling in patients with inferior vena cava or renal vein anomalies

Abstract

Purpose

To review the techniques and technical success rate of adrenal venous sampling (AVS) in patients with inferior vena cava (IVC) or renal vein anomalies.

Materials and methods

The techniques and success rate of AVS in 15 patients with anomalies [8 with double IVC (dIVC), 3 with left IVC (ltIVC), 2 with retroaortic left renal vein (LRV), and 2 with circumaortic LRV] underwent AVS was retrospectively reviewed.

Results

Among 11 patients with IVC anomalies, the success rates for sampling the right and left adrenal veins (RAV and LAV) were 81.8 and 90.9%, respectively. In dIVC, the LAV was selected using the following four methods: approaching through the right IVC from the right femoral vein, flipping the LAV catheter tip in the LRV (n = 4) or the interiliac-communicating vein (n = 1), or through the ltIVC from the right (n = 1) or left (n = 2) femoral vein. Among the four patients with LRV anomalies, the success rate was 100% for each adrenal vein.

Conclusion

AVS can be successfully performed in patients with anomalies. The key to technical success is understanding the venous anatomy based on pre-procedural CT images and choosing appropriate methods.



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Analysis of computed tomography density of liver before and after amiodarone administration

Abstract

Purpose

To evaluate CT density of liver changes between before and after amiodarone administration.

Materials and methods

Twenty-five patients underwent non-enhanced CT including the liver before and after amiodarone administration. We set regions of interest (ROIs) at liver S8, spleen, paraspinal muscle, and calculated average CT density in these ROIs, then compared CT density between liver and other organs. Statistical differences between CT density of liver and various ratios before and after administration were determined, along with correlations between cumulative dose of amiodarone and liver density after administration, density change of liver, and various ratios after administration.

Results

Liver density, liver-to-spleen ratio, and liver-to-paraspinal muscle ratio differed significantly between before and after amiodarone administration. No significant correlations were found between cumulative doses of amiodarone and any of liver density after administration, density change of liver, or various ratios after administration.

Conclusion

CT density of liver after amiodarone administration was significantly higher than that before administration. No correlations were identified between cumulative dose of amiodarone and either liver density after administration or density change of liver. Amiodarone usage should be checked when radiologists identify high density of the liver on CT.



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Correction to: The sternalis muscle: radiologic findings on MDCT

In the original publication of the article, the seventh author name was incorrectly published as Hidehumi Aoyama. The correct author name should read as Hidefumi Aoyama.



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Application of 3D image fusion for radiological identification of decedents

Publication date: Available online 9 April 2018
Source:Journal of Forensic Radiology and Imaging
Author(s): Dominic Gascho, Patricia M. Flach, Sarah Schaerli, Michael J. Thali, Sören Kottner

Graphical abstract

image


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Radiocaesium derived from the TEPCO Fukushima accident in the North Pacific Ocean: Surface transport processes until 2017

Publication date: September 2018
Source:Journal of Environmental Radioactivity, Volume 189
Author(s): Michio Aoyama, Yasunori Hamajima, Yayoi Inomata, Yuichiro Kumamoto, Eitarou Oka, Takaki Tsubono, Daisuke Tsumune
We report temporal variations of 137Cs activity concentrations in surface waters of six regions of the western and central North Pacific Ocean during 2011–2017 using a combination of 1264 previously published data and 42 new data. In the western and central North Pacific Ocean at latitudes of 30–42°N and longitudes of 140°E to 160°W, eastward transport of radiocaesium was clearly apparent. 137Cs activity concentrations in surface water decreased rapidly to ∼2–3 Bq m−3 in 2015/2016, still a bit higher than 137Cs activity concentrations before the FNPP1 accident (1.5–2 Bq m−3). 134Cs/137Cs activity ratios decay-corrected to 11 March 2011 were ∼0.5–0.8. To the south of 30°N and between 130°E and 160°W in the western and central Pacific Ocean, 137Cs activity concentrations were around 1–7 Bq m−3 in 2011/2012 but then stabilized at a few Bq m−3 up to 2017.134Cs activity concentrations were detected at levels of 0.1–0.9 Bq m−3, and 134Cs/137Cs activity ratios decay-corrected to 11 March 2011 were ∼0.3–0.5. Temporal variations of model-simulated 137Cs activity concentrations in surface water in the region of interest showed good agreement with observations, except in the southwestern North Pacific Ocean.



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Long-term effects of ionizing radiation after the Chernobyl accident: Possible contribution of historic dose

Publication date: August 2018
Source:Environmental Research, Volume 165
Author(s): Laila Omar-Nazir, Xiaopei Shi, Anders Moller, Timothy Mousseau, Soohyun Byun, Samuel Hancock, Colin Seymour, Carmel Mothersill
The impact of the Chernobyl NPP accident on the environment is documented to be greater than expected, with higher mutation rates than expected at the current, chronic low dose rate. In this paper we suggest that the historic acute exposure and resulting non-targeted effects (NTE) such as delayed mutations and genomic instability could account at least in part for currently measured mutation rates and provide an initial test of this concept. Data from Møller and Mousseau on the phenotypic mutation rates of Chernobyl birds 9–11 generations post the Chernobyl accident were used and the reconstructed dose response for mutations was compared with delayed reproductive death dose responses (as a measure of genomic instability) in cell cultures exposed to a similar range of doses. The dose to birds present during the Chernobyl NPP accident was reconstructed through the external pathway due to Cs-137 with an estimate of the uncertainty associated with such reconstruction. The percentage of Chernobyl birds several generations after the accident without mutations followed the general shape of the clonogenic survival percentage of the progeny of irradiated cells, and it plateaued at low doses. This is the expected result if NTE of radiation are involved. We suggest therefore, that NTE induced by the historic dose may play a role in generating mutations in progeny many generations following the initial disaster.



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[68Ga]Ga-Pentixafor PET/MRI for CXCR4 Imaging of Chronic Lymphocytic Leukemia: Preliminary Results

Objectives This prospective proof-of-principle study aimed to determine whether [68Ga]Ga-Pentixafor uptake, which reflects CXCR4 expression, is higher in the bone marrow of chronic lymphocytic leukemia (CLL) than in other oncological diseases without bone marrow infiltration and can therefore be used for CLL imaging. Materials and Methods Thirteen CLL patients and 20 controls (10 with pancreatic adenocarcinoma and 10 with mucosa-associated lymphoid tissue lymphoma) with histologically proven cancer underwent [68Ga]Ga-Pentixafor positron emission tomography/magnetic resonance imaging. Standardized [68Ga]Ga-Pentixafor uptake values (SUVmax, SUVmean) were measured in the bone marrow of the pelvis, the lumbar vertebra L4, and the bony structure with the visually highest tracer uptake ("hottest lesion"). Mean apparent diffusion coefficient values were also measured in the pelvis. Serum leukocyte count (gram per liter), lymphocyte percentage (percent), lactate dehydrogenase (unit per liter), β2-microglobulin (milligram per deciliter), and C-reactive protein (milligram per deciliter) were measured. Statistical analyses comprised analysis of variance with Games-Howell post hoc tests and Spearman correlation coefficients. Results SUVmax and SUVmean differed significantly between CLL and pancreatic adenocarcinoma in the pelvis (P = 0.032 and P = 0.008) and lumbar vertebra L4 (both P

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Diffusion-Weighted Imaging With Apparent Diffusion Coefficient Mapping for Breast Cancer Detection as a Stand-Alone Parameter: Comparison With Dynamic Contrast-Enhanced and Multiparametric Magnetic Resonance Imaging

Purpose The aims of this study were to compare dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) with apparent diffusion coefficient mapping as a stand-alone parameter without any other supportive sequence for breast cancer detection and to assess its combination as multiparametric MRI (mpMRI) of the breast. Materials and Methods In this institutional review board–approved single-center study, prospectively acquired data of 106 patients who underwent breast MRI from 12/2010 to 09/2014 for an imaging abnormality (Breast Imaging Reporting and Data System 0, 4/5) were retrospectively analyzed. Four readers independently assessed DWI and DCE as well as combined as mpMRI. Breast Imaging Reporting and Data System categories, lesion size, and mean apparent diffusion coefficient values were recorded. Histopathology was used as the gold standard. Appropriate statistical tests were used to compare diagnostic values. Results There were 69 malignant and 41 benign tumors in 106 patients. Four patients presented with bilateral lesions. Dynamic contrast-enhanced MRI was the most sensitive test for breast cancer detection, with an average sensitivity of 100%. Diffusion-weighted imaging alone was less sensitive (82%; P

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Impact of the Glymphatic System on the Kinetic and Distribution of Gadodiamide in the Rat Brain: Observations by Dynamic MRI and Effect of Circadian Rhythm on Tissue Gadolinium Concentrations

Objectives The glymphatic system is a recently hypothesized waste clearance system of the brain in which perivascular space constitutes a pathway similar to the lymphatic system in other body regions. Sleep and anesthesia are reported to influence the activity of the glymphatic system. Because rats are nocturnal animals, the glymphatic system is expected to be more active during the day. We attempted to elucidate the influence of the glymphatic system for intravenously injected gadodiamide in the rat brain by 2 experiments. One was a magnetic resonance imaging (MRI) experiment to evaluate the short-term dynamics of signal intensity changes after gadodiamide administration. The other was a quantification experiment to evaluate the concentration of retained gadolinium within the rat brain after repeated intravenous administration of gadodiamide at different times of day and levels of anesthesia. Materials and Methods The imaging experiment was performed on 6 rats that received an intravenous injection of gadodiamide (1 mmol/kg) and dynamic MRI for 3 hours at 2.4-minute intervals. The time course of the signal intensity changes was evaluated for different brain structures. The tissue quantification experiment was performed on 24 rats divided into 4 groups by injection time (morning, late afternoon) and anesthesia (none, short, long) during administration. All animals received gadodiamide (1.8 mmol/kg, 8 times over 2 weeks). Gadolinium concentration of dissected brain tissues was quantified 5 weeks after the last administration by inductively coupled plasma mass spectrometry. Results In the imaging experiment, muscle and the fourth ventricle showed an instantaneous signal intensity increase immediately after gadodiamide injection. The signal curve of the cerebral cortex and deep cerebellar nuclei reached the peak signal intensity later than the fourth ventricle but earlier than that of the prepontine cistern. In the gadolinium quantification experiment, the concentration in the group with the morning injection showed a significantly lower concentration than the late afternoon injection group. The lowest tissue gadolinium concentrations were found in the groups injected in the morning during long anesthesia. Conclusions Instantaneous transition of gadodiamide from blood to cerebrospinal fluid was indicated by dynamic MRI. The gadodiamide distribution to the cerebral cortex and deep cerebellar nuclei seemed to depend on both blood flow and cerebrospinal fluid. This confirms previous studies indicating that the cerebrospinal fluid is one potential pathway of gadolinium-based contrast agent entry into the brain. For the distribution and clearance of the gadodiamide from brain tissue, involvement of the glymphatic system seemed to be indicated in terms of the influence of sleep and anesthesia. Received for publication January 30, 2018; and accepted for publication, after revision, February 28, 2018. Conflicts of interest and sources of funding: Gregor Jost, Thomas Frenzel and Hubertus Pietsch are employees of Bayer AG. Correspondence to: Toshiaki Taoka, MD, PhD, Department of Radiology, Nagoya University Hospital, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466–8550, Japan. E-mail: ttaoka@med.nagoya-u.ac.jp. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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Acknowledgment to reviewers 2017



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Incidental findings during head and neck MRI screening in 1717 patients with temporomandibular disorders

Abstract

Objective

Magnetic resonance imaging (MRI) plays an important role in the evaluation of temporomandibular disorders (TMDs). At our institution, we perform additional head and neck screening using head coils when performing MRI screening of the temporomandibular joint (TMJ) to detect lesions in areas other than the TMJ (lesions discovered by chance, or incidental findings; IFs) and to conduct a diagnosis of exclusion. The objective of this study was to determine the number and frequency of IFs detected during head and neck screening, according to sites and diseases.

Materials and methods

The study evaluated 1717 patients with clinically suspected TMDs who underwent MRI of the TMJ. IFs were assessed on horizontal sections of images of the craniofacial region obtained by the short tau inversion recovery imaging technique.

Results

The patients undergoing MRI of the TMJ comprised 433 males and 1284 females. Among the patients, at least one IF was detected on images in 461 patients. The most common IF site was the maxillary sinus. Based on diagnostic imaging, there were 21 IFs (1.2%) associated with TMD symptoms, or for which an association with TMD symptoms could not be ruled out.

Conclusions

Combination of conventional MRI imaging of the TMJ with craniofacial MRI screening may allow detection of lesions other than TMDs, thereby confirming the usefulness of MRI. Detection of IFs may require development of different therapeutic strategies than those for TMDs.



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Morphology, incidence of bridging, and dimensions of sella turcica in different racial groups

Abstract

Objectives

This study was performed to assess the morphological appearance, incidence of bridging, and linear dimensions of the sella turcica (ST) in Bosnian and Iraqi subjects, and to identify associations of sex, age, and racial group with the size of the ST.

Methods

The digital standardised lateral cephalograms of 360 Bosnian and Iraqi patients (116 female, 64 male; age range 8–28 years) were retrospectively analysed. The following ST-related parameters were analysed on the lateral cephalograms: sella morphology, sella bridging, and sella size. The data were correlated with sex, age, and race.

Results

The ST exhibited a normal morphology in most subjects of both races (86.7%). The frequency of partial bridging was found in 38.9 and 37.2% of Bosnian and Iraqi subjects, respectively. A significant correlation was detected between the length of the ST and sex in both the Bosnian and Iraqi subjects (p < 0.05). A direct correlation was present between patient age and the size of the ST in both races at the 0.01 and 0.001 levels for depth, length, and diameter. When race was compared with sella size, a significant difference was found in the length and depth of the ST (p <  0.001).

Conclusions

Similarities were found between Bosnian and Iraqi subjects in the morphology, incidence of bridging, and linear dimensions of the ST. Length was the only parameter significantly associated with sex, age, and racial group. These findings could be used as reference standards for studying the ST in both races.



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Band- und Sehnenverletzungen an Fuß und Sprunggelenk

Zusammenfassung

Verletzungen der Bänder und Sehnen von Sprunggelenk und Fuß gehören zu den häufigsten posttraumatischen Veränderungen, mit denen ein Allgemeinradiologe konfrontiert wird. Eine korrekte und präzise Beschreibung von Pathologie und möglichen Begleitverletzungen ist für die Therapieplanung des unfallchirurgischen oder orthopädischen Behandlers essenziell. Neben der konventionellen Röntgendiagnostik zum Frakturausschluss und der Ultraschalluntersuchung kommt der Magnetresonanztomographie (MRT) zur Beurteilung der Bänder und Sehnen eine herausragende Rolle zu. Die vorliegende Arbeit gibt einen Überblick über die wesentlichen Verletzungen des Band- und Sehnenapparates von Sprunggelenk und Fuß mit ihren jeweils typischen bildmorphologischen Befunden und möglichen Begleitverletzungen. Dabei werden zunächst jeweils Anatomie und relevante Fakten zur Biomechanik erläutert. Schließlich folgt eine Beschreibung zu erwartender MRT-Befunde und möglicher Fallstricke. Im Einzelnen dargestellt werden der laterale und der mediale Bandkomplex, die Syndesmose, das sog. Pfannenband und das Lisfranc-Ligament. Daneben werden die Achillessehne und die Peronealsehnen behandelt.



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Radiologische Bildgebung der entzündlichen Erkrankungen des Gastrointestinaltrakts



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Mitteilungen des Berufsverbandes der Deutschen Radiologen



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Renal iron deposition by magnetic resonance imaging in pediatric β-thalassemia major patients: relation to renal biomarkers, total body iron and chelation therapy.

Publication date: Available online 9 April 2018
Source:European Journal of Radiology
Author(s): Mohsen Saleh ElAlfy, Nayera Hazaa El-Sherif, Fatma Soliman El-Sayed Ebeid, Eman Abdel Rahman Ismail, Khaleid Abo Elfotouh, Yasser Wagih Darwish, Ahmed S. Ibrahim, Islam Reda Farag Elghamry, Nermeen Adel Shokrey, Dunia Naser Alajeil
BackgroundThe reciprocal of multiecho gradient-echo (ME–GRE) T2* magnetic resonance imaging (MRI) R2*, rises linearly with tissue iron concentration in both heart and liver. Little is known about renal iron deposition in β-thalassemia major (β-TM).AimTo assess renal iron overload by MRI and its relation to total body iron and renal function among 50 pediatric patients with β-TM.MethodsSerum ferritin, serum cystatin C, urinary albumin creatinine ratio (UACR), and urinary β2-microglobulin (β2 M) were measured with calculation of β2 M/albumin ratio. Quantification of liver, heart and kidney iron overload was done by MRI.ResultsSerum cystatin C, UACR and urinary β2 microglobulin as well as urinary β2m/albumin were significantly higher in β-TM patients than the control group. No significant difference was found as regards renal R2* between Patients with mean serum ferritin above 2500 μg/L and those with lower serum cutoff. Renal R2* was higher in patients with poor compliance to chelation therapy and positively correlated to indirect bilirubin, LDH, cystatin C and LIC but inversely correlated to cardiac T2*.Conclusionkidney iron deposition impairs renal glomerular and tubular functions in pediatric patients with β-TM and is related to hemolysis, total body iron overload and poor compliance to chelation.



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Effects of repetitive prolonged breath-hold in elite divers on myocardial fibrosis and cerebral morphology

Publication date: June 2018
Source:European Journal of Radiology, Volume 103
Author(s): J. Doerner, L. Eichhorn, J.A. Luetkens, J.N. Lunkenheimer, J. Albers, J. Nadal, H.H. Schild, C.P. Naehle
BackgroundProlonged apnea by breath-hold (BH) divers leads to hypoxemia and compensatory mechanisms of the cardiovascular system (i.e. increase of total peripheral resistance, increase of systolic blood-pressure, left-ventricular enlargement) to maintain oxygen supply to oxygen sensitive organs such as the brain. All these changes may result in structural myocardial or subclinical brain alterations. Therefore, the aim of this study was to investigate mid-term effects of repetitive prolonged apnea using cardiac magnetic resonance imaging (CMR) and magnetic resonance imaging of the brain.Materials and methods17 elite BH divers (15 males) were investigated at baseline, from whom 9 (7 males) were investigated again at follow-up one year later. CMR included functional imaging and tissue characterization using T1- and T2-mapping as well as late gadolinium enhancement. Results were compared intra-individually and with 50 age matched controls.ResultsMean BH time were 297 ± 52 s (entire cohort) and 315 ± 56 s (sub-cohort) at initial, and 334 ± 104 s at follow-up examination. Apnea resulted in a progressive increase of the left ventricle and impaired function, whichfully resolved after cessation of apnea. At rest, no dilation of the left ventricle was notable (LV-EDV: 106.7 ± 28.8 ml; LV-EDV/BSA: 52.2 ± 12.7 ml/m2). Compared to controls, the apnea group showed significantly lower volumes (LV-EDV: 106.7 ± 28.8 ml vs. 140.9 ± 36.3 ml, p = .008; LV-EDV/BSA: 52.2 ± 12.7 ml/m2 vs. 73.7 ± 12.8 ml/m2). In contrast, LV-EF showed no significant differences between both groups (61.0 ± 7.0% vs. 60.9 ± 3.6%). T1- and T2-mapping revealed no significant differences, neither intra-individually nor in comparison with age matched controls. (T1 pre-contrast: 974.1 ± 12.9 ms vs. 969.4 ± 29.0 ms, p = .2; T1 post-contrast: 368.9 ± 38.5 ms vs. 966.7 ± 40.5 ms, p = .4; ECV: 29.2 ± 1.5% vs. 29.8 ± 1.6%, p = .3; T2. 52 ± 2 ms vs. 52 ± 3 ms; p = .4). Except for one old embolic lesion no structural changes were found in brain imaging.ConclusionAlthough, prolonged apnea leads to impressive adaptions of the cardiovascular system (i.e. dilation of the left ventricle) and hypertension due to peripheral vasoconstriction no mid-term morphological changes could be observed in both, the myocardium and the brain. BH divers are suitable as a model to investigate acute physiological changes of prolonged apnea and hypoxemia, but not as a model for chronic alterations.



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T1 mapping on gadoxetic acid-enhanced MR imaging predicts recurrence of hepatocellular carcinoma after hepatectomy

Publication date: June 2018
Source:European Journal of Radiology, Volume 103
Author(s): Wen-Tao Wang, Shuo Zhu, Ying Ding, Li Yang, Cai-Zhong Chen, Qing-Hai Ye, Yuan Ji, Meng-Su Zeng, Sheng-Xiang Rao
PurposeOur purpose was to demonstrate the prognostic significance of T1 mapping on gadoxetic acid-enhanced MR imaging in prediction of recurrence of single HCC after hepatectomy.Materials and methodsOne hundred and seven patients with single nodular HCC (≤3 cm) who underwent preoperative gadoxetic acid-enhanced MRI were included in the study. T1 mapping with syngo MapIt was obtained on a 1.5 T scanner. Radiological features and reduction rate of T1 relaxation time (Δ%) of tumors were assessed by two radiologists. Cumulative recurrence rates were compared between groups of low and high reduction rate of T1 relaxation time. A further classified cumulative recurrence rate of the overall cohort was based on the numbers of independent predictive factors.ResultsReduction rate of T1 relaxation time (P = 0.001) and non-hypervascular hypointense nodules (P = 0.042) in preoperative gadoxetic acid-enhanced MRI were independently related to recurrence of HCC after hepatectomy. Patients of lower reduction rates group had higher cumulative recurrence rates (P < 0.0001) than patients of higher reduction rates group. A combination of the two risk factors in patients with single HCC had significantly higher recurrence rates compared to those with either or none of the two risk factors.ConclusionsReduction rate of T1 relaxation time combined with non-hypervascular hypointense nodules can be reliable biomarkers in the preoperative prediction of recurrence of HCC after hepatectomy.



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Useful computed tomography features for differentiating between focal atelectasis and pleural dissemination on preoperative evaluations of thymic epithelial tumors

Publication date: June 2018
Source:European Journal of Radiology, Volume 103
Author(s): Shingo Omata, Yoshiyuki Ozawa, Motoo Nakagawa, Masaki Hara, Yuta Shibamoto
PurposeDistinguishing between focal atelectasis (FA) and pleural dissemination (PD) is important for determining the optimal therapeutic strategy for thymic epithelial tumors (TET). This study aimed to identify useful computed tomography (CT) features for distinguishing between these two conditions.Materials and methodsWe retrospectively analyzed preoperative CT images of 27 TET, which included 40 PD and 40 FA lesions. Two radiologists independently interpreted the pleural lesions without knowing the final diagnosis. The CT images were evaluated to assess the lesion location, size, and shape, presence of a spinous shadow and ground glass opacities (GGO) near to the lesion, and the shortest distance from the lesion to the nearest peripheral pulmonary artery (PA).ResultsFA lesions tended to occur on the dorsal side (90%, P = 0.024); have shorter major and minor axes (P < 0.001), a triangular shape (43%, P = 0.002), a spinous shadow (45%, P = 0.001) and GGO (28%, P = 0.006); and be close to a peripheral PA (P = 0.007). Ninety percent of PD lesions were located in the left thorax, and all of them were ipsilateral to the tumor (both P < 0.001). The 9 examined factors exhibited sensitivity, specificity, positive predictive, and negative predictive values of 85%, 95%, 94%, and 86%, respectively, for diagnosing FA (when ≥3 factors were present), and 90%, 48%, 63%, and 83%, respectively, for diagnosing PD (when ≥4 factors were present).ConclusionThe site, size, and shape of a lesion; the presence of a spinous shadow/GGO; and the distance to the nearest PA are useful for distinguishing between PD and FA.



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Nonhypervascular pancreatic neuroendocrine tumors: spectrum of MDCT imaging findings and differentiation from pancreatic ductal adenocarcinoma

Publication date: Available online 11 April 2018
Source:European Journal of Radiology
Author(s): Grigory Karmazanovsky, Elena Belousova, Wolfgang Schima, Andrei Glotov, Dmitry Kalinin, Andrei Kriger
PurposeThe purpose of our study was to determine contrast-enhanced MDCT features to differentiate nonhypervascular pancreatic neuroendocrine tumors (PNETs) from pancreatic ductal adenocarcinomas (PDACs).Methodsand materials: We included 74 patients with PNETs and 80 patients with PDACs who underwent preoperative MDCT. Two radiologists evaluated the morphologic characteristic and enhancement patterns of the tumors. Quantitative and qualitative analysis was performed, including evaluation of tumor size, homogeneity, contrast enhancement pattern, presence of pancreatic duct dilatation and tumor invasion to the adjacent vessels and peripancreatic infiltration. Tumor-to-pancreas enhancement ratio was defined as the Hounsfield units (HU) value of the tumor divided by the HU value of the pancreas. the first group was hypervascular PNETs showing hyperenhancement on arterial phase images and nonhypervascular PNETs, showing iso- or hypoenhancement on arterial phase images. After that, two radiologists estimated the possibilities of PNET or PDAC were for nonhypervascular PNETs.ResultsOn the basis of arterial enhancement, 43 PNETs were hypervascular and 31 were nonhypervascular. When compared to PDAC, nonhypervascular PNETs more frequently had well-defined tumor margins, intratumoral cystic components, calcifications and blood vessels and less frequently had main pancreatic duct dilatation, peripancreatic infiltration and vascular invasion (p < 0.01 for all). Nonhypervascular PNETs had higher tumor-to-pancreas enhancement ratio in venous phase (1.02 vs. 0.78, p = 0.012). Nonhypervascular PNETs more often had portal-venous hyperenhancement or persistent isoenhancement, while PDAC more often had persistent hypoenhancement or gradual delayed enhancement (p < 0.001). The absence of pancreatic duct dilatation and portal-venous hyperenhancement or persistent isoenhancement were the independent predictors for pancreatic adenocarcinoma.(The most accurate MDCT-findings to predict nonhypervascular PNET were the absence of pancreatic duct dilatation and peripancreatic infiltration (79% and 92% accuracy), portal-venous phase hyperenhancement or persistent isoenhancement (77%), the presence of intratumoral blood vessels (77%) and relative enhancement intensity in venous phase >0.9 (76%). Using these criteria, the area under curve for differentiation of PNET from PDAC was 0.906–0.846.ConclusionCombined assessment of the enhancement and morphologic characteristics can improve the differentiation between nonhypervascular PNETs and PDAC at contrast-enhanced MDCT.



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Prediction of histological grade of endometrial cancer by means of MRI

Publication date: June 2018
Source:European Journal of Radiology, Volume 103
Author(s): Matteo Bonatti, Beatrice Pedrinolla, Adam Jerzy Cybulski, Fabio Lombardo, Giovanni Negri, Sergio Messini, Tiziana Tagliaferri, Riccardo Manfredi, Giampietro Bonatti
ObjectivesTo evaluate the ability of MRI in predicting histological grade of endometrial cancer (EC).MethodsIRB-approved retrospective study; requirement for informed consent was waived. 90 patients with histologically proven EC who underwent preoperative MRI and surgery at our Institution between Sept2011 and Nov2016 were included. Myometrial invasion (</>50%) was assessed. Neoplasm and uterus volumes were estimated according to the ellipsoid formula; neoplasm/uterus volume ratio (N/U) was calculated. ADC maps were generated and histogram analysis was performed using commercially available software. MRI parameters were compared with the definitive histological grade (G1 = 28 patients, G2 = 29, G3 = 33) using ANOVA and Tukey-Kramer tests.ResultsDeep myometrial invasion was significantly more frequent in G2-G3 lesions than in G1 ones (p < 0,005). N/U ratio was significantly higher for high-grade neoplasms (mean 0,08 for G1, 0,16 for G2 and 0,21 in G3; P = 0,002 for G1 vs. G2-G3); a cut off value of 0,13 enabled to distinguish G1 from G2-G3 lesions with 50% sensibility and 89% specificity. ADC values didn't show any statistically significant correlation with tumour grade.ConclusionsN/U ratio >0.13 and deep myometrial invasion are significantly correlated with high grade EC, whereas ADC values are not useful for predicting EC grade.



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Diagnosis of glioma recurrence using multiparametric dynamic 18F-fluoroethyl-tyrosine PET-MRI

Publication date: June 2018
Source:European Journal of Radiology, Volume 103
Author(s): Thomas Pyka, Daniela Hiob, Christine Preibisch, Jens Gempt, Benedikt Wiestler, Jürgen Schlegel, Christoph Straube, Claus Zimmer
ObjectivesTo investigate the value of combined 18F-fluorethyltyrosine-(FET)-PET/MRI for differentiation between recurrence and treatment-related changes in glioma patients.Methods63 lesions suggestive of recurrence in 47 glioma patients were retrospectively identified. All patients had a dynamic FET scan, as well as morphologic MRI, PWI and DWI on a hybrid PET/MRI scanner. Lesions suggestive of recurrence were marked. ROC analysis was performed univariately and on parameter combination.Results50 lesions were classified as recurrence, 13 as radiation necrosis. Diagnosis was based on histology in 23 and follow-up imaging in 40 cases. Sensitivities and specificities for static PET were 80 and 85%, 66% and 77% for PWI, 62 and 77% for DWI and 64 and 79% for PET time-to-peak. AUC was 0.86 (p < 0.001) for static PET, 0.73 (p = 0.013) for PWI, 0.70 (p = 0.030) for DWI and 0.73 (p < 0.001) for dynamic PET. Multiparametric analysis resulted in an AUC of 0.89, notably yielding sensitivity of 76% vs. 56% for PET alone at 100% specificity.ConclusionSimultaneous dynamic FET-PET/MRI was reliably feasible for imaging of recurrent glioma. While all modalities were able to discriminate between recurrence and treatment-related changes, multiparametric analysis added value especially when high specificity was demanded.



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Dual-layer spectral detector CT monoenergetic reconstruction improves image quality of non-contrast cerebral CT as compared with conventional single energy CT

Publication date: Available online 13 April 2018
Source:European Journal of Radiology
Author(s): Xue-Mei Zhao, Man Wang, Run-Ze Wu, Ekta Dharaiya, Feng Feng, Ming-Li Li, Hui You, Yun Wang, Zheng-Yu Jin, Yi-Ning Wang
PurposeTo investigate and compare image quality of monoenergetic reconstructions from spectral NCCT to conventional 120kVp images acquired at a similar dose.Materials and methodsPatients undergoing NCCT on a dual-layer spectral detector CT (n = 30) and a conventional CT (n = 30) were enrolled in the study. The spectral detector CT data was reconstructed at monoenergetic images from 40–140 keV in 5-keV increments and 65–70 keV in 1-keV increments (Group A1) and using single energy CT equivalent reconstruction (Group A2). The reference conventional 120kVp images (Group B) were acquired using a standard-of-care protocol with the same radiation dose. We evaluated the image quality of monoenergetic images and determined the optimal keV level using HU attenuation, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), artifact evaluation in posterior fossa by placing region-of-interest (ROI) and subjective image score by 2 radiologists independently using a 4-point scale (1–excellent, 4–undiagnostic).ResultsThe SNR and subjective image score were optimal at 66-70keV, while monoenergetic 68 keV images with a higher SNR (18.48 ± 1.94, 15.55 ± 1.56 and 14.33 ± 1.38 for Group 68keV, A2 and B respectively, p < 0.001), CNR (4.09 ± 0.65, 3.43 ± 0.56 and 3.52 ± 0.55 for Group 68keV, A2 and B respectively, p<0.001) and a lower noise (1.80 ± 0.19, 2.11 ± 0.19 and 2.25 ± 0.25 for Group 68keV, A2 and B respectively, p<0.001).ConclusionSpectral NCCT monoenergetic reconstructions at 68 keV improve image quality and reduce artifact compared to conventional single energy CT without radiation dose penalty.



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Quantitative analysis of background parenchymal enhancement in whole breast on MRI: Influence of menstrual cycle and comparison with a qualitative analysis

Publication date: Available online 11 April 2018
Source:European Journal of Radiology
Author(s): Yongsik Jung, Seong Kyun Jeong, Doo Kyoung Kang, Yeorae Moon, Tae Hee Kim
ObjectiveWe quantitatively analyzed background parenchymal enhancement (BPE) in whole breast according to menstrual cycle and compared it with a qualitative analysis method.Materials and MethodsA data set of breast magnetic resonance imaging (MRI) from 273 breast cancer patients was used. For quantitative analysis, we used semiautomated in-house software with MATLAB. From each voxel of whole breast, the software calculated BPE using following equation: [(signal intensity [SI] at 1 min 30 sec after contrast injection – baseline SI)/baseline SI] × 100%.ResultsIn total, 53 patients had minimal, 108 mild, 87 moderate, and 25 marked BPE. On quantitative analysis, mean BPE values were 33.1% in the minimal, 42.1% in the mild, 59.1% in the moderate, and 81.9% in the marked BPE group showing significant difference (p = 0.009 for minimal vs. mild, p < 0.001 for other comparisons). Spearman's correlation test showed that there was strong significant correlation between qualitative and quantitative BPE (r = 0.63, p < 0.001).The mean BPE value was 48.7% for patients in the first week of the menstrual cycle, 43.5% in the second week, 49% in the third week, and 49.4% for those in the fourth week. The difference between the second and fourth weeks was significant (p = 0.005). Median, 90th percentile, and 10th percentile values were also significantly different between the second and fourth weeks but not different in other comparisons (first vs. second, first vs. third, first vs. fourth, second vs. third, or third vs. fourth).ConclusionQuantitative analysis of BPE correlated well with the qualitative BPE grade. Quantitative BPE values were lowest in the second week and highest in the fourth week.



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Influence of gantry rotation time and scan mode on image quality in ultra-high-resolution CT system

Publication date: Available online 4 April 2018
Source:European Journal of Radiology
Author(s): Osamu Honda, Masahiro Yanagawa, Akinori Hata, Noriko Kikuchi, Tomo Miyata, Shinsuke Tsukagoshi, Ayumi Uranishi, Noriyuki Tomiyama
ObjectivesTo investigate the image quality of helical scan (HS) mode and non-helical scan (non-HS) mode on ultra-high-resolution CT in different gantry rotation time.Methods Ultra-high resolution CT scanned eleven cadaveric lungs with the following rotation time with tube current of 200 mA and 0.25 mm collimation: HS with 1.5 s/rot (HS200 mA/1.5 s), non-HS with 1.5 s/rot (non-HS200 mA/1.5s), non-HS with 0.75s/rot (non-HS200 mA/0.75 s), non-HS with 0.35 s/rot (non-HS200 mA/0.35 s). Three observers compared each non-HS image with HS image, and scored non-HS images by using 3-point scale, paying attention to normal findings, abnormal findings, noise, streak artifact, and overall image quality. Statistical analysis was performed with Steel-Dwass test.ResultsOverall image quality (score: 2.45) and noise (score: 2.42) of non-HS 200 mA/1.5s was statistically best (p < 0.0005). Overall Image quality and noise of non-HS200 mA/0.75 s (score: 2.0) was comparable to that of HS200 mA/1.5 s. CTDIvol of HS200 mA/1.5 s is 23.2 mGy. CTDIvol of non-HS200 mA/1.5 s, non-HS200 mA/0.75 s, non-HS200 mA/0.35 s is 19.2 mGy, 9.8 mGy, 4.7 mGy.ConclusionOverall image quality and noise of non-helical scan is better than that of helical scan in the same rotation time. Overall Image quality of non-HS200 mA/0.75 s is comparable to that of HS200 mA/1.5 s, though the radiation dose of non-HS200 mA/0.75 s is lower than that of HS200 mA/1.5 s.



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Evaluation of 2-point, 3-point, and 6-point Dixon Magnetic Resonance Imaging with Flexible Echo Timing for Muscle Fat Quantification

Publication date: Available online 12 April 2018
Source:European Journal of Radiology
Author(s): Alexandra Grimm, Heiko Meyer, Marcel D. Nickel, Mathias Nittka, Esther Raithel, Oliver Chaudry, Andreas Friedberger, Michael Uder, Wolfgang Kemmler, Harald H. Quick, Klaus Engelke
The purpose of this study is to evaluate and compare 2-point (2pt), 3-point (3pt), and 6-point (6pt) Dixon magnetic resonance imaging (MRI) sequences with flexible echo times (TE) to measure proton density fat fraction (PDFF) within muscles.Two subject groups were recruited (G1: 23 young and healthy men, 31 ± 6 years; G2: 50 elderly men, sarcopenic, 77 ± 5 years). A 3-Tesla MRI system was used to perform Dixon imaging on the left thigh. PDFF was measured with six Dixon prototype sequences: 2pt, 3pt, and 6pt sequences once with optimal TEs (in- and opposed-phase echo times), lower resolution, and higher bandwidth (optTE sequences) and once with higher image resolution (highRes sequences) and shortest possible TE, respectively. Intra-fascia PDFF content was determined. To evaluate the comparability among the sequences, Bland-Altman analysis was performed. The highRes 6pt Dixon sequences served as reference as a high correlation of this sequence to magnetic resonance spectroscopy has been shown before.The PDFF difference between the highRes 6pt Dixon sequence and the optTE 6pt, both 3pt, and the optTE 2pt was low (between 2.2% and 4.4%), however, not to the highRes 2pt Dixon sequence (33%). For the optTE sequences, difference decreased with the number of echoes used.In conclusion, for Dixon sequences with more than two echoes, the fat fraction measurement was reliable with arbitrary echo times, while for 2pt Dixon sequences, it was reliable with dedicated in- and opposed-phase echo timing.



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