Πέμπτη, 5 Απριλίου 2018

Characteristic MR Imaging Findings of the Neonatal Brain in RASopathies [PEDIATRICS]

BACKGROUND AND PURPOSE:

Neuroimaging features in neonates with RASopathies are rarely reported, and to date, there are no neuroimaging studies conducted in this population. Our aim was to investigate the occurrence of supratentorial and posterior fossa abnormalities on brain MRIs of neonates with a RASopathy.

MATERIALS AND METHODS:

An observational case-control study of neonates with a confirmed RASopathy was conducted. The presence of an intraventricular and/or parenchymal hemorrhage and punctate white matter lesions and assessments of the splenium of the corpus callosum, gyrification of the cortical gray matter, and enlargement of the extracerebral space were noted. The vermis height, transverse cerebellar diameter, cranial base angle, tentorial angle, and infratentorial angle were measured.

RESULTS:

We reviewed 48 brain MR studies performed at 3 academic centers in 3 countries between 2009 and 2017. Sixteen of these infants had a genetically confirmed RASopathy (group 1), and 32 healthy infants were enrolled as the control group (group 2). An increased rate of white matter lesions, extracerebral space enlargement, simplification of the cortical gyrification, and white matter abnormalities were seen in group 1 (P < .001, for each). The vermis height of patients was significantly lower, and tentorial and infratentorial angles were significantly higher in group 1 (P = .01, P < .001, and P = .001, respectively).

CONCLUSIONS:

Neonates with a RASopathy had characteristic structural and acquired abnormalities in the cortical gray matter, white matter, corpus callosum, cerebellum, and posterior fossa. This study provides novel neuroimaging findings on supratentorial and posterior fossa abnormalities in neonates with a RASopathy.



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Cavitary Plaques in Otospongiosis: CT Findings and Clinical Implications [HEAD & NECK]

BACKGROUND AND PURPOSE:

Cavitary plaques have been reported as a manifestation of otospongiosis. They have been related to third window manifestations, complications during cochlear implantation, and sensorineural hearing loss. However, their etiology and clinical implications are not entirely understood. Our purpose was to determine the prevalence, imaging findings, and clinical implications of cavitary plaques in otospongiosis.

MATERIALS AND METHODS:

We identified patients with otospongiosis at a tertiary care academic medical center from January 2012 to April 2017. Cross-sectional CT images and clinical records of 47 patients (89 temporal bones) were evaluated for the presence, location, and imaging features of cavitary and noncavitary otospongiotic plaques, as well as clinical symptoms and complications in those who underwent cochlear implantation.

RESULTS:

Noncavitary otospongiotic plaques were present in 86 (97%) temporal bones and cavitary plaques in 30 (35%). Cavitary plaques predominated with increasing age (mean age, 59 years; P = .058), mostly involving the anteroinferior wall of the internal auditory canal (P = .003), and their presence was not associated with a higher grade of otospongiosis by imaging (P = .664) or with a specific type of hearing loss (P = .365). No patients with cavitary plaques had third window manifestations, and those with a history of cochlear implantation (n = 6) did not have complications during the procedure.

CONCLUSIONS:

Cavitary plaques occurred in one-third of patients with otospongiosis. Typically, they occurred in the anteroinferior wall of the internal auditory canal. There was no correlation with the degree of otospongiosis, type of hearing loss, or surgical complications. Cavitary plaques tended to present in older patients.



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Who's Contributing Most to American Neuroscience Journals: American or Foreign Authors? [RESEARCH PERSPECTIVES]

BACKGROUND AND PURPOSE:

With globalization, the contributions of authors from abroad to the American published literature has increased. We sought to determine the changes with time in the proportional contributions of American and non-American authors in the American neurosciences literature. We hypothesized the following: 1) During the past 21 years, manuscript contributions of American institutions have proportionally decreased in neuroradiology, more than in neurosurgery or neurology; 2) contributions of Asian institutions have affected neuroradiology more than neurosurgery and neurology; and 3) American articles garner more citations.

MATERIALS AND METHODS:

We reviewed the May issues of 2 of the highest impact American-based neurology, neurosurgery, and neuroradiology journals published from 1997 to 2017. We counted the number of articles published by nation based on the institution of origin. We looked at trends across time and compared neurology, neurosurgery, and neuroradiology journals. We also gathered data on the number of citations of each article by nationality.

RESULTS:

We reviewed 3025 articles. There was a significantly lower ratio of American to non-American authorship in neuroradiology versus neurology/neurosurgery journals (odds ratio = 0.70; 95% confidence interval, 0.60–0.82). There was a significantly decreasing trend in American authorship across the 21 years in neuroradiology. Of the countries outside the United States, Japan contributed most for neuroradiology and neurosurgery journals, and the UK, for neurology. American-authored articles were cited, on average, 1.25 times more frequently than non-American-authored articles.

CONCLUSIONS:

Non-American contributions have impacted neuroradiology more than other clinical neuroscience fields with Asian authorship showing the greatest impact. That impact is growing, and the causes are manifold. Nonetheless American-authored articles are cited more.



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Accuracy of CT Angiography for Differentiating Pseudo-Occlusion from True Occlusion or High-Grade Stenosis of the Extracranial ICA in Acute Ischemic Stroke: A Retrospective MR CLEAN Substudy [INTERVENTIONAL]

BACKGROUND AND PURPOSE:

The absence of opacification on CTA in the extracranial ICA in acute ischemic stroke may be caused by atherosclerotic occlusion, dissection, or pseudo-occlusion. The latter is explained by sluggish or stagnant flow in a patent artery caused by a distal intracranial occlusion. This study aimed to explore the accuracy of CTA for differentiating pseudo-occlusion from true occlusion of the extracranial ICA.

MATERIALS AND METHODS:

All patients from the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN) with an apparent ICA occlusion on CTA and available DSA images were included. Two independent observers classified CTA images as atherosclerotic cause (occlusion/high-grade stenosis), dissection, or suspected pseudo-occlusion. Pseudo-occlusion was suspected if CTA showed a gradual contrast decline located above the level of the carotid bulb, especially in the presence of an occluded intracranial ICA bifurcation (T-occlusion). DSA images, classified into the same 3 categories, were used as the criterion standard.

RESULTS:

In 108 of 476 patients (23%), CTA showed an apparent extracranial carotid occlusion. DSA was available in 46 of these, showing an atherosclerotic cause in 13 (28%), dissection in 16 (35%), and pseudo-occlusion in 17 (37%). The sensitivity for detecting pseudo-occlusion on CTA was 82% (95% CI, 57–96) for both observers; specificity was 76% (95% CI, 56–90) and 86% (95% CI, 68–96) for observers 1 and 2, respectively. The value for interobserver agreement was .77, indicating substantial agreement. T-occlusions were more frequent in pseudo- than true occlusions (82% versus 21%, P < .001).

CONCLUSIONS:

On CTA, extracranial ICA pseudo-occlusions can be differentiated from true carotid occlusions.



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MRI Planimetry and Magnetic Resonance Parkinsonism Index in the Differential Diagnosis of Patients with Parkinsonism [ADULT BRAIN]

BACKGROUND AND PURPOSE:

Differential diagnosis of multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration from Parkinson disease on clinical grounds is often difficult. MR imaging biomarkers could assist in a more accurate diagnosis. We examined the utility of MR imaging surface measurements (MR imaging planimetry) in the differential diagnosis of patients with parkinsonism.

MATERIALS AND METHODS:

Fifty-two patients with Parkinson-plus (progressive supranuclear palsy, n = 24; corticobasal degeneration, n = 9; multiple system atrophy, n = 19), 18 patients with Parkinson disease, and 15 healthy controls were included. Corpus callosum, midbrain, and pons surfaces; relevant indices; and the Magnetic Resonance Parkinsonism Index were calculated. Corpus callosum subsection analysis was performed, and the corpus callosum posteroanterior gradient was introduced.

RESULTS:

A Magnetic Resonance Parkinsonism Index value of >12.6 discriminated progressive supranuclear palsy from other causes of parkinsonism with a 91% sensitivity and 95% specificity. No planimetry measurement could accurately discriminate those with multiple system atrophy with parkinsonism from patients with Parkinson disease. A corpus callosum posteroanterior gradient value of ≤191 was highly specific (97%) and moderately sensitive (75%) for the diagnosis of corticobasal degeneration versus all other groups. A midbrain-to-corpus callosum posteroanterior gradient ratio of ≤0.45 was highly indicative of progressive supranuclear palsy over corticobasal degeneration (sensitivity 86%, specificity 88%).

CONCLUSIONS:

MR imaging planimetry measurements are potent imaging markers of progressive supranuclear palsy and promising markers of corticobasal degeneration but do not seem to assist in the diagnosis of multiple system atrophy with parkinsonism.



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Slow Collateral Flow Is Associated with Thrombus Extension in Patients with Acute Large-Artery Occlusion [INTERVENTIONAL]

BACKGROUND AND PURPOSE:

It is still poorly understood about the dynamic changes of the thrombus after intravenous thrombolysis and how the remaining thrombus affects clinical outcome in human stroke. Collateral flow was assumed to help to deliver endo/exogenous tissue-type plasminogen activator to the clot. We aimed to analyze the impact of collateral flow on the dynamic changes of the thrombus in patients with acute large-artery occlusion who received intravenous thrombolysis.

MATERIALS AND METHODS:

We reviewed consecutive patients with acute ischemic stroke with M1 segment or distal internal carotid artery occlusion who underwent multimodal MR imaging or CT perfusion before and 24 hours after intravenous thrombolysis without recanalization. Patients were divided into 3 groups (thrombus extension, shortening, and no change) according to thrombus-length change between baseline and 24 hours. Collateral flow was measured with arrival time delay and the collateral scoring system. Poor outcome was defined as a 3-month modified Rankin Scale score of ≥3.

RESULTS:

Among 51 patients, 18 (35.3%) had thrombus extension, 14 (27%) had thrombus shortening, and 19 (37.3%) had thrombus without change. Arrival time delay was independently associated with thrombus extension (OR = 1.499; 95% CI, 1.053–2.135; P = .025). Similarly, the collateral score on the peak artery phase was independently associated with thrombus extension (OR = 0.456; 95% CI, 0.211–0.984; P = .045), whereas baseline National Institutes of Health Stroke Scale score (OR = 0.768; 95% CI, 0.614–0.961; P = .021) and baseline thrombus length (OR = 1.193; 95% CI, 1.021–1.394; P = .026) were associated with thrombus shortening. All patients with thrombus extension had poor outcomes.

CONCLUSIONS:

Slow collateral flow was related to thrombus extension in patients with large-artery occlusion without recanalization after intravenous thrombolysis.



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Edge Contrast of the FLAIR Hyperintense Region Predicts Survival in Patients with High-Grade Gliomas following Treatment with Bevacizumab [ADULT BRAIN]

BACKGROUND AND PURPOSE:

Treatment with bevacizumab is standard of care for recurrent high-grade gliomas; however, monitoring response to treatment following bevacizumab remains a challenge. The purpose of this study was to determine whether quantifying the sharpness of the fluid-attenuated inversion recovery hyperintense border using a measure derived from texture analysis—edge contrast—improves the evaluation of response to bevacizumab in patients with high-grade gliomas.

MATERIALS AND METHODS:

MRIs were evaluated in 33 patients with high-grade gliomas before and after the initiation of bevacizumab. Volumes of interest within the FLAIR hyperintense region were segmented. Edge contrast magnitude for each VOI was extracted using gradients of the 3D FLAIR images. Cox proportional hazards models were generated to determine the relationship between edge contrast and progression-free survival/overall survival using age and the extent of surgical resection as covariates.

RESULTS:

After bevacizumab, lower edge contrast of the FLAIR hyperintense region was associated with poorer progression-free survival (P = .009) and overall survival (P = .022) among patients with high-grade gliomas. Kaplan-Meier curves revealed that edge contrast cutoff significantly stratified patients for both progression-free survival (log-rank 2 = 8.3, P = .003) and overall survival (log-rank 2 = 5.5, P = .019).

CONCLUSIONS:

Texture analysis using edge contrast of the FLAIR hyperintense region may be an important predictive indicator in patients with high-grade gliomas following treatment with bevacizumab. Specifically, low FLAIR edge contrast may partially reflect areas of early tumor infiltration. This study adds to a growing body of literature proposing that quantifying features may be important for determining outcomes in patients with high-grade gliomas.



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Clival Malformations in CHARGE Syndrome [PEDIATRICS]

BACKGROUND AND PURPOSE:

CHARGE syndrome is a multisystemic congenital disorder, most commonly including coloboma, heart malformations, choanal atresia, developmental delay, and genital and ear anomalies. The diagnostic criteria for CHARGE syndrome have been refined with time. However, limited reports describe skull base and craniocervical junction abnormalities. Recently, a coronal clival cleft has been identified in association with CHARGE syndrome. The aim of our study was to assess the prevalence of clival pathology in CHARGE syndrome.

MATERIALS AND METHODS:

In this retrospective study, the CT/MR imaging data base at a single academic children's hospital was queried for the phrase "CHARGE syndrome" during a 17-year period (2001–2017). Electronic medical records were reviewed to confirm the diagnosis. Images were assessed for skull base anomalies, specifically clival hypoplasia and dysplasia.

RESULTS:

The search yielded 42 examinations (21 CTs and 21 MRIs) from 15 distinct patients (mean age, 4.1 ± 5.6 years; range, 2 days to 19 years). CHARGE syndrome diagnosis was confirmed either by clinical and genetic testing (n = 6) or by clinical diagnosis only (n = 9). A coronal clival cleft was identified in 87% of patients (37 examinations, n = 13 patients), either partial (53%) or complete (33%). Clival hypoplasia without clefting was present in all 5 examinations from the remaining 2 patients.

CONCLUSIONS:

Clival pathology is universal in CHARGE syndrome. Coronal clival clefts are extremely common, representing a useful additional diagnostic finding. Detection of a clival cleft should alert the radiologist to examine the palate, choana, eyes, ears, and olfactory centers for other signs of CHARGE syndrome.



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Functional-guided radiotherapy using knowledge-based planning

There are two significant challenges when implementing functional-guided radiotherapy using 4DCT-ventilation imaging: (1) lack of knowledge of realistic patient specific dosimetric goals for functional lung and (2) ensuring consistent plan quality across multiple planners. Knowledge-based planning (KBP) is positioned to address both concerns.

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Frequency and Severity of Acute Allergic-Like Reactions to Intravenously Administered Gadolinium-Based Contrast Media in Children

imageObjectives The purpose of this study is to determine the frequency and severity of acute allergic-like reactions to gadolinium-based contrast media (GBCM) in children before, during, and after the transition from gadopentetate dimeglumine to gadoterate meglumine as our primary clinical GBCM. Materials and Methods Institutional review board approval was obtained for this Health Insurance Portability and Accountability Act–compliant retrospective investigation. Allergic-like reactions to GBCM in pediatric patients were retrospectively assessed from January 2009 to January 2017, which included a departmental change of GBCM from gadopentetate dimeglumine to gadoterate meglumine. Allergic-like reactions were identified from departmental and hospital databases. The number of doses of GBCM was obtained from billing data. Allergic-like reaction frequencies for each GBCM were calculated and compared using the chi-squared test. Results A total of 32,365 administrations of GBCM occurred during the study period (327 for gadofosveset trisodium; 672 for gadoxetate disodium; 12,012 for gadoterate meglumine; and 19,354 for gadopentetate dimeglumine). Allergic-like reactions occurred after 21 (0.06%) administrations. Reaction frequencies were not significantly different among the GBCM (0.3% gadofosveset trisodium; 0% gadoxetate disodium, 0.06% gadoterate meglumine, 0.08% gadopentetate dimeglumine; P > 0.05). Ten (47.6%) reactions were mild, 10 (47.6%) were moderate, and 1 (4.8%) was severe. The overall reaction frequency peaked during the 6-month transition period from gadopentetate dimeglumine to gadoterate meglumine (0.20%), compared with 0.07% pretransition (P = 0.048) and 0.04% posttransition (P = 0.0095). Conclusion Allergic-like reactions to GBCM in children are rare. Gadoterate meglumine has a reaction frequency that does not significantly differ from other GBCMs. During the transition from gadopentetate dimeglumine to gadoterate meglumine, an increase in the frequency of reported allergic-like reactions was observed, likely reflective of the Weber effect.

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Impact of Contrast Media Concentration on Low-Kilovolt Computed Tomography Angiography: A Systematic Preclinical Approach

imageObjectives Low peak kilovoltage (kVp) protocols in computed tomography angiography (CTA) demand a review of contrast media (CM) administration practices. The aim of this study was to systematically evaluate different iodine concentrations of CM in a porcine model. Materials and Methods Dynamic 70 kVp CTA was performed on 7 pigs using a third-generation dual-source CT system. Three CM injection protocols (A-C) with an identical total iodine dose and iodine delivery rate (150 mg I/kg, 12 s, 0.75 g I/s) differed in iodine concentration and flow rate (protocol A: 400 mg I/mL, 1.9 mL/s; B: 300 mg I/mL, 2.5 mL/s; C: 150 mg I/mL, 5 mL/s). All protocols were applied in a randomized order and compared intraindividually. Arterial enhancement at different locations in the pulmonary artery, the aorta, and aortic branches was measured over time. Time attenuation curves, peak enhancement, time to peak, and bolus tracking delay times needed for static CTA were calculated. The reproducibility of optimal parameters was tested in single-phase CTA. Results The heart rates of the pigs were comparable for all protocols (P > 0.7). The injection pressure was significantly higher for protocol A (64 ± 5 psi) and protocol C (55 ± 3 psi) compared with protocol B (39 ± 2 psi) (P

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CAPTURE: Consistently Acquired Projections for Tuned and Robust EstimationA Self-Navigated Respiratory Motion Correction Approach

imageObjectives In this study, we present a fully automated and robust self-navigated approach to obtain 4-dimensional (4-D) motion-resolved images during free breathing. Materials and Methods The proposed method, Consistently Acquired Projections for Tuned and Robust Estimation (CAPTURE), is a variant of the stack-of-stars gradient-echo sequence. A 1-D navigator was consistently acquired at a fixed azimuthal angle for all stacks of spokes to reduce nonphysiological signal contamination due to system imperfections. The resulting projections were then "tuned" using complex phase rotation to adapt to scan-to-scan variations, followed by the detection of the respiratory curve. Four-dimensional motion-corrected and uncorrected images were then reconstructed via respiratory and temporal binning, respectively. This Health Insurance Portability and Accountability Act–compliant study was performed with Institutional Review Board approval. A phantom experiment was performed using a custom-made deformable motion phantom with an adjustable frequency and amplitude. For in vivo experiments, 10 healthy participants and 12 liver tumor patients provided informed consent and were imaged with the CAPTURE sequence. Two radiologists, blinded to which images were motion-corrected and which were not, independently reviewed the images and scored the image quality using a 5-point Likert scale. Results In the respiratory motion phantom experiment, CAPTURE reversed the effects of motion blurring and restored edge sharpness from 36% to 78% of that observed in the images from the static scan. Despite large intra- and intersubject variability in respiration patterns, CAPTURE successfully detected the respiratory motion signal in all participants and significantly improved the image quality according to the subjective radiological assessments of 2 raters (P

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T2 Mapping for Noninvasive Assessment of Interstitial Edema in Acute Cardiac Allograft Rejection in a Mouse Model of Heterotopic Heart Transplantation

imageObjectives Heart transplantation (HTX) in mice is used to characterize gene-deficient mice and to test new treatment strategies. The purpose was to establish noninvasive magnetic resonance imaging techniques in mice to monitor pathophysiological changes of the allograft during rejection. Materials and Methods Magnetic resonance imaging was performed at baseline and days 1 and 6 after isogenic (n = 10, C57BL/6) and allogenic (n = 12, C57BL/6 to BALB/c) heterotopic HTX on a 7 T small animal scanner. Respiratory- and electrocardiogram-gated multislice multi-echo spin echo sequences were acquired, and parameter maps of T2 relaxation time were generated. T2 times in septal, anterior, lateral, and posterior myocardial segments as well as global T2 times were calculated and compared between groups. At day 7 animals were sacrificed and graft pathology was assessed by semiquantitative regional analysis and correlated with magnetic resonance imaging results. Results Myocardial T2 relaxation time was significantly increased in allogenic (33.4 ± 0.1 ms) and isogenic cardiac grafts (31.8 ± 1.8 ms) on day 1 after HTX compared with healthy donor hearts at baseline (23.1 ± 0.3 ms, P

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Relaxivity of Ferumoxytol at 1.5 T and 3.0 T

imageObjectives The aim of this study was to determine the relaxation properties of ferumoxytol, an off-label alternative to gadolinium-based contrast agents, under physiological conditions at 1.5 T and 3.0 T. Materials and Methods Ferumoxytol was diluted in gradually increasing concentrations (0.26–4.2 mM) in saline, human plasma, and human whole blood. Magnetic resonance relaxometry was performed at 37°C at 1.5 T and 3.0 T. Longitudinal and transverse relaxation rate constants (R1, R2, R2*) were measured as a function of ferumoxytol concentration, and relaxivities (r1, r2, r2*) were calculated. Results A linear dependence of R1, R2, and R2* on ferumoxytol concentration was found in saline and plasma with lower R1 values at 3.0 T and similar R2 and R2* values at 1.5 T and 3.0 T (1.5 T: r1saline = 19.9 ± 2.3 s−1mM−1; r1plasma = 19.0 ± 1.7 s−1mM−1; r2saline = 60.8 ± 3.8 s−1mM−1; r2plasma = 64.9 ± 1.8 s−1mM−1; r2*saline = 60.4 ± 4.7 s−1mM−1; r2*plasma = 64.4 ± 2.5 s−1mM−1; 3.0 T: r1saline = 10.0 ± 0.3 s−1mM−1; r1plasma = 9.5 ± 0.2 s−1mM−1; r2saline = 62.3 ± 3.7 s−1mM−1; r2plasma = 65.2 ± 1.8 s−1mM−1; r2*saline = 57.0 ± 4.7 s−1mM−1; r2*plasma = 55.7 ± 4.4 s−1mM−1). The dependence of relaxation rates on concentration in blood was nonlinear. Formulas from second-order polynomial fittings of the relaxation rates were calculated to characterize the relationship between R1blood and R2 blood with ferumoxytol. Conclusions Ferumoxytol demonstrates strong longitudinal and transverse relaxivities. Awareness of the nonlinear relaxation behavior of ferumoxytol in blood is important for ferumoxytol-enhanced magnetic resonance imaging applications and for protocol optimization.

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Gadolinium Accumulation in the Deep Cerebellar Nuclei and Globus Pallidus After Exposure to Linear but Not Macrocyclic Gadolinium-Based Contrast Agents in a Retrospective Pig Study With High Similarity to Clinical Conditions

imageObjective The aim of this retrospective study was to determine the gadolinium (Gd) concentration in different brain areas in a pig cohort that received repeated administration of Gd-based contrast agents (GBCAs) at standard doses over several years, comparable with a clinical setting. Material and Methods Brain tissue was collected from 13 Göttingen mini pigs that had received repeated intravenous injections of gadopentetate dimeglumine (Gd-DTPA; Magnevist) and/or gadobutrol (Gadovist). The animals have been included in several preclinical imaging studies since 2008 and received cumulative Gd doses ranging from 7 to 129 mmol per animal over an extended period. Two animals with no history of administration of GBCA were included as controls. Brain autopsies were performed not earlier than 8 and not later than 38 months after the last GBCA application. Tissues from multiple brain areas including cerebellar and cerebral deep nuclei, cerebellar and cerebral cortex, and pons were analyzed for Gd using inductively coupled plasma mass spectrometry. Results Of the 13 animals, 8 received up to 48 injections of gadobutrol and Gd-DTPA and 5 received up to 29 injections of gadobutrol only. In animals that had received both Gd-DTPA and gadobutrol, a median (interquartile range) Gd concentration of 1.0 nmol/g tissue (0.44-1.42) was measured in the cerebellar nuclei and 0.53 nmol/g (0.29-0.62) in the globus pallidus. The Gd concentration in these areas in gadobutrol-only animals was 50-fold lower with median concentrations of 0.02 nmol/g (0.01-0.02) for cerebellar nuclei and 0.01 nmol/g (0.01-0.01) for globus pallidus and was comparable with control animals with no GBCA history. Accordingly, in animals that received both GBCAs, the amount of residual Gd correlated with the administered dose of Gd-DTPA (P ≤ 0.002) but not with the total Gd dose, consisting of Gd-DTPA and gadobutrol. The Gd concentration in cortical tissue and in the pons was very low (≤0.07 nmol/g tissue) in all animals analyzed. Conclusion Multiple exposure to macrocyclic gadobutrol is not associated with Gd deposition in brain tissue of healthy pigs. A single additional administration of linear Gd-DTPA is sufficient for Gd accumulation in the nucleus dentatus and globus pallidus, underlining the importance of obtaining a complete GBCA history in clinical studies.

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Optimizing Pulmonary Embolism Computed Tomography in the Age of Individualized Medicine: A Prospective Clinical Study

imagePurpose The aim of the study was to simultaneously optimize contrast media (CM) injection and scan parameters for the individual patient during computed tomography pulmonary angiography (CTPA). Methods In this study (NCT02611115), 235 consecutive patients suspected of having pulmonary embolism were prospectively enrolled. Automated kV selection software on a third-generation multidetector computed tomography adapted tube voltage to the individual patient, based on scout scans. The contrast injection protocol was adapted to both patient body weight and kV-setting selection via a predefined formula, based on previous research. Injection data were collected from a contrast media and radiation dose monitoring software. Attenuation was measured in Hounsfield units (HU) in the pulmonary trunk (PT); attenuation values 200 HU or greater were considered diagnostic. Subjective image quality was assessed by using a 4-point Likert scale at the level of the PT, lobar, segmental, and subsegmental arteries. Results between groups were reported as mean ± SD. Results Two hundred twenty-two patients (94%) were scanned at a kV setting below 100 kV: n = 108 for 70 kV, n = 82 for 80 kV, and n = 32 for 90 kV. Mean CM bolus volume (in milliliters) and total iodine load (in grams of iodine) for 70 to 90 kV were as follows: 24 ± 3 mL and 7 ± 1 g I, 29 ± 4 mL and 9 ± 2 g I, and 38 ± 4 mL and 11 ± 1 g I, respectively. Mean flow rates (in milliliters per second) and iodine delivery rates (in grams of iodine per second) were 3.0 ± 0.4 mL/s and 0.9 ± 0.1 g I/s (70 kV), 3.6 ± 0.4 mL/s and 1.0 ± 0.1 g I/s (80 kV), and 4.7 ± 0.5 mL/s and 1.3 ± 0.1 g I/s (90 kV). Mean radiation doses were 1.3 ± 0.3 mSv at 70 kV, 1.7 ± 0.4 mSv at 80 kV, and 2.2 ± 0.6 mSv at 90 kV. Mean vascular attenuation in the PT for each kV group was as follows: 397 ± 101 HU for 70 kV, 398 ± 96 HU for 80 kV, and 378 ± 100 HU for 90 kV, P = 0.59. Forty-six patients (21%) showed pulmonary embolism on the CTPA. One scan (90 kV) showed nondiagnostic segmental pulmonary arteries, and 5% of subsegmental arteries were of nondiagnostic image quality. All other segments were considered diagnostic-excellent subjective image quality. Conclusions Simultaneously optimizing both CM injections and kV settings to the individual patient in CTPA results in diagnostic attenuation with on average 24 to 38 mL of CM volume and a low radiation dose for most patients. This individualized protocol may help overcome attenuation-variation problems between patients and kV settings in CTPA.

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Treatment Effect of Balloon Pulmonary Angioplasty in Chronic Thromboembolic Pulmonary Hypertension Quantified by Automatic Comparative Imaging in Computed Tomography Pulmonary Angiography

imageObjectives Balloon pulmonary angioplasty (BPA) in patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH) can have variable outcomes. To gain more insight into this variation, we designed a method for visualizing and quantifying changes in pulmonary perfusion by automatically comparing computed tomography (CT) pulmonary angiography before and after BPA treatment. We validated these quantifications of perfusion changes against hemodynamic changes measured with right-sided heart catheterization. Materials and Methods We studied 14 consecutive CTEPH patients (12 women; age, 70.5 ± 24), who underwent CT pulmonary angiography and right-sided heart catheterization, before and after BPA. Posttreatment images were registered to pretreatment CT scans (using the Elastix toolbox) to obtain corresponding locations. Pulmonary vascular trees and their centerlines were detected using a graph cuts method and a distance transform method, respectively. Areas distal from vessels were defined as pulmonary parenchyma. Subsequently, the density changes within the vascular centerlines and parenchymal areas were calculated and corrected for inspiration level differences. For visualization, the densitometric changes were displayed in color-coded overlays. For quantification, the median and interquartile range of the density changes in the vascular and parenchymal areas (ΔVD and ΔPD) were calculated. The recorded changes in hemodynamic parameters, including changes in systolic, diastolic, and mean pulmonary artery pressure (ΔsPAP, ΔdPAP, and ΔmPAP, respectively) and vascular resistance (ΔPVR), were used as reference assessments of the treatment effect. Spearman correlation coefficients were employed to investigate the correlations between changes in perfusion and hemodynamic changes. Results Comparative imaging maps showed distinct patterns in perfusion changes among patients. Within pulmonary vessels, the interquartile range of ΔVD correlated significantly with ΔsPAP (R = −0.58, P = 0.03), ΔdPAP (R = −0.71, P = 0.005), ΔmPAP (R = −0.71, P = 0.005), and ΔPVR (R = −0.77, P = 0.001). In the parenchyma, the median of ΔPD had significant correlations with ΔdPAP (R = −0.58, P = 0.030) and ΔmPAP (R = −0.59, P = 0.025). Conclusions Comparative imaging analysis in CTEPH patients offers insight into differences in BPA treatment effect. Quantification of perfusion changes provides noninvasive measures that reflect hemodynamic changes.

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In Vivo Abdominal Magnetic Resonance Elastography for the Assessment of Portal Hypertension Before and After Transjugular Intrahepatic Portosystemic Shunt Implantation: Erratum

No abstract available

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On the relation between outdoor 222Rn and atmospheric stability determined by a modified Turner method

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Publication date: September 2018
Source:Journal of Environmental Radioactivity, Volume 189
Author(s): Martin Bulko, Karol Holý, Monika Müllerová
In practice, information about atmospheric stability is often obtained from discrete stability classes determined from routine meteorological observations. However, changing concentrations of the radioactive gas 222Rn present in the atmosphere are also considered a good indicator of vertical dispersion and atmospheric stability. A complex, in-depth analysis between these different approaches of atmospheric stability assessment has not been performed so far, and was the main motivation behind this study. The study presents atmospheric radon data measured in Bratislava (Slovakia) and stability indexes (SI) calculated according to a modified Turner method during a period of one year. Basic features of the diurnal and seasonal variations of these variables are discussed. It was found that the time series of radon activity concentration (RAC) lags approximately 5 h behind that of the Turner stability classes adjusted for temperate climate regions. Various time lags were also identified between RAC and meteorological variables used to determine the stability classes. Evaluation of seasonal trends revealed a low variability of mean monthly values of stability classes compared to the variability of mean monthly values of RAC. Another notable difference between RAC and stability indexes was found – while the stability index can both increase and decrease with wind speed, concentration of outdoor radon was never observed to increase with increasing wind speed. In spite of the mentioned discrepancies, the time series of RAC and SI are generally in a good agreement. This is especially true if one compares the deviations of RAC and SI from their mean daily values, when the differences in their seasonal variability are eliminated. Deviations of RAC can be used to calculate diurnal variations of stability indexes. Analysis of a complete year of data also revealed a roughly linear relationship between average values of RAC and calculated stability indexes, because in large datasets random processes tend to cancel each other out.



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