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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