Interstudy reproducibility of dark blood high-resolution MRI in evaluating basilar atherosclerotic plaque at 3 Tesla

PURPOSE:We aimed to evaluate the interscan, intraobserver, and interobserver reproducibility of basilar atherosclerotic plaque employing dark blood high-resolution magnetic resonance imaging (HR-MRI) at 3 Tesla.METHODS:Sixteen patients (14 males and 2 females) with >30% basilar stenosis as identified by conventional magnetic resonance angiography were prospectively recruited for scan and rescan examinations on a 3 Tesla MRI system using T2-weighted turbo spin-echo protocol. Two observers independently measured the areas of vessels and lumens. Wall area was derived by subtracting the lumen area from the vessel area. Areas of vessels, lumens and walls were compared for the evaluation of interscan variability of basilar plaque. To assess the intraobserver variability, one observer reevaluated all the images of the first scan after a 4-week interval.RESULTS:Fourteen patients were included in the final analysis. No clinically significant difference was observed for interscan, intraobserver, and interobserver measurements. The intraclass correlations for vessel, lumen, and wall areas were excellent and ranged from 0.973 to 0.981 for the interscan measurements, 0.997 to 0.998 for the intraobserver measurements and 0.979 to 0.985 for the interobserver measurements. The coefficients of variation for quantitative basilar morphology measurements were 4.31%–10.35% for the interscan measurements, 1.41%–4.62% for the intraobserver measurements and 3.79%–8.46% for the interobserver measurements. Compared with the interscan and interobserver measurements, narrow intervals of the scatterplots were observed for the intraobserver measurements by Bland-Altman plots.CONCLUSION:Basilar atherosclerotic plaque imaging demonstrates excellent reproducibility at 3 Tesla. The study proves that dark blood HR-MRI may serve as a reliable tool for clinical studies focused on the progression and treatment response of basilar atherosclerosis

An assessment on the incremental value of high-resolution magnetic resonance imaging to identify culprit plaques in atherosclerotic disease of the middle cerebral artery.

OBJECTIVE: Although certain morphological features depicted by high resolution, multi-contrast magnetic resonance imaging (hrMRI) have been shown to be different between culprit and non-culprit middle cerebral artery (MCA) atherosclerotic lesions, the incremental value of hrMRI to define culprit lesions over stenosis has not been assessed. METHODS: Patients suspected with MCA stenosis underwent hrMRI. Lumen and outer wall were segmented to calculate stenosis, plaque burden (PB), volume (PV), length (PL) and minimum luminal area (MLA). RESULTS: Data from 165 lesions (112 culprit and 53 non-culprit) in 139 individuals were included. Culprit lesions were larger and longer with a narrower lumen and increased PB compared with non-culprit lesions. More culprit lesions showed contrast enhancement. Both PB and MLA were better indicators than stenosis in differentiating lesion types (AUC were 0.649, 0.732 and 0.737 for stenosis, PB and MLA, respectively). Combinations of PB, MLA and stenosis could improve positive predictive value (PPV) and specificity significantly. An optimal combination of stenosis ≥ 50 %, PB ≥ 77 % and MLA ≤ 2.0 mm(2) produced a PPV = 85.7 %, negative predictive value = 54.1 %, sensitivity = 69.6 %, specificity = 75.5 %, and accuracy = 71.5 %. CONCLUSIONS: hrMRI plaque imaging provides incremental information to luminal stenosis in identifying culprit lesions. KEY POINTS: • High resolution MRI provides incremental information in defining culprit MCA atherosclerotic lesions. • Both plaque burden and minimum luminal area are better indicators than stenosis. • An optimal combination includes stenosis ≥ 50 %, PB ≥ 77 % and MLA ≤ 2.0 mm (2) .This research is supported by Shanghai Shenkang Porject SHDC12013110, Shanghai, China; British Heart Foundation (BHF) PG/11/74/29100; and the NIHR Cambridge Biomedical Research Centre, Cambridge, UK. Dr Peng is supported by China Scholarship Council (201306580006), Beijing, China.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00330-015-4008-

EXPERIMENTAL STUDY OF THE STABILITY OF NbTi COMPOSITE CONDUCTOR UNDER THE INFLUENCE OF PULSED MAGNETIC FIELD

Nous avons construit un appareillage expérimental destiné à étudier l'influence d'un champ magnétique pulsé sur la stabilité d'un conducteur multifilamentaire composite, torsadé, de NbTi. Plusieurs échantillons ont été mesurés. Nous présentons nos résultats.To study the influence of pulsed magnetic field on the stability of NbTi multifilamentary twisted composite conductor, an experimental device was constructed and several samples have been studied. The corresponding results are presented

IMPROVEMENT ON THE SUPPORT STRUCTURE OF THE SUPERCONDUCTING SADDLE MAGNET SSM-3

Le travail pour l'amélioration de la structure supportante de l'aimant SSM-3 ("adiabatically stable, saddle magnet") est résumé. Cet aimant atteint la performance en échantillon court.The work related to support structure improvement, which allows the adiabatically stable saddle magnet SSM-3 to achieve "short-sample" performance, has been summarized

Atherosclerosis Burden of Brain‐ and Heart‐Supplying Arteries and the Relationship With Vascular Risk in Patients With Ischemic Stroke

Background Atherosclerosis of brain‐ and heart‐supplying arteries (BHAs) are risk indicators for patients with ischemic stroke, but the atherosclerosis burden (AB) of intracranial, cervical, aortic, and coronary arteries in each and in total have not been simultaneously evaluated, and the associations with vascular risk remain unknown. Methods and Results With computed tomography angiography, single‐territory AB was triple ranked on the basis of the number of arterial segments with a significant atherosclerotic lesion. The total AB (TAB) of BHAs was triple ranked on the basis of the number of arterial territories with a significant atherosclerotic lesion, or according to the sum of 4 single‐territory AB rank‐scores. After a 12‐month follow‐up of 395 patients with ischemic stroke, a composite outcome of ischemic stroke, myocardial infarction, and vascular death occurred in 10.9%. The single‐territory AB of intracranial, cervical, aortic, and coronary arteries showed distinct strata patterns and different associations with vascular risk. The score‐based TAB of BHAs predicted vascular risk (crude hazard ratios [95% CIs]: per level increase, 2.35 [1.54–3.58]; median versus low, 3.37 [1.45–7.82]; high versus low, 6.00 [2.36–15.24]) independently of vascular risk factors and single‐territory AB, providing more prognostic information than the TAB of BHAs measured by the number of significantly atherosclerotic territories. Vascular events occurred in 3.0%, 13.6%, and 22.6% of patients in the low (41.8%), median (44.8%), and high (13.4%) strata of the score‐based TAB of BHAs, respectively. Conclusions The single‐territory AB of intracranial, cervical, aortic, or coronary arteries might be not reliable for vascular risk stratification in patients with ischemic stroke, and evaluating the TAB of BHAs by quantitatively integrating the single‐territory AB is advisable

Quench protection design of a 1.5 T superconducting MRI magnet

A 1.5 T superconducting MRI magnet has been developed in our laboratory. A passive quench protection system is employed to avoid the damage through the quench event. The coils are subdivided into several groups and a heater network is implemented accordingly. With the control volume method, the numerical model of the quench time is introduced. Different design schemes of the heater strip are compared. The simulation results of currents and voltages are illustrated and the temperature rise of the coils and the heaters are discussed

Diffusion-weighted imaging of rectal cancer on repeatability and cancer characterization: an effect of b-value distribution study

Abstract Background To explore the effect of b-value distributions on the repeatability and diagnostic performance of the ADC value in rectal cancer patients using multiple b-values and mono-exponential model diffusion-weighted imaging (DWI). Methods Thirty-two preoperative rectal cancer patients, without receiving neoadjuvant therapy, were scanned on a 3 Tesla magnetic resonance imaging scanner using DWI with 10 b-values ranging from 0 to 2000 s/mm2. The apparent diffusion coefficient (ADC) value was calculated using a mono-exponential model and 31 b-value combinations consisting of 2 to 10 b-values were explored. Regions of interest with the maximum cross-sectional tumour size were outlined on the ADC map by two independent observers. Intraclass correlation coefficients (ICC), coefficient of variation (CV), and Bland-Altman plots between the two observers were calculated and evaluated to determine repeatability. Areas under receiver operating characteristic curves (AUCs) were evaluated for rectal cancer characterization. Correlations between the mean ADC values and T stage were assessed using the Spearman correlation coefficient (ρ). α (= ICC + AUC + |ρ|- CV - |bias|) was defined and used to assess the optimal b-value distribution. Results Postoperative pathology tests revealed 4 patients with T1, 10 patients with T2, and 18 patients with T3 stages. There were no significant difference in age and sex between the two groups (T1–2 vs. T3). Excellent reproducibility was observed for ADC values between two observers with ICC and CV values ranging from 0.920 to 0.998, and 1.475 to 5.568%, respectively. The mean percent difference and ρ between the paired measurements was ranged from − 2.7 to 1.2% and from − 0.759 to − 0.407, respectively. The b-value combinations with the top three α values were b(0, 1000 s/mm2), b(500, 1500, 2000 s/mm2) and b(100, 1000, 1500 s/mm2) for α = 2.581, 2.571 and 2.569, respectively. Conclusions The number of b-values and their distributions influenced the repeatability of the ADC values and their diagnostic performance. The optimal b-value combination was 0 and 1000 s/mm2 for DWI examination of rectal cancer patients

Comparison of two different measurement methods in evaluating basilar atherosclerotic plaque using high-resolution MRI at 3 tesla

Abstract Background To compare the Self-referenced and Referenced measurement methods in assessing basilar artery (BA) atherosclerotic plaque employing dark blood high-resolution MRI at 3 Tesla. Methods Forty patients with > 20% stenosis as identified by conventional MRA were recruited and evaluated on a 3 Tesla MRI system. The outer wall, inner wall and lumen areas of maximal lumen narrowing site and the outer wall and lumen areas of sites that were proximal and distal to the maximal lumen narrowing site were manually traced. Plaque area (PA), stenosis rate (SR) and percent plaque burden (PPB) were calculated using the Self-referenced and Referenced measurement methods, respectively. To assess intra-observer reproducibility, BA plaque was measured twice with a 2-week interval in between measurements. Results Thirty-seven patients were included in the final analysis. There were no significant differences in PA, SR and PPB measurements between the two methods. The intra-class coefficients and coefficient of variations (CV) ranged from 0.976 to 0.990 and from 3.73 to 5.61% for the Self-referenced method and ranged from 0.928 to 0.971 and from 4.64 to 9.95% for the Referenced method, respectively. Both methods are effective in the evaluation of BA plaque. However, the CVs of the Self-referenced method is lower than the Referenced measurement method. Moreover, Bland-Altman plots showed that the Self-referenced method has a narrower interval than the Referenced measurement method. Conclusions The Self-referenced method is better and more convenient for evaluating BA plaque, and it may serve as a promising method for evaluation of basilar atherosclerotic plaque