The Use of Noncontrast Quantitative MRI to Detect Gadolinium-Enhancing Multiple Sclerosis Brain Lesions: A Systematic Review and Meta-Analysis.

BACKGROUND: Concerns have arisen about the long-term health effects of repeat gadolinium injections in patients with multiple sclerosis and the incomplete characterization of MS lesion pathophysiology that results from relying on enhancement characteristics alone. PURPOSE: Our aim was to perform a systematic review and meta-analysis analyzing whether noncontrast MR imaging biomarkers can distinguish enhancing and nonenhancing brain MS lesions. DATA SOURCES: Our sources were Ovid MEDLINE, Ovid Embase, and the Cochrane data base from inception to August 2016. STUDY SELECTION: We included 37 journal articles on 985 patients with MS who had MR imaging in which T1-weighted postcontrast sequences were compared with noncontrast sequences obtained during the same MR imaging examination by using ROI analysis of individual MS lesions. DATA ANALYSIS: We performed random-effects meta-analyses comparing the standard mean difference of each MR imaging metric taken from enhancing-versus-nonenhancing lesions. DATA SYNTHESIS: DTI-based fractional anisotropy values are significantly different between enhancing and nonenhancing lesions (P = .02), with enhancing lesions showing decreased fractional anisotropy compared with nonenhancing lesions. Of the other most frequently studied MR imaging biomarkers (mean diffusivity, magnetization transfer ratio, or ADC), none were significantly different (P values of 0.30, 0.47, and 0.19. respectively) between enhancing and nonenhancing lesions. Of the limited studies providing diagnostic accuracy measures, gradient-echo-based quantitative susceptibility mapping had the best performance in discriminating enhancing and nonenhancing MS lesions. LIMITATIONS: MR imaging techniques and patient characteristics were variable across studies. Most studies did not provide diagnostic accuracy measures. All imaging metrics were not studied in all 37 studies. CONCLUSIONS: Noncontrast MR imaging techniques, such as DTI-based FA, can assess MS lesion acuity without gadolinium.

Quantifying Intracranial Internal Carotid Artery Stenosis on MR Angiography.

BACKGROUND AND PURPOSE: Intracranial atherosclerosis is a common cause of ischemic stroke. Intracranial stenosis is most commonly quantified by the Warfarin-Aspirin Symptomatic Intracranial Disease method, which involves calculating a ratio of luminal diameter measurements on conventional angiography. Our purpose was to determine whether a single linear measurement of the narrowest caliber of the intracranial ICA on MRA can accurately predict Warfarin-Aspirin Symptomatic Intracranial Disease stenosis measurements. MATERIALS AND METHODS: We identified patients from a prospective stroke registry who had undergone head MRAs to quantitatively evaluate the degree of Warfarin-Aspirin Symptomatic Intracranial Disease-derived stenosis in each intracranial ICA. We also made a single linear millimeter measurement at the site of maximal narrowing of the ICA. We calculated a correlation coefficient between the lumen diameter in millimeters and percentage Warfarin-Aspirin Symptomatic Intracranial Disease stenosis. We performed receiver operating characteristic analysis to determine optimal luminal diameter cutoff values. RESULTS: In 386 unique intracranial ICAs, we found a strong linear relationship between single lumen measurements and Warfarin-Aspirin Symptomatic Intracranial Disease-style stenosis measurements (R = -0.84, P < .0001). We found that ICA lumen diameters of ≤2.1 and ≤1.3 mm were optimal cutoffs for identifying patients with ≥50% stenosis and ≥70% stenosis, respectively (area under the curve = 0.96 and 0.99, respectively). CONCLUSIONS: There is a strong linear relationship between the narrowest lumen diameter of the intracranial ICA and percentage stenosis. Our results suggest that a single lumen diameter measurement on MRA allows accurate estimation of Warfarin-Aspirin Symptomatic Intracranial Disease stenosis, which may affect risk stratification and treatment decisions.

Association between Carotid Plaque Features on CTA and Cerebrovascular Ischemia: A Systematic Review and Meta-Analysis.

BACKGROUND: CTA is a widely available imaging examination that may allow the evaluation of high-risk carotid plaque features. PURPOSE: Our aim was to evaluate the association between specific carotid plaque features on CTA and ipsilateral cerebrovascular ischemia. DATA SOURCES: We performed a systematic review of Ovid MEDLINE, Ovid Embase, Scopus, and the Cochrane Library from inception to March 2016 for articles that evaluated the relationship between CTA-detected carotid plaque features and ischemic events, defined as ipsilateral ischemic stroke or transient ischemic attack. STUDY SELECTION: Sixteen studies were ultimately included after screening 12,557. DATA ANALYSIS: Two readers recorded data from each study and assessed the study quality with all disagreements resolved by a third reader. A random-effects OR was used to evaluate the association between cerebrovascular ischemia and each of the evaluated plaque features. DATA SYNTHESIS: We found significant positive relationships with cerebrovascular ischemia for the presence of soft plaque (OR, 2.9; 95% CI, 1.4-6.0), plaque ulceration (OR, 2.2; 95% CI, 1.4-3.4), and increased common carotid artery wall thickness (OR, 6.2; 95% CI, 2.5-15.6). We found a significant negative relationship between calcified plaque and ipsilateral ischemia (OR, 0.5; 95% CI, 0.4-0.7). LIMITATIONS: We found heterogeneity in the existing literature secondary to lack of standardized plaque features and clinical definitions. CONCLUSIONS: Soft plaque, plaque ulceration, and increased common carotid artery wall thickness on CTA are associated with ipsilateral cerebrovascular ischemia, while calcified plaque is negatively associated with downstream ischemic events.