Improved Detectability of Brain Stem Ischemia by Combining Axial and Coronal Diffusion-Weighted Imaging.

BACKGROUND AND PURPOSE: To evaluate the benefit of a coronal diffusion-weighted imaging (DWI) in addition to standard axial DWI for the detection of brain stem infarctions. METHODS: A retrospective analysis of patients with symptoms consistent with acute and subacute brain stem infarction who received magnetic resonance imaging, including axial and coronal DWI. Diffusion restrictions were identified by 2 independent raters blinded for the final clinical diagnosis in 3 separate reading steps: axial DWI, coronal DWI, and combined axial and coronal DWI. Lesion location and certainty level were both documented for each reading step. In cases of reader disagreement, an additional consensus reading was performed. RESULTS: Two hundred thirty-nine patients were included. Of these, 124 patients (51.9%) were clinically diagnosed with brain stem infarction. Sensitivity, specificity, positive, and negative predictive values were best for combined DWI assessment (90.3%, 99.1%, 99.1%, and 90.5%) compared with axial (85.5%, 94.9%, 94.6%, and 85.8%) and coronal DWI alone (87.9%, 96.5%, 96.5%, and 88.1%). Diffusion restriction on combined DWI was diagnosed in 112/124 patients compared with 106/124 on axial DWI and 109/124 on coronal DWI. Interobserver agreement for the detection of brain stem lesions was the highest in the combined rating step (Cohen κ coefficient=0.94). CONCLUSIONS: Coronal DWI sequences might improve the detection rate of brain stem infarction compared with standard axial DWI. The combined coronal and axial DWI provides the best detection rate while minimally increasing scan times.

Impact of intravenous alteplase on sub-angiographic emboli in high-resolution diffusion-weighted imaging following successful thrombectomy.

OBJECTIVE: Thrombus microfragmentation causing peripheral emboli (PE) during mechanical thrombectomy (MT) may modulate treatment effects, even in cases with successful reperfusion. This study aims to investigate whether intravenous alteplase is of potential benefit in reducing PE after successful MT. METHODS: Patients from a prospective study treated at a tertiary care stroke center between 08/2017 and 12/2019 were analyzed. The main inclusion criterion was successful reperfusion after MT (defined as expanded thrombolysis in cerebral infarction (eTICI) scale ≥ 2b50) of large vessel occlusion anterior circulation stroke. All patients received a high-resolution diffusion-weighted imaging (DWI) follow-up 24 h after MT for PE detection. Patients were grouped as "direct MT" (no alteplase) or as MT plus additional intravenous alteplase. The number and volume of ischemic core lesions and PE were then quantified and analyzed. RESULTS: Fifty-six patients were prospectively enrolled. Additional intravenous alteplase was administered in 46.3% (26/56). There were no statistically significant differences of PE compared by groups of direct MT and additional intravenous alteplase administration regarding mean numbers (12.1, 95% CI 8.6-15.5 vs. 11.1, 95% CI 7.0-15.1; p = 0.701), and median volume (0.70 mL, IQR 0.21-1.55 vs. 0.39 mL, IQR 0.10-1.62; p = 0.554). In uni- and multivariable linear regression analysis, higher eTICI scores were significantly associated with reduced PE, while the administration of alteplase was neither associated with numbers nor volume of peripheral emboli. Additional alteplase did not alter reperfusion success. CONCLUSIONS: Intravenous alteplase neither affects the number nor volume of sub-angiographic DWI-PE after successful endovascular reperfusion. In the light of currently running randomized trials, further studies are warranted to validate these findings. KEY POINTS: • Thrombus microfragmentation during endovascular stroke treatment may cause peripheral emboli that are only detectable on diffusion-weighted imaging and may directly compromise treatment effects. • In this prospective study, the application of intravenous alteplase did not influence the occurrence of peripheral emboli detected on high-resolution diffusion-weighted imaging. • A higher degree of recanalization was associated with a reduced number and volume of peripheral emboli and better functional outcome, while contrariwise, peripheral emboli did not modify the effect of recanalization on modified Rankin Scale scores at day 90.

Radiomics of Brain MRI: Utility in Prediction of Metastatic Tumor Type.

Purpose To investigate the feasibility of tumor type prediction with MRI radiomic image features of different brain metastases in a multiclass machine learning approach for patients with unknown primary lesion at the time of diagnosis. Materials and methods This single-center retrospective analysis included radiomic features of 658 brain metastases from T1-weighted contrast material-enhanced, T1-weighted nonenhanced, and fluid-attenuated inversion recovery (FLAIR) images in 189 patients (101 women, 88 men; mean age, 61 years; age range, 32-85 years). Images were acquired over a 9-year period (from September 2007 through December 2016) with different MRI units, reflecting heterogeneous image data. Included metastases originated from breast cancer (n = 143), small cell lung cancer (n = 151), non-small cell lung cancer (n = 225), gastrointestinal cancer (n = 50), and melanoma (n = 89). A total of 1423 quantitative image features and basic clinical data were evaluated by using random forest machine learning algorithms. Validation was performed with model-external fivefold cross validation. Comparative analysis of 10 randomly drawn cross-validation sets verified the stability of the results. The classifier performance was compared with predictions from a respective conventional reading by two radiologists. Results Areas under the receiver operating characteristic curve of the five-class problem ranged between 0.64 (for non-small cell lung cancer) and 0.82 (for melanoma); all P values were less than .01. Prediction performance of the classifier was superior to the radiologists' readings. Highest differences were observed for melanoma, with a 17-percentage-point gain in sensitivity compared with the sensitivity of both readers; P values were less than .02. Conclusion Quantitative features of routine brain MR images used in a machine learning classifier provided high discriminatory accuracy in predicting the tumor type of brain metastases. © RSNA, 2018 Online supplemental material is available for this article.

Spectrally fat-suppressed coronal 2D TSE sequences may be more sensitive than 2D STIR for the detection of hyperintense optic nerve lesions.

OBJECTIVES: The aim of the study is to compare coronal spectrally fat-suppressed 2D turbo spin-echo (TSE) with 2D short-tau inversion-recovery (STIR) sequences for the detection of optic nerve hyperintensities in patients with acute optic nerve neuritis (ON). METHODS: A retrospective review of patients with suspected unilateral ON and pathological visual evoked potentials, who received coronal TSE and STIR sequences with similar fast and clinically feasible acquisition times in addition to our standard imaging protocol. All images were evaluated and compared concerning the presence of optic nerve lesions, lesion lengths, and signal intensities in different anatomical parts of the optic nerves and CNR measures. A summary confidence score (CS) was calculated based on each reader's subjective confidence regarding the scoring items. RESULTS: Interobserver agreements regarding the detection of optic nerve lesions were excellent for both sequences (TSE, κ = 0.89 and STIR, κ = 0.80). Greater extensions (17.4 ± 6.3 mm vs. 14.1 ± 5.8 mm), as well as higher numbers of optic nerve lesions in symptomatic nerves, were detected on TSE (49/52) compared with STIR (45/52) sequences (both p < 0.001). Overall CS were significantly (p < 0.001) higher for TSE (2.8) compared with STIR (2.1) sequences regarding the presence or absence of optic nerve lesions. CNR ratios of lesions' mean signal intensities vs. ipsilateral surrounding orbital fat and vs. signal intensity measurements from contralateral optic nerves were significantly higher on TSE compared with STIR (p < 0.001 for both comparisons). CONCLUSION: Spectrally fat-suppressed coronal 2D TSE sequences appear to be more sensitive for the detection of hyperintense optic lesions compared with 2D STIR sequences. KEY POINTS: • Spectrally fat-suppressed TSE sequences showed higher detection rates of hyperintense optic nerve lesions, as well as a higher reader confidence scores compared with STIR. • Optic nerve signal abnormalities on TSE sequences were brighter and showed a greater expansion along the optic nerve course. • CNR measures were significantly higher on TSE compared with STIR, when comparing the ratios of mean signal intensities of optic nerve lesions to ipsilateral orbital fat and to contralateral healthy optic nerves of both sequences.

Is visual evaluation of aneurysm coiling a reliable study end point? Systematic review and meta-analysis.

BACKGROUND AND PURPOSE: Angiographic occlusion as a surrogate marker of satisfactory aneurysm treatment is commonly used in clinical trials although some pitfalls have to be considered. To investigate the inter-rater reliability of visual rating of aneurysm occlusion as study end point, we performed a systematic review and meta-analysis. METHODS: Electronic databases (MEDLINE, EMBASE, PubMed, and the Cochrane Library) were searched up to June 2014. Assessment of risk for bias was based on the Quality Appraisal Tool for Studies of Diagnostic Reliability and the Guidelines for Reporting Reliability and Agreement studies. Inter-rater reliability estimates were pooled across studies using meta-analysis, and the influence of several factors (eg, imaging methods, grading scales, and occlusion rate) was tested with meta-regression. RESULTS: From 1193 titles, 644 abstracts and 87 full-text versions were reviewed. Twenty-six articles met the inclusion criteria and provided 77 reliability estimates. Twenty-one different rating scales were used, and statistical analysis varied. Mean inter-rater agreement of the pooled studies was substantial (κ=0.65; 95% confidence interval, 0.60-0.69). Reliability varied significantly as a function of imaging methods, grading scales, occlusion rates, and their interaction. Observer agreement substantially increased with increasing occlusion rate in digital subtraction angiography but not in MR angiography. Reliability was higher in studies using 2- or 3-value grading scales than in studies with 4-value grading scales. CONCLUSIONS: There is significant heterogeneity between studies evaluating the reliability of visual evaluation of aneurysm coiling. On the basis of our analysis, we found that the combination of magnetic resonance angiography, 3-value grading scale, and 2 trained raters seems most promising for usage as surrogate study end points.

Effect of Balloon Guide Catheter Utilization on the Incidence of Sub-angiographic Peripheral Emboli on High-Resolution DWI After Thrombectomy: A Prospective Observational Study.

Background: Thrombus fragmentation causing distal emboli is a feared complication during mechanical thrombectomy (MT). We aimed to investigate the impact of procedural parameters and thrombus properties on the incidence of peripheral emboli after MT for large vessel occlusions (LVO). Methods: We performed a prospective analysis of patients with LVO stroke successfully treated with MT, defined as a score of 2b, 2c, or 3 on the thrombolysis in cerebral infarction (TICI) scale. A follow-up MRI including high-resolution diffusion-weighted imaging (DWI) was performed within 24 h following MT. The primary endpoint was the number and volume of peripheral emboli, classified as punctuate DWI lesions distant to the diffusion-restricted core lesion. Further analysis included the influence of baseline characteristics, procedural and outcome parameters, and thrombus properties on peripheral emboli. Results: Thirty-seven patients with successful MT met the inclusion criteria. Use of a balloon guide catheter (BGC) and TICI were the only independent predictors for a reduced number of peripheral emboli. The use of a BGC led to a significant reduction in the number and volume of peripheral emboli, with a median number/volume of peripheral emboli of 4.5/287 µl (IQR 1.25-8.25/76-569 µl) vs. 12/938 µl (IQR 4-19/242-1,836 µl). In cases where BGC was not employed, the number of peripheral emboli increased with decreasing TICI scores. Conclusions: BGC-aided MT reduces the number of peripheral emboli in successful but incomplete reperfusion (TICI 2b and 2c). The effectiveness of this strategy therefore goes above and beyond that which can be demonstrated by the TICI score alone.

Sub-angiographic peripheral emboli in high resolution DWI after endovascular recanalization.

BACKGROUND AND AIM: To analyze the incidence of peripheral emboli after successful mechanical thrombectomy (MT) of intracranial large vessel occlusions (LVO). METHODS: We performed a prospective analysis of patients with intracranial LVO who underwent successful MT and received a 1.5 T MRI including diffusion-weighted imaging (DWI) in standard- and high-resolution as well as susceptibility-weighted imaging (SWI) on the day following the intervention. Reperfusion grade was assessed on post-thrombectomy digital subtraction angiography (DSA) using the expanded thrombolysis in cerebral infarction (eTICI) scale. Punctuate DWI lesions distal to the DWI core lesion were classified as peripheral emboli. DWI lesions outside the primary affected vascular territory were classified as emboli into new territories. Additionally, SWI and post-thrombectomy DSA were analyzed and correlated to findings on DWI. RESULTS: Twenty-eight patients undergoing successful MT met the inclusion criteria. In 26/28 patients (93%), a total of 324 embolic lesions were detected in DWI representing 2.1% of the cumulated ischemic core volume. 151 peripheral emboli were detected in standard-resolution DWI, 173 additional emboli were uncovered in high-resolution DWI. Eight out of nine patients with an eTICI 3 reperfusion had embolic lesions (29 DWI lesions). 9.6% (31/324) of peripheral emboli were observed in vascular territories not affected by the LVO. SWI lesions were observed in close proximity to 10.2% (33/324) of DWI lesions. CONCLUSIONS: Peripheral emboli are frequent after MT even after complete reperfusion. These emboli occur rather in the vascular territory of the occluded vessel than in other territories. A large proportion of peripheral emboli is only detected by high-resolution DWI.

Improved detectability of acute and subacute brainstem infarctions by combining standard axial and thin-sliced sagittal DWI.

BACKGROUND AND PURPOSE: Most false negative findings in DWI of ischemic stroke are in patients with minor deficits clinically localized to the brainstem. Our goal was to evaluate the benefit of a thin-sliced sagittal DWI in addition to conventional axial DWI at 1.5T for the detection of brainstem infarctions. METHODS: Data of patients with symptoms consistent with acute and subacute brainstem infarction and an MRI examination including standard axial DWI and thin-sliced sagittal DWI were retrospectively analyzed. Patients with the later diagnosis of a TIA, an inflammation or a tumor of the brainstem were excluded from analysis. Diffusion restrictions were identified by two independent raters blinded for the final clinical diagnosis in three separate reading steps: First, only axial DWI, secondly only sagittal DWI, and lastly both DWIs together. Presence and size of DWI-lesions were documented for each plane. Differences between the observers were settled in consensus in a separate joint reading. RESULTS: Of 73 included patients, 46 patients were clinically diagnosed with brainstem infarction. Inter-observer agreement was excellent for the detection of brainstem lesions in axial and sagittal DWI (kappa = 0.94 and 0.97). In 28/46 patients (60.9%) lesions were detected in the axial plane alone, whereas in 6 more patients (73.9%) lesions were detected in the review of both sequences together. All lesions undetectable in the axial plane were smaller than 5 mm in cranio-caudal direction. CONCLUSIONS: Thin-sliced sagittal DWI in addition to axial DWI improves the detection rate of brainstem infarction with little additional expenditure of time.