Fellows’ Journal Club

Differentiation of Enhancing Glioma and Primary Central Nervous System Lymphoma by Texture-Based Machine Learning

Fellows’ Journal Club

The authors evaluated the diagnostic performance of a machine-learning algorithm by using texture analysis of contrast-enhanced T1-weighted images for differentiation of primary central nervous system lymphoma (n=35) and enhancing glioma (n=71). The mean areas under the receiver operating characteristic curve were 0.877 for the support vector machine classifier; 0.878 for reader 1; 0.899 for reader 2; and 0.845 for reader 3. They conclude that support vector machine classification based on textural features of contrast-enhanced T1WI is noninferior to expert human evaluation in the differentiation of primary central nervous system lymphoma and enhancing glioma.

Intraforaminal Location of Thoracolumbar Radicular Arteries Providing an Anterior Radiculomedullary Artery Using Flat Panel Catheter Angiotomography

Fellows’ Journal Club

Ninety-four flat panel catheter angiotomography acquisitions obtained during the selective injection of intersegmental arteries providing an anterior radiculomedullary artery were reviewed. The location of radicular arteries could be ascertained in 78/94 flat panel catheter angiotomography acquisitions. Fifty-three acquisitions (67.9%) were on the left side, and 25 (32.1%), on the right, between T2 and L3. The arteries were found in the anterosuperior quadrant in 75 cases (96.2%), in the posterosuperior quadrant in 2 (2.6%), and in the anteroinferior quadrant in 1(1.3%). Needle placement in the anterosuperior quadrant (subpedicular approach) should be avoided during transforaminal epidural steroid injection. The authors advocate the posterolateral approach that allows placing the needle tip away from the documented position of ARMA contributors within the neural foramen, reducing the risk of intra-arterial injection or injury to the spinal vascularization.

Clinical and Imaging Characteristics of Diffuse Intracranial Dolichoectasia

Fellows’ Journal Club

The authors retrospectively reviewed a consecutive series of patients with diffuse intracranial dolichoectasia and compared demographics, vascular risk factors, additional aneurysm prevalence, and clinical outcomes with a group of patients with vertebrobasilar dolichoectasia. Twenty-five patients had diffuse intracranial dolichoectasia, and 139 had vertebrobasilar dolichoectasia. Patients with diffuse intracranial dolichoectasia were older than those with vertebrobasilar dolichoectasia and had a higher prevalence of abdominal aortic aneurysms, other visceral aneurysms, and smoking history. Patients with diffuse intracranial dolichoectasia were more likely to have aneurysm growth. They conclude that the natural history of patients with diffuse intracranial dolichoectasia is significantly worse than that in those with isolated vertebrobasilar dolichoectasia.

Site and Rate of Occlusive Disease in Cervicocerebral Arteries: A CT Angiography Study of 2209 Patients with Acute Ischemic Stroke

Fellows’ Journal Club

The authors used CTA to assess arterial stenosis and occlusion in an ischemic stroke population arriving at a tertiary stroke center within 24 hours of symptom onset to obtain a comprehensive picture of occlusive disease pattern. Extra- and intracranial pathology, defined as stenosis of ≥50% and occlusions, were registered and classified into 21 prespecified segments. In the 50,807 arterial segments available for revision, 1851 (3.6%) abnormal segments were in the ischemic (symptomatic) territory and another 408 (0.8%) were outside it (asymptomatic). In the 1211 patients with ischemic stroke imaged within 6 hours of symptom onset, 40.7% had symptomatic large, proximal occlusions. They conclude that CTA in patients with acute ischemic stroke shows large individual variations of occlusion sites and degrees. Approximately half of patients have no visible occlusive disease, and 40% imaged within 6 hours show large, proximal segment occlusions amenable to endovascular therapy.

Imaging Characteristics of Pediatric Diffuse Midline Gliomas with Histone H3 K27M Mutation

Fellows’ Journal Club

The 2016 WHO Classification of Tumors of the Central Nervous System includes “diffuse midline glioma with histone H3 K27M mutation” as a new diagnostic entity. This study of 33 patients with diffuse midline gliomas found histone H3 K27M mutation was present in 24 patients (72.7%) and absent in 9 (27.3%). The location was the thalamus in 27.3%; the pons in 42.4%; within the vermis/fourth ventricle in 15%; and the spinal cord in 6%. The radiographic features of diffuse midline gliomas with histone H3 K27M mutation were highly variable, ranging from expansile masses without enhancement or necrosis with large areas of surrounding infiltrative growth to peripherally enhancing masses with central necrosis with significant mass effect.

Evaluation of Collaterals and Clot Burden Using Time-Resolved C-Arm Conebeam CT Angiography in the Angiography Suite: A Feasibility Study

Fellows’ Journal Club

Ten C-arm conebeam CT perfusion datasets from 10 subjects with acute ischemic stroke acquired before endovascular treatment were retrospectively processed to generate time-resolved conebeam CTA. From time-resolved conebeam CTA, 2 experienced readers evaluated the clot burden and collateral flow in consensus by using previously reported scoring systems and assessed the clinical value of this novel imaging technique. The 2 readers agreed that time-revolved C-arm conebeam CTA was the preferred method for evaluating the clot burden and collateral flow compared with other conventional imaging methods. They conclude that comprehensive evaluations of clot burden and collateral flow are feasible by using time-resolved C-arm conebeam CTA data acquired in the angiography suite.

Genetically Defined Oligodendroglioma Is Characterized by Indistinct Tumor Borders at MRI

Fellows’ Journal Club

The authors wanted to determine whether imaging characteristics previously associated with oligodendroglial tumors were still applicable given the 2016 WHO classification that made IDH mutation and 1p/19q codeletion the defining features of oligodendroglioma. They found that 92% of genetically defined oligodendrogliomas had noncircumscribed borders, compared with 45% of non-1p/19q codeleted tumors with at least partial histologic oligodendroglial morphology. Ninety-nine percent of oligodendrogliomas were heterogeneous on T1- and/or T2-weighted imaging.

MR Fingerprinting of Adult Brain Tumors: Initial Experience

Fellows’ Journal Club

MR fingerprinting is a technique in which pseudorandomized acquisition parameters are used to simultaneously quantify multiple tissue properties, including T1 and T2 relaxation times. The authors evaluated the ability of MR fingerprinting–derived T1 and T2 relaxometry to differentiate the 3 common types of intra-axial brain tumors (17 glioblastomas, 6 lower grade gliomas, and 8 metastases). Using these parameters, they explored the T1 and T2 properties of peritumoral white matter in various tumor types. Mean T2 values could differentiate solid tumor regions of lowergrade gliomas from metastases and the mean T1 of peritumoral white matter surrounding lowergrade gliomas differed from peritumoral white matter around glioblastomas.

Effects of MRI Protocol Parameters, Preload Injection Dose, Fractionation Strategies, and Leakage Correction Algorithms on the Fidelity of Dynamic-Susceptibility Contrast MRI Estimates of Relative Cerebral Blood Volume in Gliomas

Fellows’ Journal Club

The authors used DSC-MR imaging simulations to examine the influence of various acquisition parameters and leakage-correction strategies on the faithful estimation of CBV. Optimal strategies were determined by protocol with the lowest mean error. They conclude that the choice of image acquisition and preload dosing and/or fractionation has tremendous impact on the fidelity of CBV estimation. A variety of acquisition strategies can be used to obtain similar accuracy of CBV estimation, while the bidirectional leakage-correction algorithm aids in minimizing errors in CBV estimation under all scenarios.

Transverse Sinus Stenosis Is the Most Sensitive MR Imaging Correlate of Idiopathic Intracranial Hypertension

Fellows’ Journal Club

MR imaging and MRV images from 63 patients with idiopathic intracranial hypertension and 96 controls were reviewed by using 3 independent procedures. MRV images were graded for the presence and degree of stenosis of the transverse sinus. Postgadolinium coronal T1-weighted sequences were evaluated independent of MRV. The dimensions of the proximal and distal transverse sinus were measured. Transverse sinus stenosis was identified bilaterally on MRV in 94% of patients with IIH and in 3% of controls. On coronal T1 postgadolinium MR images, transverse sinus stenosis was identified in 83% of patients with IIH and 7% of controls. The authors conclude that transverse sinus stenosis is the most useful and sensitive imaging indicator of this disease state.