Sachi Okuchi

Certain brain tumors exhibit cystic components. MRI is particularly effective in characterizing the location, enhancement, and morphology of these cystic regions, enabling radiologists to narrow the differential diagnosis. Cystic components are often associated with circumscribed tumors and may be linked to favorable outcomes. High-grade tumors such as glioblastoma can also occasionally exhibit cystic components. Here, we summarize the imaging characteristics of representative cystic brain intraparenchymal neoplasms, including hemangioblastoma, pilocytic astrocytoma, pleomorphic xanthoastrocytoma, ganglioglioma, desmoplastic infantile ganglioglioma/astrocytoma, central neurocytoma, dysembryoplastic neuroepithelial tumor, ependymoma, glioblastoma, and metastases. This review aims to provide MRI features that facilitate differentiation of these tumors and support appropriate clinical management.

Background: Carotid artery stenosis is a major cause of stroke. Non‐contrast MR angiography (MRA) using time‐spatial labeling inversion pulse (Time‐SLIP) may offer potential advantages over 3D time‐of‐flight (TOF)‐MRA for simultaneous visualization of carotid, vertebral, and subclavian arteries, but remains uninvestigated. Purpose: To determine optimal black blood inversion time (TI) for visualizing the carotid and subclavian arteries using three‐dimensional (3D) fast field echo (FFE) Time‐SLIP MRA, and to compare its image quality with 3D TOF‐MRA. Study Type: Prospective. Subjects: 11 healthy adults (23–57 years, five females) and 4 patients (76–93 years, three females) with cervical vascular abnormalities. All patients had ICA stenosis. One patient exhibited ECA stenosis. Field Strength/Sequence: 3‐T, 3D FFE with Time‐SLIP using four TIs (1200–1800 ms) for healthy, 3D balanced steady‐state free precession (bSSFP) with Time‐SLIP using TI = 1600 for patients, and 3D TOF‐MRA for all subjects, covering the cervical and subclavian arteries. Assessment: For healthy subjects, relative signal intensity (SI) was measured using ROI for both sides of the carotid, vertebral, and subclavian arteries. For the same locations, vessel visibility was independently scored by three board‐certified radiologists. Patient images were qualitatively assessed for vessel visibility, abnormality, and artifacts. Statistical Tests: Friedman and Wilcoxon signed‐rank tests for pairwise comparisons of vessel visibility. A Bonferroni‐corrected significance threshold of p < 0.005 (= 0.05/10) was used. Results: In volunteer scans, relative SI for TI = 1600 was highest, while TI = 1800 showed the best visibility scores. 3D TOF‐MRA showed limitations in subclavian and brachiocephalic arteries due to low vessel‐to‐background contrast. In patients, FFE‐based Time‐SLIP provided better subclavian artery depiction than bSSFP‐based Time‐SLIP. Data Conclusion: 3D FFE with Time‐SLIP may enable high‐quality simultaneous visualization of the carotid and subclavian arteries when compared to 3D TOF‐MRA. In patients with vascular abnormalities, 3D FFE may provide superior subclavian artery depiction compared to 3D TOF‐MRA and 3D bSSFP. Evidence Level: 2. Technical Efficacy: Stage 2.

Background: Vessel‐specific bolus arrival time (BAT) has become calculated with higher spatiotemporal resolution on dynamic contrast‐enhanced magnetic resonance imaging using the Golden‐angle RAdial Sparse Parallel (GRASP) technique. However, its utility in moyamoya disease (MMD) is unclear.Purpose: To evaluate the relationship between BAT and arterial stenosis/periventricular anastomosis (PA) development, and the utility of BAT in MMD.Study Type: Retrospective.Subjects: Sixty‐one preoperative MMD patients (mean ± standard deviation age, 31.0 ± 20.4 years; 46 females; 25 children).Field Strength/Sequence: 3‐T, radial volume interpolated breath‐hold examination sequence, and three‐dimensional time‐of‐flight magnetic resonance angiography (3D TOF‐MRA).Assessment: Arterial stenosis, including internal carotid artery, middle cerebral artery (MCA), and posterior cerebral artery, and PA development, including lenticulostriate artery, thalamic perforator, and choroidal channel, were scored on TOF‐MRA. Differences in BAT (ΔBATs) between the right and left regions of interest (ROIs), including MCA M2, basal ganglia, thalamus, and choroid plexus, were compared with the right and left arterial stenosis score differences. ΔBATs between the MCA M2 and the ipsilateral basal ganglia, thalamus, and choroid plexus were compared with PA scores. A logistic regression model including ΔBAT was developed to assess the associations with recent transient ischemic attacks (TIAs).Statistical Tests: Kappa statistic, Friedman test, intraclass correlation coefficient, one‐way analysis of variance, Tukey–Kramer test, logistic regression analysis, and receiver operating characteristic analysis. p < 0.05 was considered significant.Results: ΔBATs between the right and left ROIs increased by 0.11–1.76 s depending on arterial stenosis score differences. ΔBATs between the MCA M2 and the ipsilateral ROIs decreased by 0.32–1.46 s with higher PA scores. Models including ΔBAT for recent TIAs showed areas under the curve of 0.81 in children and 0.78 in adults.Data Conclusion: BAT was indicative of arterial stenosis and PA development, and was associated with recent TIAs in MMD.Level of Evidence: 3Technical Efficacy: Stage 2

Background: To evaluate the clinical usefulness of thin-slice echo-planar imaging (EPI)-based diffusion-weighted imaging (DWI) with an on-console distortion correction technique, termed reverse encoding distortion correction DWI (RDC-DWI), in patients with non-functioning pituitary neuroendocrine tumor (PitNET)/pituitary adenoma. Methods: Patients with non-functioning PitNET/pituitary adenoma who underwent 3-T RDC-DWI between December 2021 and September 2022 were retrospectively enrolled. Image quality was compared among RDC-DWI, DWI with correction for distortion induced by B₀ inhomogeneity alone (B₀-corrected-DWI), and original EPI-based DWI with anterior-posterior phase-encoding direction (AP-DWI). Susceptibility artifact, anatomical visualization of cranial nerves, overall tumor visualization, and visualization of cavernous sinus invasion were assessed qualitatively. Quantitative assessment of geometric distortion was performed by evaluation of anterior and posterior displacement between each DWI and the corresponding three-dimensional T2-weighted imaging. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and apparent diffusion coefficient values were measured. Results: Sixty-four patients (age 70.8 ± 9.9 years [mean ± standard deviation]; 33 females) with non-functioning PitNET/pituitary adenoma were evaluated. In terms of susceptibility artifacts in the frontal and temporal lobes, visualization of left trigeminal nerve, overall tumor visualization, and anterior displacement, RDC-DWI performed the best and B₀-corrected-DWI performed better than AP-DWI. The right oculomotor and right trigeminal nerves were better visualized by RDC-DWI than by B₀-corrected-DWI and AP-DWI. Visualization of cavernous sinus invasion and posterior displacement were better by RDC-DWI and B₀-corrected-DWI than by AP-DWI. SNR and CNR were the highest for RDC-DWI. Conclusions: RDC-DWI achieved excellent image quality regarding susceptibility artifact, geometric distortion, and tumor visualization in patients with non-functioning PitNET/pituitary adenoma. Relevance statement: RDC-DWI facilitates excellent visualization of the pituitary region and surrounding normal structures, and its on-console distortion correction technique is convenient. RDC-DWI can clearly depict cavernous sinus invasion of PitNET/pituitary adenoma even without contrast medium. Key points: • RDC-DWI is an EPI-based DWI technique with a novel on-console distortion correction technique. • RDC-DWI corrects distortion due to B₀ field inhomogeneity and eddy current. • We evaluated the usefulness of thin-slice RDC-DWI in non-functioning PitNET/pituitary adenoma. • RDC-DWI exhibited excellent visualization in the pituitary region and surrounding structures. • In addition, the on-console distortion correction of RDC-DWI is clinically convenient. Graphical

Quantitative susceptibility mapping (QSM) is a unique technique for providing quantitative information on tissue magnetic susceptibility using phase image data. QSM can provide valuable information regarding physiological and pathological processes such as iron deposition, hemorrhage, calcification, and myelin. QSM has been considered for use as an imaging biomarker to investigate physiological status and pathological changes. Although various studies have investigated the clinical applications of QSM, particularly regarding the use of QSM in clinical practice, have not been examined well. This review provides on an overview of the basics of QSM and its clinical applications in neuroradiology.Level of Evidence: 2Technical Efficacy: Stage 2