Brain

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.

Combining Diffusion Tensor Metrics and DSC Perfusion Imaging: Can It Improve the Diagnostic Accuracy in Differentiating Tumefactive Demyelination from High-Grade Glioma?

Editor’s Choice

Fourteen patients with tumefactive demyelinating lesions and 21 patients with high-grade gliomas underwent MR imaging with conventional, DTI, and DSC perfusion imaging. Conventional imaging sequences had a sensitivity of 80.9% and specificity of 57.1% in differentiating high-grade gliomas from tumefactive demyelinating lesions. DTI metrics (p:q tensor decomposition) and DSC perfusion demonstrated a statistically significant difference among enhancing portions in tumefactive demyelinating lesions and high-grade gliomas. The highest specificity was found for ADC, the anisotropic component of the diffusion tensor, and relative CBV. The authors conclude that DTI and DSC perfusion add profoundly to conventional imaging in differentiating tumefactive demyelinating lesions and high-grade gliomas.

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.

Predictive Utility of Marketed Volumetric Software Tools in Subjects at Risk for Alzheimer Disease: Do Regions Outside the Hippocampus Matter?

Editor’s Choice

The authors assessed the prognostic efficacy of individual-versus-combined regional volumetrics in 2 commercially available brain volumetric software packages for predicting conversion of patients with mild cognitive impairment to Alzheimer disease. One hundred ninety-two subjects (mean age, 74.8 years) diagnosed with mild cognitive impairment at baseline were studied. On univariable analysis of 11 NeuroQuant and 11 Neuroreader regional volumes, hippocampal volume had the highest area under the curve for both software packages (0.69, NeuroQuant; 0.68, Neuroreader) and was not significantly different between packages. They conclude that of the multiple regional volume measures available in FDA-cleared brain volumetric software packages, hippocampal volume remains the best single predictor of conversion of mild cognitive impairment to Alzheimer disease at 3-year follow-up.

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.

Evaluation of Encephaloduroarteriosynangiosis Efficacy Using Probabilistic Independent Component Analysis Applied to Dynamic Susceptibility Contrast Perfusion MRI

Editor’s Choice

In this prospective study, 13 patients underwent unilateral indirect cerebral revascularization and DSC-MR imaging before and after surgery. Conventional perfusion parameters (relative CBV, relative CBF, and TTP) and probabilistic independent components that reflect the relative contributions of DSC signals consistent with arterial, capillary, and venous hemodynamics were calculated and examined for significant changes after surgery. Before surgery, tissue within the affected hemisphere demonstrated a high probability for hemodynamics consistent with venous flow and a low probability for hemodynamics consistent with arterial flow, whereas the contralateral control hemisphere demonstrated the reverse. Consistent with symptomatic improvement, the probability for venous hemodynamics within the affected hemisphere decreased with time after surgery. The authors conclude that probabilistic independent component analysis yielded sensitive measurements of changes in local tissue perfusion that may be associated with newly formed vasculature after indirect cerebral revascularization surgery.

Synthetic MRI in the Detection of Multiple Sclerosis Plaques

Fellows’ Journal Club

In this retrospective study, synthetic T2-weighted, FLAIR, double inversion recovery, and phase-sensitive inversion recovery images were produced in 12 patients with MS after quantification of T1 and T2 values and proton density. Double inversion recovery images were optimized for each patient by adjusting the TI. The number of visible plaques was determined by a radiologist for a set of these 4 types of synthetic MR images and a set of conventional T1-weighted inversion recovery, T2-weighted, and FLAIR images. Conventional 3D double inversion recovery and other available images were used as the criterion standard. Synthetic MR imaging enabled detection of more MS plaques than conventional MR imaging in a comparable acquisition time (approximately 7 minutes). The contrast for MS plaques on synthetic double inversion recovery images was better than on conventional double inversion recovery images.

Abstract

Figure 1 from paper
An example of DIR optimization. A DIR image with a second TI of 460 ms (A) (as determined according to the equations in the main text) shows better delineation of MS plaques than a DIR image with a second TI of 360 ms (B) or 560 ms (C).

BACKGROUND AND PURPOSE

Synthetic MR imaging enables the creation of various contrast-weighted images including double inversion recovery and phase-sensitive inversion recovery from a single MR imaging quantification scan. Here, we assessed whether synthetic MR imaging is suitable for detecting MS plaques.

MATERIALS AND METHODS

Quantitative and conventional MR imaging data on 12 patients with MS were retrospectively analyzed. Synthetic T2-weighted, FLAIR, double inversion recovery, and phase-sensitive inversion recovery images were produced after quantification of T1 and T2 values and proton density. Double inversion recovery images were optimized for each patient by adjusting the TI. The number of visible plaques was determined by a radiologist for a set of these 4 types of synthetic MR

Quantifying Intracranial Plaque Permeability with Dynamic Contrast-Enhanced MRI: A Pilot Study

Editor’s Choice

The purpose of this study was to use DCE MR imaging to quantify the contrast permeability of intracranial atherosclerotic disease plaques in 10 symptomatic patients and to compare these parameters against existing markers of plaque volatility using black-blood MR imaging pulse sequences. Ktrans and fractional plasma volume (Vp) measurements were higher in plaques versus healthy white matter and similar or less than values in the choroid plexus. Only Ktrans correlated significantly with time from symptom onset. Dynamic contrast-enhanced MR imaging parameters were not found to correlate significantly with intraplaque enhancement or hyperintensity. The authors suggest that Ktrans may be an independent imaging biomarker of acute and symptom-associated pathologic changes in intracranial atherosclerotic disease plaques.

Intracranial Arteriovenous Shunting: Detection with Arterial Spin-Labeling and Susceptibility-Weighted Imaging Combined

Fellows’ Journal Club

Ninety-two consecutive patients with a known (n = 24) or suspected arteriovenous shunting (n = 68) underwent DSA and brain MR imaging, including arterial spin-labeling/SWI and conventional angiographic MR imaging. DSA showed arteriovenous shunting in 63 of the 92 patients. Interobserver agreement was excellent. In 5 patients, arterial spin-labeling/SWI correctly detected arteriovenous shunting, while the conventional angiographic MR imaging did not. The authors conclude that the combined use of arterial spin-labeling and SWI may be an alternative to contrast-enhanced MRA for the detection of intracranial arteriovenous shunting.

Abstract

Figure 3 from paper
A 60-year-old patient with a right paracentral AVM. ASL raw data (A) demonstrates a strong hypersignal at the anterior part of the right paracentral region (A, arrow). The slight venous hypersignal related to AVS was initially missed by the blinded readers by using SWI alone (B, arrowhead) but was correctly identified by using ASL and SWI combined (C, ASL/SWI merged image, arrow). Findings of time-resolved 4D contrast-enhanced MRA (D) were considered negative by the blinded readers. DSA reveals a small pial AVM in the right paracentral region (E, arrow).

BACKGROUND AND PURPOSE

Arterial spin-labeling and susceptibility-weighted imaging are 2 MR imaging techniques that do not require gadolinium. The study aimed to assess the accuracy of arterial spin-labeling and SWI combined for detecting intracranial arteriovenous shunting in comparison with conventional MR imaging.

MATERIALS AND METHODS

Ninety-two consecutive patients with a known (n = 24) or suspected arteriovenous shunting (n = 68) underwent digital subtraction angiography and brain MR imaging, including arterial spin-labeling/SWI and conventional angiographic MR imaging (3D TOF, 4D time-resolved, and 3D contrast-enhanced MRA). Arterial spin-labeling/SWI and conventional MR imaging were reviewed separately in a randomized order by 2 blinded radiologists who judged the presence or absence of arteriovenous shunting. The accuracy of arterial spin-labeling/SWI for the detection of

Metabolic Abnormalities in the Hippocampus of Patients with Schizophrenia: A 3D Multivoxel MR Spectroscopic Imaging Study at 3T

Editor’s Choice

Nineteen patients with schizophrenia and 11 matched healthy controls underwent MR imaging and multivoxel point-resolved 1H-MRS at 3T to obtain their hippocampal gray matter absolute NAA, Cr, and Cho concentrations. Patients’ average hippocampal GM Cr concentrations were 19% higher than those of controls. NAA and Cho showed no differences. The authors conclude that the findings suggest the hippocampal volume deficit in schizophrenia is not due to net loss of neurons, which is in agreement with histopathology studies but not with prior 1H-MR spectroscopy reports. Elevated Cr would be consistent with hippocampal hypermetabolism.