Clinical Imaging for Diagnostic Challenges in the Management of Gliomas: A Review

Abstract

Neuroimaging plays a critical role in the management of patients with gliomas. While conventional magnetic resonance imaging (MRI) remains the standard imaging modality, it is frequently insufficient to inform clinical decision‐making. There is a need for noninvasive strategies for reliably distinguishing low‐grade from high‐grade gliomas, identifying important molecular features of glioma, choosing an appropriate target for biopsy, delineating target area for surgery or radiosurgery, and distinguishing tumor progression (TP) from pseudoprogression (PsP). One recent advance is the identification of the T2/fluid‐attenuated inversion recovery mismatch sign on standard MRI to identify isocitrate dehydrogenase mutant astrocytomas. However, to meet other challenges, neuro‐oncologists are increasingly turning to advanced imaging modalities. Diffusion‐weighted imaging modalities including diffusion tensor imaging and diffusion kurtosis imaging can be helpful in delineating tumor margins and better visualization of tissue architecture. Perfusion imaging including dynamic contrast‐enhanced MRI using gadolinium or ferumoxytol contrast agents can be helpful for grading as well as distinguishing TP from PsP. Positron emission tomography is useful for measuring tumor metabolism, which correlates with grade and can distinguish TP/PsP in the right setting. Magnetic resonance spectroscopy can identify tissue by its chemical composition, can distinguish TP/PsP, and can identify molecular features like 2‐hydroxyglutarate. Finally, amide proton transfer imaging measures intracellular protein content, which can be used to identify tumor grade/progression and distinguish TP/PsP.

Association of dynamic susceptibility magnetic resonance imaging at initial tumor diagnosis with the prognosis of different molecular glioma subtypes

“…However, our cohort comprised low-grade tumors without contrast enhancement and occasionally lower perfusion than the healthy tissue. The hotspot method does not work in this case, and including the whole tumor volume in the measurement might represent the behavior of the tumor more thoroughly [ 20 , 21 , 31 ].…”

“…As an alternative, dynamic contrast-enhanced imaging is based on T1-weighted images and can quantify the microvascular permeability [ 32 ]. Arterial spin labeling measures the perfusion without contrast agent application and is independent of bias from leakage through the blood-brain barrier [ 21 ]. It has shown promising results in the initial diagnosis and detection of recurrent disease in gliomas [ 33 , 34 ].…”

“…The matrix of the FLAIR sequence was adjusted to the perfusion maps using an in-house Matlab-based application (Matlab 2014b, MathWorks Natick, Massachusetts, USA). We drew a volume of interest (VOI) covering the whole tumor with signal alteration in the FLAIR sequence and excluded surrounding edema, vessels, and necrotic areas [ 20 , 21 ].…”

Advancing Imaging to Enhance Surgery

“…For presumed recurrent glioma, the modality performs with a high sensitivity (range 96-100%), and diagnostic accuracy (range 82-94%) 126,129 . Applying hybrid 11C-METH PET/MRI, AA-PET outperformed MRI and differentiated progression versus pseudoprogression with a 97.1% sensitivity and 93.3% specificity compared to 86.1% sensitivity and 71.4% specificity for MRI 128,129 .…”

“…In comparison to conventional and advanced MRI, AA-PET retains a complementary role and allows a more precise distinction of gliomas due to the improved specificity and metabolic characterization 116,128 , even in case of recurrence or when assessing the response from pseudoprogression or other treatment-related changes. For presumed recurrent glioma, the modality performs with a high sensitivity (range 96-100%), and diagnostic accuracy (range 82-94%) 126,129 .…”