Glioma monitoring and assessment: Utility of amide proton transfer MRI

Abstract

AbstractMagnetic resonance imaging (MRI) plays a key role in the planning of glioma biopsy as well as postoperative monitoring for recurrence or progression. This review describes amide proton transfer (APT) MRI and its application to glioma imaging, including the use of APT MRI to address unmet clinical needs, common APT sequence parameter choices, and post‐processing methods. APT is a chemical exchange saturation transfer MRI technique that is sensitive to exchanging protons between water molecules and proteins and peptides containing amide groups in tissue. APT has shown promise in several areas including: differentiating glioma grading, correlation to cellular proliferation, association with molecular markers, and distinguishing pseudo‐progression from true progression. Multiple studies have shown that APTw values are affected by tumor markers including isocitrate dehydrogenase status and O6‐methylguanine‐DNA‐methyltransferase promoter status, demonstrating the potential for APT MRI. APT has also been shown to correlate with markers of cellular proliferation, including Ki‐67 index and low apparent diffusion coefficient on diffusion‐weighted imaging. Finally, this review also examines the potential limitations of APT MRI in clinical glioma imaging including the lack of standardization of acquisition and processing as well as the impact of 𝑇1, nuclear overhauser effect and magnetization transfer on the APT signal.