Simultaneous MRI Assessment of Perfusion and Permeability in Gliomas via Dynamic SAGE-EPI

Overview

This study demonstrates the feasibility of using dynamic spin-and-gradient-echo echoplanar imaging (dynamic SAGE-EPI) to concurrently measure cerebral blood flow, vascular permeability, and leakage effects in gliomas. Novel biomarkers such as TRATE correlate with established metrics like PSR and Ki67 expression, providing insights into tumor aggressiveness and blood–brain barrier integrity without additional contrast doses or scan time.

Background

Gliomas exhibit heterogeneous prognosis influenced by molecular and biological features, with aggressive tumors showing increased neoangiogenesis and blood–brain barrier (BBB) disruption. Conventional MRI techniques like dynamic susceptibility contrast (DSC) and dynamic contrast enhanced (DCE) imaging separately quantify vascular density and BBB permeability but require two contrast doses and longer scan times. Dual-echo DSC and dynamic SAGE-EPI sequences enable simultaneous acquisition of perfusion and permeability data, potentially reducing scan time and contrast agent exposure while providing novel quantitative biomarkers such as TRATE that are independent of acquisition parameters.

Data Highlights

The study included adult-type diffuse glioma patients undergoing dynamic SAGE-EPI MRI with a single dose of Gadavist® contrast agent. Dynamic SAGE-EPI acquired multiple echoes allowing separation of T1 and T2* effects. Metrics derived included TRATE (transverse relaxivity at tracer equilibrium), PSR (percentage of signal recovery), ΔR1,ss (steady-state T1 leakage), and Ktrans (volume transfer constant). Correlations between TRATE and PSR, and between ΔR1,ss and Ktrans were assessed. Tumor molecular markers such as Ki67 proliferation index and IDH mutation status were analyzed in relation to imaging biomarkers.

Key Findings

• TRATE correlated positively with PSR, confirming its role as a quantitative marker of cytoarchitectural features independent of acquisition parameters.
• ΔR1,ss showed correlation with Ktrans, validating its use as a marker of BBB permeability derived from dynamic SAGE-EPI data.
• Higher TRATE values were observed in tumors with increased Ki67 expression, indicating association with proliferative and aggressive tumor characteristics.
• Glioblastomas with IDH wild-type status exhibited elevated TRATE compared to lower-grade or IDH-mutant gliomas, reflecting more aggressive cytoarchitecture.
• Dynamic SAGE-EPI enabled simultaneous acquisition of perfusion and permeability metrics with a single contrast dose, reducing scan time and gadolinium exposure.

Clinical Implications

Dynamic SAGE-EPI MRI provides a comprehensive, efficient imaging approach to assess glioma vascular characteristics and BBB integrity simultaneously, aiding in tumor grading and molecular profiling. The novel TRATE biomarker offers a robust, acquisition-independent measure of tumor cytoarchitecture that may improve differentiation of aggressive gliomas. This technique may reduce patient risk by limiting contrast agent doses and scan duration while enhancing diagnostic information.

Conclusion

Dynamic SAGE-EPI enables concurrent evaluation of cerebral blood flow, vascular permeability, and leakage effects in gliomas, with novel biomarkers like TRATE correlating with established imaging and histopathological markers. This approach holds promise for improved, efficient glioma characterization in clinical practice.

References

1. Stokes et al. 2023 -- Concurrent Assessment of Cerebral Blood Flow, Vascular Permeability, and Leakage in Gliomas via Dynamic Spin-and-Gradient-Echo Echoplanar Imaging MRI