pH Mapping of Gliomas Using Quantitative Chemical Exchange Saturation Transfer MRI: Quasi-Steady-State, Spillover-,...

Area of Science:

• Biomedical Imaging
• Neuro-oncology
• Quantitative MRI

Background:

• In-situ pH mapping is crucial for understanding glioma progression and guiding therapy.
• Chemical Exchange Saturation Transfer (CEST) offers noninvasive pH imaging but faces quantification challenges in gliomas.

Purpose of the Study:

• To quantify glioma pH by measuring proton exchange rates using optimized omega plot analysis.
• To establish a reliable method for in-situ pH measurement in gliomas.

Main Methods:

• Prospective study utilizing CEST imaging at 11.7T and 7.0T.
• Employed omega plot analysis, quasi-steady-state (QUASS) analysis, and multi-pool Lorentzian fitting.
• Validated in creatine phantoms, rat glioma xenografts, and human glioma patients.

Main Results:

• Omega plot analysis showed a linear correlation (R² > 0.98) between MTRrex and ω₁² in gliomas.
• Glioma pH measurements were independent of concentration changes.
• Rat gliomas exhibited decreased exchange rates compared to normal tissue (P=0.025), a pattern mirrored in human gliomas.

Conclusions:

• QUASS-based, spillover-, and MT-corrected omega plot analysis is a feasible method for quantifying glioma pH.
• This technique enables reliable in-situ pH mapping for improved glioma assessment.
• The findings support the clinical utility of advanced MRI techniques for brain tumor characterization.