Tissue Cell Fraction (TCF) from Quantitative Sodium MR Imaging Measures Real-Time Tumor Response to Fractionated Radiation Therapy

Keith R. Thulborn¹, Ian C. Atkinson¹, Aiming Lu¹, Saad Jamil¹, Wesley McClain¹, Matthew Koshy¹, Pauliah Mohan², Kathryn Beal², Antonio M. Omuro², Michelle Bradbury²

Quantitative sodium MR imaging and the two-compartment model of tissue sodium concentration have been used to measure weekly and accumulated changes in tissue cell fraction (TCF) of human high grade brain tumors during fractionated radiation therapy. Whereas some tumors show regionally distinct responses within weekly intervals, others show no response. This near real-time capability of early monitoring of tumor responsiveness to treatment could be used to guide adaptive therapy or to switch to more effective alternative therapy. The lack of responsiveness in many of these tumors explains why the prognosis remains so grime for these aggressive tumors.