Early detection of radiation therapy response in non-Hodgkin's lymphoma xenografts by in vivo 1H magnetic resonance spectroscopy and imaging

The purpose of the study was to investigate the capability of H-1 MRS and MRI methods for detecting early response to radiation therapy in non-Hodgkin's lymphoma (NHL). Studies were performed on the WSU-DLCL2 xenograft model in nude mice of human diffuse large B-cell lymphoma, the most common form of NHL. Radiation treatment was applied as a single 15 Gy dose to the tumor. Tumor lactate, lipids, total choline, T-2 and apparent diffusion coefficients (ADC) were measured before treatment and at 24 h and 72 h after radiation. A Hadamard-encoded slice-selective multiple quantum coherence spectroscopy sequence was used for detecting lactate (Lac) while a stimulated echo acquisition mode sequence was used for detection of total choline (tCho) and lipids. T-2- and diffusion-weighted imaging sequences were used for measuring T-2 and ADC. Within 24 h after radiation, significant changes were observed in the normalized integrated resonance intensities of Lac and the methylenes of lipids. Lac/H2O decreased by 38 +/- 15% (p = 0.03), and lipid (1.3 ppm, CH2)/H2O increased by 57 +/- 14% (p = 0.01). At 72 h after radiation, tCho/H2O decreased by 45 +/- 14% (p = 0.01), and lipid (2.8 ppm, polyunsaturated fatty acid)/H2O increased by 970 +/- 36% (p = 0.001). ADC increased by 14 +/- 2% (p = 0.003), and T-2 did not change significantly. Tumor growth delay and regression were observed thereafter. This study enabled comparison of the relative sensitivities of various H-1 MRS and MRI indices to radiation and suggests that H-1 MRS/MRI measurements detect early responses to radiation that precede tumor volume changes. Copyright (C) 2010 John Wiley & Sons, Ltd.