Effects of radiation on the NMR relaxation effects of aqueous solutions of gadolinium contrast agents.

We investigate the effects of radiation on aqueous solutions of two common MRI contrast agents based on paramagnetic gadolinium chelates. Aqueous solutions of Gd-DTPA (gadolinium diethylenetriaminepentaacetic acid) and Gd-HP-DO3A (gadoteridol), as well as Gd-DTPA in the presence of concentrations of several common metabolites (N-acetylaspartate, Choline, Creatine and myo-inositol) typical of conditions in vivo, were irradiated at dose levels up to 30 Gy using a 6 MV linear accelerator and imaged using a 1.5 T MRI system. In addition, the effects of radiation dose on solution relaxation rates were compared with the effects of temperature by subjecting the same samples to varying temperatures over a range of 4 K using the same experimental conditions and imaging sequences. Radiation caused small increases (1% or less at a dose of 20 Gy) in the relaxivity of solutions. The effects of radiation on relaxivities were orders of magnitude smaller than the effects of temperature over the range in this study. Copyright 2008 John Wiley & Sons, Ltd.