In Vivo Detection of Radiation-Induced Metabolic Response in Rat Kidneys by 13C Hyperpolarized MRSI

Introduction: The safe delivery of an ionization radiation dose to a tumor is often limited by the irradiation of the adjacent normal tissues. In total body irradiation, for instance, unintended radiation dose to the kidneys can result in the loss of renal function and radiation-induced nephropathy[1]. Radiation injuries in radiosensitive late responding critical organs, such as the kidneys, can take months or years to become apparent as structural changes[2]. Early detection of radiation-induced tissue damage is beneficial to manage the risk of late complications and to better design radiation therapy. Changes of lactate dehydrogenase (LDH) and lactate levels have been observed in various ex vivo animal tissues within few days following x-ray irradiation[3, 4]. Therefore, it may be suggested that metabolic response may reflect early signs of radiation-induced tissue alterations when measured in vivo. C hyperpolarized MRI/MR spectroscopic imaging (MRSI) is an emerging technique that can be utilized to measure in vivo metabolic response [5, 6]. The purpose of this study was to explore the potential of using currently available hyperpolarized C MRSI techniques to detect radiation-induced metabolic alterations in rat kidneys at clinically relevant radiation doses.