IN VIVO DETECTION OF RADIATION-INDUCED TISSUE DAMAGE IN KIDNEY BY C13 MRSI

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Recent introduction of nuclear hyperpolarization technique to liquid state enabled in vivo detection of C-13 labeled endogenous metabolites by MR spectroscopy imaging (MRSI). We investigate feasibility of employing this novel technique to assess radiation-induced tissue damage, which could result in radiotherapy, at moderate doses. We choose kidney tissues because kidney is a radiosensitive organ and provides internal control. In this study, we use Wistar male rats weighing 200-450 g to make the model by unilaterally irradiating one kidney with a collimated beam of X-rays. Initially, rats received radiation dose of 15 Gy and were subjected to C-13 magnetic resonance spectroscopy imaging (MRSI) at 21 days of postirradiation time. In MRSI, rats were intravenously injected with a hyperpolarized solution of 80 mM [113C]pyruvate. Hyperpolarization was performed by using DNP technique in HyperSenseTM polarizer (Oxford instruments). Fast chemical shift imaging (CSI) was performed at 3 T to acquire axial slices through both kidneys in every 6th second to measure both dynamic and spatial distribution of metabolites, pyruvate, lactate, and alanine. Animals are sacrificed after imaging to harvest kidney tissues for histopathology in order to confirm imaging observations. In our preliminary data, observed reduction of lactate production in the irradiated kidney in comparison to non-irradiated kidney suggests potential use of hyperpolarized C-13 metabolic imaging technique to detect radiation effects in kidney tissues.