Calculated Tl and T2 MR Images and 3IP MR Spectra in Rabbit Thigh V2 Carcinoma to Monitor the Effect of Steroid Administration

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Abstract
T1 and T2 proton relaxation times in six rabbit thigh V2 carcinomas were obtaind from regions of interest on calculated MR images at 2.35 tesla before and after steroid administration. Mean T1 and T2 values of viable tumor tissue decreased after steroid administration, consistent with decreased tissue water content. After steroid withdrawal, T1 and T2 values returned toward baseline. Relaxation times of peritumoral muscle tissue and normal contralateral thigh muscle essentially remained unchanged. In a separate experiment, six rabbit thigh V2 carcinomas were monitored before and after steroids by 31P spectroscopy using a surface coil. No substantial steroid-related changes were recognizable. A fall of the ratio of phosphocreatine to inorganic phosphate and signal increase from phosphomonoester and phosphodiester compounds were observed during various stages of tumor growth. Analysis of 31P spectra changes and sequential measurements of relaxation times may prove valuable for assessment of tumor growth and therapeutic response in diagnostic oncology.