A Study on Prediction of effects of Radiotherapy by Magnetic Resonance Spectroscory

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(1) IN VIVO ^<31>P-MR SPECTROSCOPY OF EXPERIMENTAL TUMORSIn vivo ^<31>P-MR spectroscopy of various sizes of experimental tumors revealed progressive increase of Pi/beta -NTP, PME/beta -NTP and Pi/PME ratios in proportion with the tumors increasing in size. On the other hand, PCr/Pi, PDE/PME, PDE/Pi ratios and pHi decreased with the tumor size. Spectral changes after irradiation of tumors of the same size were as follows. (1) Transient marked decrease of NTP levels found immediately after irradiation had no direct relation to the later tumor growth. (2) Sequential changes of Pi/PME roughly correlated with the radiation dose. (3) Relative sequential changes of pHi, Pi/beta -NTP and PME/ beta -NTP observed from the 1st to the 2nd day were related to the later tumor growth. (4) These spectral changes correlated with the grade of G2+M accumulation in DNA histograms and the grade of necrosis or degeneration in histological examinations which were performed on the 5th day after irradiation.(2) ^<31>P-MR SPECTROSCOPY IN HUMAN SUPERFICIAL MALIGNANT TUMORS^<31>P-MR spectra obtained from human superficial malignant tumors were characterized by the presence of PME and PDE peaks and by alkaline shift of PHi.Although there are many variations in the spectral changes after treatments, decrease of PME and PDE peaks seems to be an early indicator of tumor response.