[Changes in 31P-MR spectroscopy in murine experimental tumor (SCC VII) after irradiation]

Changes in the phosphate metabolism of transplanted squamous cell carcinoma VII (SCC VII) tumor were studied after irradiation using in vivo 31P-magnetic resonance spectroscopy (MRS). The results were as follows. 1) Phosphocreatine (PCr), gamma-,alpha- and beta-ATP, inorganic phosphate (Pi), phosphomonoester (PME) and phosphodiester (PDE) were detected in 31P-MR spectroscopy of SCC VII solid tumor. 2) 31P-MRS parameters, including PCr, beta-ATP, PCr/Pi, beta-ATP, beta-ATP/Pi and pH, increased after irradiation, then decreased with tumor regrowth. 3) Pi, PME and PDE decreased transiently after irradiation, and thereafter increased gradually. 4) PCr/Pi showed the most remarkable increase (p < 0.05) of all parameters following irradiation. Therefore, it may be employed as a therapeutic index in radiation therapy. Because PCr/Pi decreased again after irradiation prior to regrowth of tumor, it may be used to predict tumor regrowth. From these results, it was suggested that 31P-MRS was useful for monitoring the effects of radiation therapy, and regrowth after irradiation.