Sijens P E, Baldwin N J, Ng T C
Magnetic Resonance Research Center, Cleveland Clinic Foundation, Ohio, USA.
Invest Radiol. 1997 Jan;32(1):39-43. doi: 10.1097/00004424-199701000-00006.
In previous phosphorus-31 (31P) magnetic resonance (MR) spectroscopy studies of radiation-induced fibrosarcoma (RIF-1), tumor model single-dose x-ray irradiation was applied at subcurative doses. A more effective x-ray does was used in this study, allowing correlation of treatment efficacy with the early changes observed in the 31P MR spectra of RIF-1 tumors.
Subcutaneous RIF-1 tumors of 60 mice were examined by 31P MR spectroscopy shortly before a single localized x-ray dose of 40 Gy and at eight times (2, 12, 24, 48, 72, 120, 168, and 216 hours) thereafter.
Early increases in the relative concentration of inorganic phosphate and decreases in adenosine triphosphate (ATP), most notably at 2 and 12 hours (each P < 0.00001), were observed that lasted up to 48 hours after irradiation. Phosphomonoester and tumor pH showed decreases that reversed even earlier. Reduction of ATP measured at 48 hours after irradiation was, however, correlated with percent tumor shrinkage observed during the subsequent weeks (r = -0.59; P < 0.00001).
Sustained loss of RIF-1 tumor ATP is predictive of treatment efficacy. Temporary depression of high-energy phosphate in favor of inorganic phosphate does not necessarily lead to cell death.
在先前对辐射诱导纤维肉瘤（RIF-1）的磷-31（³¹P）磁共振（MR）波谱研究中，肿瘤模型采用了低于治愈剂量的单次X线照射。本研究使用了更有效的X线剂量，从而能够将治疗效果与在RIF-1肿瘤的³¹P MR波谱中观察到的早期变化相关联。
在对60只小鼠皮下接种的RIF-1肿瘤进行单次局部40 Gy X线照射前不久，以及照射后8个时间点（2、12、24、48、72、120、168和216小时），通过³¹P MR波谱对其进行检查。
观察到无机磷酸盐相对浓度早期升高，三磷酸腺苷（ATP）降低，最明显的是在2小时和12小时（均P < 0.00001），这种情况在照射后持续长达48小时。磷酸单酯和肿瘤pH值降低，且恢复得更早。然而，照射后48小时测得的ATP降低与随后几周观察到的肿瘤缩小百分比相关（r = -0.59；P < 0.00001）。
RIF-1肿瘤ATP的持续丧失可预测治疗效果。高能磷酸盐暂时向无机磷酸盐的转变不一定会导致细胞死亡。
