DIRECT PO2 MEASUREMENTS BY EPR OXIMETRY TO OPTIMIZE SPLIT DOSE RADIATION: CANCER

瘤内电子顺磁共振血氧仪 氧敏感顺磁材料的植入(印度墨水) 用来重复监测单个小鼠肿瘤的氧分压 分割剂量照射前后。结果证实了我们的 先前报道的辐射诱导纤维肉瘤的时间进程 (RIF-1)小鼠肿瘤缺氧24小时后氧分压升高的变化 照射和最大复氧时间约为72小时。肿瘤生长 被用来比较第二个低氧组的反应 放射剂量是肿瘤放疗后的最小剂量。 PO2(初始照射后24小时)至“含氧”组，其中 在复氧后进行第二次照射。 发生(两次给药间隔72小时)。值得注意的是 与“低氧”相比，“低氧”的肿瘤倍增时间更长。 组，表明测量的PO2变化反映了 肿瘤放射敏感性。两次剂量之间的24小时间隔导致 肿瘤的复氧延迟，而导致72小时的间隔 在第二个缺氧/复氧循环中。我们的结果表明 用EPR血氧仪重复直接测量肿瘤中的PO2可以是 有助于对分割辐射剂量进行计时，以实现局部改善 肿瘤的控制。

Electron paramagnetic resonance (EPR) oximetry with intratumoral implantation of an oxygen-sensitive paramagnetic material (India ink) was used to monitor repeatedly the pO2 in individual murine tumors before and after split dose irradiation. Results confirmed our previously reported time course in radiation-induced-fibrosarcoma (RIF-1) murine tumors of pO2 changes of increased hypoxia 24 hr after irradiation and maximum reoxygenation at about 72 hrs. Tumor growth was used to compare the response in a "hypoxic" group where the second dose of radiation was delivered at the minimum post-radiation tumor pO2 (24 hr after initial irradiation) to an "oxic" group where the second dose of radiation was delivered after reoxygenation had occurred (72 hr interval between doses). There were significantly longer tumor doubling times in the "oxic" compared to the "hypoxic" group, indicating that the measured pO2 changes reflected changes in tumor radiosensitivity. A 24 hr interval between doses resulted in a delay of reoxygenation in the tumors, while a 72 hr interval resulted in a second cycle of hypoxia/reoxygenation. Our results suggest that repeated direct measurements of pO2 in tumors by EPR oximetry could be useful in timing split radiation doses to achieve improved local control of tumors.