NON INVASIVE MR LOCALIZATION OF OXYGEN SENSITIVE EPR MATERIALS

电子顺磁共振（EPR）血氧测定，肿瘤内 氧敏感顺磁材料（印度墨水）植入 用于重复监测单个小鼠肿瘤中的pO 2 分次剂量照射前后。 结果证实， 先前报道的放射诱导纤维肉瘤的时间进程 （RIF-1）给药后24小时缺氧增加的pO 2变化的小鼠肿瘤 照射并在约72小时达到最大再氧合。 肿瘤生长 用于比较“缺氧”组的反应， 在最小放射后肿瘤处递送放射剂量 pO 2（初始照射后24小时）与“好氧”组相比， 第二次剂量的放射治疗是在复氧后进行的， 发生（给药间隔72小时）。 有显著 与“缺氧”相比，“有氧”中的肿瘤倍增时间更长 组，表明测量的pO 2变化反映了 肿瘤放射敏感性 两次给药之间间隔24小时， 延迟肿瘤中的复氧，而72小时的间隔导致 在缺氧/复氧的第二个循环中。 我们的结果表明 通过EPR血氧测定法重复直接测量肿瘤中的pO 2， 用于定时分割辐射剂量以实现改善的局部 控制肿瘤。

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.