Feasibility of 99Tcm-HL91 hypoxia imaging to predict the Radiosensitization of hyperbaric oxygenation

To observe the feasibility of 99Tcm -HL91 hypoxia imaging to predict the radiosensitization of hyperbaric oxygenation, the mice bearing H22 tumor KM were placed into hyperbaric oxygen chamber for a certain time, and were divided into three groups of 15 min, 30 min and 60 min, according to the time of being out of hyperbaric oxygenation. Five mice of every group were carried on 99Tcm -HL91 hypoxia imaging and 60Co therapy respectively. The mice without hyperbaric oxygenation therapy were regarded as control group. The T/NT of tumor to contralateral muscles were calculated by ROI technology for all of the imaging mice. After acquired, the mice were killed soon. The tumors were excised and weighted, and the radioactivity and differential uptake ratio(DUR) were computed by quantitating the tracer uptake. Every radiotherapy group mice were observed and recorded the tumors growth days and the average survival time. The results showed that the DUR, T/NT and the delay times of the tumors growth were significantly different in the 15 min group and 30 min group respectively (P<0.05), compared with the control group. While there were no significant difference between the 60 min group and the control group (P>0.05). The results showed that 99Tcm -HL91 hypoxia imaging is an effective method of predicting effects of hyperbaric oxygen enhancement. The sensitizing effect of hyperbaric oxygen is the best within the initial 30 min then becomes decreasing gradually.The sooner combined treatments are adopted,the better effects are. (authors)