| Objective: The purpose of this study was to determine whether (99m)~Tc-HL91 hypoxia imaging could detect reoxygenation of tumor after radiation therapy, and compared with (99m)~Tc-MIBI tumor imaging, We evaluated if the accumulation of (99m)~Tc-HL91 in tumors could aid in monitoring the response to radiation therapy and predicting the radiosentivities of KM mice bearing H22 tumor. Methods: 1. Contrast experiment of (99m)~Tc-HL91 and (99m)~Tc-MIBI imaging in monitoring the effect of radiation therapy: Female KM mice bearing H22 in the left thigh were divided into control group and irradiation groups. The irradiation groups were exposed to 60Co at a single dose of 15Gy. (99m)~Tc-HL91 or (99m)~Tc-MIBI planar imaging was performed at 0d, 1d, 3d and 5d post-irradiation, then the tumor and contralateral muscles were excised, weighted and the radioactivity was measured. ROI were drawn around tumor and contralateral muscles in planar images to calculate the T/NT. Differential uptake ratio (DUR) and tumor-to-muscle ratio were computed to quantitate the tracer uptake. 2. The experiment of (99m)~Tc-HL91 hypoxia imaging in predicting the radiosentivities: Female KM mice bearing H22 were all accepted (99m)~Tc-HL91 planar imaging, then they were irradiated with a single dose of 15Gy next day, the second (99m)~Tc-HL91 planer imaging was performed after 5d post-irradiation. ROI were drawn around tumor and contralateral muscles in planar images to calculate the T/NT. Comparing (99m)~Tc-HL91 uptake in tumors before (B) and after (A) their radiation, and using the value d (d= after T/NT-before T/NT), the KM mice were divided into the group which uptake (A) was higher than uptake (B) (d>0 group) and the group which uptake (A) was smaller than uptake (B) (d<0 group). 5 KM mice bearing H22 were randomly selected from the two groups and killed, then excised the tumor and cut it into sections. The tumor sections were underwent static imaging with SPECT and stained with HE to observe the tumor cells growth by microscopy, then percentages of necrosis area (PNA) was measured with a HPIAS-1000 imaging analysis system, and compared its results with DUR. The survival mice of two groups were feed as before, observed the tumor growth, measured tumor volume, and recorded the mean tumor growth rate and the average survival time. Results: 1. Results of imaging: (99m)~Tc-HL91 groups: images of tumors were clearly visible, there were obvious radioactivity gathering in all tumor images. (99m)~Tc-MIBI groups: images of tumors were identified, but they were not so clear as the (99m)~Tc-HL91 groups.2. Results of the contrast experiment of (99m)~Tc-HL91 and (99m)~Tc-MIBI imaging in monitoring the effect of radiation therapy: â‘ Sequential imaging of different time groups post-irradiation: (99m)~Tc-HL91 groups: there was no obvious difference between the tumor image of 0d group and the control group; the tumor image of 1d group reduced to thin; the tumor image of 3d group reduced to the most obviously thin; the tumor image of 5d group was clearer than the 3d group, but no significant difference was detected between it and the control group. (99m)~Tc-MIBI groups: Compared with the control group, the tumor image of different time irradiation groups reduced to thin gradually starting from 0d post-irradiation, among them the tumor image of 5d group was the most obviously thin, even appeared to weaker than the normal side. Contrasting the (99m)~Tc-HL91 and (99m)~Tc-MIBI imaging, the tumor images of (99m)~Tc-HL91 groups were obviously clearer than (99m)~Tc-MIBI groups in every time. â‘¡The changes of tracer uptake in different time groups post-irradiation: (99m)~Tc-HL91 groups: Compared with the control group, the tumor DUR of irradiation groups decreased first and then increased. Among them the tumor DUR had a little bit decrease at 0d, then the DUR decreased markedly at 1d and 3d post-irradiation, and the 3d group decreased most, but at 5d post-irradiation the DUR increased to near the control group. Analyzed the DUR of different time groups, the result showed...
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