The relationship between (99m)Tc-MIBI uptakes and tumor cell death/proliferation state under irradiation

To evaluate the potential of 99mTc-MIBI imaging to monitor cellular viability of tumor post-irradiation, Ehrlich carcinoma tissues were exposed to 60Co at different single dose (0, 5, 10, 15 and 20 Gy, respectively) and the following protocol were performed at 6 h pre-irradiation and 24, 72 and 144 h post-irradiation, respectively: (1) 99mTc-MIBI planar scintigraphy was performed. Uptake of 99mTc-MIBI was expressed as differential uptake ratio (DUR) and tumor-to-non-target ratio (T/NT). (2) Apoptosis index (AI), percent of necrosis area (PNA) and Proliferating cell nuclear antigen integral absorbance (PCNA-IA)were measured. DUR and T/NT decreased with radiation dose escalating and post-irradiation time prolonging. At 24 h post-irradiation, DUR or T/NT was inversely correlated with AI or PNA (r=-0.849, -0.829, -0.883, -0.855, respectively, n=33, P<0.01) and positively correlated with PCNA-IA (r=0.789, 0.742, respectively, n=33, P<0.01). At 72 and 144 h post-irradiation, DUR or T/NT was only inversely correlated with PNA (r=-0.967, -0.956, -0.915, -0.886, respectively, n=33, P<0.01). It is suggested that 99mTc-MIBI uptake of tumor cell correlated with the changes of cell viability after irradiation. 99mTc-MIBI imaging may be a potential method to monitor tumor cell viability or therapeutic response after irradiation.