Ibarrola_1996_Br.J.Radiol_69_1026

The delay in the appearance and the extent of a lesion induced by gamma-irradiation, in rabbit iliospinalis muscles, have been evaluated in vivo by MRI. The left side rabbit muscle was irradiated with an 192Ir sealed source at two skin surface doses: 40 Gy and 80 Gy. The progress of the lesion was followed on a long-term basis (12 months) by using T2 weighted spin echo imaging. The irradiation induced lesions were detected by MRI 22 weeks after irradiation for the 40 Gy group and 17 weeks for the 80 Gy group. The atrophy of the muscle and the extent of the lesion increased as a function of the dose at the skin surface. The threshold depth dose, corresponding to the deepest border of the lesion, was calculated by using the monoexponential attenuation law. The results gave the value of 20 +/- 7 Gy for the 40 Gy group and 16 +/- 3 Gy for the 80 Gy group.