Experimental study of spinal image guided radiotherapy scheme optimization

English Keywords:Spinal cord  Radioactive damage  Diffusion weighted imaging  Image guided radiation therapy

English Abstract:

  【Abstract】 Objectives: To observe the effects of different spinal image guided radiation therapy(IGRT) during radiotherapy treating area of spinal cord MRI diffusion-weighted imaging(DWI) apparent diffusion coefficient(ADC), and to provide experimental basis for IGRT optimization. Methods: 36 male adult Beagles were divided according to the irradiation schemes as 4 common factors of clinical radiotherapy of the wild(A, 5, 7, 9), single dose(B, 16, 20Gy), radiation dose rate(C, 4, 6Gy/min) and irradiation angle(D, angle, unequal angle) and fractionated radiotherapy as L12(3×23) orthogonal table IGRT in T7-T12, once a week, total dose was 80Gy. Each scheme was performed in 3 dogs. ADC of radiation region of spinal cord was tested every 2 weeks before radiotherapy and after radiotherapy started, the measured data were analyzed by using statistical software SPSS 17.0, the optimum scheme was obtained by spinal IGRT. Results: Groups showed no significant difference as for the values of ADC(P>0.05) before radiotherapy. After different radiotherapy schemes, ADC values elevated; ADC value reached maximum at 6 weeks after radiotherapy. Until the third month after radiotherapy, the ADC values were still higher than the level before radiotherapy. At the same time with different schemes of spinal cord, ADC values were different(P<0.05), each time point of 5 wild field, a single dose of 20Gy radiation rate, 6Gy/min and equal angle had the maximum ADC value, and the radiation field of 9 wild, a single dose of 16Gy, dose rate of 4Gy/min and equal angle had the minimum ADC value. Statistically significant influence of irradiation field, single dose, dose rate of radiotherapy on regional spinal cord ADC value(P<0.05), and the contribution of each factor to spinal cord injury was s single dose> dose rate> radiation field. Conclusions: The radiation field, single dose, dose rate and angle will impact the size of the damage of spinal IGRT radiotherapy regions of the spinal cord, the the optimization scheme should be cautioned when choosing spinal IGRT.