An Experimental Study Of The Impact Of Canine Spine IGRT On ADC Values And Bax/Bcl-2in Spinal Cord

Objective:Beagle spine were treated with different image guided radiation therapy programs, then MR DWI and RT-PCR detect spinal cord injury to select the ascheme, that with which spinal cord injury was lightest. Methods:36adult male beagle dogs was treated with IGRT on its7-12chest vertebrae and attachments, total dose was80Gy, which was divided to put in T7～12once a week. Conventional MRI and MR DWI were detected every two weeks until three months after the end of radiotherapy, dogs were killed at three months after the end of radiotherapy,then take out the spinal cord, HE and TUNEL staining to observed, RT-PCR to detect apoptosis-related genes Bax/Bcl-2ratio in the spinal cord. Results:②conventional MRI:At four weeks, can observe thevertebral body signal rises on T2WI image;radiotherapy vertebral signal was highest at6weeks, then the signal reduce,vertebral signal is still higher than the previous radiotherapy; However,there was non significantly abnormal be observed on T2WI radiotherapy area.②MR DWI:Before radiotherapy, the average value of36beagles thoracic cord ADC values was (0.83±0.04)×10-3mm2/s, ADC value increased after radiotherapy, the max ADC value appears six weeks after the start of radiotherapy, until three months after the end of radiotherapy, ADC value was still higher than their level before radiotherapy.③Orthogonal experiment results of ADC values:levels difference between radiation field,single dose,dose rate in spinal cord injury was statistically significant (p<0.05),there was no statistically significant between the two levels of the angle,primary effect size in the order of single dose>dose rate> radiation field; the better spinal IGRT program is the single dose of16Gy, dose rate4Gy/min,9wilds and the equal angle④levels difference between radiation field,single dose,dose rate in spinal cord injury was statistically significant (p<0.05),there was no statistically significant between the two levels of the angle,primary effect size in the order of single dose>dose rate> radiation field; the better spinal IGRT program is the single dose of16Gy, dose rate4Gy/min,9wilds and the equal angle.ConcIusion:①MR DWI is more sensitive than conventional MRI for the detection of radioactive spinal cord injury, on the basis of conventional MRI, to detect MR DWI is more conducive to detect early detection of radioactive spinal cord injury.②As the same total dose, when irradiated with different radiation schemes,radiotherapy different area of spinal cord injury.spinal IGRT optimization is feasible,the lightest spinal cord injury treated with a single dose of16Gy, dose rate4Gy/min,radiation field9wilds and the equal angle, spinal tumor radiotherapy in clinical IGRT treatment should pay attention to optimization.