Abstract:
This study aimed at finding an optimal approach for the distribution of the standard radiation dose to the prostate gland and in the same time the reduction of the radiation dose to the rectum , urinary bladder and skin , by using a medium energy (1.25 MV) cobalt -60 machine , alongside with the use of CT images of 55 patients undergoing radiotherapy planning for the distribution of the radiation dose via several fields (3,5,7) , in order to find out an agreed upon protocol and a standard method to substitute the images in the future (whenever they are not feasible), during the planning the study concluded that the use of five radiation fields with wedge angles 45ە for oblique fields (anterior , right anterior oblique, left anterior oblique , right posterior oblique and left posterior oblique ) through 0, 60 , 300, 120,240 degrees respectively, can help provide a radiation dose with ratio of 98% to the prostate gland with a reduced dose of 76.7%,96% and 71% to the rectum , urinary bladder and skin respectively. The study also concluded that a standard planning of CT images could be used as a substitute to the manual contour of the mean dimensions (AP separation 23.4 cm, lateral separation 41.4cm), to replace any other planning within the range 15.2cm to 26.1cm for the AP separation and the range 30cm to 48.4 cm for the lateral separation. This approach will cancel the need for the CT scans of any patient within this range, as there is no significant difference when comparing the distribution of radiation dose through the application of a contour depending on CT scans for each patient with the application of the standard contour derived from the CT scans.
