Dose verification in radiotherapy needs daily imaging of the patient so the anatomic or position changes can be seen which may suggest replanning before the next treatment. Using standard equipment, it is not possible to obtain the daily image while the patient is on the treatment couch. The patient has to be moved to the CT scanning to obtain the daily image, which is not so practical. In addition, information from many angles for the daily image, as is required with a complete CT scanner, cannot be easily obtained due to time constraints. One possible solution to obtain the daily image would be to collect limited information while the patient is on the treatment couch. In other words, the angles for treatment planning and for imaging have to be the same. Thus, this research aims to establish a method to solve this problem. This approach uses a combination of coplanar beam positions for treatment planning of prostate cancer. A small number of beams (7 and 9) were used to explore the solution space to determine the best beam positions. The beam directions obtained for the prostate case compared well with standard criteria. The average optimization quality factors, the projection correlation values, and the dose-volume histograms were analyzed for this case. This also used two optimization methods, the gradient descent method and the simulated annealing. This process greatly reduced the overall computation time for clinical routine. The combination of treatment planning optimization and imaging optimization using projection correlation method provides the basis for powerful tools that assists the radiotherapy planner in achieving the ultimate goal: finding the treatment plan that is the best R. Widita1, L.C. Holloway2 1Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung 40132, Indonesia. 2Department of Radiation Oncology, Liverpool Hospital, Liverpool, NSW, Australia
