Physical Evaluation and Verification of Different Radiotherapy Techniques for Prostate Cancer
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Abstract
Introduction: In radiotherapy, cancer prostate can be treated with different advanced radiotherapy techniques (3DCRT, IMRT, and RapidArc). Each of these techniques can be achieved with different plans. To select the optimum plan in these techniques physical evaluation and dose verification should be performed for each plan.
Material and Methods: Computed tomography scans of 18 patients who had completed 3DCRT for intermediate risk of prostate cancer were replanned using two RapidArc plans, four IMRT plans and two 3DCRT plans. Calculated doses to planning target volume (PTV) and organs at risk (OAR) were compared between all plans in physical evaluation (dose homogeneity index (HI), target coverage and conformity indices (PITV, TCI, CI, and CN), dose gradient (GI and GM), critical organ scoring indices (COSI and MCOSI) and an index for overall plan quality factor (QF)). Dose distributions of 8 plans were verified using 2D array in octavious 4D phantom.
Results: by using physical evaluation HI values indicated that 3DCRT has the best dose homogeneity. Calculated values of PITV, TCI, CI, and CN showed that RapidArc produce better dose conformity than other technique. GM and GI values displayed that, RapidArc gives better dose gradient than IMRT and 3DCRT. COSI values displayed that the RapidArc and 3DCRT is the best sparing high dose to OAR. MCOSI values displayed that the RapidArc and 3DCRT is the best sparing from low dose to high dose to OAR. So, none of these physical evaluation indices solely allowed ranking the plans. Calculating QF index allowed ranking the plans. The QF value of Rapid Arc plans give the highest values.
Conclusion: in comparing between 3 technique (3DCRT.IMRT and Rapid Arc) the Physical evaluation of treatment plans can't be achieved by calculating any of the physical evaluation quantities solely. This issue can be solved by calculating treatment plan quality factor. In advanced radiotherapy techniques, in addition to the physical evaluation, dose verification should be performed and analysed.