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Dosimetric Evaluation of Bilateral Hip Prostheses for RT Plan of Prostate with Different Algorithms and Calculation Conditions

S Pokharel

S Pokharel1*, S Rana2 , (1) 21st Century Oncology, Naples, FL, (2) Miami Cancer Institute , Miami, FL


SU-I-GPD-T-436 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To evaluate the dosimetric effect of bilateral hip prostheses in RT treatment plan of prostate

Methods: A prostate case (50.4 Gy, 28 fractions) with bilateral hip prostheses has been chosen for this study. All relevant structures including prostheses and artifacts were contoured and assigned appropriate densities. A five fields IMRT plan and a RA plan with two full arcs were designed. The first plan avoided beam entry and exit through prostheses whereas second did not. Both plans were optimized with same set of objectives and calculated using Eclipse AAA and AcurosXB algorithms (versions 11.0.13). Plans were normalized such that 95% target volume received 100% of prescription dose. Plans were then optimized and recalculated with inhomogeneity turned off and with the change of prosthetic material from Titanium to stainless steel.

Results: There was no significant difference in PTV (Minimum, maximum and mean)dose among all the plans.There was no significant difference in mean dose of rectum, bladder, penile bulb, normal tissue and V50 of rectum and bladder . However, V30 for both rectum and bladder were significantly lower for RA plans compared to five fields IMRT. There were minor changes in all dosimetric indices and number of MUs for five fields IMRT with the change in prosthetic material. However, there was a significant increase in V30 for both rectum and bladder with the change of material from Titanium to stainless steel for RA plans.

Conclusion: Insignificant changes were observed with five fields IMRT plan for both change in material and inhomogeneity. However, RA plans seem to have significant difference from the choice of materials and inhomogeneity. Specially, AAA seems to have more changes in number of MUs than AcurosXB. It is advisable to use full RA plan with AcurosXB to achieve sufficient target coverage with lower dose to the critical structures.

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