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Dosimetric Comparison of Multiplan and Eclipse Planning Systems for the Stereotactic Body Radiotherapy Treatment of Prostate Cancer

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Fang Li*, c Ozhasoglu , d Clump , d Heron , r Lalonde , M Huq , University of Pittsburgh Cancer Institute, Pittsburgh, PA


SU-I-GPD-T-573 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Both Cyberknife and LINAC are currently used for the stereotactic body radiotherapy(SBRT) treatment of prostate cancer. Time for IRIS-based cyberknife treatment is long (≥1 hour) compared to conventional LINACs. The introduction of InCiseᵀᴹ MLC has made it possible to reduce the treatment time. The goal of this study is to compare plan quality generated by Multiplan and Eclipse.

Methods: Ten patients with early stage prostate cancer previously planned in Eclipse(AAA V11.0.31) and treated on Truebeam were re-planned in Multiplan(V5.3.0)., The planning CT nd contours were imported from Eclipse to Multiplan. The prescription was 36.25Gy to PTV and 40Gy to GTV in five fractions. At least 95% of the PTV and GTV were covered by the prescription isodose line, rectum V36Gy was limited to 1cc, bladder V37Gy limited to 10cc. Plans were generated by utilizing both IRIS collimator and MLC.The evaluated dosimetric parameters include PTV/GTV coverage, conformity index(CI), treatment times, total MU, number of MLC segments and organ at risk(OAR) sparing.

Results: The average CI for MLC-based Cyberknife plans is1.34 vs. 1.05 for Eclipse-based plans. With similar PTV/GTV coverage, Cyberknife MLC-based plans have much higher mean urethra dose (46.4Gy) than Eclipse based plans (39.8Gy). Rectum V100 was 4.6cc from Cyber plans vs. 1.3cc for Eclipse plans; bladder V100 was 10.7cc vs. 5.2cc; V38Gy of NVB was 55.9% vs. 28.1%. Total MU from Cyber-MLC was 16408 vs. 2795 for Eclipse; the corresponding total treatment times were 23.4 min vs. 19.4 min. Average number of MLC Segments was 66 in Cyberknife plans, and 498 in Eclipse plans. The dosimetric characteristics discussed above for IRIS-based plans are similar to those for Eclipse-based plans.

Conclusion: CK-MLC plans had fewer MU and Shorter delivery time than CK-IRIS plans, but were not able to meet the same level of conformity as CK-IRIS or Eclipse MLC.

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