Program Information
Will CyberKnife M6â„¢ Multileaf Collimator Offer Advantages Over IRISâ„¢ Collimator in Prostate SBRT?
V Kathriarachchi1*, C Shang1,2 , G Evans1 , T Leventouri1 , G Kalantzis1 , (1) Florida Atlantic University, Boca Raton, FL, (2) Lynn Cancer Institute, Boca Raton Regional Hospital, Boca Raton, FL
Presentations
MO-B-BRD-5 (Monday, March 9, 2015) 10:00 AM - 12:00 PM Room: Ballroom D
Purpose: CyberKnife M6â„¢ InCiseâ„¢ Multileaf collimator (MLC) has become a new modality in practice. Its ability of forming irregularly shaped beamlets offers a potential for more efficient dose optimization and treatment delivery in comparison with that by IRISâ„¢ dodecagon beams. This study is focused on quantification of such timesaving ability in prostate SBRT with comparable dosimetry plans.
Methods:Eight prostate cancer patients were planned in MultiPlanâ„¢ 5.1.2 respectively utilizing IRIS and MLC for 36.25 Gy in 5 fractions. PTV was outlined for treating prostate only. All plans were evaluated by dose conformity index (CI), homogeneity index (HI), new conformity index (nCI) and PTV coverage. In addition, maximum doses at the bladder and rectum, calculated treatment time per fraction and planned MUs were also compared and tested for significance with the Wilcoxon test.
Results:In both IRIS and MLC plan groups, PTV Dmax was scaled to 115% while the HI was maintained at 1.15. The mean Vâ‚₀₀ was 95.42% for IRIS, and 95.36% for MLC (p=0.48); mean CI: 1.08 vs. 1.05 (p=0.09); and mean nCI: 1.13 vs. 1.11 (p=0.11). Between the groups, the differences of Dmax for the bladder and rectum were found insignificant (p=0.4). Changing from IRIS to MLC, the average treatment time per fraction was reduced by 35% (43.5 ± 2.6 min vs. 28.3 ± 1.6 min, p<0.01) and the planned MU’s were decreased by 40% (50318 ± 8976 vs. 30286 ± 2211, p<0.01).
Conclusion:This investigation demonstrated the ability of CyberKnife M6â„¢ to produce prostate SBRT plans equivalent to those using IRIS in terms of target coverage, and dose sparing of critical structures. However, a significant 35% reduction in treatment time and 40% reduction in number of MUs were achieved by replacing IRIS with MLC without dosimetric compromise in planning quality.
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