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Impact of Different Treatment Planning Systems On Modulation Complexity for Prostate Volumetric Modulated Arc Therapy

M Itano1*, K Motegi2 , S Kanai3 , S Shirasaki4 , H Tachibana5 , (1) ,,,(2) National Cancer Center, Kashiwa, Chiba, (3) Funabashi Municipal Medical Center, Funabashi, Chiba, (4) Funabashi Municipal Medical Center, Funabashi, Chiba, (5) National Cancer Center Hospital East, Kashiwa,


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: Modulation complexity depends on optimization and MLC motion calculation. We evaluated the impact of difference between Eclipse (EC, Varian Medical Systems, Palo Alto, USA) and RayStation (RS, RaySearch Laboratories, Stockholm, Sweden) planning systems on modulation complexity for prostate volumetric modulated arc therapy (VMAT).

Methods: First, CT images and contouring data for five prostate cancer patients were collected and two VMAT plans for each patient were generated using EC and RS to achieve same plan goal of dose volume constraints for targets and organs at risk (OARs). Subsequently, dose distribution and the modulation complexity computed using the modulation complexity score (MCS) were evaluated for the two plans.

Results: The mean numbers of the control points (CP) were 356 and 198 for EC and RS respectively. Mean MCS values were 0.168 ± 0.027 and 0.205 ± 0.027 for EC and RS respectively. Four plans of RS show higher MCS than EC. In the comparisons of dose distribution, EC shows better OAR sparing than RS while keeping similar target coverage. Gamma pass ratio of all plans in EC achieved > 98%.

Conclusion: EC may generate more complex plans for shape and size of MLC aperture sequence to generate better dose distribution while accuracy of dose delivery is sufficient.


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