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Validation of COMPASS for Pre-Treatment Patient-Specific Quality Assurance

S Sharma*, M Sairem, A Binjola, V Subramani, S Chander, All India Institute Of Medical Sciences


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Aim is to validate COMPASS 3D patient specific quality-assurance software for Monaco treatment planning system (TPS) along with Versa HD for routine quality assurance.

Methods: Beam data acquired for Monaco commissioning was used for COMPASS beam modelling. After beam modelling of COMPASS, to check fit quality, COMPASS computed curves were compared with beam data measured with radiation field analyser (RFA, IBA Blue Phantom2) by means of root mean square error (RMSE). Further to test the MLC (Agility-MLC VersaHD) modelling in COMPASS software, Elekta Express QA package contains eight QA fields as follows (i) 10x10 (ii) 20x20 (iii) 3ABUT (iv) DMLC1 (v) HIMRT (vi) HDMLC(vii) 7SegA (viii) Four L were measured with COMPASS and compared with Monaco TPS. For clinical validation of COMPASS, VMAT plans were created for downloadable contoured structure set of AAPM TG119 cases for energy 6MV using Monaco (5.11) TPS for Versa-HD linear-accelerator and verified by COMPASS (calculated and measured).

Results: RMSE for profile and PDD curve in different regions (i.e. penumbra, out of field, in field, build-up, falloff) were within 3.1% except for PDD (percentage depth dose) curves which showed 31.4% error in build-up region. In Build-up region COMPASS is creating PDD profile from zero depth whereas RFA measured PDD curve starts from -0.5cm depth (as-per Monaco requirement). For express QA check, all beams showed 2D gamma pass-rate above 95% except for FourL. FourL field Monaco versus COMPASS measured gamma pass-rate was 98.4% but Monaco versus COMPASS computed gamma pass rate was 93.4%. COMPASS computed and measured, TG119 test cases showed good agreement (within 3%) with Monaco TPS.

Conclusion: COMPASS measured (reconstructed) and computed results are in good agreement with Monaco TPS, therefore can be used for routine patient-specific quality-assurance. Special care has to be taken for superficially located targets.

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Quality Assurance, Validation, Intensity Modulation


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