Division of Medical Radiation Physics Monte Carlo for CyberKnife Incise TM MLC Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Switzerland
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Outline CyberKnife M6 System at the Inselspital Bern Commissioning Evaluation In-house independent MC dose calculation (IDC) for InCise MLC Evaluation Benchmarking of MC dose calculation for InCise MLC Summary
CyberKnife M6 System at the Inselspital Bern 2014: Installation of CyberKnife M6 System. May 2014: Start of patient treatments. July 2015: Installation of InCise MLC. August 2017: CyberKnife -11 Upgrade (requirement for the use of Monte Carlo (MC) for the InCise MLC).
CyberKnife M6 System at the Inselspital Bern
Commissioning Finite Size Pencil Beam (FSPB) algorithm must be commissioned before starting with MC commissioning. No additional data/measurements required for the MC MLC algorithm. Estimated time needed for commissioning: 3-5 days.
Commissioning - Workflow FSPB MC START Define Source Model (FWHM, Energy) Calculate TPR Calculate OCR Calculate OF ok ok Inselspital Bern: FWHM = 2.0 mm Energy = 6.3 MeV Compare calc. vs meas. TPR Compare calc. vs meas. OCR Compare calc. vs meas. OF ok FINISH nok nok nok
Evaluation In-house independent MC dose calculation (IDC) for InCise MLC Geometry model of the CyberKnife System equipped with the InCise MLC Ref: P.-H. Mackeprang et al., "Independent Monte-Carlo dose calculation for MLC based CyberKnife radiotherapy", Phys. Med. Biol. 63, 2018.
Evaluation In-house independent MC dose calculation (IDC) for InCise MLC Model is validated with measurements. Ref: P.-H. Mackeprang et al., "Independent Monte-Carlo dose calculation for MLC based CyberKnife radiotherapy", Phys. Med. Biol. 63, 2018.
Evaluation In-house independent MC dose calculation (IDC) for InCise MLC An MC-based modular IDC-Framework was successfully developed, implemented and validated against measurements and is now available to perform patient-specific QA. Ref: P.-H. Mackeprang et al., "Independent Monte-Carlo dose calculation for MLC based CyberKnife radiotherapy", Phys. Med. Biol. 63, 2018.
Evaluation Benchmarking of MC dose calculation for InCise MLC IDC - Framework COMPARISON Precision Dose distributions in water 11 rectangular MLC field sizes TPR, OCR Dose distributions in lung phantom (CIRS Thorax Phantom) Single MLC field Dose distributions in patients 2 prostate cases 7 lung cases Calculation time
Evaluation Benchmarking of MC dose calculation for InCise MLC Dose distributions in water -> OCR 115.0 x 100.1 mm 2 Framework and Precision depth = 1.5 cm Agreement between IDC 7.6 x 7.7 mm 2 within 3.1% / 1 mm. 46.2 x 46.2 mm 2 Measurement xxx IDC Framework - - - Precision
Evaluation Benchmarking of MC dose calculation for InCise MLC Dose distributions in water -> TPR Measurement xxx IDC Framework - - - Precision Agreement between IDC Framework and Precision within 2.3% / 1 mm. 115.0 x 100.1 mm 2 46.2 x 46.2 mm 2 7.6 x 7.7 mm 2
Evaluation Benchmarking of MC dose calculation for InCise MLC Dose distributions in lung phantom (CIRS Thorax Phantom) Precision IDC Framework Dose difference
Evaluation Benchmarking of MC dose calculation for InCise MLC Dose distributions in patients (lung case) Dose difference Gamma (2% / 1 mm)
Evaluation Benchmarking of MC dose calculation for InCise MLC Dose distributions in patients
Evaluation Benchmarking of MC dose calculation for InCise MLC Calculation time
Evaluation Benchmarking of MC dose calculation for InCise MLC
Summary Once the FSPB algorithm is commissioned, no additional beam data measurements are needed in order to commission the MC algorithm for the InCise MLC. An in-house independent dose calculation framework (IDC- Framework) was developed and validated against measurements. The accuracy of the MC algorithm within Precision was evaluated by comparing it with the IDC-Framework. The calculation time for a clinically reasonable dose distribution with Monte Carlo is typically below one hour.
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