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Evaluation and Validation of a Set of Dosimetric and Geometric Accuracy Tests of the Collapsed Cone Convolution Superposition Dose Calculation Algorithm for the RefleXion Treatment Planning System

R Bassalow*, D Zaks , S Maganti , Y Voronenko , RefleXion Medical, Hayward, CA


(Sunday, 7/14/2019) 4:00 PM - 4:30 PM

Room: Exhibit Hall | Forum 7

Purpose: To evaluate the dosimetric and geometric accuracy of the Collapsed Cone Convolution Superposition (CCCS) algorithm for the RefleXion treatment planning system (TPS) and validate the methodology for future RefleXion beam commissioning.

Methods: RefleXion is the first Biology Guided Radiation Therapy (BgRT) system capable of using real time positron emissions to deliver highly conformal radiation dose distributions around targets and organs at risk. The TPS uses an in-house developed CCCS algorithm for accurate dose calculation which accounts for features of the RefleXion system such as: a rapidly rotating gantry (upto 60 rpm), a stepping couch, narrow slit fields, limited by the 1 or 2 cm jaw sizes and 64 leaf binary MLC. Comparisons were done for field sizes and penumbras, for dose profiles in water and for point doses in solid water slabs of different density, at different SSDs and under a blocked field.

Results: The X and Y profiles for all tested field sizes had gamma passing rates exceeding 98.6% for 2%/2mm global gamma. The PDD for all tested field sizes and depths agreed within 1.1%. Point doses in the Cortical Bone and the Lung slabs were within 0.5%. Maximum point dose difference in solid water slabs was 1.6% at the SSD of 70 cm. The X and Y field sizes agreed within 0.5 mm and 1.4% respectively. Maximum penumbra difference for all X and Y field sizes was 0.6 mm corresponding to the smallest jaw size of 1 cm. Point doses under a blocked field for a range of transverse offsets agreed within 1.3%.

Conclusion: The RefleXion CCCS algorithm showed good agreement with the measured data, within the measurement uncertainties associated with the small field dosimetry and model parameters in the CCCS algorithm. The presented tests can be used as part of the future RefleXion beam commissioning procedure.

Funding Support, Disclosures, and Conflict of Interest: This research was funded by RefleXion Medical


Not Applicable / None Entered.


TH- External beam- photons: dose computation engines- deterministic

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