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SU‐F‐J‐148: A Collapsed Cone Algorithm Can Be Used for Quality Assurance for Monaco Treatment Plans for the MR‐Linac
Author(s) -
Hackett S,
van Asselen B,
Feist G,
Pencea S,
Akhiat H,
Wolthaus J,
Kotte A,
Bol G,
Lagendijk J,
Raaymakers B
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4956056
Subject(s) - field size , nuclear medicine , linear particle accelerator , quality assurance , radiation treatment planning , mathematics , dosimetry , field (mathematics) , physics , beam (structure) , algorithm , medicine , radiation therapy , optics , radiology , external quality assessment , pathology , pure mathematics
Purpose: Treatment plans for the MR‐linac, calculated in Monaco v5.19, include direct simulation of the effects of the 1.5T B 0 ‐field. We tested the feasibility of using a collapsed‐cone (CC) algorithm in Oncentra, which does not account for effects of the B 0 ‐field, as a fast online, independent 3D check of dose calculations. Methods: Treatment plans for six patients were generated in Monaco with a 6 MV FFF beam and the B 0 ‐field. All plans were recalculated with a CC model of the same beam. Plans for the same patients were also generated in Monaco without the B 0 ‐field. The mean dose (Dmean) and doses to 10% (D10%) and 90% (D90%) of the volume were determined, as percentages of the prescribed dose, for target volumes and OARs in each calculated dose distribution. Student's t‐tests between paired parameters from Monaco plans and corresponding CC calculations were performed. Results: Figure 1 shows an example of the difference between dose distributions calculated in Monaco, with the B 0 ‐field, and the CC algorithm. Figure 2 shows distributions of (absolute) difference between parameters for Monaco plans, with the B 0 ‐field, and CC calculations. The Dmean and D90% values for the CTVs and PTVs were significantly different, but differences in dose distributions arose predominantly at the edges of the target volumes. Inclusion of the B 0 ‐field had little effect on agreement of the Dmean values, as illustrated by Figure 3, nor on agreement of the D10% and D90% values. Conclusion: Dose distributions recalculated with a CC algorithm show good agreement with those calculated with Monaco, for plans both with and without the B 0 ‐field, indicating that the CC algorithm could be used to check online treatment planning for the MRlinac. Agreement for a wider range of treatment sites, and the feasibility of using the γ‐test as a simple pass/fail criterion, will be investigated.