Implementation and experimental validation of a robust hybrid direct aperture optimization approach for mixed-beam radiotherapy.

Heath, Emily; Mueller, Silvan; Guyer, Gian; Duetschler, Alisha; Eliçin, Olgun; Aebersold, Daniel; Fix, Michael K.; Manser, Peter (2021). Implementation and experimental validation of a robust hybrid direct aperture optimization approach for mixed-beam radiotherapy. Medical physics, 48(11), pp. 7299-7312. Wiley 10.1002/mp.15258

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PURPOSE

The objectives of the work presented in this paper were to (1) implement a robust-optimization method for deliverable mixed-beam radiotherapy (MBRT) plans within a previously developed MBRT planning framework; (2) perform an experimental validation of the delivery of robust-optimized MBRT plans; and (3) compare PTV-based and robust-optimized MBRT plans in terms of target dose robustness and organs at risk (OAR) sparing for clinical head and neck and brain patient cases.

METHODS

A robust-optimization method, which accounts for translational setup errors, was implemented within a previously developed treatment planning framework for MBRT. The framework uses a hybrid direct aperture optimization method combining column generation and simulated annealing. A robust plan was developed and then delivered to an anthropomorphic head phantom using the Developer Mode of a TrueBeam linac. Planar dose distributions were measured and compared to the planned dose. Robust-optimized and PTV-based plans were developed for three clinical patient cases consisting of two head and neck cases and one brain case. The plans were compared in terms of the robustness to 5 mm shifts of the target volume dose as well as in terms of OAR sparing.

RESULTS

Using a gamma criterion of 3%/2 mm and a dose threshold of 10%, the agreement between film measurements and dose calculations was better than 97.7% for the total plan and better than 95.5% for the electron component of the plan. For the two head and neck patient cases, the average clinical target volume (CTV) dose homogeneity index (V95%-V107%) over all the considered setup error scenarios was on average 19% lower for the PTV-based plans and it had a larger standard deviation. The robust-optimized plans achieved, on average, a 20% reduction in the OAR doses compared to the PTV-based plans. For the brain patient case, the CTV dose homogeneity index was similar for the two plans, while the OAR doses were 22% lower, on average, for the robust-optimized plan. No clear trend in terms of electron contributions was found across the three patient cases, although robust-optimized plans tended toward higher electron beam energies.

CONCLUSIONS

A framework for robust optimization of deliverable MBRT plans has been developed and validated. PTV-based MBRT were found to not be robust to setup errors, while the dose delivered by the robust-optimized plans were clinically acceptable for all considered error scenarios and had better OAR sparing. This study shows that the robust optimization is a promising alternative to conventional PTV margins for MBRT.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Clinic of Radiation Oncology > Medical Radiation Physics
04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Clinic of Radiation Oncology

UniBE Contributor:

Müller, Silvan Andreas; Guyer, Gian Mauro Carlo; Eliçin, Olgun; Aebersold, Daniel Matthias; Fix, Michael and Manser, Peter

Subjects:

600 Technology > 610 Medicine & health

ISSN:

2473-4209

Publisher:

Wiley

Language:

English

Submitter:

Beatrice Scheidegger

Date Deposited:

09 Nov 2021 15:18

Last Modified:

17 Nov 2021 00:13

Publisher DOI:

10.1002/mp.15258

PubMed ID:

34585756

Uncontrolled Keywords:

mixed-beam radiation therapy modulated electron radiation therapy robust optimization treatment planning

BORIS DOI:

10.48350/160329

URI:

https://boris.unibe.ch/id/eprint/160329

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