New method to optimize protection of the organs at risk allows to regain coverage and homogeneity in the Planning Target Volume

Alfonso Quintero Quintero; Edwin Rozo Albarracin

doi:10.29384/rbfm.2023.v17.19849001701

Authors

Alfonso Quintero Quintero Medical Physicist https://orcid.org/0000-0002-8312-4601
Edwin Rozo Albarracin Medical Physicist https://orcid.org/0009-0005-3762-599X

DOI:

https://doi.org/10.29384/rbfm.2023.v17.19849001701

Keywords:

VMAT, ICRU 83, homogeneity index, dose coverage, OARs protection

Abstract

The construction of auxiliary structures within the Planning Target Volume (PTV) is proposed as a method to recover coverage and homogeneity, and to optimize the protection of the organs at risk (OARs) in radiotherapy treatment plans. To this purpose, it was performed the Volumetric Modulated Arc Therapy (VMAT) treatment planning of the “mock prostate” test. Three plans were optimized in the EclipseTM treatment planning system. In plan 1 (P1), it was defined an initial objective function only for the PTV. Then, the dose received by the OARs was restricted, guaranteeing the PTV level of coverage. Plan 2 (P2) used the same dose-volume objectives for the PTV as in P1, but more restrictive dose constraints were set for the OARs. From the dose distribution obtained in P2, it was built auxiliary subvolumes contained within the PTV to regain coverage and homogeneity in plan 3 (P3). To this end, it was compared the coverage (D95%), the Homogeneity Index (HI) and dose-volume histogram for the PTV, and OARs dose sparing for rectum and Bladder. P1 and P3 resulted in similar PTV coverage and HI values, however, the OARs received a lower dose in P3. Despite in P2 it was achieved a higher OARs protection, the PTV coverage and HI were considerably reduced. In this sense P3 allowed to reach the best balance between coverage, HI, and OARs protection. As a consequence of these results, it has been shown that the introduction of auxiliary structures as target subvolumes constitute a powerful and easy to implement tool in the treatment planning optimization process and can be employed in any pathology that requires VMAT.

Downloads

Download data is not yet available.

References

Otto K. Volumetric modulated arc therapy: IMRT in a single gantry arc. Medical physics. 2008;35(1):310-317. https://doi.org/10.1118/1.2818738.

Teoh M, Clark C, Wood K, Whitaker S, Nisbet A. Volumetric modulated arc therapy: a review of current literature and clinical use in practice. The British Journal of Radiology. 2011;84(1007);967-996. https://doi.org/10.1259/bjr/22373346.

Macchia G, Deodato F, Cilla S, Cammelli S, Guido A, Ferioli M, et al. Volumetric modulated arc therapy for treatment of solid tumors: current insights. Onco Targets Ther. 2017;10:3755-3772. https://doi.org/10.2147/OTT.S113119.

Liu H, Sintay B, Pearman K, Shang Q, Hayes L, Maurer J, et al. Comparison of the progressive resolution optimizer and photon optimizer in VMAT optimization for stereotactic treatments. Journal of applied clinical medical physics. 2018;19(4):155-162. https://doi.org/10.1002/acm2.12355.

ICRU Report 83: Prescribing, Recording, and Reporting Photon-Beam Intensity-Modulated Therapy (IMRT). Journal of the International Commission on Radiation Units and Measurements. 2010;10(1):1-106. https://doi.org/10.1093/jicru_ndq002.

Hussein M, Heijmen BJ, Verellen D, Nisbet A. Automation in intensity modulated radiotherapy treatment planning-a review of recent innovations. The British Journal of Radiology. 2018;91(1092):201802. https://doi.org/10.1259/bjr.20180270.

Creemers IH, Kusters JM, van Kollenburg PG, Bouwmans LC, Schinagl DA, Bussink J. Comparison of dose metrics between automated and manual radiotherapy planning for advanced stage non-small cell lung cancer with volumetric modulated arc therapy, Physics and Imaging in Radiation Oncology. 2019;9:92-96. https://doi.org/10.1016/j.phro.2019.03.003.

Nelms BE, Robinson G, Markham J, Velasco K, Boyd S, Narayan S, et al. Variation in external beam treatment plan quality: an inter-institutional study of planners and planning systems. Practical radiation oncology 2012;2(4):296-305. https://doi.org/10.1016/j.prro.2011.11.012.

Ezzell GA, Burmeister JW, Dogan N, LoSasso TJ, Mechalakos JG, Mihailidis D, et al. IMRT commissioning: multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119. Medical physics. 2009;36(11):5359–5373. https://doi.org/10.1118/1.3238104.