ABSTRACT
To evaluate the effects of arc geometry on lung stereotactic body radiation therapy
(SBRT) plan quality, using collision check software to select safe beam angles. Thirty
lung SBRT cases were replanned 10Gy x 5 using 4 volumetric modulated arc therapy (VMAT)
geometries: coplanar lateral (cpLAT), coplanar oblique (cpOBL), noncoplanar lateral
(ncpLAT) and noncoplanar oblique (ncpOBL). Lateral arcs spanned 180° on the affected
side whereas the 180° oblique arcs crossed midline to spare healthy tissues. Couch
angles were separated by 30° on noncoplanar plans. Clearance was verified with Radformation
CollisionCheck software. Optimization objectives were the same across the four plans
for each case. Planning target volume (PTV) coverage was set to 95% and then plans
were evaluated for dose conformity, healthy tissue doses, and monitor units. Clinically
treated plans were used to benchmark the results. The volumes of the 25%, 50% and
75% isodoses were smaller with noncoplanar than coplanar arcs. The volume of the 50%
isodose line relative to the PTV (CI50%) was as follows: clinical 3.75±0.72, cpLAT
3.39 ± 0.37, cpOBL 3.36 ± 0.34, ncpLAT 3.02 ± 0.21 and ncpOBL 3.02 ± 0.22. The Wilcoxon
signed rank test with Bonferroni correction showed p < 0.005 in all CI50% comparisons
except between the cpLat and cpObl arcs and between the ncpLat and ncpObl arcs. The
best lung sparing was achieved using ncpObl arcs, which was statistically significant
(p < 0.001) compared with the other four plans at V12.5Gy, V13.5Gy and V20Gy. Chest
wall V30Gy was significantly better using noncoplanar arcs in comparison to the other
plan types (p < 0.001). The best heart sparing at V10Gy from the ncpOBL arcs was significant
compared with the clinical and cpLat plans (p < 0.005). Arc geometry has a substantial
effect on lung SBRT plan quality. Noncoplanar arcs were superior to coplanar arcs
at compacting the dose distribution at the 25%, 50% and 75% isodose levels, thereby
reducing the dose to healthy tissues. Further healthy tissue sparing was achieved
using oblique arcs that minimize the pathlength through healthy tissues and avoid
organs at risk. The dosimetric advantages of the noncoplanar and oblique arcs require
careful beam angle selection during treatment planning to avoid collisions during
treatment, which may be facilitated by commercial software.
Keywords
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to Medical DosimetryAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- Dosimetric evaluation of heterogeneity corrections for RTOG 0236: stereotactic body radiotherapy of inoperable stage I-II non–small-cell lung cancer.Int J Radiat Oncol Biol Phys. 2009; 73: 1235-1242https://doi.org/10.1016/j.ijrobp.2008.11.019
American Cancer Society. Lung cancer guide: What you need to know. American Cancer Society. https://www.cancer.org/cancer/lung-cancer.html. Accessed November 27, 2021.
- Optimal beam arrangement for stereotactic body radiation therapy delivery in lung tumors.Acta Oncologica. 2009; 49: 219-224https://doi.org/10.3109/02841860903302897
- Volumetric modulated arc therapy for delivery of hypofractionated stereotactic lung radiotherapy: a dosimetric and treatment efficiency analysis.Radiother Oncol. 2010; 95: 153-157https://doi.org/10.1016/j.radonc.2009.12.039
Timmerman RD, Kavanagh BD. Stereotactic body radiation therapy for lung cancer. Lung Cancer:256-270; 2008. doi:10.1002/9780470696330.ch17.
- Stereotactic body radiation therapy for inoperable early stage lung cancer.JAMA. 2010; 303: 1070-1076https://doi.org/10.1001/jama.2010.261
- Safety and efficacy of a five-fraction stereotactic body radiotherapy schedule for centrally located non-small-cell lung cancer: NRG oncology/RTOG 0813 trial.J Clin Oncol. 2019; 37: 1316-1325
- A randomized phase 2 study comparing 2 stereotactic body radiation therapy schedules for medically inoperable patients with stage I peripheral non-small cell lung cancer: NRG oncology RTOG 0915 (NCCTG N0927).Int J Radiat Oncol Biol Phys. 2015; 93: 757-764https://doi.org/10.1016/j.ijrobp.2015.07.2260
- A physically meaningful relationship between R50% and PTV surface area in lung SBRT.J Appl Clin Med Phys. 2020; 21: 47-56https://doi.org/10.1002/acm2.12964
- Circumferential or sectored beam arrangements for stereotactic body radiation therapy (SBRT) of primary lung tumors: Effect on target and normal-structure dose-volume metrics.Med Dosim. 2013; 38: 407-412https://doi.org/10.1016/j.meddos.2013.05.002
- A treatment-planning comparison of three beam arrangement strategies for stereotactic body radiation therapy for centrally located lung tumors using volumetric-modulated arc therapy.J Radiat Res. 2016; 57: 273-279https://doi.org/10.1093/jrr/rrv105
- (J. Dosimetric comparison of two arc-based stereotactic body radiotherapy techniques for early-stage lung cancer.Med Dosim. 2015; 40: 76-81https://doi.org/10.1016/j.meddos.2014.10.004
- Collision risk mitigation of Varian Truebeam linear accelerator with supplemental live-view cameras.Pract Radiat Oncol. 2019; 9: e103-e109https://doi.org/10.1016/j.prro.2018.07.001
- Collision indicator charts for gantry-couch position combinations for Varian Linacs.J Appl Clin Med Phys. 2011; 12: 16-22https://doi.org/10.1120/jacmp.v12i3.3405
- The development and verification of a highly accurate collision prediction model for automated noncoplanar plan delivery.Med Phys. 2015; 42: 6457-6467https://doi.org/10.1118/1.4932631
Lung Cancer Atlases, templates, & tools. NRG. https://www.nrgoncology.org/ciro-lung. Accessed December 12, 2021.
- Fine-tuning the normal tissue objective in eclipse for lung stereotactic body radiation therapy.Med Dosim. 2018; 43: 344-350https://doi.org/10.1016/j.meddos.2017.11.004
Article info
Publication history
Published online: February 06, 2023
Accepted:
January 10,
2023
Received in revised form:
December 5,
2022
Received:
July 8,
2022
Identification
Copyright
© 2023 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.
