Vol. 8, 2023



Angela Dameska, Milena Teodosievska Dilindarski, Dushko Lukarski

Pages: 131-135

DOI: 10.37392/RapProc.2023.27

Volumetric modulated arc therapy (VMAT) is the next step in the improvement of the dynamic intensity modulated radiotherapy by improving the delivery efficiency and reducing the treatment time. In this study we have evaluated the delivery accuracy of different types of VMAT plans by performing an end-to-end test using the CIRS IMRT Thorax 002LFC phantom on two different radiotherapy units, a Varian iX Clinac and a Halcyon unit. We have created 10 different VMAT plans and measured the dose in different points according to a modified IAEA CRP E24017 protocol. For the measurement points representing the target volumes we have found that using two or three arcs gives acceptable results, but for single arc treatments the results were suboptimal. For low-dose regions, field size was found to have a more pronounced effect especially on the iX unit, with larger fields leading to slightly reduced accuracy. Inaccuracies are usually highest where the inhomogeneity of the body is greatest, such as the points representing the lungs and the spinal cord regions, where the computational algorithms themselves also contribute to the overall inaccuracy. In conclusion, the end-to-end test showed that the plans are clinically acceptable, but the recommendations for these particular machines would be not to use single arc treatments and to consider algorithm inaccuracies in regions of greater inhomogeneity during the treatment planning process.
  1. K. Otto, “Volumetric modulated arc therapy: IMRT in a single gantry arc,” Med. Phys., vol. 35, no. 1, pp. 310 – 317, Jan. 2008.
    DOI: 10.1118/1.2818738
    PMid: 18293586
  2. E. Vanetti et al., “Volumetric modulated arc radiotherapy for carcinomas of the oro-pharynx, hypo-pharynx and larynx: a treatment planning comparison with fixed field IMRT,” Radiother. Oncol., vol. 92, no. 1, pp. 111 – 117, Jul. 2009.
    DOI: 10.1016/j.radonc.2008.12.008
    PMid: 19157609
  3. J. Gomez-Millan Barrachina et al., “Potential advantages of volumetric arc therapy in head and neck cancer,” Head & Neck, vol. 37, no. 6, pp. 909 – 914, Jun. 2015.
    DOI: 10.1002/hed.23685
    PMid: 24623665
  4. U. Akbas et al., “Nasopharyngeal carcinoma radiotherapy with hybrid technique,” Med. Dosim., vol. 44, no. 3, pp. 251 – 257, Sep. 2019.
    DOI: 10.1016/j.meddos.2018.09.003
    PMid: 30366620
  5. N. Zhao et al., “A hybrid IMRT/VMAT technique for the treatment of nasopharyngeal cancer,” Biomed Res. Int., vol. 2015, 940102, 2015.
    DOI: 10.1155/2015/940102
    PMid: 25688371
    PMCid: PMC4320861
  6. X. Jin et al., “CBCT-based volumetric and dosimetric variation evaluation of volumetric modulated arc radiotherapy in the treatment of nasopharyngeal cancer patients,” Radiat. Oncol., vol. 8, no. 1, 279, Dec. 2013.
    DOI: 10.1186/1748-717X-8-279
    PMid: 24289312
    PMCid: PMC4222038
  7. J. M. Park, H. G. Wu, H. J. Kim, C. H. Choi, J. I. Kim, “Comparison of treatment plans between IMRT with MR-linac and VMAT for lung SABR,” Radiat. Oncol., vol. 14, no. 1, 105, Jun. 2019.
    DOI: 10.1186/s13014-019-1314-0
    PMid: 31196120
    PMCid: PMC6567463
  8. E. E. Klein et al., “Task Group 142 report: Quality assurance of medical accelerators,” Med. Phys., vol. 36, no. 9, pp. 4197 – 4212, Sep. 2009.
    DOI: 10.1118/1.3190392
    PMid: 19810494
  9. J. Hanley et al., “AAPM Task Group 198 Report: An implementation guide for TG 142 quality assurance of medical accelerators,” Med. Phys., vol. 48, no. 10, pp. e830 – e885, Oct. 2021.
    DOI: 10.1002/mp.14992
    PMid: 34036590
  10. M. Miften et al., “Tolerance limits and methodologies for IMRT measurement-based verification QA: Recommendations of AAPM Task Group No. 218,” Med. Phys., vol. 45, no. 4, pp. e53 – e83, Apr. 2018.
    DOI: 10.1002/mp.12810
    PMid: 29443390
  11. T. C. Zhu et al., “Report of AAPM Task Group 219 on independent calculation-based dose/MU verification for IMRT,” Med. Phys., vol. 48, no. 10, pp. e808 – e829, Oct. 2021.
    DOI: 10.1002/mp.15069
    PMid: 34213772
  12. P. Kazantsev et al., “IAEA methodology for on-site end-to-end IMRT/VMAT audits an international pilot study,” Acta Oncol., vol. 59, no. 2, pp. 141 – 148, Feb. 2020.
    DOI: 10.1080/0284186X.2019.1685128
    PMid: 31746249
  13. P. Wesolowska et al., “Testing the methodology for a dosimetric end-to-end audit of IMRT/VMAT: results of IAEA multicentre and national studies,” Acta Oncol., vol. 58, no. 12, pp. 1731 – 1739, Dec. 2019.
    DOI: 10.1080/0284186X.2019.1648859
    PMid: 31423867
  14. T. Santos et al., “IMRT national audit in Portugal,” Phys. Med., vol. 65, pp. 128 – 136, Sep. 2019.
    DOI: 10.1016/j.ejmp.2019.08.013
    PMid: 31450123
  15. L. Tuntipumiamorn et al., “Multi-institutional evaluation using the end-to-end test for implementation of dynamic techniques of radiation therapy in Thailand,” Rep. Pract. Oncol. Radiother., vol. 24, no. 1, pp. 124 – 132, Jan-Feb. 2019.
    DOI: 10.1016/j.rpor.2018.11.005
    PMid: 30532660
    PMCid: PMC6265520
  16. H. Schiefer et al., “The Swiss IMRT dosimetry intercomparison using a thorax phantom,” Med. Phys.,nvol. 37, no. 8, pp. 4424 – 4431, Aug. 2010.
    DOI: 10.1118/1.3460795
    PMid: 20879601
  17. D. S. Radojcic et al., “Experimental validation of Monte Carlo based treatment planning system in bone density equivalent media,” Radiol. Oncol., vol. 54, no. 4, pp. 495 – 504, Sep. 2020.
    DOI: 10.2478/raon-2020-0051
    PMid: 32936784
    PMCid: PMC7585341
  18. E. Gershkevitsh et al., “Dosimetric inter-institutional comparison in European radiotherapy centres: Results of IAEA supported treatment planning system audit,” Acta Oncol., vol. 53, no. 5, pp. 628 – 636, May 2014.
    DOI: 10.3109/0284186X.2013.840742
    PMid: 24164104