Plan-Class Specific Reference Quality Assurance for Volumetric Modulated Arc Therapy

  • Received : 2019.02.20
  • Accepted : 2019.02.26
  • Published : 2019.03.31


Background: There have been much efforts to develop the proper and realistic machine Quality Assurance (QA) reflecting on real Volumetric Modulated Arc Therapy (VMAT) plan. In this work we propose and test a special VMAT plan of plan-class specific (pcsr) QA, as a machine QA so that it might be a good solution to supplement weak point of present machine QA to make it more realistic for VMAT treatment. Materials and Methods: We divided human body into 5 treatment sites: brain, head and neck, chest, abdomen, and pelvis. One plan for each treatment site was selected from real VMAT cases and contours were mapped into the computational human phantom where the same plan as real VMAT plan was created and called plan-class specific reference (pcsr) QA plan. We delivered this pcsr QA plan on a daily basis over the full research period and tracked how much MLC movement and dosimetric error occurred in regular delivery. Several real patients under treatments were also tracked to test the usefulness of pcsr QA through comparisons between them. We used dynalog file viewer (DFV) and Dynalog file to analyze position and speed of individual MLC leaf. The gamma pass rate from portal dosimetry for different gamma criteria was analyzed to evaluate analyze dosimetric accuracy. Results and Discussion: The maxRMS of MLC position error for all plans were all within the tolerance limit of < 0.35 cm and the positional variation of maxPEs for both pcsr and real plans were observed very stable over the research session. Daily variations of maxRMS of MLC speed error and gamma pass rate for real VMAT plans were observed very comparable to those in their pcsr plans in good acceptable fluctuation. Conclusion: We believe that the newly proposed pcsr QA would be useful and helpful to predict the mid-term quality of real VMAT treatment delivery.


Supported by : Korea Foundation Of Nuclear Safety (KoFONS)


  1. Eric EK, et al. Task Group 142 report: Quality assurance of medical accelerators. Med. Phys. 2009;36(9):4197-4212.
  2. Choi SH, Park D, Kim KB, Kim DW, Lee J, Shin DO. Suggestion for comprehensive quality assurance of medical linear accelerator in Korea. Prog. Med. Phys. 2015;26(4):294-303.
  3. Smith K, Balter P, Duhon J, White GA Jr, Vassy DL Jr, Miller RA, Serago CF, Fairobent LA. AAPM Medical Physics Practice Guideline 8.a.: Linear accelerator performance tests. J. Appl. Clin. Med. Phys. 2017;18(4):23-39.
  4. Nederlandse Commisssie Voor Stralingsdosimetrie. Code of Practice for the Quality Assurance and Control for Volumetric Modulated Arc Therapy. Report 24 of the Netherlands Commission on Radiation Dosimetry. 2015:9-59.
  5. Ezzell GA, et al. IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119. Med. Phys. 2009;36(11):5359-5373.
  6. Rahman MM, Kim CH, Kim S. Daily based quality assurance of volumetric modulated arc therapy for the full session of treatment. J. Korean. Phys. Soc. 2018;73(7):990-1000.
  7. Choi SH, Jeong JH, Cho S, Chung MS, Huh HD, Kim WC, Cho KW, Kim CH. Construction of a High-quality Voxel Model VKHMan Using Serially Sectioned Images from Visible Korean Human Project in Korea. J NUCL SCI TECHNOL. 2008;Suppl 5:179-182.
  8. Kim CH, Jeong HJ, Bloch WE, Cho KW, Hwang SB. A polygonsurface reference Korean male phantom (PSRK-Man) and its direct implementation in Geant4 Monte Carlo simulation. Phys. Med. Biol. 2011;56:3137-3161.
  9. Dynalog File Viewer Reference Guide (P/N 100013698-05). Varian Medical Systems. Palo Alto. CA. USA. January 2011.
  10. McGarry CK, Agnew CE, Hussein M, Tsang Y, Hounsell AR, Clark CH. The use of log file analysis within VMAT audits. Br. J. Radiol. 2016;89:20150489.
  11. Kosaka K, Tanooka M, Doi H, Inoue H, Tarutani K, Suzuki H, Takada Y, Fujiwara M, Kamikonya N, Hirota S. Feasibility of estimating patient-specific dose verification results directly from linear accelerator log files in volumetric modulated arc therapy. Int. J. Medical Physics, Clinical Engineering and Radiation Oncology. 2016;5:317-328.
  12. Kim JI, Choi CH, Wu HG, Kim JH, Kim K, Park JM. Correlation analysis between 2D and quasi-3D gamma evaluations for both intensity-modulated radiation therapy and volumetric modulated arc therapy. Oncotarget. 2017;8:5449-5459.
  13. Defoor DL, Quino LAV, Mavroidis P, Papanikolaou N, Stathakis S. Anatomy-based, patient-specific VMAT QA using EPID or MLC log files. J. Appl. Clin. Med. Phys. 2015;16(3):206-215.
  14. Kerns JR, Childress N, Kry SF. A multi-institution evaluation of MLC log files and performance in IMRT delivery. Radiat. Oncol. 2014;9:176.
  15. Scaggion A, Negri A, Rossato MA, Roggio A, Simonato F, Bacco S, Paiusco M. Delivering RapidArc$^{(R)}$: A comprehensive study on accuracy and long term stability. Phys Medica. 2016;32:866-873.
  16. Park JM, Wu HG, Kim JH, Carlson JNK, Kim K. The effect of MLC speed and acceleration on the plan delivery accuracy of VMAT. Br. J. Radiol. 2015;88:20140698.
  17. Alonso JO, Galinanes AV, Pellejero SP, Azorin JFP. Evaluation of MLC performance in VMAT and dynamic IMRT by log file Analysis. Physica. Medica. 2017;33:87-94.
  18. Venencia CD, Besa P. Commissioning and quality assurance for intensitymodulated radiotherapy with dynamic multileaf collimator: Experience of the Pontificia Universidad Catolica de Chile. J. Appl. Clin. Med. Phys. 2004;5(3):37-54.
  19. Chui CS, Spirou S, LoSasso T. Testing of dynamic multileaf collimation. Med. Phys. 1996;23(5):635-641.
  20. Litzenberg DW, Moran JM, Fraass BA. Verification of dynamic and segmental IMRT delivery by dynamic log file analysis. J. Appl. Clin. Med. Phys. 2002;3(2):63-72.
  21. Nelms BE, Simon JA. A survey on planar IMRT QA analysis. J. Appl. Clin. Med. Phys. 2007;8(3):76-90.
  22. Portal Dosimetry Reference Guide (P1015288-001-A). Varian Medical Systems. Palo Alto. CA. USA. 2015.
  23. Jin J, Jesseph FB, Ahmad S. A comparison study of volumetric modulated arc therapy quality assurances using portal dosimetry and MapCHECK 2. Prog. Med. Phys. 2014;24:65-71.
  24. Hussein M, Rowshanfarzad P, Ebert MA, Nisbet A, Clark CH. A comparison of the gamma index analysis in various commercial IMRT/VMAT QA systems. Radiat. Oncol. 2013;109:370-376.
  25. Woon WA, Ravindran PB, Ekayanake P, Vikraman S, Lim YYF, Khalid J. A study on the effect of detector resolution on gamma index passing rate for VMAT and IMRT QA. J. Appl. Clin. Med. Phys. 2018;19(2):230-248.
  26. Miften M, et al. Tolerance limits and methodologies for IMRT measurement-based verification QA: Recommendations of AAPM Task Group No. 218. Med. Phys. 2018;45(4):e53-e83.
  27. Agnew A, Agnew CE, Grattan MWD, Hounsell AR, McGarry CK. Monitoring daily MLC positional errors using trajectory log files and EPID measurements for IMRT and VMAT deliveries. Phys. Med. Biol. 2014;59:N49.
  28. LoSasso T. IMRT Delivery Performance with a Varian Multileaf Collimator. Int. J. Radiation Oncology Biol. Phys. 2008;71:S85.
  29. Huq MS, et al. The report of Task Group 100 of the AAPM: Application of risk analysis methods to radiation therapy quality management. Med. Phys. 2016;43(7):4209-4262.
  30. Bortfeld T, Ullrich RS, Neve WD, Wazer DE (Editors.). Image-Guided IMRT. Verlag Berlin Heidelberg. Springer. 2006;117-128.