Abstract
Linac parameters such as the multi-leaf collimator (MLC) position and jaw position, cumulative monitor units (MUs), and the corresponding gantry angle were recorded during the clinical delivery of volumetric modulated arc therapy for prostate, lung, and head/neck cancer patients. Then, linac parameters were converted into the beam-data format used in the treatment planning system, and the dose distribution was reconstructed. The dose-volume histogram and the dose difference (DD) were compared with the corresponding values in the treatment plan. A reproducible error of in-treatment linac parameters was observed when a sudden change of beam intensity or MLC/jaw speed occurred. The maximum cumulative MU error was more than 4 MU for lung cancer cases, and the maximum MLC position exceeded 5 mm for prostate and head/neck cancer patients. However, these errors were quickly compensated for at the next control point. All treatments analyzed in the present study were delivered within 0.4 % accuracy at the planning target volume. The cumulative dose agreed with that of the plan within 3 % of the prescribed dose. The 1 % DD was 93.9, 99.9, and 93.4 % of the prescription dose for prostate, lung, and head/neck cancer patients, respectively.
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References
Otto K. Volumetric modulated arc therapy: IMRT in a single gantry arc. Med Phys. 2008;35:310–7.
Bedford JL, Nordmark HV, MacNair HA, et al. Treatment of lung cancer using volumetric modulated arc therapy and image guidance: a case study. Acta Oncol. 2008;47:1438–43.
Bedford JL, Warrington AP. Commissioning of volumetric modulated arc therapy (VMAT). Int J Radiat Oncol Biol Phys. 2009;73:537–45.
Korrenman S, Medin J, Kristoffersen FK. Dosimetric verification of RapidArc treatment delivery. Acta Oncol. 2009;48:185–91.
Schreibmann E, Dhabaan A, Elder E, et al. Patient-specific quality assurance method for VMAT treatment delivery. Med Phys. 2009;36:4530–5.
Stell AM, Li GL, Zeidan OA, et al. An extensive log-file analysis of step-and-shoot intensity modulated radiation therapy segment delivery errors. Med Phys. 2004;31:1593–602.
Lee L, Le QT, Xing L. Retrospective IMRT dose reconstruction based on cone-beam CT and MLC log-file. Int J Radiat Oncol Biol Phys. 2008;70:634–44.
Okumura M, Obata Y, Shimomura K, et al. The effect of gantry and collimator angles on leaf limited velocity and position in dynamic multileaf collimator intensity-modulated radiation therapy. Phys Med Biol. 2010;55:3101–13.
Xing L, Lin Z, Donaldson SS, et al. Dosimetric effects of patient displacement and collimator and gantry angle misalignment on intensity modulated radiation therapy. Radiother Oncol. 2000;56:97–108.
Haga A, Nakagawa K, Shiraishi K, et al. Quality assurance of volumetric modulated arc therapy using Elekta Synergy. Acta Oncol. 2009;48:1193–7.
Mans A, Remeijer P, Olaciregui-Ruiz I, et al. 3D Dosimetric verification of volumetric-modulated arc therapy by portal dosimetry. Radiother Oncol. 2010;94:181–7.
Mans A, Wendling M, McDermott LN. Catching errors with in vivo EPID dosimetry. Med Phys. 2010;37:2638–44.
Hu W, Ye J, Wang J, et al. Use of kilovoltage X-ray volume imaging in patient dose calculation for head-and-neck and partial brain radiation therapy. Radiat Oncol. 2010;5:29.
Ding GX, Duggan DM, Coffey CW, et al. A study on adaptive IMRT treatment planning using kV cone-beam CT. Radiother Oncol. 2007;85:116–25.
Yang Y, Schreibmann E, Li T, et al. Evaluation of on-board kV cone beam CT (CBCT)-based dose calculation. Phys Med Biol. 2007;52:685–705.
van Zijtveld M, Dirkx M, Heijmen B. Correction of conebeam CT values using a planning CT for derivation of the “dose of the day”. Radiother Oncol. 2007;85:195–200.
Richter A, Hu Q, Steglich D, et al. Investigation of the usability of conebeam CT data sets for dose calculation. Radiat Oncol. 2008;3:42.
Guan H, Dong H. Dose calculation accuracy using cone-beam CT (CBCT) for pelvic adaptive radiotherapy. Phys Med Biol. 2009;54:6239–50.
Morin O, Chen J, Aubin M, et al. Dose calculation using megavoltage cone-beam CT. Int J Radiat Oncol Biol Phys. 2007;67:1201–10.
Qian J, Lee L, Liu W, et al. Dose reconstruction for volumetric modulated arc therapy (VMAT) using cone-beam CT and dynamic log files. Phys Med Biol. 2010;55:3597–610.
Sakumi A, Haga A, Kida S, et al. First in-situ dose calculation report using in-treatment kilovoltage cone-beam CT and in-treatment linac parameters during volumetric modulated arc therapy. J Radiat Res. 2011;52:536–7.
Bertelsen A, Lorenzen EL, Brink C. Validation of a new control system for Elekta accelerators facilitating continuously variable dose rate. Med Phys. 2011;38:4802–10.
Acknowledgments
This work was supported by JSPS KAKENHI 22791176. A. H. wishes to thank Dr. Grant Jackson (Elekta K.K.) for his advice regarding the use of iCom in acquiring log data during treatment. K. N. received research funding from Elekta K.K.
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The authors declare that they have no conflict of interest.
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Haga, A., Sakumi, A., Okano, Y. et al. Dose verification of volumetric modulated arc therapy (VMAT) by use of in-treatment linac parameters. Radiol Phys Technol 6, 335–342 (2013). https://doi.org/10.1007/s12194-013-0205-6
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DOI: https://doi.org/10.1007/s12194-013-0205-6