Abstract Objective To study the real-time dose verification with 2D array ion chamber array in volumetric modulated arc therapy (VMAT) with a 2D array ion chamber array. Methods The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source-detector distance (SDD) was 140 cm. 8 mm RW3 solid water was added to the 2D array to improve the signal noise ratio. Patient plans for esophageal, prostate and liver cancers were selected to be delivered on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real-time patient transit dose measurements were performed at each fraction. Dose distributions were evaluated using gamma index criteria of 3 mm DTA and 3% dose difference referred to the first time result. Results The gamma index pass rate in the Cheese phantom were about 98%;the gamma index pass rate for esophageal, prostate and liver cancer patient were about 92%, 92% and 94%, respectively. Gamma pass rate for all single fraction were more than 90%. Conclusions The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.
Corresponding Authors:
Wang Yunlai, Department of Radiation Oncology, PLA General Hospital, Beijing 100853, China;Email:nanyangwang@163.com
Cite this article:
Liu Xiao*,Wang Yunlai,Ju Zhongjian et al. Real-time patient transit dose verification of volumetric modulated arc therapy by a 2D ionization chamber array[J]. Chinese Journal of Radiation Oncology, 2015, 24(4): 462-465.
Liu Xiao*,Wang Yunlai,Ju Zhongjian et al. Real-time patient transit dose verification of volumetric modulated arc therapy by a 2D ionization chamber array[J]. Chinese Journal of Radiation Oncology, 2015, 24(4): 462-465.
[1] Bedford J,Warrington A. Commissioning of volumetric modulated arc therapy VMAT[J]. Int J Radiat Oncol Biol Phys,2009,73(2):537-545.DOI:10.1016/j.ijrobp.2008.08.055. [2] Korreman S, Medin J, and Kjaer-Kristoffersen F. Dosimetric verification of RapidArc treatment delivery[J]. Acta Oncol,2009,48(2):185-191.DOI:10.1080/02841860802287116. [3] Low DA, Harms WB, Mutic S, et al. A technique for the quantitative evaluation of dose distributions[J]. Med Phys,1998,25(5):656-661. [4] Low DA,Dempsey JF. Evaluation of the gamma dose distribution comparison method[J].Med Phys,2003,30(90):2455-2464. [5] Park JY, Lee JW, Choi KS,et al. Development of a novel quality assurance system based on rolled-up and rolled-out radiochromic films in volumetric modulated arc therapy[J]. Med Phys,2011,38(12):6688-6696.DOI:10.1118/1.3659706. [6] Tanooka M, Doi H, Miura H, et al. Three-dimensional radiochromic film dosimetry for volumetric modulated arc therapy using a spiral water phantom[J].J Radiat Res,2013,54(6):1153-1159.DOI:10.1093/jrr/rrt059. [7] Syamkumar SA, Padmanabhan S, Sukumar P, et al. Characterization of responses of 2D array seven29 detector and its combined use with octavius phantom for the patient-specific quality assurance in rapidarc treatment delivery[J].Med Dosim,2012,37(1):53-60.DOI:10.1016/j.meddos.2010.12.013. [8] Boggula R, Birkner M, Lohr F,et al. Evaluation of a 2D detector array for patient-specific VMAT QA with different setups[J].Phys Med Biol,2011,56(22):7163-7177.DOI:10.1088/0031-9155/56/22/011. [9] Gloi AM, Buchanan RE, Zuge CL, et al. RapidArc quality assurance through MapCHECK[J]. J Appl Clin Med Phys,2011,12(2):39-47. [10] Feygelman V, Zhang G, Stevens C, et al. Evaluation of a new VMAT QA device, or the"X" and"O" array geometries[J]. J Appl Clin Med Phy,2011,12(2):146-168. [11] Fogliata A, Clivio A, Fenoglietto P, et al. Quality assurance of RapidArc in clinical practice using portal dosimetry[J]. Br J Radiol,2011,84(1002):534-545.DOI:10.1259/bjr/72327299. [12] Mans A, Remeijer P, Olaciregui-Ruiz I, et al. 3D Dosimetric verification of volumetric-modulated arc therapy by portal dosimetry[J].Radiother Oncol, 2010, 94(2):181-187.DOI:10.1016/j.radonc.2009.12.020. [13] Rowshanfarzad P, Sabet M, O’Connor DJ, et al. Detection and correction for EPID and gantry sag during arc delivery using cine EPID imaging[J]. Med Phys,2012,39(2):623-635.DOI:10.1118/1.3673958. [14] Du W, Gao S. Measuring the wobble of radiation field centers during gantry rotation and collimator movement on a linear accelerator[J]. Med Phys,2011,38(8):4575-4578.
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