AbstractObjective To investigate how to use the ArcCHECK to complete synchronization test in helical tomotherapy (HT). Methods According to the synchronization test suggested by AAPM TG148, three aspects should be tested.(1) Gantry angle consistency:ArcCHECK device in the long axis was perpendicular to the rotation plane using virtual isocenter positioning. A delivery sequence was defined with a slice width of 2.5 cm, a pitch of 0.1, and a minimum of 40 rotations. The control sinogram was set to open the middle two leaves (No. 32 and 33) at projections centered at 0°, 120°, and 240°.(2) Couch speed uniformity:The ArcCHECK was fixed on the treatment couch by positioning the long axis in the movement direction of couch. An irradiation was done with a static gantry in the 0° position, the collimation set to 1 cm, and all MLC leaves open. A couch travel distance of 20 cm was programmed using a clinically common couch speed (0.3-0.5 mm/s for 2.5 cm treatment slice width) in the course of irradiation.(3) Synchronization of couch translation and gantry rotation:In this test, a rotational irradiation was used with the nominal 1.0 cm beam and a pitch of 1 for 13 rotations. The control sonogram was set to open all the leaves for a half rotation on the second, seventh, and twelfth rotations. The initial collected data were used as the baseline data of parameters. The subsequent measurements were compared with the baseline data using the point to point absolute dose pass rates of DD (dose difference, 1%). Results The gantry angle consistency could check the correct initial angles at the beginning of the treatment and the ability to reproduce the projection every rotation. There were six parallel and straight high-dose regions in ArcCHECK software. In the couch speed uniformity test, the relative dose in the long axis in the high-dose regions was changed less than 2%. In the synchronization test of couch translation and gantry rotation, three parallel high-dose regions with the same separation spacing were present in the ArcCHECK software. The synchronization tests were done twenty-eight times in the second, seventh, and twelfth irradiation rotations and the average pass rates were 93.2%±1.5%, 93.7%±1.1%, and 93.5%±1.3%, respectively. Conclusions The ArcCHECK device is a suitable alternative method for performing the synchronization test in HT due to its lower workload and costs compared with the film.
Yu Lang,Yang Bo,Liu Xia et al. Application of semiconductor matrix in synchronization test in helical tomotherapy[J]. Chinese Journal of Radiation Oncology, 2017, 26(12): 1430-1433.
Yu Lang,Yang Bo,Liu Xia et al. Application of semiconductor matrix in synchronization test in helical tomotherapy[J]. Chinese Journal of Radiation Oncology, 2017, 26(12): 1430-1433.
[1] Van Dyk J.The modern technology of radiation oncology:a compendium for medical physicists and radiation oncologists[M].Madison,WI:Medical Physics Publishing,1999. [2] 于浪,杨波,庞廷田,等.应用二维电离室矩阵对后装剂量分布的验证[J].协和医学杂志,2013,4(4):408-412.DOI:10.3969/j.issn.1674-9081.2013.04.013. Yu L,Yang B,Pang TT,et al. Use of two-dimensional ionization chamber array on brachytherapy dose verification[J].Med J Peking Union Med Coll Hosp,2013,4(4):408-412.DOI:10.3969/j.issn.1674-9081.2013.04.013. [3] 于浪,杨波,李楠,等.应用二维电离室矩阵进行虚拟楔形板物理参数检测[J].中华放射肿瘤学杂志,2015,24(3):340-342.DOI:10.3760/cma.j.issn.1004-4221.2015.03.027. Yu L,Yang B,Li N,et al. Dosimetry verification of virtual wedge using a two-dimensional ionisation chamber array[J].Chin J Radiat Oncol,2015,24(3):340-342.DOI:10.3760/cma.j.issn.1004-4221.2015.03.027. [4] Mackie TR,Holmes T,Swerdloff S,et al. Tomotherapy:a new concept for the delivery of dynamic conformal radiotherapy[J].Med Phys,1993,20(6):1709-1719.DOI:10.1118/1.596958. [5] Balog J,Holmes T,Vaden R.A helical tomotherapy dynamic quality assurance[J].Med Phys,2006,33(10):3939-3950.DOI:10.1118/1.2351952. [6] Langen KM,Papanikolaou N,Balog J,et al. QA for helical tomotherapy:report of the AAPM task group 148[J].Med Phys,2010,37(9):4817-4853.DOI:10.1118/1.3462971. [7] Li GJ,Zhang YJ,Jiang XQ,et al. Evaluation of the ArcCHECK QA system for IMRT and VMAT verification[J].Phys Med,2013,29(3):295-303.DOI:10.1016/j.ejmp.2012.04.005. [8] 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.DOI:10.1118/1.598248. [9] Li G, Zhang Y, Jiang X, et al. Evaluation of the ArcCHECK QA system for IMRT and VMAT verification[J]. Physica medica:PM:an international journal devoted to the applications of physics to medicine and biology:official journal of the Italian Association of Biomedical Physics (AIFB), 2013, 29(3):295. [10] Fenwick JD,Tomé WA,Jaradat HA,et al. Quality assurance of a helical tomotherapy machine[J].Phys Med Biol,2004,49(13):2933-2953.DOI:10.1088/0031-9155/49/13/012. [11] Chapman D,Barnett R,Yartsev S.Helical tomotherapy quality assurance with ArcCHECK[J].Med Dosim,2014,39(2):159-162.DOI:10.1016/j.meddos.2013.12.002.
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