An EPID-based system for gantry-resolved MLC quality assurance for VMAT.
Multileaf collimator (MLC) positions should be precisely and independently mea-sured as a function of gantry angle as part of a comprehensive quality assurance (QA) program for volumetric-modulated arc therapy (VMAT). It is also ideal that such a QA program has the ability to relate MLC positional accuracy to patient-specific dosimetry in order to determine the clinical significance of any detected MLC errors. In this work we propose a method to verify individual MLC trajectories during VMAT deliveries for use as a routine linear accelerator QA tool. We also extend this method to reconstruct the 3D patient dose in the treatment planning sys-tem based on the measured MLC trajectories and the original DICOM plan file. The method relies on extracting MLC positions from EPID images acquired at 8.41fps during clinical VMAT deliveries. A gantry angle is automatically tagged to each image in order to obtain the MLC trajectories as a function of gantry angle. This analysis was performed for six clinical VMAT plans acquired at monthly intervals for three months. The measured trajectories for each delivery were compared to the MLC positions from the DICOM plan file. The maximum mean error detected was 0.07 mm and a maximum root-mean-square error was 0.8 mm for any leaf of any delivery. The sensitivity of this system was characterized by introducing random and systematic MLC errors into the test plans. It was demonstrated that the system is capable of detecting random and systematic errors on the range of 1-2mm and single leaf calibration errors of 0.5 mm. The methodology developed in the work has potential to be used for efficient routine linear accelerator MLC QA and pretreatment patient-specific QA and has the ability to relate measured MLC positional errors to 3D dosimetric errors within a patient volume.
Gosford Hospital; University of Newcastle. benjamin.zwan@health.nsw.gov.au.
Benjamin J
BJ
Zwan
Michael P
MP
Barnes
Todsaporn
T
Fuangord
Cameron J
CJ
Stanton
Daryl J
DJ
O'Connor
Paul J
PJ
Keall
Peter B
PB
Greer
D055615:Electrical Equipment and Supplies; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy; D010315:Particle Accelerators / Q000295:instrumentation*; D011785:Quality Assurance, Health Care / Q000379:methods*; D011786:Quality Control; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000592:standards*; D012984:Software
Med Phys. 2011 Sep;38(9):5146-66
21978060
Med Phys. 2010 Jul;37(7):3862-7
20831094
Med Phys. 2009 Oct;36(10):4530-5
19928084
Med Phys. 2008 Jan;35(1):310-7
18293586
Med Phys. 2002 Sep;29(9):2034-40
12349924
Med Phys. 2004 Mar;31(3):463-76
15070242
Phys Med Biol. 2014 Jan 6;59(1):61-81
24334552
Int J Radiat Oncol Biol Phys. 2008 Oct 1;72(2):575-81
18793960
Phys Med Biol. 2005 Apr 7;50(7):1377-92
15798330
Phys Med Biol. 2014 May 7;59(9):N49-63
24732210
J Appl Clin Med Phys. 2011 Nov 15;12(4):3456
22089001
J Appl Clin Med Phys. 2004 Summer;5(3):37-54
15753938
Phys Med Biol. 2006 Nov 7;51(21):5517-38
17047267
Phys Med Biol. 2011 Aug 7;56(15):4827-38
21753232
Phys Med Biol. 1995 Sep;40(9):1435-49
8532757
Med Phys. 2002 May;29(5):810-20
12033577
Med Phys. 2011 Mar;38(3):1425-34
21520854
Med Phys. 2012 Oct;39(10):6192-207
23039657
Phys Med Biol. 2010 Jul 7;55(13):3597-610
20526034
Med Phys. 2003 Oct;30(10):2736-49
14596312
Med Phys. 2011 Apr;38(4):2246-55
21626959
Med Phys. 2003 May;30(5):799-805
12772987
Med Phys. 2013 Aug;40(8):081715
23927312
Med Phys. 2012 Feb;39(2):623-35
22320771
Med Phys. 2013 Sep;40(9):091907
24007158
Radiother Oncol. 2010 Dec;97(3):554-60
20817291
Int J Radiat Oncol Biol Phys. 2008;71(1 Suppl):S85-8
18406945
Med Phys. 2009 Jul;36(7):3304-9
19673226
J Appl Clin Med Phys. 2014 Jan 06;15(1):4507
24423849
Radiother Oncol. 2006 Jul;80(1):86-92
16854483
Phys Med. 2012 Jul;28(3):262-8
21784685
Phys Med Biol. 2000 Feb;45(2):495-509
10701517
Med Phys. 2004 Feb;31(2):389-95
15000625
Phys Med Biol. 2000 May;45(5):1211-27
10843101
Med Phys. 2006 Jul;33(7):2557-64
16898460
Med Phys. 2011 Mar;38(3):1366-73
21520847
J Appl Clin Med Phys. 2010 Nov 16;12(1):3373
21330988
Med Phys. 1996 May;23(5):635-41
8724734
Phys Med Biol. 2010 Jun 7;55(11):3101-13
20463373
Int J Radiat Oncol Biol Phys. 2008 Feb 1;70(2):634-44
18207036
Radiother Oncol. 2009 Nov;93(2):226-33
19765846
Med Phys. 2004 Jun;31(6):1593-602
15259664