Initial clinical experience with ArcCHECK for IMRT/VMAT QA.
Many devices designed for the purpose of performing patient-specific IMRT/VMAT QA are commercially available. In this work we report our experience and initial clinical results with the ArcCHECK. The ArcCHECK consists of a cylindrical array of diode detectors measuring entry and exit doses. The measured result is a cumulative dose displayed as a 2D matrix. The detector array requires both an absolute dose calibration, and a calibration of the detector response, relative to each other. In addition to the calibrations suggested by the manufacturer, various tests were performed in order to assess its stability and performance prior to clinical introduction. Tests of uniformity, linearity, and repetition rate dependence of the detector response were conducted and described in this work. Following initial test-ing, the ArcCHECK device was introduced in the clinic for routine patient-specific IMRT QA. The clinical results from one year of use were collected and analyzed. The gamma pass rates at the 3%/3 mm criterion were reported for 3,116 cases that included both IMRT and VMAT treatment plans delivered on 18 linear accelera-tors. The gamma pass rates were categorized based on the treatment site, treatment technique, type of MLCs, operator, ArcCHECK device, and LINAC model. We recorded the percent of failures at the clinically acceptable threshold of 90%. In addition, we calculated the threshold that encompasses two standard deviations (2 SD) (95%) of QAs (T95) for each category investigated. The commissioning measurements demonstrated that the device performed as expected. The uniformity of the detector response to a constant field arc delivery showed a 1% standard deviation from the mean. The variation in dose with changing repetition rate was within 1 cGy of the mean, while the measured dose showed a linear relation with delivered MUs. Our initial patient QA results showed that, at the clinically selected passing criterion, 4.5% of cases failed. On average T95 was 91%, rang-ing from 73% for gynecological sites to 96.5% for central nervous system sites. There are statistically significant differences in passing rates between IMRT and VMAT, high-definition (HD) and non-HD MLCs, and different LINAC models (p-values << 0.001). An additional investigation into the failing QAs and a com-parison with ion-chamber measurements reveals that the differences observed in the passing rates between the different studied factors can be largely explained by the field size dependence of the device. Based on our initial experience with the ArcCHECK, our passing rates are, on average, consistent with values reported in the AAPM TG-119. However, the significant variations between QAs that were observed based on the size of the treatment fields may need to be corrected to improve the specificity and sensitivity of the device.
The University of Texas MD Anderson Cancer Center. maristophanous@mdanderson.org.
Michalis
M
Aristophanous
Yelin
Y
Suh
Pai C
PC
Chi
Luke J
LJ
Whittlesey
Scott
S
LaNeave
Mary K
MK
Martel
D002138:Calibration; D005720:Gamma Rays; D006801:Humans; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care / Q000592:standards*; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000295:instrumentation / Q000592:standards*; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000592:standards*
Med Phys. 2010 Jan;37(1):108-15
20175471
Med Phys. 2011 Sep;38(9):5021-32
21978046
Phys Med. 2013 May;29(3):295-303
22583979
Med Phys. 2008 Jan;35(1):310-7
18293586
J Appl Clin Med Phys. 2011 Jan 31;12(2):3346
21587178
Int J Radiat Oncol Biol Phys. 2001 Nov 15;51(4):880-914
11704310
Med Phys. 1999 Sep;26(9):1847-70
10505874
Int J Radiat Oncol Biol Phys. 1993 May 20;26(2):261-73
8491684
Int J Radiat Oncol Biol Phys. 1996 Jul 1;35(4):721-30
8690638
Med Phys. 2012 Jul;39(7):4228-38
22830756
Med Phys. 2011 Mar;38(3):1313-38
21520843
Radiother Oncol. 1996 Sep;40(3):271-9
8940755
Med Phys. 2010 Jun;37(6):2516-24
20632563
Int J Radiat Oncol Biol Phys. 1997 Aug 1;39(1):99-114
9300745
J Appl Clin Med Phys. 2014 Jul 08;15(4):4832
25207411
Med Dosim. 2013 Spring;38(1):77-80
22917964
Med Phys. 2009 Nov;36(11):5359-73
19994544
Int J Radiat Oncol Biol Phys. 2001 Nov 1;51(3):579-88
11597796
Semin Radiat Oncol. 2004 Apr;14(2):103-9
15095256
Int J Radiat Oncol Biol Phys. 2004 Apr 1;58(5):1616-34
15050343
Int J Radiat Oncol Biol Phys. 2000 Oct 1;48(3):649-56
11020560