Journal List > Prog Med Phys > v.25(2) > 1098461

TOOLS
Jin, Jesseph, and Ahmad: A Comparison Study of Volumetric Modulated Arc Therapy Quality Assurances Using Portal Dosimetry and MapCHECK 2
Original Article

Progress in Medical Physics 2014;25(2):65-71.

Published online: 20 June 2014

DOI: https://doi.org/10.14316/pmp.2014.25.2.65

A Comparison Study of Volumetric Modulated Arc Therapy Quality Assurances Using Portal Dosimetry and MapCHECK 2

Hosang Jin, Fredrick B. Jesseph, Salahuddin Ahmad

Department of Radiation Oncology, Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma, USA

Correspondence: Hosang Jin(hosang-jin@ouhsc.edu) Tel:1-405-271-3016, Fax:1-405-271-8297

Received 18 April 2014       Revised 13 May 2014       Accepted 3 June 2014

Copyright © 2014 Korean Society of Medical Physics

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A Varian Portal Dosimetry system was compared to an isocentrically mounted MapCHECK 2 diode array for volumetric modulated arc therapy (VMAT) QA. A Varian TrueBeam STx with an aS-1000 digital imaging panel was used to acquire VMAT QA images for 13 plans using four photon energies (6, 8, 10 and 15 MV). The EPID-based QA images were compared to the Portal Dose Image Prediction calculated in the Varian Eclipse treatment planning system (TPS). An isocentrically mounted Sun Nuclear MapCHECK 2 diode array with 5 cm water-equivalent buildup was also used for the VMAT QAs and the measurements were compared to a composite dose plane from the Eclipse TPS. A γtest was implemented in the Sun Nuclear Patient software with 10% threshold and absolute comparison at 1%/1 mm (dose difference/distance-to-agreement), 2%/2 mm, and 3%/3 mm criteria for both QA methods. The two-tailed paired Student's t-test was employed to analyze the statistical significance at 95% confidence level. The average γpassing rates were greater than 95% at 3%/3 mm using both methods for all four energies. The differences in the average passing rates between the two methods were within 1.7% and 1.6% of each other when analyzed at 2%/2 mm and 3%/3 mm, respectively. The EPID passing rates were somewhat better than the MapCHECK 2 when analyzed at 1%/1 mm; the difference was lower for 8 MV and 10 MV. However, the differences were not statistically significant for all criteria and energies (p-values ＞0.05). The EPID-based QA showed large off-axis over-response and dependence of γpassing rate on energy, while the MapCHECK 2 was susceptible to the MLC tongue-and-groove effect. The two fluence-based QA techniques can be an alternative tool of VMAT QA to each other, if the limitations of each QA method (mechanical sag, detector response, and detector alignment) are carefully considered.

Keywords: Pretreatment QA, VMAT, EPID, Portal dosimetry, MapCHECK 2

References

1. Bakhtiari M, Kumaraswamy L, Bailey DW, de Boer S, Malhotra HK, Podgorsak MB. Using a n EPID for pa – tient-specific V MA T quality a ssur ance. Me d P hys. 38:1366–1373. 2011.
2. Sharma DS, Mhatre V, Heigrujam M, Talapatra K, Mallik S. Portal dosimetry for pretreatment verification of IMRT plan: a comparison with 2D ion chamber array. J Appl Clin Med Phys. 11:238–248. 2010.
crossref
3. Clemente S, Caivano R, Cozzolino M, et al. To evaluate the accuracy of dynamic versus static IMRT delivery using portal dosimetry. Clin Transl Onc ol. 16:208–212. 2014.
crossref
4. Bailey DW, Kumaraswamy L, Bakhtiari M, Malhotra HK, Podgorsak MB. EPID dosimetry for pr etre atment quality assurance with t w o c ommerc ial syste ms. J A pp l Clin Me d Phys. 13:82–99. 2012.
5. Bailey DW, Kumaraswamy L, Bakhtiari M, Podgorsak MB. A two-dime nsional matrix corr ection for off-axis por tal dose prediction err ors. Me d Phys. 40:051704. 2013.
6. Bailey DW, Kumaraswamy L, Podgorsak MB. An effective correction algorithm for off-axis portal dosimetry errors. Med Phys 36: 40 8 9–40 9 4 (. 2009.
7. Huang Y-C, Yeh C-Y, Yeh J-H, et al. Clinical practice and evaluation of ele ctr onic p ortal imaging device for VM AT quality assurance. Med Dosim. 38:35–41. 2013.
8. Iftimia I, Cirino ET, Xiong L, Mower HW. Quality assurance methodology for Va rian R apid A rc tre atment pla ns. J A ppl Clin Med P hys. 11:130–143. 2010.
9. Nicolini G, Vanetti E, Clivio A, et al. The GLAaS algorithm for p ortal dosime try and quality assura nce of R ap i dA rc, an intensity modulate d rotational the rapy. Ra dia t Oncol. 3:24. 2008.
crossref
10. Rowshanfarzad P, Sabet M, O'Connor DJ, McCowan PM, McCurdy BM, Greer PB. Detection and corr ection for EPID and gantry sag during arc de livery using cine EP ID imaging. Med P hys. 39:623–635. 2012.
11. Gloi AM, Buchanan RE, Zuge CL, Goettler AM. RapidArc quality assurance through Ma pCHECK. J A pp l Clin Med P hys. 12:39–47. 2011.
12. Jursinic PA, Sharma R, Reuter J. MapCHECK use d for rotational IMRT measurements: step-and-shoot, TomoTherapy, RapidArc. Me d Phys. 37:2837–2846. 2010.
13. Rinaldin G, Perna L, Agnello G, et al. Quality a ssur ance of R apid A rc treatme nts: Per formanc es and pre-clinical ve r-ifications of a p lanar dete ctor (M apCHECK2). Phys Me dic a. 30:184–190. 2014.
14. Shim SJ, Shim JB, Lee SH, et al. Quality a ssur ance of volumetric modulated arc therapy for ele kta synergy. Kor ean J Med Phys. 23:33–41. 2012.
15. Varian Medical Systems: TrueBeamTM TrueBea m STxTM Technical reference guide (Version 1.6 Volume 2: Imaging; Docu ID ID. B501671R01, Revision D). V aria n Medic al Syste ms, Inc., Switzerland, (. 2011. ). , pp. 205–207.
16. Varian Medical Systems: Eclipse algorithms reference guide (P/N B503486R01B, docume nt ve rsion 1. 0). Va rian Me dic al Systems, I nc., Finland, (. 2011. ), pp.3 9 3–42 3.
17. Low DA, Harms WB, Mutic S, Purdy JA. A technique for the quantitative eva luation of dose distrib utions. Med Phys. 25:656–661. 1998.
18. Stock M, Kroupa B, Georg D. Interpretation a nd evaluation of the gamma index and the ga mma index a ng l e for the ve r-ification of IMRT hybrid plans. Phys Med Biol. 50:399–411. 2005.
19. Sweet J, Nicolaou N. Arc splitting for V MA T pa tient QA [abstract]. Med Phys. 39:3746. 2012.
20. Jin H, Keeling VP, Johnson DA, Ahmad S. Interplay effect of angular depende nce and calibration field size of MapCHECK 2 on R ap i dA rc quality a ssur ance. J Ap pl Clin Med Phys. 15:1–13. 2014.
21. Greer PB. Correction of pixel sensitivity variation and off-a xis response for a morphous silicon EP ID dosimetry. Med Phys. 32:3558–3568. 2005.
22. Greer PB. Off-axis dose response characteristics of an amor – phous silicon ele ctr onic p ortal imaging device. Med Phys. 34:3815–3824. 2007.
23. Deng J, Pawlicki T, Chen Y, Li J, Jiang SB, Ma C-M: The MLC tongue-and-groove effect on IMRT dose distributions. Phys Med Biol. 46:1039–1060. 2001.
24. Olch AJ. Evaluation of the ac cura cy of 3DVH software estimates of dose to virtual ion c ha mbe r and film in composite IMRT QA. Med P hys. 39:81–86. 2012.

Fig. 1.
Gamma analysis of a 6 MV VMAT QA plan at 1%/1 mm using the SNC Patient software. (a) EPID-based measurement, (b) Portal Dose Image Prediction, (c) failed gamma points for EPID-based QA, (d) MapCHECK 2 measurement, (e) calculated dose for MapCHECK 2, and (f) failed gamma points for MapCHECK 2 QA.
pmp-25-65f1.tif
Fig. 2.
Gamma passing rate of the 13 patients at 3%/3 mm: (a) EPID-based QA and (b) MapCHECK 2 QA. For plans with small (less than 10 cm) and large field size (greater than 20 cm), relatively low passing rates were observed for the EPID QA; however, the MapCHECK 2 QA did not show any particular dependence on field size.
pmp-25-65f2.tif
Table 1.
The γpassing rates (%) of EPID portal dosimetry (E) and MapCHECK 2 (M) QAs.
Beam energy Gamma criteria 6 MV 8 MV 10 MV 15 MV
1%/ 1 mm 2%/ 2 mm 3%/ 3 mm 1%/ 1 mm 2%/ 2 mm 3%/ 3 mm 1%/ 1 mm 2%/ 2 mm 3%/ 3 mm 1%/ 1 mm 2%/ 2 mm 3%/ 3 mm
EPID-based Mean 70.8 93.6 98.3 60.4 88.7 96.2 66.4 91.5 97.3 65.9 92.2 98.0
QA (E) S.D. 16.4 9.1 2.9 18.5 13.4 5.7 20.3 12.5 4.9 16.2 9.8 3.7
MapCHECK2 Mean 61.4 91.9 98.2 57.1 90.2 97.8 63.3 93.2 98.5 59.2 90.5 98.2
QA (M) S.D. 6.8 4.3 1.8 7.2 5.5 2.5 6.9 3.4 1.6 8.0 5.3 2.2
Difference Mean 9.4 1.7 0.1 3.4 –1.5 –1.6 3.1 –1.7 –1.2 6.7 1.7 –0.2
(E-M) S.D. 17.2 11.0 3.7 21.0 16.2 6.8 22.4 13.7 5.6 18.7 11.6 4.2
p-value (E vs s. M) 0.07 0.60 0.90 0.56 0.72 0.35 0.62 0.66 0.44 0.22 0.62 0.87
Table 2.
Statistical significance test (p-value) using Student's t-test between different energies.
γ criteria 6 MV vs. 8 MV 6 MV vs. 10 MV 6 MV vs. 15 MV
1%/ 2%/ 3%/ 1%/ 2%/ 3%/ 1%/ 2%/ 3%/
1 mm 2 mm 3 mm 1 mm 2 mm 3 mm 1 mm 2 mm 3 mm
EPID-based QA 0.0003 0.01 0.02 0.04 0.07 0.13 0.02 0.07 0.19
MapCHECK 2 QA 0.02 0.11 0.53 0.14 0.06 0.12 0.11 0.18 0.88
  8 MV vs. 10 MV 8 MV vs. 15 MV 10 MV vs. 15 MV
EPID-based QA 0.02 0.01 0.02 0.07 0.06 0.04 0.80 0.61 0.30
MapCHECK 2 QA 0.0002 0.01 0.16 0.13 0.71 0.39 0.02 0.01 0.17
TOOLS
Similar articles