Evaluating the Impact of Various Parameters on the Gamma Index Values of 2D Diode Array in IMRT Verification

keyvan Jabbari, fakhereh pashaei, Mohammad Reza Ay, Alireza Amouheidari, Mohammad Bagher Tavakoli

DOI: 10.4103/jmss.JMSS_15_17

Abstract


Background: MapCHECK2 is a two-dimensional diode arrays planar dosimetry verification system.
Dosimetric results are evaluated with gamma index. This study aims to provide comprehensive
information on the impact of various factors on the gamma index values of MapCHECK2, which is
mostly used for IMRT dose verification. Materials and Methods: Seven fields were planned for 6 and
18 MV photons. The azimuthal angle is defined as any rotation of collimators or the MapCHECK2
around the central axis, which was varied from 5 to -5°. The gantry angle was changed from -8 to 8°.
Isodose sampling resolution was studied in the range of 0.5 to 4 mm. The effects of additional buildup on
gamma index in three cases were also assessed. Gamma test acceptance criteria were 3%/3 mm. Results:
The change of azimuthal angle in 5° interval reduced gamma index value by about 9%. The results of
putting buildups of various thicknesses on the MapCHECK2 surface showed that gamma index was
generally improved in thicker buildup, especially for 18 MV. Changing the sampling resolution from 4 to
2 mm resulted in an increase in gamma index by about 3.7%. The deviation of the gantry in 8° intervals in
either directions changed the gamma index only by about 1.6% for 6 MV and 2.1% for 18 MV.
Conclusion: Among the studied parameters, the azimuthal angle is one of the most effective factors on
gamma index value. The gantry angle deviation and sampling resolution are less effective on gamma
index value reduction.

Keywords


Gamma index, intensity modulated radiation therapy verification, MapCHECK2, twodimensional array

Full Text:

PDF

References


Levitt SH, Khan FM. The rush to judgment: Does the evidence support the enthusiasm over three-dimensional conformal radiation therapy and dose escalation in the treatment of prostate cancer?. Int J Radiat Oncol Biol Phys 2001;51:871-9.

Ellis F, Hall E, Oliver R. A compensator for variations in tissue thickness for high energy beams. Br J Radiol 1959;32:421-2.

Jursinic PA, Podgorsak MB, Paliwal BR. Implementation of a threedimensional compensation system based on computed tomography generated surface contours and tissue inhomogeneities. Med Phys 1994;21:357-65.

McShan D, Fraass B, Lichter A. Full integration of the beams eye view concept into computerized treatment planning. Int J Radiat Oncol Biol Phys 1990;18:1485-94.

Sherouse GW, Bourland JD, Reynolds K, McMurry HL, Mitchell TP, Chaney EL. Virtual simulation in the clinical setting: Some practical considerations. Int J Radiat Oncol Biol Phys 1990;19: 1059-65.

Ezzell GA, Galvin JM, Low D, Palta JR, Rosen I, Sharpe MB, et al. Guidance document on delivery, treatment planning, and clinical implementation of IMRT: Report of the IMRT Subcommittee of the AAPM Radiation Therapy Committee. Med Phys 2003;30: 2089-115.

Tsai J-S., Wazer DE, Ling MN, Wu JK, Fagundes M, DiPetrillo T, et al. Dosimetric verification of the dynamic intensity-modulated radiation therapy of 92 patients. Int J Radiat Oncol Biol Phys 1998;40:1213-30.

Xing L, Curran B, Hill R, Holmes T, Ma L, Forster KM, et al. Dosimetric verification of a commercial inverse treatment planning system. Phys Med Biol 1999;44:463.

Zhu X, Jursinic P, Grimm D, Lopez F, Rownd J, Gillin M. Evaluation of Kodak EDR2 film for dose verification of intensity modulated radiation therapy delivered by a static multileaf collimator. Med Phys 2002;29:1687-92.

Nath R, Biggs PJ, Bova FJ, Ling CC, Purdy JA, van de Geijn J, et al. AAPM code of practice for radiotherapy accelerators: Report of AAPM Radiation Therapy Task Group No. 45. Med Phys 1994;21:1093-121.

Kutcher GJ, Coia L, Gillin M, Hanson WF, Leibel S, Morton RJ, et al. Comprehensive QA for radiation oncology: Report of AAPM Radiation Therapy Committee Task Group 40. Med Phys 1994;21:581-618.

Fraass B, Doppke K, Hunt M, Kutcher G, Starkschall G, Stern R, et al. American Association of Physicists in Medicine Radiation Therapy Committee Task Group 53: Quality assurance for clinical radiotherapy treatment planning. Med Phys 1998;25: 1773-829.

Olch AJ. Evaluation of the accuracy of 3DVH software estimates of dose to virtual ion chamber and film in composite IMRT QA. Med Phys 2012;39:81-6.

Keeling VP, Ahmad S, Jin H. A comprehensive comparison study of three different planar IMRT QA techniques using MapCHECK 2. J Appl Clin Med Phys 2013;14:222-33.

Jursinic PA, Nelms BE. A 2-D diode array and analysis software for verification of intensity modulated radiation therapy delivery. Med Phys 2003;30:870-9.

Letourneau D, Gulam M, Yan D, Oldham M, Wong JW. Evaluation of a 2D diode array for IMRT quality assurance. Radiother Oncol 2004;70:199-206.

Yorke E, Alecu R, Ding L, Fontenla D, Kalend A, Kaurin D, et al. Diode in vivo dosimetry for patients receiving external beam radiation therapy. Report of the American Association of Physicists in Medicine (AAPM) Task Group 62. AAPM Report; 2005.

Saini AS, Zhu TC. Energy dependence of commercially available diode detectors for in-vivo dosimetry. Med Phys 2007;34:1704-11.

WolffT,Carter S, LangmackK,TwymanN,Dendy P.Characterization and use of a commercial n-type diode system. Br J Radiol 1998;71:1168-77.

Low DA, Harms WB, Mutic S, Purdy JA. A technique for the quantitative evaluation of dose distributions. Med Phys 1998;25: 656-61.

Li JG, Yan G, Liu C. Comparison of two commercial detector arrays

for IMRT quality assurance. J Appl Clin Med Phys 2009;10:62-74.

Basran PS, Woo MK. An analysis of tolerance levels in IMRT quality assurance procedures. Med Phys 2008;35:2300-7.

Both S, Alecu IM, Stan AR, Alecu M, Ciura A, Hansen JM, Alecu R. A study to establish reasonable action limits for patient-specific quality assurance in intensity-modulated radiation therapy. J Appl Clin Med Phys 2007;8:1-8.

Ezzell GA, Burmeister JW, Dogan N, LoSasso TJ, Mechalakos JG, Mihailidis D, et al. IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119. Med Phys 2009;36:5359-73.

Li Q, Deng X, Chen L, Huang X, Huang S. The angular dependence of a 2-dimensional diode array and the feasibility of its application in verifying the composite dose distribution of intensity-modulated radiation therapy. Chin J Cancer 2010;29:617-20.

Keeling VP, Ahmad S, Algan O, Jin H. Dependency of planned dose perturbation (PDP) on the spatial resolution of MapCHECK 2 detectors. J Appl Clin Med Phys 2014;15:100-17.

Jin H, Keeling VP, Johnson DA, Ahmad S. Interplay effect of angular dependence and calibration field size of MapCHECK 2 on RapidArc quality assurance. J Appl Clin Med Phys 2014;15:80-92.

Rinaldin G, Perna L, Agnello G, Pallazzi G, Cattaneo G, Fiorino C, et al. Quality assurance of Rapid Arc treatments: Performances and pre clinical verifications of a planar detector (MapCHECK2). Phys Med 2014;30:184-90.


Refbacks

  • There are currently no refbacks.


 

  https://e-rasaneh.ir/Certificate/22728

https://e-rasaneh.ir/

ISSN : 2228-7477