The sensitivity of gamma-index method to the positioning errors of high-definition MLC in patient-specific VMAT QA for SBRT

Radiation Oncology

Jong Min Park³  Sung-Joon Ye¹  Jin Ho Kim²  Hak Jae Kim²  So-Yeon Park⁴  Jung-in Kim³ 

[1] Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Seoul, Korea;Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea;Center for Convergence Research on Robotics, Advance Institutes of Convergence Technology, Suwon, Korea;Interdiciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea

关键词: High-definition multi-leaf collimator;    Dose-volumetric indicator;    Gamma-index method;    Stereotactic body radiation therapy;    Patient-specific quality assurance;   

Others  :  1132064
DOI  :  10.1186/1748-717X-9-167

 received in 2013-12-20, accepted in 2014-07-21,  发布年份 2014

【 摘 要 】

Background

To investigate the sensitivity of various gamma criteria used in the gamma-index method for patient-specific volumetric modulated arc therapy (VMAT) quality assurance (QA) for stereotactic body radiation therapy (SBRT) using a flattening filter free (FFF) photon beam.

Methods

Three types of intentional misalignments were introduced to original high-definition multi-leaf collimator (HD-MLC) plans. The first type, referred to Class Out, involved the opening of each bank of leaves. The second type, Class In, involved the closing of each bank of leaves. The third type, Class Shift, involved the shifting of each bank of leaves towards the ground. Patient-specific QAs for the original and the modified plans were performed with MapCHECK2 and EBT2 films. The sensitivity of the gamma-index method using criteria of 1%/1 mm, 1.5%/1.5 mm, 1%/2 mm, 2%/1 mm and 2%/2 mm was investigated with absolute passing rates according to the magnitudes of MLCs misalignments. In addition, the changes in dose-volumetric indicators due to the magnitudes of MLC misalignments were investigated. The correlations between passing rates and the changes in dose-volumetric indicators were also investigated using Spearman’s rank correlation coefficient (γ).

Results

The criterion of 2%/1 mm was able to detect Class Out and Class In MLC misalignments of 0.5 mm and Class Shift misalignments of 1 mm. The widely adopted clinical criterion of 2%/2 mm was not able to detect 0.5 mm MLC errors of the Class Out or Class In types, and also unable to detect 3 mm Class Shift errors. No correlations were observed between dose-volumetric changes and gamma passing rates (γ < 0.8).

Conclusions

Gamma criterion of 2%/1 mm was found to be suitable as a tolerance level with passing rates of 90% and 80% for patient-specific VMAT QA for SBRT when using MapCHECK2 and EBT2 film, respectively.

【 授权许可】

   
2014 Kim et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

Figure 2.

Figure 3.

Figure 4.

【 参考文献 】

• [1]Ezzell GA, Galvin JM, Low D, Palta JR, Rosen I, Sharpe MB, Xia P, Xiao Y, Xing L, Yu CX: 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, 30:2089-2115.
• [2]Low DA, Harms WB, Mutic S, Purdy JA: A technique for the quantitative evaluation of dose distributions. Med Phys 1998, 25:656-661.
• [3]Ezzell GA, Burmeister JW, Dogan N, LoSasso TJ, Mechalakos JG, Mihailidis D, Molineu A, Palta JR, Ramsey CR, Salter BJ, Shi J, Xia P, Yue NJ, Xiao Y: IMRT commissioning: multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119. Med Phys 2009, 36:5359-5373.
• [4]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 Clinl Med Phys 2007, 8:1-8.
• [5]Davidson MT, Blake SJ, Batchelar DL, Cheung P, Mah K: Assessing the role of volumetric modulated arc therapy (VMAT) relative to IMRT and helical tomotherapy in the management of localized, locally advanced, and post-operative prostate cancer. Int J Radiat Oncol Biol Phys 2011, 80:1550-1558.
• [6]Quan EM, Li X, Li Y, Wang X, Kudchadker RJ, Johnson JL, Kuban DA, Lee AK, Zhang X: A comprehensive comparison of IMRT and VMAT plan quality for prostate cancer treatment. Int J Radiat Oncol Biol Phys 2012, 83:1169-1178.
• [7]Sung W, Park JM, Choi CH: The effect of photon energy on intensity-modulated radiation therapy (IMRT) plans for prostate cancer. Radiat Oncol J 2012, 30:27-35.
• [8]Joo YK, Sung YP, Doo HL: Comparison of treatment plans with multileaf collimators of different leaf width. K J Med Phys 2004, 15:173-178.
• [9]Wagner D, Vorwerk H: Two years experience with quality assurance protocol for patient related Rapid Arc treatment plan verification using a two dimensional ionization chamber array. Radiat oncology 2011, 6:21. BioMed Central Full Text
• [10]Nelms BE, Zhen H, Tome WA: Per-beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors. Med Phys 2011, 38:1037-1044.
• [11]Zhen H, Nelms BE, Tome WA: Moving from gamma passing rates to patient DVH-based QA metrics in pretreatment dose QA. Med Phys 2011, 38:5477-5489.
• [12]Yan G, Liu C, Simon TA, Peng LC, Fox C, Li JG: On the sensitivity of patient-specific IMRT QA to MLC positioning errors. J Appl Clinl Med Phys 2009, 10:2915.
• [13]Heilemann G, Poppe B, Laub W: On the sensitivity of common gamma-index evaluation methods to MLC misalignments in Rapidarc quality assurance. Med Phys 2013, 40:031702.
• [14]Fredh A, Scherman JB, Fog LS, Munck af Rosenschold P: Patient QA systems for rotational radiation therapy: a comparative experimental study with intentional errors. Med Phys 2013, 40:031716.
• [15]Oliver M, Gagne I, Bush K, Zavgorodni S, Ansbacher W, Beckham W: Clinical significance of multi-leaf collimator positional errors for volumetric modulated arc therapy. Radiother Oncol 2010, 97:554-560.
• [16]Kathirvel M, Subramanian S, Clivio A, Arun G, Fogliata A, Nicolini G, Subramani V, Thirumalai Swamy S, Vanetti E, Thirumalai Swamy S, Vanetti E, Cozzi L: Critical appraisal of the accuracy of Acuros-XB and Anisotropic Analytical Algorithm compared to measurement and calculations with the compass system in the delivery of RapidArc clinical plans. Radiat oncology 2013, 8:140. BioMed Central Full Text
• [17]LoSasso T, Chui CS, Ling CC: Physical and dosimetric aspects of a multileaf collimation system used in the dynamic mode for implementing intensity modulated radiotherapy. Med Phys 1998, 25:1919-1927.
• [18]Benedict SH, Yenice KM, Followill D, Galvin JM, Hinson W, Kavanagh B, Keall P, Lovelock M, Meeks S, Papiez L, Purdie T, Sadagopan R, Schell MC, Salter B, Schlesinger DJ, Shiu AS, Solberg T, Song DY, Stieber V, Timmerman R, Tomé WA, Verellen D, Wang L, Yin FF: Stereotactic body radiation therapy: the report of AAPM Task Group 101. Med Phys 2010, 37:4078-4101.
• [19]Almond PR, Biggs PJ, Coursey BM, Hanson WF, Huq MS, Nath R, Rogers DW: AAPM's TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys 1999, 26:1847-1870.
• [20]Iftimia I, Cirino ET, Xiong L, Mower HW: Quality assurance methodology for Varian RapidArc treatment plans. J Appl Clinl Med Phys 2010, 11:3164.
• [21]Gloi AM, Buchana RE, Zuge CL, Goettler AM: RapidArc quality assurance through MapCHECK. J Appl Clinl Med Phys 2011, 12:3251.
• [22]Li H, Dong L, Zhang L, Yang JN, Gillin MT, Zhu XR: Toward a better understanding of the gamma index: Investigation of parameters with a surface-based distance method. Med Phys 2011, 38:6730-6741.
• [23]Timmerman R, Heinzerling J, Abdulrahman R, Choy H, Meyer JL: Stereotactic body radiation therapy for thoracic cancers: recommendations for patient selection, setup and therapy. Front Radiat Ther Oncol 2011, 43:395-411.
• [24]Poppe B, Blechschmidt A, Djouguela A, Kollhoff R, Rubach A, Willborn KC, Harder D: Two-dimensional ionization chamber arrays for IMRT plan verification. Med Phys 2006, 33:1005-1015.
• [25]Reinhardt S, Hillbrand M, Wilkens JJ, Assmann W: Comparison of Gafchromic EBT2 and EBT3 films for clinical photon and proton beams. Med Phys 2012, 39:5257-5262.
• [26]Li JG, Yan G, Liu C: Comparison of two commercial detector arrays for IMRT quality assurance. J Appl Clinl Med Phys 2009, 10:2942.
• [27]Kruse JJ: On the insensitivity of single field planar dosimetry to IMRT inaccuracies. Med Phys 2010, 37:2516-2524.
• [28]Rangel A, Palte G, Dunscombe P: The sensitivity of patient specific IMRT QC to systematic MLC leaf bank offset errors. Med Phys 2010, 37:3862-3867.