Evaluation of IMRT Patient Specific Quality Assurance with Ion Chambers of Different Active Volumes
Objectives: IMRT is a novel technique in radiotherapy. Our aim is to compare the point dosimetry in treatment planning system and on actual phantom with different volume chambers in IMRT QA.
Methods/Statistical Analysis: 18 patient plans of IMRT with different lesions were selected for this work. Ionization chambers with 0.6 cc , 0.13 cc and IMRT slab phantom were used. Both the chambers were calibrated in national standard laboratory. Treatment machine calibration was verified before doing this dosimetry. Electrometer stability is also verified for the good results. QA plans were exported to linear accelerator after the TPS measurements. All the results were compared.
Findings: The maximum variation observed between the chambers in measured data is 3.51 % where as in TPS this is 2.2 % only which is within acceptable limit. Also, it is observed that, 0.13 cc chamber showed less deviation in few cases where dose gradient is more in the plan. With the advancements in the equipment and technology, varieties of ionization chambers with different sensitive volumes are currently available in the market. Also, intensity modulated radiotherapy practice has been increasing constantly due to its proved results. It is very important for a physicist to select a suitable chamber for doing patient specific QA. Hence, this type of study will help for practicing physicists/dosimetrists.
Application/Improvements: This study can be extended with more number of sensitive volume chambers from different vendors.
- J.M. Galvin, G. Ezzell, A. Eisbrauch, C. Yu, B. Butler, Y. Xiao. Implementing IMRT in clinical practice: a joint document of the american society for therapeutic radiology and oncology and the American association of physicists in medicine. International Journal of Radiation Oncology. 2004; 58(5), 1616-1634.
- G.A. Ezzell. Quality assurance. When and what is enough for IMRT? In: intensity modulated radiation therapy: the state of the art. American Association of Physicists in Medicine Medical Physics Monograph. Medical Physics Publishing. 2003; 613-616.
- G.A. Ezzell, J.M. Galvin, D. Low, J.R. Palta, I. Rosen, M.B. Sharpe. Guidance document on delivery, treatment planning, and clinical implementation of IMRT: Report of the IMRT Subcommittee of the AAPM Radiation Therapy Committee. Medical Physics. 2003; 30(8), 2089-115.
- L. Escudé, D. Linero, M. Mollà, R. Maralbell. Quality assurance for radiotherapy in prostate cancer: Point dose measurements in intensity modulated fields with large dose gradients. International Journal of Radiation Oncology, Biology and Physics. 2006; 66(4), 136-140.
- R. Kumar, S.D. Sharma, S. Deshpande, N.M. Sresty, C.P. Bhatt, H.I. Amols. Analysis of patient specific dosimetry quality assurance measurements in intensity modulated radiotherapy: A multi centre study. Journal of Cancer Research and Therapeutics. 2014; 10, 611-617.
- M. Alber, S. Broggi, C.D. Wagter, I. Eichwurzel, P. Engström, C. Fiorino. Guidelines for the verification of IMRT. ESTRO Mounierlaan 83/12 – 1200 Brussels (Belgium). 2008; 1-136.
- M. Van Zijtveld, M.L. Dirkx, H.C. Boer, B.J. Heijmen. Dosimetric pre treatment verification of IMRT using an EPID; clinical experience. Radiotherapy and Oncology. 2006; 81, 168-175.
- S.A. Syam Kumar, P. Sukumar, P. Sriram, D. Rajasekaran, S. Aketi, N. Vivekanandan. A patient-specific quality assurance study on absolute dose verification using ionization chambers of different volumes in rapid Arc treatments. Medical Dosimetry. 2012; 37(4), 436-441
- Absorbed dose determination in external beam radiotherapy: an international code of practice for dosimetry based on standards of absorbed dose to water. International Atomic Energy Agency (IAEA). 2000; 1-242.
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