Treatment planning validation for symmetric and asymmetric motorized wedged fields
Purpose: Wedged beam are often used in clinical radiotherapy to compensate missing tissues and dose gradients. The Elekta Precise linear accelerator supports an internal motorized wedge, which is a single large, physical wedge on a motorized carriage. In this study, the dosimetric performance of Elekta precise three dimensional treatment planning system (3DTPS) is evaluated by comparing the calculated and measured doses.
Methods: The calculations were performed by the 3DTPS for symmetric as well as asymmetric fields in a source to skin distance (SSD) setup at the depth of maximum dose (dmax) as well as at 5, 10, and 20 cm depths in water phantom using 60° motorized wedges for field sizes of 4 × 4, 10 × 10, and 20 × 20 cm2 for 6 and 15 MV photon beams. Measurements were produced by Elekta Precise linear accelerator using 0.125 cc volume ionization chamber.
Results: Good agreement between the measured and calculated isodose lines were found, with the maximum difference not exceed 5%. The difference between the calculated and measured data increases as the field size decreases, and the deviation in symmetric setting was less than that of asymmetric setting. The increase in wedge angle led to increase in the difference between calculated and measured data.
Conclusion: The results from this study showed that the accuracy of Elekta Precise 3DTPS used with the motorized wedges for symmetric and asymmetric fields is adequate for the clinical applications under the studied experimental conditions.
Ravichandran R. Has the time come for doing away with Cobalt-60 teletherapy for cancer treatments. J Med Phys 2009; 34:63-5.
Alam R, Ibbott GS, Pourang R, Nath R. Application of AAPM Radiation Therapy Committee Task Group 23 test package for comparison of two treatment planning systems for photon external beam radiotherapy. Med Phys 1997; 24:2043-54.
Murugan A, Valas XS, Thayalan K, Ramasubramanian V. Dosimetric evaluation of a three-dimensional treatment planning system. 2011; 36:15-21.
Tome WA, Meeks SL, Buatti JM, et al. A high-precision system for conformal intracranial radiotherapy. Int J Radiat Oncol Biol Phys 2000; 47:1137-43.
Shahid M, Rafique A, Sabir R, et al. Dosimetric evaluation of treatment planning using dynamic and physical wedges: a comparative study. Peak Journal of Medicine and Medical Science 2013; 1:39-48.
Venselaar J, Welleweerd H. Application of a test package in an intercomparison of the photon dose calculation performance of treatment planning systems used in a clinical setting. Radiother Oncol 2001; 60:203-13.
Venselaar J, Welleweerd H, Mijnheer B. Tolerances for the accuracy of photon beam dose calculations of treatment planning systems. Radiother Oncol 2001; 60:191-201.
Smulders B, Bruinvis IA, Mijnheer BJ. Monitor unit calculations for wedged asymmetric photon beams. Phys Med Biol 2002; 47:2013-30.
Popescu A, Lai K, Singer K, Phillips M. Wedge factor dependence with depth, field size, and nominal distance--a general computational rule. Med Phys 1999; 26:541-9.
Ahmad M, Hussain A, Muhammad W, et al. Studying wedge factors and beam profiles for physical and enhanced dynamic wedges. J Med Phys 2010; 35:33-41.
Kinhikar RA, Sharma S, Upreti R, et al. Characterizing and configuring motorized wedge for a new generation telecobalt machine in a treatment planning system. J Med Phys 2007; 32:29-33.
Spezi E, Lewis DG, Smith CW. Monte Carlo simulation and dosimetric verification of radiotherapy beam modifiers. Phys Med Biol 2001; 46:3007-29.
Miften M, Zhu XR, Takahashi K, et al. Implementation and verification of virtual wedge in a three-dimensional radiotherapy planning system. Med Phys 2000; 27:1635-43.
Liu HH, Lief EP, McCullough EC. Measuring dose distributions for enhanced dynamic wedges using a multichamber detector array. Med Phys 1997; 24:1515-9.
Bidmead AM, Garton AJ, Childs PJ. Beam data measurements for dynamic wedges on Varian 600C (6 MV) and 2100C (6 and 10 MV) linear accelerators. Phys Med Biol 1995; 40:393-411.
Halperin EC, Perez CA, Brady LW. Perez and Brady's Principles and Practice of Radiation Oncology, 5th Edition. Lippincott Williams & Wilkins 2007.
Mayles P, Nahum A, Rosenwald JC. Handbook of radiotherapy physics: theory and practice. Taylor & Francis Group, LLC 2007.
Pokharel S. Dosimetric impact of mixed-energy volumetric modulated arc therapy plans for high-risk prostate cancer. Int J Cancer Ther Oncol 2013; 1:01011.
Khan FM. The Physics of Radiation Therapy. 4th Edition. Williams and Wilkins, London. 2010.
Van Dyk J, Barnett R, Cygler J, Shragge P. Commissioning and quality assurance of treatment planning computers. Int J Radiat Oncol Biol Phys 1993; 26:261-73.
Fraass B, Doppke K, Hunt M, 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.
Anjum MN, Qadir A, Afzal M. Dosimetric evaluation of a treatment planning system using pencil beam convolution algorithm for enhanced dynamic wedges with symmetric and asymmetric fields. Iran J Radiat Res 2008; 5: 169-74.
Caprile PF, Venencia CD, Besa P. Comparison between measured and calculated dynamic wedge dose distributions using the anisotropic analytic algorithm and pencil-beam convolution. J Appl Clin Med Phys 2006; 8:47-54.
Muhammad W, Maqbool M, Shahid M, et al. Technical note: Accuracy checks of physical beam modifier factors algorithm used in computerized treatment planning system for a 15 MV photon beam. Rep Pract Oncol Radiother 2009; 14: 214-20.
Nath R, Biggs PJ, Bova FJ, et al. AAPM code of practice for radiotherapy accelerators: report of AAPM Radiation Therapy Task Group No. 45. Med Phys 1994; 21:1093-121.
Pasquino M, Casanova Borca V, Tofani S, Ozzello F. Verification of Varian Enhanced Dynamic Wedge implementation in masterplan treatment planning system. J Appl Clin Med Phys 2009; 10:2867.
Momennezhad M, Bahreyni Toosi MT, Sadeghi R, et al. A Monte Carlo simulation and dosimetric verification of physical wedges used in radiation Therapy. Iran J Radiat Res 2010; 7: 223-7.
Oyewale S. Dose prediction accuracy of collapsed cone convolution superposition algorithm in a multi-layer inhomogenous phantom. Int J Cancer Ther Oncol 2013; 1:01016.
Rana SB. Dose prediction accuracy of anisotropic analytical algorithm and pencil beam convolution algorithm beyond high density heterogeneity interface. South Asian J Cancer 2013;2:26-30.
Ojala J. The accuracy of the Acuros XB algorithm in external beam radiotherapy – a comprehensive review. Int J Cancer Ther Oncol 2014; 2:020417.
Lu L. Dose calculation algorithms in external beam photon radiation therapy. Int J Cancer Ther Oncol 2013; 1:01025.
This work is licensed under a Creative Commons Attribution 3.0 License.
International Journal of Cancer Therapy and Oncology (ISSN 2330-4049)
© International Journal of Cancer Therapy and Oncology (IJCTO)
To make sure that you can receive messages from us, please add the 'ijcto.org' domain to your e-mail 'safe list'. If you do not receive e-mail in your 'inbox', check your 'bulk mail' or 'junk mail' folders.