A Practical Method to Evaluate and Verify Dose Calculation Algorithms in the Treatment Planning System of Radiation Therapy

Author(s)
Lanchun Lu^{*},
Guy Yembi-Goma,
Jian Z. Wang,
Nilendu Gupta,
Zhibin Huang,
Simon S. Lo,
Douglas Martin,
Nina Mayr

Affiliation(s)

Department of Radiation Oncology, Ohio State University, Columbus, USA.

Department of Radiation Oncology, East Carolina University, Greenville, USA.

Department of Radiation Oncology, Case Western Reserve University, Cleveland, USA.

Department of Radiation Oncology, Ohio State University, Columbus, USA.

Department of Radiation Oncology, East Carolina University, Greenville, USA.

Department of Radiation Oncology, Case Western Reserve University, Cleveland, USA.

ABSTRACT

**Purpose:** To introduce a practical method of using** **an Electron Density Phantom (EDP) to evaluate different dose calculation algorithms for photon beams in a treatment planning system (TPS) and to commission the Anisotropic Analytical Algorithm (AAA) with inhomogeneity correction in Varian Eclipse TPS. **Methods and Materials:** The same EDP with various tissue-equivalent plugs (water, lung exhale, lung inhale, liver, breast, muscle, adipose, dense bone, trabecular bone) used to calibrate the computed tomography (CT) simulator was adopted to evaluate different dose calculation algorithms in a TPS by measuring the actual dose delivered to the EDP. The treatment plans with a 6-Megavolt (MV) single field of 20 × 20, 10 × 10, and 4 × 4 cm^{2} field sizes were created based on the CT images of the EDP. A dose of 200 cGy was prescribed to the exhale-lung insert. Dose calculations were performed with AAA with inhomogeneity correction, Pencil Beam Convolution (PBC), and AAA without inhomogeneity correction. The plans were delivered and the actual doses were measured using radiation dosimetry devices MapCheck, EDR2-film, and ionization chamber respectively. Measured doses were compared with the calculated doses from the treatment plans. **Results:** The calculated dose using the AAA with inhomogeneity correction was most consistent with the measured dose. The dose discrepancy for all types of tissues covered by beam fields is at the level of 2%. The effect of AAA inhomogeneity correction for lung tissues is over 14%. **Conclusions:** The use of EDP and Map Check to evaluate and commission the dose calculation algorithms in a TPS is practical. In Varian Eclipse TPS, the AAA with inhomogeneity correction should be used for treatment planning especially when lung tissues are involved in a small radiation field.

Cite this paper

L. Lu, G. Yembi-Goma, J. Wang, N. Gupta, Z. Huang, S. Lo, D. Martin and N. Mayr, "A Practical Method to Evaluate and Verify Dose Calculation Algorithms in the Treatment Planning System of Radiation Therapy,"*International Journal of Medical Physics, Clinical Engineering and Radiation Oncology*, Vol. 2 No. 3, 2013, pp. 76-87. doi: 10.4236/ijmpcero.2013.23011.

L. Lu, G. Yembi-Goma, J. Wang, N. Gupta, Z. Huang, S. Lo, D. Martin and N. Mayr, "A Practical Method to Evaluate and Verify Dose Calculation Algorithms in the Treatment Planning System of Radiation Therapy,"

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[13] J. J. Battista, M. B. Sharpe, E. Webb and J. Van Dyk, “A new Classification Scheme for Photon Beam Dose Algorithms,” In: D. D. Leavitt and G. Starkschall, Eds., International Conference on the Use of Computers in Radiation Therapy, XII ICCR, Salt Lake City, Medical Physics Physics Publishing, Madison, 1997, pp. 39-42.

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[18] M. B. Sharpe and J. J. Battista, “Dose Calculations Using Convolution and Superposition Principles: The Orientation of Dose Spread Kernals in Divergent X-Ray Beams,” Medical Physics, Vol. 20, No. 6, 1993, pp. 1685-1694. doi:10.1118/1.596955

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[21] C. X. Yu and J. W. Wong, “Implementation of the ETAR Method for 3D Inhomogeneity Corrections Using FFT,” Medical Physics, Vol. 20, No. 3, 1993, pp. 627-632. doi:10.1118/1.597010

[22] C.-M. Ma, J. S. Li, T. Pawlicki, et al., “A Monte Carlo Dose Calculation Tool for Radiotherapy Treatment Planning,” Physics in Medicine and Biology, Vol. 47, No. 10, 2002, pp. 1671-1689. doi:10.1118/1.597010

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[25] N. Papanikolaou, J. J. Battista, A. L. Boyer, et al., “Tissue Inhomogeneity Corrections for Megavoltage Photon Beams,” AAPM Report No. 85, AAPM TG65, 2004.

[26] A. Gray, L. D. Oliver and P. N. Johnston, “The Accuracy of the Pencil Beam Convolution and Anisotropic Analytical Algorithms in Predicting the Dose Effects Due to Attenuation from Immobilization Devices and Large Air Gaps,” Medical Physics, Vol. 36, No. 7, 2009, pp. 3181-3191. doi:10.1118/1.3147204

[27] A. V. Esch, L. Tillikainen, J. Pyykkonen, et al., “Testing of the Analytical Anisotropic Algorithm for Photon Dose Calculation,” Medical Physics, Vol. 33, No. 11, 2006, pp. 4130-4148. doi:10.1118/1.3147204

[28] B. Kavanagh, M. S. Ding, T. Schefter, et al., “The Dosimetric Effect of Inhomogeneity Correction in Dynamic Conformal ARC Stereotactic Body Radiation Therapy for Lung Tumors,” Journal of Applied Clinical Medical Physics, Vol. 7, No. 2, 2006, pp. 58-63. doi:10.1118/1.3147204

[29] D. Robinson, “Inhomogeneity Correction and the Analytic Anisotropic Algorithm,” Journal of Applied Clinical Medical Physics, Vol. 9, No. 2, 2008, p. 2786. doi:10.1088/0031-9155/51/21/002

[30] T. Nishio, E. Kunieda, H. Shirato, et al., “Dosimetric Verification in Participating Institutions in a Stereotactic Body Radiotherapy Trial for Stage I Non-Small Cell Lung Cancer: Japan Clinical Oncology Group Trial (JCOG-0403),” Physics in Medicine and Biology, Vol. 51, No. 21, 2006, 5409-5417.

[1] N. Papanikolaou, E. E. Klein and W.R. Hendee, “Heterogeneity Corrections Should Be Used in Treatment Planning for Lung Cancer?” Medical Physics, Vol. 27, No. 8, 2000, pp. 1702-1704. doi:10.1118/1.1287645

[2] N. Papanikolaou and T.R. Mackie, “Extension of the Convolution/Superposition Based Algorithms to Include Atomic Number Effects,” Medical Physics, Vol. 22, No. 6, 1995, p. 977.

[3] [1]G. Starkschall, A. A. Shiu, S. W. Bujnowski, et al., “Effect of Dimensionality of Heterogeneity Correction on the Implementation of a Three-Dimensional Electron Pencil-Beam Algorithm,” Physics in Medicine and Biology, Vol. 36, No. 2, 1991, pp. 207-227. doi:10.1088/0031-9155/36/2/006

[4] M. K. Woo, D. Scora and E. Webb, “The Regional Monte Carlo Method: A Dose Calculation Method Based on Accuracy Requirement,” Medical Physics, Vol. 25, No. 10, 1998, pp. 1866-1871. doi:10.1118/1.598366

[5] I. Kawrakow, “VMC++, Electron and Photon Monte Carlo Calculations Optimized for Radiation Treatment Planning,” In: A. Kling, F. Barao, M. Nakagawa, L. Tavora and P. Vaz, Eds., Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications: Proceedings of the Monte Carlo 2000 Meeting, Springer, Berlin, 2001, pp. 229-236.

[6] T. R. Mackie, A. F. Bielajew, D. W. Rogers and J. J. Battista, “Generation of Photon Energy Deposition Kernels Using the EGS Monte Carlo Code,” Physics in Medicine and Biology, Vol. 33, No. 1, 1988, pp. 1-20. doi:10.1118/1.598366

[7] A. Ahnesjo and M.-M. Aspradakis, “Dose Calculations for External Photon Beams in Radiotherapy (Topical Review),” Physics in Medicine and Biology, Vol. 44, No. 11, 1999, pp. 99-155. doi:10.1088/0031-9155/44/11/201

[8] M. Nilsson and T. Knoos, “Application of the Fano Theorem in Inhomogeneous Media Using a Convolution Algorithm,” Physics in Medicine and Biology, Vol. 37, No. 1, pp. 1992, 69-83. doi:10.1088/0031-9155/37/1/005

[9] A. Ahnesjo, “Collapsed Cone Convolution of Radiant Energy for Photon Dose Calculation in Heterogeneous Media,” Medical Physics, Vol. 16, No. 4, 1989, pp. 577-592. doi:10.1118/1.596360

[10] R. Mohan, C.-S. Chui and L. Lidofsky, “Differential Pencil Beam Dose Computation Model for Photons,” Medical Physics, Vol. 13, No. 1, 1986, pp. 64-73. doi:10.1118/1.595924

[11] M. R. Sontag, “Photon Beam Dose Calculations in Regions of Tissue Heterogeneity Using Computed Tomography,” Ph.D. Thesis, University of Toronto, Toronto, 1979.

[12] J. W. Wong and R. M. Henkelman, “A New Approach to CT Pixel-Based Photon Dose Calculations in Heterogeneous Media,” Medical Physics, Vol. 10, No. 2, 1983, pp. 199-208. doi:10.1118/1.595294

[13] J. J. Battista, M. B. Sharpe, E. Webb and J. Van Dyk, “A new Classification Scheme for Photon Beam Dose Algorithms,” In: D. D. Leavitt and G. Starkschall, Eds., International Conference on the Use of Computers in Radiation Therapy, XII ICCR, Salt Lake City, Medical Physics Physics Publishing, Madison, 1997, pp. 39-42.

[14] A. L. Boyer, “Shortening the Calculation Time of Photon Dose Distributions in an Inhomogeneous Medium,” Medical Physics, Vol. 11, No. 4, 1984, pp. 552-554. doi:10.1118/1.595526

[15] A. Ahnesjo, M. Saxner and A. Trepp, “A Pencil Beam Model for Photon Dose Calculation,” Medical Physics, Vol. 19, No. 2, 1992, pp. 263-273. doi:10.1118/1.595526

[16] N. Papanikolaou, T. R. Mackie, C. Meger-Wells, et al., “Investigation of the Convolution Method for Polyenergetic Spectra,” Medical Physics, Vol. 20, No. 5, 1993, pp. 1327-1336.

[17] J. D. Bourland and E. L. Chaney, “A Finite-Size Pencil Beam Model for Photon Dose Calculations in Three Dimensions,” Medical Physics, Vol. 19, No. 6, 1992, pp. 1401-1412. doi:10.1118/1.596772

[18] M. B. Sharpe and J. J. Battista, “Dose Calculations Using Convolution and Superposition Principles: The Orientation of Dose Spread Kernals in Divergent X-Ray Beams,” Medical Physics, Vol. 20, No. 6, 1993, pp. 1685-1694. doi:10.1118/1.596955

[19] J. R. Cunningham, “Tissue Inhomogeneity Corrections in Photon Beam Treatment Planning,” Progress in Medical Radiation Physics, Vol. 1, 1982, pp. 103-131. doi:10.1118/1.596955

[20] J. W. Wong and J. A. Purdy, “Review of Methods of Inhomogeneity Corrections,” Advances in Radiation Oncology Physics: Dosimetry, treatment Planning and Brachytherapy, American Institute of Physics, New York, 1992, pp. 887-899.

[21] C. X. Yu and J. W. Wong, “Implementation of the ETAR Method for 3D Inhomogeneity Corrections Using FFT,” Medical Physics, Vol. 20, No. 3, 1993, pp. 627-632. doi:10.1118/1.597010

[22] C.-M. Ma, J. S. Li, T. Pawlicki, et al., “A Monte Carlo Dose Calculation Tool for Radiotherapy Treatment Planning,” Physics in Medicine and Biology, Vol. 47, No. 10, 2002, pp. 1671-1689. doi:10.1118/1.597010

[23] S. Webb and R. P. Parker, “A Monte Carlo Study of the Interaction of External Beam X-Radiation with Inhomogeneous Media,” Physics in Medicine and Biology, Vol. 23, No. 6, 1978, pp. 1043-1059. doi:10.1118/1.597010

[24] N. Papanikolaou, “Dose Calculation Algorithms in the IMRT Era, Radiother,” Oncology, Vol. 61, Supplement 1, 2001, p. S12.

[25] N. Papanikolaou, J. J. Battista, A. L. Boyer, et al., “Tissue Inhomogeneity Corrections for Megavoltage Photon Beams,” AAPM Report No. 85, AAPM TG65, 2004.

[26] A. Gray, L. D. Oliver and P. N. Johnston, “The Accuracy of the Pencil Beam Convolution and Anisotropic Analytical Algorithms in Predicting the Dose Effects Due to Attenuation from Immobilization Devices and Large Air Gaps,” Medical Physics, Vol. 36, No. 7, 2009, pp. 3181-3191. doi:10.1118/1.3147204

[27] A. V. Esch, L. Tillikainen, J. Pyykkonen, et al., “Testing of the Analytical Anisotropic Algorithm for Photon Dose Calculation,” Medical Physics, Vol. 33, No. 11, 2006, pp. 4130-4148. doi:10.1118/1.3147204

[28] B. Kavanagh, M. S. Ding, T. Schefter, et al., “The Dosimetric Effect of Inhomogeneity Correction in Dynamic Conformal ARC Stereotactic Body Radiation Therapy for Lung Tumors,” Journal of Applied Clinical Medical Physics, Vol. 7, No. 2, 2006, pp. 58-63. doi:10.1118/1.3147204

[29] D. Robinson, “Inhomogeneity Correction and the Analytic Anisotropic Algorithm,” Journal of Applied Clinical Medical Physics, Vol. 9, No. 2, 2008, p. 2786. doi:10.1088/0031-9155/51/21/002

[30] T. Nishio, E. Kunieda, H. Shirato, et al., “Dosimetric Verification in Participating Institutions in a Stereotactic Body Radiotherapy Trial for Stage I Non-Small Cell Lung Cancer: Japan Clinical Oncology Group Trial (JCOG-0403),” Physics in Medicine and Biology, Vol. 51, No. 21, 2006, 5409-5417.