A method to quantify and assess the dosimetric and clinical impact resulting from the heterogeneity correction in radiotherapy for lung cancer
Purpose: The aim of this study was to propose a method to quantify and assess the differences in dose computations using heterogeneity correction algorithms for the planning target volumes and organs at risk.
Methods: Six patients with lung cancer treated with 3-dimensional conformal radiation therapy were included and analysed. Dose calculations were performed using the pencil beam convolution (PBC) algorithm without heterogeneity correction and the Modified Batho method (PBC-MB) with heterogeneity correction. For each patient, 3 treatment plans were generated using exactly the same beam configuration. In plan 1, the dose was calculated using the PBC algorithm. In plan 2, the dose was calculated using the PBC-MB. In plan 3, the dose was calculated using the PBC-MB method but with the same number of monitor units obtained from plan 1. To evaluate the treatment plans computed by the PBC and PBC-MB, the monitor units, dose at the isocenter, spatial isodose distribution, dose volume histograms, conformity index, homogeneity index, planning target volumes conformity index, and geometrical index were compared. A statistical analysis was carried out using Wilcoxon signed rank test.
Results: The PBC-MB method in plan 2 produced a lower number of monitor units than in plan 1 using PBC algorithm (p < 0.001). Dosimetric parameters derived from the dose volume histograms were higher for the planning target volumes and organs at risks using PBC-MB method for plans 2 and 3 when compared to plan 1. There was no significant difference for all the quality indices between plan 1 and plan 2, (p > 0.05), but a significant difference for the geometric index between plans 2 and 3 (p = 0.002) was observed.
Conclusion: The risks related to the modification from the homogeneity plan to the heterogeneity plan were the reduction of delivered dose in monitor units for the planning target volumes and the increment of the dose to the organs at risk. We suggest the adaption in the dose prescriptions when switching the dose calculation algorithm from the PBC to PBC-MB.
Cite this article as: Chaikh A, Giraud J, Balosso J. A method to quantify and assess the dosimetric and clinical impact resulting from the heterogeneity correction in radiotherapy for lung cancer. Int J Cancer Ther Oncol 2014; 2(1):020110.
Morgan AM, Knoos T, McNee SG, Evans CJ, Thwaites DI. Clinical implications of the implementation of advanced treatment planning algorithms for thoracic treatments. Radiother Oncol 2008; 86: 48–54.
Knoos T, Wieslander E, Cozzi L, Brink C, Fogliata A, Albers D, Nystrom H, Lassen S. Comparison of dose calculation algorithms for treatment planning in external photon beam therapy for clinical situations. Phys Med Biol 2006; 51: 5785–5807.
Task Group No. 65, the Radiation Therapy Committee of the American Association of Physicists in Medicine. Tissue inhomogeneity corrections for MV photon beams. Madison, WI: Medical Physics Publishing 2004.
Gray A, Oliver LD, Johnston PN. 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. Med Phys 2009; 36: 3181-91.
Rana S, Pokharel S. Verification of dose calculation algorithms in a multi-layer heterogeneous phantom using films. Gulf J Oncolog 2013; 1:63-9.
Narabayashi M, Mizowaki T, Matsuo Y, Nakamura M, Takayama K, Norihisa Y, Sakanaka K, Hiraoka M. Dosimetric evaluation of the impacts of different heterogeneity correction algorithms on target doses in stereotactic body radiation therapy for lung tumors. J Radiat Res 2012; 53: 777-84.
Ahnesjo A, Aspradakis MM. Dose calculations for external photon beams in radiotherapy. Phys Med Biol 1999; 44: R99–155.
Batho HF. Lung corrections in cobalt 60 beam therapy. J Can Assoc Radiol 1964; 15: 79-83.
El-Khatib E, Battista JJ. Improved lung dose calculation using tissue-maximum ratios in the Batho correction. Med Phys1984; 11: 279–286.
Thomas SJ. A modified power-law formula for inhomogeneity corrections in beams of high-energy x rays. Med Phys 1991; 18: 719 -723.
Lu L. Dose calculation algorithms in external beam photon radiation therapy. Int J Cancer Ther Oncol 2013; 1: 01025.
ICRU Report No. 50. Prescribing, Recording and Reporting Photon Beam Therapy.International Commission on Radiation Units and Measurements, Bethesda, Maryland 1993.
ICRU Report No. 62. Prescribing, Recording and Reporting Photon Beam Therapy supplement to ICRU Report 50, International Commission on Radiation Units and Measurements, Bethesda, Maryland 1999.
Feuvret L, Noel G, Nauraye C, Garcia P, J-Mazeron J. Conformal index and radiotherapy. Cancer Radiother 2004; 8: 108–119.
Lomax NJ, Scheib SG. Quantifying the degree of conformity in radiosurgery treatment planning. Int J Radiat Oncol Biol Phys 2003; 55:1409–19.
Wong JW, Purdy JA. On methods of inhomogeneity corrections for photon transport. Med Phys 1990; 17: 807-14.
Hedin E, Back A. Influence of different dose calculation algorithms on the estimate of NTCP for lung complications. J Appl Clin Med Phys 2013; 14: 127-39.
Seppala J, Suilamo S, Kulmala J, Mali P, Minn H. A dosimetric phantom study of dose accuracy and build-up effects using IMRT and RapidArc in stereotactic irradiation of lung tumours. Radiat Oncol 2012; 7: 79.
Herman Tde L, Hibbitts K, Herman T, Ahmad S. Evaluation of pencil beam convolution and anisotropic analytical algorithms in stereotactic lung irradiation. J Med Phys 2011; 36: 234-238.
Rana S, Rogers K, Pokharel S, Cheng C. Evaluation of Acuros XB algorithm based on RTOG 0813 dosimetric criteria for SBRT lung treatment with RapidArc. J Appl Clin Med Phys 2014; 15: 4474.
Herman Tde L, Gabrish H, Herman TS, Vlachaki MT, Ahmad S. Impact of tissue heterogeneity corrections in stereotactic body radiation therapy treatment plans for lung cancer. J Med Phys 2010; 35: 170–173.
Rana S. Clinical dosimetric impact of Acuros XB and analytical anisotropic algorithm (AAA) on real lung cancer treatment plans: review. Int J Cancer Ther Oncol 2014; 2: 02019.
Mavroidis P. Clinical implementation of radiobiological measures in treatment planning. Why has it taken so long? Int J Cancer Ther Oncol 2013; 1:01019.
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