Abstract

Purpose: The aim of this study was to evaluate dosimetric differences between pencil beam convolution (PBC) algorithm and anisotropic analytical algorithm (AAA) calculations in patients with lung and esophageal cancers. Methods : The existing plans calculated with PBC for 60 patients treated in 2012 were recalculated with AAA maintaining the same beam geometry and dose monitor units. For these plans, dose prescription ranges were 41.4 Gy to 56.0 Gy for esophageal cancers and 50.0 Gy to 64.0 Gy for lung cancers. Dosimetric variables were the 95% PTV coverage, mean PTV dose, maximum spinal cord dose, lung V 5Gy , and lung V 20Gy . Results: The 95% PTV coverage’s for both lung and esophageal tumors were reduced when recalculated with AAA. Maximum spinal cord doses for lung cancer patients were reduced by 0.7 Gy and by 0.3 Gy for esophageal cancer patients on AAA. On the other hand, lung V 5Gy had 3.5% increase for both lung and esophageal cancer patients on AAA, whereas lung V 20Gy increased by 1.5% also on AAA for esophageal cancer patients. Conclusion : These clinical results confirm the differences between AAA and PBC algorithms as observed in phantom dosimetric studies, and give an indication of the clinical implications of changing from one calculation algorithm to another. --------------------------------------- Cite this article as: Amankwaa-Frempong E, Vernimmen F, Blay S, Ezhilalan R. Irradiation of lung and esophagus tumors: A comparison of dose distributions calculated by anisotropic analytical algorithm and pencil beam convolution algorithm, a retrospective dosimetric study. Int J Cancer Ther Oncol 2014; 2(2):020210. DOI: 10.14319/ijcto.0202.10

Highlights

  • Radical radiotherapy requires the calculated absorbed dose to be delivered accurately in order to achieve tumor control.[1, 2] In terms of treatment planning calculations; uncertainty in the dose calculation should be kept to a minimum in order to achieve this maximal tumor control

  • For lung tumors from (Table 1) the maximum and mean doses to the planning target volume (PTV) as calculated with Analytical Algorithm (AAA) were all lower as compared to Pencil Beam Convolution (PBC) dose calculations

  • The 95% PTV coverage was lower (84.5%) with AAA, with a difference of the median values of 10.5% as compared to PBC (p < 0.001)

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Summary

Introduction

Radical radiotherapy requires the calculated absorbed dose to be delivered accurately in order to achieve tumor control.[1, 2] In terms of treatment planning calculations; uncertainty in the dose calculation should be kept to a minimum in order to achieve this maximal tumor control. The lung being a heterogeneous tissue creates difficulties in this regard.[3] With the exception of Monte-Carlo simulation, which has been shown to be closest to reality for dose calculation. Corresponding author: Emmanuel Amankwaa-Frempong; Directorate of oncology, Komfo Anokye Teaching Hospital, P.O. BOX KS 1934, Kumasi, Ghana Due to long calculation time with Monte-Carlo makes it impracticable to be used routinely in the current treatment planning systems.[4]

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