Monte Carlo Investigation of Field Size Effects on Central-Axis Dose Distributions (PDD Curves) and Lateral Dose Profiles

Document Type : Research Articles

Authors

Department of Physics, Faculty of Science, Al-Azhar University, Nasr city, Cairo, Egypt.

Abstract

Introduction: After radioactivity and X-rays were first discovered, researchers found that radiation could harm cells by damaging their internal structures, with cancer cells particularly vulnerable to these effects. Today, various advanced machines and methods are employed to enhance the precision of radiation delivery to tumors. Monte Carlo simulation is an excellent method for predict the dose distributions under certain conditions. Therefore, in this study, we aimed to investigate the field size effect on the central dose distributions (PDD Curves), and the lateral profiles of the dose. Method: MC codes, i)- MCBEAM code, ii)- MCSIM code, and iii) MCSHOW code used to simulate 6MV photon beams with 5 different field sizes (10x10cm, 5x5cm, 8x8cm, 15x15cm, and 20x20cm). PDDs and profile curves were compared for each field size. Result: Smaller field sizes (e.g., 5×5 cm) exhibited a lower surface dose compared to larger fields, and the depth of maximum dose dmax shifts slightly deeper as field size increases due to increased scatter contributions. Larger fields (15×15 cm, 20×20 cm) demonstrated a slower dose falloff at deeper depths compared to smaller fields. Conclusion: Monte Carlo calculations confirms that field size significantly impacts PDD curves and affects surface dose. This agreement encouraged us to research with these codes to improve treatment techniques in radiotherapy.

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Asian Pacific Journal of Cancer Prevention
Volume 27, Issue 1
January 2026
Pages 123-128

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History

  • Receive Date: 02 May 2025
  • Revise Date: 18 July 2025
  • Accept Date: 08 January 2026

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