Experimental measurement of entrance skin dose in IMRT and VMAT for cervical cancer in the pelvic region using a female phantom and optically stimulated luminescence dosimeters

Abstract

Author(s): Ahlam Azalmad*, Abour Mohamed, Mohamed Hilal

Purpose: Minimizing radiation-induced skin toxicity while ensuring optimal tumor coverage is a critical challenge in cervical cancer radiotherapy. This study compares Entrance Skin Dose (ESD) and target coverage for Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT), highlighting their implications for radiation protection.

Materials and methods: Eight Optically Stimulated Luminescence (OSL) dosimeters, providing precise point measurements of ESD with high spatial resolution, were placed at clinically relevant anatomical sites on a female anthropomorphic phantom. The phantom underwent a planning CT scan, and IMRT and VMAT plans were simulated in Eclipse using 6 MV photon beams on a Varian TrueBeam linear accelerator. Results: IMRT delivered slightly higher skin doses (0.589 Gy measured vs. 0.566 Gy calculated) compared to VMAT (0.494 Gy measured vs. 0.477 Gy calculated), with an average relative increase of ~0.5%.

Conclusion: VMAT demonstrates lower skin exposure and may be preferable for patients at higher risk of radiation-induced skin toxicity. OSL dosimetry allowed accurate ESD assessment, supporting radiation protection by confirming doses remain within safe limits and showing strong agreement with ICRU Reports 50 and 83.

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