Year: 2026 | Month: February | Volume: 13 | Issue: 2 | Pages: 235-243
DOI: https://doi.org/10.52403/ijrr.20260223
CT Number Stability of Plasticine Bolus Based on HU Measurements in 25-Fraction 6 MV Radiotherapy
Datu Sinang Saya1, Eko Hidayanto1, Ngurah Ayu Ketut Umiati1, Tegar Pratama Kayong Wardana1,3, Syarifudin2, Hendra Setiawan2
1Department of Physics, Faculty of Science and Mathematics, Diponegoro University, Semarang, Indonesia.
2Medical physicist at Bali Mandara Regional General Hospital
3Smart Material Research Center, Diponegoro University, Semarang, Indonesia.
Corresponding Author: Datu Sinang Saya
ABSTRACT
This study investigates the Hounsfield Unit (HU) stability of plasticine bolus material during fractionated radiotherapy to evaluate its suitability for clinical application in external beam radiotherapy. A plasticine bolus (10×10 cm², 1 cm thickness) was subjected to 25 fractions of 6 MV photon irradiation using a linear accelerator (LINAC). HU values were measured at baseline and after fractions 5, 10, 15, 20, and 25 using a Canon Aquilion CT-simulator (120 kVp, 300 mAs, 2 mm slice thickness). Dose distribution parameters (minimum, maximum, and mean doses) were calculated using ARIA Treatment Planning System (TPS) at each measurement point. The plasticine bolus demonstrated a baseline HU of 120, increasing to 130 HU (maximum deviation of 10 HU or 8.3%) by fraction 10, with values remaining stable through fraction 25. The peak HU change occurred at fraction 15 (131 HU, representing 9.2% deviation). Corresponding dose variations were minimal: mean dose decreased by 0.11% (from 5035.5 to 5029.8 cGy), minimum dose by 0.43% (from 3751.0 to 3735.0 cGy), and maximum dose by 0.23% (from 5128.5 to 5116.8 cGy). All HU changes remained well below the clinical tolerance threshold of ±20 HU, and dose variations were substantially lower than the 1-2% clinical significance threshold. These findings demonstrate that plasticine bolus maintains adequate HU stability for short-to-medium fractionation protocols (≤25 fractions) when proper quality assurance is implemented, though it exhibited higher HU variability compared to silicone-based alternatives reported in literature.
Keywords: Hounsfield Unit; plasticine bolus; fractionated radiotherapy; dose distribution; treatment planning system; clinical tolerance.
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