Evaluation of the dosimetric effects of fluid-containing diapers on radiation dose using a 6 MV Linear Accelerator

Purpose: The use of diapers as dressings to contain profuse bleeding in indigent late-stage cancer patients undergoing radiotherapy has been observed. When saturated with fluid, the absorbent material of the diaper may act as an unintended bolus and alter dose distribution. Findings from this study aim to improve treatment accuracy in clinically relevant scenarios and inform material considerations in resource-limited settings. Methods: Dose measurements were taken using a Farmer chamber in a slab, with a 10x10 cm² field size at 100 SSD. Two types of diapers, based on their material, were evaluated: one with a common absorbent material and the other with a super absorbent polymer (SAP) at different fluid volumes of saline solution with the same ionic strength as blood. The doses were recorded, and the percentage differences from the base dose were analyzed and compared. Results: Results show that as the fluid volume absorbed by both types of diaper increases, the percentage difference to the dose with the slab only also increases. However, there is a threshold volume where these differences plateau due to the diaper being saturated. Increasing differences greater than 5% in dose percentage were also observed between dry and wet diapers. Around 1% difference between the changes in dose between the two types of diaper were determined. The differences get smaller as both types of diaper get saturated while noticeable differences were observed at certain volume range where the diaper with SAP have lower change in dose due to the activation of gel crystals accompanied with air gaps in between. Conclusion: In general, these findings show that it is important to consider the reproducibility of the fluid-absorption state of diaper dressings, as this can lead to dose uncertainty of >5% during radiotherapy treatment.