# Feasibility study of skin dosimetry with TLD sheets for measuring the effect of 3D printed bolus in radiotherapy

## TL;DR

This study explores using TLD sheets to measure skin doses during radiotherapy, especially when using 3D-printed bolus materials on uneven surfaces.

## Contribution

The study demonstrates the feasibility of TLD sheets for skin dosimetry on irregular surfaces and compares them with 3D-printed bolus materials.

## Key findings

- TLD sheets can be used for skin dosimetry on uneven surfaces due to their flexibility and thinness.
- The error between TLD sheet measurements and treatment plan doses varied significantly depending on the dose calculation method.
- Surface dosimetry with TLD sheets is feasible even on complex anatomical shapes like a head phantom.

## Abstract

The thermoluminescence dosimeter (TLD) sheet is a measurement device coated with manganese‐doped LiB3O5 in sheet form. The sheet is 0.2‐mm thick and flexible. Hence, it can fit and be installed on irregular surfaces. The current study aimed to evaluate the feasibility of measuring patient surface doses during radiation therapy using TLD sheets. Further, the surface doses when using a three‐dimensional (3D) printed bolus were compared. First, calibration of the between TLD sheet measurements and the irradiation doses was performed. Second, dose calculations and TLD sheet measurements were compared to evaluate the error between treatment planning system (TPS) dose calculations and surface dose measurements. Finally, the TLD sheet was fitted to the head phantom to measure the surface dose at the uneven areas under two conditions (with a commercial [CM] bolus and a 3D‐printed bolus). Based on the error from the dose calculation algorithm and the difference between the TLD sheet thickness and the dose grid size or evaluation structure volume, the differences between the TLD sheet measurements and the treatment plan doses were up to 68.6% for the X‐ray collapsed cone convolution (CCC) method and up to 8.4% for the electron beam Monte Carlo (MC) method. Based on the results of the surface dosimetry of the head phantom, the application of surface dosimetry, particularly skin dosimetry, even on uneven body surfaces, can be feasible.