Calculation and measurement of doses in the surface layers of a phantom when using Tomotherapy

Abstract

Background

The calculation and measurement on the surface of the skin presents a significant dosimetric problem because of numerous factors which have an influence on the dose distribution in this region.

Aim

The overall aim of this study was to check the agreement between doses measured with thermoluminescent detectors (TLD) during tomotherapy photon beam irradiation of the skin area of a solid water cylindrical phantom with doses calculated with Hi-Art treatment planning system (TPS).

Material and Method

The measurements of the dose were made with the use of a solid water cylindrical phantom - Cheese Phantom. Two bolus phantoms were used: 5mm and 10mm Six different planning treatments were generated. The doses were measured using TL detectors.

Results

In the case of a tumor located near the surface of the skin, the mean dose for 0.5cm bolus was - 1.94Gy, and for 1cm bolus - 2.03Gy. For the tumor located inside the phantom and organ at risk on the same side that TL detectors, for a 0.5cm bolus, mean dose was 0.658Gy, and for a 1cm bolus, 0.62Gy.

Conclusion

The analysis of results showed that the relative percentage difference between measured and planned dose in the field of irradiation was less than 10%, while the largest differences were on the board of the field of radiation and outside of the field of irradiation, where the dose was 0.08Gy to 1Gy.