Akademik Veri Yönetim Sistemi
3rd European Congress of Medical Physics, 17 - 19 Haziran 2021, ss.84-85
Purpose: Skin surface is the target for total body irradiation (TBI). In megovoltage irradiation, bolus is used to increase the surface dose. In this study, it was aimed to investigate necessity of bolus for TBI using Tomotherapy device.
Material and Methods: Arms and legs were added to the male phantom using rice to simulate the whole body geometrically. The male phantom with arms and legs was immobilized by vacuum bed and 3 mm CT images were received using Philips Big Bore CT with and without the bolus. CT images were received as upper and lower part of the body and used for contouring in the treatment plans. Entire body, lungs, lens, and kidneys were contoured with 3 mm margin and PTV is created using MIM software. Treatment plan prepared given 2Gy per fraction in Volo therapy planning system. 15 numbers of Thermoluminescent dosimeter (TLD)s were placed to skin line on the phantom. The measurements were repeated three times with and without bolus and averaged. The surface doses measured using TLDs with and without bolus were compared.
Results: Measured skin doses for with and without bolus are; right lens= 0.49-1.35 Gy, left lens= 0.52-1.05 Gy, head midpoint=1.88-2.25 Gy, thyroid=1.93-2.23 Gy, right lung= 1.90-2.08 Gy, between lungs=1.83-2.20 Gy, left lung=1.86-2.23 Gy, right kidney=1.82-2.11 Gy, between kidneys=1,87-2.31 Gy, left kidney= 1.84-2.17 Gy, right hip=1.84-2.25 Gy, left hip= 1.89-2.21 Gy, right leg=1.96-2.18 Gy, left leg=1.90-2.38 Gy, between legs=1.91-2.34 Gy.
Conclusions: As expected, using bolus increased skin dose. It was seen that measured skin doses were not under 90% of PTV dose without bolus which is enough for skin dose. If a special condition to increase skin dose is not needed, it is not necessary to use bolus in Tomotherapy treatments.
Key Words: Helical Tomotherapy, skin dose, TLD, bolus.