A Study On Analyzing The FF And FFF Photon Beam Dose Distribution In Vac-Lok Immobilization Device In Our Radiotherapy

Abstract

Immobilization devices plays a pivotal role in radiotherapy for treating various carcinomas. Due to the patient comfort and convenience, vaclok is one of the most frequently using immobilization device in radiotherapy for the treatment of cancer now a day especially for the thoracic region. The aim of the present study was to analyzes the photon dose distribution of flattening filter and free flattening filters beam in blue bag vac-lok immobilization devices in our radiotherapy department. The study was done with the help of parallel plate chamber and sp34 phantom for the surface dose calculation, and pdd and beam angle attenuation done by using Farmer chamber. The d_max of all photon energy were shifted up due to the presence of vaclok devices such as 1.6 cm to 0.8 cm,2.2 cm to 1.5 cm, for 6,10, MV, and 1.8cm to 1.0 cm,2.6cm to 1.8 cm for 6 &10 MV FFF beam. It was also observed that, the surface dose increased relatively due to the presence of vaclok irrespective of the all energy used, due to the presence of 10cm vacuum bag for the energies 6MV, 10MV, 6MVFFF and 10MVFFF were 46.98%, 54.25%,43.34% and 48.10% respectively. Similarly, for 20cm the relative dose increase was up to 49.21%, 57.46%, 45.90% and 51.17% for the energies 6 &, 10MV, and 6 & 10MVFFF respectively. The gantry angle attenuation for the 10cm vacuum cushion, maximum difference was found at the angle of 40^◦for 6MV, 10MV, 6MVFFF and 10MVFFF energies and corresponding difference noted was 3.91%, 3.19%,3.86%, 3.11%. The calculation was also done for the indexing lath attenuation on the vaclok, For the vacuum cushion of 10cm thickness with indexing lath, attenuation was found maximum at the angle of 40^◦ with the values 7.01%, 6.00%, 7.05% and 5.60% for the energies 6 &10MVand 6 & 10MVFFF respectively. The results clearly show that the doses were attenuated with the introduction of vaclok and it varies with thickness as well as energy.