Electron beam Therapy at extended diatances
The nominal distance for electron beam treatment is 100cm source to surface distance SSD. However, certain clinical conditions need an extended distance to increase the available irradiated field. the study was performed on an electron beam produced from the Elekta Linear accelerator at four different energies: 6, 8, 10, and 15 MeV, both absolute dose and relative profiles were measured. 1- The absolute dose was measured with Roos Ion Chamber inserted in slap phantom at 100 cm SSD and gradually extended distances (100: 140)cm SSD, then compared to the calculated dose in Elekta Precise treatment planning system. 2- Electron beam fluence was measured with PTW 2D array to get the beam fluence within the irradiated field, evaluate the effect of extension in beam profiles, whether extended distance influence flatness, symmetry, penumbra and how to overcome this effect for suitable coverage when treated at extended distances.
Steps to reproduce
PTW 2D ARRAY examined the horizontal changes due to extended distances. the 2D array placed at the reference depth and beam quality of each energy that was measured upon IAEA published protocol TRS398. the 2D array was inserted in a slap phantom at reference depth, applicaor 10x10 connected to LINAC head, and 100 then the 2D array exposed to monitor uniit to measure the corresponding beam fluence from 100cm SSD to 140 cm SSD at the upcoming sequence (100, 105, 110, 115, 120, 140)cm.