Speaker
Level for award<br> (Hons, MSc, <br> PhD, N/A)?
N/A
Apply to be<br> considered for a student <br> award (Yes / No)?
No
Would you like to <br> submit a short paper <br> for the Conference <br> Proceedings (Yes / No)?
Yes
Abstract content <br> (Max 300 words)<br><a href="http://events.saip.org.za/getFile.py/access?resId=0&materialId=0&confId=34" target="_blank">Formatting &<br>Special chars</a>
During irradiation of malignancies in the hip region with external megavoltage photon beams, the presence of metallic prostheses could partially shield the beam at the target and alter the dose distribution. This may cause a dramatic difference in treatment outcome. This study investigates the magnitude of 6 MV photon beam dose perturbations caused by unilateral titanium prosthesis and were measured with Gafchromic EBT2 film in a pelvic phantom made out of nylon slices. Dose perturbations were measured and compared using dose maps and beam profiles for a range of field sizes between 3×3 and 10×10 cm^2. The magnitude of these perturbations were quantified as dose correction factors, DCFs which is defined as the ratio of the dose influenced by the prosthesis and the unaltered beam. A DCF of unity marks the margin between dose enhancement (where DCF > 1.0) and dose reduction (where DCF < 1.0). DCFs above unity were observed on the proximal (beam entry) side of the prosthesis while DCFs below unity occurred in the distal region (behind the prosthesis). For the studied field sizes maximum DCFs ranged between 1.251±0.003 and 1.283±0.019. Minimum DCFs ranged between 0.746±0.010 and 0.810±0.014. The DCFs on the proximal side of the prosthesis drop off rapidly with distance from the proximal prosthesis-nylon interface. The results of the study indicate that at the nylon-prosthesis interface, about 25% of dose enhancement is due to electron backscatter from the prosthesis and at least 19% of dose reduction behind the prosthesis is due to photon attenuation.
Please indicate whether<br>this abstract may be<br>published online<br>(Yes / No)
Yes
Main supervisor (name and email)<br>and his / her institution
Dr Freek Du Plessis DuPlessisFCP@ufs.ac.za
University of the Free State,Bloemfontein
