Abstract ID: 16055 Title: Dose distribution of a hip prosthesis phantom in photon beams
Purpose:A hip prosthesis phantom was used to investigate the two-dimensional dose
distribution below the hip prosthesis irradiated by photon beams and to compare measured dose
distribution with calculated one.
Methods:A hip prosthesis phantom included in paraffin was home-made, which was embedded
in an acrylic material. The hip prosthesis consisted of Co-Cr-Mo alloys. With 4cm-thickness
build-up solid water phantom both 6MV and 10MV photon beam of field size 20x20cm were
irradiated on the hip prosthesis phantom. We measured two-dimensional dose distributions with
a two-dimensional ion chamber array I’mRT MatriXX (IBA dosimetry, Schwarzenbruck,
Germany), which were compared with commercial treatment planning system Pinnacle3
(Phillips, Madison, WI). In our study, CT numbers from metal artifacts were corrected using
the density override option in the Pinnacle3.
Results:The dose distribution just behind the prosthesis was severely underestimated in the
Pinnacle3. The dose discrepancy between measured and calculated dose was more significant
for higher energy. For 10MV, there were dose discrepancies over 20% around the prosthesis,
while for 6MV below 20%.
Conclusions:In the clinical aspect there must be more careful considerations on the calculated
dose for patients with hip prosthesis irradiated by photon beam.