Dosimetric investigation of the effect of implant materials on penumbra and out of field dose in small radiation fields

In this study, computerized tomography (CT) images of implant-containing phantoms were corrected with the commercial artifact reduction tool of Metal Artifact Reduction for Orthopedic Implants (O-MAR). In small radiation fields, out-of-field dose and penumbra values were calculated by Eclipse treatment planning system on O-MAR corrected and uncorrected CT images. In the first stage of the study, an accurate and precise reference radiochromic dosimetry system was designed to compare the calculations with the measurements. As a result of the comparisons, it was found that there was an absolute error changing between 4.9% and 30.3% at the interfaces of the implant materials at the center of the field and the errors were decreased with O-MAR. Anisotropic Analytical Algorithm (AAA) and Acuros XB (AXB) calculations on O-MAR corrected images yielded an acceptable level of accuracy (1 mm and 2% error). However, for AXB calculations, in cases where O-MAR was not used, it was found that there were absolute errors up to 8% in out-of-field doses. There were also large errors (in the order of cm) in penumbra calculations. Keywords: Radiochromic Film Dosimeter, İmplant Materials, Anisotropic Analytical Algorithm (AAA), Acuros XB (AXB), Small Radiation Fields