The Impact of Metal Artifact Reduction in Estimation of Dose Distribution in ISOgray Treatment Planning Software

Some cancer patients who receive radiation therapy have metal objects in their body. There is a difference between atomic numbers of these metal objects and body tissues. This creates artifacts in images and creates large difference in CT numbers and errors in the calculations. This study was performed to evaluate the effect of correcting metal artifact on images and compare the absorbed dose estimated by ISOgray treatment planning system (TPS) and measurement. Homogeneous cylindrical phantom was prepared from Perspex material to simulate human body conditions. Cavities were created for Farmer dosimeter and titanium metal rods acting as prosthesis. CT images of phantom were acquired in the presence and absence of metal rods. The correction of metal artifact was performed using Metal Detection Technique (MDT) and CT control softwares. Dose calculation was done at the phantom center for 100 MU at the photon mode with the energies of 6, 10 and 15 MV at ISOgray TPS. The results were compared with Farmer dosimeter. The results show that there is no significant difference in absorbed dose calculated for different images corrected using two softwares by ISOgray TPS. The lowest and highest errors are 0.1% and 1.09% related to the images corrected by MDT software with the slice thickness of 3.0 cm and the distance of 2.5 cm and photon energies of 6 and 15 MV, respectively. The correction of artifacts in CT images does not have a significant effect on the dose calculated by ISOgray.