Hounsfield CT-values correction with the imar® software, impacts on dosimetrics calculation for radiation therapy

Abstract

Introduction iMAR® is a software developed by Siemens for the raw data reconstruction acquired with CT scan for dosimetry planification. This software is used in the event of presence of metal object which causes artefacts on the scan images. Purpose Metal artifacts create uncertainty in contours, add time for manual correction, and might lead to inaccuracies in dose calculation. The iMAR® algorithm used for this software must allow a depiction of the Hounsfield Units (HU) values getting closer to the reality, i.e without artefacts. To do that, several tests are conducted to demonstrate the efficiency of this product. Materials and methods Siemens SOMATON Scope 24-slice is used for CT scan. Phantom created in the department of radiotherapy with a lot of inserts. These inserts come to QUASAR™ phantom and CIRS Model 062. We compared several kind of acquisitions with different parameters of reconstructions while alternating the use, or not, of the iMAR algorithm. The dosimetry realized in the TPS Eclipse® to process the treatment plan is based on the HU values calculated in the CT scan acquisition. Therefore an HU values comparison between images with/without iMAR® software will be made to guaranty an optimal treatment. Results The first studies show a significant improvement of the UH values and the result are an optimization and precision of treatments processing. Conclusion Use iMAR® Siemens software can improve quality in the CT scan acquisition to enhanced contouring and more accurate dosimetry of the radiotherapy treatment.