[OA138] Organ dose estimate in CT exams: Inter-comparison of four commercial software and characterization of the main CT procedures used in asst Niguarda (Milan, Italy)

• Published in: Physica medica 2018-08, Vol.52, p.53-53
• Main Authors: Mattia, Cristina De, Rottoli, Federica, Sutto, Marina, Colombo, Paola Enrica, Pola, Andrea, Torresin, Alberto
• Format: Article
• Language: English
• ISSN: 1120-1797; 1724-191X
• DOI: 10.1016/j.ejmp.2018.06.210

To compare organs dose evaluation from different commercial software and to characterize the main CT procedures of our hospital to provide data for radiation risk estimation. We collected the information regarding the exposure for the main CT procedures used in our hospital through the RDIM system Nexo[DOSE]® (Bracco, Italy). We analysed the main CT protocols and clustered them in macro-groups, considering scan region and phases number. For each group, we defined a stylized protocol, which summarizes the most common exam features and mean dosimetric parameters, so that it can represent the whole macro-cluster. In the stylized protocol, some CT parameters were set equally to the most frequent values (axial/spiral mode, voltage, collimation, pitch, slice thickness), while the remaining were defined as the median values (mAs, CTDIvol, DLP, scan length). The scan region for each phase was deduced from the CT images of a patients’ sample under the specific procedure. Then, we calculated organ dose using four commercial software: CT-Expo, NCICT, NCICTX and Virtual Dose. Each software uses its own phantom family. CT-Expo uses the first generation of computational mathematical phantoms. NCICT, NCICTX and Virtual Dose use a hybrid-voxel phantom, more realistic and, for the last two software, adaptable to the patient habitus. Starting from about 35000 CT exams and 595 protocols, we obtained 13 macro-groups. In comparison with the mean value, the average range of dose values from different software is 25% for organs inside the scan region and 80% for organs partially irradiated. CT-Expo is the only software that shows dependence from collimation, pitch, slice thickness and scanner model. For the others software, the only parameters affecting organ dose calculation are voltage and CTDIvol. In this study, the discrepancies obtained changing voltage are within 15% for all software. On the other hand, the scan length is the primary source of variability in the dose calculation. Organ dose estimate is the first step to calculate effective dose and to evaluate radiation risk: a deep and critical interpretation of the results is necessary since the values range can cause a large variation in final estimate.