Establishment of regional diagnostic reference level for CT planning of breast cancer and comparing them with international values

Background: All over the world, Computed Tomography (CT) scan is used as an essential method in radiation therapy treatment planning. Ionizing radiation for the medical exposures should follow principle "As Low as Reasonably Achievable" (ALARA) to reduce the dose. The objective of this study is to establish a Diagnostic Reference Level (DRL) for breast Computed Tomography planning (CTp) and compare it with other DRLs because there are no dose guidelines for breast cancer CTp in Iran. The established DRL can be used for dose optimization in CT planning. Materials and Methods: We surveyed six RT centers in Tehran and collected data from patients with breast cancer, who were of average size, regarding the volume Computed Tomography Dose Index (CTDIvol), the dose length product (DLP), the dose parameters, the scan length, the thickness of the slices, and the use of automated exposure control (AEC). DRLs were calculated for each dose descriptor using the rounded 75th percentile of the distribution of means. Results: Data were collected on a total of 90 breast cancer CT localization scans from six CT centers. Significant variation was observed in mean DLP and mean CTDIvol among centers (p value < 0.0001). Moreover, mean mAs and scan length significantly differed across centers (p < 0.0001). Calculated DRLs for breast localization are 296.29 mGy cm and 6.64 mGy for DLP and CTDIvol, respectively which were lower compared with other studies conducted in this field. Conclusion: There were differences in doses used for breast CT planning among centers. DRLs were proposed for dose optimization and patient radiation protection in CT planning.