DIAGNOSTIC REFERENCE LEVELS FOR CARDIAC CT ANGIOGRAPHY IN AUSTRALIA.

This study aims to assess patient radiation dose from cardiac computed tomography angiography (CCTA) with the aim of proposing a national diagnostic reference levels (NDRLs) for CCTA procedures in Australia. A questionnaire was used to retrospectively gather baseline information related to CCTA scanning and patient parameters in CT centres across the country. The 75th percentile of both volumetric CT dose index (CTDIvol) and dose length-product (DLP) was used as DRL values for CCTA. A DRL for CT calcium scoring test was also determined. NDRLs were compared with international published data. Data sets of 338 patients from nine CT centres were used for analysis. The CCTA DRL for the CTDIvol and the DLP were 22 mGy and 268 mGy cm, respectively. The CT calcium scoring test DRL for DLP was 137 mGy cm. The DRL values for CCTA in Australia have been recommended for the first time. DRLs are lower than those in most published studies due to the implementation of dose-saving technologies such as prospective ECG-gated mode and iterative reconstruction algorithms. Considerable variations remain in patient doses between hospitals for the most frequently used CCTA protocols, indicating the potential for DRLs to prompt dose optimisation strategies in CT facilities.