Computed tomography radiation dose in a regional survey

Abstract

Purpose To evaluate the patient dose in computed tomography (CT) examinations and contribute to the stablishment of dose reference levels using a dose management system. Material and methods Data from 5 CT hellical multi-slice scanners (16–128 slices) in 3 public hospitals were surveyed (4 Siemens, 1 General-Electric) during 3 months. Three typical examinations were selected: head (1445 cases), thorax (579 cases) and abdomen-pelvis (1055 cases). GE-Dosewatch was used to register patient dose indexes, CTDIvol and DLP, and the technical parameters. The statistical analysis was done in Matlab. Results Both the CTDIvol and the DLP data approximate well to a log-normal distribution function whereas the scanned length fits better to a normal distribution. Median CTDIvol of head scans ranged 33.0–63.8 mGy, thorax 6.7–9.7 mGy and abdomen-pelvis 10.0–12.1 mGy. Median DLP of head scans ranged 527–1162 mGy cm, thorax 218–334 mGy cm and abdomen-pelvis 383–453 mGy cm. We noticed that same CT model scanners use different technical examinations parameters, resulting in dose variations up to 30%. A dose optimization process was initiated to standardize the scanning protocols, thus expecting a dose reduction around 20% in some cases. Patient size selection was not deemed necessary due to the high number of cases per examination, more than 100. A drawback of this massive data is the presence of extreme outliers, and thus data filtering is mandatory. Conclusion Dose management systems provide an efficient tool to overview and optimize radiological dose levels. Disclosure None.