Background: Tube current is an important determinant of radiation dose and image quality in X-ray-based examination. The combined automatic tube current modulation technique (ATCM) enables automatic adjustment of the tube current in various planes ( x-y and z) based on the size and attenuation of the body area scanned. Purpose: To compare image quality and radiation dose of the ATCM with those of a fixed tube current technique (FTC) in CT of the abdomen and pelvis performed with a 16-slice multidetector row CT. Material and Methods: We reviewed 100 patients in whom initial and follow-up CT of the abdomen and pelvis were performed with FTC and ATCM. All acquisition parameters were identical in both techniques except for tube current. We recorded objective image noise in liver parenchyma, subjective image noise and diagnostic acceptability by using a five-point scale, radiation dose, and body mass index (BMI, kg/m²). Data were analyzed with parametric and non-parametric statistical tests. Results: There was no significant difference in image noise and diagnostic acceptability between two techniques. All subjects had acceptable subjective image noise in both techniques. The significant reduction in radiation dose (45.25% reduction) was noted with combined ATCM ( P < 0.001). There was a significant linear statistical correlation between BMI and dose reduction (r = –0.78, P < 0.05). Conclusion: The ATCM for CT of the abdomen and pelvis substantially reduced radiation dose while maintaining diagnostic image quality. Patients with lower BMI showed more reduction in radiation dose.

The aim of this study was to determine the conversion factors for the effective dose (ED) per dose length product (DLP) for various computed tomography (CT) protocols based on the 2007 recommendations of the International Commission on Radiological Protection (ICRP). CT dose data from 369 CT scanners and 13,625 patients were collected through a nationwide survey. Data from 3793 patients with a difference in height within 5% of computational human phantoms were selected to calculate ED and DLP. The anatomical CT scan ranges for 11 scan protocols (adult-10, pediatric-1) were determined by experts, and scan lengths were obtained by matching scan ranges to computational phantoms. ED and DLP were calculated using the NCICT program. For each CT protocol, ED/DLP conversion factors were calculated from ED and DLP. Estimated ED conversion factors were 0.00172, 0.00751, 0.00858, 0.01843, 0.01103, 0.02532, 0.01794, 0.02811, 0.02815, 0.02175, 0.00626, 0.00458, 0.00308, and 0.00233 mSv∙mGy⁻¹∙cm⁻¹ for the adult brain, intra-cranial angiography, C-spine, L-spine, neck, chest, abdomen and pelvis, coronary angiography, calcium scoring, aortography, and CT examinations of pediatric brain of <2 years, 4–6 years, 9–11 years, and 13–15 years, respectively. We determined ED conversion factors for 11 CT protocols using CT data obtained from a nationwide survey in Korea and Monte Carlo-based dose calculations.

Background: In 2021, the Korean government proposed a new CT diagnostic reference level. This study performed a nationwide survey and developed new DRLs and AD for 13 common CT examinations. We compared other countries’ DRLs for CT examinations. Methods: This study investigated the CTDI_vol and DLP of the 12 types of CT protocols for adults and brain CT protocol for pediatrics. A total of 7829 CT examinations were performed using 225 scanners. We defined the DRLs values in the distribution of radiation exposure levels to determine the nationwide patient dose and distribution status of the dose. Results: This study showed that the new Korean national CT DRLs are slightly higher or similar to those of previous surveys and are similar or lower than those of other countries. In some protocols, although the DLP value increased, the CTDI_vol decreased; therefore, it can be concluded that the patient’s dose in CT examinations was well managed. Conclusions: The new CT DRLs were slightly higher than or similar to that of the previous survey and were evaluated to be similar or lower than CT DRLs of other countries. These DRLs will be used for radiation optimization and effective dose calculation for an individual.