Determination of Effective Dose and Local Diagnostic Reference Level for Abdomen and Pelvis Computed Tomography with and without Contrast Agent

Purpose: The International Commission on Radiological Protection (ICRP) recommends that each community produces its own Diagnostic Reference Levels (DRL), taking into account the diversity of ethnicities, imaging protocols, and equipment types in individual communities. The goal of this examination is to research the DRL for the abdominal-pelvis Computed Tomography (CT) examinations accomplished at our clinical institution. Materials and Methods: The information on 600 patients, recorded by the radiology center from May 1, 2022, to May 1, 2023, has been collected. All scans were performed using a GE Healthcare 16-slice scanner. Four imaging protocols were used for imaging the abdomen and pelvis of patients, including without contrast agent, with oral contrast agent, with contrast agent injection, and triple-phase. The median and seventy-fifth percentile values for the distribution of the CT dose index (CTDIvol in mGy) and dose length product (DLP) parameters have been computed. Results: Effective dose values in the triple-phase ranged from 33.30 to 38.12 ± 0.1 mSv for patients with different DLP values. For scans without and with oral contrast agents, the effective dose ranged from 8.68 to 9.45 ± 0.2 mSv. Scans with contrast agent injection had an effective dose ranging from 10.83 to 11.45 ± 0.1 mSv, based on the total value of DLP. The determined DRLs were as follows: for abdomen and pelvis CT without contrast agent and oral contrast agent, the DRLs were 12 mGy and 605 mGy.cm, respectively. For the abdomen and pelvis CT procedures in the triple-phase, the DRLs were 11 mGy and 2382 mGy.cm, respectively. Finally, for the abdomen and pelvis CT with contrast agent injection protocols, the DRLs were 16 mGy and 1484 mGy.cm, respectively. The maximum Size-Specific Dose Estimate (SSDE) precontrast in the triple-phase protocol was 23.10±0.2 mGy. Conclusion: The proposed DRL values for all imaging protocols, especially the triple-phase, exceed the international guidelines for DRL values in DLP and CTDIvol (mGy). Therefore, methods such as reducing the scan length should be considered to minimize the radiation dose to patients while preserving image quality