Contrast-specific conversion factor for accurate radiation dose estimation in contrast-enhanced abdominal computed tomography

Objectives: The objective of the study is to determine the contrast-specific conversion factor (cCF) based on the dose differences between non-enhanced computed tomography (NECT) and contrast-enhanced CT (CECT) in abdominal imaging, with the aim of improving the accuracy of radiation dose estimation in contrast-enhanced examinations. Material and Methods: The study included 33 adult patients who underwent both NECT and CECT. CECT image acquisition commenced 80 s after the start of iodinated contrast medium injection. A Monte Carlo simulation tool was used to estimate the radiation dose delivered to each patient during NECT and CECT. Organ doses for the liver, spleen, and both kidneys were measured using 120-kVp images. The cCF was calculated as the ratio of the organ dose in CECT to that in NECT. The cCF values are dependent on the scan protocol-, CT vendor-, and X-ray photon energy. Results: The mean organ doses during NECT were 10.45 mGy for the liver, 11.19 mGy for the spleen, and 11.47 mGy for both kidneys. During CECT, these values increased to 15.83 mGy, 17.56 mGy, and 20.75 mGy, respectively. The mean cCFs of CECT relative to NECT were 1.52 for the liver, 1.83 for the spleen, and 1.87 for both kidneys. Conclusion: Applying the cCF to NECT-based dose estimates enables more accurate assessment of radiation exposure in CECT examinations.