Does the amount of tagged stool and fluid significantly affect the radiation exposure in low-dose CT colonography performed with an automatic exposure control?

Abstract

Objective: To determine whether the amount of tagged stool and fluid significantly affects the radiation exposure in low-dose screening CT colonography performed with an automatic tube-current modulation technique. Methods: The study included 311 patients. The tagging agent was barium (n∈=∈271) or iodine (n∈=∈40). Correlation was measured between mean volume CT dose index (CTDI vol ) and the estimated x-ray attenuation of the tagged stool and fluid (ATT). Multiple linear regression analyses were performed to determine the effect of ATT on CTDI vol and the effect of ATT on image noise while adjusting for other variables including abdominal circumference. Results: CTDI vol varied from 0.88 to 2.54 mGy. There was no significant correlation between CTDI vol and ATT (p∈=∈0.61). ATT did not significantly affect CTDI vol (p∈=∈0.93), while abdominal circumference was the only factor significantly affecting CTDI vol (p∈