Exploring the relationship between intravenous contrast and radiation doses associated with head, chest, and abdomen CT at 43 hospitals in 18 countries

Purpose: Multiphase, contrast-enhanced CT (CECT) exams are important contributors to high radiation doses. We performed a multicenter, international study to explore the relationship between the administration of intravenous contrast media (ICM), scan factors, and radiation doses associated with CECT of the head, chest, and abdomen-pelvis (AP).

Methods/Materials: Our international (n= 18 countries), multicenter (n=43 sites) study (ConRad) had two parts. Part 1: Redcap survey on information related to CT and ICM brand and protocols for head, chest, and AP CT. Part 2: Information on 3,258 patients (18-96 years; M: F 1654:1604) who underwent CECT for a routine head (n=456), chest (n=528), AP (n=599), head CT angiography (H-CTA) (n=539), pulmonary embolism (CTPE, n=599) and liver protocols CT (LCT, n=537) at 43 sites across 18 countries between January 2020 to April 2022. We recorded: hospital name, patient age, gender, weight, height, body mass index [BMI], clinical indications, scan parameters (number of scan phases, kV), contrast information (concentration, volume, flow rate, and delay) and dose indices (CTDIvol and DLP).

Results: Most routine chest (58.4%) and AP (68.7%) CECT exams were performed with 2-4 scan phases with fixed scan delay (chest 71.4%; AP 79.8%, liver CECT 50.7%) following ICM administration. Most sites did not change kV across different patients and scan phases; most CECT protocols were performed at 120-140 kV (83%, 1979/2685). There was no significant difference between radiation doses associated with non-contrast (CTDIvol 23±20mGy; DLP 646±428mGy.cm) and post-contrast phases (22±46mGy; DLP 654±473mGy.cm) regardless of applied protocol. Sites that used bolus tracking for chest and AP CECT had lower CTDIvol than sites with fixed scan delays (p < 0.001). Of the 38 sites, 28 (73%) used weight-based adjustment of ICM, whereas 10 (26.3%) had fixed ICM for chest and AP CECT. There was a poor correlation between BMI and CTDIvol with underweight patients (BMI < 18.5) receiving higher doses than overweight and obese BMI patients.

Conclusions: Unexplained variations in the use of intravenous contrast and radiation doses lead to higher radiation doses and contrast media use in underweight patients.