MDCT Angiography of the Pulmonary Arteries: Influence of Iodine Flow Concentration on Vessel Attenuation and Visualization

Our objective was to assess the influence of iodine flow concentration on attenuation and visualization of the pulmonary arteries in thoracic MDCT angiography. One hundred consecutive patients who were referred to our department with suspected acute pulmonary embolism underwent MDCT angiography of the pulmonary arteries either with 120 mL of standard contrast medium (300 mg I/mL) (group A) or with 90 mL of high-concentration contrast medium (400 mg I/mL) (group B). The contrast medium was injected at a flow rate of 4 mL/sec. The scan delay was determined using a semiautomatic bolus-tracking system in all examinations conducted with the same scanning parameters. Quantitative analysis was performed by region-of-interest measurements along the z-axis to compare the attenuation profiles of the two groups. Attenuation of the fourth-, fifth-, and sixth-order arteries was assessed visually for differences between the two groups. The mean enhancement along the z-axis was 268 +/- 56 H in group A and 344 +/- 108 in group B. The difference of 76 H was statistically significant (p < 0.001). The attenuation profile was similar in both groups. The detection rate of fifth- and sixth-order arteries was significantly higher in group B than in group A (94% compared with 91% and 72% compared with 60%, respectively, p < 0.01). Use of a high flow concentration of iodine in MDCT angiography of the pulmonary arteries significantly increases attenuation of the pulmonary arteries, thereby improving visualization of subsegmental pulmonary arteries.