CT pulmonary angiography and CT venography: factors associated with vessel enhancement

The objective of our study was to determine factors associated with enhancement on CT pulmonary angiography and CT venography.

Two hundred forty-two cases (83 men and 159 women; mean age, 63 years; age range, 21-92 years) underwent CT pulmonary angiography using a bolus-tracking technique; 189 cases subsequently underwent CT venography 3 minutes after the start of the contrast injection. Two different amounts of nonionic iodine contrast medium were administered: patients weighing > 50 kg who were undergoing both CT pulmonary angiography and CT venography received 450 mg I (group B), whereas all other patients received 300 mg I (group A). The enhancement of vessels was subjectively estimated using a four-point scale, and attenuation values were measured at predetermined levels. Multiple regression analyses were performed with attenuation as the dependent variable and patient age, sex, and weight; amount of contrast medium; scanning delay; and presence of embolism as the independent variables.

The scanning delay for CT pulmonary angiography ranged from 10 to 31 seconds (mean, 19 seconds; SD, 3.3). Subjective estimates of enhancement quality on CT venography were significantly better for group B than for group A (p < 0.001). Multiple regression analyses revealed that body weight and age were the only significant and consistent independent variables associated with enhancement of the pulmonary arteries. The amount of contrast medium, body weight, and scanning delay were the independent variables that were consistently associated with enhancement of the deep veins.

The bolus-tracking technique showed relatively small variations in the scanning delay time. Patient age, body weight, and the amount of contrast medium were the important factors associated with vessel enhancement in combined CT pulmonary angiography and CT venography.