Coronary computed tomographic angiography at low concentration of contrast media and low tube voltage in obese patients

Abstract

Objective To explore the feasibility of coronary computed tomographic angiography (CCTA) for obese patients with lower tube voltage (100 kV) and lower contrast media concentration (270 mgI/ml) using iterative reconstruction. Methods A total of 48 patients with body mass index greater than 30 kg/m2 were included and randomly divided into 2 groups according to random number table method. The images of the control group were obtained using iodine 370 mgI/ml, a tube voltage of 120 kV, and traditional filtered back projection (FBP) image reconstruction. Patients in the test group were injected with isotonic low concentration contrast media (270 mgI/ml), scanned with a lower tube voltage (100 kV), and adaptive iterative noise reduction image reconstruction algorithm (AIDR-3D) was used. Two experienced physicians scored the image quality in a double-blind way. Independent sample t-test was used to compare the effective dose (E), average CT values, signal to noise ratio (SNR), contrast to noise ratio (CNR), the figure of merit (FOM), image quality scores and the total iodine intake. Side effect was also evaluated. Results The subjective scores for control group and test group were not significantly different (P>0.05). The scores of two physicians were consistency (Kappa=0.88, P 0.05), but the FOM of the test group was significantly higher than that of the control group (t=-9.250,-8.604,-9.158,-5.341, P<0.05). Effective dose in the test group was (1.61±0.41) mSv, lower than that of the control group (t=8.373, P<0.01). The total iodine and iodine injection rate in the test group were both lower than in the control group (t=7.628, 8.480, P<0.01). The incidence of contrast media-related discomfort in the test group was lower than control group (χ2=18.70, 6.25, P<0.05). Conclusions For obese patients, isotonic low concentration of contrast media and low-dose CCTA could be feasible, which substantially reduce the radiation dose and iodine intake without sacrificing image quality. Key words: Obesity; Coronary vessels; Tomography, X-ray computer; Radiation dose; Contrast media