To determine the value of individual injection protocols to result in more homogeneous vascular attenuation in coronary CT angiography (CCTA).

Two hundred and forty patients with suspicious coronary heart disease and underwent CCTA were prospectively randomized into experimental group (n=120) and control group (n=120). Four subgroups with each thirty subjects were divided randomly to use different contrast concentration (300, 320, 350 and 370 mg/ml). In the experimental group, injection protocols were determined by the formula: contrast dosage (ml) =[(weight × 280 mg/kg)/contrast concentration], injection rate (ml/s) = (contrast dosage/12 s). Other parameters between two groups were same. In the control group, patients received a fixed dose of 80 ml of contrast medium at 5.5 ml/s. For each patient, CT values of aorta, left main artery, left anterior descending branch, left circumflex branch and right coronary artery were measured, meanwhile contrast dosage and injection rate were recorded. One-way analysis of variance was used to compare CT attenuation among subgroups, inter-group comparison was performed with LSD method. Contrast dosage and injection rate between two groups were compared with t test.

Under the experimental group, CT attenuations were between 348 to 396 HU, which showed no significant difference among target arteries (all P> 0.05). Under the control group, CT attenuations were between 256 to 396 HU, which showed significantly different among target arteries (all P<0.05), and the attenuation with contrast concentration of 300 mg/ml was significantly lower than that with 370 mg/ml or 350 mg/ml. The average contrast dosage in experimental subgroup 1 to 4 were (67±9),(64±8),(62±7),(61±7) ml, lower than those in control subgroups (t value were 10.04,12.49,14.55 and 15.24, all P<0.01). The average injection rate in experimental subgroup 1 to 4 was (5.5±0.6),(5.2±0.7),(5.1±0.6),(5.0±0.6) ml/s. Injection rate in subgroup 1 showed no significant difference (t=0.06, P>0.05), injection rates in subgroup 2 to 4 were lower than those in the control subgroups (t value were 2.22,3.56 and 4.39, all P<0.05) .

Individual injection protocols in CCTA can be used to achieve homogeneous coronary attenuation levels with overall contrast dosage and injection rate reduction.

Coronary arteries; Tomography, X-ray computed; Contrast media