Preliminary study of individualized contrast injection protocols in triple-rule-out computed tomography angiography using a high-pitch dual-source technique

Abstract

To assess the feasibility of individual contrast injection protocols in triple-rule-out computed tomography examination using a dual-source Flash-chest-pain technique. From April to August 2014, 63 patients with undifferentiated acute chest pain underwent ECG-synchronized dual-spiral chest CT angiography. 31 Patients, who all had low (<65 bpm) and stable heart rate underwent TRO CT angiography in a Flash mode, with an individual triphasic contrast protocol based on weight (350 mgI/ml, A: 0.7 ml/kg, setting 10 s duration time; B: 8 s mixture of the contrast agent and saline at the same rate; C: 6-7 s saline at the same rate). In contrast, the other patients, who had random heart rate, underwent TRO CT angiography in a traditional retrospectively mode with an identical biphasic contrast protocol (350 mgI/ml, A: contrast agent 90 ml, B: saline 40 ml, injection rate 5 ml/s). Quantitative image analysis assessed vessel attenuation of aorta, coronary and pulmonary artery, signal-to-noise ratio (SNR) and contrast-to noise ratio (CNR). Subjective image was assessed on a 5 point scale (1: excellent, 5:non-diagnosis) by two blind observers. The effective dose was calculated from the dose length product (DLP) using a conversion coefficient of 0.017 mSv·mGy(-1)·cm(-1). There was no significant difference of aorta and coronary artery attenuation, noise, SNR, CNR or subjective image quality between both patient groups. Pulmonary artery attenuation was lower in test group than in control group, but it also can meet the diagnostic criteria. Moreover, the mean contrast agent and the effective dose were lower in test group than in control group (72±10) vs (90±0) ml, P<0.01 and (3.0±0.3) vs (18.8±2.7) mSv, P<0.01. As to patients with low and stable heart rate, this individual contrast protocol along with dual-source high-pith technique, is capable of achieving satisfactory image which could meet the diagnostic requirements with lower contrast agent and lower effective dose.