| ObjectiveTo ensure both the aorta and pulmonary artery well-enhanced, a long contrast injecting time is needed in triple-rule-out(TRO) computed topography (CT) examinations. Therefore, a large amount of contrast medium was used in most of the previous studies. The aim of this study is to assess the feasibility of individual contrast injection protocols in triple-rule-out computed tomography examination using a dual-source Flash-chest-pain technique.Materials and MethodsFrom 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 (<65bpm) and stable heart rate underwent TRO CT angiography in a Flash mode, with an individual triphasic contrast protocol based on weight (350mgI/ml, A: 0.7ml/kg, setting 10s duration time; B:8s mixture of the contrast agent and saline at the same rate; C:6-7s 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(350mgl/ml, A:contrast agent 90ml, B:saline 40ml, injection rate 5ml/s). Quantitative image analysis assessed vessel attenuation of aorta 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 CT dose index volume (CTDIvol) and dose length product (DLP) were recorded and the effective dose (ED) was calculated by using a conversion coefficient of 0.017mSvmGy-1cm-1.ResultsVessel attenuation of different segments was ascending aorta 373.1 ±51.6Hu vs 394.3±42.4Hu、aortic arch 378.4±48.8Hu vs 398.5±43.1Hu, middle thoracic descending aorta 322.1±.5Hu vs 342.9±46.0Hu, distal thoracic descending aorta 311.9±54.4Hu vs 336.6±.6Hu, main pulmonary artery 338.6±63.8Hu vs 402.7± 55.5Hu, left pulmonary artery 323.2±63.6Hu vs 398.5±47.9Hu, right pulmonary artery 312.9±60.9Hu vs 400.2±53.8Hu, left coronary artery 373.8±50.6Hu vs 394.6±43.0Hu, right coronary artery 381.3±65.2Hu vs 398.9±53.9Hu, respectively. SNR and CNR were 26.3±5.8 vs 26.9±4.9,22.5±5.4 vs 23.3±4.6. The average subjective image point was 1.5±1.0 vs 1.4±0.7. The effective dose was 2.97± 0.3mSv vs 18.80±2.63mSv.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 (72.1±9.9ml vs 90±0ml, P< 0.001; 2.97±0.3mSv vs 18.80±2.67mSv, P<0.001)ConclusionTo 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 than the traditional retrospectively technique. |
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