A Preliminary Trial On The Individualized Injection Protocol For Dual Source CT Coronary Angiography

Part1: Factors influencing delay time and coronary arterial density during coronary angiography with DSCTPurpose:To investigate various factors influencing delay time and coronary arterial density during coronary CTA with dual source CT.Materials and Methods:One hundred and sixteen consecutive subjects who underwent cardiac DSCT with retrospective ECG-gating were included. Factors including gender, age, height, weight, transversal cardiac diameter (TCD), transversal thoracic diameter (TTD), heart rate (HR), body surface area (BSA=[weight/height/3600]1/2) and cardiothoracic ratio (CTR=TCD/TTD) were recorded, measured and calculated before administration of contrast media during coronary CT angiography. Delay time was determined as duration from the beginning of the injection to the density in the descending aorta at the level of right main pulmonary artery reaching a threshold of100HU. Coronary arterial density was measured at the mid portion of the right coronary artery. Regression analysis and stepwise regression analysis were used to investigate the influence of these factors on delay time and coronary arterial density.Results:Delay time decreased with an increasing HR and it was shorter in women than men. Delay time increased with an increasing TCD. Delay time could be predicted by the formula:DT=16.651-0.110×HR+1.902×gender+0.394×TCD (where DT is abbreviation for delay time, gender is0for women and1for men). Coronary arterial density decreased with an increasing HR and weight. Coronary arterial density could be predicted by the formula:CAD=923.42-4.099×HR-3.293×weight (CAD=coronary arterial density). There was no relationship between the other factors mentioned above and delay time or coronary arterial.Conclusions:Delay time is influenced by HR, gender and TCD. Coronary arterial density also changes with HR and weight. So HR, gender, TCD and weight can be used to adjust flow rate and dosage of contrast media before administration of contrast media during coronary CT angiography. Part2: Contrast material injection protocol with the flow rate adjusted to the heart rate for dual source CT coronary angiographyPurpose:To investigate the effect on coronary arterial attenuations of contrast material flow rate adjusted to a patient’s heart rate during dual source CT coronary angiography (DSCT-CCTA).Materials and Methods:A total of296consecutive patients (mean age:58.7years) undergoing DSCT-CCTA without previous coronary stent placement,bypass surgery, congenital or valvular heart disease were included. The image acquisition protocol was standardized (120kV,380mAs) and retrospective electrocardiograph (ECG) gating was used. Patients were randomly assigned to one of three groups [flow rate: G1:dosage/16, G2:dosage/(scan time×8), G3:fixed flow rate]. The groups were compared with respect to the attenuations of the ascending aorta (AA) above coronary ostia, the left main coronary artery (LM), the proximal right coronary artery (RCA), the left anterior descending artery (LAD), the left circumflex artery (LCX), and the contrast to noise ratio of the LM (LMCNR) and the proximal RCA (RCACNR). Correlations between heart rate and attenuation of the coronary arteries were evaluated in three groups with linear regression.Results:There was no significant difference in the three groups among the mean attenuations of AA (P=0.141), LM (P=0.068), RCA (P=0.284), LMCNR (P=0.598) and RCACNR (P=0.546). The attenuations of the LAD and the LCX in group1were slightly higher than those in group2and3(P<0.05). In group1, the attenuations of the AA (P<0.01), LM (P<0.01), RCA (P<0.01), LAD (P=0.02) and LCX (P<0.01) decreased, respectively, with an increasing heart rate. A similar finding was detected in group3(AA:P<0.01, LM:P<0.01,RCA:P<0.01, LAD:P<0.01and LCX:P<0.01). In contrast, the attenuations of the AA (P=0.55), LM (P=0.27), RCA (P=0.77), LAD (P=0.22) and LCX (P=0.74) had no significant correlation with heart rate in group2. In all three groups, LMCNR (P=0.77,0.69and0.73respectively) and RCACNR (P=0.75,0.39and0.61respectively) had no significant correlation with heart rate.Conclusion:Contrast material flow rate adjusted to heart rate can diminish the influence of heart rate on attenuations of the coronary arteries in DSCT-CCTA.