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Background: Fixed dose contrast medium (CM) injection protocols are often used in CT coronary arteriography (CTCA). However, vascular enhancement is related to body weight and injection dose rate. Purpose: To compare aortic enhancement and coronary imaging quality between a fixed dose CM injection protocol and one adapted to body weight with a constant injection dose rate in mg I/kg/s. Material and Methods: One hundred consecutive patients undergoing CTCA were randomized to two groups; group I received 65 mL CM (370 mg I/mL) at 5 mL/s and group II received 0.9 mL CM (370 mg I/mL) per kg during 12 s resulting in a constant injection dose rate of 28 mg I/kg/s.The groups were re-divided according to body weight: IA ≤ 70 kg, IB >70 kg, IIA ≤ 70 kg, IIB >70 kg. Aortic attenuation was measured and coronary imaging quality was graded using a four-grade scale. Results: The resulting mean CM dose, aortic attenuation and score of coronary imaging quality in groups IA/IB/IIA/IIB were 24/24/19/27 g I, 437/403/448/440 HU and 2.8/2.3/2.7/2.6, respectively. CM dose and aortic attenuation were significantly different between groups IA and IIA (p < 0.001, p = 0.01), as well as between groups IB and IIB (p < 0.001, p < 0.001).There was no statistically significant difference regarding coronary imaging quality between groups IA and IIA (p = 0.30), while there was a significant difference between groups IB and IIB (p < 0.001). Conclusion: In CTCA, body weight-adapted CM injection protocols using a constant dose rate can help save CM doses in slimmer patients and improve aortic enhancement and coronary imaging quality in heavier patients compared to fixed dose protocols. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: To explore the feasibility of multiphase contrast–saline mixture with dual-flow injection technique for visualization of right ventricular (RV) cavity and interventricular septum (IVS) in 64-row multidetector computed tomography (MDCT) coronary angiography. Materials and methods: Twenty-four patients underwent coronary CT angiography (CTA) imaging with 64-row MDCT. In twelve patients (group A), 60ml contrast medium (CM) bolus was followed by 40ml saline, and in the other twelve patients (group B), 50ml CM bolus was followed by 50ml contrast–saline mixture at 60:40 ratio. The CM, saline and contrast–saline mixture flow rate were all 5.0ml/s. Two experienced radiologists measured the CT values of ascending aorta, descending aorta, pulmonary artery and RV, rated the uniformity of RV cavity, the visualization of coronary arteries and IVS independently. Results: By Kappa test, agreement between the two radiologists was 0.93 and 0.86 concerning the CT value measurements and the grades of the three indexes, respectively. By t-test, the mean CT values of ascending aorta and descending aorta of the two groups had no statistical difference (t =1.459, P >0.05; t =1.619, P >0.05); while the mean CT values of pulmonary artery and RV cavity had statistical differences (t =8.316, P <0.05; t =10.372, P <0.05). By two-related rank sum test, according to the visualization of coronary arteries and the uniformity of RV cavity, there were no statistical differences (U =66.00, P >0.05; U =54.00, P >0.05); while according to the visualization of IVS, group B was better than group A (U =8.00, P <0.05). Conclusion: In coronary CTA, a contrast–saline mixture after CM bolus can provide clear visualization of RV and IVS and LV without impairing coronary CTA image. [Copyright &y& Elsevier]