Rationale and Objectives
To investigate the feasibility of low-volume injections of contrast material with a body weight-adapted iodine-dose protocol in computed tomography coronary angiography (CTCA) using a 320-detector row scanner.
Materials and Methods
Ninety-eight patients who underwent CTCA in a single heartbeat with electrocardiogram-gating were divided into two groups, receiving 0.8 mL/kg of contrast material injected at a fixed duration of 12 seconds (A; n = 48) or 0.7 mL/kg of contrast material injected at a fixed duration of 10 seconds (B; n = 50); all patients then received 20 mL of saline. Contrast densities were assessed for the ascending aorta, left ventricle, right coronary artery (RCA), and left main coronary artery (LMA).
Results
The mean flow rate was 4.00 ± 0.56 mL/second in group A and 4.06 ± 0.57 mL/second in group B ( P = .51). There were no significant differences in the mean enhancement values of the ascending aorta, LMA and proximal RCA between the two groups. Also, there was no significant difference between the mean enhancement values at the three different levels of the RCA (proximal, middle, and distal segments) (group A; P = .27, group B; P = .07).
Conclusion
The use of 0.7 mL/kg of contrast material injected at a fixed duration of 10 seconds was feasible for CTCA using 320-detector row CT, with a sufficient and reliable contrast enhancement in the ascending aorta and coronary artery.
Computed tomography coronary angiography (CTCA) has become a standard in the noninvasive assessment of coronary arteries in the past few years . In CTCA, high and consistent vascular enhancement is a prerequisite for sufficient evaluation . Recently, it has been reported that a patient weight–adapted iodine-dose protocol with fixed injection duration yielded significantly better image quality than the fixed-dose protocol in 64-detector row CTCA . An injection volume of 1.0 mL/kg body weight of contrast material (370 mgI/mL) is necessary to achieve a sufficient contrast enhancement, and injection duration of 15 seconds is recommended in 64-detector row CTCA .
Very recently, 320-detector row CT scanner has been developed with a z-coverage value of 160 mm; thus, the entire heart can be scanned in a single rotation and within a single heartbeat with a minimum temporal resolution of 175 ms . The data acquisition time for 320-detector row CTCA is less than 3 seconds, which is quite short compared with 64-detector row CTCA at less than 10 seconds. Because this shorter scan time permits a decrease in the contrast dose or the injection duration at CTCA , contrast material protocols must be adjusted and optimized as CT technology evolves.
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Materials and methods
Patients
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CT Scanning
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Methods of Evaluation
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Statistical Analyses
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Results
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Table 1
Patient Characteristics and contrast Dose at Each Group
Group A Group B_P_ Age (y) 69.8 ± 9.8 68.7 ± 9.0 .39 Weight (kg) 59.3 ± 8.4 58.0 ± 8.1 .34 Heart rate (beats/min) 57.1 ± 9.7 58.8 ± 6.4 .14 Flow rate (mL/sec) 4.00 ± 0.56 4.06 ± 0.57 .51Iodine rate (gI/sec) 1.40 ± 0.20 1.42 ± 0.20 .50
Data are the mean ± SD.
Table 2
The Mean Enhancement Values in Each Portion
Group A Group B_P_ Ascending aorta 452.9 ± 50.4 450.7 ± 49.1 .83 Pulmonary artery trunk 188.7 ± 63.7 130.8 ± 31.6 <.01 Right ventricle 146.0 ± 45.4 106.2 ± 27.3 <.01 Left ventricle 414.9 ± 46.4 402.9 ± 49.5 .21 Left main coronary artery 410.6 ± 47.9 416.8 ± 52.6 .52 Proximal right coronary artery 374.6 ± 43.7 384.2 ± 49.8 .38 Middle right coronary artery 361.6 ± 47.0 364.4 ± 48.8 .98 Distal right coronary artery 357.8 ± 51.6 361.2 ± 46.1 .79
Data are the mean ± SD.
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Discussion
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