Author: mh/ktg

Related content: CT, Vessels, Contrast Agents, Workflow

Reducing Iodine Delivery Rate in CTA

Low injection speed of high concentration contrast media provides diagnostic images in coronary CTA at 70 kVp.

Session Topic: Cardiac CT: contrast agent and radiation dose
Session Date: Wednesday, March 1st 2017
Presentation Code: B-0145
Presentation Title: Low Contrast Medium Injection Speed Study on Prospectively High-pitch Coronary CT Angiography at 70 kVp
Name of Speaker: Liang Zhang, First Hospital of China Medical Center, Shenyang/China
Congress: ECR 2017, Vienna

Coronary CT Angiography (CTA) at 70 kVp significantly reduces radiation dose and increases contrast compared to higher kVp settings. Liang Zhang from Shenyang, China, and colleagues looked for the optimal contrast flow rate for 70 kVp protocols. Therefore, they evaluated feasibility and image quality of prospectively ECG-triggered high-pitch coronary CTA with a contrast medium injection rate of 3.5 mL/s at 70 kVp.

Methods

104 patients with suspected coronary artery disease included in this prospective study. All patients had a body mass index (BMI) below 26 kg/m2 and were randomly distributed to two groups of 52 patients each:

  • Patients in the experimental group A received a contrast volume of 28 mL of 370 mg Iodine/mL at a flow rate of 3.5 mL/s.
  • Patients in the control group B received 40 mL of 370 mg I/mL at a flow rate of 5 mL/s.

Injection duration was 8 s in both groups. The resulting iodine delivery rate (IDR) were 1.295 gI/s for group A and 1.85 gI/s for group B.

All patients underwent ECG-triggered high-pitch coronary CTA on a Dual-Source CT system at 70 kVp. Pitch was 3.2 for all patients. Iterative reconstruction was used at a strength level of 3.

Zhang and colleagues assessed the attenuation in different segments of the coronary arteries, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). They subjectively evaluated image quality using 4-point grading scale.

Results

CTA was performed successfully in all patients. The mean attenuation was significantly lower in group A compared to group B; however, it reached levels above 400 HU in all segments. The noise was significantly lower in group A.

The SNR was significantly lower in all coronary artery segments of group A, except for the left main artery.

The CNR was significantly lower in the ascending aorta, the left anterior descending artery, and the left circumflex artery of group A compared to group B. The differences were not significant for the right coronary artery and the left main artery.

All CT scans were diagnostic in both groups.

The subjective evaluation of image quality showed no statistical differences: 3.04±0.75 in group A vs. 3.0±0.79 in group B.
The radiation dose did not vary significantly between the two groups: 0.36±0.06 mSv in group A vs. 0.38±0.07 mSv in group B.

Conclusion

“The proposed protocol is a suitable option to exclude cardiovascular diseases if radiation dose or contrast media toxicity is a concern,” concluded Zhang. “An injection rate of 3.5 mL per second could allow more patients with poor vascular condition to undergo coronary CT angiography.”