Lower Radiation and Contrast Dose with New Aortic CT Protocol

A 70-kVp high-pitch non–ECG-gated thoracic aortic CTA provides acceptable imaging, with reduction in radiation and contrast agent, according to a study published in Academic Radiology.

Researchers from China sought to assess the feasibility of CTA with 40-mL contrast agent compared with 100-kVp standard-pitch CTA with 60-mL contrast agent when examining the aorta.

Sixty-seven patients (51 men and 16 women), mean age 55, participated in the study. Group A comprised 31 patients who underwent non–ECG-gated aortic CTA at 70 kVp, high pitch of 3.4, and 40-mL contrast agent. Group B, which comprised 36 patients, underwent CTA at 100-kVp, pitch of 1.2, and 60-mL contrast agent. Iterative reconstruction was used in all patients.

The researchers evaluated CTA images on a three-point scale and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared.

The results showed that the mean CT values and noise levels were higher in group A compared to group B but SNR and CNR were lower than those in group B. “The image quality of the aorta at the level of the diaphragm was lower in group A than that in group B,” the authors wrote. “However, image quality was graded as diagnostic in all patients, and motion artifacts of the aortic arch were significantly decreased in group A.”

The radiation dose, measured by mean entrance dose, was 0.4 mSv for thoracic aortic CT imaging at 70 kVp. This provided an 85% reduction compared with the 2.7 mSv with the 100-kVp acquisition mode.

Findings:

The researchers concluded that their proposed protocol provided diagnostic information while providing reduced radiation and contrast doses, compared with the standard-pitch CTA at 100 kVp.