Photon-counting CT reduces contrast by 25 percent without impacting image quality: Study

The results, published in Radiology: Cardiothoracic Imaging, further highlight the benefits of photon-counting computed tomography.

The researchers showed that CTA of the aorta was linked with a higher contrast-to-noise ratio (CNR), resulting in a low-volume contrast media protocol offering noninferior image quality versus energy-integrating detector (EID) CT at the same radiation dose.

CCTA is used with contrast to examine the aorta that passes through the abdomen and the chest and is prone to aneurysms. Using iodinated contrast agents in the exam is considered safe, but there are risks, particularly among kidney disease patients.

Many patients undergoing CCTA of the aorta are older, and some may suffer from a certain nephropathy degree; thus, they might be at risk for further kidney function reduction due to the contrast media administration. Also, iodine breakdown can have adverse effects on the planet and contrast agents are subject to supply chain disruptions, reducing the amount and use of CT contrast becomes more significant.

Against the above background, Kai Higashigaito and the research team from Switzerland aimed to evaluate and develop a low-volume contrast media protocol for thoracoabdominal CT angiography (CTA) with photon-counting detector (PCD) CT in a prospective study.

The study included consecutive participants who underwent CTA with a photon-counting detector of the thoracoabdominal aorta and previous CTA with EID CT at equal radiation doses. In PCD CT, virtual monoenergetic images were reconstructed in 5-keV intervals from 40 to 60 keV.

Noninferiority analysis was used to determine the noninferior image quality of the low-volume contrast media protocol with PCD CT. The measurement of image noise, attenuation of the aorta, and the contrast-to-noise ratio were done, and two independent readers rated subjective image quality. The first group used the same contrast media protocol for both scans. CNR gain in PCD CT compared with EID CT served as the second group's reference for contrast media volume reduction.

The authors reported the following findings:

· The study included 100 participants (mean age, 75 years ± 8 [SD]; 83 men). In the first group (n = 40), VMI at 50 keV provided the best trade-off between objective and subjective image quality, achieving 25% higher CNR than EID CT.

· Contrast media volume in the second group (n = 60) was reduced by 25% (52.5 mL).

· Mean differences in CNR and subjective image quality between EID CT and PCD CT at 50 keV were above the predefined boundaries of noninferiority (−0.54 and −0.36, respectively).

"The findings showed that the improved image quality of CCTA with photon-counting detector CT systems can be used to reduce the amount of administered contrast media to the patients without reducing the examination's diagnostic yield," the researchers wrote. "Image quality remained at the same level as previous CT angiography examinations in the same patients using a conventional CT, even though we reduced the contrast media volume."

"CCTA of the aorta with [PCCT] was linked with higher contrast-to-noise ratio, which translated into a low-volume contrast media protocol demonstrating noninferior image quality compared with [conventional] CT at the same radiation dose," they conclude.

Reference:

The study titled "CT Angiography of the Aorta Using Photon-counting Detector CT with Reduced Contrast Media Volume" was published in Radiology: Cardiothoracic Imaging.

DOI: https://doi.org/10.1148/ryct.220140