While coronary CT angiography (CCTA) has become a highly effective tool to noninvasively screen low or intermediate risk patients for coronary heart disease, its limitations have prevented CCTA from being used on high-risk patients. Now, a new CT technology called ultra-high-resolution coronary CT angiography (UHR-CCTA) has shown promise to also provide a noninvasive method to detect heart disease in high-risk patients.
The new technology, detailed in the European Journal of Radiology, overcomes the shortcomings of CCTA for high-risk patients related to high levels of coronary calcification and the frequent presence of stents in this populations. When CCTA is used, coronary calcifications tend to “bloom,” or light up in a way that makes these areas of calcification appear more extensive than they are. This can lead to overestimation of a patient’s blockages and false-positive results.
“Consequently, patients may undergo unnecessary, often invasive, testing,” said study lead author Muhammad T. Hagar, MD, from the Department of Diagnostic and Interventional Radiology at the University of Freiburg, Germany. “This is the reason why current guidelines do not recommend using CCTA in high-risk individuals.”
UHR-CCTA has emerged as a promising tool to fill this needed imaging diagnostic gap that potentially overcomes CCTA’s blooms via the use of photon-counting CT scanners. To assess the utility of UHR-CCTA for high-risk patients, Hagar and other researchers compared the accuracy of UHR-CCTA with that of the reference standard of invasive coronary angiography (IGA) in a cohort of 68 patients. All patients had severe aortic stenosis, a serious heart valve disease that reduces or block blood flow from the heart to the aorta.
UHR-CCTA proved to be both highly sensitive and specific for the detection of coronary artery disease, delivering a median image quality score of 1.5 on the five-point Likert scale, where 1 is excellent imaging and 5 is non-diagnostic. These results indicate that the technology should be made available as a noninvasive diagnostic method for patients who are at high-risk of coronary artery disease.
“It appears that the spectrum of patients benefiting from undergoing non-invasive CCTA has been significantly broadened by photon-counting detector technology,” he said. “This is excellent news for these patients and the imaging community.”
UHR-CCTA is still in the early stages of development and refinement, Hagar noted. The high resolution of UHR-CCTA is the result of a greater number of emitted photons during the imaging process, which increases radiation exposure for patients compared with regular CT scanners. Researchers are currently working to refine the technology to reduce the amount of radiation emitted.
In some instances, UHR-CCTA could be indicated for patients if the potential diagnostic benefit outweigh the risk of increased radiation exposure. However, it should not be applied to all patients. The researchers also note that the technology is not the common currently, but it should be more prevalent in the coming years.
“At the University of Freiburg, we had the privilege to work with the technology since its introduction and I am convinced that photon-counting CT is the beginning of a new generation of CT scanners, similar to the introduction to multislice CT 30 years ago,” Hagar said.
Hagar and team are also studying the potential use of UHR-CCTA for other diagnostic applications including its use for oncology imaging. They are also broadening research to study its feasibility in other areas of cardiac imagine where traditional CT imaging can’t be used, such as for patients with coronary stents. Others areas of inquiry include using the technology for heart muscle assessment, with early data suggesting UHR-CCTA may improve soft-tissue resolution, which could significantly improve disease characterization.
