Ron Blankstein, MD, MSCCT, associate director, cardiovascular imaging program, director, cardiac computed tomography, Brigham and Women's Hospital, and professor of medicine, Harvard Medical School, and former president of the Society of Cardiovascular Computed Tomography (SCCT) explains the recent advances in coronary computed tomography angiography (CCTA or CTA). He spoke to Cardiovascular Business at the 2022 SCCT meeting in July.
Among the advances are better scanner technology with improved spacial and temporal resolution, photon-counting CT and (AI) algorithms.
The biggest AI advances at SCCT were algorithms to automatically assess soft coronary plaques and coronary fat attenuation for signs of inflammation. Blankstein said AI automation is a manual, time-consuming task that no one does in the real world to contour and quantify the different types of plaque. This enables new, reproducible data that can be used to track the growth of plaques, assess the type and severity of the disease and begin prevention with medications years before the disease processes far enough to produce symptoms.
"This is an area that is really exciting right now," Blankstein said. "The AI is able to process the CT images and obtain a lot of information. First there is plaque analysis and automatic plaque quantification to be able to tell us how much plaque and the types of plaque. Today, this is something that takes a long time to do if you were ever to do it manually, but no one really uses it in real-world care. [AI] is going to be the future, where with every coronary CTA we will provide a detailed report."
Ultimately, he said this will offer a much better risk assessment than current methods and enable better preventive care to tailor specific drug therapies to reverse plaque inflammation. Two companies now have U.S. FDA clearance for this AI technology.
AI is also being incorporated into CT scanner technology to better isocenter patients to reduce the need for retakes and improve image resolution and quality even on lower-dose scans, Blankstein said.
Fractional flow reserve CT (FFR-CT) is another technology he sees as a major advance, because it enables a physiological assessment of coronary blood flow from a CT scan and eliminate the need for other tests, such as invasive angiograms.
Fat attenuation index (FAI) imaging was also identified as a major advance that has CE mark in Europe, and the vendor is seeking FDA clearance. Blankstein said the algorithm looks at the fat surrounding the coronary arteries for signs of inflammation based on the structure of the fat. This can show if a plaque in that vessel segment is inflamed and is, or may soon become, unstable and prone to plaque rupture. FAI also can show in serial followup scans if medications are reversing the inflammation.
Blankstein said FAI and AI soft plaque analysis may also enable better patient selection for some of the new, very expensive drug therapies.
Plaque assessment is also now included in the new CAD-RADS 2.0 reporting requirements for cardiac CT, where plaque is now seen as a key indicator of disease severity and risk of further cardiac events. Blankstein co-chaired the rewrite of CAD-RADS 2.0.
"In the past, we always focused on stenosis, but one of the biggest new things in CAD-RADS is we now want everyone to report how much plaque a patient has. Now you don't just report the CAD-RADS degree of stenosis, but there is now also a 'P' for plaque classification, which is associated with the level of plaque they have," Blankstein explained.
He said AI soft plaque assessment technologies need additional clinical validation in the coming years. However, they could be included in future iterations of CAD-RADS if trial evidence shows it improves diagnostic accuracy and improves patient outcomes.
Photon-counting will likely become the new standard for CT imaging in the coming years. It offers improved image quality and all scans are inherently spectral CT, so the images can be viewed at different energies. This can also be used to enhance or subtract different features, or periodic elements like calcium and iodine can be removed from images to see inside calcified plaques, or to create a non-contrast image view. Although there is only one vendor with this technology that has FDA clearance, all other major CT vendors have their own photon-counting development programs, including several that have already shown works-in-progress at recent Radiological Society of North America (RSNA) meetings.
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