“In the future, every CT will be a photon-counting CT.”
Prof. Gabriel Krestin · Erasmus Medical Center, Rotterdam, Netherlands, Past President of the European Society of Radiology
NAEOTOM Alpha with Quantum Technology is opening new avenues of clinical investigation through the acquisition of spectral data at the scanner's fastest temporal resolution.
One area of investigation is to compare extracellular volume (ECV) calculated from CT imaging against the traditional benchmark of cardiac MR (CMR) T1 mapping in the characterization of myocardial fibrosis. [20] Recent work demonstrated that quantitative and qualitative analysis of ECV maps for myocardial tissue characterization is reliable on NAEOTOM Alpha and correlates well to the MRI reference standard [20] (Figure 12).
Recent investigations have suggested that evaluation of pericardial fat as an imaging biomarker of the early stages of atherosclerosis through the use of CT imaging can enhance cardiovascular risk scoring beyond the use of calcium scoring. Thus there may be a clinical desire for the use of CT systems to allow visualization and quantification of the inflammatory response inside the vessel wall, rather than only relying on visualization of plaque inside the vessel lumen.
NAEOTOM Alpha is poised to meet the challenge of using such a biomarker, offering higher spatial resolution and image contrast for accurate segmentation of pericardial fat, with the potential to further develop an evolving new dimension in CCTA scanning.
Preliminary investigations on NAEOTOM Alpha demonstrate that a relatively new biomarker known as the “fat attenuation index” (FAI), a CCTA-based marker of coronary inflammation, demonstrates a cutoff value that is affected by the selected keV level, and this may help standardize evaluation of pericoronary inflammation by photon-counting CT as a measure of patients’ cardiac risk [21].
Figure 12: Subendocardial late enhancement in an elderly patient with recent history of percutaneous coronary intervention in the obtuse marginal artery due to non-ST-elevation myocardial infarction. Cardiac MRI images (Figs. 12a & 12c) and CT ECV maps (Figs. 12b & 12d) demonstrate basal lateral wall subendocardial involvement on short axis (top, arrows) and long-axis views (bottom, arrows). Evaluation of ECV is based on WIP software that is not commercially available (to the date of publishing this document).
Utilizing high-resolution Quantum HD Cardiac images for quantitative coronary plaque analysis also seems to provide a high degree of accuracy. A preliminary investigation showed that due to reduced blooming artifacts when using 0.2 mm slice thickness coronary CTA images compared to 0.6 mm slices, an improved visualization of fibrotic and lipid-rich plaque components is possible while the calculated calcified plaque volume is significantly reduced [22].
With the benefits provided by photon-counting CT over conventional CT, this represents a major step forward in realizing the promise of this technology for cardiovascular imaging. These key features have opened the door for a improved performance of cardiac CT angiographic examinations, enhancing clinical diagnostic capabilities and decision making, and now represent the next milestone technical advance in clinical CT imaging.
Figure 13: Analysis of plaque volumes using Quantum HD Cardiac images demonstrating improved visualization of plaque components (yellow = calcified, green = fibrotic, and blue = lipid rich) with a slice thickness of 0.2 mm (Bv64 kernel).