2321. The Effect of Motion on Coronary Artery Stenosis Quantification Using Photon-Counting Detector CT With Ultra-High Resolution
Authors * Denotes Presenting Author
  1. Emese Zsarnoczay *; Medical Imaging Centre, Semmelweis University; Medical University of South Carolina
  2. Nicola Fink; Medical University of South Carolina; University Hospital, LMU Munich
  3. U. Joseph Schoepf; Medical University of South Carolina
  4. Jim O' Doherty; Siemens Healthcare USA
  5. Pál Maurovich-Horvat; Medical Imaging Centre, Semmelweis University
  6. Akos Varga-Szemes; Medical University of South Carolina
  7. Tilman Emrich; Medical University of South Carolina; University Medical Center of the Johannes Gutenberg University Mainz
The diagnostic quality of conventional coronary CT angiography (CCTA) is often influenced by motion and blooming artifacts. The aim of this study was to evaluate the feasibility of ultra-high resolution (UHR) acquisition mode for photon-counting detector CT (PCD-CT)-based CCTA and to investigate whether UHR with PCD-CT improves stenosis quantification accuracy and reduces blooming artifacts at low, intermediate, and high heart rates in a dynamic motion phantom.

Materials and Methods:
Two vessel phantoms (4 mm in diameter) containing two solid calcified lesion inserts mimicking diameter stenoses of 25% and 50% and filled with different concentrations of iodine contrast material were placed inside an anthropomorphic thorax CT phantom attached to a coronary motion simulator. The motion phantom was used to mimic the 3D motion of the coronary arteries at heart rates between 50 and 100 beats per minute (bpm). Scanning was performed on a dual-source PCD-CT system using an ECG-gated sequential mode at UHR and standard resolution, reconstructed at 60, 80, and 100 bpm in the diastolic phase with the least motion artifacts. UHR images were reconstructed using a Bv56 kernel (quantum iterative reconstruction [QIR] at a strength level of 3, slice thickness of 0.2 mm) and standard resolution images were reconstructed as virtual monoenergetic images (VMI) at 55 keV, using a Bv40 kernel (QIR 3, slice thickness of 0.6 mm). Percent diameter stenosis (PDS) and blooming artifact measurements were performed by two readers for each vessel phantom.

The measured PDS values derived by UHR were more accurate compared to standard resolution for both lesions at every heart rate, e.g. median (IQR) PDS values for the 50% lesion with standard resolution vs. UHR were 57.1% (55.2% - 59.2%) versus 50.0% (48.5% - 51.2%) at 60 bpm (p = 0.001) and 61.0% (58.6% - 64.3%) versus 52.4% (51.3% - 54.3%) at 100 bpm (p < 0.001). Blooming artifacts decreased with UHR compared to standard resolution for both lesions at every heart rate, e.g., median (IQR) blooming artifacts for the 50% nominal stenosis with standard resolution versus UHR were 67.0% (61.2% - 72.8%) versus 53.1% (50.6% - 57.0%) at 60 bpm and 71.6% (65.5% -79.2%) versus 54.9% (50.6% - 59.3%) at 100 bpm.

This phantom study demonstrated that UHR for PCD-CT-based CCTA is feasible at low, intermediate and high heart rates. Furthermore, UHR mode has the possibility to decrease blooming artifacts caused by heavily calcified plaques and to improve stenosis quantification over a wide range of heart rates.