Trial Outcomes & Findings for Clinical Impact of Cardiac Photon-Counting Detector CT (NCT NCT05240807)

Patients scheduled for a clinically indicated coronary CT angiogram, stress cardiac MRI, or nuclear cardiovascular stress scan in Mayo Clinic Rochester outpatient practice were invited to participate in this study from August 2022 to February 2026. After their clinical exam, patients were approached by a study coordinator to discuss the research study. If they provided written informed consent, the patient was escorted to their photon-counting detector CT scan.

After their clinical scan and before their research scan (intervention), 25 patients withdrew consent, 4 patients failed to meet the inclusion criteria, and 1 patient had an issue with IV placement that prevented scanning resulting in a final cohort of 246 patients.

Clinical Impact of Cardiac Photon-Counting Detector CT

Percent area stenosis (PAS) measures coronary artery stenosis (blockage) and is defined as the vessel's cross-sectional area in the region of highest stenosis (i.e., most closed) divided by the healthy vessel's cross-sectional area. PAS can range from 0% to 100% with higher percentages indicating worse stenosis. In arm 1, PAS was measured at the site of worst stenosis in each coronary vessel or patient using validated commercial software. For each stenosis, PAS was measured at the same location in the photon-counting detector CT (PCD-CT) angiography scan and in the clinical CT angiography scan (EID-CT). These values were subtracted to get a change in PAS between the clinical EID-CT scan and the PCD-CT scan for each stenosis. Change in PAS impacts patient management. During recruitment, the PCD-CT scanner had a multi-energy ultra-high resolution update allowing a new scan mode that collected x-ray energy data. This mode was used for all patients recruited after the update.

Sensitivity was calculated as the number of patients correctly identified by the reader as having perfusion defects on photon-counting detector (PCD) CT divided by the total number of patients with perfusion defects. Specificity was calculated as the number of patients correctly identified by the reader as not having perfusion defects on PCD-CT divided by the total number of patients without perfusion defects. Sensitivity and specificity can range between 0 and 100%. All analyzed images were taken when the patient was at rest.

Coronary Artery Disease-Reporting and Data System (CADRADS) score is a value assigned to each patient based on the patient's highest percent diameter stenosis (PDS) with higher scores indicating worse stenosis. PDS is defined as the diameter of the stenosed (blocked) coronary vessel divided by the diameter of the healthy vessel. A CADRADs score of 0-5 is assigned to the following PDS values, respectively: 0%, 1-24%, 25-49%, 50-70%, 70-99%, and 100%. A CADRAD score was calculated for each patient in both EID-CT and PCD-CT scans based on the respective PDS for the same lesion. The number of patients whose CADRADS decreased in PCD-CT relative to EID-CT (e.g. 2 on PCD-CT, 3 on EID-CT) is reported below. Change in CADRADS impacts patient management. During recruitment, the PCD-CT scanner had a multi-energy ultra-high resolution update allowing a new scan mode that collected x-ray energy data. This mode was used for all patients recruited after the update.

Sensitivity was calculated as the number of patients correctly identified by the reader as having perfusion defects on photon-counting detector CT (PCD-CT) divided by the total number of patients with perfusion defects. Specificity was calculated as the number of patients correctly identified by the reader as not having perfusion defects on PCD-CT divided by the total number of patients without perfusion defects. Sensitivity and specificity can range between 0 and 100%. All analyzed images were taken after the patient was administered a pharmacological cardiac stress agent to increase heart rate.