Can Photon-Counting CT Bolster Myocardial Extracellular Volume Quantification Beyond EID-CT?

Emerging research suggests that photon-counting computed tomography (PCCT) significantly enhances myocardial extracellular volume (ECV) quantification over dual-phase energy-integrating detector CT (EID-CT) and may provide a viable alternative in the absence of cardiac magnetic resonance (CMR) imaging. For the retrospective study, recently published in European Radiology, researchers compared single- and dual-phase myocardial ECV measurements with PCCT to dual-phase EID-CT in relation to cardiac MRI. All 80 patients in the cohort had 3T CMR while PCD-CT and EID-CT use was evenly divided in the cohort, according to the study. The study authors found that single-phase and double-phase myocardial ECV measurements obtained with PCCT provided an 84 percent and 91 percent correlation coefficient, respectively, to CMR whereas EID-CT myocardial ECV measurement offered a 62 percent correlation coefficient. The capability of photon-counting detector CT (PCD-CT) to facilitate spectral imaging without compromising temporal resolution is a significant advantage over EID-CT for cardiac assessments, according to the researchers. “The lower temporal resolution of EID-CT in dual energy mode (125 ms for dual-source EID-CT vs 66 ms for PCD-CT) can be relevant in patients with higher or irregular heart rates, as it may lead to motion artifacts and reduced image quality, thereby affecting the accuracy of ECV,” pointed out lead study author Shouyu Bao, M.D., who is affiliated with the Department of Radiology at the Ruijin Hospital and the Shanghai Jiao Tong University School of Medicine in Shanghai, China, and colleagues. For patients with higher heart rates (HR > 60 bpm), the researchers found that single-phase and dual-phase ECV measurements obtained with PCD-CT offered an 87 percent and 88 percent interclass correlation coefficient (ICC), respectively to CMR in contrast to a 60 percent ICC for EID-CT. Three Key Takeaways Improved accuracy. Photon-counting CT (PCCT) demonstrated substantially stronger correlation with CMR for myocardial ECV quantification compared to energy-integrating detector CT (EID-CT). Better performance in patients with higher heart rates. PCCT maintained higher reliability than EID-CT in patients with elevated or irregular heart rates, reducing motion artifacts and improving image quality. Lower radiation dose. PCCT provided more accurate myocardial tissue characterization at less than half the radiation dose of EID-CT, enhancing its clinical utility. “In (comparison) to EID-CT, PCD-CT provided more accurate and reliable myocardial ECV quantification, particularly in patients with higher heart rates, where motion sensitivity is a concern,” added Bao and colleagues. Noting key differences between PCD-CT and EID-CT with respect to radiation dosing, the study authors also pointed out that the median dose length product (DLP) for PCT-CT was less than half of the median DLP for the EID-CT cohort (247.50 mGy-cm vs. 497.55 mGy-cm). (Editor’s note: For related content, see “Photon-Counting CT Study Examines Impact of Scan Mode on Radiation Dosing for CCTA in Patients with Non-Acute Chest Pain,” “Study: Photon-Counting CT Reduces Radiation Dosing by More than 40 Percent in Kids with Congenital Heart Disease” and “Study Shows Enhanced Diagnosis of Coronary Artery Stenosis with Photon-Counting CTA.”) In regard to study limitations, the authors acknowledged the potential for selection bias and unmeasured cofounding factors with PCD-CT and EID-CT scans being obtained on different platforms. They also conceded possible discrepancies with CMR acquisition during diastole and CT-ECV acquisition during systole.