Myocardial Perfusion Quantification With SPECT Using Multi-Pinhole Collimator Compared to Photon-Counting Coronary CTA

This prospective study aims to compare functional abnormalities detected using myocardial perfusion SPECT imaging (MPI SPECT) with the extent and severity of anatomical findings on coronary computed tomography angiography (coronary CTA). Additionally, the investigators aim to enhance the diagnostic value of MPI SPECT by quantifying myocardial blood flow and utilizing myocardial flow reserve calculated from dynamic SPECT images.

50 patients with suspected coronary artery disease are anticipated to be enrolled. Pharmacological stress and rest-phase dynamic and static MPI SPECT following an additional coronary CTA scan are to be performed. The obtained multimodality imaging data (functional and anatomical parameters) are planned to be compared and subjected to statistical analysis. The results of this study are expected to improve risk assessment for patients with moderate cardiovascular risk and enhance the diagnostic performance of MPI SPECT.

Diagnostic management of patients with moderate clinical likelihood of obstructive coronary artery disease (CAD) remains challenging. Myocardial perfusion SPECT imaging (MPI SPECT) is a widely available and cost-effective modality that provides functional information on segmental perfusion defects. However, conventional static MPI SPECT has moderate diagnostic performance in identifying subclinical coronary atherosclerosis.

The novel multi-pinhole (MPH) collimator technology with a three-detector SPECT camera (AnyScan® TRIO SPECT/CT, Mediso Ltd., Hungary) enables temporal and spatial resolution, absolute quantification of stress and rest myocardial blood flow (sMBF and rMBF), and calculated myocardial flow reserve (MFR), overcoming the difficulties of semi-quantitative evaluation.

This study aims to investigate the association between quantitative MFR, semi-quantitative functional parameters of dynamic, static MPI SPECT, and coronary CTA-based plaque metrics. Flow parameters of myocardial wall segments will be corresponded to the appropriate coronary artery based on the CT-assessed anatomy. Furthermore, the investigators aim to build statistical models representative of clinical scenarios to test the diagnostic accuracy of the MPH collimator.

In this prospective study, 50 patients with moderate cardiovascular pre-test probability (PTP) referred to either coronary CTA or MPI SPECT are anticipated to be enrolled. Cardiovascular PTP is estimated according to the CAD consortium based on age, sex, type of chest pain, and cardiovascular risk factors. Patients with a history of coronary artery bypass graft implantation, left or right bundle branch block, and atrial fibrillation will be excluded. Participants will be subjected (1) to dynamic and (2) static MPI SPECT (pharmacological stress and rest) and (3) to coronary CTA within 30 days. Patients undergoing pharmacological stress (dipyridamole or adenosine) dynamic MPI SPECT, which will be performed with AnyScan® TRIO SPECT/CT (Mediso Ltd.). Imaging will be started at the time of the radiopharmaceutical administration both in stress and rest, captured for 15 minutes in list mode. BMI-standardized doses of 99m-Tc will be used, with a same-day acquisition protocol, resulting in a three-fold increase for the rest phase compared to stress. Following each phase of dynamic acquisition in 30-60 minutes, an ECG-gated static MPI SPECT will be performed using a conventional LEHR collimator.

Data, such as sMBF, rMBF, MFR, summed stress score (SSS), summed rest score (SRS), summed difference score (SDS), as well as visually evaluated perfusion defect severity and extent will be determined from MPI SPECT. Within 30 days of MPI SPECT, coronary CTA with Calcium Score assessment will also be performed using a photon-counting detector CT (NAEOTON Alpha, Siemens Healthineers, Germany). Coronary CTA will be analyzed as follows: coronary artery calcium score (CACS), the severity of luminal stenosis, total plaque volume, quantitative plaque composition, and CT-derived fractional flow reserve (FFR). The following additional anamnestic covariants will be used: age, sex, and cardiovascular risk factors such as type of chest pain, diabetes mellitus, hypertension, smoking, obesity, and dyslipidemia.

The investigators hypothesized that dynamic MPI SPECT may prove to be superior to semi-quantitative static MPI SPECT in detecting CAD. Furthermore, MFR data combined with CACS may improve the diagnostic accuracy of MPI SPECT and guide the selection of patients for invasive coronary angiography.

MPI SPECT and coronary CTA data will be analyzed on-site at Semmelweis University, Hungary. The results will be available after the completion of patient enrollment.

Eligibility Criteria:
Inclusion Criteria:

* suspected coronary artery disease
* referred to coronary CTA or SPECT MPI by the patient's physician
* agrees to the other imaging modality that was not indicated by their physician (coronary CTA or SPECT MPI)
* suitable for informed consent

Exclusion Criteria:

* moderate or severe aortic valve stenosis
* atrial fibrillation
* pregnancy or breastfeeding
* history of coronary artery bypass graft implantation
* history of stent implantation
* chronic renal failure (eGFR \< 30 ml/m2)
* active oncological treatment
* congenital heart disease
* left or right bundle branch block