A novel dynamic cardiac phantom for comparing blood pool and myocardial perfusion tracers: initial evaluation with CZT-ERNA and PET-MPI.

Nuclear imaging modalities can quantify cardiac volumes and left ventricular ejection fraction (LVEF), but systematic differences between techniques complicate direct comparison. Phantom-based evaluations comparing myocardial perfusion and blood-pool methods are scarce. We used a dynamic two-compartment cardiac phantom (myocardium and left ventricular [LV] lumen) with adjustable stroke volume and heart rate. Static and gated acquisitions were performed on cadmium-zinc-telluride equilibrium radionuclilde angiocardiography (CZT-ERNA) and gated positron emission tomography myocardial perfusion imaging (PET-MPI) under identical volumes and heart-rate settings. Computed tomography (CT) served as the reference for end-diastolic volume (EDV) and end-systolic volume (ESV). LVEF was derived from these volumes for all modalities. We also assessed the impact of phantom position relative to detectors, as well as the effect of attenuation correction via a thorax phantom. CZT-ERNA overestimated static LV volumes relative to CT, whereas PET-MPI underestimated them. Both modalities underestimated LVEF compared with CT-derived values, with a larger bias for PET-MPI. On PET-MPI, attenuation correction produced similar volumes with and without the thorax phantom. CZT-ERNA volumes decreased as detector distance increased. Under controlled phantom conditions, CZT-ERNA and PET-MPI show inverse biases for LV volumes and both underestimated LVEF versus CT. These findings point to the influence of reconstruction and contouring algorithms, attenuation correction, and camera positioning. The dynamic phantom enables direct comparison of perfusion- and blood-pool-based measurements and may support modality-specific calibration when translating absolute values across techniques.