Quantification of regional left ventricular function from electrocardiogram-gated cardiac nuclear medicine tomographic images

Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) have the unique potential to provide a three-dimensional (3D) map of perfusion/metabolic activity throughout the left ventricle (LV) of the heart. Through electrocardiogram gating of the acquisition, these modalities have the potential to also allow the assessment of global and regional mechanical function. However, a number of physical factors, including image noise and poor spatial resolution, limit the clinical utility of these modalities. In this work, we investigate various data analysis techniques in order to (1) recover the true cardiac radioisotope distribution from noisy, blurry images, and (2) establish a scheme to assess regional LV function quantitatively.; First, we discuss a resolution-correcting, model-based fitting method for measuring regional wall thickening (TK) from gated 18F PET/201Tl SPECT perfusion/metabolism studies. To reduce the method's high sensitivity to noise, we introduce a refinement of the model by applying a temporal constraint on the tracer uptake within the LV, and fitting profile data from all time-points simultaneously. Experiments using mathematical and physical phantom data indicated a reduced variability in TK.; We then extended the model to two spatial dimensions, while introducing Fourier constraints on the LV's shape and motion. We applied the method to simulated 99mTc SPECT gated blood pool (GBP) images, in which the tracer binds to the blood rather than the LV muscle. Results suggest that lower-frequency terms describing the LV shape and motion can be recovered despite high noise-levels and poor resolution. Next, we investigated the feasibility of short-duration cardiac stress GBP studies. Rest scans of 10 normals and two patients (obtained from the Nuclear Medicine Department, Clinical Center, National Institutes of Health) were analyzed quantitatively, and the clinical impact of increased noise was estimated. We found that stress studies may provide reliable regional LV function measurements, despite the increased noise.; Finally, we developed 3D and 4D spherical harmonic Models for 201Tl SPECT perfusion data. Results were assessed qualitatively using actual patient data and quantitatively using simulations. Our methods compared unfavorably with 1D and 2D models when applied to ideal data, but outperformed them at a realistic noise-level and resolution.