Performance evaluation of 4D reconstruction methods for gated cardiac single photon emission computed tomography in obese patients

The purpose of this study is to evaluate 4D reconstruction methods for the processing of gated cardiac single photon emission computed tomography (SPECT) images from obese patients. Clinical gated SPECT projection data were reconstructed using the ordered-sub sets expectation- maximization (OS-EM) and the 4D reseated block- iterative maximum a posteriori (RBI-MAP) reconstruction algorithms. The data were used to derive a relative distribution of quantitative tetrofosmin uptake ratios for the various organs. Using anthropometric data, body sizes were determined for a standard obese male and female NURBS-based cardiac torso (NCAT) phantom. Tetrofosmin uptake ratios were modeled in the obese phantoms and projection data were generated. Poisson noise was simulated, and the noisy data were reconstructed with OS-EM and 4D RBI-MAP. The projected and reconstructed data from the obese phantoms make for a realistic model of tetrofosmin uptake distribution. Qualitatively, 4D processing methods substantially improve visualization of cardiac motion in these very noisy images. We conclude that the tetrofosmin patient models provide a realistic, controllable test vehicle on which to evaluate 4D processing methods for gated cardiac SPECT. 4D processing methods improve the quality of gated SPECT images in obese patients, providing a usable representation of cardiac motion in these difficult-to-image patients.