Sarah G Cuddy-Walsh1,2, R Glenn Wells3,4. 1. Department of Physics, Carleton University, Ottawa, ON, Canada. swalsh@ottawaheart.ca. 2. Division of Cardiology, University of Ottawa Heart Institute, H2243 - 40 Ruskin Street, Ottawa, ON, K1Y 4W7, Canada. swalsh@ottawaheart.ca. 3. Department of Physics, Carleton University, Ottawa, ON, Canada. 4. Division of Cardiology, University of Ottawa Heart Institute, H2243 - 40 Ruskin Street, Ottawa, ON, K1Y 4W7, Canada.
Abstract
BACKGROUND: Dedicated cardiac SPECT cameras which employ multi-pinhole detectors have variable photon sensitivity within the camera's field-of-view such that a lower number of photon counts is typically detected from the base of the heart than from the apex. Consequently, the noise in a reconstructed image is expected to be higher at the base than at the apex of the heart. METHODS: Patient emission images were resampled to create statistical replicates which were reconstructed with and without attenuation correction. Noise images were computed using one standard deviation of the replicated images. These were evaluated for 93 patients with normal study results, each imaged with both a dual-headed parallel-hole camera and a multi-pinhole camera. Statistics for a normal database (NDB) of images from the 93 patients were also calculated. RESULTS: Image noise (1.7-fold) and NDB uncertainty (1.3-fold) increase significantly from the apex-to-the base of the heart in attenuation-corrected multi-pinhole SPECT images. The differences for non-attenuation-corrected images or those acquired with a parallel-hole camera were not significant. CONCLUSIONS: For best interpretation of attenuation-corrected images acquired with multi-pinhole cameras, knowledge of NDB uncertainty gradients should be taken into consideration.
BACKGROUND: Dedicated cardiac SPECT cameras which employ multi-pinhole detectors have variable photon sensitivity within the camera's field-of-view such that a lower number of photon counts is typically detected from the base of the heart than from the apex. Consequently, the noise in a reconstructed image is expected to be higher at the base than at the apex of the heart. METHODS: Patient emission images were resampled to create statistical replicates which were reconstructed with and without attenuation correction. Noise images were computed using one standard deviation of the replicated images. These were evaluated for 93 patients with normal study results, each imaged with both a dual-headed parallel-hole camera and a multi-pinhole camera. Statistics for a normal database (NDB) of images from the 93 patients were also calculated. RESULTS: Image noise (1.7-fold) and NDB uncertainty (1.3-fold) increase significantly from the apex-to-the base of the heart in attenuation-corrected multi-pinhole SPECT images. The differences for non-attenuation-corrected images or those acquired with a parallel-hole camera were not significant. CONCLUSIONS: For best interpretation of attenuation-corrected images acquired with multi-pinhole cameras, knowledge of NDB uncertainty gradients should be taken into consideration.