The authors define ordered subset processing for standard algorithms (such as expectation maximization, EM) for image restoration from projections. Ordered subsets methods group projection data into an ordered sequence of subsets (or blocks). An iteration of ordered subsets EM is defined as a single pass through all the subsets, in each subset using the current estimate to initialize applicatio...

This work presents new mathematical results on the inversion of the exponential x-ray transform. It is shown that a reconstruction formula can be obtained for any dataset whose projection directions consist of a union of half great circles on the unit sphere. A basic example of such a dataset is the semi-equatorial band. The discussion in the paper is mostly focused on this example. The reconst...

Single-photon emission computed tomography (SPECT) is based on the measurement of radiation emitted by a radiotracer injected into the patient. Because of photoelectric absorption and Compton scatter, the γ photons are attenuated inside the body before arriving at the detector. A quantitative reconstruction must consider the attenuation, which is usually non-uniform. Novikov and Natterer had de...

UNLABELLED SPECT imaging of the pelvis is hampered by the presence of bladder artifacts, which render up to 20% of the images unreadable. The artifacts are caused by the high level of activity in the bladder and by the change in activity level as the bladder fills during data acquisition. The changing activity, together with the inhomogeneous attenuation of the pelvis, leads to inconsistencies ...

BACKGROUND & OBJECTIVES Preoperative localization of parathyroid lesions is essential for improving the results in patients with primary hyperparathyroidism. The purpose of this study was to evaluate retrospectively the value of technetium-99m (Tc-99m) methoxyisobutylisonitrile (MIBI) single photon emission computed tomography (SPECT) and to compare the diagnostic accuracy of iterative reconstr...

introduction: acceptance test is a necessary procedure after spect system installation. the goal of this test is to reveal system's present condition, to compare it with manufacturer's specifications and also as a base for later tests. methods: this study investigated four spect systems in tehran. all of the quality control tests are performed on the basis of nema and iaea recommendations and b...

Single photon emission computed tomography (SPECT) imaging is widely implemented in nuclear medicine as its clinical role in the diagnosis and management of several diseases is, many times, very helpful (e.g., myocardium perfusion imaging). The quality of SPECT images are degraded by several factors such as noise because of the limited number of counts, attenuation, or scatter of photons. Image...

This review sets out to discuss the foremost applications of artificial intelligence (AI), particularly deep learning (DL) algorithms, in single-photon emission computed tomography (SPECT) and positron (PET) imaging. To this end, underlying limitations/challenges these imaging modalities are briefly discussed followed by a description AI-based solutions proposed address challenges. will focus o...

Respiratory motion can blur the tomographic reconstruction of positron emission tomography or single-photon emission computed tomography (SPECT) images, which subsequently impair quantitative measurements, e.g. in the upper abdomen area. Respiratory signal phase-based gated reconstruction addresses this problem, but deteriorates the signal-to-noise ratio (SNR) and other intensity-based quality ...

We apply a uniform Cramer-Rao (CR) bound [l] to study the bias-variance trade-offs in single photon emission computed tomography (SPECT) image reconstruction. The uniform CR bound is used to specify achievable and unachievable regions in the bias-variance trade-off plane. The image reconstruction algorithms considered in this paper are: 1) Space alternating generalized EM and 2) penalized weigh...