Iterative Ordered Subsets Expectation Maximization Research Articles

Quantitative simultaneous /sup 99m/Tc//sup 123/I SPECT: design study and validation with Monte Carlo simulations and physical acquisitions

Simultaneous dual isotope imaging (/sup 99m/Tc//sup 123/I) has potential clinical applications but has not been implemented in the clinic. The aim of this work was to design an artificial neural network (ANN) for crosstalk and scatter correction using a smaller number of energy windows (8) than we had previously proposed (26) to allow implementation on some clinical cameras, and to validate our approach using realistic Monte Carlo simulations and anthropomorphic brain phantom acquisitions. Monte Carlo simulations of dual isotope SPECT studies of a digital brain phantom and physical acquisitions of the striatal brain phantom were used to validate our approach. Corrected projections were reconstructed using an iterative ordered subsets expectation maximization (OSEM) algorithm that modeled nonuniform attenuation and variable collimator response in the projector/backprojector. Results: In Monte Carlo simulations, ANN26 and ANN8 yielded similarly accurate quantitation of /sup 123/I activity (bias <7%) in all brain structures. An asymmetric windowing method (AW) yielded accurate estimation in the striata (bias <7%) but not in other brain structures. The estimation bias of /sup 99m/Tc primary activity was <10% in all brain structures with ANN26 and ANN8.

Rotating slant-hole single-photon emission-computed tomography

This dissertation presents a detailed investigation of the use of rotating slant-hole (RSH) collimators in single-photon emission-computed tomography(SPECT). We propose RSH SPECT as an alternative imaging technique, which may have advantages over more traditional SPECT techniques, in certain imaging applications. The basic imaging properties of RSH collimators are derived. This includes the derivation of expressions for the size and location of the common volume of view and the geometric resolution and efficiency. In addition, we derive an analytical expression for the geometric response and transfer functions of RSH collimators. The theoretical expressions for the aforementioned imaging characteristics are verified via Monte Carlo simulations and phantom experiments. Next, we present the development of a three-dimensional (3-D) analytic reconstruction algorithm for RSH SPECT. This includes the derivation of both a backprojection of the filtered projections and a filtering of the simple backprojections (BpjF) algorithm. The relationship between the derived 3-D RSH reconstruction filter and a number of other reconstruction filters is discussed. In addition, the implementation of the BpjF reconstruction algorithm is described and its performance is demonstrated via simulations and phantom experiments. We have also implemented an iterative ordered-subsets expectation-maximization (OS-EM) reconstruction algorithm for RSH SPECT. A detailed description of the development of the projector/backprojector employed by the OS-EM algorithm is provided. Simulation and phantom experiments are again used to demonstrate the performance of the projector/backprojector and the iterative OS-EM reconstruction algorithm. Rotating slant-hole SPECT has potential applications in cardiac and breast imaging. Thus, we demonstrate the feasibility, advantages, and disadvantages of using RSH SPECT via a comparison with conventional SPECT in a cardiac and breast imaging phantom experiment. In conclusion, we summarize the results presented and discuss their implications on the current and future state of RSH SPECT research.