Statistical list-mode image reconstruction for the high resolution research tomograph

Abstract

We have investigated statistical list-mode reconstruction applicable to a depth-encoding high resolution research tomograph. An image non-negativity constraint has been employed in the reconstructions and is shown to effectively remove the overestimation bias introduced by the sinogram non-negativity constraint. We have furthermore implemented a convergent subsetized (CS) list-mode reconstruction algorithm, based on previous work (Hsiao et al 2002 Conf. Rec. SPIE Med. Imaging 4684 10-19; Hsiao et al 2002 Conf. Rec. IEEE Int. Symp. Biomed. Imaging 409-12) on convergent histogram OSEM reconstruction. We have demonstrated that the first step of the convergent algorithm is exactly equivalent (unlike the histogram-mode case) to the regular subsetized list-mode EM algorithm, while the second and final step takes the form of additive updates in image space. We have shown that in terms of contrast, noise as well as FWHM width behaviour, the CS algorithm is robust and does not result in limit cycles. A hybrid algorithm based on the ordinary and the convergent algorithms is also proposed, and is shown to combine the advantages of the two algorithms (i.e. it is able to reach a higher image quality in fewer iterations while maintaining the convergent behaviour), making the hybrid approach a good alternative to the ordinary subsetized list-mode EM algorithm.

Effects of multiple‐interaction photon events in a high‐resolution PET system that uses 3‐D positioning detectors

“…19 The geometrical sensitivity, including photon attenuation, was measured by simulating a normalization phantom, consisting of a uniformly radioactive slab of water occupying the entire FOV with 50 Ci of total activity. Backprojecting all the LORs in the system for computing the sensitivity map would be a daunting task since the breast PET system has more than 19.6 billion LORs.…”

Research of the system response of neutron double scatter imaging for MLEM reconstruction

“…The MLEM [7,8] is often used in astronomy and medical imaging. In neutron double scatter imaging, in order to overcome the difficulty with restoring an enormous set of measurement data, listmode acquisition is achieved by regarding the acquired events as they were detected one-by-one in the form of a list [6].…”

PET for cerebrovascular diseases: status and limitation

“…At first a non-negativity constrain on the update factor was introduced, however this was found to cause a significant positive bias in the images [6]. This problem stimulated significant development in the image reconstruction area, which lead to the practical implementation of the currently most widely accepted reconstruction method, Ordinary Poisson-OSEM [7][8][9], where the images are recosntructed using the following expression:…”

“…Since the HRRT is capable of acquiring data in list mode, it is often advantageous to reconstruct the data directly from the list mode file as opposed to first assigning the data to sinogram bins. As a consequence several groups have explored list mode based reconstruction algorithms [6,[13][14][15] of which a particular implementation results into the following modifications of the expression listed above: …”