Background: The positron emission tomography (PET) technology has undergone continuous innovation in recent years. New-technology digital PETs are silicon photomultiplier (SiPM) PET systems with digital readouts, which contribute to improved image resolution. This study aimed to compare the image quality of sub-centimeter lesions of NEMA PET phantom images obtained under identical imaging conditions (identical lesion volumes, identical activity and identical scanning time) using dPET, analog PET-1 and analog PET-2 acquired in the clinic. Materials and Methods: For image analysis, a standard NEMA IEC body phantom was used. In the present study, the lesion detection performance of all PETs was evaluated in two categories, sub- and over-centimeter size. The imaging durations of this study were 1, 2, 3, and 5 minutes, while the injection doses were 2.33 and 5.33 kBq/ml for the 1/4 and 1/8 background-to-lesion ratios, respectively. For a quantitative assessment of image quality, a circular ROI with activity concentrations (ACmean) and the mean recovery coefficient were calculated for each lesion via the ACmean. Results: Our study revealed approximately 15% greater RCmean values for dPET with SiPM technology compared to the analog PET-2 with PMT technology. However, analog PET-1 exhibited a significant lack of performance, especially when compared to analog PET-2 and dPET. Conclusion: Although dPET, the first generation of dPETs analyzed in the present study, yields relatively better RCmean values than analog PETs, it is not able to entirely eliminate the unfavorable impacts of PVE for sub-centimeter lesions.

In this paper, we review novel techniques in the emerging field of spatiotemporal 4D PET imaging. We will discuss existing limitations in conventional dynamic PET imaging which involves independent reconstruction of dynamic PET datasets. Various approaches that seek to attempt some or all of these limitations are reviewed in this work, including techniques that utilize iterative temporal smoothing, advanced temporal basis functions, principal components transformation of the dynamic data, wavelet-based techniques as well as direct kinetic parameter estimation methods. Extension of 4D PET to 5D PET in which the additional dimension of (respiratory or cardiac) gating is considered has also been discussed.

PET (Positron Emission Tomography) is a powerful imaging technique through which quantitative information on the distribution of positron emitter labeled radiopharmaceuticals (PET radiopharmaceuticals) in the body can be realized. Positrons (b+) are positively charged beta particles. They are emitted when the atom is proton enriched. A positron has only a transient existence. After losing all of its kinetic energy, it interacts with an electron and is annihilated. Both the mass of positron and electron are converted to energy during annihilation and two 511 KeV photons are emitted at a 180° angle to each other. The PET is based on the coincidence detection of the two aforementioned photons. Coincidence detection is a powerful method enhancing sensitivity and dynamic-imaging capabilities of PET. PET camera systems contain a ring of detectors that encircles the patient. The data collected over many angles around the body axis of the patient is used to reconstruct the image of the activity distribution in slice or tomographic form.

In this paper we define the p-analog of the restricted representations and the p-analog of the Fourier-Stieltjes algebras on inverse semigroups and also we improve some results about Herz algebras on Clifford semigroups, and we give a necessary and sufficient condition for amenability of these algebras on Clifford semigroups.