Advances in Preclinical PET

A pre-clinical PET scanner based on a monolithic annulus of scintillator (AnnPET): construction and NU4-2008 performance testing

Objective.In the past several decades, numerous positron emission tomography (PET) scanners of various designs have been constructed for use in pre-clinical studies. Our group is investigating use of a monolithic annulus of scintillator, instead of the traditional arrays of discrete scintillator elements or individual detectors that utilize continuous blocks of scintillator, to construct a novel pre-clinical PET scanner.Approach.This scanner, called AnnPET, is based on a fourteen-faceted annulus of lutetium yttrium orthosilicate with an inner diameter of 6 cm and length of 7.2 cm. Each facet is populated with four specially constructed 4 × 4 arrays of 4 mm × 4 mm multi-pixel photon counters .To cool and temperature stabilize these devices, the scanner gantry is immersed in dielectric fluid. Positioning of events in the scintillator is accomplished with the application of deep-residual convolutional neural network. The scanner's performance was assessed using the NEMA NU4-2008 protocols.Results.Full-width-at-half-maximum (FWHM) of the images of a point source reconstructed with the single slice rebinned filtered backprojection (SSRB-FBP) algorithm at 5 mm from the center of the scanner are: 1.40 mm (radial), 1.38 mm (tangential) and 1.40 mm (axial). At 18 mm from scanner center (edge of the scanner's inner bore) the FWHMs are: 1.62 mm (radial), 1.43 mm (tangential) and 1.48 mm (axial) FWHM. Peak detection sensitivity is 9.5% (0.086 cps Bq-1). Peak noise equivalent count rate is 234 kcps at 14.4 MBq.Significance.Overall, testing of the AnnPET system demonstrated very promising performance results for a pre-clinical PET scanner based on a single, cooled annulus of monolithic scintillator used with neural networks. Continued development of the system is planned.

Preclinical magnetic resonance imaging and spectroscopy in the fields of radiological technology, medical physics, and radiology

Magnetic resonance imaging (MRI) is an indispensable diagnostic imaging technique used in the clinical setting. MRI is advantageous over X-ray and computed tomography (CT), because the contrast provided depends on differences in the density of various organ tissues. In addition to MRI systems in hospitals, more than 100 systems are used for research purposes in Japan in various fields, including basic scientific research, molecular and clinical investigations, and life science research, such as drug discovery, veterinary medicine, and food testing. For many years, additional preclinical imaging studies have been conducted in basic research in the fields of radiation technology, medical physics, and radiology. The preclinical MRI research includes studies using small-bore and whole-body MRI systems. In this review, we focus on the animal study using small-bore MRI systems as "preclinical MRI". The preclinical MRI can be used to elucidate the pathophysiology of diseases and for translational research. This review will provide an overview of previous preclinical MRI studies such as brain, heart, and liver disease assessments. Also, we provide an overview of the utility of preclinical MRI studies in radiological physics and technology.

A look at radiation detectors and their applications in medical imaging

The effectiveness and precision of disease diagnosis and treatment have increased, thanks to developments in clinical imaging over the past few decades. Science is developing and progressing steadily in imaging modalities, and effective outcomes are starting to show up as a result of the shorter scanning periods needed as well as the higher-resolution images generated. The choice of one clinical device over another is influenced by technical disparities among the equipment, such as detection medium, shorter scan time, patient comfort, cost-effectiveness, accessibility, greater sensitivity and specificity, and spatial resolution. Lately, computational algorithms, artificial intelligence (AI), in particular, have been incorporated with diagnostic and treatment techniques, including imaging systems. AI is a discipline comprised of multiple computational and mathematical models. Its applications aided in manipulating sophisticated data in imaging processes and increased imaging tests' accuracy and precision during diagnosis. Computed tomography (CT), positron emission tomography (PET), and Single Photon Emission Computed Tomography (SPECT) along with their corresponding radiation detectors have been reviewed in this study. This review will provide an in-depth explanation of the above-mentioned imaging modalities as well as the radiation detectors that are their essential components. From the early development of these medical instruments till now, various modifications and improvements have been done and more is yet to be established for better performance which calls for a necessity to capture the available information and record the gaps to be filled for better future advances.

Innovations in Small-Animal PET Instrumentation

Biomedical research has long relied on small-animal studies to elucidate disease process and develop new medical treatments. The introduction of in vivo functional imaging technology, such as PET, has allowed investigators to peer inside their subjects and follow disease progression longitudinally as well as improve understanding of normal biological processes. Recent developments in CRISPR, immuno-PET, and high-resolution in vivo imaging have only increased the importance of small-animal, or preclinical, PET imaging. Other drivers of preclinical PET innovation include new combinations of imaging technologies, such as PET/MR imaging, which require changes to PET hardware.

Preclinical Imaging Studies: Protocols, Preparation, Anesthesia, and Animal Care

Today preclinical PET imaging connects laboratory research with clinical applications. Here PET clearly bridges the gap, as nearly identical imaging protocols can be applied to both animal and humans. However, some hurdles exist and researchers must be careful, partly because the animals are usually anesthetized during the scans, while human volunteers are awake. This review is based on our own experiences of some of the most important pitfalls and how to overcome them. This includes how studies should be designed, how to select the right anesthesia and monitoring. The choice of anesthesia is quite crucial, as it may have a greater influence on the results than the effect of the tested procedures. Monitoring is necessary, as the animals cannot fully maintain homeostasis during anesthesia, and reliable results are dependent on a stable physiology. Additionally, it is important to note that rodents, in particular, are prone to rapidly becoming hypothermic. Thus, the selection of an appropriate anesthetic and monitoring protocol is crucial for both obtaining accurate results and ensuring animal welfare. Prior to imaging, catheters for tracer administration and, if necessary, blood sampling should be implanted. The administration of tracers should be done in a manner that minimizes interference with the scans, and the same applies to any serial blood sampling. The limited blood volume and organ size of rodents should also be taken into consideration when planning experiments. Finally, if the animal needs to be awakened after the scan, proper care must be taken to ensure their welfare.