scholarly journals Deep-Learning Based Positron Range Correction of PET Images

2020 ◽  
Vol 11 (1) ◽  
pp. 266
Author(s):  
Joaquín L. Herraiz ◽  
Adrián Bembibre ◽  
Alejandro López-Montes
Keyword(s):  
Imaging Technique ◽  
High Energy ◽  
The Body ◽  
Emission Tomography ◽  
Small Animals ◽  
Positron Energy ◽  
Positron Range ◽  
Positron Emission ◽  
Range Correction

Positron emission tomography (PET) is a molecular imaging technique that provides a 3D image of functional processes in the body in vivo. Some of the radionuclides proposed for PET imaging emit high-energy positrons, which travel some distance before they annihilate (positron range), creating significant blurring in the reconstructed images. Their large positron range compromises the achievable spatial resolution of the system, which is more significant when using high-resolution scanners designed for the imaging of small animals. In this work, we trained a deep neural network named Deep-PRC to correct PET images for positron range effects. Deep-PRC was trained with modeled cases using a realistic Monte Carlo simulation tool that considers the positron energy distribution and the materials and tissues it propagates into. Quantification of the reconstructed PET images corrected with Deep-PRC showed that it was able to restore the images by up to 95% without any significant noise increase. The proposed method, which is accessible via Github, can provide an accurate positron range correction in a few seconds for a typical PET acquisition.

Positron Emission Tomography: Clinical Applications and Pharmaceutical Care

1994 ◽  
Vol 7 (3) ◽  
pp. 124-139 ◽  
Author(s):  
Richard J. Hammes ◽  
John W. Babich
Keyword(s):  
Positron Emission Tomography ◽  
Imaging Technique ◽  
Three Dimensional ◽  
Building Blocks ◽  
Emission Tomography ◽  
Pharmacokinetic Parameters ◽  
Nuclear Medicine Imaging ◽  
Receptor Ligands ◽  
Positron Emission

Positron emission tomography {PET) is a nuclear medicine imaging technique which exploits the unique physical characteristics of radionuclides that decay by positron emission. These characteristics allow for in vivo quantitative measurement of three-dimensional distributions of radioactivity with a spatial resolution of 5 mm using current detector technology. In addition to these physical advantages, PET is the only imaging technique that can use the short-lived positron emitting radionuclides of the so-called “organic” elements: carbon (C-11), nitrogen (N-13), and oxygen (0–15). These elements are the building blocks of physiological compounds and can be used to study most enzymes, receptors, and other metabolically important compounds and their associated reactions. PET allows for the study of a variety of physiological and biochemical processes through the application of particular radiopharmaceuticals. PET has also been used to study the interaction of receptor-specific ligands in several receptor systems including dopaminergic, adrenergic, serotinergic, and opiod. C-11 and F-18 labeled receptor ligands have been used to study receptor selectivity and receptor concentrations in vivo. Recently, PET has been used to measure the pharmacokinetics of several novel antibiotics in humans allowing the direct measurement of tissue concentrations and correlation with classical pharmacokinetic parameters. This review discusses some of the current applications of PET in more detail.

scholarly journals [68Ga]ABY-028: an albumin-binding domain (ABD) protein-based imaging tracer for positron emission tomography (PET) studies of altered vascular permeability and predictions of albumin-drug conjugate transport

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Emma Jussing ◽  
Li Lu ◽  
Jonas Grafström ◽  
Tetyana Tegnebratt ◽  
Fabian Arnberg ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Vascular Permeability ◽  
Ex Vivo ◽  
Circulatory System ◽  
Binding Domain ◽  
The Body ◽  
Emission Tomography ◽  
Albumin Binding ◽  
Positron Emission

Abstract Background Albumin is commonly used as a carrier platform for drugs to extend their circulatory half-lives and influence their uptake into tissues that have altered permeability to the plasma protein. The albumin-binding domain (ABD) protein, which binds in vivo to serum albumin with high affinity, has proven to be a versatile scaffold for engineering biopharmaceuticals with a range of binding capabilities. In this study, the ABD protein equipped with a mal-DOTA chelator (denoted ABY-028) was radiolabeled with gallium-68 (68Ga). This novel radiotracer was then used together with positron emission tomography (PET) imaging to examine variations in the uptake of the ABD-albumin conjugate with variations in endothelial permeability. Results ABY-028, produced by peptide synthesis in excellent purity and stored at − 20 °C, was stable for 24 months (end of study). [68Ga]ABY-028 could be obtained with labeling yields of > 80% and approximately 95% radiochemical purity. [68Ga]ABY-028 distributed in vivo with the plasma pool, with highest radioactivity in the heart ventricles and major vessels of the body, a gradual transport over time from the circulatory system into tissues and elimination via the kidneys. Early [68Ga]ABY-028 uptake differed in xenografts with different vascular properties: mean standard uptake values (SUVmean) were initially 5 times larger in FaDu than in A431 xenografts, but the difference decreased to 3 after 1 h. Cutaneously administered, vasoactive nitroglycerin increased radioactivity in the A431 xenografts. Heterogeneity in the levels and rates of increases of radioactivity uptake was observed in sub-regions of individual MMTV-PyMT mammary tumors and in FaDu xenografts. Higher uptake early after tracer administration could be observed in lower metabolic regions. Fluctuations in the increased permeability for the tracer across the blood-brain-barrier (BBB) direct after experimentally induced stroke were monitored by PET and the increased uptake was confirmed by ex vivo phosphorimaging. Conclusions [68Ga]ABY-028 is a promising new tracer for visualization of changes in albumin uptake due to disease- and pharmacologically altered vascular permeability and their potential effects on the passive uptake of targeting therapeutics based on the ABD protein technology.

scholarly journals Novel PET Biomarkers to Disentangle Molecular Pathways across Age-Related Neurodegenerative Diseases

Cells ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 2581
Author(s):  
Heather Wilson ◽  
Marios Politis ◽  
Eugenii A. Rabiner ◽  
Lefkos T. Middleton
Keyword(s):  
Neurodegenerative Diseases ◽  
Protein Misfolding ◽  
Imaging Technique ◽  
Emission Tomography ◽  
Imaging Biomarkers ◽  
Synaptic Dysfunction ◽  
Molecular Pathways ◽  
Age Related ◽  
Positron Emission

There is a need to disentangle the etiological puzzle of age-related neurodegenerative diseases, whose clinical phenotypes arise from known, and as yet unknown, pathways that can act distinctly or in concert. Enhanced sub-phenotyping and the identification of in vivo biomarker-driven signature profiles could improve the stratification of patients into clinical trials and, potentially, help to drive the treatment landscape towards the precision medicine paradigm. The rapidly growing field of neuroimaging offers valuable tools to investigate disease pathophysiology and molecular pathways in humans, with the potential to capture the whole disease course starting from preclinical stages. Positron emission tomography (PET) combines the advantages of a versatile imaging technique with the ability to quantify, to nanomolar sensitivity, molecular targets in vivo. This review will discuss current research and available imaging biomarkers evaluating dysregulation of the main molecular pathways across age-related neurodegenerative diseases. The molecular pathways focused on in this review involve mitochondrial dysfunction and energy dysregulation; neuroinflammation; protein misfolding; aggregation and the concepts of pathobiology, synaptic dysfunction, neurotransmitter dysregulation and dysfunction of the glymphatic system. The use of PET imaging to dissect these molecular pathways and the potential to aid sub-phenotyping will be discussed, with a focus on novel PET biomarkers.

scholarly journals Rapid Feasibility Studies of Tracers for Positron Emission Tomography: High-Resolution PET in Small Animals with Kinetic Analysis

1991 ◽  
Vol 11 (6) ◽  
pp. 926-931 ◽  
Author(s):  
M. Ingvar ◽  
L. Eriksson ◽  
G. A. Rogers ◽  
S. Stone-Elander ◽  
L. Widén
Keyword(s):  
Positron Emission Tomography ◽  
Emission Tomography ◽  
Whole Body ◽  
Small Animals ◽  
Pharmacological Properties ◽  
Time Activity ◽  
Pet Tracers ◽  
Arterial Blood ◽  
Positron Emission

The development of methods for production of a radiotracer for use in human studies with positron emission tomography (PET) is often a time-consuming process of optimizing radiolabelling yields and handling procedures. Sometimes the radiotracer is not the original drug, but rather a derivative with unknown in vivo pharmacological properties. We have developed a fast and simple method of testing putative new PET tracers in vivo in small animals. The procedure has been validated in rats with different PET tracers with known kinetic and pharmacological properties ([2-18F]2-fluoro-2-deoxy-d-glucose, [ N-methyl-11C]Ro 15-1788, and [15O]butanol). The tracer concentration in arterial blood was continuously measured to obtain the brain input function. Following image reconstruction of the scans, time–activity curves of selected regions of interest were generated. Estimations of CMRglc (1.0 ± 0.2 μmol g−1 min−1), CBF (1.4 ± 0.4 ml g−1 min−1) and transport rate constants for [ N-methyl-11C]Ro 15-1788 (K1 = 0.44 ± 0.01 ml g−1 min−1 and k2 = 0.099 ± 0.005 min−1) as well as calculated first pass extraction (0.32 ±0.1) are in reasonable agreement with literature values. Small animal studies require minimal amounts of radioactivity and can be performed without sterility and toxicology tests. They may serve as a preliminary basis for radiation safety calculations because whole body scans can be performed even with a head scanner. The major advantage of this procedure in comparison to ex vivo autoradiography is that very few experiments are necessary to reliably determine the properties of the blood–brain barrier transport of the radiotracer and the possible whole brain receptor binding characteristics.

scholarly journals CellGPS: Whole-body tracking of single cells by positron emission tomography

2019 ◽  
Author(s):  
Kyung Oh Jung ◽  
Tae Jin Kim ◽  
Jung Ho Yu ◽  
Siyeon Rhee ◽  
Wei Zhao ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Single Cells ◽  
The Body ◽  
Emission Tomography ◽  
Whole Body ◽  
Cell Trafficking ◽  
Anatomical Landmarks ◽  
Average Cell ◽  
Positron Emission

AbstractIn vivo molecular imaging tools are critically important for determining the role played by cell trafficking in biological processes and cellular therapies. However, existing tools measure average cell behavior and not the kinetics and migration routes of individual cells inside the body. Furthermore, efflux and non-specific accumulation of contrast agents are confounding factors, leading to inaccurate estimation of cell distribution in vivo. In view of these challenges, we report the development of a “cellular GPS” capable of tracking single cells inside living subjects with exquisite sensitivity. We use mesoporous silica nanoparticles (MSN) to concentrate 68Ga radioisotope into live cells and inject these cells into live mice. From the pattern of annihilation photons detected by positron emission tomography (PET), we infer, in real time, the position of individual cells with respect to anatomical landmarks derived from X-ray computed tomography (CT). To demonstrate this technique, a single human breast cancer cell was tracked in a mouse model of experimental metastasis. The cell arrested in the lungs 2-3 seconds after tail-vein injection. Its average velocity was estimated at around 50 mm/s, consistent with blood flow rate. Other cells were tracked after injection through other routes, but no motion was detected within 10 min of acquisition. Single-cell tracking could be applied to determine the kinetics of cell trafficking and arrest during the earliest phase of the metastatic cascade, the trafficking of immune cells during cancer immunotherapy, or the distribution of cells after transplantation in regenerative medicine.

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