Biological Sciences
PET Scan
A PET scan, or positron emission tomography scan, is a medical imaging technique that uses a radioactive substance to create 3D images of the body's functional processes. It is commonly used to detect diseases such as cancer, assess brain function, and evaluate heart conditions. PET scans can provide detailed information about the body's metabolism and help in diagnosing and monitoring various medical conditions.
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12 Key excerpts on "PET Scan"
- Nick Van Bruggen, Timothy P.L. Roberts, Nick Van Bruggen, Timothy P.L. Roberts(Authors)
- 2002(Publication Date)
- CRC Press(Publisher)
Positron emission tomography (PET) has been used for a number of years in the study of the function and neurochemistry in the human and nonhuman primate brain. 1 PET is a noninvasive and extremely safe imaging modality that allows for repeated observations in an individual. The adaptation of PET to repeatedly and noninvasively image small animals represents a unique opportunity to explore neu-roplasticity and neuropathology in living rodents. This chapter will describe the basic physical principles underlying PET imaging, review some of the work that has successfully utilized PET in rodent brain imaging, and will indicate future directions for rodent research with PET. 9.2 BASIC PRINCIPLES OF POSITRON EMISSION TOMOGRAPHY IMAGING PET is a radiotracer imaging technique that utilizes small amounts of a compound or biomolecule of interest labeled with radioactive atoms. The radiation emitted as the radioactive label decays is picked up by a series of external detectors and the resulting information is used to compute images that show the distribution of the Small Animal Imaging with Positron Emission Tomography 273 radioactive tracer in the subject. PET can essentially be thought of as a noninvasive version of autoradiography, with inferior spatial resolution, but with the advantages that the pharmacokinetics of the tracer can be measured in a single experiment and repeat studies can be performed on the same subject. 9.2.1 P OSITRON -E MITTING R ADIONUCLIDES AND T RACERS PET imaging makes exclusive use of radionuclides that decay by positron emission. Table 9.1 lists commonly used positron-emitting radionuclides. Some of the radio-nuclides are isotopes of biologically ubiquitous elements such as carbon, nitrogen, and oxygen, enabling radioactively labeled tracers of small organic molecules to be produced by direct isotopic substitution, for example, by replacing a stable carbon-12 atom with a positron-emitting carbon-11 atom.
eBook - PDF- Shan Xiang Wang, Adam de la Zerda(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
PET is a nuclear medicine tomographic imaging technique that uses a tracer compound labeled with a radionuclide that is a positron emitter. A PET study yields cross sectional image slices representing uptake/biodistribution of the radioactively labeled chemical. PET provides quantitative information of rates of biological processes, such as metabolism, cell prolif- eration, etc. uni03B3 Unstable nucleus in a labeled compound emits a positron e – e + uni03B3 Detector Detector Positron trajectory Positron annihilates with electron Two 511 photons are emitted simultaneously in opposite directions Figure 14.4 Positron annihilation with an electron. Source: Zereshk [2]. CC0-1.0 public domain https://creativecommons.org/publicdomain/zero/1.0/ . Photon “detectors” Figure 14.5 PET Scan. Source: Image courtesy of Dr. Craig Levin. 14 Radionuclide Imaging 300 14.2.1 Types of Coincidences True coincidence is the simultaneous detection of the two emissions resulting from a single decay event, which indicates that the annihilation location occurred somewhere along a straight line between the two detectors. A scatter coincidence occurs when one or both photons from a single event are scattered and both are detected, resulting in an incorrectly drawn line (mistake). One way to counteract scatter coincidences is to use photodetectors that only respond to specific photon energies since photons change energy after scattering. A random coincidence is the simultaneous detection of emission from more than one decay event, which will also result in an incorrectly drawn line. Each of these three coincidence types is depicted in Figure 14.6. 14.2.2 Basics of PET – Detector A PET detector consists of a scintillation crystal and a photomultiplier tube (PMT), shown in Figure 14.7. The scintillation crystal converts an X-ray photon (gamma ray) to many (tens of thou- sands) visible photons.
eBook - ePubHandbook of In Vivo Chemistry in Mice
From Lab to Living System
- Katsunori Tanaka, Kenward Vong(Authors)
- 2019(Publication Date)
- Wiley-VCH(Publisher)
5 Positron Emission Tomography (PET) Imaging in Live AnimalsXiaowei Ma and Zhen ChengStanford University, Department of Radiology, 1201 Welch Road, Lucas Center, P095, Stanford, CA, 94305‐5484, USA5.1 Introduction
Positron emission tomography (PET ) is a highly sensitive noninvasive functional imaging technology that is ideally suited for monitoring the molecular biological processes in the course of diseases in vivo. By detecting the gamma rays emitted from the radioisotope‐labeled tracer in the body, three‐dimensional images can be reconstructed to show the location and concentration of the tracer corresponding to the bioactivities. PET imaging can obtain different information of diseases such as diagnostic and/or prognostic information by using different kinds of radioisotope‐labeled tracers. It can be used to monitor perfusion, metabolic rate, gene expression, protein expression, receptor binding, and many other events. With noninvasive PET imaging, we can investigate disease progression or molecular change in real time in vivo. The power of PET makes it an attractive technology in standard medical care in recent years.The decisive influence of PET imaging in preclinical usage has motivated scientists to develop a miniaturized version of a PET Scanner called micro‐PET for noninvasive molecular imaging of laboratory animals. With the tremendous advances in biotechnology, a wide range of small laboratory animal models, such as mice and rats, have been used to study human disease progress. Therefore, it has significantly motivated the extent of PET technique for small‐animal imaging. With the galloping progress of technology, many micro‐PET Scanners have been designed and made with high performance. They have facilitated the development of molecular imaging assays in small‐animal models, which is a very important basis for clinical translation. The micro‐PET imaging studies could supply pharmacokinetic data of tracers and optimize the imaging signal acquirement. Micro‐PET Scanners have played a crucial role in biology, scientific research, and drug development for many kinds of diseases such as tumor, neurological diseases, and cardiovascular diseases. One of the most important and powerful feature of micro‐PET is the ability to validate tracers in animal models and then translate them from these preclinical models to clinical applications using the same tracers in clinical PET sites around the world.
- Darin D. Dougherty, Scott L. Rauch, Jerrold F. Rosenbaum, Darin D. Dougherty, Scott L. Rauch, Jerrold F. Rosenbaum(Authors)
- 2008(Publication Date)
- American Psychiatric Association Publishing(Publisher)
75 3 Positron Emission Tomography and Single Photon Emission Computed Tomography Darin D. Dougherty, M.D., M.Sc. Scott L. Rauch, M.D. Alan J. Fischman, M.D., Ph.D. Whereas computed tomography (CT; see Chapter 1 in this volume) and magnetic resonance imaging (MRI; see Chapter 2 in this volume) provide structural im- ages of the brain, positron emission tomography (PET) and single photon emission computed tomography (SPECT) are radiological technologies that are used to measure numerous aspects of brain function. PET and SPECT, along with functional magnetic resonance im- aging (fMRI; see Chapter 4 in this volume), are power- ful tools for neuroscience research. Although PET and SPECT are still primarily research tools in the field of psychiatry, there is growing clinical utility for these methodologies. We begin this chapter by briefly de- scribing the principles that underlie these methods. We then discuss the use of PET and SPECT in both the clin- ical psychiatry and neuroscience research environ- ments. Finally, we propose future directions for the use of PET and SPECT in psychiatry. Principles of PET and SPECT Positron Emission Tomography Positron Emission PET measures radioactive decay in order to form im- ages of biological tissue function. Specifically, unstable 76 ESSENTIALS OF NEUROIMAGING FOR CLINICAL PRACTICE nuclides are introduced into the organism being stud- ied, and the PET camera detects the resulting radioac- tive decay and uses these data to construct functional images. Commonly used positron-emitting nuclides in PET studies include 11-carbon ( 11 C), 15-oxygen ( 15 O), 18-fluorine ( 18 F), and 13-nitrogen ( 13 N) (Table 3– 1). These nuclides are incorporated into the desired molecules, resulting in a radiopharmaceutical (see subsection titled “Radiopharmaceuticals” later in this chapter).
eBook - PDF- Raymond Taillefer, Iraj Khalkhali, Alan D. Waxman, Hans J. Biersack, Raymond Taillefer, Iraj Khalkhali, Alan D. Waxman, Hans J. Biersack(Authors)
- 2021(Publication Date)
- CRC Press(Publisher)
4 Breast Imaging with Positron Emission Tomography HANS BENDER, HoLGER PALMEDO, and HANS J. BIERSACK University of Bonn, Bonn, Germany AxEL SCHOMBURG Roentgeninstitut. Dusseldorf. Germany I. INTRODUCTION A. Historical Background Positron emission tomography (PET) is a cross-sectional, nuclear medicine imag- ing technique that provides functional images of the body (e.g., by visualization of metabolic processes, expression of transporters, receptors, etc.). PET combines a series of characteristics/abilities that could not be realized in standard nuclear medicine applications: 1. Quantitation: While gamma rays can not be focused like visible light, the collimator technology allows a sufficient but limited substitute. The major limitation is due to the fact that gamma rays can not be stopped but only attenu- ated. By this way, the assumed volume of an imaged lesion is related to the accu- mulated activity. Thus, the higher the accumulated activity within a defined vol- ume, the larger it appears on the display unit. 2. Resolution: The above-mentioned physical limitation of single-gamma ray imaging does not only limit true/accurate volume estimates but also limits the resolution of the system. In addition, deeply located and small lesions are signifi- cantly masked by attenuation and scatter, while the detected size seems to increase with the distance of the object from the collimator. 3. Production of biologically identical tracers: Certain positron emitters (1 1 C, ' 5 0, 13 N) are the building blocks of organic compounds as they are used in 147 148 BENDER ET AL. living organisms. Substitution of the stable isotope by its radioactive form allows the production of biologically identical substances, which are substrate and tracer of a pertaining and highly specific metabolic pathway at the same time.
eBook - PDF- Joseph D. Bronzino, Donald R. Peterson, Joseph D. Bronzino, Donald R. Peterson(Authors)
- 2014(Publication Date)
- CRC Press(Publisher)
1987. Physics in Nuclear Medicine. New York, Grune & Stratton. Steigman, J. and Eckerman, W.C. 1992. The Chemistry of Technetium in Medicine. Washington, National Academy Press. Stocklin, G. 1992. Tracers for metabolic imaging of brain and heart: radiochemistry and radiopharmacol-ogy. Eur. J. Nucl. Med. 19: 527. 14.2 Instrumentation Thomas F. Budinger 14.2.1 Background The history of positron-emission tomography (PET) can be traced to the early 1950s, when workers in Boston first realized the medical imaging possibilities of a particular class of radioactive substances. It was recognized then that the high-energy photons produced by annihilation of the positron from positron-emitting isotopes could be used to describe, in three dimensions, the physiologic distribution of “tagged” chemical compounds. After two decades of moderate technological developments by a few research cen-ters, widespread interest and broadly based research activity began in earnest following the development of sophisticated reconstruction algorithms and improvements in detector technology. By the mid-1980s, PET had become a tool for medical diagnosis and for dynamic studies of human metabolism. Today, because of its million-fold sensitivity advantage over magnetic resonance imaging (MRI) in tracer studies and its chemical specificity, PET is used to study neuroreceptors in the brain and other body tissues. In contrast, MRI has exquisite resolution for anatomic (Figure 14.4) and flow studies as well as unique attributes of evaluating chemical composition of tissue but in the millimolar range rather PET MRI FIGURE 14.4 The MRI image shows the arteriovenous malformation (AVM) as an area of signal loss due to blood flow. The PET image shows the AVM as a region devoid of glucose metabolism and also shows decreased metabo-lism in the adjacent frontal cortex. This is a metabolic effect of the AVM on the brain and may explain some of the patient’s symptoms.
eBook - ePub- Aaron Newman(Author)
- 2019(Publication Date)
- SAGE Publications Ltd(Publisher)
Although PET has some significant limitations relative to fMRI – including much lower temporal resolution, moderately lower spatial resolution, and the need to use radioactivity – it has some advantages as well. These include the ability to image neuromodulator concentrations and disease markers, as well as the fact that there is no magnetic field or RF energy that, in MRI, precludes scanning people with some implanted devices such as cochlear implants. An exciting recent technical advance is scanners that combine PET and MRI in a single unit. These open up possibilities of simultaneous multimodal neuroimaging that could provide greater insight into functional brain activation, as well as enhanced understanding of the physiological processes underlying the fMRI BOLD response.Things You Should Know- The PET signal is created by radioactive decay of atoms that are unstable due to having one more proton than neutrons. Such atoms stabilize by converting one proton to a neutron, emitting a positron in the process. Positrons travel a short distance before encountering an electron and being annihilated, resulting in the formation of a pair of photons which travel in opposite directions at the speed of light.
- PET Scanners detect and localize these positrons through scintillation detectors tuned to the photons emitted by positron annihilation. PET Scanners consist of a number of detector rings; the number of these determines the number of slices the PET image can contain. Coincidence detectors are used to identify pairs of photons that arrive simultaneously at two detectors along a line of response passing through the tissue. Since the origin of the photon could be anywhere along that line of response, PET data must be reconstructed through back-projection. This involves computing, for each location in the image volume, the number of detections occurring along lines of response passing through that location. This can be done exclusively within each detector ring, for 2D imaging, or across rings for 3D imaging.
- The radioactive substances introduced into the body for PET imaging are called positron-emitting radioligands (PERs). These generally involve a chemically unstable atom bound to a molecule of physiological interest, such as oxygen or glucose. PERs have a short half-life and therefore must be synthesized in a cyclotron shortly before use. Common PERs for functional imaging include oxygen (15 O, for measuring cerebral blow flow or oxygen metabolism) and fluorodeoxyglucose (18 FDG, for measuring glucose metabolism). As well, a number of PERs are used to trace specific neuromodulator systems, including 18
eBook - PDFEarly Breast Cancer
From Screening to Multidisciplinary Management, Third Edition
- John R Benson, Gerald P.H. Gui, Todd Tuttle, John R Benson, Gerald P.H. Gui, Todd Tuttle(Authors)
- 2013(Publication Date)
- CRC Press(Publisher)
195 21 PET Scanning and breast cancer management Rebecca Wight and Patrick Borgen introduction Positron emission tomography with 18 F-fluorodeoxyglucose (FDG-PET) has become a widely accepted imaging tool in oncology. Although this technology is not routinely used in breast cancer management, there is a large body of research examining its utility in breast cancer screening, diagnosis, pre-operative evaluation, and monitoring of recurrence and response to chemotherapy (1–4). The advantage of FDG-PET over conventional imaging modalities, such as mammography, ultrasonography, computer tomography (CT), and magnetic resonance imaging (MRI), is its ability to provide functional tumor information. The technology exploits the “Warburg effect” first described by Warburg et al. in the 1920s, in that tumor cells have a higher metabolic rate than normal tissue with higher glucose avidity and increased glucose utilization (5). The most commonly used radiotracer in PET technology, 18 F-fluorodeoxyglucose (FDG), is a glucose analog which is taken up by cells following the same initial metabolic pathway as glucose. After phosphorylation, given the lack of an oxygen atom at its C-2 position, the tracer molecule is unable to undergo further catabolism, thereby allowing accumulation of FDG within the cell. A subsequent decay of radioisotope occurs, during which positrons travel approximately 1 mm and collide with electrons in an annihilation reaction which produces two high-energy photons. These photons are emitted in opposite directions and can be detected during the whole-body scanning process as 3-D images representing the distri-bution of the radiotracer (6,7). Images also denote the intensity of FDG uptake and are reported as a standardized uptake value (SUV) representing metabolic data corresponding to both local and regional disease. Combining this process with CT (Fig. 21.1) allows correlation with anatomical data and increased accuracy of tumor detection.
eBook - PDF- Philip Palin Dendy, Brian Heaton(Authors)
- 2011(Publication Date)
- CRC Press(Publisher)
Many of the challenges of the use of positron emitters remain. The application of the methodology is inextricably linked to the production and availability of well-characterised radiopharmaceuticals targeted to specific biochemical pathways and processes. Such tracers are important for diagnosis and disease staging but more importantly there is a 11.13 Current and Future Developments of PET and PET/CT ............................................ 393 11.14 Conclusion ........................................................................................................................ 395 References ..................................................................................................................................... 395 Further Reading .......................................................................................................................... 396 Exercises ...................................................................................................................................... 396 Positron Emission Tomographic Imaging (PET) 377 growing demand to be able to measure response to therapeutic interventions. This lat-ter application is renewing the drive to discover and characterise ‘biomarkers’ which are uniquely sensitive to changes in disease state following treatment. Enhancements of the detector and image reconstruction technology still occur with continued developments in sensitivity, resolution and quantitative accuracy. These are combined with the exploration of other multimodality combinations such as PET and magnetic resonance (PET/MR) both in humans and high resolution animal systems. This chapter provides an introduction to the principles behind PET imaging and the cur-rent developments and applications.
eBook - PDFRadioisotopes
Applications in Bio-Medical Science
- Nirmal Singh(Author)
- 2011(Publication Date)
- IntechOpen(Publisher)
This new guideline prompted the pharmaceutical industry to identify and quantify drug metabolites in humans in the early phases of drug development. In microdose studies PK data are obtained after administration of a trace subpharmacologic quantity to human subjects (Lappin et al., 2006). The ultrasensitive analytic technique of accelerator mass spectrometry (AMS) has been used to quantify the low plasma concentrations anticipated after microdose administration. These studies do not provide information about the safety and tolerability of the drug. Requirements for microdose studies have been summarized by the EMEA, FDA and others (EMEA, 2003; FDA, 2006; Bergstrom et al., 2003; Marchetti et al., 2007). 3. PET imaging 3.1 Principles of PET PET is a nuclear imaging technique used to map biological and physiological processes in living subjects following the administration of positron emitting radiopharmaceuticals. The technique is based on the detection of photons released by annihilation of positrons emitted by radioisotopes. Positron-emitting radionuclides are produced in a cyclotron by bombarding target material with accelerated protons. In the body, these radionuclides emit positrons that undergo annihilation with nearby electrons, resulting in the release of two photons. These so-called annihilation photons are detected by imaging and the resulting data can be used to reveal the distribution of the radiotracer in the body. Unlike conventional imaging modalities, such as magnetic resonance imaging (MRI) or computed tomography (CT), which mainly provide detailed anatomical images, PET can measure biochemical and physiological aberrations that occur prior to macroscopic anatomical signs of a disease, such as cancer (Chen et al., 2011). Currently, many positron emitting isotopes are available with different characteristics (see Table 1).
eBook - PDFPositron Emission Tomography
Recent Developments in Instrumentation, Research and Clinical Oncological Practice
- Sandro Misciagna(Author)
- 2013(Publication Date)
- IntechOpen(Publisher)
Indian J. Radiol. Imaging. 19(2): 94–98, 2010. Positron Emission Tomography-Computed Tomography Data Acquisition and Image Management http://dx.doi.org/10.5772/57119 61 Chapter 3 Basic PET Data Analysis Techniques Karmen K. Yoder Additional information is available at the end of the chapter http://dx.doi.org/10.5772/57126 1. Introduction 1.1. Purpose of chapter In many neuroscience-based PET research labs, procedures for data analyses are developed in-house and passed along as students, staff and post-doctoral fellows transition through training cycles. Although image processing and data analysis techniques are quite similar across many groups, there has not been any formal information available to the general scientific public. This becomes problematic from an instructional standpoint, as the increas‐ ingly cross-disciplinary nature of neuroimaging attracts researchers with vastly diverse backgrounds. It is not uncommon to find behavioral pharmacologists, bench neuroscientists, neuropsychologists, and neuroradiologists interested in using neuroimaging techniques for their research. However, often these individuals cannot pursue formal training in PET because of time constraints from other job demands. Although it is easy for seasoned PET researchers to quickly train someone in a laboratory-codified stream of image processing, the “why” of the steps may not get communicated sufficiently, which is a clear disservice to the trainees. This chapter was designed to remedy this problem. The intent of this chapter is to provide a broad foundation of the concepts behind basic PET image processing and data analyses, using data and images from several neuroligands to illustrate key points. The reader is expected to have a basic working understanding of positron emission, gamma ray generation, and photon detection by the PET Scanner. 1.2. Importance of study planning First and foremost, the scientific question at hand should drive the research process.
eBook - PDF- Victor H. Gerbaudo(Author)
- 2012(Publication Date)
- Cambridge University Press(Publisher)
Carbon-11 acetate positron emission tomography can detect local recurrence of prostate cancer Eur J Nucl Med Mol Imaging 2002;29:1380–4. 168. Seppälä J, Seppänen M, Arponen E, Lindholm P, Minn H. Carbon-11 acetate PET/CT based dose escalated IMRT in prostate cancer. Radiother Oncol 2009;93:234–40. 169. Ponde DE, Dence CS, Oyama N et al. 18F-fluoroacetate: a potential acetate analog for prostate tumor imaging – in vivo evaluation of 18F-fluoroacetate versus 11C-acetate. J Nucl Med 2007;48:420–8. Chapter 2: PET probes for oncology 33 Part I Chapter 3 General concepts of PET and PET/CT imaging PET/CT information systems Jon M. Hainer While radiology was founded when X-rays spoiled a piece of photographic film, modern medical imaging has evolved to become primarily electronic. Computers, electromagnetic storage systems, and information networks are rapidly replacing photo- graphic film as the means of viewing, storing, and distributing radiologic images. As with any media, however, these electronic systems have idiosyncrasies that can lead to misinterpretation and error. It is therefore vital for radiologists to understand the foun- dations of the electronic media, so as to be able to recognize these pitfalls and, to the extent possible, adjust for them. Using some interesting images as starting points, we will discuss how modern systems store and display two- dimensional (2-D) and three-dimensional (3-D) images, as well as describe the additional text data necessary to provide the proper context for the imaging. Two-dimensional radiologic imaging In Figure 3.1, we have four identical images. Well, at least the images are identical in terms of how they are stored on a computer. On the screen, they are clearly very different. While the basic structures of the images generally appear similar, color and intensity have been varied to emphasize different aspects of the images.
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