World Library  
Flag as Inappropriate
Email this Article

Brain positron emission tomography

Article Id: WHEBN0032443411
Reproduction Date:

Title: Brain positron emission tomography  
Author: World Heritage Encyclopedia
Language: English
Subject: Magnetic resonance imaging of the brain, Computed tomography of the head, Medical imaging, Echoencephalography, Magnetic resonance neurography
Collection: 3D Nuclear Medical Imaging, Neuroimaging
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Brain positron emission tomography

Brain positron emission tomography
Diagnostics
PET scan of a normal brain
ICD-10-PCS C030

Positron emission tomography (PET) measures emissions from radioactively labeled metabolically active chemicals that have been injected into the bloodstream. The emission data are computer-processed to produce multi-dimensional images of the distribution of the chemicals throughout the brain.[1]

Contents

  • Process 1
  • Advantages and disadvantages 2
  • Uses 3
  • References 4

Process

The positron emitting radioisotopes used are usually produced by a cyclotron, and chemicals are labeled with these radioactive atoms. The labeled compound, called a radiotracer, is injected into the bloodstream and eventually makes its way to the brain through blood circulation. Detectors in the PET scanner detect the radioactivity as the compound charges in various regions of the brain. A computer uses the data gathered by the detectors to create multi-dimensional (normally 3-dimensional volumetric or 4-dimensional time-varying) images that show the distribution of the radiotracer in the brain. Especially useful are a wide array of ligands used to map different aspects of neurotransmitter activity, with by far the most commonly used PET tracer being a labeled form of glucose (see Fludeoxyglucose (18F) (FDG)).

Advantages and disadvantages

The greatest benefit of PET scanning is that different compounds can show blood flow and oxygen and glucose metabolism in the tissues of the working brain. These measurements reflect the amount of brain activity in the various regions of the brain and allow to learn more about how the brain works. PET scans were superior to all other metabolic imaging methods in terms of resolution and speed of completion (as little as 30 seconds), when they first became available. The improved resolution permitted better study to be made as to the area of the brain activated by a particular task. The biggest drawback of PET scanning is that because the radioactivity decays rapidly, it is limited to monitoring short tasks.[2]

Uses

PET brain scans show chemical differences in the brain between addicts and non-addicts. The normal images in the bottom row come from non-addicts; the abnormal images in the top row come from patients with addiction disorders. These PET brain scans show that that addicts have fewer than average dopamine receptors in their brains, so that weaker dopamine signals are sent between cells.

Before the use of Functional magnetic resonance imaging became widespread, PET scanning was the preferred method of functional (as opposed to structural) brain imaging, and it still continues to make large contributions to neuroscience. PET scanning is also useful in PET-guided stereotactic surgery and radiosurgery for treatment of intracranial tumors, arteriovenous malformations and other surgically treatable conditions.[3]

PET scanning is also used for diagnosis of brain disease, most notably because brain tumors, strokes, and neuron-damaging diseases which cause dementia (such as Alzheimer's disease) all cause great changes in brain metabolism, which in turn causes easily detectable changes in PET scans. PET is probably most useful in early cases of certain dementias (with classic examples being Alzheimer's disease and Pick's disease) where the early damage is too diffuse and makes too little difference in brain volume and gross structure to change CT and standard MRI images enough to be able to reliably differentiate it from the "normal" range of cortical atrophy which occurs with aging (in many but not all) persons, and which does not cause clinical dementia.

References

  1. ^ Lars-Goran Nilsson and Hans J. Markowitsch (1999). Cognitive Neuroscience of Memory. Seattle: Hogrefe & Huber Publishers., page 57
  2. ^ Lars-Goran Nilsson and Hans J. Markowitsch (1999). Cognitive Neuroscience of Memory. Seattle: Hogrefe & Huber Publishers., pg. 60
  3. ^ Levivier M, Massager N, Wikler D, Lorenzoni J, Ruiz S, Devriendt D, David P, Desmedt F, Simon S, Van Houtte P, Brotchi J, Goldman S (July 2004). "Use of stereotactic PET images in dosimetry planning of radiosurgery for brain tumors: clinical experience and proposed classification". Journal of Nuclear Medicine 45 (7): 1146–1154.  
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.