Positron emission tomography (PET)

Definition

Positron emission tomography (PET) is a non-invasive scanning technique that utilizes small amounts of radioactive positrons (positively charged particles) to visualize body function and metabolism .

Purpose

As of 2001, PET is the fastest growing nuclear medicine tool in terms of increasing acceptance and applications. It is useful in the diagnosis, staging, and treatment of cancer because it provides information that cannot be obtained by other techniques like computed tomography (CT) and magnetic resonance imaging (MRI).

PET scans can be performed at medical centers equipped with a small cyclotron. Smaller cyclotrons and increasing availability of certain radiopharmaceuticals are making PET a more widely used imaging modality.

Physicians first used PET to obtain information about brain function and to study brain activity in various neurological diseases and disorders, including stroke, epilepsy, Alzheimer's disease , Parkinson's disease , and Huntington's disease; and in such psychiatric disorders as schizophrenia , depression, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, and Tourette syndrome. More and more, PET is being used to evaluate patients for head and neck, lymphoma, melanoma, lung, colorectal, and esophageal cancers. PET also is used to evaluate heart muscle function in patients with coronary artery disease or cardiomyopathy.

Precautions

There is always a slight risk when radioactive material is injected into the body. However, because the radioactive tracers used are short-lived and clear the body quickly, they are considered safe. The radiation dose received is only slightly more than that received in a chest x ray . Still, pregnant women should not have a PET scan.

Description

PET involves injecting a patient with a radiopharmaceutical similar to glucose. An hour after injection of this tracer, a PET scanner images a specific metabolic function by measuring the concentration and distribution of the tracer throughout the body.

When it enters the body, the tracer courses through the bloodstream to the target organ, where it emits positrons. The positively charged positrons collide with negatively charged electrons and gamma rays are produced. The gamma rays are detected by photomultiplier scintillator combinations positioned on opposite sides of the patient. These signals are then processed by the computer and images are generated.

PET provides an advantage over CT and MRI because it can determine if a lesion is malignant. The two other modalities provide images of anatomical structures but often cannot provide a determination of malignancy. Recently, PET has been used in combination with CT and MRI to identify abnormalities with more precision and indicate areas of most active metabolism. This additional information allows for more accurate evaluation of cancer treatment and management.

Health care team roles

Personnel for a PET facility should include a physicist for technical support, calibration, and software; a physician for medical interventions and reading; and administrative staff for scheduling, paperwork, and billing. A trained technologist performs the PET scans. A positron emission tomography technologist performs PET procedures on clinical and research subjects referred for neurologic, oncologic, cardiac, or other conditions. The technologist also ensures appropriate patient care, acquires data, and performs analysis according to protocols. A technologist needs training in nuclear medicine. State licensure is required as a nuclear medicine technologist.

KEY TERMS

Electron —One of the small particles that make up an atom. An electron has the same mass and amount of charge as a positron, but the electron has a negative charge.

Gamma ray —A high-energy photon emitted by radioactive substances.

Half-life —The time required for half of the atoms in a radioactive substance to disintegrate.

Photon —A light particle.

Positron —One of the small particles that make up an atom. A positron has the same mass and amount of charge as an electron, but the positron has a positive charge.

Resources

BOOKS

Bares, R., and G. Lucignani. Clinical PET. Kluwer Academic Publishers, 1996.

Gulyas, Balazs, and Hans W. Muller-Gartner. Positron Emission Tomography: A Critical Assessment of Recent Trends. Kluwer Academic Publishers, 1996.

Kevles, Bettyann Holtzmann. Medical Imaging in the Twentieth Century. Rutgers University Press, 1996.

PERIODICALS

"Brain Imaging and Psychiatry: Part 1." Harvard Mental Health Letter 13 (Jan. 1997): 1.

"Brain Imaging and Psychiatry: Part 2." Harvard Mental Health Letter 13 (Feb. 1997): 1.

Faust, Rita Baron. "Life-Saving Breakthroughs: Innovative Designs and Techniques for Treating Heart Disease." American Health for Women 16 (Sept. 1997): 65.

Powledge, Tabatha M. "Unlocking the Secrets of the Brain: Part 2." BioScience 47 (17 July 1997): 403.

"Studies Argue for Wider Use of PET for Cancer Patients." Cancer Weekly Plus (15 Dec. 1997): 9.

OTHER

Barnes, Eric. "HCFA Broadens Medicare Coverage for PET." Radiology News 18 Dec. 2000. <http://www.auntminnie.com>.

Di Carli, M. F. "Positron Emission Tomography (PET)." 1st Virtual Congress of Cardiology 4 Oct. 1999. <http://www.fac.org>.

Madden Yee, Kate. "Start-up Enters Breast Imaging Arena with Scintimammography, PET Offerings." Radiology News 14 Mar. 2001. <http://www.auntminnie.com>.

"Nycomed Amersham and the Medical Research Council: Major Collaboration in World Leading Imaging Technology." Medical Research Center. 2001. <http://www.mrc.ac.uk/whats_new/press_releases/PR_2001/mrc_02_01.html>.

Dan Harvey

Positron Emission Tomography (PET)

Definition

Positron emission tomography (PET) is a non-invasive scanning technique that utilizes small amounts of radioactive positrons (positively charged particles) to visualize body function and metabolism.

Purpose

PET is the fastest growing nuclear medicine tool in terms of increasing acceptance and applications. It is useful in the diagnosis, staging, and treatment of cancer because it provides information that cannot be obtained by other techniques like computed tomography (CT) and magnetic resonance imaging (MRI).

PET scans can be performed at medical centers equipped with a small cyclotron. Smaller cyclotrons and increasing availability of certain radiopharmaceuticals are making PET a more widely used imaging modality.

Physicians first used PET to obtain information about brain function and to study brain activity in various neurological diseases and disorders, including stroke, epilepsy, Alzheimer's disease, Parkinson's disease, and Huntington's disease; and in psychiatric disorders such as schizophrenia, depression, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, and Tourette syndrome. More and more, PET is being used to evaluate patients for head and neck, lymphoma, melanoma, lung, colorectal, and esophageal cancers. PET also is used to evaluate heart muscle function in patients with coronary artery disease or cardiomyopathy.

Precautions

There is always a slight risk when radioactive material is injected into the body. However, because the radioactive tracers used are short-lived and clear the body quickly, they are considered safe. The radiation dose received is only slightly more than that received in a chest x ray. Still, pregnant women should not have a PET scan.

Description

PET involves injecting a patient with a radiopharmaceutical similar to glucose. An hour after injection of this tracer, a PET scanner images a specific metabolic function by measuring the concentration and distribution of the tracer throughout the body.

When it enters the body, the tracer courses through the bloodstream to the target organ, where it emits positrons. The positively charged positrons collide with negatively charged electrons and gamma rays are produced. The gamma rays are detected by photomultiplier-scintillator combinations positioned on opposite sides of the patient. These signals are then processed by the computer and images are generated.

PET provides an advantage over CT and MRI because it can determine if a lesion is malignant. The two other modalities provide images of anatomical structures but often cannot provide a determination of malignancy. Recently PET has been used in combination with CT and MRI to identify abnormalities with more precision and indicate areas of most active metabolism. This additional information allows for more accurate evaluation of cancer treatment and management.

Health care team roles

Personnel for a PET facility should include a physicist for technical support, calibration, and software; a physician for medical interventions and reading; and administrative staff for scheduling, paperwork, and billing. A trained technologist performs the PET scans. A positron emission tomography technologist performs PET procedures on clinical and research subjects referred for neurologic, oncologic, cardiac, or other conditions. The technologist also ensures appropriate patient care, acquires data, and performs analysis according to protocols. A technologist needs training in nuclear medicine. State licensure is required as a nuclear medicine technologist.

KEY TERMS

Electron— One of the small particles that make up an atom. An electron has the same mass and amount of charge as a positron, but the electron has a negative charge.

Gamma ray— A high-energy photon emitted by radioactive substances.

Half-life— The time required for half of the atoms in a radioactive substance to disintegrate.

Photon— A light particle.

Positron— One of the small particles that make up an atom. A positron has the same mass and amount of charge as an electron, but the positron has a positive charge.

Resources

BOOKS

Bares, R., and G. Lucignani. Clinical PET. Kluwer Academic Publishers, 1996.

Gulyas, Balazs, and Hans W. Muller-Gartner. Positron Emission Tomography: A Critical Assessment of Recent Trends. Kluwer Academic Publishers, 1996.

Kevles, Bettyann Holtzmann. Medical Imaging in the Twentieth Century. Rutgers University Press, 1996.

PERIODICALS

"Brain Imaging and Psychiatry: Part 1." Harvard Mental Health Letter 13 (Jan. 1997): 1.

"Brain Imaging and Psychiatry: Part 2." Harvard Mental Health Letter 13 (Feb. 1997): 1.

Faust, Rita Baron. "Life-Saving Breakthroughs: Innovative Designs and Techniques for Treating Heart Disease." American Health for Women 16 (Sept. 1997): 65.

Powledge, Tabatha M. "Unlocking the Secrets of the Brain: Part 2." BioScience 47 (17 July 1997): 403.

"Studies Argue for Wider Use of PET for Cancer Patients." Cancer Weekly Plus (15 Dec. 1997): 9.

OTHER

Barnes, Eric. "HCFA Broadens Medicare Coverage for PET." Radiology News 18 Dec. 2000. 〈http://www.auntminnie.com〉.

Di Carli, M. F. "Positron Emission Tomography (PET)." 1st Virtual Congress of Cardiology 4 Oct. 1999. 〈http://www.fac.org〉.

Madden Yee, Kate. "Start-up Enters Breast Imaging Arena with Scintimammography, PET Offerings." Radiology News 14 Mar. 2001. 〈http://www.auntminnie.com〉.

"Nycomed Amersham and the Medical Research Council: Major Collaboration in World Leading Imaging Technology." Medical Research Center. 2001. 〈http://www.mrc.ac.uk/whats_new/press_releases/PR_2001/mrc_02_01.html〉.

Positron Emission Tomography (PET)

Definition
Purpose
Description

Definition

Positron emission tomography (PET) is a noninvasive scanning technique that utilizes small amounts of radioactive positrons (positively charged particles) to visualize body function and metabolism.

Purpose

PET is the fastest growing nuclear medicine tool in terms of increasing acceptance and applications. It is useful in the diagnosis, staging, and treatment of cancer because it provides information that cannot be obtained by other techniques such as computed tomography (CT) and magnetic resonance imaging (MRI).

PET scans are performed at medical centers equipped with a small cyclotron. Smaller cyclotrons and increasing availability of certain radiopharmaceuticals are making PET a more widely used imaging modality.

Physicians first used PET to obtain information about brain function, and to study brain activity in various neurological diseases and disorders including stroke, epilepsy, Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease; and in psychiatric disorders such as schizophrenia, depression, obsessive-compulsive disorder, attention deficit hyperactivity disorder (ADHD), and Tourette syndrome. PET is now used to evaluate patients for these cancers: head and neck, lymphoma, melanoma, lung, colorectal, breast, and esophageal. PET also is used to evaluate heart muscle function in patients with coronary artery disease or cardiomyopathy.

Description

PET involves injecting a patient with a radiopharmaceutical similar to glucose. An hour after injection of this tracer, a PET scanner images a specific metabolic function by measuring the concentration and distribution of the tracer throughout the body.

When it enters the body, the tracer courses through the bloodstream to the target organ, where it emits positrons. The positively charged positrons collide with negatively charged electrons, producing gamma rays. The gamma rays are detected by photomultiplier-scintillator combinations positioned on opposite sides of the patient. These signals are processed by the computer and images are generated.

KEY TERMS

Electron— One of the small particles that make up an atom. An electron has the same mass and amount of charge as a positron, but the electron has a negative charge.

Gamma ray— A high-energy photon emitted by radioactive substances.

Half-life— The time required for half of the atoms in a radioactive substance to disintegrate.

Photon— A light particle.

Positron— One of the small particles that make up an atom. A positron has the same mass and amount of charge as an electron, but the positron has a positive charge.

PET provides an advantage over CT and MRI because it can determine if a lesion is malignant. The two other modalities provide images of anatomical structures, but often cannot provide a determination of malignancy. CT and MRI show structure, while PET shows function. PET has been used in combination with CT and MRI to identify abnormalities with more precision and indicate areas of most active metabolism. This additional information allows for more accurate evaluation of cancer treatment and management.

Resources

BOOKS

Bares, R., and G. Lucignani. Clinical PET. Kluwer Academic Publishers, 1996.

Gulyas, Balazs, and Hans Muller-Gartner. Positron Emission Tomography: A Critical Assessment of Recent Trends. Kluwer Academic Publishers, 1996.

Kevles, Bettyann Holtzmann. Medical Imaging in the Twentieth Century. Rutgers University Press 1996.

PERIODICALS

“Brain Imaging and Psychiatry: Part 1.” Harvard Mental Health Letter 13 (Jan. 1997): 1.

“Brain Imaging and Psychiatry: Part 2.” Harvard Mental Health Letter 13 (February 1997): 1403.

Goerres, G. “Position Emission Tomography and PET CT of the Head and Neck: FDG Uptake in Normal Anatomy, in Benign Lesions, and Changes Resulting from Treatment.” American Journal of Roentgenology (November 2002): 1337.

Kostakoglu, L. “Clinical Role of FDG PET in Evaluation of Cancer Patients.” Radiographics (March-April 2003): 315

Shreve, P. “Pitfalls in Oncologic Diagnosis with FDG PET Imaging: Physiologic and Benign Variants.” Radio-graphics 62 (January/February 1999).

“Studies Argue for Wider Use of PET for Cancer Patients.” Cancer Weekly Plus 15 (December 1997): 9.

OTHER

Di Carli, M. F. “Positron Emission Tomography (PET).” 1st Virtual Congress of Cardiology. October 4, 1999. http://www.fac.org.

Madden Yee, Kate. “Start-up Enters Breast Imaging Arena with Scintimammography, PET Offerings.” Radiology News. March 14, 2001. http://www.auntminnie.com.

“Nycomed Amersham and the Medical Research Council: Major Collaboration in World Leading Imaging Technology.” Medical Research Center 2001. http://www.mrc.ac.uk/whats_new/press_releases/PR_2001/mrc_02_01.html.

Dan Harvey

Lee A. Shratter, M.D.

Positron Emission Tomography (PET)

Description

Risks

Resources

Positron emission tomography (PET) is a nuclear medicine medical imaging (scanning) technique used in conjunction with small amounts of radiolabeled compounds to visualize brainanatomy and function.

PET was the first scanning method to provide information on brain function as well as anatomy.

This information includes data on blood flow, oxygen consumption, glucose metabolism, and concentrations of various molecules in brain tissue.

PET has been used to study brain activity in various neurological diseases and disorders, including stroke; epilepsy; Alzheimer disease, Parkinson disease, and Huntington disease; and in some psychiatric disorders, such as schizophrenia, depression, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, and Tourette syndrome. PET studies have helped to identify the brain mechanisms that operate in drug addiction, and to shed light on the mechanisms by which individual drugs work. PET is also proving to be more accurate than other methods in the diagnosis of many types of cancer. In the treatment of cancer, PET can be used to determine more quickly than conventional tests whether a given therapy is working. PET scans also give accurate and detailed information on heart disease, particularly in women, in whom breast tissue can interfere with other types of tests.

Description

A very small amount of a radiolabeled compound is inhaled by or injected into the patient. The injected or inhaled compound accumulates in the tissue to be studied. As the radioactive atoms in the compound decay, they release smaller particles called positrons, which are positively charged (the counterpart of an electron). When a positron collides with an electron (negatively charged), they are both annihilated, and two photons (light particles) are emitted. The photons

KEY TERMS

Electron— One of the small particles that make up an atom. An electron has the same mass and amount of charge as a positron, but the electron has a negative charge.

Gamma ray— Electromagnetic radiation originating from the nucleus of an atom.

Half-life— The time required for one-half of the atoms in a radioactive substance to disintegrate.

Photon— A particle of light.

Positron— One of the small particles that make up an atom. A positron has the same mass and amount of charge as an electron, but the positron has a positive charge.

move in opposite directions and are picked up by the detector ring of the PET scanner. A computer uses this information to generate three-dimensional, cross-sectional images that represent the biological activity where the radiolabeled compound has accumulated. They are often used in the medical fields of oncology, cardiology, neurology, neuropsychology, pharmacology, and psychiatry.

A related technique is called single photon emission computed tomography (CT) scan (SPECT). SPECT is similar to PET, but the compounds used contain heavier, longer-lived radioactive atoms that emit high-energy photons, called gamma rays, instead of positrons. SPECT is used for many of the same applications as PET, and is less expensive than PET, but the resulting picture is usually less sharp than a PET image and reveals less information about the brain.

Risks

Some of radioactive compounds used for PET or SPECT scanning can persist for a long time in the body. Even though only a small amount is injected each time, the long half-lives of these compounds can limit the number of times a patient can be scanned.

Resources

BOOKS

Dilsizian, Vasken, and Gerald M. Pohost, eds. Cardiac CT, PET, and MR. Malden, MA: Blackwell Futura, 2006.

Lin, Eugene. PET and PET/CT: A Clinical Guide. New York: Thieme Medical Publishers, 2005.

Wernick, Miles N., and John N. Aarsvold, eds. Emission Tomography: The Fundamentals of PET and SPECT. Amsterdam, Netherlands, and Boston, MA: Elsevier Academic Press, 2004.

Lisa Christenson

Positron emission tomography (PET)

Definition

Positron emission tomography (PET) is a noninvasive scanning technique that utilizes small amounts of radioactive positrons (positively charged particles) to visualize body function and metabolism.

Description

PET is the fastest growing nuclear medicine tool in terms of increasing acceptance and applications. It is useful in the diagnosis, staging, and treatment of cancer because it provides information that cannot be obtained by other techniques such as computed tomography (CT ) and magnetic resonance imaging (MRI) .

PET scans are performed at medical centers equipped with a small cyclotron. Smaller cyclotrons and increasing availability of certain radiopharmaceuticals are making PET a more widely used imaging modality.

Physicians first used PET to obtain information about brain function, and to study brain activity in various neurological diseases and disorders including stroke, epilepsy, Alzheimer's disease, Parkinson's disease , and Huntington's disease; and in psychiatric disorders such as schizophrenia, depression , obsessive-compulsive disorder, attention deficit hyperactivity disorder (ADHD), and Tourette syndrome . PET is now used to evaluate patients for these cancers: head and neck, lymphoma, melanoma, lung, colorectal, breast, and esophageal. PET also is used to evaluate heart muscle function in patients with coronary artery disease or cardiomyopathy.

Procedure

PET involves injecting a patient with a radiopharmaceutical similar to glucose. An hour after injection of this tracer, a PET scan creates an image of a specific metabolic function by measuring the concentration and distribution of the tracer throughout the body.

When it enters the body, the tracer courses through the bloodstream to the target organ, where it emits positrons. The positively charged positrons collide with negatively charged electrons, producing gamma rays. The gamma rays are detected by photomultiplier-scintillator combinations positioned on opposite sides of the patient. These signals are processed by the computer and images are generated.

PET provides an advantage over CT and MRI because it can determine if a lesion is malignant. The two other modalities provide images of anatomical structures, but often cannot provide a determination of malignancy. CT and MRI show structure, while PET shows function. PET has been used in combination with CT and MRI to identify abnormalities with more precision and indicate areas of most active metabolism. This additional information allows for more accurate evaluation of cancer treatment and management.

Resources

BOOKS

Bares, R., and G. Lucignani. Clinical PET. Kluwer Academic Publishers, 1996.

Gulyas, Balazs, and Hans Muller-Gartner. Positron Emission Tomography: A Critical Assessment of Recent Trends. Kluwer Academic Publishers, 1996.

Kevles, Bettyann Holtzmann. Medical Imaging in the Twentieth Century. Rutgers University Press, 1996.

PERIODICALS

"Brain Imaging and Psychiatry: Part 1." Harvard Mental Health Letter 13 (Jan. 1997): 1.

"Brain Imaging and Psychiatry: Part 2." Harvard Mental Health Letter 13 (February 1997): 1403.

Goerres, G. "Position Emission Tomography and PET CT of the Head and Neck: FDG Uptake in Normal Anatomy, in Benign Lesions, and Changes Resulting from Treatment." American Journal of Roentgenology (November 2002): 1337.

Kostakoglu, L. "Clinical Role of FDG PET in Evaluation of Cancer Patients." Radiographics (March-April 2003): 315.

Shreve, P. "Pitfalls in Oncologic Diagnosis with FDG PET Imaging: Physiologic and Benign Variants." Radiographics 62 (January/February 1999).

"Studies Argue for Wider Use of PET for Cancer Patients." Cancer Weekly Plus 15 (December 1997): 9.

OTHER

Di Carli, M. F. "Positron Emission Tomography (PET)." 1st Virtual Congress of Cardiology October 4, 1999. <http://www.fac.org>.

Madden Yee, Kate. "Start-up Enters Breast Imaging Arena with Scintimammography, PET Offerings." Radiology News March 14, 2001. <http://www.auntminnie.com>.

"Nycomed Amersham and the Medical Research Council: Major Collaboration in World Leading Imaging Technology." Medical Research Center 2001. <http://www.mrc.ac.uk/whats_new/press_releases/PR_2001/mrc_02_01.html>.

Dan Harvey

Lee A. Shratter, MD

Rosalyn Carson-DeWitt, MD