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Nuclear Medicine |
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Nuclear medicine
is a branch of medicine and medical imaging that uses the
nuclear properties of matter in diagnosis and therapy. More
specifically, nuclear medicine is a part of molecular imaging
because it produces images that reflect biological processes
that take place at the cellular and sub-cellular level. |
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Background
Nuclear medicine procedures use pharmaceuticals that have
been labeled with radionuclides (radiopharmaceuticals). In
diagnosis, radioactive substances are administered to
patients and the radiation emitted is detected. The
diagnostic tests involve the formation of an image using a
gamma camera or positron emission tomography, invented by
Hal O. Anger, and sometimes called an Anger gamma camera.
Imaging may also be referred to as radionuclide imaging or
nuclear scintigraphy. Other diagnostic tests use probes to
acquire measurements from parts of the body, or counters for
the measurement of samples taken from the patient.
In therapy, radionuclides are administered to treat disease
or provide palliative pain relief. For example,
administration of Iodine-131 is often used for the treatment
of thyrotoxicosis and thyroid cancer. Phosphorus-32 was
formerly used in treatment of polycythemia vera. Those
treatments rely on the killing of cells by high radiation
exposure, as compared to diagnostics in which the exposure
is kept as low as reasonably achievable (ALARA policy) so as
to reduce the chance of creating a cancer. |
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Nuclear
medicine imaging is unique, because it provides
doctors with information about both structure and
function. It is a way to gather medical information
that would otherwise be unavailable, require surgery,
or necessitate more expensive diagnostic tests. |
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Radiation dose |
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A
patient undergoing a nuclear medicine procedure will receive
a radiation dose. Under present international guidelines it
is assumed that any radiation dose, however small, presents
a risk. The radiation doses delivered to a patient |
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in a nuclear medicine investigation present a very small
risk of inducing cancer. In this respect it is similar
to the risk from X-ray investigations except that the
dose is delivered internally rather than from an
external source such as an X-ray machine. |
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Diagnostic testing |
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Diagnostic tests in nuclear medicine exploit the way that
the body handles substances differently when there is
disease or pathology present. The radionuclide introduced
into the body is often chemically bound to a complex that
acts |
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characteristically within the body; this is commonly known
as a tracer. In the presence of disease, a tracer will often
be distributed around the body and/or processed differently.
Many
tracer complexes have been developed in order to image or treat
many different organs, glands, and physiological processes.
The types of tests can be split into two
broad groups: in-vivo and in-vitro. |
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Nuclear
medicine specialists use safe, painless, and
cost-effective techniques to image the body and
treat disease. |
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Types of studies
A typical
nuclear medicine study involves administration of a radionuclide
into the body by intravenous injection in liquid or aggregate form,
ingestion while combined with food, inhalation as a gas or aerosol,
or rarely, injection of a radionuclide that has undergone
micro-encapsulation.
Some studies require the labeling of a
patient's own blood cells with a radionuclide (leukocyte scintigraphy and red blood cell scintigraphy).
Most diagnostic radionuclides emit gamma rays, while the cell-damaging properties of
beta particles are used in therapeutic applications. Refined
radionuclides for use in nuclear medicine are derived from fission
or fusion processes in nuclear reactors, which produce radioisotopes
with longer half-lives, or cyclotrons, which produce radioisotopes
with shorter half-lives, or take advantage of natural decay
processes in dedicated generators, i.e. molybdenum/technetium or
strontium/rubidium. |
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The
most commonly used intravenous radionuclides
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Technetium-99m (technetium-99m)
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Iodine-123 and 131
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Thallium-201
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Gallium-67
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Fluorine-18 Fluorodeoxyglucose
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Indium-111 Labeled Leukocytes
The most commonly used gaseous/aerosol radionuclides
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Xenon-133
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Krypton-81m
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Technetium-99m Technegas
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Technetium-99m DTPA |
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Data
Analysis |
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The
end result of the nuclear medicine imaging process is a
"dataset" comprising one or more images. In multi-image
datasets the array of images may represent a time
sequence (ie. cine) often called a "dynamic" dataset,
a cardiac |
gated time sequence, or a spatial
sequence where the gamma-camera is moved relative to the
patient. SPECT is the process by which images acquired from
a rotating gamma-camera are reconstructed to produce an
image of a "slice" through the patient at a particular
position. A collection of parallel slices form a
slice-stack, a three-dimensional representation of the
distribution of radionuclide in the patient.
The nuclear medicine computer may require millions of
lines of source code to provide quantitative analysis
packages for each of the specific imaging techniques
available in nuclear medicine. |
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What's
new
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Publication
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Manpower
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Images
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Links |
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Copyright © 2005,
www.cnmumym.org
All rights reserved
Centre For Nuclear Medicine and Ultrasound (CNMU), Post Box No-47,
Mymensingh-2200, Bangladesh
Site
design : Mizanur Rahman (AE), BAEC, e-mail:
mizan_ot@yahoo.com |
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