A full explanation of the details of using radioactive tracers in medicine. It's relevant to Unit 1 Module 1 SS1 and also will help you be sure you picked the right answer for the 2012 U1 P1 Q1.

1. CAPE UNIT 1 CHEMISTRY –
Radioactive Tracers In Medicine
Uses Of Radionuclides* In Medicine
How A Tracer Is Defined
Uses Of Radionuclides In Medicine
1. Diagnostic i.e. determining the problem.
2. Therapeutic i.e. treating the problem.
3. Power source (e.g. in cardiac pacemakers).
Radionuclides used in diagnostic
nuclear medicine are often called
radioactive tracers.
*A nuclide is a type of atom with definite numbers of protons
and neutrons in the nucleus A radionuclide is a nuclide
How Much Is Used
I di ti li ti t h i i lland neutrons in the nucleus. A radionuclide is a nuclide
exhibiting radioactivity.
In diagnostic applications, technicians use small
amounts of radionuclides whose progress through
the body or localization in
specific organs can be followed.
Larger quantities of radionuclides are used in
therapeutic applications.
Chemical Principles Behind Use
The fundamental chemical principle behind the
use of radionuclides in diagnostic medical work
is the fact that a radioactive nuclide of an
element has the same chemical properties as a
nonradioactive nuclide of the element. Thus,
body chemistry is not upset by the presence of a
small amount of a radioactive substance whose
nonradioactive form is already present in the
body.
Criteria For Selecting Diagnostic Radionuclides
(a) At low concentrations (to minimize radiation damage),
the radionuclide must be detectable by instrumentation
placed outside the body.y p y
(b) The radionuclide must have a short half life.
(c) The radionuclide must have a known mechanism for
elimination from the body.
(d) The chemical properties of the radionuclide must be
such that it is compatible with normal body chemistry.
Example Of Tracer Application In
Medicine
Location Of Impaired Circulation The Three Half Lives: TE, TB And TR
Material compiled by Denison at Global in Cunupia.
Interested students can call 693‐2909.
Location Of Impaired Circulation
Sodium‐24 is used to follow the circulation of
blood in the body. A small amount of this
radionuclide is injected into the blood stream in
the form of a sodium chloride solution. The
movement of the sodium‐24 through the
circulatory system is followed with radiation
The Three Half Lives: TE, TB And TR
The half life of a radionuclide T½ is the time taken for half
of the active nuclei to disintegrate, or alternatively the
time taken fro the activity to fall to half its original value.
When a radioactive isotope is taken into the body, it is
subject to various biological processes which will removecirculatory system is followed with radiation
detection equipment. If it takes longer than
normal for the radionuclide to show up at a
particular spot in the body, this is an indication
that the circulation is impaired at that spot.
THE HALF LIFE OF SODIUM‐24 IS 15.0 HOURS.
subject to various biological processes which will remove
it, such as urination, respiration and defecation. This
means that its effective half life, TE in the body is less
than the physical half life, TR from radioactive decay
alone. The biological half life, TB is defined as the time
taken for biological processes to remove half the original
active material. The effective half life is then given by the
equation:equation:
1/TE = 1/TB + 1/TR