Assessor name: Michael Hickey
In this assignment, I will be comparing the desirable biological propertes and biological propertes of
radionuclides used for imaging. I will also be evaluatng the choice of radiopharmaceutcals for a
range of clinical imaging requirements
RADIONUCLIDES USED FOR IMAGING
A radioisotope used for diagnosis must emit gamma rays of sufcient energy to escape from the
body and it must have a half-life short enough for it to decay away soon afer imaging is completed.
There are also several other factors that need to be taken into consideraton before the radionuclide
can be used for this process. Radionuclides for radiopharmaceutcals must have certain propertes
such as;
Emit only gamma rays, since alpha and beta radiatons are readily absorbed in the body,
causing damage through ionisaton and difculty with detecton producing inaccurate
images).
Have a conveniently short half-life; short enough to avoid excessive radiaton damage, yet
long enough to allow detecton and produce an accurate image.
Emit gamma radiaton of an energy suitable for easy detecton by gamma camera.
Be easily atached to convenient biological compounds to transport it to the targeted
destnaton.
Reduced side efects on patents pregnant women and children).
Be readily and cheaply available, at high concentratons.
The other key factors that need to be considered before imaging is to take place are the biological
and radiological propertes.
Biological and Radiological Propertee
Technetum-99m is a widely used radioactve tracer which can be used to identfy blocked blood
vessels. Tc-99 is not widely used in radiopharmaceutcal processes just because of its very efcient
half-life but also because of its compatbility with biological compounds in the body. A
radiopharmaceutcal is formed by ataching a radioisotope to normal molecules found in the body,
known as radioactve labelling. The radiaton emited from the radiopharmaceutcal is detected by a
special camera called a gamma camera. A radiopharmaceutcal is given to a patent in a dose which
is just enough to obtain the informaton required. The actual amount of radiaton received by the
patent is very small.
Technetum-99m is a widely used radioactve tracer isotope in Nuclear Medicine. Its gamma ray
energy of about 140 keV is convenient for detecton. The fact that both its physical half-life and
its life are very short leads to very fast clearing from the body afer an imaging process. A further
advantage is that the gamma is a single energy, meaning it does not produce other radiaton beta
radiaton) allowing more precise alignment of imaging detectors.
Half-lives in days
Isotope
TPhysical TBiological TEfectve
Tc-99m 0.25 1 0.20
The technetum isotope Tc-99m is unusual in that it has a half-life for gamma emission of 6 hours.
This is extremely long for an electromagnetc decay - more typical is 10-16 seconds. With such a long