Hello there
The short answer to the first part of your question regarding
(Technetium 99m) Tc99m compounds is that they give a sharper picture
than do other medically used radioisotopes. It has a higher photon
flux resulting in these clearer images. Tc99m compounds can also
provide answers to many diagnostic questions from widely differing
indications.
Tc99m compounds also have a fairly short half life (about 6 hours) and
present less of a risk to the patient for radiation damage than do
isotopes with longer half lives.
It is obtained as the decay product of Molybdenum 99, 99Mo(T1/2-67
hours). This is created in the hospitals from a Mo99-Tc99m generator
system while 99Mo itself is obtained from fission of uranium 235 in
research reactors.
There is also the matter of convenience. While most medical isotopes
must be prepared in a central laboratory, Tc99 compounds can be
prepared in the hospital where they are used.
In fact, once again because of their short half life, they need to be
prepared where used. This is carried out in specially equipped
laboratories in the hospitals which are called hospital
radiopharmacies.
Tc99m in the form of sodium pertechnetate is obtained by eluting a
sterile Mo99-Tc99m generator with a sterile sodium chloride solution.
The other Tc99m radiopharmaceuticals required for different organ
studies are obtained by adding to corresponding sterile “kits”
containing the active ingredients.
This combination of clearer images, safety, convenience and
versatility, go a long way to establishing Tc99m compounds as being
among the favorites of nuclear medicine.
There are undoubtedly many layers of additional reasonings, mostly
technical in nature, behind their popularity. But what I have covered
encompasses the main reasons.
With the increase in image clarity provided by Tc99m isotopes, the
camera used must have the ability to record these images at a higher
resolution and of course the three main advantages of the gamma camera
are:
1 - High sensitivity
2 - A broad static field of view
3 - High spatial resolution.
These features lead to advantages such as rapid changes in the isotope
distribution can be measured and diagnostic time shortened. In
addition, improvements in the positioning circuit have achieved even
higher resolutions making gamma cameras more popular than ever in
medical diagnosis.
This article, which is in PDF format requiring Acrobat Reader, will
give you an even broader overview of the gamma camera:
http://usa.hamamatsu.com/cmp-detectors/pmts/handbook/92gammacameras.pdf
You may also fine this article interesting:
http://www.ansto.gov.au/info/press/2003/p002.html - It is a press
release from ANSTO Communications in Australia and relates to the fact
that increased use of gamma cameras in emergency wards could prevent
thousands of needless hospital admissions.
Websites used for the above in addition to those listed in the text:
http://tinyurl.com/d87p - A commercial website from Bristol-Myers
Squibb Company
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfTopic/topicindex/topindx.cfm?alpha=g
- This website from the FDA has a couple of articles about the failure
of a particular type of gamma camera. You will also find many other
articles in both text and PDF formats.
http://www.iaea.or.at/programmes/ripc/iachem/areas_of_activities.htm -
Information from the Internation Atomic Energy Agency regarding
isotopes and medical isotopes
http://www.pathinfo.com/cgi-bin/lh.cgi?tx=technetium - This is a
membership website containing a list of Tc99m compounds and their
uses. 30 compounds are covered. When I accessed the site, I received
this notice: "NOTICE: Your free, non-member search was automatically
truncated at 30 information-packets. There are an additional 4 packets
available in this search. Members may obtain virtually unlimited
outputs." - - So as you can see, even without a membership, you can
find all but four of the compounds.
http://www.virtual.epm.br/material/tis/curr-med/med3/2002/ddi/matdid/cap2.htm
- The website is "Squires Fundamentals Radiology" Information about
Tc99m is found near the bottom of a very long page. Because of that,
I will go ahead and quote it here: "Technetium-99m (Tc99m) has proved
to be the most useful radioactive tracer; it is relatively
inexpensive, has a short but useful half-life, and is readily
available from portable generators. Tc99m is linked to various
physiological substances that will seek different organs.
Technetium-Tc99m-pertechnetate is trapped by the thyroid gland and can
be used for thyroid imaging. Two other examples of other useful Tc99m
compounds are Tc99m- macroaggregated albumin (which is trapped in
pulmonary capillaries) for lung scanning (Figure 2.42) and Tc-99m
-methylene diphosphonate for bone scanning (Figure 2.43"
The figure references are found at the website.
Search - Google
Terms - Tc99m, Tc99m history of use, gamma camera/s, gamma camera
history of use, radiology, nuclear medicine
If I may clarify anything, please ask before rating the answer.
Cheers
digsalot |
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