Hi rswchicago!
It appears that there are a number of procedures that use TC-99m as an
imaging agent, and each has specific protocol for patient preparation
and imaging. These uses include bone marrow imaging, leukocyte
imaging for the detection of osteomyelitis, and inflammatory bowel
disease, among others.
“Tc-99m is a metastable (i.e. 99 “m”) isotope that decays with a six
(6) hour half life yielding a single gamma ray at 140 KeV.”
( http://www.shroud.com/pdfs/accett2.pdf )
Because the half-life is only six hours, the imaging must be completed
before a reasonable amount of time or else too large of a portion of
the radioactive particles would be gone to take adequate images. This
maximum time constraint must be balanced with the minimum time
constraint described next:
The 2-3 hour period you described below is only applicable for
procedures in which blood is taken from the patient, the cells are
labeled with TC-99m, and are then re-injected into the body (there are
other applications). The waiting period is for the purpose of
allowing the labeled cells to disperse adequately such that an image
can be taken of the density and location of their distribution.
To further aid this distribution, the patient is supposed to drink
lots of water throughout the procedure. The reason the patient is
asked to urinate is twofold: a) so that the labeled cells can disperse
better through the urinary tract and be imaged better, and b) so that
the amount of radioactive material is more quickly disposed of from
the body, as it can have adverse effects like any radioactive
substance.
( http://www.md.chula.ac.th/radio/service/nucmed.php#bone )
I hope this has Answered your questions about this procedure. Please
do not hesitate to ask if you have any need for a clarification, and
please do if necessary before rating this Answer. Thank you!
Regards,
Andrewxmp |
