In conventional X-ray or CT examinations, the radiation comes out of a machine
and then passes through the patient's body. Nuclear medicine exams, however, use
the opposite approach: a radioactive material is introduced into the patient's
body (usually by injection), and is then detected by a machine called a gamma
You may be thinking "that sounds
Actually, the radioactive materials used have very short half-lives,
which means that they decay rapidly into a harmless material. Often, the
injected radioactive material is only inside the body for a very short time, and
the total dose of radiation is small -- similar, and sometimes even less than,
many other kinds of X-ray procedures. About twelve million nuclear medicine
exams are performed every year in the United States.
Why not just get a regular X-ray?
X-rays and nuclear medicine scans provide different information.
X-rays produce a structural image of an organ -- in other words, they tell us
what the organ looks like. On the other hand, nuclear scans image organ function.
That is, they can tell us what part of an organ is working properly, and what
part is not. For example, in one kind of nuclear scan called bone imaging, the
bone metabolism changes caused by trauma, infection or invasion by tumor may be
seen weeks or months before an abnormality is seen with X-rays.
Another example of imaging physiology is a new type of study available at
the Rochester Medical Center, Single Photon Emission Tomography, also known as a “SPECT”
scan. SPECT scans use a radiotracer to look for areas of increased metabolic
activity that is characteristic of viable tissue. While the tissue may look normal
on a CT scan or MRI, the SPECT scan may find changes in metabolic activity in the
tissue, suggesting it is not normal.
There is a wide range of exams performed in nuclear medicine. Please consult the
following sections for the individual details and how to prepare for an exam.