SPECT Scan | Summary

Purpose:
SPECT (Single photon emission computed tomography) is a noninvasive diagnostic technique for many heart problems or diseases. By this test we can determine if the patient have a high risk for heart attack.
In contrast to CT or MRI witch gives us only anatomical image, SPECT in addition gives to the doctor the function of the organ.
It is used also to determine rate and volume of blood flow, size and location of blockage or narrowing coronary blood vessels.
SPECT is very good for heart disease in women, because the other tests are not accurate enough (particularly in women who have big breast). It is also used to finding tumors in beast and other organs like the brain.

Description of instrument:
Gamma cameras- there are two types rotating, few detectors that rotating around the patient, or circular, that do not rotate but it has lot of detectors in all the angles.
Each detector is connected to photomultiplier tubes that convert every photon to light that converted to electrical signal. The signal process in a computer know from witch angle this photon came, the computer get many signals so it can calculate the location of the tracer in that two dimensional slice. Then the table is moved to get another slice, so the computer from all the slices can get a there dimensional image.
Radiopharmaceuticals or tracers- they are proteins or organic molecules that attached to a radionuclide mostly thalium-201 or technetium-99m. Usually the radionuclide has a short half live, so it must be deliver routinely.
Chemical stress test- the test is done first when the heart is relax, and secondly after exercise, some people can not do it safely, like people who have pacemaker, so they get drugs that make the heart react as it was exercising. The names are persantine, dobutamine, adenosine.

Scientific principle:
Radioactivity- the radionuclide is decaying and emitting a photon.
Tracer- the radio tracer is bonded to a molecules or proteins that used mostly by the organ that we want to check, like the heart muscles. And staying there emitting the photons.
Places that have high level of tracer the picture will be bright(hot spot) and vise versa to the dark spots. By this the doctor can tell if it is normal or not.

Operation:
You should not eat or drink 12 hours before the exam.
The tracer is injected to the blood.
Waiting few minutes until it gets to the organ we check (brain, heart).
The patient lies in the bed and the gamma camera start to absorb the photon and after awhile we get the image of the organ.
Usually the will be to tests one in rest and another one after running in a treadmill for few minutes.
The test will take 15-30 minutes.
After the exam the patient can go back to normal activity.
The dose amount is a few mCi.

Safety features:
The tracer is going out from the body after 48 hours.
The dose amount is very low.
Pregnant or breast-feeding women must council their doctor before the test.
Breast-feeding women should not feed her baby for 36 hours after the examination.
The patient has to drink a lot after the exam so the radionuclide will go by the urine outside the body.



Web sites
http://www.asnc.org/patientinfo/information.cfm
http://www.heartcenteronline.com/
http://www.howstuffworks.com/
http://www.brighamandwomens.org/nuclearmedicine/patient/myocardial.asp