Thallium

Peggy, it is not a recognised trigger for GBS/CIDP anymore than any other ‘chemicals’ none of which show any evidence whatsoever.

Radionuclide tests (including thallium scans)

Radionuclide tests are less common than electrocardiograms or echocardiography.

What happens?
A doctor will inject a small amount of radioactive substance (isotope) into the blood, often while you are exercising on an exercise bike or treadmill (a running machine). You may also be given an injection of a drug to increase the blood flow to your heart. (This is particularly useful if you cannot do much exercise).
A large ‘camera’, positioned close to the chest, picks up the gamma rays sent out by the isotope. Depending on what sort of isotope is used, the camera can take pictures either of the inside of the heart as it empties and fills, or of the flow of blood to the muscular walls of the heart.
The isotope breaks down quickly, so you get only a small dose of radioactivity. Different isotopes are used for different tests. These include technetium, tetrofosmin, technetium MIBI, and thallium.
What can the test tell?
Doctors use different isotopes to assess different aspects of how your heart works. Radionuclide tests allow doctors to accurately assess the blood flow to the heart muscle. They give more detailed information than the exercise ECG test. They can also give information about the strength of the heart muscle. Radionuclide tests are very accurate and can help confirm whether you have coronary heart disease or not.
Radionuclide tests are safe and can give a lot of information about your heart, but only a few hospitals in the UK have the equipment and skilled staff to carry them out.
DocDavid