What is difference between Thallium test and Angiography

A coronary angiogram is a procedure carried by the interventional cardiologist in the cardiac cath. lab, to exactly assess the extent of blocks present in the coronary arteries after which they can decide to go for angioplasty with or without stent, or to go for direct CABG operation etc.,.
A thallium test is also a method (noninvasive technique) to assess the extent of blocks by injecting the radioactive thallium subcutaneously & study the behaviour of the coronary arteries etc.,.

Begging to differ with the dear doctor, a Thallium exam does, in no way, tell one about any blockage or degree of blockage. A Thallium test, specifically a stress Thallium test, tells the physicians if the heart muscle is receiving enough blood from the coronary arteries or not.

From this point on it is only speculative whether or not a coronary artery is occluded & no way of knowing how much, degree wise, the occlusion is.

In an Angiogram, however, specific coronary artery & degree of blockage of that artery is quite clear.

Coronary angiography is a procedure that uses a special dye (contrast material) and x-rays to see how blood flows through your heart. MEDLINE PLUS: http://nlm.nih.gov/medlineplus/ency/article/003876.htm

Thallium and sestamibi stress tests are nuclear imaging methods that provide a view of the blood flow into the heart muscle, both at rest and during activity. MEDLINE PLUS: http://nlm.nih.gov/medlineplus/ency/article/007201.htm