1. Positron Emission tomography
Pet scans
Positron Emission tomography

2. Diagnosis
Pet scans show areas of damaged tissues. They do this by detecting areas of decreased blood flow, this can reveal coronary artery disease.
Pet scans can identify active cancer tumours by showing metabolic activity in tissue.

3. The process
Inject the patients with a radioactive isotope with a short half life so it acts like a tracer.
Positrons meet electrons and annihilate emitting high energy gamma rays which are detected. Distribution of radioactivity matches up with metabolic activity.
Isotopes used in pet scans have short half life's. So it's important that it's made in that hospital.

4. Tracers in medicines
Radioactive isotopes are used as traces to diagnose some medical conditions:
The tracer is injected into the patient or swallowed its progress around the body is followed by an external detector.
An example of this is iodine 131, this is absorbed by the thyroid gland.
- only isotopes which emit beta or gamma are used as they can pass out of the body.