The Gamma camera:

The gamma camera is used to detect photons of gamma radiation from radioactive nuclei injected into the body, it can be used medical imaging to find tumors, blockages or certain types of tissue in the body.

Radioisotopes

Radioisotopes used in medical imaging are put into patients bodies and recorded on the outside using a gamma camera. Gamma radiation is used as it isn’t as ionising as Alpha or Beta but is more penetrating however, this doesn’t mean it isn’t dangerous. Radioisotopes must have a short half life, so the isotope quickly dies down after it isn’t needed to minimise exposure and so that only a small dose of the isotope is needed. Many radioisotopes are produced artificially in hospitals using a particle accelerator. The most common one is Technetium-99m (the m stands for metastable) it can be used for monitoring the functions of major organs, it loses energy in the form of gamma photons of energy 140 keV and has a half life of six hours.

Medical Tracers

Radioisotopes need to be chemically combined with elements to make sure they combine with the correct tissues and reach the correct parts of the body when injected. These radioisotopes connected with elements are designed to target the correct parts of the body and are called medical tracers or more complexly radiopharmaceuticals. They can be used in conjunction with a gamma camera to find irregularities in the function of the body.

How the Camera Works

The gamma camera detects gamma photons emitted from the medical tracer in the patient and produces an image showing the concentrations of the medical tracer, it does this by:
1.Turning the gamma photons into an image starts when the gamma photons enter the collimator, which acts as a filter. Only photons going in the same direction as the collimator are allowed to pass through, if the photons come at an angle they are absorbed as the collimator is made out of lead.
2.After the collimator the photons reach the scintillator and on contact have a one in ten chance of interacting with it, if they do interact thousands of photons of visible light are produced.
3.The photons of light then travel through the light guide to the photomultiplier tubes, which are arranged in a hexagonal pattern, and convert the photons into electrical pulses.
4.The pulses are sent to a computer to be processed and turned into an image.