The Gamma Camera
The gamma Camera is displayed to the left, you need to be familar with how its key features.
- Collimator Tubes - The gamma ray photons travel along the axis of these lead tubes. The quality of the image can be improved by having longer / thinner tubes.
- Scintillator (NaI Crystal) - The gamma ray photon produces many visible light photons
- Photomultiplied Tubes - Electrons are produced by the photons of light
- Computer - The electrical signals are used to create an image.
Positron Emission Tomography (PET)
PET scanners take advantage of the annihilation event between a positron and an electron. The key stages are:
- A patient is injected with a positron emitter.
- An annihilation event between a positron and an electron takes place producing two gamma ray photons
- These gamma ray photons travel is opposite directions
- The patient is surrounded by a ring of gamma detectors. The arrival times of the photons are used to pinpoint areas of increased brain activity.
- A 3D image is made by a computer making use of the detector signals.
Computerised Axial Tomography (CAT) Scanner
CAT scans provide a way of creating a 3D image using X-rays.
- The x-ray tube rotates around the patient, allowing x-ray beams to pass through the patient at different angles.
- The shape of this beam is thin fan (see diagram)
- With the help of a computer, images of slices of the patient are produced.
- By moving the x-ray tube we get an image of a different slice.
The fact that the images produced are in 3D is one advantage of CAT scans over a traditional X-ray. Another advantage is that there is better contrast between different soft tissue.