Flashcards
Medical Imaging Procedures
Cards in this deck (4)
- 1How are X-rays produced?1. Thermionic emission from a coil produces a high-intensity beam of electrons
2. The beam is directed at a rotating heavy-metal anode (e.g. tungsten) - the electrons accelerate towards the anode
3. When the electrons reach the anode, they decelerate and scatter through collisions with the positive metal ions
4. The electrons' KE is released as X-ray photons in an effect known as bremsstrahlung (braking radiation)
5. The X-rays escape through a window in the side
6. Deceleration heats up the anode, so it rotates to distribute the heat more evenly and enable a higher-intensity electron beam to be used. - 2How is a conventional X-ray taken?1. Patient lies down on bed
2. X-rays are fired from an X-ray generator
3. The X-rays are absorbed by denser material (e.g. bone) - materials with a higher linear attenuation coefficient
4. The remaining X-ray photons pass through to a photographic plate
5. Where an X-ray photon hits, it darkens the plate and produces a negative image - 3How does a CAT scan work?1. Patient lies down on a bed, surrounded by a ring of X-ray detectors
2. An X-ray emitter rotates around the ring, exposing the patient to a fan-shaped beam of X-rays in all directions
3. Detectors opposite the emitter receive the radiation and send the information to a computer
4. The computer uses the information to build up a 3D image.
5. The radiographer can use the image to view 'slices' through the patient on a computer screen. - 4How does a gamma camera work?1. Patient lies on a bed, having received a medical tracer
2. A gamma camera is placed above them, consisting of a collimator (honeycomb of parallel tubes surrounded by lead), a scintillator crystal of sodium iodide and
3. The gamma photons leave the patient and pass
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- A-level OCR Physics A-level Flashcards on Medical Imaging Procedures, created by James Norman on 16/03/2020.
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- James Norman
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