6.5 - Medical Imaging Flashcards
What is Compton Scattering?
The effect whereby an X-ray deflected by interaction with an orbital electron has a longer wavelength than its initial wavelength. The electron is ejected from the atom at high speed.
What is Attentuation?
A gradual decrease in intensity
What is the Attenuation (or absorption) coefficient?
A constant used to calculate how the intensity of X-rays decreases as they pass through a material
What does CAT stand for?
Computerised Axial Tomography
What is a CAT scan?
A process using multiple X-ray scans to produce images of ‘slices’ through the body in one plane, in order to produce a 3D image
What is a Gamma Camera?
It detects gamma photons emitted from a patient given a radioactive tracer. This is used to produce a real-time image of the path of the tracer through the body
What is a Tracer?
A radioactive substance either ingested by or injected to a patient. It emits gamma photons to be detected by a gamma camera
What is a Collimator?
A device for producing a parallel-sided (collimated) beam of electromagnetic radiation
What is a Scintillator?
A material that produces many photons of visible light when struck by a high-energy photon
What is a Photomultiplier Tube?
A device used to give a pulse of electrons for each incident photon
What does PET stand for?
Position Emission Tomography
What is a PET Scan?
The use of gamma photons produced when positrons annihilate with electrons inside the body to map out biologically active areas within the body
What are Ultrasound Waves?
They are longitudinal waves above the upper limit of the audible range, with frequencies greater than 20,000Hz
What is a transducer?
A device, such as a microphone, which converts a non-electric signal (e.g. sound) into an electrical signal
What is the Piecoelectric effect?
The change in volume of a material when a p.d. Is applied across its opposite faces. Alternatively, it is the production of an induced e.m.f when certain crystals are placed under stress
