7. Medical Physics Flashcards
(44 cards)
A-Scan:
For scanning tissue.
Involves placing an ultrasound emitting transducer on the surface of the body, and then measuring reflections of emitted pulses.
Used to measure the foetal head size during pregnancy.
Accomodation:
The name given to the eye’s focusing process.
Acoustic Impedance:
The product of the speed of sound and the density of the specific medium.
Astigmatism:
A sight defect caused by a misshapen cornea.
B-Scan:
A method of scanning tissue, used for more complex structures than A-scans.
Instead of the echo signals controlling the y-gain (as in A-scans), they control the brightness of the oscilloscope spot.
Used to determine the placenta’s position during pregnancy.
Barium Meal:
It is consumed by the patient and has significant difference between the density of the area being scanned and the rest of the body.
Barium is chosen due to its high proton number.
Bone-Soft Tissue Boundary:
A boundary at which the acoustic impedance is very large. This means that ultrasound is more intensely reflected.
Ceruminous:
The wax glands that line the ear canal and protect the eardrum.
Ciliary Muscles:
Circular muscle fibres responsible for making changes to the lens’ shape.
Cones:
A light sensitive cell that is used to detect high light intensities. Each cone is connected to a nerve fibre that joins it to the brain and so results in detailed, colour images.
Air-Soft Tissue Boundary:
A boundary at which nearly all incident ultrasound pulses are reflected, due to there being a very large acoustic impedance difference.
How do CT Scans work?
What do they produce?
A scanning method that produces a cross section of the body
By rotating a monochromatic x-ray beam around the body, in combination with a series of detectors.
Decibel:
The unit used for sound intensity.
What are Flat-Panel Detectors?
A light detecting panel that is used in medical imaging.
They are faster and more sensitive to light differences than traditional film.
Where are Gamma Cameras used?
And what are they?
A type of detector used in PET scanners, consisting of a photomultiplier tubes that convert gamma photons into electrical pulses.
Hypermetropia:
The name given to long sightedness.
Iris:
A coloured region of the eye that is partly responsible for controlling that amount of light that enters.
Linear Attenuation Coefficient:
X-rays attenuate when it passes through matter. The linear attenuation coefficient is the ratio of the fractional reduction of intensity over the thickness of the layer.
Magnetic Resonance Imaging (MRI) :
A scanning method that involves the patient lying in a very strong cylindrical magnet. Electromagnetic radiation is emitted that causes a reorientation of hydrogen nuclei. When they return to their original positions radiofrequency radiation is emitted and detected.
Mass Attenuation Coefficient:
The linear attenuation coefficient divided by the density of the material being passed through.
Myopia:
The name given to short sightedness.
-far point of eye is closer than infinity
-cant focus on objects further than far point
Piezoelectric Effect:
An effect shown by crystals like quartz. When a potential difference is applied, the crystal will mechanically deform. Likewise, when the crystal is deformed, a potential difference is produced.
Positron Emission Tomography (PET) Scans:
A scanning technique that produces cross-sectional and 3D images. It involves a radionuclide being injected into the body, which then releases gamma photons that are detected by the scanning machine.
Retina:
The light-sensitive region, found at the back of the eye.
