Topic Option: Medical Physics Flashcards
Outer Ear
shaped to channel air vibrations (sound) to the tympanic membrane
Tympanic Membrane
ear drum
Middle Ear
converts the oscillations of the ear drum into oscillations in the fluid of the inner ear at the oval window
Ossicles
three small bones in the inner ear – malleus, incus and stapes
Inner Ear (especially Cochlea)
converts the oscillations in the fluid of the inner ear into electrical signals that are sent along the auditory nerve to the brain
Impedance Matching
a mechanism for transmitting, rather than reflecting, as much of the sound energy from the air to the cochlea as possible – without this mechanism for pressure transformation between media of different densities (air and fluid), most sound would be reflected rather than transmitted into the cochlear fluid
Sound Intensity
Power per unit area of a sound wave(NOTE: Intensity depends on the square of the amplitude of the sound wave.) (NOTE: There is a logarithmic response of the ear to intensity.)
Loudness
The response of the ear to intensity
Sound Intensity Level (IL)
ten times the common logarithm of the ratio of the intensity of a sound to the sound intensity at the threshold of hearing (measured in decibels (dB))
Selective Frequency Loss
conductive loss of hearing for a particular range of frequencies
Tinnitus
temporary deafness across the frequency range due to short-term exposure to loud sounds (“ringing” in the ears)
Attenuation
Absorption of energy from beam
Half-Value Thickness (x1/2)
the thickness of a material needed for a beam (of X-rays) to be attenuated (reduced in intensity) by 50%
Attenuation Coefficient (μ)
Probability of a single photon being absorbed in 1m of a material
Computed Tomography (CT) Scan
an X-ray imaging technique – X-rays and detectors are rotated around a patient and a computer combines the information to produce a 3-D interior picture
Ultrasound Scan
medical imaging technique in which high frequency (20kHz) sound waves are transmitted and reflected from soft tissue
Piezoelectric Crystals
quartz crystals that change shape when an electric current flows and can be used with AC voltage to produce and detect ultrasound
Acoustic Impedance (Z)
the product of the density of a substance and the speed of sound in that substance
A-scan
amplitude modulated scan – presents the information from an ultrasound probe as a graph of returned intensity versus time
B-scan
brightness modulated scan – Operator moves ultrasound generator and computer records echo returns.
Nuclear Magnetic Resonance (NMR) Imaging
medical imaging technique that involves the use of a non-uniform magnetic field in conjunction with a large uniform field to cause nuclei to broadcast radio waves used to image the patient
Pulse Oximetry
laser technique for measuring the oxygen content of the blood by shining red or infrared light through a thin part of a patient’s anatomy
Endoscope
tube with a collection of optical fibers using lasers to look inside the human body
Radiation Dosimetry
techniques for measuring the amount of ionizing radiation
