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PhysicsModule4

Questions from the Module 4 of the Physics component

QuestionAnswer
Acoustic interface Relates to the summation of superpositioned waves; constructive & destructive
Attenuation Decrease in intensity as beam travels through a medium
Power a measure of the total energy transmitted summed over the entire cross
Intensity describes the amount of energy in the beam. The rate that a wave transmits energy over an area. W/cm2
Energy the capacity or ability to do work, make something happen, or to change. Occurs in many forms.
Amplitude normally used to refer to the particle displacement, particle velocity, or acoustic pressure of a sound wave. Amplitude also indicates the strength of the detected echo or the voltage induced in a crystal by a pressure wave.
Diffraction a measure of the span of signal magnitudes that can be represented or processed by the various components of a system.
Decibel Quantify Intensities/power/amplitude/dynamic range/attenuation
Depth of penetration How far into the body the transducer can send an ultrasound wave and still detect its echo
Attenuation coefficient db/cm
Scattering same as reflection
Refraction The redirection of the transmitted sound beam which may occur when the beam crosses an interface
Reflection Sound being redirected toward the sound source
Absorption Absorption is the dominant form of attenuation in soft tissue. Absorption increases exponentially with increasing frequency
Incidence an occurrence or frequency of occurrence; refers to the original, unreflected ultrasound beam produced by the transducer
Intensity rate at which energy passes through a unit area. Intensity = power in a wave divided by the area over which the power is spread (I=P/A
Density mass/unit area
Rayl a unit of impedence ; 1 rayl =(1kg)/(m2*s)
Describe a specular reflector large, smooth and flat relative to the wavelength
Describe an interface that causes scattering Large but rough relative to the wavelength or smaller than the width of the sound beam (or one wavelength)
Describe Rayliegh scatterers very small relative to the wavelength (RBS’s)
List components responsible for sound attenuation Depth of penetration, frequency of the beam, attenuation coefficient; Interference, Diffusion, Absorption, Reflection (scattering), Refraction
What is normal incidence? When the US beam is perpendicular to the interface surface, allowing maximum detection of the reflected angle
What is oblique incidence? When the US beam is not perpendicular to the interface surface, the US beam is not reflected back to the transducer
Discuss the relationship between frequency, attenuation, and path length As frequency increases, attenuation increases and path length decreases
Compare the relative values for attenuation and speed of sound in soft tissue, bone, air, water and fat. Z values( acoustic impedance) : Steel>bone>ice>soft tissue>water>fat>airC Values (sound propagation speed): steel>ice>bone>soft tissue>water>fat>air
Identify structures within the body causing reflection and scattering. Scattering: liver, gallbladder stonesReflection: Diaphragm, pericardium, bladder wall
Created by: sbeard1