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PhysicsModule4
Questions from the Module 4 of the Physics component
| Question | Answer |
|---|---|
| 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
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