PHYSICS class 4:II
About this set
Created by:
cole1321 on September 30, 2012
Description:
The second part of physics lecture 4 (9/14/10)
Copied From:
Set copied from CarrieMines
Log in to favorite or report as inappropriate.
Order by
48 terms
Terms | Definitions |
|---|---|
 What are the 3 factors of attenuation? | absorption, scattering, reflection |
| Aas the sound beam travels through the body, what happens to amplitude and intensity? | reduced |
| Heat energy is produced when this happens to the sound. | absorbtion |
| This occurs at the tissue interfaces. | reflection and scatter |
| The amount of heat produced by it is too small to cause a measurable temperature change. | diagnostic ultrasound |
| Sound energy that cannot be recovered is caused by what? | non-perpendicular incidence |
| If a woman is less than 5 weeks pregnant none of this should be used to scan the embryo. | color or Doppler |
| Attenuation in tissue is hightly dependent on what? | probe frequency |
| The higher the frequency, the higher the ________ and ________. | attenuation and absorption |
| The higher the frequency the lower the _________. | penetration |
| What units are used to quantify attenuation? | decibles (db) |
| Decibles are units of what? | POWER and % of acoustic output |
| If frequency is increased by 1, then what happens to attenuation and absorption? | increased by 1 |
| What is the maximum of acoustic output? | 100% |
| What does blood disapate? | heat |
| Other than attenuation, decibles can also be used to measure what? | instrument output, dynamic range, gain |
| A logarithmic way of comparing ratio of 2 intensities that include attenuation and amplification is to measure in what? | decibles |
| The amount of attenuation/per cm/per MHz which equals db/cm is the what? | attenuation coefficient |
| At 1.54 mm/μs the lung has what type of attenuation? | high |
| At 1.54 mm/μs bone has what type of attenuation? | low (it's a reflector) |
| The range of the attenuation coefficient of soft tissue is what? | 0.5 - 1db/cm/MHz |
| When power is increased by 3db, what happens to intensity? | doubled |
| When power is decreased by 3db, what happens to intensity? | halved |
| What is the intensity of power increased by? | 3db |
| As frequency and attenuation increase, this will also increase... | attenuation coefficient |
| As penetration decreases, these will increase... | attenuation and resolution |
| The distance that a sound must travel to reduce the intensity of sound to 1/2 of its original value is what?(decease by 3db) | half value layer thickness |
| The shorter the spatial pulse length, the ______ the penetration will be, but the ______ the resolution will be. | less; higher |
| For superficial structures, you need to have a shorter what? | spatial pulse length |
| For abdominal imaging you need what? | high penetration |
| The time that the pulse is on (measured in μsec) is what? | pulse duration |
| The length of the pulse (measured in mm) is what? | pulse length |
| If there are many cycles in a pulse it has a longer ________. | wavelength |
| A pulse that creates more penetration is a what? | long pulse |
| The shorter the wavelength the fewer the _______ in the pulse. | cycles |
| A short pulse will create what? | less penetration |
| What does pulse travel time equal? (time it takes for one pulse to travel round trip) | 13 μsec/cm |
| The maximum displacement of any particles measured from an undistured postion is what? | amplitude |
| Amplitude of a wave decreases as it what? | travels |
| How can amplitude be increased? | POWER/OUTPUT |
| If amplitude is doubled than intensity is... | quadrupled |
| If amplitude is halved than intensity is... | quartered |
| What is the energy in a sound wave? | intensity |
| Although intensity can be adjusted with the POWER/OUTPUT, it originally is determined by what? | sound source (transducer) |
| mW/cm² is a measurement for what? | intensity (power) |
| 100 mW/cm² is the maximum power used in what? | diagnostic ultrasound |
| What happens to the power in a wave as it travels through a tissue? | decreases |
| What is amplitude² equal to? | power |
First Time Here?
Welcome to Quizlet, a fun, free place to study. Try these flashcards, find others to study, or make your own.