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Ultrasound physics 1

part 1

Lateral Resolution is improved by... Focusing
A focused tx-r produces the best picture with the... Focal zone
If the beam tx-r Q is high, its bandwidth is... Narrow
Axial Resolution (SPL/2) can be improved by... Shorter impulse length
Which one of the following statements are true about a single pulse ultrasound from a tx-r Contains a range of frequencies
If (2) sound beams have the same acoustic power, the one with the _______ will have the highest intensity. smaller
Compared to audiable sound, the frequency of ultrasound is ________. higher
Which of the following frequencies is in the ultrasound range? a) 10 khz b) 10,000hz c)1 mhz d)1 khz c) 1 mhz
In soft tissue, as frequency increases, wavelenth ________. decreases (Wavelength = PS/F
PS increases with _______ increases. a) density b) stiffness stiffness
To increase the depth of penetration of a sound beam, we must __________. a)Decrease freq. b)Increase velocity a)Decrease freq. (due to attenuation)
Increasing the frequency is improved for: a) depth of penetration b)refraction c)axial resolution c)axial resolution (axial res.= SPL/2 = # of cycles in a pulse X Wavelength(wavelength= PS/F)
Which UNFOCUSED tx-r would provide to the LONGEST focal length? a) 10mhz, 6mm b) 7.5mhz, 6mm c)10mhz, 4mm d)7.5mhz, 4mhz a) 10mhz, 6mm
The speed of sound in soft tissue is ___m/s 1,540 m/s
The diagnostic frequency range: a)5-10khz b) 2-12mhz c) 1-1000mhz d)2-12khz b) 2-12mhz
Attenuation along a sound path is a decreasing in.... a)freq. b)amp c)intensity d) both b & c d) both b & c (freq & intensity)
Calculate the attenuation in soft tissue for frequency 6mhz, a distance of 10cm... (clue: know the attenuation formula) total atten.=atten. coef. x depth (atten. coef. = f/2) Total atten.= 6/2 x 10cm Total atten.= 3db/cm x 10 cm Total atten.= 30db
When scanning the breast, which of the following tx-r is MOST SUITABLE? a) 2.5mhz b) 3.5 mhz c) 5.0mhz d)7.5mhz d)7.5mhz (higher freq. due to attenuation for more superficial parts
What can you do to improve the Temporal Resolution? Decrease focal zones (space of scan -line
Which intensity level is always going to be the lowest? SATA
Shadowing are artifacts caused by: A strong reflector
TGC controls serve to: The T.G.C. control compensates for the effects of attenuation by progressively increasing the amount of amplification applied to signals with depth (time).
Intensity Reflection Coefficient equation: [Z2 - Z1/ Z2 + Z1]Squared x 100 =
According to Snell's Law, the angle of trans. is related to the incident beam angle and ________? The related sound in (2) mediums
Which of the following parameters is not adjustable by the operator controls by the frequency. PS = Propagation Speed
A sound wave leaves the tx-r and travels through soft tissue, 1 sec later the echo returns to the tz-r. What is teh distance from the tx-r to the reflection that produced the echo. .77 mm (half of propagation speed of 1.54mm/sec
High frequency tx-r have: shorter wavelength and less penetration.
Bright areas in grey scale imaging indicate: strong echos
When you adjust the acoustic power by 3 decibels, which of the following must accurately describe this adjustment? 3db = 50% or halved.
The impedance formula = = PS x Density
For a perpendicular incidence, if the ITC is 96%, what is the intensity coefficient? 4
Which of the following quantities varies most w/ DISTANCE from the tx-r phase? a) axial resolution b) lateral resolution c) freq. d) wavelength e) period b) lateral resolution
Which of the following is a characteristic of a medium through which sound is propagating Impedence
For perpendicular incidence, if the incidences are the same, what happens? Will completely transmit
Oblique incidences propagation speed of two media are equal, but density are different incident angle = reflection & transmission angle
Increase in Spacial Pulse Length... none of the above (multiple choice)
Place the following media in order of increasing sound propagation speed from slowest to fastest: Gas, Solid, and Liquid Gas, Liquid then Solid
If the frequency of sound is above 20khz, what kind of sound spectrum is it? Ultrasound
Period x # of cycles in a pulse = Pulse duration
Te propagation speed of a sound wave is primarily dependent on ______ through which sound is being transferred. material
What are the units for DF (duty factor) %
Wavelength is the measure of _____. distance
How many cycles are there in 1 sec continuous wave 3mhz? none of the above (multiple choice)
The fraction of time that a pulse is actually ON (formula to determine answer) DF= PD/PRF
Period when applied to US is: the time it takes to complete a single wave cycle
If frequency decrease the Wavelength will _________> Increase
Source can be described as: mechanical vibration that can be transmitted through wavelength.
The PRF # of pulses ______. per sec
SPL is = the length of space over which one pulse occurs
Acoustic impedance is: the density of tissue x (PS) speed of sound in tissue
Which of the following increases as frequency increases... all of the above (multiple choice)
The term for a tx-r that has array of rectangular element in straight line... linear array
The non-focused tx-r's another name for near = Freznol zone
What improves grey scale resolution: adding matrix boards
Created by: Sharita