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Ultrasound physics 1
part 1
| Question | Answer |
|---|---|
| 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
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