SPI PRACTICE QUESTIONS.docx

Sound waves are: - correct answer longitudinal, mechanical The speed of sound in soft tissue is closest to: - correct answer 1,500 m/s The frequency closest to the lower limit of ultrasound is: - correct answer 15,000 Hz Which is not an acoustic variable? - correct answer intensity The effects of soft tissue on ultrasound are called: - correct answer acoustic propagation properties All of the following are true EXCEPT: - correct answer two waves with identical frequencies must interfere constructively Put in decreasing order: deci, deca, micro, centi - correct answer deca, deci, centi micro ______________ is the time to complete one cycle - correct answer period Which of the following sound waves is ultrasonic and least useful? - correct answer 30 KHz What is the frequency of a wave with a 1 msec period? - correct answer 1 KHz ______________ is the distance covered by one cycle - correct answer wavelength Which of the following is determined by the source and the medium? - correct answer range resolution Propagation speed = ______________ x wavelength - correct answer frequency As a result of ______________, the propagation speed increases - correct answer decreasing compressibility and density Put in decreasing order of propagation speed: gas, liquid, solid - correct answer solid, liquid, gas If the frequency of US is increased from 0.77 MHz to 1.54 MHz, what happens to the wavelength? - correct answer halved A sound wave's frequency is 10 MHz. The wave is traveling in soft tissue. What is its wavelength? - correct answer .15 mm If the frequency of an US wave is doubled, what happens to the period? - correct answer halved If the frequency of US is increased from 0.77MHz to 1.54MHz, what happens to the propagation speed? - correct answer remains the same The units of PRF are: - correct answer per minute The time from the beginning of a pulse until its end is ______________? - correct answer pulsed duration What happens to the speed of sound in a medium when the bulk modulus of the medium increases? - correct answer faster ___________ resolution is determined by SPL - correct answer radial or axial If a wave's amplitude is doubled, what happens to the power? - correct answer quadrupled Power of sound has units of: - correct answer watts If the intensity of a sound beam remains unchanged while the beam area is reduced in half, what has happened to the power? - correct answer halved Which of these intensities is the smallest? SATP, SPTP, SATA - correct answer SATA The duty factor for CW ultrasound is: - correct answer 1.0 What is the minimum value of the duty factor? - correct answer 0% What are the units of intensity? - correct answer watts/cm2 What happens to the speed of sound in a medium when the bulk modulus of the medium decreases? - correct answer slower The units of attenuation are ______; this is a ______________ scale - correct answer dB, logarithmic Sound intensity is decreased by 75%. How many decibels of attenuation is that? - correct answer 6 dB The fundamental frequency of a transducer is 2.5 MHz. What is the second harmonic frequency? - correct answer 5 MHz A pulse is emitted by a transducer and is traveling in soft tissue. The go-return-time, or time-of-flight, of a sound pulse is 130 microseconds. What is the reflector depth? - correct answer 10 cm If a 5 MHz sound wave is traveling in the tissues listed below, which will have the longest wavelength? - correct answer bone If a 5 MHz sound wave is traveling in the tissues listed below, which will have the shortest wavelength? - correct answer air What is the approximate attenuation coefficient of 1 MHz US in soft tissue? - correct answer .5 dB/cm Rayl is the unit of: - correct answer impedance Impedance is the _________ of _________ and _________ - correct answer product, propagation speed, density What are attenuation's three components? - correct answer scattering, reflection, absorption For soft tissue, the approximate attenuation coefficient in dB/cm is equal to one-half _________ in _________ - correct answer frequency, MHz As the impedance of two media become vastly different , the: - correct answer reflection increases The angle between two media is 90 degrees. What is this called? - correct answer orthogonal incidence The angle between two media is 56 degrees. This is called: - correct answer oblique incidence Refraction only occurs if there are: - correct answer oblique incidence and different propagation speeds With normal incidence, what factors affect refraction? - correct answer none of the above T/F: With right angle incidence, reflections are always generated at a boundary if the propagation speeds of the media are different - correct answer false _________ is a redirection of US in many directions as a result of a *rough* boundary between two media - correct answer scattering Which of the following tissues will most likely create Rayleigh scattering? - correct answer red blood cells T/F: With normal incidence, the angle is 180 degrees. - correct answer false Under which of the following conditions is axial resolution improved? - correct answer decreased SPL Snell's law describes the physics of: - correct answer refraction The most likely amount of reflection at a boundary between soft tissues is: - correct answer 1% The most typical amount of transmission at a boundary in biologic media is: - correct answer 99% Sound is traveling from medium 1 to medium 2. Propagation speeds of M1 is 1,600 m/s and M2 is 1,500 m/s. There is oblique incidence - correct answer angle of incidence = angle of reflection T/F: Doppler shifts ALWAYS occur is the sound source and receiver are in motion - correct answer false Which of the following is associated with power Doppler? - correct answer poor temporal resolution and flash artifact The Doppler shift is a measure of: - correct answer difference between incident & reflected frequencies