SPL - ANSWER wavelength x # of cycles
With phased array transducers, the transmitted sound beam is steered by - ANSWER Varying the timing of pulses to the individual piezoelectric elements
What type of wave is sound? - ANSWER mechanical and longitudinal
The Frequency ranges for Ultrasound ...
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SPL - ANSWER wavelength x # of cycles
With phased array transducers, the transmitted sound beam is steered by - ANSWER
Varying the timing of pulses to the individual piezoelectric elements
What type of wave is sound? - ANSWER mechanical and longitudinal
The Frequency ranges for Ultrasound are: - ANSWER > 20,000 Hz (20kHz)
The speed of sound in soft tissue is: - ANSWER 1540 m/s
Linear sequence Array - ANSWER transducer that fires the elements in groups
Unit for Wavelength - ANSWER is millimeters
Enhancement is caused by - ANSWER weakly attenuating structures (such as a cyst)
The wavelength in a material having a propagation speed of 1.5 mm/us employing a
transducer frequency of 5.0 MHz is: - ANSWER 0.3 mm Wavelength= c/f = 1.5mm/us ÷
5MHz = 0.3mm
An ultrasound transducer converts: - ANSWER electrical energy into mechanical energy
and vice versa
The order of attenuation, from the lowest attenuation to highest: - ANSWER fat, muscle,
bone, air
Propagation Speed from the lowest to highest: - ANSWER air, fat, muscle, bone
If the frequency doubled, what to wavelength? - ANSWER Decrease by one half/
Frequency and wavelength are inversely related
What happened to intensity if the amplitude of a signal is halve? - ANSWER Quarted/
Intensity is proportional to the amplitude squared, so if the amplitude is halved, the
resulting intensity is one fourth the original intensity
Duty factor - ANSWER is the percentage of the time the sound is being transmitted
A 3dB gain would indicated in intensity by: - ANSWER 2 times (A gain of 3dB results in
doubling of intensity (or power))
, Ignoring the effects of attenuation, the intensity of ultrasound beam is usually greater at
the focal zone because of: - ANSWER The smaller beam diameter (Intensity equals
power divided by area. The area is smallest in the focal zone; therefore, the intensity is
highest)
B-mode - ANSWER Brightness mode of the dot, which is considered in the z-axis of the
image
Axial resolution is determined by - ANSWER spatial pulse length
Improve axial resolution - ANSWER decreasing the numbers of cycles in a pulse, or
increasing frequency
With phased array transducers, the transmitted sound beam is steered by: - ANSWER
Varying the timing of pulses to the individual piezoelectric elements
If the gain of an amplifier is 18 dB, what is the new gain if the power is reduced by half?
- ANSWER 15 dB
SATA - ANSWER lowest intensity
If the amplitud of a wave is increased threefold, the power will: - ANSWER increased
ninefold
Ultrasound attenuates an average of ____ dB/cm of travel for each megahertz of
frequency. - ANSWER 0.7
It the intensity transmition coefficient (ITC) is 0.74, the intensity reflection coefficient
(IRC) will be: - ANSWER 0.26
Acoustic impedance is define as the product of: - ANSWER the speed of sound in tissue
and density of the tissue
Rayleigh scattering is an example of: - ANSWER a reflector whose size is smaller than
the wavelength
If medium 2 impedance is equal to medium 1 impedance: - ANSWER 100% of the
intensity will be transmitted
What is the total attenuation of 3.5 MHz pulse after passing through 2 cm of soft tissue?
- ANSWER 3.5 dB
The thinner the piezoelectric element, - ANSWER the higher the frequency
A decibel (dB) describes the: - ANSWER ratio of two sound intensities
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