An object lies 7.7 cm beneath the patient\'s skin. How long after the ultrasound
ID: 2033264 • Letter: A
Question
An object lies 7.7 cm beneath the patient's skin. How long after the ultrasound pulse is fired will it be before the echo from this object is detected?
a) 1.54 ms
b) 200 ms
c) 0.01 ms
d) 0.1 ms
The intensity of an echo is 1/10,000 of that of the incident beam. The intensity ratio in decibels is:
a) 20 dB
b) 10 dB
c) - 40 dB
d) - 4 dB
The depth resolution is best when:
a) the wavelength is long
b) the crystal is thick
c) the frequency is high
d) the crystal is lightly damped
A 2mm thick disk composed of lead zirconium titanate will, when excited by a voltage pulse, oscillate at a frequency of 1 MHz. How thick should the crystal be if the required frequency is 4 MHz?
a) 4 mm
b) 1 mm
c) 0.5 mm
d) 0.25 mm
In a continuous-wave Doppler scanner, the frequency of the echo will be greatest if the source of the echo:
a) is approaching the transducer
b) is moving away from the transducer
c) moves at right angles to the direction of the beam
d) is stationary
In soft tissues, ultrasonic waves whose frequency is 3.08 MHz will have a wavelength of:
0.2 mm
b) 0.5 mm
c) 2.0 mm
d) 5.0 mm
An object lies 7.7 cm beneath the patient's skin. How long after the ultrasound pulse is fired will it be before the echo from this object is detected?
a) 1.54 ms
b) 200 ms
c) 0.01 ms
d) 0.1 ms
The intensity of an echo is 1/10,000 of that of the incident beam. The intensity ratio in decibels is:
a) 20 dB
b) 10 dB
c) - 40 dB
d) - 4 dB
The depth resolution is best when:
a) the wavelength is long
b) the crystal is thick
c) the frequency is high
d) the crystal is lightly damped
A 2mm thick disk composed of lead zirconium titanate will, when excited by a voltage pulse, oscillate at a frequency of 1 MHz. How thick should the crystal be if the required frequency is 4 MHz?
a) 4 mm
b) 1 mm
c) 0.5 mm
d) 0.25 mm
In a continuous-wave Doppler scanner, the frequency of the echo will be greatest if the source of the echo:
a) is approaching the transducer
b) is moving away from the transducer
c) moves at right angles to the direction of the beam
d) is stationary
In soft tissues, ultrasonic waves whose frequency is 3.08 MHz will have a wavelength of:
0.2 mm
b) 0.5 mm
c) 2.0 mm
d) 5.0 mm
Explanation / Answer
here,
speed of ultrasound pulse , v = 1540 m/s
x = 7.7 cm = 0.077 m
the time taken after the ultrasound pulse fired will be , t = 2x /v
t = 2 * 0.077 /1540 s
t = 1 * 10^-4 s
t = 0.1 ms
the time taken after the ultrasound pulse fired is d) 0.1 ms