A typical ultrasound transducer used for medicaldiagnosis produces a beam of ultrasound with a frequency of 1.0 MHz.The beam travels from the transducer through tissue and partially reflectswhen it encounters different structures in the tissue. The same transducerthat produces the ultrasound also detects the reflections.The transduceremits a short pulse of ultrasound and waits to receive the reflected echoesbefore emitting the next pulse. By measuring the time between the initialpulse and the arrival of the reflected signal, we can use the speed of ultrasoundin tissue, 1540 m>s, to determine the distance from the transducerto the structure that produced the reflection.As the ultrasound beam passes through tissue, the beam is attenuatedthrough absorption. Thus deeper structures return weaker echoes. A typicalattenuation in tissue is -100 dB/m. MHz; in bone it is -500 dB/m . MHz.In determining attenuation, we take the reference intensity to be the intensityproduced by the transducer In some applications of ultrasound, such as its use on cranialtissues, large reflections from the surrounding bones can producestanding waves. This is of concern because the large pressure amplitudein an antinode can damage tissues. For a frequency of 1.0 MHz, whatis the distance between antinodes in tissue? (a) 0.38 mm; (b) 0.75 mm;(c) 1.5 mm; (d) 3.0 mm.
A typical ultrasound transducer used for medical
diagnosis produces a beam of ultrasound with a frequency of 1.0 MHz.
The beam travels from the transducer through tissue and partially reflects
when it encounters different structures in the tissue. The same transducer
that produces the ultrasound also detects the reflections.
The transducer
emits a short pulse of ultrasound and waits to receive the reflected echoes
before emitting the next pulse. By measuring the time between the initial
pulse and the arrival of the reflected signal, we can use the speed of ultrasound
in tissue, 1540 m>s, to determine the distance from the transducer
to the structure that produced the reflection.
As the ultrasound beam passes through tissue, the beam is attenuated
through absorption. Thus deeper structures return weaker echoes. A typical
attenuation in tissue is -100 dB/m. MHz; in bone it is -500 dB/m . MHz.
In determining attenuation, we take the reference intensity to be the intensity
produced by the transducer In some applications of ultrasound, such as its use on cranial
tissues, large reflections from the surrounding bones can produce
standing waves. This is of concern because the large pressure amplitude
in an antinode can damage tissues. For a frequency of 1.0 MHz, what
is the distance between antinodes in tissue? (a) 0.38 mm; (b) 0.75 mm;
(c) 1.5 mm; (d) 3.0 mm.
Trending now
This is a popular solution!
Step by step
Solved in 2 steps
