Exam code: H556
This question is about the medical use of ultrasound.
a)
In ultrasound scanning, explain what is meant by impedance (acoustic) matching and how it may be achieved.
[2]
b)
There are several different types of ultrasound scanning techniques.
Explain how an A-scan could be used to measure the thickness of a patient’s eye lens. You may draw a diagram to help with your answer.
[3]
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a)
Explain how an ultrasound transducer can emit ultrasound. You do not need to describe the design of the transducer.
[2]
b)
Explain how the reflection of ultrasound at a boundary between two tissues depends on the physical properties of the tissues.
[3]
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The density of a sample of bone is . The speed of ultrasound in the bone is .
Calculate the acoustic impedance of bone.
An ultrasound pulse is incident at the boundary between muscle and bone.
The acoustic impedance of muscle is .
Calculate the intensity reflection coefficient for this boundary.
Describe the principles of an ultrasound B-scan and how it differs from an A-scan.
Your answer should include:
how the ultrasound is produced.
the role of the coupling gel.
how the 2D image is built up.
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