EASY
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The reflection of ultrasound allows the image to be generated by the ultrasound machine.

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Important Questions on Medical Imaging

EASY
SONAR is an application of acoustics.
HARD
(b) Brain tissue has a density of 1.04×103 kg m-3 and ultrasound travels at 1.58×103 m s-1 through it. Calculate the acoustic impedance of brain tissue.
HARD

Determine the fraction of the intensity of an ultrasound beam that is reflected when a beam is incident normally on a boundary between water and fat. (Use values from Table )

Material Density/kg m-3 Speed of sound /ms-1 Acoustic impedane /106kgm-2s-1
Lead zirconate titanate 7650 3790 29.0
Quartz 2650 5700 15.1
Polyvinylidese diflouride 1780 2360 4.20

 

MEDIUM
What do you mean by the acoustics of buildings? Suggest four steps that can be taken, while constructing buildings, to avoid the problems which may occur due to multiple reflection of the sound.
EASY
What are the Essential and Important Differences between A-Scan and B scan ?
HARD

(c) This is the trace formed on the screen of an oscilloscope when ultrasound is reflected from the front and rear surfaces of the head of a foetus. The time-base of the oscilloscope is set at 10μsiv-1.

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(ii) Calculate the diameter of the head of the foetus.

HARD

Piezo-electric crystals have many applications other than in ultrasound scanning. For example, they are used in:

(d) the auto-focus mechanism of some cameras (to move the lens back and forth).

MEDIUM

Represent the union of two sets by Venn diagram for each of the following.

X={x | x is a prime number between 80 and 100}

Y={y | y is an odd number between 90 and 100}

HARD
Define the threshold of hearing.
HARD
Calculate the acoustic impedance of muscle tissue. (Density =1075 kg m-3; speed of sound =1590 m s-1.)
EASY
State any two application of acoustics
MEDIUM
B-scan is considered the _____ scan.
HARD
For ultrasound of frequency 3.5MHz, the acoustic impedance of muscle is 1.78×106 kg m-2 s-1, and that of soft tissue is 1.63×106 kg m-2 s-1.
Calculate the percentage of the incident ultrasound reflected at a muscle-soft tissue boundary.
EASY
The branch of physics which deals with the study of production, transmissions and reception of sound is called?
HARD

The ultrasound image shown in Figure clearly shows the baby's skin and some bones. Explain why these show up clearly while softer organs inside its body do not.

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HARD

(c) This is the trace formed on the screen of an oscilloscope when ultrasound is reflected from the front and rear surfaces of the head of a foetus. The time-base of the oscilloscope is set at 10μsiv-1.

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(i) Explain why the second peak is lower than the foetus.

HARD
Explain why ultrasound cannot readily be used to examine the brain. Suggest one or more alternative scanning techniques that can be used for this.
MEDIUM
A transducer produces ultrasonic waves of frequency 800kHz. The speed of sound in the crystal is 5200 m s-1. Calculate the optimum thickness for the crystal.
EASY
What is the reflection of ultrasound?