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 / 10 6 kgm - 2 s - 1 Lead zirconate titanate 7650 3790 29 . 0 Quartz 2650 5700 15 . 1 Polyvinylidese diflouride 1780 2360 4 . 20

Fraction of intensity is given by I r I o = ( Z 2 - Z 1 ) 2 ( Z 2 + Z 1 ) 2 = ( 1 . 34 - 1 . 50 ) 2 ( 1 . 34 + 1 . 50 ) 2 = 3 . 2 × 10 - 3

HARD

AS and A Level

IMPORTANT

Earn 100

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

(c) guitar pickups (to connect the guitar to an amplifier).

Important Questions on Medical Imaging

HARD

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 30 - Medical Imaging>Questions>Q 11

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).

HARD

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 30 - Medical Imaging>Questions>Q 12

Calculate the acoustic impedance of muscle tissue. (Density

= 1075 kg m^{- 3};

speed of sound

= 1590 m s^{- 1}

HARD

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 30 - Medical Imaging>Questions>Q 13

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	$Density / {kg m}^{- 3}$	$Speed of sound / {ms}^{- 1}$	$Acoustic impedane / 10^{6} {kgm}^{- 2} s^{- 1}$
Lead zirconate titanate	$7650$	$3790$	$29.0$
Quartz	$2650$	$5700$	$15.1$
Polyvinylidese diflouride	$1780$	$2360$	$4.20$

HARD

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 30 - Medical Imaging>Questions>Q 14

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.

Question Image

HARD

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 30 - Medical Imaging>Questions>Q 15

Explain why ultrasound cannot readily be used to examine the brain. Suggest one or more alternative scanning techniques that can be used for this.

HARD

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 30 - Medical Imaging>Questions>Q 16

Two consecutive peaks in an ultrasound A-scan are separated by a time interval of

0.034 ms

. Calculate the distance between the two reflecting surfaces. (Assume that the speed of sound in the tissue between the two surfaces is

1540 m s^{- 1} .

)

HARD

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 30 - Medical Imaging>Questions>Q 17

Explain why an ultrasound B-scan, rather than X-rays, is used to examine a foetus.

MEDIUM

AS and A Level

IMPORTANT

Physics for Cambridge International AS & A Level Coursebook 3rd Edition Digital Access>Chapter 30 - Medical Imaging>Questions>Q 18

Suggest the reason why, in PET scanning, it is important that the positron meets an electron within a very short distance from its point of emission.

Piezo-electric crystals have many applications other than in ultrasound scanning. For example, they are used in: (c) guitar pickups (to connect the guitar to an amplifier).

Important Questions on Medical Imaging

Learn and Prepare for any exam you want !

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

(c) guitar pickups (to connect the guitar to an amplifier).