Using Ultrasound in Medical Imaging
Model Answer
Explain the principles of using ultrasound to obtain diagnostic information about internal body structures.
- A pulse of ultrasound is emitted by a transducer.
- Ultrasound wave is reflected at boundaries.
- Reflected pulse is detected by the transducer.
- Reflected wave is processed and displayed.
- Time delay between generation and detection gives information about depth.
- Intensity of reflected wave gives information about the nature of the boundary.
- A coupling gel is used to minimise reflection at the skin.
- Ultrasound waves are generated and detected by a quartz crystal.
- Degree of reflection depends upon specific acoustic impedances of the two media at the boundary.
Model Answer
Describe how reflected ultrasound pulses may be used to obtain diagnostic information about internal body structures
- Time delay between generation and detection gives information about depth.
- Intensity of reflected wave gives information about nature of boundary.
Why are pulses used
- So that there is no interference between transmitted and reflected waves.
- A single crystal is used to generate and detect ultrasounds in the transducer, therefore it cannot simultaneously generate and detect ultrasound. It must send a pulse and wait for detection before sending another pulse.