Waves and Light: Ultrasound Imaging

Ultrasound Imaging and Waves

Key Concepts:

Ultrasound refers to sound waves with frequencies higher than the upper audible limit of human hearing.
Ultrasound imaging or sonography involves the use of these high-frequency sound waves to create images of structures within the body, such as tissues, organs and blood flow.

Mechanics of Ultrasound:

Ultrasound devices send waves into the body, which bounce back after hitting structures within.
The probe receives these echoed waves and converts them into electrical signals, which are then processed to create an image.
The depth to which ultrasound waves can penetrate depends on the frequency and intensity of the ultrasound.

Reflection, Refraction and Diffraction:

When the ultrasound wave hits a boundary between two different mediums within the body, some of the wave gets reflected back while some gets transmitted.
The angle of incidence equals the angle of reflection, following the law of reflection.
Refraction of ultrasound waves can occur at boundaries between different tissues and can alter the path of the wave.
Diffraction is minimal with ultrasound waves because of their small wavelength.

Uses and Limitations of Ultrasound:

Ultrasound imaging is used in various diagnostic procedures, from fetal imaging to detecting problems in the heart, kidneys, liver and other organs.
It is non-invasive, safe as it doesn’t use ionising radiation, and captures real-time movement of the body’s internal organs.
However, ultrasound imaging is limited by its inability to penetrate bone and gas. It also has a lower resolution in comparison to other imaging techniques like MRI and CT.

Doppler Effect and Ultrasound:

The Doppler Effect refers to the change in frequency and wavelength of a wave for an observer moving relative to the source of the wave.
In the context of ultrasound, using the Doppler Effect makes it possible to measure velocity of blood or movement of organs within the body.
Doppler ultrasound can detect and measure the rate of blood flow, helping to diagnose conditions such as blocked arteries, heart valve problems and pregnancy complications.