BRAINCAKEUltrasound
Ultrasound is sound with a frequency above 20 kHz, above the range of human hearing. Like all sound, it is a longitudinal wave: the particles of the medium vibrate back and forth along the direction the wave travels, making compressions and rarefactions.
Medical ultrasound usually uses frequencies of about 1 to 15 MHz. It travels through soft tissue at about 1500 m s−1. When it reaches a boundary between two different tissues, part of it is reflected; the reflected pulses (echoes) are used to make images.
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Key terms in this lesson
- attenuation
- A decrease in the intensity of a beam of radiation as it passes through matter, due to absorption or scattering.
- resolution
- The ability of an imaging technique to distinguish two closely spaced points or structures as separate.
More in Medical Imaging
- Technetium-99m and Fluorine-18
- The Gamma Camera
- Diagnosis with a Gamma Camera
- PET Scanning
- The Piezoelectric Effect
- Ultrasound Transducers
- A-scans and B-scans
- Acoustic Impedance
All 20 lessons in Medical Imaging · All OCR A-level Physics topics