BSIP, MENDIL / SCIENCE PHOTO LIBRARY BSIP, MENDIL / SCIENCE PHOTO LIBRARY
Blood pressure measurement. Doctor measuring the blood pressure in an elderly patient's leg. The sphygmomanometer (black cuff) is used to take the blood pressure of the main blood vessels. The pressure in the smaller blood vessels is measured using Doppler ultrasound. High-frequency sound waves (ultrasound) are produced from the trans- ducer (centre left). An image is formed from waves reflected back to the transducer by internal body structures. Blood flowing through the arteries alters the frequency of the reflected sound waves. The alteration of wave frequency by motion is called the Doppler effect. These measures allow the health of the blood system to be assessed.
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