The photo on the right shows a medical technician using an ultrasound machine to diagnose appendicitis to a patient, without the use of x-rays. The ultrasound imaging technique involves using high frequency sound waves and their echoes. The machine transmits high-frequency sound pulses into the patient’s body using a probe. In the image, the technician presses and moves the probe along the patient’s body. This photo was taken in the St. Louis Children’s Hospital, and obtained from *.
In terms of physics concepts, medical ultrasound techniques involve waves, it is important to understand the nature of a wave. A wave is a traveling disturbance that carries energy from place to place. Ultrasound-imaging machines use ultrasound waves to produce …show more content…
These sound pulses are usually in the order of 1-5 megahertz. The probe is a transducer that uses an array of piezoelectric crystals. When an electrical current from the machine is applied to these crystals, they rapidly change shape. The changes in shape cause vibrations of the crystals, producing ultrasound waves that travel outward. The sound waves then pass through the patient’s skin and into his or her internal anatomy. Sound is a wave that travels in a straight line and requires a medium. Frequency and wavelength are related by the speed of sound in the medium with (v=fλ). V is usually slowest in liquids and gasses and fastest in solids. For example, the speed of sound in a muscle is 1580 m/s while the speed of sound in soft tissue is 1540 m/s. Both the density and the stiffness of the medium determine the speed of sound. As the waves encounter different tissues that hold different characteristics, some sound waves get reflected back to the probe and thus reflect back to the piezoelectric crystals, while some travel on further until they arrive at another tissue or organ before they are reflected back. The probe or transducer also has the ability to picks up the reflected waves and relay them to the ultrasound machine. This is because the crystals can work in reverse and produce electrical signals when it detects high-frequency pressure waves. The returned echoes are converted to electrical signals by the probe and are then processed by the computer, showing points of brightness on the image corresponding to position and strength of the reflecting echoes. Hence, the same crystals are used to send and receive the sound waves. The distance from the probe to the tissue or organs is calculated using the speed of sound in tissue (1,540 m/s) and the time it takes for each echo to return (Figure 1). This is number is usually on the order of millionths of a
In terms of physics concepts, medical ultrasound techniques involve waves, it is important to understand the nature of a wave. A wave is a traveling disturbance that carries energy from place to place. Ultrasound-imaging machines use ultrasound waves to produce …show more content…
These sound pulses are usually in the order of 1-5 megahertz. The probe is a transducer that uses an array of piezoelectric crystals. When an electrical current from the machine is applied to these crystals, they rapidly change shape. The changes in shape cause vibrations of the crystals, producing ultrasound waves that travel outward. The sound waves then pass through the patient’s skin and into his or her internal anatomy. Sound is a wave that travels in a straight line and requires a medium. Frequency and wavelength are related by the speed of sound in the medium with (v=fλ). V is usually slowest in liquids and gasses and fastest in solids. For example, the speed of sound in a muscle is 1580 m/s while the speed of sound in soft tissue is 1540 m/s. Both the density and the stiffness of the medium determine the speed of sound. As the waves encounter different tissues that hold different characteristics, some sound waves get reflected back to the probe and thus reflect back to the piezoelectric crystals, while some travel on further until they arrive at another tissue or organ before they are reflected back. The probe or transducer also has the ability to picks up the reflected waves and relay them to the ultrasound machine. This is because the crystals can work in reverse and produce electrical signals when it detects high-frequency pressure waves. The returned echoes are converted to electrical signals by the probe and are then processed by the computer, showing points of brightness on the image corresponding to position and strength of the reflecting echoes. Hence, the same crystals are used to send and receive the sound waves. The distance from the probe to the tissue or organs is calculated using the speed of sound in tissue (1,540 m/s) and the time it takes for each echo to return (Figure 1). This is number is usually on the order of millionths of a