Background
Diagnostic sonography or
ultrasonography (US) is an imaging technique that uses high-frequency sound
waves to locate internal body structures such as muscles, tendons and joints. sonography
has diagnostic applications in nearly all areas of clinical medicine. In hand
surgery, US is used as a first-line imaging procedure to detect soft-tissue
masses, traumatic injury to ligaments or tendons in the wrist and hand, and as
needle guidance during ganglion aspiration and steroid injections.1,2
Historical Overview
French physicist Pierre
Curie’s discovery of piezoelectricity in 1880 is considered the first discovery
of US. In 1915, French physicist, Paul Langevin developed sonographic imaging
by inventing the first transducer. Interestingly, with the sinking of the
Titanic in 1912, scientists were interested in methods for detecting submerged
objects, especially during times of war (eg, submarines). Austrian neurologist
and psychiatrist, Karl Dussik was the first physician to use US in medical
diagnosis of brain tumors 1942. In 1948, American internist, George Ludwig, was
the first used US to detect gallstones. Perhaps the most commonly known use of
US in obstetrics and gynecology was pioneered by Ian Donald in 1958.
Description
Most modern US equipment
displays the dynamic information in real time, such that the images are
obtained in any plane by moving the transducer (probe). The US sound wave is
typically produced by a piezoelectric transducer. Strong, short electrical
pulses from the US machine drive the transducer at the desired frequency (1–18
MHz). The application of a water-based gel between the skin and the probe
ensures efficient transmission of the sound wave into the body. The sound wave
is partially reflected anywhere there are acoustic impedance changes in the
body; some of the waves are reflected back to the transducer. The transducer translates
these vibrations into electrical pulses that are then processed and transformed
into a digital image displayed on the screen. The most well-known type of image
is B-mode, which displays the acoustic impedance of a two-dimensional
cross-section of tissue. Other types of images can display blood flow, movement
of tissue or the anatomy of a three-dimensional area.
