Cardiovascular Sonography is the use of ultrasound to evaluate cardiovascular anatomy. A cardiac sonographer works directly with patients and operates ultrasound equipment which collects heart images. Cardiac physicians and sonographers work as a team during the echo procedure to watchfully examine the blood and heart vessels. This paper discusses the history of Cardiovascular Sonography.
The word ultrasound refers to sound waves beyond the range of human hearing (oscillations above 20,000 cycles per second or 20kHz). The dog whistle is an often-used example. Both sound and ultrasound waves are mechanical vibrations that can only propagate through matter (liquids, solids, and to some extent, gases). The composition and temperature of that matter determines the velocity of these waves. Whenever these waves encounter a boundary (such as an organ wall) or interface between two substances, there is a decrease in velocity, and some of the energy is reflected back as an echo, while the rest of the energy passes through to the next interface. (Kupinski, 2012)
In clinical ultrasonography, a transmitter produces a short pulse (typically a few millionths of a second) of high-frequency electrical oscillations (1 to 10MHz, or million cycles per second). The transducer, acting like a loudspeaker, converts this electric signal into a pulse of mechanical vibrations of about the same frequency and duration. With the transducer pressed firmly against the patient's body, and acoustically coupled to it with gel or oil, the pulse of ultrasound energy enters with little reflection at the skin and propagates inward through soft tissues and fluids. Then, quiescent and acting as a microphone, the same (or another) transducer senses any reflected, much weaker pulses of ultrasound, and transforms them back into electrical signals. Echoes from distinct organs, blood vessels, and other structures are amplified and processed by the receiver, and are sent to a computer, which keeps track of their return times and amplitudes. About a thousandth of a second later, another pulse is produced and sent off in a slightly different direction through the body, and the whole process begins anew. From echo data generated in this fashion, the computer can create a real-time image in which one sees the arms and legs of a fetus move around or a heart valve open and close. (Robertson, 2001)
Ultrasound is particularly useful in the study of soft tissues and organs that are too similar to provide adequate x-ray image contrast. Doppler ultrasound can detect and monitor the flow (or lack thereof) of blood in the arteries and veins. Ultrasound does not use ionizing radiation and usually costs less than other imaging modalities for example magnetic resonance imaging (MRI)or computed tomography (CT) . (Otto , 2007)
Ultrasonics originated in the domain of physics. The basic properties of sound were described in the classic work of Lord Rayleigh on The Theory of Sound (1877). The discovery of the piezoelectric effect by the French physicists Pierre and Jacques Curie in 1880 provided a way for generating ultrasound waves and became the ...