A history of ultrasound physics and the properties of the transducer - Research Paper Example

? A history of ultrasound physics and the properties of the transducer Ipek J. Batca PHYS101 Prof. J. Bigos 02 January 2012 Abstract Transducers act as both a transmitter and a receiver of ultrasound and are capable of producing beams that are in turn directed in a variety of ways of improving the quality of the images that are seen on the screen. The main component of the transducer is made from a special piezoelectric material, which implies that they are capable of converting one form of energy to another; for instance, electrical energy can be converted to mechanical energy and vice-versa. Prior to the second World War, sonar, which is the technique of transmitting waves of sound through water and observing the echoes that return to characterize the objects that are submerged, was an inspiration to the pioneers of ultrasound investigators in exploring ways and in turn applying the medical diagnosis concepts. This paper will highlight the history of ultrasound and discuss the properties of transducers. History of ultrasound According to Orenstein, (2008) Pythagoras, popular for his theory about right-angled triangles was the pioneer of ultrasound, since he invented the sonometer, which was used to study musical sounds. Boethius (c. 480-c.525) was the first to give comparison between sound waves to waves that were produced when a pebble was dropped into calm water. Pierre Curie, a French physicist discovered piezoelectricity in 1877, the moment that ultrasound was conceived. Later on, as Orenstein continues to assert, sonographic imaging was developed by French professor and physicist Paul Lavengin. Many scientists had the desire to see inside the human body and in turn developed probes and scopes for diagnosis and treatment during the late 19th and early 20th centuries. For instance, the discovery of X-rays by William Conrad in 1865 played an important role in the history of ultrasound. Moreover, in 1912, when the Titanic sank while on its maiden voyage made people to be curious in detecting submerged substances. Like many other technological advances, ultrasound also owes its development to the World War. Lavengin was called upon by the French government to develop an object that was able to detect the sub marines of the enemy during the World War One. The device he invented applied the piezoelectric effect he had learned as Curies’ student (Orenstein, 2008). The transducer is one of the most critical componenets of any diagnostic ultrasound system. There exists various types of ultrasound transducers that can be chosen prior to performing an ultrasound investigation, therefore, much attention should be accorded towards choosing the most suitable transducer for the ultrasound application (Gibbs, Cole, & Sassano, 2009 p27). However, Lavengin did not complete the device he developed in 1917 so that it could be used during the First World War, but it indeed formed the basis of sonar detection that was developed in the World War II (Orenstein, 2008). In 1928, Sergei Sokolov, a Russian physicist made important suggestions that saw ultrasound being used for industrial purposes that included detecting flaws in metallic devices. Ultrasound is a new aspect in the field of medicine. For instance, in the 1920s and the 1930s, ultrasound was used by members of European football clubs as a physical therapy. Additionally, as reported by Orenstein, ultrasound was utilized in the sterilization of vaccines as well as for cancer therapy in conjunction with radiation therapy. Subsequently, in 1948, other ultrasound pioneers such as Douglas Howry subjected his efforts towards developing a B-mode equipment that compared pathology to cross-sectional anatomy. The late 60s and early 70s was the period of sonic boom. A 2D echo was pioneered by Klaus Bom. Don Baker, John Reid and Dennis Watkins were able to develop a pulsed Doppler in 1966, which was able to detect the flow of blood from the different corners of the heart. Real-time ultrasound was developed in the early 1980s. In this regard, ultrasound became more popular and believable. In the 1990s, ultrasound was developed to 3D and 4D that could be interpreted easily by the public (Orenstein, 2008). Properties of the Transducer Following the discovery of ultrasound devices such as the transducer, the primary requirement was to utilize suitable materials as substrates. In this regard, the main requirement of a transducer are; physical housing assembly, Electrical connections, Piezoelectric element, Backing material, Acoustic lens and Impedance matching layer. The physical housing is composed of all the individual components that include the crystal, electrodes, matching layer and backing material. Electrical connections; this encompasses the formation of two electrical connections on the front and the rear faces of the crystal by plating an ultra-thin layer of gold or silver on the respective surfaces. The electrodes are therefore connected to the ultrasound machine, which in turn disseminate the short burst of electrical pulses to excite the crystal, and via the piezoelectric energy, an ultrasound energy pulse is generated. Piezoelectric element; Transducers, as discussed earlier, primarily operates on the effect of piezoelectric that was discovered by Jacques and Pierre Curie in 1880 (Gibbs, Cole, & Sassano, 2009 p29). The piezoelectric property can only exist if the material is anisotropic. This implies that its properties vary with direction in relation to the internal structure. Important properties are the velocity of the wave, piezoelectric coupling, temperature effects, diffraction and the attenuation and the degree of the generation of unwanted bulk-wave (Morgan, 2007 p7). Jaques and Curie discovered that there are certain crystalline minerals that when subjected to a mechanical force, they became polarized electrically, meaning that they generated voltages (Gibbs, Cole, & Sassano, 2009 p29). The Backing Material; when a crystal is subjected towards a short pulse of electricity, it vibrates in all directions. Therefore, in order to eliminate the back face vibrations, and in order to control the length of front face vibrations, a backing material, which primarily consists of tungestein powder and plastic or epoxy resin is attached to the piezoelectric crystals at the back face. Acoustic lens plays the role of improving the resolution of the image by reducing the transducer’s beam width. The lateral resolution is determined by the width of beam. Therefore, the acoustic lens is an important property of the transducer. Impedance matching layers is sandwitched between the piezoelectric crystals and the patient and it plays an integral role that outrightly affects the transducer’s sensitivity. For instance, the ability of the ultrasound system to find out small reflected echoes(Gibbs, Cole, & Sassano, 2009 p30). Conclusion The transducer plays an integral role in the system of ultrasound instrumentation. The transducer, as discussed in this paper, incorporates the piezoelectric element that is able to convert electrical signals into mechanical energy and vice-versa. Various factors that include mechanical and electrical construction as well as the external electrical and mechanical load conditions greatly influence the characteristic of the transducer. The mechanical aspect of the transducer involves such parameters as the surface area radiation, mechanical damping, housing, as well as the electrical connections. The transducer has witnessed massive evolution since it was invented up to the current 3D or 4D statuses, and it plays significant roles in ultrasound. References Gibbs, V., Cole, D., & Sassano, A. (2009). Ultrasound Physics and Technology: How, Why and When. Elsevier Limited. Morgan, D. (2007). Surface Acoustic Wave Filters: With Application to Electronic Communications and Digital Processing. (2nd Edition ed.). Elsevier Limited. Orenstein, B. W. (2008). Ultrasound History. Radiology Today , IX (24), 28-29. Read More