UltrasoundPhysics and the Properties of the Transducer
UltrasoundPhysics and the Properties of the Transducer
Ultrasoundphysics dates back to over a century ago. It allows for thestructural components of tissues to be visualized through anon-invasive process. The process of ultra-sonication is acollaborative approach that includes different stakeholders. Eventhough the physics of ultrasound is sophisticated, its simplicity canbe seen in the clinical context. Ultrasound technology was initiallydeveloped by non-medical experts before it was adopted into themedical field (Geria, Raio, and Tayal, 2015). The continualmodification of ultrasound has contributed in increasing thesignificance of ultrasound physics, e.g. the adoption of thetransducer.
Thehistory of ultrasound physics
LazzaroSpallanzani was the first person to study ultrasound physics. Hedefined the concept of echolocation, as the process whereby a soundis produced that later on bounces back in the form of an echo afterhitting an object. The echo is used to determination location, size,and the structure of the object. This method is used by bats togather specific information while flying. Jean-Daniel Colladondevised one of the earliest ultrasound transducers by placing achurch bell under the water in an experiment conducted in the year1826 (Tsung, 2015). He was able to utilize this set-up to calculatehow fast sound travels in the water. He eventually proved that soundmovement in the air was much slower as compared to sound movement inthe water.
Inthe year 1880, Jacques and Pierre Curie discovered piezoelectriceffect, whereby mechanical stress led to the creation of an electriccharge. In the year 1915, Paul Langevin invented the hydrophone. Itwas the first transducer developed following the sinking of the shipTitanic in 1912 (Tsung, 2015). This invention was vital in helpingdetect icebergs, which caused the ship to sink. Later on, hydrophonetechnology was adopted in warfare to detect rival submarines. It waswidely used in World War 1. Paul Langevin also aided in thediscovered of animal tissue disruption, through heat generation inthe late 1920s. This discovery made it possible to treat diseasessuch as Parkinson disease and rheumatic arthritis.
Researchon the feasibility of using ultrasound in the medical field was notedin 1942 through the work of Karl Dussik. This followed a lengthyperiod of research from 1915 to 1942. Karl was able to use thistechnology in the diagnosis of brain tumors. In the year 1948, aprotocol was established detailing the application of ultrasound indiagnosing gallstones. George Ludwig was able to demonstrate this.Later along, other foreign objects could also be detected throughthis technology.
Inthe year 1951, Douglas Howry and Joseph Holmes developed anultrasound scanner (B-mode linear compound). Their primary objectivewas to abolish ‘unrealistic’ echoes. This invention improvedimaging, offering a clear distinction between different structuresand tissues.
Inthe year 1953, the diagnosis of mitral stenosis was further enhancedthrough the ability to perform an echocardiogram as outlined by IngeEdler and Carl Hertz. In the same year, John Wild and John Reid wereable to produce real-time images showing human breast cancer growth.In 1955, the Doppler Effect was first used in the medical applicationin monitoring the heart and blood vessels’ pulsation rate. This wasfollowed by the invention of the Pan Scanner in 1957 with thecapability of the transducer rotating around the patient in theabsence of a non-aqueous environment (Tsung, 2015).
Inthe year 1958, Ian Donald pioneered the OB-GYN ultrasound that wasable to detect Cysts and abdominal tumors. The method could alsodetect and reveal twin pregnancies. In 1962, another significantmilestone was realized the first invention of a transducer that wasable to be positioned by the hand was developed by Joseph Holmes andhis colleagues. The year 1963 saw the launch of the B-Mode scanner inthe USA, thereby initiating a period of the most popular ultrasoundscanners. In 1965, a real-time imaging scanner was invented by WalterKraus and Richard Soldner. The Doppler technique was put into furtheraction in 1966 where it was used in determining the flow of blood tothe heart. This was an invention by Don Baker, John Reid and DennisWatkins (Tsung, 2015). Detection of the peripheral vascular diseaseswas achieved through the Doppler imaging, invented by Gene Strandnessin 1967.
Inthe year 1972, the world first linear array scanner referred to asthe multi-scan system was developed by Paul Hugenholtz and OrganonTeknika. In the year 1973, a gray scale technology was developed byGeorge Kosoff which had the capability to differentiate betweentextures. One of the most outstanding developments in sonography wasdeveloped in the year 1973 by James Griffith and Walter Henry. Theywere able to develop an oscillating real-time scanning device (Tsung,2015). In 1974, the first duplex pulsed Doppler scanner with thecapabilities of 2D-imaging was developed by Frank Barber, John Reid,and Don Baker. In the year 1976, digital converters were invented byAlbert Waxman, which phased out the analog systems.
In1985, the possibility of a real-time color flow imaging was realizedby Chihiro Kasai and other colleagues from Japan. In 1987, there weredevelopments in the field of cardiology through the development ofthree-dimensional volumetric structure with real-time capabilities.Olaf von Ramm initiated this invention. In the year 1989, the firstcommercial 3D scanner known as Combison was introduced into themarket. Later that year, Daniel Lichtenstein pioneered ultrasoundinto the intensive care unit.
In1994, there was the development of state of the art medical imagingequipment with high-resolution capabilities. This was developed byOlaf von Ramm and Stephen William Smith. In 1996, there wasindependent research on fetal echocardiography through the use ofcardiac sonography. The main aim was to abolish the motion artifactsthat were familiar with 3D techniques (Tsung, 2015).
Propertiesof the transducer
Thegeneration of ultrasound waves is achieved through the use of atransducer. They facilitate the conversion of electric signals intoultrasonic energy for transmission into the tissues. The energy thatis reflected back from the tissue is converted into an electricalsignal. One of the vital components is the piezoelectric crystalelement which comprises of lead zirconate titanate. A thin conductingfilm coats the front and back surfaces. This ensures an appropriatecontact with the electrodes responsible for supplying the electricfields to the crystals. Some dipoles combine to form the crystals.The dipoles have a positive and a negative end which realignfollowing the passage of an electric current. This changes thedimension of the crystal inhibiting further current flow (Mattiat,2013).
Thevoltage between the plating electrodes leads to variations in theshape of the crystal. The crystal vibrates following the passage ofhigh-frequency energy. This vibration must be stopped withinmicroseconds. This is because there should be the immediate readinessof the transducer to receive echoes from the interface of the tissues(Boulmé et al., 2015). There is a reflection of the echoes towardsthe transducer as the sound pulse goes through the body. The energyreceived by the transducer emanates from the echoes hence the crystalelement becomes physically compressed. The orientation of the dipolesis altered thus inducing a voltage between the electrodes.Amplification of the voltage causes it to be used as an ultrasonicsignal for display. The transducer also has what’s referred to asthe Q factor. It determines the persistence and purity of the sound.The production of a pure sound is linked to the high Q transducer,while the production of a complete spectrum of sound is related tothe low Q transducer (Linder et al., 2016). Changing the features ofthe damping block can be used to control the Q factor.
Inconclusion, there is no doubt about the significant contribution ofultrasound physics to the society at large. As noted in thehistorical context, a lot of stakeholders have been involved intrying to diversify the use of ultrasound physics to impactpositively on the society.
Boulmé,A., Gross, D., Heller, J., & Certon, D. (2015). Normal ModeTheory Applied to Linear Arrays of Capacitive MicromachinedUltrasonic Transducers. Physics Procedia, 70, 992-996.
Geria,R. N., Raio, C. C., & Tayal, V. (2015). Point-of-care ultrasound:not a stethoscope—a separate clinical entity. Journal of Ultrasoundin Medicine, 34(1), 172-173.
Linder,H., Malo, M. K., Liukkonen, J., Jurvelin, J. S., & Töyräs, J.(2016). Phased-array ultrasound technology enhances accuracy of dualfrequency ultrasound measurements–towards improved ultrasound bonediagnostics. Journal of medical engineering & technology, 1-5.
Mattiat,O. E. (2013). Ultrasonic transducer materials. Springer Science &Business Media.
Tsung,J. (2015). History of Ultrasound and Technological Advances. NewYork, USA.