Relevant Terminologies Lecture 3 PDF

Relevant Terminologies Prof. Feliz Niña G. Perez, RRT, MSRT  Diagnostic sonography (ultrasonography) is an ultrasound-based diagnostic imaging technique used to visualize subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or l...

Relevant Terminologies Prof. Feliz Niña G. Perez, RRT, MSRT  Diagnostic sonography (ultrasonography) is an ultrasound-based diagnostic imaging technique used to visualize subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions. Sonography is effective for imaging soft tissues of the body.  During an ultrasound procedure, the ultrasound machine generates images by sending high-frequency sound waves into the body. These sound waves bounce off tissues and organs inside the body, creating echoes. The ultrasound machine captures these echoes and converts them into electrical signals. These signals are then processed and used to generate images of the internal structures.  Although discovered several years before the X-ray (1883), the ultrasound is a much later found application in medicine. The application of ultrasound in medicine began in fifties of last century. From the clinical aspect the ultrasound possesses the priceless significance because of its noninvasive, good visualization characteristics and relatively easy management  Transmission technology is based on distinguishing the tissues with different absorbance of ultrasound. Due to uneven absorption of ultrasound images provides internal structure that consists of a mosaic of lighter and darker places. This technology is now abandoned. It uses two aligned transducers located in opposite sides of the part. One transducer acts as transmitter and the other as receiver. Used in industrial areas/aspects.  Reflection technology (echo) registers the pulse is reflected from the boundary of two tissues with different acoustic resistance. A sound wave is typically produced by a piezoelectric transducer encased in a probe. Strong, short electrical pulses from the ultrasound machine make the transducer ring at the desired frequency.  The frequencies can be anywhere between 2 and 18 MHz. The sound is focused either by the shape of the transducer, a lens in front of the transducer, or a complex set of control pulses from the ultrasound scanner machine. Wave Equation The wave equation is significant in understanding the behaviour of waves in different mediums. The basic mathematics of ultrasound is the wave equation, which describes the behavior of sound waves as they propagate through tissue. The wave equation is a mathematical formula that describes the behaviour of waves in different mediums. It is used to predict the propagation of waves, such as sound waves, light waves, and electromagnetic waves. The equation is based on the principles of wave mechanics, which states that waves can be described by their amplitude, wavelength, and frequency. Types of Ultrasonic Waves Longitudinal ultrasonic waves - the direction of propagation of which coincides with the direction of displacement and velocities of the particles of the medium. Transverse ultrasonic waves - waves propagating in a direction perpendicular to the plane in which the directions of displacements and velocities of body particles lie, the same as shear waves  Surface (Rayleigh) ultrasonic waves have an elliptical motion of particles and propagate over the surface of the material. Their speed is approximately 90% of the shear wave propagation speed, and their penetration deep into the material is equal to approximately one wavelength. Ultrasound intensity and power Sound intensity is the time-average energy carried by a sound wave through a unit area perpendicular to the direction of wave propagation, per unit time. For periodic sound, averaging is performed either over a period of time larger than the period or over an integer number of periods. Ultrasound intensity is a value that expresses the power of the acoustic field at a point Sound power is the energy transmitted by a sound wave through the considered surface per unit of time. Distinguish between the instantaneous value of the ultrasound power and the average over a period or over a long time. Of greatest interest is the average value of the ultrasound power per unit area, the so-called average specific sound power, or sound intensity Ultrasound attenuation One of the main characteristics of ultrasound is its attenuation. Attenuation of ultrasound is the decrease in the amplitude and, therefore, the intensity of the sound wave as it propagates. The attenuation of ultrasound occurs for a number of reasons. The main ones are: decrease in wave amplitude with distance from the source, due to the shape and wave dimensions of the source; scattering of ultrasound by inhomogeneities of the medium, as a result of which the energy flux in the initial direction of propagation decreases; absorption of ultrasound, i.e. irreversible transfer of the energy of a sound wave into other forms, in particular into heat Ultrasound Emitters Ultrasound emitters are devices used to excite ultrasonic vibrations and waves in gaseous, liquid, and solid media. Ultrasound emitters convert energy of some other kind to the energy of the sound field. The most widely used ultrasound emitters are electro- acoustic transducers. In the overwhelming majority of ultrasound emitters of this type, namely in piezoelectric transducers, magnetostrictive transducers, electrodynamic emitters, electromagnetic and electrostatic emitters, electrical energy is converted into vibration energy of some solid body (emitting plate, rod, diaphragm, etc.), which emits acoustic waves into the environment. Piezoelectricity was co-discovered by Pierre Curie (1859- 1906) and his brother Jacques (1856-1941) in the period 1878-1880. The 'piezo' suffix of piezoelectric was formed from the Ancient Greek word πιεζω (piezo) meaning "to press“ piezoelectricity is the process of using crystals to convert mechanical energy into electrical energy or vice versa. Piezoelectric Crystals Piezoelectric crystals have unique electromechanical properties. When an electric current is applied to a piezoelectric crystal, it starts to vibrate and these vibrations generate sound waves with frequencies between 1.5 and 8 MHz. Electrical energy is converted by piezoelectric crystals into mechanical energy which generates ultrasound waves. Echoes return stimulating these crystals and these produce electrical signals returning to the machine. These electrical signals are converted into the grey scale imaging we see. quartz, silicon dioxide, lead zirconate and lead titanate Piezoelectric Effect converts kinetic or mechanical energy, due to crystal deformation, into electrical energy. This is how ultrasound transducers receive the sound waves.  Piezoelectric materials exhibit both a direct and a reverse piezoelectric effect. The direct effect produces an electrical charge when a mechanical vibration or shock is applied to the material, while the reverse effect creates a mechanical vibration or shock when electricity is applied. Purpose of Piezoelectric crystal used in Ultrasound devices When an electric current is applied to a piezoelectric crystal, it starts to vibrate and these vibrations generate sound waves with frequencies between 1.5 and 8 MHz (i.e ultrasound). Thus, piezoelectric crystals can convert electric currents into ultrasound waves.  Piezoelectric materials can be made to vibrate via the converse piezoelectric effect to the point where they start emitting ultrasonic waves. At the same time, they can register mechanical energy such as sound and convert it into electrical energy by means of the direct piezoelectric effect. Devices that convert one energy type into another via one or both piezoelectric effects, are known as piezoelectric transducers. These devices enable a wide range of ultrasound technologies.  BASIC TERMINOLOGIES USED IN SONOGRAPHY  Echogenicity - the ability to create an ultrasound echo; the ability of a tissue to reflect sound waves Anechoic - being echo-free or without echoes(e.g. fluid-filled cyst, ascites) Hyperechoic/ echogenic -producing echoes of higher amplitude than normal for the surrounding medium  Isoechoic - areas which have similar echogenicity to each other Hypoechoic - producing echoes of lower amplitude than the surrounding medium Sonolucent - allowing passage of ultrasound waves without echoes Heterogenous - mixed echoic pattern within plaque areas of sonolucence Homogenous -uniform plaque texture Acoustic window - is the area defined by the pathway of the ultrasound beam between the transducer and the acoustic reflector. Acoustic Shadowing/ posterior shadowing - is characterised by a signal void behind structures that strongly absorb or reflect ultrasonic waves. This happens most frequently with solid structures. Acoustic Enhancement/ Posterior enhancement - refers to the increased echoes deep to structures that transmit sound exceptionally well. This is characteristic of fluid filled structures such as cysts, the urinary bladder and the gallbladder.