What is ultrasound? How is the ultrasonic system designed to produce detection methods and ultrasound?

Method of producing and detecting ultrasound:

Ultrasonic systems are designed to produce ultrasound. At present, the technology used in modern technology to create and detect ultrasound waves is the piezoelectric effect. This system consists of a generator for generating electrical signals, the necessary amplifiers, a transducer, other electronic processing devices, and a display unit) Several types of devices can be used to generate ultrasonic energy. At present, ultrasound transducers are piezoelectric resonators. Sometimes called a crystal resonator or crystal, an ac potential difference of resonant frequency is applied across the two surfaces of the quartz crystal to make it vibrate at its natural frequency. And that is done with the help of oscillatory electronic circuits. Therefore, a very thin metal coating is applied on both sides of the sheet to provide direct electrical connection.

 

In addition to quartz crystal, synthetic piezoelectric materials such as barium titanate, lead zirconate titanate crystal are also used in special cases. Quartz crystals are commonly used for frequencies up to 15 MHz.The term ‘ultrasound’ is applied to all acoustic energy with frequencies above the human audible frequency range (20,000 Hz or 20 kHz). Typical diagnostic sonography scanners operate in the 2-18 MHz frequency range, hundreds of times above the audible limit.

 

Ultrasonography is widely used in medicine for both diagnosis and treatment. A sonographer performs scanning for diagnostic purposes. Sonographers typically use a hand-held probe, which is held over the patient and moved. This probe is called a transducer. A water-based gel is used to couple the ultrasound between the transducer and the patient. Sonography is useful for imaging the soft tissues of the body. Structures near the surface such as muscles, tendons, testes, breast and brain are imaged at higher frequencies (7–18 MHz). Deeper structures such as the liver and kidney are imaged at lower frequencies.

 

Biomedical Instrument The ultrasound transducer is the main imaging part of the ultrasound machine. The transducer produces sound waves and receives the echo. So to speak, it is the mouth and ears of the ultrasound machine. A transducer is a piezoelectric transducer. When an electric current from the oscillator is applied to the piezoelectric crystal, it rapidly changes shape or vibrates the crystal, producing sound waves that travel outward.  

 

Use of echo ultrasound The use of pulse echo ultrasound in ophthalmology is very effective for the diagnosis of retinal detachments, intraocular tumors, vitreous opacities, orbital tumors and lens dislocation.It helps in measuring axial length in patients with progressive myopia, locating intraocular objects and removing non-magnetic external objects. Echo-opthalmoscopy uses a 7.5–15 MHz pencil type transducer.

The transmitted pulse is of very small amplitude, ie in the nanosecond range. When anterior-posterior examination is performed along the optical axis in normal eyes, echoes will be obtained from the following structures. eyelid surface (corresponding to the zero marker);corneal surface; Anterior lens capsule, posterior lens capsule, posterior wall of eyeball (appears as a complex echo from a unit formed by retina, choroid and sclera) and retrobulbur fat. The depth and relative distance of each formation shown on the display using the marker distance on the trace can be read directly from the screen or taken as a photograph.

 

Principle of M-scan display: As in A-scan mode, each transmitted pulse triggers a sweep of the oscilloscope. But the received pulses are used only to brighten the trace without controlling the vertical deflection. Quiescent brightness is set below the visibility threshold, so that only echoes appear as bright dots. They are proportional to the intensity of each echo and the transducer is held stationary for the M-scan seen, so that the dot and movement along the sweep represent the movement of the received target. If photographic paper is passed slowly over the oscilloscope, a dot representing each target will trace a line on the paper. A stationary target will trace a straight line. On the other hand, a moving target will trace its movement pattern with respect to time. A light-pen recorder (in which the intensity of the light source can be controlled) can be used instead of an oscilloscope to produce a chart record of the movement of the echoes over time.

With the help of ultrasound, it is possible to distinguish between different soft tissues and measure the movement of the structure of the heart. That is why ultrasound is very useful for analysis method in cardiology. An important point in this case is that there is usually no interference by echoes from other body structures. Because the heart is surrounded by lungs, which are literally air sacs. This helps a lot in interpretation.The heart has several acoustic interfaces; Such as- atrial and ventricular walls, inter-atrial and inter-ventricular septa and different types of valves. The movement and position of each interface can be measured by reflected ultrasound. Echoes from these walls and valves are predictable, since the heart’s components move in a known manner.  The echocardiogram is very useful in interpreting mitral valve movement over time. Valve movement is measured by echo displacement per unit time during diastole. Another use of echocardiography is fluid detection. The presence of fluid within the pericardium can be diagnosed with an echocardiogram.

Doppler sonography (Doppler sonography): Doppler ultrasound, based on the Doppler effect. When the ultrasound wave is reflected by a moving object, the frequency of the echo changes. If the object moves towards the transducer, the frequency will increase and if it moves away from the transducer, the frequency will decrease. How much the frequency changes depends on how fast the object is moving. Doppler measures changes in the frequency of ultrasound echoes to calculate how fast an object is moving. This ultrasound is mainly used to measure the rate of blood flow through the heart and major arteries and also to detect any blockages in these arteries. To determine if it is blocked by disease or tumor. Doppler sonography can determine and visualize whether blood flow is moving towards or against the probe and its relative velocity. It is particularly useful in cardiovascular studies (sonography of blood vessels and heart). Doppler data is displayed on a graph using spectral doppler or color doppler (directional doppler).Or display as an image using Power Doppler (Non directional Doppler). A Doppler shift is within the audible range and is often presented audibly using stereo speakers.