Ultrasound (US) is a medical diagnostic technique based on the action of ultrasound waves. The images are obtained by processing the ultrasonic beams (echoes) reflected by the body structures.
For a better understanding of the concept of ultrasound we must first define the sound. Sound, is the sensation produced in the organ of the ear by a mechanical wave originated from the vibration of an elastic body and propagated by a material medium. Sound waves are forms of energy transmission and require matter for transmission.
Ultrasound is defined as a series of mechanical waves, usually longitudinal, caused by the vibration of an elastic body (piezoelectric crystal) and propagated by a material medium (body tissues) whose frequency exceeds that of human-audible sound: 20,000 cycles / second or 20 kilohertz (20 KHz).
Types of ultrasound
Medical ultrasound falls into two distinct categories: diagnostic and therapeutic.
- Diagnostic ultrasound is a non-invasive diagnostic technique that is used to produce images within the body. Ultrasound probes, called transducers, produce these sound waves. Most diagnostic ultrasound probes are placed on the skin. However, to optimize the quality of the images, the probes can be placed inside the body through the gastrointestinal tract, the vagina, or the blood vessels. In addition, ultrasound is sometimes used during surgery by placing a sterile probe into the area where the operation is performed.
Diagnostic ultrasound can also be subdivided into anatomical and functional ultrasound.
- Therapeutic ultrasound also uses sound waves above the range of the human ear, but does not produce images. Its objective is to interact with the tissues in the body so that they can be modified or destroyed.
How does it work?
The ultrasound waves are produced by a transducer, which can emit ultrasound waves as well as detect the echoes reflected by the ultrasound. In most cases, the active elements in ultrasound transducers are made of special ceramic glass materials called piezoelectric. These materials are capable of producing sound waves when an electric field passes through them, but they also work in reverse, producing an electric field when they receive a sound wave. When used in an ultrasound scanner, the transducer sends a beam of sound waves into the body. The sound waves are reflected back to the transducer, by the boundaries between the tissues in the path of the beam (eg the limit between fluid and soft tissue, or tissue and bone). When these echoes reach the transducer, electrical signals are generated that are sent to the ultrasound scanner.
Using the speed of sound and the return time of each echo, the scanner calculates the distance between the transducer and the tissue limit. These distances are then used to generate two-dimensional images of tissues and organs. During an ultrasound exam, the technician will apply a gel to the skin. This prevents air pockets from forming between the transducer and the skin, which can block ultrasound waves from entering the body.
Cleaning and maintenance of the ultrasound system
Maintenance should be performed periodically and as necessary. Because this medical equipment contains several circuit boards, extensive diagnostic capabilities for technical service and very complex operating software, it is recommended that only trained personnel take care of the technical service of the system.
Much attention should be paid to the cleaning and maintenance of the ultrasound system and peripherals. Thorough cleaning is important for equipment components because they contain electromechanical devices. If such devices are exposed to an excessive and constant level of dust and humidity, their performance and reliability will decrease.
It is essential to clean the transducers that are used with the ultrasound system. Cleaning procedures vary according to the different types of transducers and the use they are intended for.