How Does an Ultrasound Machine Work

Smita Pandit Mar 12, 2019
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Ultrasound imaging is a non-invasive diagnostic procedure which uses high-frequency sound waves to produce images of the internal organs of the body. This ScienceStruck post provides information on how an ultrasound machine works.
Vscan, a palm-sized ultrasound imaging device developed by GE Healthcare and funded by the National Institute of Biomedical Imaging and Bioengineering (NIBIB), allows physicians to monitor pregnancies, view internal organs, and check for problems associated with blood flow.
The term 'ultrasound' refers to a frequency that is above the range of human hearing.
Ultrasound imaging, which is also known as diagnostic medical sonography, is a non-invasive imaging procedure that involves the use of high-frequency sound waves for diagnostic, as well as therapeutic purposes. It is considered to be safer than X-rays and CT scans, as it doesn't involve the use of ionizing radiation.
An ultrasound machine is a computer-integrated diagnostic tool. It comprises of a transducer probe, CPU, monitor, keyboard with control knobs, disk storage devices, and printer. Its components work collectively for producing images of the internal organs.

Ultrasound Imaging and Reverse Piezoelectric Effect

Piezoelectric crystals are crystals that generate a charge when they are subjected to mechanical stress. The transformation of mechanical energy into electrical energy is referred to as piezoelectric effect. Quartz, barium titanate, lead niobate, lead zirconate titanate, etc., are some of the piezoelectric materials.
In case of an ultrasound, pulsed ultrasound waves are generated with the help of piezoelectric crystals that are placed in a hand-held probe called transducer. When an electric current is applied to the piezoelectric crystal, it induces mechanical stress.
This is referred to as reverse piezoelectric effect. It is the reverse piezoelectric effect that is relied upon for the production of ultrasound waves.
When an electric current is applied to these crystals, it brings about a rapid change in their shape. This causes the crystals to produce sound waves that travel outward. When these sound or pressure waves bounce back and hit the crystals, they emit electric current.
The frequency used for the purpose of ultrasound imaging is within 2 - 15 MHz. There is an inverse relationship between the wavelength and frequency of ultrasound waves. High-frequency ultrasound waves have short wavelength, and low-frequency ultrasound waves have long wavelength.
High frequencies are used for scanning the organs or tissues that are close to the surface. High-frequency waves provide images of high resolution. Though low frequencies waves can penetrate to deeper structures, they provide images of lower resolution.

Components of an Ultrasound Machine

Nowadays, ultrasound machines are readily available, and widely used for diagnostic purposes. Let's find out how ultrasound waves are produced and transmitted via these machines.

Central Processing Unit

The CPU contains power supplies for the transducer probe and the microprocessor, a set of circuits that connect the CPU to the computer.
Its task is to receive the data and provide output by processing the data as per the stored directions. In an ultrasound, the CPU sends electric current to the transducer, and processes the information sent by the processor into 2D or 3D images. These images can be seen on the monitor.

Transducer

The transducer is an integral component of an ultrasound.
The term 'transducer' refers to a device that converts energy from one form to another. This device acts as the transmitter, as well as the receiver. During an ultrasound, a gel is applied on the targeted body part to prevent the sound waves from getting distorted. The probe is moved back and forth over that part of the body.
The application of an electric current to the crystals in the transducer leads to the generation of the ultrasound waves. The reflection of the ultrasound waves occurs at the boundary of different types of tissue. The transducer converts the mechanical energy of the ultrasound waves that bounce back off the targeted organ into an electric current.
The CPU then processes the information regarding the pitch and amplitude of the sound, and the time taken by the ultrasound waves to get reflected on to the transducer for generating 2D or 3D images of the internal organs.

Other Components

➞ The sonogram technician can use the keyboard for adding notes and taking measurements of the image. The transducer pulse controls can be used to vary the duration and frequency of the ultrasound pulses, or change the scan mode.
➞ The processed data from the CPU is turned into an image, which can be seen on the monitor.
➞ The processed data and/or images can be stored on the hard disk along with the patient's medical records.
➞ The ultrasound technician can also select an image, which can be printed by a thermal printer that is connected to the ultrasound.
Ultrasound has various uses in diagnostics, but it has become indispensable for analyzing the fetal development. While the conventional ultrasound provides two-dimensional images for three-dimensional human anatomy, it's now possible to generate 3D and 4D images.
While the 3D scans are still pictures of the embryo in three dimensions, the moving three-dimensional images of the embryo are referred to as 4D scans. Though adverse effects have not been linked to the use of ultrasound, concerns have been raised on account of the possible link between the abuse of ultrasounds and thermal effects of ultrasound waves.
For instance, if the probe is left at one spot for a long period, it could cause the temperature to rise at that spot. To reduce such risks, it is extremely essential that the ultrasound machine is handled by an experienced sonographer.