Ultrasound is a sound wave with a frequency lesser than the frequency audible to humans. However, revolutionary advancements in the diagnostic field implemented the use of ultrasound waves for the diagnosis of various clinical conditions. In this regard, ultrasound scans have been developed for scanning and imaging body organs and detecting possible abnormalities in pathological conditions.
The working principle of ultrasound scanning generally involves the administration of ultrasound waves to the body via a transducer (probe). These waves strike various body parts and bounce back to create echoes. Finally, the echoed waves create a real-time image of the internal organs. Multiple types of ultrasound transducers (probes) are used based on their target organ of imaging and use.
A transducer is a device that produces sound waves and echoes are made when these sound waves bounce off the tissues of the body. The transducer these echoes and it sends them to the computer. The computer uses the echoes to form an image which is called a sonogram. There are different types of transducers used. Let’s have a look at them:
- Real-time transducer
- Special Purpose transducer
Transducers that give real-time imaging of the anatomy and physiology of body organs are called real-time transducers. Real-time ultrasonic images use two basic techniques which are:
- Mechanical Scanning
- Electric Array Scanning
In Mechanical scanning, the pictures are formed in real-time when the transducer is moved by a motor or an electromagnet. There are three types of mechanical real-time instruments. The images formed by mechanical scanning are in sector format. They comprise an area of 45° to 90°.
Oscillating Transducer (Unclosed crystal):
The oscillating transducer touches the patient’s skin, and both the operator and the patient can feel vibrations caused by the moving crystal.
Electric Array Scanning:
In this type of scanning, the transducers are activated electronically to produce an ultrasonic beam to sweep across the patient. These have basically three types:
These are also known as a convex or curved linear probe because the piezoelectric crystal arrangement is curvilinear. This type of probe has a low frequency, and it allows deep penetration. The shape of its beam is convex and becomes wide at the footprints. These probes have frequencies ranging between 2.5 to 7.5 MHz. the sub-type of the curvilinear probe is called the micro-convex which has a smaller footprint and due to this reason, it is used in neonatal and pediatrics.
Uses of Curvilinear Probe:
It is used to examine deeper structures like abdominal structures. It is also used for superficial organ scannings like large breasts and large thyroid.
This type consists of a number of small rectangular transducer elements arranged in a line. The linear probe is a high-frequency probe. The piezoelectric crystal arrangement of the linear probe is linear. The beam shape of the linear probe is rectangular, and it has a good near-field resolution. The 2D imaging linear transducer has a wide footprint and it has a frequency ranging from 2.5 MHz to 12 MHz. It is the best probe to view the superficial structures. It provides information about poor depth organs, and it has low penetration power.
Uses of Linear Probe:
It is used for viewing:
- Vascular examination
- Blood Vessel visualization
- Musculoskeletal – tendons, bones, muscles
- Thyroid Gland
Linear Probe with 3D Imaging:
3D imaging linear transducer has a wide footprint, and it has a frequency ranging between 7.5 MHz to 11 MHz. It is used for viewing breast and thyroid glands.
They are also known as phased array transducers. Transducers are arranged in such a manner that will produce an image in sector form. It is the simplest type of electric array scanning. This type of probe has a small footprint and low frequency ranging from 2 MHz to 7.5 MHz. The footprint of this probe is small, and its beam point is narrow, but it will expand as it will move deeper. It has a triangular beam shape. These transducers have good depth, penetration, and better resolution information.
Uses of Sector Probe:
It is used for cardiac imaging, transesophageal imaging, abdomen, lungs, and pleura between ribs and small places. It is also used for brain examinations.
Special Purpose Transducers:
This permits unorthodox routes of access to be employed and unusual procedures to be carried out. There are different types of Special Purpose transducers. They are:
These types of transducers are inserted inside the normal body without puncturing the skin.
Transesophageal (TEE) Probe:
As the footprint of the Transesophageal probe is small therefore it is used for internal examinations. It is used to get a better picture of the heart when it is passed through the esophagus. It has a frequency ranging from 3 MHz to 10 MHz. Multiple frequency transducers are used for high resolution and better anatomical details.
Endo cavitary Probes:
These probes provide the opportunity for physicians to perform internal examinations of the patients. The footprint of Endo cavitary probes is small. Their frequency ranges from 3.5 MHz to11.5 MHz. The endo cavitary transducers include endovaginal and endorectal transducers. They are used to view the uterus and rectum.
For the scanning of the rectum part, the best suitable transducer is of 5 MHz or 7.5 MHz frequency. This probe is used for prostate and rectal wall scanning.
In this scanning, mechanical or electronically moved transducers can be used. it has a frequency ranging from 5 MHz to 7.5 MHz. it is used for scanning ovaries and the uterus.
Ultrasonic Transducers Applications:
They can locate the target inside the human body. They are also utilized in the diagnostic testing and testing of the internal organs. They are used for checkups of the heart, eyes, and uterus.
So, this was all about ultrasound transducers, and hopefully, you found it significantly informative. Ultrasound is a non-invasive, painless, and impressively reliable diagnostic tool that is used for the detection of various pathologies by providing a complete and detailed picture of internal bodily organs. Along with the diagnosis, ultrasounds also assist in disease prognosis and monitoring of the therapy, thereby emerging as a robust clinical tool.
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