In this blog post, we will explain the different ultrasound transducer types and determine the types of examinations you can use them for. In the end, we will offer some good points you should keep in mind when you are purchasing transducers.
Before we get started, let’s answer the question. – What is an ultrasound transducer and what is it good for?
An ultrasound transducer, also called a probe, is a device that produces sound waves that bounce off body tissues and make echoes. The transducer also receives the echoes and sends them to a computer that uses them to create an image called sonogram.
Hereby, an ultrasound transducer is a very important part of the ultrasound machine and a core part of the signal transmission chain for image reconstruction. Moreover, it is the fundamental determinant of image quality.
The essential element of each ultrasound transducer is a piezoelectric crystal. It serves to generate as well as receive ultrasound waves. Sadly, the medical imaging industry has been using the same piezoelectric material for over 40 years.
But what happened a few years ago?
Luckily, a new type of crystal material and ultrasound probe technology appeared. That meant a dramatic improvement in image quality. You can read more about the technology in our blog post – Ultrasound Probe Technology.
Ultrasound Transducer Types
You can find ultrasound transducers in different shapes, sizes, and with diverse features. That is because you need different specifications for maintaining image quality across different parts of the body.
Transducers can be either passed over the surface of the body – external transducers or can be inserted into an orifice, such as the rectum or vagina – these are internal transducers.
Any more differences?
The ultrasound transducers differ in construction based on:
- Piezoelectric crystal arrangement
- Aperture (footprint)
Below we list the three most common ultrasound transducer types – linear, convex (standard or micro-convex), and phased array. Furthermore, we have included other transducers that are available on the market and can be found in our warehouse.
So, what features are typical for the linear transducer?
Firstly, the piezoelectric crystal arrangement is linear, the shape of the beam is rectangular, and the near-field resolution is good.
The footprint, frequency, and applications of the linear transducer depend on whether the product is for 2D or 3D imaging.
The linear transducer for 2D imaging has a wide footprint and its central frequency is 2.5Mhz – 12Mhz. You can use this transducer for various applications, such as:
- Vascular examination
- Venipuncture, blood vessel visualization
- Tendon, arthrogenous
- Intraoperative, laparoscopy
- The thickness measurement of body fat and musculus for daily health care check and locomotive syndrome check
- Photoacoustic imaging, ultrasonic velocity change imaging
The linear transducer for 3D imaging has a wide footprint and a central frequency of 7.5Mhz – 11Mhz.
What can you use this transducer for?
- Arteria carotis of vascular application
The convex ultrasound transducer type is also called the curved transducer because the piezoelectric crystal arrangement is curvilinear.
Moreover, the beam shape is convex and the transducer is good for in-depth examinations, even though the image resolution decreases when the depth increases.
The footprint, frequency, and applications also depend on whether the product is for 2D or 3D imaging.
The convex transducer for 2D imaging has a wide footprint and its central frequency is 2.5MHz – 7.5MHz.
You can use it for:
- Abdominal examinations
- Transvaginal and transrectal examinations
- Diagnosis of organs
The convex transducer for 3D imaging has a wide field of view and a central frequency of 3.5MHz – 6.5MHz. You can use it for abdominal examinations.
In addition to the convex transducers, there is a subtype called micro convex. It has a much smaller footprint and typically, physicians would use it in neonatal and paediatrics applications.
Phased Array Transducers
This transducer is named after the piezoelectric crystal arrangement which is called phased-array and it is the most commonly used crystal.
Phased Array transducer has a small footprint and low frequency (its central frequency is 2Mhz – 7.5Mhz).
The beam point is narrow but it expands depending on the applied frequency. Furthermore, the beam shape is almost triangular and the near-field resolution is poor.
What for can you use the Phased Array transducer?
- Cardiac examinations, including Transesophagealexaminations
- Abdominal examinations
- Brain examinations
Other Ultrasound Transducer Types
We are not done, yet.
There are more ultrasound transducer types on the market. Such as:
Pencil transducers, also called CW Doppler probes, are utilized to measure blood flow and speed of sound in blood. This probe has a small footprint and uses low frequency (typically 2Mhz– 8Mhz).
The next ultrasound transducer type is endocavitary. These probes provide you with the opportunity to perform internal examinations of the patient. Therefore, they are designed to fit in specific body orifices. The endocavitary transducers include endovaginal, endorectal, and endocavity transducers. Typically, they have small footprints and the frequency varies in the range of 3.5Mhz – 11.5Mhz.
Furthermore, there is a transesophageal (TEE) probe. As well as the previously mentioned probes, it has a small footprint and is used for internal examinations. It is often employed in cardiology to obtain a better image of the heart through the oesophagus. The frequency is middle, in the range of 3Mhz – 10Mhz.
Moreover, there are several probes designed for surgical use, for instance – laparoscopic probes.
Tips You Should Follow When Buying an Ultrasound Transducer
Now, you should be aware of the most common ultrasound transducer types. And we have a few tips that you should follow when purchasing ultrasound transducers:
- Make sure to double check that the probe you are about to buy is compatible with the system you own – you can use a probe guide, or ask our sales team.
- Penetration depth is better at a low frequency (between 2.5 and 7.5Mhz) but a disadvantage of the low frequency is a lower image quality
- The higher the frequency (above 7.5Mhz), the lower is the depth of penetration, however, you get better quality images close to the surface (7.5MHz = 20 cm).
- A black line on the screen of the ultrasound system will most likely mean that the transducer has a dead crystal inside.
- A shadow on the screen of the ultrasound system could indicate a weak crystal inside the transducer that does not produce the necessary vibration.
How Should You Treat Your Transducer?
Finally, remember that the transducer is a very important, and also a very expensive element of an ultrasound. Therefore, after you have purchased your transducer, you should use it with caution, which means:
- Do not throw, drop, or knock the transducer
- Be careful not to damage the duct of the transducer
- Wipe the gel from the transducer after each use
- Do not sluice with alcohol-based confections
To learn more about how to protect your ultrasound probes and what the most common defects are, check our blog post that explains this topic in more depth.
We hope that after reading this article, you have a clear image of ultrasound transducer types. And that you will be more prepared the next time you are purchasing probes.
If you have any more questions about transducers, do not hesitate to contact our sales department at firstname.lastname@example.org or via phone +45 96 886 500.
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