What are the commonly used transducers in musculoskeletal Ultrasound?
In musculoskeletal ultrasound, various transducers can be used depending on the specific area being examined and the depth of the structures being imaged. Here are some commonly used transducers in musculoskeletal ultrasound:
- Linear array transducer: This transducer has a linear shape and is often used for superficial structures and tendons. It provides high-resolution images and is suitable for evaluating superficial joints, tendons, ligaments, and muscles.
- Curvilinear array transducer: This transducer has a curved shape and is commonly used for imaging larger and deeper structures such as deeper muscles, joints, and organs. It provides a wider field of view but with slightly lower resolution compared to the linear array transducer.
- Phased array transducer: This transducer uses multiple small elements to create and steer ultrasound beams electronically. It is often used for imaging deep structures, such as the shoulder joint, where the beam needs to penetrate through multiple layers of tissue.
- High-frequency transducer: These transducers operate at higher frequencies, typically between 10-18 MHz, and provide excellent resolution for superficial structures. They are commonly used for imaging tendons, ligaments, and small joints.
- Microconvex transducer: This transducer has a small convex shape and is specifically designed for imaging small joints and areas with limited access, such as the hand and foot. It provides good resolution and can capture detailed images in small spaces.
- Intraoperative transducer: These transducers are designed for use during surgical procedures. They are often smaller in size and more maneuverable to allow imaging in the operating room environment.
- The transducer frequency is one important determinant of image quality.
- The higher the frequency, the greater the spatial resolution of the images and the lower the degree of tissue penetration.
- It is important to select the transducer with the highest frequency that still allows penetration to the depth of the structure being imaged.
- Linear probes are preferable to curved probes for musculoskeletal US because the ultrasound waves are propagated parallel to the transducer surface, limiting artifacts during evaluation of linear structures such as tendons.
The most Commonly used transducers in musculoskeletal ultrasound are the below
- Highfrequency (15-7 MHz), smallfootprint, linear array transducer, also called a “hockey stick” transducer – The compact or “hockey stick” linear transducer is ideally suited for the evaluation of small joints and guiding procedures performed on the distal extremities where sharp contours allow for limited contact with the probe surface.
- High-frequency (17-5 MHz) linear array transducer – The linear 12-5 MHz is the workhorse transducer for musculoskeletal US, while the linear 17-5 MHz transducer may be used for the evaluation of more superficial structures.
- Low to medium-frequency (5-2 MHz) curvilinear array transducer – The 5-9 MHz curvilinear transducer is less commonly used in musculoskeletal US but has a role in the evaluation of deep structures or patients with larger body habitus.
- Both linear transducers are used for superficial imaging, whereas the curvilinear transducer’s lower frequency facilitates examination of deeper regions such as the hip
Musculoskeletal ultrasound involves not only the imaging of soft tissues throughout their available range, but also the visualization of elements structurally or functionally connected with them, e.g. the examination of muscle-tendon units should include the tendons at the muscle belly level and the naked (bare) part, their entheses, as well as all peritendinous elements, such as the peritendineum, sheaths, retinaculum, bursa, fascia, subcutaneous tissue, fat folds or bone outlines, main vessels and regional nerves.
Due to the specificity of the diagnosed tissues, musculoskeletal ultrasound requires top-class equipment with the highest quality transducers and, if possible, full software options to improve image quality, i.e. resolution, contrast and the best possible artifact removal.
In addition to providing high quality grayscale images, ultrasound apparatus should also feature the most sensitive color Doppler options
It’s worth noting that the specific transducer used may vary based on the individual clinic or facility, the patient’s specific needs, and the expertise of the sonographer or radiologist performing the ultrasound examination. The choice of transducer will depend on the desired depth of penetration, the target structure being imaged, and the level of detail required in the image.