Transducer Handling

In 1999, the American Institute for Ultrasound Medicine (AIUM) established terminology to describe transducer manipulation.  These terms do not include specification of direction (i.e. proximal, distal, and clockwise).  When combined, these maneuvers can be used to optimize an ultrasound image by accounting for anatomical variances within the tissue.  While these terms and manipulations may seem like common sense or second nature, they provide a standardized vocabulary that can be very useful when describing how a particular image was obtained.

In general, a transducer can be manipulated in five ways:

  • Sliding
  • Tilting
  • Rocking
  • Rotating
  • Compressing

 

Before starting a procedure, ensure the transducer is properly orientated (discussed later).  Apply sufficient gel to the end of the transducer.  Gel serves as a coupler between air and the skin.  Without it, the significant differences in acoustic impedance between the air and tissue would cause the sound to be reflected; preventing it from entering the skin.  Place the transducer flat against the patient’s skin for maximum contact, with the ulnar aspect of the hand at the base of the transducer resting on the patient, as seen below left.  If the transducer is held too high, as in the picture on the right, it will be difficult to maintain a stable and consistent image.   Be gentle, but firm; the sound will penetrate tissue regardless of the pressure applied.  Initially, the transducer should be held perpendicular to the skin.  After obtaining a preliminary picture, it can then be manipulated to optimize the image.

Sliding
Many regional procedures can be complicated by small blood vessels which course over or near the nerves.  Sliding enables the practitioner to evaluate the anatomy and determine the best location where the block can be completed effectively, but safely.

 

Rocking
Air artifact occurs when the entire transducer is not contact with the skin.  This can occur when the transducer “footprint” is larger than the body surface being scanned (such as the ankle or wrist), or at areas where the body is not completely flat.  Rocking the transducer in the direction of the artifact, creates the contact that is needed to generate an image.

Tilting                                                                   The greatest reflection of sound occurs when the transducer is perpendicular to the desired structure to be imaged.  As nerves travel distally through the body, they often move from deep within the tissue to more superficial areas.  When this occurs the nerves are often not parallel with the skin/transducer interface.  Tilting the transducer can help create an angle closer to 90 degrees that will improve the reflection of the nerve, making it more visible on ultrasound.

Rotating
As noted previously with sliding, regional anesthesia is often complicated by small blood vessels that travel around and near the nerves we wish to block.  Rotating the transducer allows the provider to optimize the desired structure in the image on the same plane while minimizing or avoiding complicating ones.

 

 Compressing
When structures deep in the tissue are imaged, the strength of the sound wave is reduced due to attenuation.  Because the returning signals are weak,  images may have poor resolution, making a block  difficult to perform.  Compressing is used to decrease space from the skin to the desired structure being imaged, improving resolution.  However, compressing can also collapse veins and even small arteries increasing the potential for vascular puncture.


References

AIUM Technical Bulletin. Transducer manipulation. American institute of ultrasound medicine. J Ultrasound Med. 1999; 18:169-175.

 

    Legal Disclaimer

  • Provision of education and research information only - always seek professional advice

    The VAULT website was developed by Christian R. Falyar, CRNA, DNAP, to share information related to ultrasound-guided regional anesthesia with other anesthesia providers. It is not intended to be a substitute for accredited regional anesthesia training. Christian R. Falyar CRNA, DNAP does not accept any liability for any injury, loss or damage that results from the use of or reliance on information contained in this website.
  • Quality of information - always check the information

    Christian R. Falyar, CRNA, DNAP has made every effort to ensure the quality of the information presented on this website is current and checks it regularly. However, before relying on the material on this website, users should carefully evaluate its accuracy, currency, completeness and relevance to their practice. Christian R. Falyar, CRNA, DNAP, cannot guarantee and assumes no legal liability or responsibility for the accuracy, currency or completeness of the information.
  • Links to external websites

    This website may contain links to other websites which are external to the VAULT website. Christian R. Falyar, CRNA, DNAP takes reasonable care in selecting linking websites. It is the responsibility of the user to make their own decisions about the accuracy, currency, reliability and correctness of information contained in linked external websites. Linkage to external websites should not be taken to be an endorsement or a recommendation of any third party products or services offered by virtue of any information, material or content linked from or to this website. Users of links provided by this website are responsible for being aware of which organization is hosting the website they visit. Views or recommendations provided in linked websites do not necessarily reflect those of Christian R. Falyar, CRNA, DNAP.