Anisotropy

Case contributed by Dr Matt A. Morgan

Presentation

Asymptomatic.

Patient Data

Age: 35Y
Gender: Male
Ultrasound

Example #1

In this patient with a normal Achilles tendon, the transducer was rocked back and forth to demonstrate the appearance of anisotropy.

Ultrasound

Example #2

In this patient with a normal wrist, the transducer was rocked back and forth to demonstrate the appearance of anisotropy. (1: flexor digitorum tendons. 2: flexor carpi radialis. 3: palmaris longus. 4: median nerve). Note how anisotropy increases the contrast between the tendon and nerve against the surrounding fat.

Case Discussion

When practicing musculoskeletal ultrasound, one should be aware of anisotropy.

Unlike many other structures in the body, the echo received from a compact fibrillar structure (such as a tendon or a nerve) is highly dependent on the angle of incidence. This has the potential to cause normal structures to appear abnormal.  For instance, a normal tendon may appear dark and tendinotic if it is insonated at less than 90 degrees (less than perpendicular to the long axis of the tendon).

Anisotropy is particularly important in evaluation of tendons and nerves that turn corners or dive beneath other structures; for instance, the peroneal tendons around the lateral malleolus, or the median nerve dipping below the flexor retinaculum.

PlayAdd to Share

Case information

rID: 31817
Case created: 30th Oct 2014
Last edited: 4th Aug 2017
Inclusion in quiz mode: Included

Updating… Please wait.
Loadinganimation

Alert accept

Error Unable to process the form. Check for errors and try again.

Alert accept Thank you for updating your details.