Anisotropy is the most significant and commonly encountered artifact (potential pitfall / imaging mistake) with the superficial structures in musculoskeletal ultrasound and it is particularly potentially problematic when using linear transducers. It refers to the property of tissue to differentially conduct or reflect sound waves back to the transducer based on the angle of incidence of the sound waves. The anisotropic artifact refers to a darkening and loss of resolution of the image which occurs when the approach of the sound waves is less than perpendicular (ie, angle of incidence greater than 0 degrees). Therefore, the sonographer should attempt to keep the direction of the beam as close to perpendicular as possible.
Anisotropy is still one of the main challenges for sonographers who are developing their learning curve on a certain level. Being aware of the potential presence of anisotropy is important in qualitative scanning and pathology recognition. In SonoSkills courses we pay a lot of attention in the recognition and prevention of anisotropy.