Structure-related echoes in ultrasonographic images of equine superficial digital flexor tendons.
OBJECTIVE
To develop a method to discriminate between structure-related echoes and echoes resulting from interference, as observed in transverse ultrasonographic images of equine superficial digital flexor (SDF) tendons.


METHODS
2 normal (injury-free) SDF tendons obtained from a 3-year-old Thoroughbred and a 9-year-old Dutch Warmblood horse.


METHODS
Tendons were mounted in a custom-made device that permitted exact transverse and perpendicular sequential scanning with precise steps of 0.5 mm along the long axis of the tendon. Photographs of transverse tendon sections at the exact scanning locations were obtained. Propagation, reflection, and refraction artifacts were quantified, and an image rectification procedure was developed, allowing exact matching of each photograph with the corresponding ultrasonographic image. A correlation routine was developed that departed from this transverse ultrasonographic image (position 0); this routine added information from images collected at precise distances of 0.5 and 1 mm on both sides of the actual scan location (positions -2, -1, +1, +2).


RESULTS
By use of the correlation routine, echoes that remained steady over all 5 images were enhanced and resolved, and constantly changing echoes were multiplicatively reduced and faded. This correlated image could be projected over the rectified photograph, and the resolved echoes matched perfectly with the endotendon septa surrounding fibers and fasciculi.


CONCLUSIONS
The correlation routine permits exclusive resolution of structure-related echoes, as echoes resulting from interference are faded. The technique described can produce images that depict only the essential structure-related information. In this way, the clinical assessment of tendon integrity is greatly facilitated.
van Schie
H T
HT
Raaphorst Equine Clinic, Wassenaar, The Netherlands.
Bakker
E M
EM
D000818:Animals; D016477:Artifacts; D005260:Female; D006736:Horses; D007091:Image Processing, Computer-Assisted; D008297:Male; D012016:Reference Values; D013710:Tendons / Q000000981:diagnostic imaging* / Q000502:physiology*; D014463:Ultrasonography / Q000379:methods / Q000662:veterinary*