Computerized ultrasonographic tissue
characterization of equine superficial digital
flexor tendons by means of stability
quantification of echo patterns in contiguous
transverse ultrasonographic images
Objective—To describe a method of computerized
ultrasonographic tissue characterization that includes
structures below the size limits of resolution in equine
superficial digital flexor tendons.
Sample Population—2 damaged and 2 structurally
normal superficial digital flexor tendons.
Procedure—Transverse ultrasonographic images were
collected along the tendon long axis. Stability of echo
pattern was quantified by means of variation in gray levels
of each pixel in contiguous images and expressed
as correlation, entropy, and waviness ratios.
Results—Normal young and normal old tissues were
characterized by high correlation and low entropy and
waviness ratios. In necrotic tissue, collapsed intratendinous
septa resulted in high correlation, moderate
entropy, and high waviness ratios. In early granulation tissue,
complete lack of bundle formation resulted in values
of zero for correlation and waviness ratios; loose
connective tissue matrix resulted in a high entropy ratio.
In late granulation tissue, formation of new bundles
resulted in a high correlation ratio; swollen intratendinous
septa and incomplete organization of connective
tissue matrix were reflected in high entropy and waviness
ratios. In early fibrotic tissue, rearrangement of tendon
bundles resulted in a correlation ratio within reference
range and a slight increase in the waviness ratio; an
increase in cellularity and lack of fibrillar arrangement led
to an increase in the entropy ratio. In late fibrotic and scar
tissues, inferior quality of repair with almost complete
lack of organization was reflected in low to moderate
correlation, low waviness, and high entropy ratios.
Conclusions and Clinical Relevance—Stability of
echo patterns accurately reflects homogeneity of tendons
in horses. (Am J Vet Res 2003;64:366–375)