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
Sample Population—2 normal (injury-free) SDF tendons
obtained from a 3-year-old Thoroughbred and a
9-year-old Dutch Warmblood horse.
Procedure—Tendons were mounted in a custommade
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 ultrasonographic images 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 and Clinical Relevance—The correlation
routine permits exclusive resolution of structurerelated
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. (Am J Vet Res
Objective—To correlate quantitative analysis of ultrasonographic
images of normal (injury-free) equine
superficial digital flexor (SDF) tendons and equine
SFD tendons that have pathologic changes with corresponding
Sample Population—4 SDF tendons, 2 of which
had various stages of tissue integrity. The 2 ipsilateral
tendons were used as points of reference.
Procedure—Tendons were mounted in a custommade
device that permitted sequential scanning,
transversely and perpendicular to the tendon long
axis. At precise steps of 0.5 mm, transverse ultrasonographic
images were collected. Subsequently,
tendons were fixed and prepared for histologic
examination. The following 8 tissue types were
discerned: normal young, normal old, necrotic,
early granulation, late granulation, early fibrotic,
late fibrotic, and scar tissues. In areas of interest,
the corresponding ultrasonographic images were
selected for gray level statistical analysis.
Results—Compared with other tissue types, earlystage
granulation tissue was characterized by substantially
lower mean gray level and a clearly different
histogram. Necrotic tissue had a higher mean
gray level, with a virtually normal histogram. In late
granulation and early fibrotic tissues, the mean gray
level and the histogram could not be discerned
from those of normal tendon tissue. The same
applied to late fibrotic and scar tissues; mean gray
levels were fractionally lower than those of normal
tendon tissue with a completely normal histogram.
Conclusions—Although quantification of the transverse
ultrasonographic image by use of first-order
gray level statistics may be helpful, the method is
not sufficiently sensitive to accurately and unequivocally
determine the type of tendon tissue.
Quantitative analysis should incorporate transverse
and longitudinal information. (Am J Vet Res 2000;61:
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)
Objective—To evaluate effectiveness of computerized
discrimination between structure-related and
non–structure-related echoes in ultrasonographic
images for quantitative evaluation of tendon structural
integrity in horses.
Sample Population—4 superficial digital flexor tendons
(2 damaged tendons, 2 normal tendons).
Procedure—Transverse ultrasonographic images that
precisely matched histologic sections were obtained
in fixed steps along the long axis of each tendon.
Distribution, intensity, and delineation of structurerelated
echoes, quantitatively expressed as the correlation
ratio and steadiness ratio , were compared with
histologic findings in tissue that was normal or had
necrosis, early granulation, late granulation, early
fibrosis, or inferior repair.
Results—In normal tendon, the even distribution of
structure-related echoes with high intensity and sharp
delineation yielded high correlation ratio and steadiness
ratio. In areas of necrosis, collapsed endotendon
septa yielded solid but blurred structure-related
echoes (high correlation ration and low steadiness
ratio). In early granulation tissue, complete lack of
organization caused zero values for both ratios. In late
granulation tissue, reorganization and swollen endotendon
septa yielded poorly delineated structurerelated
echoes (high correlation ratio, low steadiness
ratio). In early fibrosis, rearrangement of bundles
resulted in normal correlation ration and slightly low
steadiness ratio. In inferior repair, the almost complete
lack of structural reorganization resulted in heterogeneous
poorly delineated low-intensity echoes
(low correlation ratio and steadiness ratio).
Conclusions and Clinical Relevance—The combination
of correlation ratio and steadiness ratio accurately
reflects histopathologic findings, making computerized
correlation of ultrasonographic images an efficient
tool for quantitative evaluation of tendon structural
integrity. (Am J Vet Res 2001;62:1159–1166)
Objective—To evaluate quantitative ultrasonography for objective monitoring of the healing process and prognostication of repair quality in equine superficial digital flexor (SDF) tendons.
Animals—6 horses with standardized surgical lesions in SDF tendons of both forelimbs.
Procedures—Healing was monitored for 20 weeks after surgery by use of computerized ultrasonography. Pixels were categorized as C (intact fasciculi), B (incomplete fasciculi), E (accumulations of cells and fibrils), or N (homogenous fluid or cells). Four scars with the best quality of repair (repair group) and 4 scars with the lowest quality (inferior repair group) were identified histologically. Ratios for C, B, E, and N in both groups were compared.
Results—During 4 weeks after surgery, lesions increased 2- to 4-fold in length and 10-fold in volume. Until week 3 or 4, structure-related C and B ratios decreased sharply, whereas E and N ratios increased. After week 4, C and B ratios increased with gradually decreasing E and N ratios. At week 12, C and B ratios were equivalent. After week 12, C ratio increased slowly, but B ratio more rapidly. At week 20, C ratio remained constant, B ratio was substantially increased, and E and N ratios decreased. Values for the inferior repair group were most aberrant from normal. Ratios for C differed significantly between repair and inferior repair groups at weeks 16 and 18 and for B beginning at 14 weeks.
Conclusions and Clinical Relevance—Computerized ultrasonography provided an excellent tool for objective monitoring of healing tendons in horses and reliable prognostication of repair quality.