Objective—To quantitatively assess distractioninduced bone formation in a crural lengthening model in dogs by use of delayed-image bone scintigraphy.
Animals—12 mature Labrador Retrievers.
Procedure—Dogs were randomly allocated to 1 of 3 groups. A circular external skeletal fixation system was mounted on the right crus of each dog. Osteotomy of the distal portion of the tibia and fibula was performed in groups 1 and 2 and was followed by a lengthening procedure of 10 mm in the first group only. The third group served as sham-operated controls. Delayed-image bone scintigraphy with technetium-99m hydroxy methylene diphosphonate was performed 2, 4, and 6 weeks after surgery. Delayedimage–to–region-of-interest, delayed-image–to–crural, and delayed-image–to–femoral scintigraphic activity ratios were calculated. New bone formation was quantified by use of densitometric image analysis, and values for the scintigraphic ratios were compared.
Results—In the distraction and osteotomy groups, delayed-image–to–region-of-interest and delayedimage-to-crural ratios increased significantly. Although densitometric image analysis revealed increased bone formation after distraction, the region-of-interest ratios and crural ratios were similar in both groups. All dogs had increased delayedimage–to–femoral ratios.
Conclusions and Clinical Relevance—Delayed-image bone scintigraphy ratios were not effective at differentiating between the amounts of distraction-induced bone and osteotomy-induced bone. Metabolic bone activity in the adjacent femur was increased as a consequence of circular external skeletal fixator placement. Delayed-image bone scintigraphy was not adequately sensitive to quantitatively monitor bone formation but may be useful as an early predictor of bone healing.
Objective—To determine the reproducibility and accuracy of computed tomographic (CT) measurements of pituitary gland dimensions in healthy dogs.
Animals—35 healthy sexually intact adult dogs.
Procedures—2 observers independently viewed CT images of the skull in 35 dogs twice. Pituitary gland height, width, length, and volume and pituitary gland height–to–brain area ratio (P:B ratio) were measured or calculated. Intraobserver and interobserver agreement indexes (AIs) were calculated for pituitary gland dimensions. Computed tomography was performed also on 5 phantoms, and both observers measured phantom dimensions twice. True-value AIs were calculated for the phantom study.
Results—The mean ± SD interobserver AI between observer 1 and 2 for pituitary gland height and the P:B ratio was 0.90 ± 0.07. The intraobserver AI for pituitary gland height and the P:B ratio was 0.97 ± 0.04 for observer 1 and 0.94 ± 0.04 for observer 2. The intraand interobserver AIs for the other dimensions were lower than those for pituitary gland height and the P:B ratio. All phantom dimensions on CT images were underestimated significantly, compared with their true values.
Conclusions and Clinical Relevance—The intra- and interobserver AIs for pituitary gland dimension measurements on CT images were high. However, the same observer preferably should perform serial measurements. Window settings influence pituitary gland dimension measurements, and predetermined window settings are recommended to make comparisons among dogs. Pituitary gland dimension measurements made from CT images in our study underestimated the true values.
Objective—To assess intra- and interobserver repeatability of ocular biometric measurements obtained by means of high-resolution B-mode ultrasonography in dogs.
Animals—6 Beagles without ocular abnormalities.
Procedures—B-mode ultrasonography was performed bilaterally with a 10.5-MHz broadband compact linear array transducer. All measurements were made on 2 different occasions by 2 observers. The Bland-Altman method was used to assess agreement between measurements obtained by the 2 observers and between the 2 sets of measurements obtained by each observer.
Results—Intra- and interobserver repeatability was highest for larger measurements, such as depth of the eye and depth of the anterior chamber. When repeatability was examined, bias was significantly different from 0 for only a few measurements, but the percentage difference between observations was as high as 180% for some measurements.
Conclusions and Clinical Relevance—Results suggest that most measurements of intraocular distances and structures obtained by means of high-resolution B-mode ultrasonography have acceptable intra- and interobserver repeatability. However, the percentage difference between observations can be high for smaller measurements.
Objective—To evaluate thin-slice 3-dimensional gradient-echo (GE) magnetic resonance imaging (MRI) of the pituitary gland in healthy dogs.
Animals—11 healthy dogs.
Procedures—By use of a 0.2-Tesla open magnet, MRI of the skull was performed with T1-weighted GE sequences and various protocols with variations in imaging plane, slice thickness, and flip angle before and after administration of contrast medium; multiplanar reconstructions were made. The pituitary region was subjectively assessed, and its dimensions were measured. Image quality was determined by calculation of contrast-to-noise and signal-to-noise ratios.
Results—Best-detailed images were obtained with a T1-weighted GE sequence with 1-mm slice thickness and 30° flip angle before and after administration of contrast medium. Images with flip angles > 50° were of poor quality. Quality of multiplanar reconstruction images with 1-mm slices was better than with 2-mm slices. The bright signal was best seen without contrast medium. With contrast medium, the dorsal border of the pituitary gland was clearly delineated, but lateral borders were more difficult to discern.
Conclusions and Clinical Relevance—MRI of the canine pituitary gland with a 0.2-Tesla open magnet should include a T1-weighted GE sequence with 1-mm slice thickness and flip angle of 30° before and after administration of contrast medium. The neurohypophysis was best visualized without contrast medium. The MRI examination permitted differentiation between the pituitary gland and surrounding structures.
Objective—To assess the extent of agreement between computed tomography (CT), magnetic resonance imaging (MRI), and surgical findings in dogs with degenerative lumbosacral stenosis.
Animals—35 dogs with degenerative lumbosacral stenosis.
Procedures—Results of preoperative CT and MRI were compared with surgical findings with respect to degree and location of disk protrusion, position of the dural sac, amount of epidural fat, and swelling of spinal nerve roots.
Results—A lumbosacral step was seen on radiographic images from 22 of 32 (69%) dogs, on CT images from 23 of 35 (66%) dogs, and on MR images from 21 of 35 (60%) dogs. Most dogs had slight or moderate disk protrusion that was centrally located. There was substantial or near perfect agreement between CT and MRI findings in regard to degree of disk protrusion (kappa, 0.88), location of disk protrusion (0.63), position of the dural sac (0.89), amount of epidural fat (0.72), and swelling of spinal nerve roots (0.60). The degree of agreement between CT and surgical findings and between MRI and surgical findings was moderate in regard to degree and location of disk protrusion (kappa, 0.44 to 0.56) and swelling of spinal nerve roots (0.40 and 0.50).
Conclusions and Clinical Relevance—Results indicate that there is a high degree of agreement between CT and MRI findings in dogs with degenerative lumbosacral stenosis but that the degree of agreement between diagnostic imaging findings and surgical findings is lower.
Objective—To determine portal hemodynamic
changes associated with surgical shunt ligation and
establish ultrasonographic criteria for determining the
optimal degree of shunt narrowing and predicting outcome.
Animals—17 dogs, each with a single congenital
extrahepatic portosystemic shunt.
Procedure—Pre- and postligation flow velocities and
flow directions were determined by Doppler ultrasonography
intraoperatively in the shunt and in the portal
vein cranial and caudal to the shunt origin. Outcome
was evaluated 1 month after surgery by measuring
blood ammonia concentration and performing abdominal
Results—Hepatofugal flow was detected in 9 of 17
dogs before shunt attenuation in the portal segment
that was between the shunt origin and the entering
point of the gastroduodenal vein. If hepatofugal flow
became hepatopetal after shunt ligation, hyperammonemia
resolved. Hepatofugal portal flow was
caused by blood that flowed from the gastroduodenal
vein toward the shunt. Shunt attenuation converted
hepatofugal flow to hepatopetal in the shunt in 12 of
17 dogs. Chronic portal hypertension developed or
perioperative death occurred when the portal congestion
index caudal to the shunt origin increased by
> 3.6 times.
Conclusions and Clinical Relevance—After hepatopetal
flow in the cranial portal vein and the shunt is
established, further shunt narrowing is contraindicated.
Increase of the portal congestion index caudal to the
shunt > 3.5 times should be avoided. Poor outcome
because of severe hypoplasia of the portal branches can
be expected if the flow direction remains hepatofugal
after shunt occlusion cranial to the shunt origin. ( J Am
Vet Med Assoc 2004;224:395–402)
Objective—To determine the contrast enhancement
pattern of the pituitary gland in healthy dogs via
dynamic computed tomography (CT).
Procedure—With each dog in sternal recumbency,
transverse CT scans were made perpendicular to the
skull base from the rostral clinoid processes to the
dorsum sellae. At the position of the image that contained
the largest cross section of the pituitary gland,
a series of 9 to 11 scans was made during and after
IV injection of contrast medium (dynamic CT scans).
The contrast enhancement pattern of the pituitary
gland and surrounding arteries was assessed visually
and by use of time-density curves.
Results—After strong enhancement of the maxillary
arteries, the intracavernous parts of the internal
carotid arteries, and the communicating arteries of
the arterial cerebral circle, there was a strong
enhancement of the central part of the pituitary gland
followed by enhancement of its peripheral part. On
the last images of the dynamic series of the pituitary
gland, the central part was hypodense, compared
with the peripheral part. Time-density curves confirmed
an early, strong enhancement of the central
part and a delayed, less strong enhancement of the
peripheral part of the gland.
Conclusions and Clinical Relevance—The difference
in enhancement between the central and
peripheral parts of the pituitary gland was attributable
to a difference in vascularization of the neurohypophysis
and adenohypophysis, respectively. Distortion
or disappearance of the strong central enhancement
(pituitary flush) may be used for the detection and
localization of pituitary abnormalities in the adenohypophysis.
(Am J Vet Res 2004;65:1518–1524)
Objective—To describe clinical, ultrasonographic, and computed tomographic (CT) features of confirmed neoplastic and nonneoplastic disease in dogs with unilateral orbital diseases, determine criteria to differentiate between the 2 conditions, and assess the relative value of ultrasonography and CT for the differential diagnosis of these 2 conditions.
Animals—29 dogs with unilateral neoplastic orbital disease and 16 dogs with unilateral nonneoplastic orbital disease.
Procedures—Clinical history and results of physical and ophthalmologic examinations were recorded. Ultrasonographic and CT images were evaluated, and discriminating factors were identified to differentiate neoplastic from nonneoplastic diseases. Diagnostic value of ultrasonography and CT was assessed.
Results—Dogs with neoplastic disease were significantly older; had clinical signs for a longer time before initial examination; had more progressive onset of clinical signs; and more frequently had protrusion of the nictitating membrane, fever, and anorexia. The most discriminating factor for both imaging modalities was delineation of the margins (odds ratio was 41.7 for ultrasonography and 45 for CT), with neoplastic lesions clearly delineated more often. Ultrasonographically, neoplastic lesions were more frequently hypoechoic and homogeneous, with indentation of the globe and bone involvement evident more frequently than for nonneoplastic lesions. Mineralization was detected only with neoplasia. Fluctuant fluid was seen more frequently in dogs with nonneoplastic disease. Computed tomography more frequently revealed extraorbital involvement. Diagnostic value was similar for both imaging modalities.
Conclusions and Clinical Relevance—Ultrasonography and CT are valuable imaging modalities to assist in differentiating neoplastic from nonneoplastic unilateral orbital disease in dogs.