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Abstract

Objective—To determine whether results of magnetic resonance imaging (MRI) and computed tomography (CT) are associated with postoperative outcome in working dogs with degenerative lumbosacral stenosis.

Design—Prospective cohort study.

Animals—12 dogs treated surgically for degenerative lumbosacral stenosis.

Procedure—Procedure—The lumbosacral vertebral column was examined before surgery by use of MRI and CT and after surgery by use of CT. Outcome, based on performance in standardized training exercises, was assessed 6 months after decompressive surgery. Associations between imaging results and postoperative outcome were determined by use of a Fisher exact test and logistic regression.

Results—None of the dogs were able to perform their duties before surgery. By 6 months after surgery, 8 of 12 dogs had been returned to full active duty. Nerve tissue compression was effectively localized by use of CT and MRI. Significant associations between results of imaging studies and postoperative outcome were not identified.

Conclusions and Clinical Relevance—Surgical intervention is justified in high-performance working dogs with degenerative lumbosacral stenosis. However, results of imaging studies may be less important than clinical or surgical factors for predicting outcome in affected dogs. (J Am Vet Med Assoc 2000;216:1769–1774)

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To characterize the computed tomographic (CT) and cross-sectional anatomic features of myofascial compartments and soft tissue spaces in the manus of cadavers of dogs without forelimb disease.

Animals—33 cadavers of adult medium- to large-breed dogs without forelimb disease.

Procedures—Forelimbs were removed from the cadavers within 4 hours after euthanasia or within 6 hours after thawing from initial freezing. Specimens were then frozen for variable periods and thawed for approximately 16 hours before use. Each manus of 60 forelimbs underwent CT before and after injection of a radiopaque, blue-staining contrast medium into locations where soft tissue spaces and myofascial compartments were predicted (on the basis of pilot study data [6 forelimbs]). Two veterinary radiologists reviewed CT images and recorded the presence or absence of a discrete space or compartment at each injection site. Each manus was subsequently dissected or sectioned transversely. Locations of blue-staining contrast medium accumulation were compared with locations of contrast enhancement in CT images. Anatomic structures within each soft tissue space or myofascial compartment were described.

Results—13 soft tissue spaces and 5 myofascial compartments were identified in the manus. Three myofascial structures that were examined were determined not to be compartments.

Conclusions and Clinical Relevance—Knowledge of soft tissue spaces and myofascial compartments are used to map the likely spread of disease in the hands and feet of humans. Thus, understanding the locations and extent of similar structures in the canine manus may improve the effectiveness of surgical interventions in dogs with injury or inflammation of this region of the forelimb.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To measure effects of dog position on L7-S1 intervertebral foraminal area and lumbosacral (LS) angle by means of computed tomography (CT) and determine whether changes in values between positions are associated with clinical signs in dogs with LS disease.

Animals—86 dogs examined via a positional CT protocol that included flexion and extension scans of L7-S1.

Procedures—Archived CT images and medical records were reviewed. Included dogs had good-quality flexion and extension CT scans of L7-S1 and no evidence of fractures, neoplasia, or previous LS surgery. One person who was unaware of CT findings recorded clinical status with regard to 3 signs of LS disease (right or left hind limb lameness and LS pain) at the time of CT evaluation. One person who was unaware of clinical findings measured L7-S1 foraminal areas and LS angles, with the aid of an image-analysis workstation and reformatted parasagittal planar CT images.

Results—Intraobserver variation for measurements of L7-S1 foraminal area ranged from 6.4% to 6.6%. Mean foraminal area and LS angle were significantly smaller when vertebral columns were extended versus flexed. Percentage positional change in L7-S1 foraminal area or LS angle was not significantly different among dogs with versus without each clinical sign. There was a significant correlation between percentage positional change in L7-S1 foraminal area and LS angle in dogs with versus without ipsilateral hind limb lameness and LS pain.

Conclusions and Clinical Relevance—Positional CT is a feasible technique for quantifying dynamic changes in L7-S1 intervertebral foraminal morphology in dogs with LS disease.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To test the effects of computed tomography (CT) image plane and window settings on diagnostic certainty for CT characteristics associated with dysplastic elbow joints (elbow joint dysplasia) in dogs and to provide optimal display guidelines for these CT characteristics.

Sample Population—CT images of 50 dysplastic elbow joints from 49 lame dogs and 10 elbow joints from 5 sound dogs.

Procedures—CT image data were obtained in transverse, sagittal, and dorsal planes. Each plane was examined by use of 3 Hounsfield unit (HU) window settings. Two veterinary radiologists independently evaluated sets of CT images for evidence of 7 CT characteristics. Effect of elbow joint status, image plane, and window settings on diagnostic certainty for these CT characteristics was tested by use of a visual analogue scale.

Results—Diagnostic certainty for abnormalities of the medial coronoid process (MCP) and radial incisure was highest in the transverse plane, subchondral defects or sclerosis of the trochlea humeri was highest in the dorsal plane, and joint incongruity was highest in the sagittal plane. Certainty for hypoattenuating subchondral defects or fissures was highest at 2,500 or 3,500 HUs, whereas certainty for subchondral sclerosis was highest at 1,500 HUs and lowest at 3,500 HUs.

Conclusions and Clinical Relevance—Diagnostic certainty for CT characteristics of elbow joint dysplasia in dogs was affected by image display variables. Diagnostic certainty for altered subchondral bone density was primarily influenced by window settings, whereas structural MCP abnormalities and joint incongruity were influenced most by image plane.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate nonselective computed tomographic (CT) venography for evaluating the cervical internal vertebral venous plexus (IVVP), define the diameter and area dimensions of the IVVP, and determine the relationship between dimensions of the cervical IVVP and other vertebral components in medium-sized dogs.

Animals—6 healthy dogs that weighed 18 to 27 kg.

Procedure—Helical CT scans were performed from C1 to C7 before and after IV injection of contrast medium (480 mg of iodine/kg) and a continuous infusion (240 mg of iodine/kg). Image data were transferred to a CT workstation, and measurements were performed on displayed transverse images. Diameter and area measurements of the vertebral canal, dural sac, IVVP, and vertebral body were obtained at C3 to C7.

Results—Opacification of vertebral venous structures was achieved in all dogs with no adverse reactions. Sagittal diameters of the IVVP for C3 to C7 ranged from 0.6 to 3.2 mm. Transverse diameters ranged from 2.32 to 5.74 mm. The IVVP area represented 12.4% of the mean vertebral canal transverse area and 30.61% of the mean vertebral epidural space area. Area measurements of the IVVP were significantly correlated with vertebral canal area and dural sac area.

Conclusions and Clinical Relevance—Results indicated that nonselective CT venography is a safe, sensitive method for performing morphometric assessments of the cervical IVVP in dogs. Findings support the theory that there may be a physiologic or developmental relationship between cervical vertebral canal components. (Am J Vet Res 2005;66:2039–2045)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To describe the vascular distribution pattern of contrast medium during intraosseous regional perfusion (IORP) of the distal portion of the equine forelimb.

Sample Population—13 cadaveric forelimbs from 12 horses without forelimb diseases.

Procedures—Serial lateromedial radiographic views were taken of the distal portion of 10 heparinized cadaveric forelimbs at 0, 1, 2, 6, 15, and 30 minutes during IORP of the third metacarpal bone (MCIII) by use of iodinated contrast medium and a tourniquet placed over the proximal portion of MCIII. Vascular regions of interest (ROI) were created for each radiograph. Reviewers identified the presence or absence of contrast medium–induced opacified vessels in all ROI on radiographs. This information was summarized to identify vessel-filling patterns over time. Vessel identification was verified by use of computed tomography angiography and latex perfusion studies on the distal portion of separate cadaveric forelimbs.

Results—During IORP, contrast medium filled the medullary cavity of the MCIII; exited via transcortical vessels; and diffused distally to the remaining arteries and veins of the forelimb, distal to the tourniquet. Maximum vessel and soft tissue opacification occurred in most specimens at 6 and 30 minutes, respectively. Serial radiography vessel patterns matched those of computed tomography images and dissected specimens.

Conclusions and Clinical Relevance—IORP provides a repeatable pattern of vascular distribution in the distal portion of the equine forelimb. To our knowledge, our study provides the first documentation of arterial perfusion by use of IORP; results of previous reports indicate that IORP delivers medications to only the venous vessels of the perfused forelimb.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To analyze survival time and identify prognostic factors associated with outcome following discharge in dogs with primary brain tumors treated palliatively.

Design—Prospective case series.

Animals—51 dogs with 5 histopathologic types of brain tumors.

Procedures—Owners with dogs examined from 2004 to 2008 were invited to participate if dogs had CT or MRI evidence of a brain mass that was histopathologically confirmed as a neoplasm upon death, dogs survived for ≥ 48 hours after hospital discharge, and treatments following discharge were limited to administration of prednisone or phenobarbital. Prognostic factors, including signalment, clinical signs (including duration), tumor type, tumor location, degree of peritumoral edema, lesion burden, and prescribed treatment, were evaluated. Survival time was estimated and animal- and tumor-specific variables evaluated as potential prognostic factors.

Results—The median survival time in all dogs was 69 days (95% confidence interval [CI], 18 to 201 days). Multivariate analyses identified neuroanatomic location as the only significant prognostic variable, with the survival time of dogs with infratentorial tumors (n = 18) being significantly shorter (median, 28 days; 95% CI, 19 to 68 days) than survival time of dogs with supratentorial (33) tumors (median, 178 days; 95% CI, 119 to 270 days). Seizures were the most common clinical sign associated with supratentorial tumors (24/33 [73%]) and central vestibular dysfunction with infratentorial tumors (12/18).

Conclusions and Clinical Relevance—Dogs with palliatively treated primary brain tumors, particularly those with tumors in the cerebellum, pons, or medulla, had a poor prognosis. However, dogs with supratentorial tumors had survival times > 3 months.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objectives—To evaluate computed tomography (CT) densitometry as a technique for quantifying contrast enhancement of compressive soft tissues in the canine lumbosacral vertebral canal and to determine whether the degree of contrast enhancement can be used to help predict tissue type or histopathologic characteristics.

Animals—29 large breed dogs with lumbosacral stenosis.

Procedure—Contrast-enhanced CT of L5-S3 was performed by use of a previously described protocol. At each disk level, CT densities of a water-filled syringe, epaxial muscles, and 4 vertebral canal locations were measured. Mean tissue enhancement was calculated by vertebral canal location, using water-filled syringe enhancement as a correction factor. Corrected CT enhancement was compared with tissue type, degree of tissue inflammation, and degree of tissue activity.

Results—Intravenous contrast administration of contrast medium significantly increased CT densities of water-filled syringes and epaxial muscles. Corrected CT enhancement of vertebral canal soft tissues at stenotic sites was greater than at nonstenotic sites. There was no association between enhancement and tissue type for any vertebral canal location. There was no correlation between enhancement and degree of tissue inflammation. There was a correlation between enhancement and tissue activity in the dorsal vertebral canal only.

Conclusions and Clinical Relevance—A water-filled syringe is a useful calibration tool for CT density measurements. The degree of tissue contrast enhancement, measured by CT densitometry, can be helpful for predicting the location of compressive soft tissues in dogs with lumbosacral stenosis. However, it is of limited value for predicting compressive soft-tissue types or histopathologic characteristics. (Am J Vet Res 2002;63:733–737)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To describe the anatomic features of the pituitary gland region in horses via computed tomography (CT) and determine the accuracy of CT for estimating normal equine pituitary gland dimensions.

Animals—25 adult horses with no clinical signs of pituitary disease.

Procedure—Transverse CT images and gross transverse tissue sections were compared in 2 horses. Contrast-enhanced CT of the pituitary gland region was performed postmortem in 23 horses with 4 slice thickness and interval settings (10-mm contiguous or overlapping slices and 4-mm contiguous or overlapping slices). Gross and CT estimates of pituitary gland dimensions were compared via ANOVA. Accuracy of CT estimates was calculated with gross pituitary gland measurements as the known value.

Results—Pituitary glands were located between the temporomandibular joints and had contrast enhancement. Mean gross dimensions were length, 2.11 cm; width, 2.16 cm; height, 0.98 cm; and volume, 2.66 cm3. Gross measurements and CT estimates of pituitary gland length from 10-mm contiguous and overlapping slices did not differ. Gross measurements and CT estimates of pituitary gland width from 4-mm contiguous and overlapping slices did not differ. Estimates of height and volume from all CT techniques differed from gross measurements. Accuracies for CT estimates were length, 88 to 99%; width, 81 to 92%; height, 58 to 71%; and volume, 43 to 55%.

Conclusions and Clinical Relevance—Accuracy of estimates of pituitary gland dimension in horses varied with CT scanning technique; via CT, estimates of length and width of glands were more accurate than estimates of height or volume. (Am J Vet Res 2003;64:1387–1394)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To identify ventilatory protocols that yielded good image quality for thoracic CT and hemodynamic stability in cats.

Animals—7 healthy cats.

Procedures—Cats were anesthetized and ventilated via 4 randomized protocols (hyperventilation, 20 seconds [protocol 1]; single deep inspiration, positive inspiratory pressure of 15 cm H2O [protocol 2]; recruitment maneuver [protocol 3]; and hyperventilation, 20 seconds with a positive end-expiratory pressure of 5 cm H2O [protocol 4]). Thoracic CT was performed for each protocol; images were acquired during apnea for protocols 1 and 3 and during positive airway pressure for protocols 2 and 4. Heart rate; systolic, mean, and diastolic arterial blood pressures; blood gas values; end-tidal isoflurane concentration; rectal temperature; and measures of atelectasis, total lung volume (TLV), and lung density were determined before and after each protocol.

Results—None of the protocols eliminated atelectasis; the number of lung lobes with atelectasis was significantly greater during protocol 1 than during the other protocols. Lung density and TLV differed significantly among protocols, except between protocols 1 and 3. Protocol 2 TLV exceeded reference values. Arterial blood pressure after each protocol was lower than before the protocols. Mean and diastolic arterial blood pressure were higher after protocol 3 and diastolic arterial blood pressure was higher after protocol 4 than after protocol 2.

Conclusions and Clinical Relevance—Standardization of ventilatory protocols may minimize effects on thoracic CT images and hemodynamic variables. Although atelectasis was still present, ventilatory protocols 3 and 4 provided the best compromise between image quality and hemodynamic stability.

Full access
in American Journal of Veterinary Research