OBJECTIVE To characterize and compare MRI susceptibility artifacts related to titanium and stainless steel monocortical screws in the cervical vertebrae and spinal cord of canine cadavers.
SAMPLE 12 canine cadavers.
PROCEDURES Cervical vertebrae (C4 and C5) were surgically stabilized with titanium or stainless steel monocortical screws and polymethylmethacrylate. Routine T1-weighted, T2-weighted, and short tau inversion recovery sequences were performed at 3.0 T. Magnetic susceptibility artifacts in 20 regions of interest (ROIs) across 4 contiguous vertebrae (C3 through C6) were scored by use of an established scoring system.
RESULTS Artifact scores for stainless steel screws were significantly greater than scores for titanium screws at 18 of 20 ROIs. Artifact scores for titanium screws were significantly higher for spinal cord ROIs within the implanted vertebrae. Artifact scores for stainless steel screws at C3 were significantly less than at the other 3 cervical vertebrae.
CONCLUSIONS AND CLINICAL RELEVANCE Evaluation of routine MRI sequences obtained at 3.0 T revealed that susceptibility artifacts related to titanium monocortical screws were considered mild and should not hinder the overall clinical assessment of the cervical vertebrae and spinal cord. However, mild focal artifacts may obscure small portions of the spinal cord or intervertebral discs immediately adjacent to titanium screws. Severe artifacts related to stainless steel screws were more likely to result in routine MRI sequences being nondiagnostic; however, artifacts may be mitigated by implant positioning.
Objective—To compare long-term results of radiotherapy
alone versus radiotherapy followed by exenteration
of the nasal cavity in dogs with malignant
Animals—53 dogs with malignant intranasal neoplasia.
Procedure—All dogs underwent radiotherapy consisting
of administration of 10 fractions of 4.2 Gy each
on consecutive weekdays. For dogs in the surgery
group (n = 13), follow-up computed tomography was
performed, and dogs were scheduled for surgery if
persistent or recurrent tumor was seen.
Results—Perioperative complications for dogs that
underwent surgery included hemorrhage requiring
transfusion (2 dogs) and subcutaneous emphysema
(8). Rhinitis and osteomyelitis-osteonecrosis occurred
significantly more frequently in dogs in the radiotherapy
and surgery group (9 and 4 dogs, respectively)
than in dogs in the radiotherapy-only group (4 and 3
dogs, respectively). Two- and 3-year survival rates
were 44% and 24%, respectively, for dogs in the
radiotherapy group and 69% and 58%, respectively,
for dogs in the surgery group. Overall median survival
time for dogs in the radiotherapy and surgery group
(47.7 months) was significantly longer than time for
dogs in the radiotherapy-only group (19.7 months).
Conclusions and Clinical Relevance—Results suggest
that exenteration of the nasal cavity significantly
prolongs survival time in dogs with intranasal neoplasia
that have undergone radiotherapy. Exenteration after
radiotherapy may increase the risk of chronic complications.
(J Am Vet Med Assoc 2005;227:936–941)
Objective—To determine intra- and interobserver variability of 2 veterinary radiologists and 2 veterinary general practitioners for detection of pulmonary nodules in standard and inverted (reversed grayscale) displays of digital thoracic radiographs of dogs.
Sample—114 sets of 3-view (right lateral, left lateral, and ventrodorsal or dorsoventral views) digital thoracic radiographs from 114 dogs.
Procedures—2 experienced board-certified veterinary radiologists and 2 experienced veterinary general practitioners individually evaluated 114 randomized sets of radiographs. Pulmonary nodules were present in radiographs of 60 of 114 dogs. Each reviewer examined all images in standard or inverted display mode and scored nodule detection on a confidence scale of 1 to 5. After ≥ 2 months, the same individuals evaluated the same images in the remaining display mode. Intraobserver agreement for each display mode was determined via a κ statistic; results between the 2 groups of reviewers were compared via receiver operator curve analysis.
Results—There was no significant intraobserver variability in pulmonary nodule detection between the 2 display modes. Detection accuracy for board-certified radiologists was significantly greater than that of veterinary general practitioners for both display modes. Near-perfect intraobserver agreement was detected between the 2 display modes for board-certified radiologists, whereas moderate to slight intraobserver agreement was detected for the veterinary general practitioners.
Conclusions and Clinical Relevance—Detection of pulmonary nodules in digital thoracic radiographs was comparable, whether a standard or inverted mode was used for evaluations. However, the board-certified radiologists had greater detection accuracy than did veterinary general practitioners.
To assess whether cardiac MRI or various biomarkers can be used to detect myocardial ischemia and fibrosis in dogs with cardiomegaly secondary to myxomatous mitral valve disease (MMVD).
6 dogs with cardiomegaly secondary to naturally occurring stage B2 MMVD being treated only with pimobendan with or without enalapril and 6 control dogs with no cardiac disease. All dogs were ≥ 5 years old with no systemic illness.
Serum cardiac troponin I and concentrations were measured, and dogs were anesthetized for cardiac MRI with ECG-triggered acquisition of native T1- and T2-weighted images. Gadolinium contrast was administered to evaluate myocardial perfusion and late gadolinium enhancement (LGE). Mean T1 and T2 values and regions of LGE were measured with dedicated software. Extracellular volume (ECV) was estimated on the basis of Hct and T1 values of myocardium and surrounding blood. Subjective analysis for myocardial perfusion deficits was performed.
Dogs with MMVD had significantly (P = .013) higher cardiac troponin I concentrations than control dogs, but galectin-3 concentrations did not differ (P = .08) between groups. Myocardial fibrosis was detected in 4 dogs with MMVD and 3 control dogs; no dogs had obvious myocardial perfusion deficits. Native T1 and T2 values, postcontrast T1 values, and ECV values were not significantly different between groups (all P > .3).
Results suggest that some dogs with cardiomegaly secondary to MMVD may not have clinically relevant myocardial fibrosis.