OBJECTIVE To predict histologic grade of meningiomas in dogs via texture analysis (TA) of MRI scans of the brain and spinal cord. SAMPLE 58 sets of MRI scans of the brain and spinal cord of dogs with histologically diagnosed meningioma. PROCEDURES MRI sequences were divided into a training set and a test set, and results of histologic assessment were obtained. Tumors were histologically grouped as benign (stage I) or atypical-anaplastic (stage II or III). Texture analysis was performed by use of specialized software on T2-weighted (T2W) and pre- and postcontrast T1-weighted (T1W) images. A set of 30 texture features that provided the highest discriminating power between the 2 histologic classes in the training set was automatically selected by the TA software. Linear discriminant analysis was performed, and the most discriminant factor (MDF) was calculated. The previously selected texture features were then used for linear discriminant analysis of the test set data, and the MDF was calculated. RESULTS For the training set, TA of precontrast T1W images provided the best diagnostic accuracy; a cutoff MDF of < 0.0057 resulted in a sensitivity of 97.4% and specificity of 95.0% for discriminating benign from atypical-anaplastic meningiomas. Use of postcontrast T1W and T2W images yielded poorer diagnostic performances. Application of the MDF cutoff calculated with the training set to the MDF calculated with the test set provided a correct classification rate of 96.8% for precontrast T1W images, 92.0% for postcontrast T1W images, and 78.9% for T2W images. CONCLUSIONS AND CLINICAL RELEVANCE Findings supported the potential clinical usefulness of TA of MRI scans for the grading of meningiomas in dogs.

OBJECTIVE To compare stroke volume (SV) calculated on the basis of cardiac morphology determined by MRI and results of phase-contrast angiography (PCA) of ventricular inflow and outflow in dogs. ANIMALS 10 healthy Beagles. PROCEDURES Cardiac MRI was performed twice on each Beagle. Cine gradient echo sequences of both ventricles in short-axis planes were used for morphological quantification of SVs by assessment of myocardial contours. From the long-axis plane, SVs in 4-chamber and left ventricular 2-chamber views were acquired at end diastole and end systole. For calculation of SV on the basis of blood flow, PCA was performed for cardiac valves. RESULTS Mean ± SD values for SV quantified on the basis of blood flow were similar in all valves (aortic, 17.8 ± 4.1 mL; pulmonary, 17.2 ± 5.4 mL; mitral, 17.2 ± 3.9 mL; and tricuspid, 16.9 ± 5.1 mL). Morphological quantification of SV in the short-axis plane yielded significant differences between left (13.4 ± 2.7 mL) and right (8.6 ± 2.4 mL) sides. Morphological quantification of left ventricular SV in the long-axis plane (15.2 ± 3.3 mL and 20.7 ± 3.8 mL in the 4- and 2-chamber views) yielded variable results, which differed significantly from values for flow-based quantification, except for values for the morphological 4-chamber view and PCA for the atrioventricular valves, for which no significant differences were identified. CONCLUSIONS AND CLINICAL RELEVANCE In contrast to quantification based on blood flow, calculation on the basis of morphology for the short-axis plane significantly underestimated SV, probably because of through-plane motion and complex right ventricular anatomy.

OBJECTIVE To determine anatomic reference points for 4 turtle species and to evaluate data on relative anatomic dimensions, signal intensities (SIs), and position of selected organs within the coelomic cavity by use of MRI. ANIMALS 3 turtle cadavers (1 red-eared slider [Trachemys scripta elegans], 1 yellow-bellied slider [Trachemys scripta scripta], and 1 Coastal plain cooter [Pseudemys concinna floridana]) and 63 live adult turtles (30 red-eared sliders, 20 yellow-bellied sliders, 5 Coastal plain cooters, and 8 hieroglyphic river cooters [Pseudemys concinna hieroglyphica]). PROCEDURES MRI and necropsy were performed on the 3 turtle cadavers. Physical examination, hematologic evaluation, and whole-body radiography were performed on the 63 live turtles. Turtles were sedated, and MRI in transverse, sagittal, and dorsal planes was used to measure organ dimensions, position within the coelomic cavity, and SIs. Body positioning after sedation was standardized with the head, neck, limbs, and tail positioned in maximum extension. RESULTS Measurements of the heart, liver, gallbladder, and kidneys in sagittal, transverse, and dorsal planes; relative position of those organs within the coelom; and SIs of the kidneys and liver were obtained with MRI and provided anatomic data for these 4 turtle species. CONCLUSIONS AND CLINICAL RELEVANCE MRI was a valuable tool for determining the position, dimensions, and SIs of selected organs. Measurement of organs in freshwater chelonians was achievable with MRI. Further studies are needed to establish reference values for anatomic structures in turtles. Results reported here may serve as guidelines and aid in clinical interpretation of MRI images for these 4 species.

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 acquire MRI diffusion data (apparent diffusion coefficient [ADC] and fractional anisotropy [FA] values, including separate measures for gray and white matter) at 3.0 T for multiple locations of the brain of neurologically normal dogs. ANIMALS: 13 neurologically normal dogs recruited from a group of patients undergoing tibial plateau leveling osteotomy. PROCEDURES: MRI duration ranged from 20 to 30 minutes, including obtaining preliminary images to exclude pathological changes (T2-weighted fluid-attenuated inversion recovery transverse and dorsal images) and diffusion-weighted images., RESULTS: Globally, there were significant differences between mean values for gray and white matter in the cerebral lobes and cerebellum for ADC (range of means for gray matter, 0.8349 × 10(−3) s/mm2 to 0.9273 × 10(−3) s/mm2; range of means for white matter, 0.6897 × 10(−3) s/mm2 to 0.7332 × 10(−3) s/mm2) and FA (range of means for gray matter, 0.1978 to 0.2364; range of means for white matter, 0.5136 to 0.6144). These values also differed among cerebral lobes. In most areas, a positive correlation was detected between ADC values and patient age but not between FA values and patient age. CONCLUSIONS AND CLINICAL RELEVANCE: Cerebral interlobar and cerebellar diffusion values differed significantly, especially in the gray matter. Information about diffusion values in neurologically normal dogs may be used to diagnose and monitor abnormalities and was the first step in determining the clinical use of diffusion imaging. This information provided an important starting point for the clinical application of diffusion imaging of the canine brain.

OBJECTIVE To evaluate the usefulness of diffusion and perfusion MRI of the cerebrum in cats with familial spontaneous epilepsy (FSECs) and identify microstructural and functional deficit zones in affected cats. ANIMALS 19 FSECs and 12 healthy cats. PROCEDURES Diffusion-weighted, diffusion tensor, and perfusion-weighted MRI of the cerebrum were performed during interictal periods in FSECs. Imaging findings were compared between FSECs and control cats. Diffusion (apparent diffusion coefficient and fractional anisotropy) and perfusion (relative cerebral blood volume [rCBV], relative cerebral blood flow [rCBF], and mean transit time) variables were measured bilaterally in the hippocampus, amygdala, thalamus, parietal cortex gray matter, and subcortical white matter. Asymmetry of these variables in each region was also evaluated and compared between FSECs and control cats. RESULTS The apparent diffusion coefficient of the total amygdala of FSECs was significantly higher, compared with that of control cats. The fractional anisotropy of the right side and total hippocampus of FSECs was significantly lower, compared with that of control cats. The left and right sides and total hippocampal rCBV and rCBF were significantly lower in FSECs than in control cats. The rCBV and rCBF of the parietal cortex gray matter in FSECs were significantly lower than in control cats. CONCLUSIONS AND CLINICAL RELEVANCE In FSECs, diffusion and perfusion MRI detected microstructural changes and hypoperfusion (lowered function) in the cerebrum during interictal periods from that of healthy cats. These findings indicated that diffusion and perfusion MRI may be useful for noninvasive evaluation of epileptogenic foci in cats.

OBJECTIVE To use MRI and CT to compare the amount of tissue damage (soft tissue and bone) to the heads of goats after administration of a nonpenetrating or penetrating captive bolt. ANIMALS Cadavers of twelve 1- to 5-year-old mixed-breed goats that had been euthanized with an overdose of pentobarbital as part of an unrelated study. PROCEDURES Cadavers were randomly assigned to receive a nonpenetrating (n = 6) or penetrating (6) captive bolt. The head of 1 cadaver was imaged via CT and MRI. The muzzle of a device designed to administer either a penetrating or nonpenetrating captive bolt was then placed flush on the dorsal midline of each head at the level of the external occipital protuberance (poll) and aimed downward toward the cranialmost portion of the intermandibular space, and the assigned bolt was administered. Heads were removed, and CT and MRI of each head were performed. After imaging, each skull was transected along the sagittal plane to permit gross evaluation of central nervous tissue and obtain digital photographic images. In addition, 1 head that received a nonpenetrating captive bolt was further evaluated via blunt dissection and removal of adnexa from the external surface of the calvarium. RESULTS MRI, CT, and dissection of skulls revealed severe skeletal and soft tissue damage after impact with the penetrating and nonpenetrating captive bolts. CONCLUSIONS AND CLINICAL RELEVANCE The nonpenetrating captive bolt appeared to cause damage similar to that of the penetrating captive bolt in the cranium and soft tissues of the head in caprine cadavers. This damage suggested that administration of a nonpenetrating captive bolt as described here may be an acceptable method of euthanasia in goats.