Magnetic resonance imaging of a canine eye with melanoma

An 8-year-old Beagle dog had exophthalmos of the left eye for the last two past months. On ophthalmoscopy, the intraocular lesion could not be evaluated due to the opacity of the cornea. Ultrasonography revealed that the eyeball was distorted in shape and shifted in position, however, the precise lesion could not be identified. On magnetic resonance (MR) imaging, the lesion was observed as hyperintense on T1-weighted and hypointense on T2-weighted images, similar to those reported in human melanoma. The lesion was histologically diagnosed to be malignant intraocular melanoma. Though this is only a case report, canine ocular melanoma may show the similar characteristic MR images as in human uveal malignant melanoma.     

Magnetic resonance imaging of feline hippocampal necrosis

The clinical, neuropathologic, and magnetic resonance (MR) imaging features in four cats with necrosis of the hippocampus and piriform lobe are described. All cats had acute generalized seizures and behavioral changes including aggression, salivation, polyphagia, and disorientation. Routine hematologic, serum chemistry, and cerebrospinal fluid analyses were normal. MR imaging abnormalities were restricted to the area of the hippocampus and piriform lobe. The lesions were T2-hyperintense, T1-hypointense, and were characterized by various degrees of contrast enhancement. Lesions were consistent with necrotizing encephalitis. Two cats were euthanized and underwent postmortem examination within a week after MR imaging due to the lack of response to antiepileptic drug therapy and progressive neuropathy. The remaining two cats lived for about four months and were then euthanized because of persistent behavioral and neurologic signs; only one of these cats underwent postmortem examination with histopathologic examination. Histopathological findings were typical of severe, diffuse, bilateral symmetric necrosis, and degeneration of neurons in the hippocampus and piriform lobe, but an etiologic agent was not apparent. This apparently unique feline syndrome, now reported in Switzerland and Italy, has no known cause at this time.     

Microbiology of the canine and feline eye

Knowledge of the microbiology of the canine and feline eye in normal and pathologic states is an important aspect of the clinician's assessment of external ocular disease. Gram-positive bacteria predominate in surveys of microbial flora in normal and diseased eyes. These same organisms are routinely isolated from skin and the upper respiratory tract. Injury to the eye may result in proliferation and potential pathogenicity of normal ocular flora. A variety of bacterial, fungal, viral, and other microbial isolates affect the diagnosis and treatment of external ocular disease.     

Magnetic resonance imaging of the normal canine thyroid gland.

The magnetic resonance (MR) imaging features of the normal canine thyroid gland were retrospectively compiled from images acquired in 44 dogs presented for a variety of diseases unrelated to the thyroid gland. The appearance of the thyroid gland on different sequences, including pre- and postcontrast T1-weighted, T2-weighted, two-dimensional gradient echo, three-dimensional T2*-weighted gradient echo and proton density weighted images, were described in different image planes. The characteristic shape, location, and intensity of thyroid lobes compared with surrounding structures made them easily detectable in all dogs. The most common location of the thyroid lobes was dorsolateral to the trachea with the maximal cross-sectional area of the lobes located ventral to C2/3 or C3 in more than 85% of the dogs. The majority of the lobes were ovoid on transverse images. An isthmus was seen in one large dog and parathyroid glands could not be seen. The mean maximal thyroid lobe diameter on transverse images was 8.1 mm, being twice the mean diameter of the common carotid artery. Considering the excellent conspicuity and characteristic appearance of the canine thyroid gland, MR imaging can be beneficial in the diagnosis of diffuse thyroid diseases, in differentiating thyroid vs. nonthyroid neck masses and in staging and treatment planning of thyroid tumors in this species.     

Diagnostic imaging of the canine and feline ear.

Radiographic evaluation of the tympanic bulla is limited. Improper obliquity or angulation of the skull for radiographs or malpositioning of the tongue can result in an inadequate study [4]. Additionally, because of the complex anatomy of the canine and feline skull, with superimposition of multiple osseous structures, radiography can result in false-negative examinations or understimation of the disease present [2]. When compared with surgical findings of 19 clinical cases of presumptive middle ear disease, false-negative radiographic findings were found in 25% of the surgically confirmed cases of otitis media [4]. Therefore, radiographs are not considered to be a highly sensitive mode of diagnosing otitis media. Radiographs may be helpful in determining lysis associated with neoplasia; however, the extent of involvement is still underestimated. In a study comparing CT and radiographic evaluation of otitis media, CT was determined to be more sensitive but less specific than radiography [11]. CT is the preferred modality for the evaluation of the tympanic bulla at our institution. This opinion may be biased by the fact that most cases are presented for recurrent or chronic otitis. Although radiography is more accessible, the availability of CT in local referral settings is increasing as opposed to being limited to university settings. After the cost (i.e., anesthesia, radiographs) and amount of time necessary to make optimum radiographic studies are taken into account, a CT study may actually be faster and more informative. Given our preference for the CT examination, the cost of the examination has been adjusted to make it more appealing to the owner and clinician. For example, a bulla CT study is only 1.3 times the cost of a radiographic bulla study. In conclusion, imaging of the ear canal can provide important information about ear disease, including unilateral or bilateral ear disease, the degree of middle or inner ear involvement, peripheral versus central vestibular disease, an infectious or inflammatory versus neoplastic process, the chronicity of the disease process, involvement of adjacent structures, and postsurgical complications.     

Magnetic resonance imaging in the diagnosis and treatment of a canine spinal cord injury

A nine-year-old female crossbred dog was presented with tetraplegia following a fall. No vertebral abnormalities were detectable on plain radiographs of the cervical spine. Magnetic resonance imaging scans revealed absence of extraparenchymal compression and an area of oedema within the cervical spinal cord, suggesting a favourable prognosis. Following nursing care and physiotherapy, the dog recovered the ability to walk, although mild neurological deficits persisted in the left limbs.     

Magnetic resonance imaging features of feline intracranial neoplasia: retrospective analysis of 46 cats

The purpose of this retrospective study was to determine the magnetic resonance imaging (MRI) characteristics of feline brain tumors and to determine whether these characteristics can be used to accurately predict the histologic diagnosis. MRI scans of 46 cats with histologically confirmed brain tumors were reviewed, including 33 meningiomas, 6 lymphomas, 4 gliomas, 2 olfactory neuroblastomas, and 1 pituitary tumor. MRI features including axial origin, shape, location, signal intensity, contrast enhancement, peritumoral edema, and mass effect were reviewed and characterized for each tumor type. Tumor shape, axial origin, contrast enhancement, and degree of peritumoral edema aided in the identification of tumor type. Meningiomas were always extra-axial and were most often ovoid with marked contrast enhancement and mild peritumoral edema. Gliomas were always intra-axial with ring enhancement and generally caused more peritumoral edema than other tumors. The brain tumor was detected on MRI in 45 (98%) cats. Two blinded independent reviewers correctly identified 82% of all of the tumor types on the basis of MRI appearance alone. Thus, MRI is an excellent diagnostic tool for the detection of brain tumors in cats, and it provides important information to aid in the diagnosis of tumor type.     

Magnetic resonance imaging and pathological findings in a case of canine idiopathic eosinophilic meningoencephalitis

A case of idiopathic eosinophilic meningoencephalitis in a six-month-old male Maremma shepherd dog is reported. The dog was referred with a four month history of progressive weakness and depression with loss of trained habits. Tendency to recumbency, disorientation, visual impairment, bilaterally decreased menace response and hindlimb conscious proprioception deficits were detected. Magnetic resonance imaging showed a diffuse hypointense signal involving the cerebral grey matter with enlargement of the cerebral sulci on T1-weighted and fast fluid-attenuated inversion recovery (FLAIR) sequences consistent with a diffuse necrosis or atrophy of the cortical grey matter. Histological examination revealed severe inflammatory infiltration mainly composed of eosinophils and macrophages in the subarachnoid space and in the superficial layer of the cerebral cortex where parenchymal rarefaction and necrosis of neurones were also evident. No parasites, cysts or fungi were detected, and an immunologically mediated disorder was suspected. Magnetic resonance imaging may represent a useful diagnostic tool to differentiate idiopathic eosinophilic meningoencephalitis from other inflammatory brain diseases of young dogs.     

Ultrasonography of the eye and orbit

The eye and orbit are excellent subjects for ultrasonic evaluation. Examination and interpretation are relatively simple procedures. The normal ultrasonic anatomy of the eye and orbit is presented. Some examples of ocular and orbital pathology are discussed also.     

Magnetic resonance imaging of the normal bovine digit

The purpose of this study was defining the normal structures of the digits and hoof in Holstein dairy cattle using Magnetic Resonance Image (MRI). Transverse, Sagital and Dorsoplantar MRI images of three isolated cattle cadaver digits were obtained using Gyroscan T5-NT a magnet of 0.5 Tesla and T1 Weighted sequence. The MRI images were compared to corresponding frozen cross-sections and dissect specimens of the cadaver digits. Relevant anatomical structures were identified and labeled at each level. The MRI images provided anatomical detail of the digits and hoof in Holstein dairy cattle. Transversal images provided excellent depiction of anatomical structures when compared to corresponding frozen cross-sections. The information presented in this paper would serve as an initial reference to the evaluation of MRI images of the digits and hoof in Holstein dairy cattle, that can be used by radiologist, clinicians, surgeon or for research propose in bovine lameness.     

Nuclear imaging and radiation therapy in canine and feline thyroid disease.

The indications, techniques, and expectations for radionuclide diagnostic studies on canine and feline thyroid glands are presented. In addition, the considerations surrounding radioiodine or external beam radiotherapy for benign and malignant thyroid disease are reviewed. The intent of this article is to familiarize primary care veterinarians with the utility of and outcome of the ionizing radiation-based diagnostic and therapeutic techniques for assessing and treating canine and feline thyroid disease.     

Magnetic resonance imaging of hepatic neoplasms in the rat

Magnetic resonance imaging (MRI) at microscopic resolution was done on a live rat that had chemically induced hepatic neoplasms. Beginning at the anterior aspect of the liver, 16 contiguous transaxial slices (each 1.25 mm thick) were produced using three-dimensional Fourier transform sequences. The rat had been treated with diethylnitrosamine (200 mg/kg) at 70 days of age, and, subsequently, received periodic implants of 17a-ethynylestradiol for 60 weeks. Carr-Purcell-Meiboom-Gill (CPMG) sequences (repetition time = 2,000 and echo time = 20, 40, 60, 80 ms) were done to give quantitative measures of spin-spin relaxation times (T2). Pixel-by-pixel curve fitting from these multiple images yielded calculated T2 images. Histologic evaluation of three abnormal areas in the liver revealed solid and cystic hepatocellular adenomas. Although lesions were evident in early-echo images of the CPMG sequence, they were more apparent in the late-echo images. This was consistent with longer T2 relaxation times for the lesions. The voxels of dimensions (230 x 230 x 1,250 microns) permitted resolution of volume elements less than 0.07 mm3. This in turn permitted clear delineation of focal lesions less than 3 mm in diameter. The potential for MRI at microscopic resolution in toxicologic research is clearly demonstrated.     

Ultrasonographic, computed tomographic and magnetic resonance imaging anatomy of the normal canine stifle joint

Ultrasonographic (US), magnetic resonance (MR) and computed tomographic (CT) images of normal canine stifle joints were obtained and compared with plastinated cross-sectional slices of cadaver specimens from the same dogs. The bony and articular structures were identified and correlated with the three diagnostic imaging modalities. These results provide an atlas of normal cross-sectional US, MR and CT anatomy of the canine stifle, which can be used for the interpretation of stifle images from any of these imaging modalities.     

Magnetic resonance spectroscopy of the canine brain at 3.0 T and 7.0 T

The purpose of this study was to evaluate the feasibility of proton magnetic resonance spectroscopy (1H MRS) to study the concentration of metabolites in the brain of dogs at 3.0 and 7.0 T. Four healthy male beagles were scanned using 3.0 T and 7.0 T human magnetic resonance imaging (MRI) units. The results obtained showed that all dogs had excellent quality spectra for a small (1 cm3) and large (8 cm3) voxel at 3.0 T, whereas only 2 dogs had high quality spectra at 7.0 T due to insufficient water suppression. 1H MRS at 3.0 T appears to be a reliable method to study metabolite concentrations in the canine brain. The development of more advanced water suppression techniques is necessary to improve the results at 7.0 T.