Magnetic resonance imaging characterization of canine splenic lesions

Introduction:  Splenic lesions are a common finding in veterinary medicine and typically 1/2 to 2/3 of these lesions are malignant. Due to the limited accuracy of ultrasound, unnecessary exploratory surgeries/biopsies may be performed for benign lesions and treatment may be delayed for malignant ones. Splenic lesions are rare in people. MR imaging, with its inherently high soft tissue contrast, is efficacious in imaging the human spleen. We have previously demonstrated the efficacy of MRI to differentiate canine hepatic lesions. In that study 8 splenic lesions were all accurately characterized. This current study represents a further evaluation of splenic lesions.
Methods:  In this prospective study, 27 dogs with splenic lesions were accrued. Histopathological/cytological confirmation of lesions occurred either before or shortly after imaging. MRI clinicians were blinded to histopathology results. MR (General Electric, 1.5 Tesla) images using a variety of sequences were obtained before and after intravenous administration of gadolinium.
Results:  32 lesions (9 malignant, 23 benign) were evaluated in 27 dogs. Lesions were confirmed via histopathology (n = 20) or cytology (n = 12). Benign lesions included, EMH (n = 7), hematoma/hemorrhage (n = 5), lymphoid hyperplasia (n = 9), and hemangioma (n = 2). Malignant lesions included anaplastic sarcoma (n = 3), malignant histiocytosis (n = 2), hemangiosarcoma (n = 2), plasma cell tumor (n = 1) and adenocarcinoma (n = 1). The overall accuracy in differentiating benign from malignant lesions was 88%(29/32 lesions). The overall sensitivity and specificity were 100%(95% CI, 66–100) and 87%(95% CI 66–97).
Conclusions:  Based upon these results, MRI is both sensitive and specific in distinguishing between malignant and benign splenic lesions.     

Magnetic resonance imaging features of canine gliomatosis cerebri

A retrospective, case series study was undertaken to identify magnetic resonance imaging (MRI) characteristics of gliomatosis cerebri in dogs. Fourteen dogs were included by review of histopathological records and contemporaneous MRI. On MRI, all lesions presented as ill‐defined, intraaxial lesions within the left and right forebrain hemispheres with involvement of white and gray matter. Lesions presented as hyperintense areas on T2‐weighted and FLAIR sequences and as hypointense or isointense areas on T1‐weighted images, with mild parenchymal contrast enhancement in three dogs. Signal changes were noted in three to 10 cerebral lobes. Other most commonly affected structures were the thalamus (13), caudate nucleus (13), interthalamic adhesion (11), hypothalamus (11), callosal commissure (10), hippocampus (9), and quadrigeminal plate (8). Abnormalities within the caudal fossa were noted in 10 dogs. Solid tumor portions were identified in five dogs. The histopathological examination demonstrated in all dogs a widespread diffuse infiltration with neoplastic glial cells in white and gray matter with meningeal infiltration. Comparison between MRI and histopathology showed that all areas with signal changes on MRI corresponded to diffuse and dense infiltration with neoplastic cells. The signal intensity on T2‐weighted and FLAIR images reflected the density of neoplastic cells. In all dogs, MRI underestimated lesion extent and meningeal infiltration. Involvement of the caudal fossa was not seen on MRI in three dogs. Despite this, MRI allowed identification of lesions extending into at least three cerebral lobes and therefore satisfying the criteria used for diagnosis of diffuse glioma with gliomatosis cerebri growth pattern in humans.     

Magnetic resonance imaging of canine mast cell tumors

Mast cell tumors (MCT) are the most common cutaneous tumors in dogs. Our purpose was to describe the magnetic resonance (MR) imaging characteristics of cutaneous MCT and to identify imaging characteristics that allow differentiation of metastatic from normal lymph nodes. Eight dogs with a total of nineMCT were imaged as were their presumed draining and associated contralateral lymph nodes. The signal intensity of tumors and lymph nodes was compared to adjacent musculature. On T2-W images, 7/9 MCT were hyperintense to muscle and 2/9 were isointense. On T1-W images, 8/9 MCT were isointense and 1/9 were mildly hypointense. All tumors were strongly contrast enhancing; 5/9 were homogeneous and 4/9 heterogeneous in their enhancement patterns. Six lymph node pairs were included in the evaluation (five sentinel lymph nodes with metastases, one without, and six contralateral lymph nodes). Metastatic lymph nodes were significantly larger than their contralateral lymph nodes (P = 0.039). All lymph nodes were isointense on T1-W images and hyperintense on T2-W images. 5/5 metastatic and 2/7 normal lymph nodes were heterogeneously T2-hyperintense. All lymph nodes were moderately to strongly contrast enhancing. 4/5 metastatic and 2/7 normal lymph nodes had heterogeneous enhancement patterns. While heterogeneity was more common in metastatic than in normal lymph nodes, this difference was not significant (P = 0.058 for T2-W images; P = 0.234 for postcontrast images). MR imaging may be useful in the presurgical evaluation and clinical staging of cutaneous MCT.     

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.     

Magnetic resonance imaging features of canine incomplete humeral condyle ossification

Incomplete ossification of the humeral condyle (IOHC) is characterized by an intracondylar fissure located where the intercondylar physis is present in growing dogs. Its radiologic and computed tomographic features have been described but the magnetic resonance (MR) features have not been characterized. Our purpose was to further describe the range of MRappearances of IOHC, to assess the diagnostic capability of MRrelative to radiology, and to determine whether MRis able to identify the disease before a fissure forms. Thirty-eight elbow MRscans and radiographs, when available, were reviewed and divided into three groups. In Group 1 (affected elbows, n = 22), there was an intracondylar defect on MRwith variable appearance; the defect was not visible radiographically in 32% of the elbows. The main difference between Group 2 (nonaffected elbows, n = 6) and Group 3 (contralaterals to IOHC or to condylar fracture, without fissure, n = 10) was the appearance of the humeral condyle in short tau inversion recovery (STIR) sequences: all elbows in Group 2 had a homogeneous humeral condyle, whereas all but one in Group 3 were heterogeneous. One dog in Group 3 developed a complete condylar fissure 7 months after the first examination, when no evidence of an intracondylar defect had been detected. The MRappearance of IOHC is variable and a heterogeneous humeral condyle in STIR images without a clear defect may warn of the possibility for the subsequent development of a condylar fissure.     

Magnetic resonance imaging findings in acute canine distemper virus infection

Demyelination is the prominent histopathological hallmark in the acute stage of canine distemper virus infection. Magnetic resonance imaging is an important diagnostic tool in human beings to determine demyelination in the brain, for example in multiple sclerosis. Five young dogs with clinically suspected canine distemper virus infection were subjected to magnetic resonance imaging of the brain and histopathological and immunohistochemical examinations. Hyperintense lesions and loss of contrast between grey and white matter were detected in T2-weighted images in the cerebellum and/or in the brainstem of three dogs, which correlated with demyelination demonstrated in histopathological examination. Furthermore, increased signal intensities in T2-weighted images were seen in the temporal lobe of four dogs with no evidence of demyelination. Magnetic resonance imaging seems to be a sensitive tool for the visualisation of in vivo myelination defects in dogs with acute canine distemper virus infection. Postictal oedema and accumulation of antigen positive cells have to be considered an important differential diagnosis.     

Magnetic resonance imaging technique for the examination of canine mammary tumours

The aim of this study was to adapt the human magnetic resonance imaging (MRI) sequences for use in the routine examination of canine mammary glands. MRI was performed on 10, middle- to old-aged dogs of different breeds. It was found that T1- and T2-weighted spin echo, short T1 inversion recovery sequences and a gradient echo (GE) dynamic T1-weighted measurement made in the coronal and transversal planes were the most informative MR diagnostic methods for imaging canine mammary tumours. The static MR technique is the most detailed imaging modality for differentiating the tissue types in the substance of the mammary gland. The MRI findings were in close relationship with the histological result (five malignant mixed tumours and five cases of invasive ductal carcinoma). Using the GE dynamic contrast-enhanced sequence the morphological patterns as well as the kinetic parameters proved to be malignant. By the dynamic measurement technique initial information was obtained on the contrast enhancing properties, which are valuable factors during in vivo staging and in the prognostic work.     

Magnetic resonance imaging of the canine and feline eye, orbit, and optic nerves and its clinical application

The purpose of this study was to investigate magnetic resonance imaging of the normal canine and feline eye, orbit and optic nerves using proton density-weighted, T₁-weighted and T₂-weighted images. The clinical application of magnetic resonance imaging in veterinary ophthalmology was also investigated using three clinical cases: a feline orbital melanoma, a feline optic nerve meningioma, and a canine orbital fibrosarcoma. Gadolinium diethylenetriamine pentaacetic acid enhanced magnetic resonance imaging was completed on the case of feline optic nerve meningioma. Magnetic resonance imaging provides excellent anatomical detail of the canine and feline eye, orbit, and optic nerves due to its superior soft tissue contrast, and its multiplanar and multislice imaging capability. Therefore it is of value for diagnostic imaging of some ophthalmic and neuro-ophthalmic conditions in the dog and cat.     

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 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.     

Magnetic resonance imaging in a dog with a choroid plexus carcinoma

Magnetic resonance imaging was used ante mortem to confirm the anatomic location of an intracranial lesion in a dog with neurological signs. Necropsy revealed the lesion to be a choroid plexus carcinoma with thalamic invasion. A review of the literature on choroid plexus carcinomas in the dog is included.     

Magnetic resonance imaging and pathological findings in a cat with brain contusions

Necropsy was performed on a mongrel male cat of unknown age weighing 1.3 kg, which probably encountered a traffic accident. Gross pathological examination of the brain revealed reddish colour of the right cerebral hemisphere and haemorrhages on the surface of the right frontal lobe to temporal lobe. Histologically, there was diffuse vacuolation in the cortex of the right frontal lobe and extensive haemorrhages in the base of brain. These histopathological findings were consistent with areas of abnormal signals found on post-mortem magnetic resonance imaging (MRI). In this study, the MRI findings were identical to that reported in human cases of head trauma as well as histopathological changes.     

Magnetic resonance imaging findings of hepatic encephalopathy in a dog with a portosystemic shunt

A 6-year-old ShihTzu presented with tonic-clonic cluster seizure. T2-weighted magnetic resonance (MR) images showed bilateral diffuse hyperintense lesions at the cerebral cortex with enlarged sulci. Computed tomography revealed a portosystemic shunt (PSS) and azygos continuation. Based on the clinical signs, blood examinations and diagnostic images, the dog was diagnosed with hepatic encephalopathy secondary to PSS. The neurologic signs were gradually improved after medical therapy for hyperammonemia. This is the first report of hyperintensity of the cerebral cortex on T2-weighted MR images associated with acute hepatic encephalopathy in a dog.