Diagnostic utility of computed tomography imaging in equine intracranial conditions

Reasons for performing study: The use of computer tomography (CT) and contrast‐enhanced CT (CCT) to image the head is common. However, the validity of CT as a neurodiagnostic indicator of intracranial diseases in horses is unknown. Objective: To define the validity of CT and CCT in horses with suspected intracranial disorders. Methods: The validity of CT imaging was estimated by comparing clinical, clinicopathological and histopathological findings to CT findings in 15 horses presented for intracranial disorders, for which pre‐ and post contrast CT images and post mortem examination of the brain and skull were reviewed. Post mortem examination (gross and histopathological examination) was considered as the gold standard; and sensitivity, specificity, predictive values, likelihood ratios, and pre‐ and post test probabilities were calculated. Results: All horses had abnormal neurological examinations on admission. Computer tomography imaging identified intracranial lesions in 8 horses, and included masses (oligodendroglioma, adenocarcinoma and cholesterinic granulomas), acute haemorrhage and skull fractures. Computer tomography imaging failed to identify intracranial lesions in 6 cases, which included meningitis, meningoencephalitis and nonacute haemorrhage. Lesions not recognised by CT were also not evident on gross examination but were identified by histopathological examination of the brain. Post mortem examination of the brain and skull was unremarkable in one horse, for which cranial CT imaging was normal (specificity, 100%). Therefore, the odds of having an intracranial lesion after an abnormal CT were very high. In contrast, there was a moderate sensitivity (57.1%, 95% confidence interval: 29.6–81.2). Conclusions and potential relevance: CT was an excellent neurodiagnostic tool in identifying skull fractures, intracranial space‐occupying lesions (e.g. neoplasia) and acute haemorrhage and allows to rule in intracranial disorders. However, CT showed limited sensitivity in identifying inflammatory disorders and small parenchymal lesions in the equine brain, which was not further detectable after contrast administration.     

Comparisons of computed tomography, contrast-enhanced computed tomography and standing low-field magnetic resonance imaging in horses with lameness localised to the foot. Part 2: Lesion identification

Reasons for performing study: No previous study compares computed tomography (CT), contrast‐enhanced computed tomography (CECT) and standing low‐field magnetic resonance imaging (LFMRI) to detect lesions in horses with lameness localised to the foot. This study will help clinicians understand the limitations of these techniques. Objectives: To determine if CT, CECT and LFMRI would identify lesions within the distal limb and document discrepancies with lesion distribution and lesion classification. Methods: Lesions in specific structures identified on CT and MR images of feet (31 limbs) from the same horse were reviewed and compared. Distributions of lesions were compared using a Chi‐squared test and techniques analysed using the paired marginal homogeneity test for concordance. Results: Lesions of the deep digital flexor tendon (DDFT) were most common and CT/CECT identified more lesions than LFMRI. Deep digital flexor tendon lesions seen on LFMRI only were frequently distal to the proximal extent of the distal sesamoid and DDFT lesions seen on CT/CECT only were frequently proximal to the distal sesamoid. Lesions identified on LFMRI only were core (23.3%) or splits (43.3%), whereas lesions identified only on CT were abrasions (29.8%), core (15.8%), enlargement (15.8%) or mineralisation (12.3%). Contrast‐enhanced CT improved lesion identification at the DDFT insertion compared to CT and resulted in distal sesamoidean impar ligament and collateral sesamoidean ligament vascular enhancement in 75% of cases. Low‐field MRI and CT/CECT failed to identify soft tissue mineralisation and bone oedema, respectively. Conclusions and potential relevance: Multiple lesions are detected with CT, CECT and LFMRI but there is variability in lesion detection and classification. LFMRI centred only on the podotrochlear apparatus may fail to identify lesions of the pastern or soft tissue mineralisation. Computed tomography may fail to identify DDFT lesions distal to the proximal border of the distal sesamoid.     

USE OF CONTRAST-ENHANCED COMPUTED TOMOGRAPHY TO ASSESS ANGIOGENESIS IN DEEP DIGITAL FLEXOR TENDONOPATHY IN A HORSE

We compared contrast-enhanced computed tomography (CT) and high field magnetic resonance (MR) imaging in a horse with deep digital flexor tendonopathy. Lesions in the distal extremity were documented grossly and histopathologically. In contrast-enhanced CT, the deep digital flexor tendon lesions were markedly contrast enhancing with evidence of angiogenesis in the core and dorsal border lesions. The lesion morphology was clearly delineated on MR imaging, but without contrast media angiogenesis cannot be identified. Gross examination, histopathologic examination, and CD31 immunohistochemistry confirmed the tendonopathy and an increased presence of small blood vessels. In this horse, deep digital flexor tendon lesions appeared similarly on contrast-enhanced CT and MR imaging. Contrast-enhanced CT may be an alternative to MR imaging for assessing tendon and ligament injury in the digit of the horse.     

COMPUTED TOMOGRAPHY OF BRAIN TUMORS IN THE CAUDAL FOSSA OF THE DOG*

Computed tomography (CT) was used to investigate brain tumors in the caudal fossa of three dogs. Changes detected by CT included compression or distortion of cerebrospinal fluid spaces within the caudal fossa, and changes in parenchymal density before and after intravenous injection of a nondiffusible, iodinated contrast medium. CT provided information regarding tumor size, location, character, and relationships with normal caudal fossa structures. It was concluded that CT offered advantages over technics currently in use for diagnosis and assessment of caudal fossa lesions in the dog.     

Computed tomographic characteristics of cavitary pulmonary adenocarcinoma in 3 dogs and 2 cats

Cavitary pulmonary lesions can result from the localized breakdown of pulmonary parenchyma or be caused by the expulsion of a necrotic part of a mass. The objectives of this study were to describe the clinical and computed tomographic characteristics for cases of cavitary pulmonary adenocarcinoma and find associations between the features and those identified in human pulmonary cavitary soft tissue lesions. Five cases were identified that had a cavitary pulmonary mass on thoracic computed tomography (CT) and histopathology of the lesions. Three dogs and 2 cats had cavitary pulmonary adenocarcinoma. Common features of CT in these cases included lesions in the caudal lung lobes, lobular and spiculated lesion margins, air bronchograms within the mass, pleural tags, heterogeneous contrast enhancement, and ground glass opacity in the surrounding parenchyma. The findings of this case series suggest there are similarities in the CT characteristics of malignancy in human and animal cavitary pulmonary masses.     

DIFFERENTIATION OF NEOPLASTIC FROM NON-NEOPLASTIC LESIONS IN DOG BRAIN USING QUANTITATIVE CT

The uptake and washout of iodinated contrast medium in neoplastic and non-neoplastic lesions in the dog brin was quantified using computed tomography. The magnitude of tissue contrast enhancement was measured during and up to 15 minutes following an intravenous infusion of contrast medium. Compartmental analysis was used to obtain rate contants for contrast medium movement into and out of brain lesions. In non-glioma tumors, contrast enhancement was maximum during the infusion and the rate of contrast washout was comparable to that measured in the normal brain. Mixed gliomas also showed maximum enhancement during infusion, but there was no washout of contrast. Contrast enhancement in radiation-induced brain damage and cystic encephalomalacia secondary to tumor compression continued to increase for 5–15 minutes after infusion; rate constants in these non-tumor lesions were different from all tumors studied. Hyperthermia-induced lesions had comparable rate constants for contrast washin and washout. These results indicate that kinetic CT studies provide a non-invasive measure of permeability differences between lesions, may be useful in differentiating certain types of intracranial lesions, and may provide an effective method for patient follow-up after treatment.     

Injection of the insertion of the deep digital flexor tendon in horses using radiographic guidance

Insertional tendinopathies of the DDFT have been reported both as the sole lesion and as part of a multifocal lesion (Dyson et al. 2003). Computed tomography (CT) and magnetic resonance imaging allow specific diagnosis of deep digital flexor tendon lesions within the hoof capsule; however, direct intralesional treatment of such lesions is difficult because of the hoof's rigid structure. A technique designed to mimic intralesional injection of insertional tendinopathies of the DDFT in the standing horse using radiographic guidance was assessed. Radiographic and contrast CT imaging and sectioning of the limbs confirmed accurate injection in all cases although inadvertant administration of injectate into adjacent structures was also evident.     

Computer tomographic differentiation of intrathoracic neoplasms and inflammation in the dog

The purpose of this study was to elaborate on the advantages and limits of computed tomography (CT) in the differentiation of thoracic lesions, in particular neoplasias. In the course of the investigation CT-scans of the thorax of 31 dogs with lesions in the area of the lungs or mediastinum were evaluated. The lesions were rated by morphology, distribution pattern, attenuation values and contrast-enhancement. Biopsies or the whole body underwent a pathohistological examination. Of the 31 dogs 17 had neoplastic and 14 had inflammatory lesions in the thoracic region. With help of the CT, the exact localisations of the different lesions was possible in most cases. Due to their characteristic morphologies, distribution patterns and attenuation values the differentiation between inflammatory and neoplastic lesions was possible in most cases (n=25/31) on the basis of the CT-scans. Mean non-enhanced CT attenuation values of the neoplastic lesions ranged between 31 and 50 HU, of the inflammatory lesions between -251 and 9 HU. Both neoplastic and inflammatory lesions showed contrast enhancement (between 14 and 38 HU and between 2 and 95 HU respectively). The mediastinal abcesses enhanced mainly on the periphery of the lesion. A differentiation of the various types of neoplastic lesions based on the non-enhanced attenuation values was not successful. Only metastasis could be differentiated because of their distribution pattern.     

NORMAL VARIATION IN SIZE OF THE LATERAL VENTRICLES OF THE LABRADOR RETRIEVER DOG AS ASSESSED BY MAGNETIC RESONANCE IMAGING

Detecting canine brain lesions on computed tomography (CT) or magnetic resonance (MR) scans can be difficult if the lesions do not enhance well following administration of intravenous contrast material. Changes in the shape and position of the ventricular system can be important in the diagnosis of such lesions. Normal variation within the canine ventricular system has not been documented. MR scans from 62 normal Labrador retriever type dogs were evaluated. Five dogs had symmetric enlargement of the ventricles, while nineteen dogs had mild to severe ventricular asymmetry. The incidence of asymmetry in normal dogs must be considered when using ventricular configuration as an indication of central nervous system abnormality.     

Comparison of concurrent imaging modalities for staging of dogs with appendicular primary bone tumours

This study assessed the use of whole body computed tomography (CT) for the evaluation of metastasis in dogs with primary appendicular bone tumours compared to long bone survey radiography, bone scintigraphy and thoracic radiographs. Fifteen dogs were included in this pilot study. A construct reference standard was used for detection of bone metastasis, and negative thoracic radiographs were compared against CT. Definitive lesions were only identified on bone scintigraphy. Not all lesions agreed with the construct reference standard. No definitive lesions were identified on survey radiographs or CT. Lesions were identified on thoracic CT that were not visible radiographically. Equivocal ground glass pulmonary lesions progressed in three of four cases. Whole body CT was not a suitable alternative to bone scintigraphy; however, it was useful as an adjunctive diagnostic modality. Pulmonary lesions were visible on CT that were not seen radiographically and ground glass pulmonary lesions in dogs should be considered suspicious for metastasis.     

COMPUTED TOMOGRAPHY OF RAMBOUILLET SHEEP AFFECTED WITH NEURONAL CEROID LIPOFUSCINOSIS

Computed tomography (CT) was performed on 3 normal Rambouillet sheep and 6 Rambouillet sheep affected with neuronal ceroid lipofuscinosis. Characteristic lesions seen in the brain of affected sheep included dramatically enlarged lateral ventricles and reduced cerebral thickness. The lesions were seen in sheep as young as 4 months of age. Antemortem CT observations correlated well with postmortem findings in this model of Neuronal Ceroid Lipofuscinosis.     

Radiographic, magnetic resonance imaging, computed tomographic, and rhinoscopic features of nasal aspergillosis in dogs

OBJECTIVE: To determine radiographic, magnetic resonance imaging (MRI), computed tomography (CT), and rhinoscopic features of nasal aspergillosis in dogs. DESIGN: Prospective study. ANIMALS: 15 client-owned dogs. PROCEDURE: All dogs had clinical signs of chronic nasal disease; the diagnosis of nasal aspergillosis was made on the basis of positive results for at least 2 diagnostic tests (serology, cytology, histology, or fungal culture) and detection of typical intrasinusal and intranasal fungal colonies and turbinate destruction via rhinoscopy. Radiography, MRI, and CT were performed under general anesthesia. Rhinoscopy was repeated to evaluate lesions and initiate treatment. Findings of radiography, MRI, CT, and rhinoscopy were compared. RESULTS: MRI and CT revealed lesions suggestive of nasal aspergillosis more frequently than did radiography. Computed tomography was the best technique for detection of cortical bone lesions; the nature of abnormal soft tissue, however, could not be identified. Magnetic resonance imaging allowed evaluation of lesions of the frontal bone and was especially useful for differentiating between a thickened mucosa and secretions or fungal colonies; however, fungal colonies could not be differentiated from secretions. Rhinoscopy allowed identification of the nature of intranasal and intrasinusal soft tissue but was not as useful as CT and MRI for defining the extent of lesions and provided no information regarding bone lesions. CONCLUSIONS AND CLINICAL RELEVANCE: The value of CT and MRI for diagnosis of nasal aspergillosis was similar and greater than that of radiography. Rhinoscopy is necessary because it is the only technique that allows direct visualization of fungal colonies.     

COMPUTED TOMOGRAPHIC FEATURES OF PHARYNGEAL NEOPLASIA IN 25 DOGS

Computed tomography (CT) is commonly used to investigate head tumors in dogs, however little information is available for lesions of the pharyngeal area. The purpose of this multicentric, retrospective, cross‐sectional study was to describe the CT findings in a sample of dogs with pathologically confirmed pharyngeal neoplasia and determine whether any CT features allowed differentiation of tumor type. Location of lesions, size and shape, margins, relationship with surrounding structures and vessels, attenuation characteristics and enhancement pattern, regional lymph node changes, and presence of metastasis were recorded by three observers (1 DECVDI). The effect of final diagnosis on each CT feature was tested. A total of 25 dogs were included: 15 with carcinomas, five sarcomas, four melanomas, and one lymphoma. The oropharynx and laryngopharynx were more frequently involved. Among tumor groups, lesions were of similar size, irregularly shaped, had ill‐defined margins, and had moderate‐to‐marked heterogeneous contrast enhancement. Lysis of hyoid bones was recorded in two carcinomas and infiltration of the lingual artery occurred in one case. Marked medial retropharyngeal lymphoadenomegaly was recorded in 11 of 14 carcinomas, in all sarcomas and in two of four melanomas. The single lymphoma case showed ill‐defined thickening of the oropharyngeal and laryngeal wall with retropharyngeal and mandibular lymphadenomegaly. Lung metastases were found in two of five sarcomas and two of four melanomas. Findings from the current study did not support the hypothesis that CT features could be used to predict pharyngeal tumor type in dogs. However, CT was helpful for determining mass extension, lymph node involvement, and distant metastatic spread.     

COMPUTED TOMOGRAPHY OF NONANESTHETIZED CATS WITH UPPER AIRWAY OBSTRUCTION

Upper airway obstruction is a potentially life‐threatening problem in cats and for which a noninvasive, sensitive method rapid diagnosis is needed. The purposes of this prospective study were to describe a computed tomography (CT) technique for nonanesthetized cats with upper airway obstruction, CT characteristics of obstructive diseases, and comparisons between CT findings and findings from other diagnostic tests. Ten cats with clinical signs of upper airway obstruction were recruited for the study. Four cats with no clinical signs of upper airway obstruction were recruited as controls. All cats underwent computed tomography imaging without sedation or anesthesia, using a 16‐slice helical CT scanner and a previously described transparent positional device. Three‐dimensional (3D) internal volume rendering was performed on all CT image sets and 3D external volume rendering was also performed on cats with evidence of mass lesions. Confirmation of upper airway obstruction was based on visual laryngeal examination, endoscopy, fine‐needle aspirate, biopsy, or necropsy. Seven cats were diagnosed with intramural upper airway masses, two with laryngotracheitis, and one with laryngeal paralysis. The CT and 3D volume‐rendered images identified lesions consistent with upper airway disease in all cats. In cats with mass lesions, CT accurately identified the mass and location. Findings from this study supported the use of CT imaging as an effective technique for diagnosing upper airway obstruction in nonanesthetized cats.     

Comparison between magnetic resonance imaging,computed tomography,and arthrography to identify artificially induced cartilage defects of the equine carpal joints

While articular cartilage changes are considered to be one of the initial events in the pathological cascade leading to osteoarthritis, these changes remain difficult to detect using conventional diagnostic imaging modalities such as plain radiography. The aim of this prospective, experimental, methods comparison study was to compare the sensitivity of magnetic resonance imaging (MRI), magnetic resonance arthrography, computed tomography (CT), and CT arthrography in the detection of artificially induced articular cartilage defects in the equine carpal joints. Defects were created in the antebrachiocarpal and middle carpal joint using curettage by a board‐certified equine surgeon. Normal articular cartilage thickness varied from a maximum of 1.22 mm at the level of the distal aspect of the radius to a minimum of 0.17 mm in the proximal articular surface of the third carpal bone. Regarding cartilaginous defect measurements the remaining cartilaginous bed range from a maximum of 0.776 mm in the partial thickness defects, and 0 mm (defect reaches the subchondral bone) when total thickness defect were made. Computed tomography and magnetic resonance imaging were performed followed by CT arthrography and magnetic resonance arthrography after antebrachiocarpal and middle carpal intraarticular contrast administration. All images were reviewed by two board‐certified veterinary radiologists, both of whom were blinded to the location, presence of, and thickness of the cartilage defects. A total number of 72 lesions in nine limbs were created. Mean sensitivity for localizing cartilage defects varied between imaging modalities with CT arthrography showing the best sensitivity (69.9%), followed by magnetic resonance arthrography (53.5%), MRI (33.3%), and CT (18.1%) respectively. The addition of contrast arthrography in both magnetic resonance and CT improved the rate of cartilage lesion detection although no statistical significance was found. Computed tomographic arthrography displayed the best sensitivity for detecting articular cartilage defects in the equine antebrachiocarpal and middle‐carpal joints, compared to magnetic resonance arthrography, MRI, and CT.     

Computed tomography (CT) of the lungs of the dog using a helical CT scanner, intravenous iodine contrast medium and different CT windows

The aim of this study was to determine the accuracy of helical computed tomography (CT) for visualizing pulmonary parenchyma and associated formations in normal dogs. CT scan was performed by using intravenous contrast medium and by applying different types of CT windows: soft tissue and lung windows, and high-resolution computed tomography of the lung. This technique allowed, especially with lung window types, a good view of the parenchyma, bronchial tree, vascular structures and pleural cavity. The selected images, with high anatomical quality and tissue contrast, may be a reference for future clinical studies of this organ. Thus, helical CT is a promising non-invasive method of diagnosing a wide variety of pulmonary diseases in dogs.     

APPLICATION AND MACHINE ACCURACY OF A NEW FRAMELESS COMPUTED TOMOGRAPHY‐GUIDED STEREOTACTIC BRAIN BIOPSY SYSTEM IN DOGS

The purpose of this study was to describe application and machine accuracy for a new computed tomography (CT) guided, frameless, stereotactic brain biopsy system in dogs. Heads from ten canine cadavers were secured to a bite‐plate with six attached fiducial markers and imaged using CT. Fiducialized CT images were imported into stereotactic software and spherical phantom lesions between 3.9 and 5.5 mm in diameter were created in six locations. Infrared cameras and reflective markers were used to register fiducials to the reconstructed image set. Coordinates in the X, Y, and Z planes were identified for each lesion center. Iohexol (1.5 μl of 240 mgI/ml) was injected into the center of each lesion and CT scans were repeated. Pre‐ and postinjection CT images for each cadaver were fused using the system software. Application accuracy was calculated using the center of each phantom lesion and the center of each injected contrast material location. Machine accuracy was calculated using a phantom with known distances between four fixed points in the X, Y, and Z planes. Mean application accuracy in the first 5 cadavers was 4.3 mm (95% confidence interval [CI] 2.9–4.3 mm) and in the second 5 cadavers was 2.9 mm (95% CI 2–3.9 mm). The more superficial lesions were targeted significantly less accurately than the deeper lesions (P = 0.0183). Median machine accuracy was 0.1 mm and the range was 0.1–0.2 mm. Findings supported use of the new biopsy system for canine brain lesions >3.9 mm in diameter.     

Cerebral pyogranuloma associated with systemic coronavirus infection in a ferret

A 2‐year‐old male ferret was presented with central nervous system signs. Computed tomography (CT) of the brain revealed a well‐defined contrast‐enhancing lesion on the rostral forebrain that appeared extraparenchymal. Surgical excision of the mass was performed and the ferret was euthanised during the procedure. Histopathology of the excised mass showed multiple meningeal nodular lesions with infiltrates of epithelioid macrophages, occasionally centred on degenerated neutrophils and surrounded by a broad rim of plasma cells, features consistent with pyogranulomatous meningitis. The histopathological features in this ferret were similar to those in cats with feline infectious peritonitis. Definitive diagnosis was assessed by immunohistochemistry, confirming a ferret systemic coronavirus (FSCV) associated disease. This is the first case of coronavirus granuloma described on CT‐scan in the central nervous system of a ferret.