A repeatable CT protocol for quantifying caudal vena cava growth in medium and large breed dogs.

Developmental malformations can cause stunted or abnormal growth and clinical disease in dogs. In humans, measurements of the inferior vena cava are used as methods for detecting abnormal growth trajectories. The objectives of this retrospective, multicenter, analytical, cross-sectional study were to develop a repeatable protocol to measure the caudal vena cava (CVC) and generate growth curves in medium and large-breed dogs during development. Contrast-enhanced CT DICOM images from 438 normal dogs, aged from 1 to 18 months, from five specific breeds were included. A "best guess" measurement protocol was created. Dogs were stratified into medium or large breed groups based on growth rate trajectories. Linear regression models and logarithmic trend lines were used to evaluate the CVC growth over time. The CVC measurements were analyzed from four anatomical regions: thorax, diaphragm, intra-hepatic, and renal. The thoracic segment produced the most repeatable measurements with the highest explanatory power. The CVC thoracic circumference ranged from 2.5 to 4.9 cm from 1 to 18 months of age. Medium and large breeds had similar CVC growth trajectories, with comparable estimated marginal means, however medium dogs reached 80% of predicted final CVC size approximately 4 weeks earlier than large breed dogs. This new protocol provides a standardized technique for evaluation of the CVC circumference over time using contrast-enhanced CT and is most repeatable when taken at the thoracic level. This approach could be adapted for other vessels to predict their growth trajectories, generating healthy reference population data for comparison against patients with vascular anomalies.

Lean body weight-adjusted intravenous iodinated contrast dose for abdominal CT in dogs reduces interpatient enhancement variability while providing diagnostic quality organ enhancement.

Contrast-enhanced computed tomography (CECT) is increasingly used to screen for abdominal pathology in dogs, and the contrast dose used is commonly calculated as a linear function of total body weight (TBW). Body fat is not metabolically active and contributes little to dispersing or diluting contrast medium (CM) in the blood. This prospective, analytic, cross-section design pilot study aimed to establish the feasibility of intravenous CM dosed according to lean body weight (LBW) for abdominal CECT in dogs compared to TBW. We hypothesized that when dosing intravenous CM according to LBW, studies will remain at diagnostic quality, there will be a reduced interindividual contrast enhancement (CE) variability, and there will be less change to heart rate and blood pressure in dogs compared to when administering CM calculated on TBW. Twelve dogs had two CECT studies with contrast doses according to TBW and LBW at least 8 weeks apart. Interindividual organ and vessel CE variability, diagnostic quality of the studies, and changes in physiological status were compared between protocols. The LBW-based protocol provided less variability in the CE of most organs and vessels (except the aorta). When dosed according to LBW, liver enhancement was positively associated with grams of iodine per kg TBW during the portal venous phase (P = 0.046). There was no significant difference in physiological parameters after CM administration between dosing protocols. Our conclusion is that a CM dose based on LBW for abdominal CECT lowers interindividual CE variability and is effective at maintaining studies of diagnostic quality.

Aorta, liver, and portal vein CT contrast enhancement during the portal venous phase are positively associated with abdominal fat percentage in dogs.

Contrast-enhanced computed tomography (CT) is increasingly being used as a standard diagnostic test for dogs with suspected abdominal pathology. The iodinated contrast dose is commonly calculated based on linear increases in total body weight. However, body fat is not metabolically active and contributes little to dispersing or diluting the contrast medium in the blood. The aim of this retrospective single-center analytic study was to investigate the possible correlation between abdominal organ and vessel enhancement, and abdominal fat percentage in dogs. We hypothesized that, when dosing intravenous iodinated contrast according to total body weight, there would be a positive association between the degree of contrast enhancement of selected organs and vessels with increasing abdominal fat percentage. Vascular and parenchymal attenuation data were collected from 62 multiphasic abdominal CECT scans performed on dogs over a 5-year period at U-Vet Werribee Animal Hospital between February 2014 and February 2019. Findings based on a linear regression model showed a positive association of aorta (P = .005), liver (P = .045), and portal vein (P = .001) enhancement to abdominal fat percentage during the portal venous phase. Authors recommend that other body size parameters, such as lean body weight, should be considered when calculating iodine dose for abdominal contrast-enhanced CT in dogs.

Development and Implementation of a Corriedale Ovine Brain Atlas for Use in Atlas-Based Segmentation.

Segmentation is the process of partitioning an image into subdivisions and can be applied to medical images to isolate anatomical or pathological areas for further analysis. This process can be done manually or automated by the use of image processing computer packages. Atlas-based segmentation automates this process by the use of a pre-labelled template and a registration algorithm. We developed an ovine brain atlas that can be used as a model for neurological conditions such as Parkinson's disease and focal epilepsy. 17 female Corriedale ovine brains were imaged in-vivo in a 1.5T (low-resolution) MRI scanner. 13 of the low-resolution images were combined using a template construction algorithm to form a low-resolution template. The template was labelled to form an atlas and tested by comparing manual with atlas-based segmentations against the remaining four low-resolution images. The comparisons were in the form of similarity metrics used in previous segmentation research. Dice Similarity Coefficients were utilised to determine the degree of overlap between eight independent, manual and atlas-based segmentations, with values ranging from 0 (no overlap) to 1 (complete overlap). For 7 of these 8 segmented areas, we achieved a Dice Similarity Coefficient of 0.5-0.8. The amygdala was difficult to segment due to its variable location and similar intensity to surrounding tissues resulting in Dice Coefficients of 0.0-0.2. We developed a low resolution ovine brain atlas with eight clinically relevant areas labelled. This brain atlas performed comparably to prior human atlases described in the literature and to intra-observer error providing an atlas that can be used to guide further research using ovine brains as a model and is hosted online for public access.

Development of representative magnetic resonance imaging-based atlases of the canine brain and evaluation of three methods for atlas-based segmentation.

OBJECTIVE: To develop representative MRI atlases of the canine brain and to evaluate 3 methods of atlas-based segmentation (ABS). ANIMALS: 62 dogs without clinical signs of epilepsy and without MRI evidence of structural brain disease. PROCEDURES: The MRI scans from 44 dogs were used to develop 4 templates on the basis of brain shape (brachycephalic, mesaticephalic, dolichocephalic, and combined mesaticephalic and dolichocephalic). Atlas labels were generated by segmenting the brain, ventricular system, hippocampal formation, and caudate nuclei. The MRI scans from the remaining 18 dogs were used to evaluate 3 methods of ABS (manual brain extraction and application of a brain shape-specific template [A], automatic brain extraction and application of a brain shape-specific template [B], and manual brain extraction and application of a combined template [C]). The performance of each ABS method was compared by calculation of the Dice and Jaccard coefficients, with manual segmentation used as the gold standard. RESULTS: Method A had the highest mean Jaccard coefficient and was the most accurate ABS method assessed. Measures of overlap for ABS methods that used manual brain extraction (A and C) ranged from 0.75 to 0.95 and compared favorably with repeated measures of overlap for manual extraction, which ranged from 0.88 to 0.97. CONCLUSIONS AND CLINICAL RELEVANCE: Atlas-based segmentation was an accurate and repeatable method for segmentation of canine brain structures. It could be performed more rapidly than manual segmentation, which should allow the application of computer-assisted volumetry to large data sets and clinical cases and facilitate neuroimaging research and disease diagnosis.

International Veterinary Epilepsy Task Force recommendations for a veterinary epilepsy-specific MRI protocol.

Epilepsy is one of the most common chronic neurological diseases in veterinary practice. Magnetic resonance imaging (MRI) is regarded as an important diagnostic test to reach the diagnosis of idiopathic epilepsy. However, given that the diagnosis requires the exclusion of other differentials for seizures, the parameters for MRI examination should allow the detection of subtle lesions which may not be obvious with existing techniques. In addition, there are several differentials for idiopathic epilepsy in humans, for example some focal cortical dysplasias, which may only apparent with special sequences, imaging planes and/or particular techniques used in performing the MRI scan. As a result, there is a need to standardize MRI examination in veterinary patients with techniques that reliably diagnose subtle lesions, identify post-seizure changes, and which will allow for future identification of underlying causes of seizures not yet apparent in the veterinary literature.There is a need for a standardized veterinary epilepsy-specific MRI protocol which will facilitate more detailed examination of areas susceptible to generating and perpetuating seizures, is cost efficient, simple to perform and can be adapted for both low and high field scanners. Standardisation of imaging will improve clinical communication and uniformity of case definition between research studies. A 6-7 sequence epilepsy-specific MRI protocol for veterinary patients is proposed and further advanced MR and functional imaging is reviewed.

Structural and functional correlations in a large animal model of bleomycin-induced pulmonary fibrosis.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a severe and progressive respiratory disease with poor prognosis. Despite the positive outcomes from recent clinical trials, there is still no cure for this disease. Pre-clinical animal models are currently largely limited to small animals which have a number of shortcomings. We have previously shown that fibrosis is induced in isolated sheep lung segments 14 days after bleomycin treatment. This study aimed to determine whether bleomycin-induced fibrosis and associated functional changes persisted over a seven-week period. METHODS: Two separate lung segments in nine sheep received two challenges two weeks apart of either, 3U bleomycin (BLM), or saline (control). Lung function in these segments was assessed by a wedged-bronchoscope procedure after bleomycin treatment. Lung tissue, and an ex vivo CT analysis were used to assess for the persistence of inflammation, fibrosis and collagen content in this model. RESULTS: Fibrotic changes persisted up to seven weeks in bleomycin-treated isolated lung segments (Pathology scores: bleomycin12.27 ± 0.07 vs. saline 4.90 ± 1.18, n = 9, p = 0.0003). Localization of bleomycin-induced injury and increased tissue density was confirmed by CT analysis (mean densitometric CT value: bleomycin -698 ± 2.95 Hounsfield units vs. saline -898 ± 2.5 Hounsfield units, p = 0.02). Masson's trichrome staining revealed increased connective tissue in bleomycin segments, compared to controls (% blue staining/total field area: 8.5 ± 0.8 vs. 2.1 ± 0.2 %, n = 9, p < 0.0001). bleomycin-treated segments were significantly less compliant from baseline at 7 weeks post treatment compared to control-treated segments (2.05 ± 0.88 vs. 4.97 ± 0.79 mL/cmH20, n = 9, p = 0.002). There was also a direct negative correlation between pathology scores and segmental compliance. CONCLUSIONS: We show that there is a correlation between fibrosis and correspondingly poor lung function which persist for up to seven weeks after bleomycin treatment in this large animal model of pulmonary fibrosis.

Magnetic resonance imaging, computed tomography, and gross anatomy of the canine tarsus.

OBJECTIVES: To describe the normal anatomy of the soft tissues of the canine tarsus as identified on computed tomography (CT) and magnetic resonance imaging (MRI) and to evaluate specific MRI sequences and planes for observing structures of diagnostic interest. STUDY DESIGN: Prospective descriptive study. ANIMALS: Canine cadavers (n = 3). METHODS: A frozen cadaver pelvic limb was used to trial multiple MRI sequences using a 1.5 T superconducting magnet and preferred sequences were selected. Radiographs of 6 canine cadaver pelvic limbs confirmed the tarsi were radiographically normal. A 16-slice CT scanner was used to obtain 1 mm contiguous slices through the tarsi. T1-weighted, proton density with fat suppression (PD FS) and T2-weighted MRI sequences were obtained in the sagittal plane, T1-weighted, and PD FS sequences in the dorsal plane and PD FS sequences in the transverse plane. The limbs were frozen for one month and sliced into 4-5 mm thick frozen sections. Anatomic sections were photographed and visually correlated to CT and MR images. RESULTS: Most soft tissue structures were easiest to identify on the transverse MRI sections with cross reference to either the sagittal or dorsal plane. Bony structures were easily identified on all CT, MR, and gross sections. CONCLUSIONS: The anatomy of the canine tarsus can be readily identified on MR imaging.

Imaging diagnosis--Use of multiphasic contrast-enhanced computed tomography for diagnosis of mesenteric volvulus in a dog.

A 4-year-old German shorthaired pointer presented with collapse and hematochezia. Radiographs showed gas and fluid-distended small intestines and loss of serosal detail. Ultrasound examination showed hypomotile, fluid-distended small intestines, and thrombosed jejunal veins. Multiphasic contrast-enhanced computed tomography was performed and showed a CT "whirl sign," an important but nonspecific sign of intestinal volvulus in human patients. At surgery, the majority of the small intestine was entangled in the volvulus and showed black discoloration. The patient was euthanized. Postmortem evaluation yielded a diagnosis of jejunoileal mesenteric volvulus secondary to a congenital omphalomesenteric duct remnant.

Description of technique and lower reference limit for magnetic resonance imaging of hippocampal volumetry in dogs.

OBJECTIVE: To evaluate the use of high-resolution MRI for hippocampal volumetry in dogs and to define a lower reference limit for hippocampal formation (HF) volume. ANIMALS: 20 dogs (with no history of seizures and no underlying structural brain disease) that underwent MRI of the brain. PROCEDURES: The MRI protocol included a high-resolution T1-weighted 3-D ultrafast gradient-echo sequence aligned in a dorsal plane perpendicular to the long axis of the HF. Images obtained with MRI were retrospectively analyzed by 2 observers (A and B). Intraobserver and interobserver agreement were calculated with the Lin concordance correlation coefficient. Volume measurements of the HF were adjusted for intracranial volume, and a lower 95% reference limit for adjusted HF volume was calculated. RESULTS: There was substantial intraobserver agreement (Lin concordance correlation coefficient, 0.97 [95% confidence interval {CI}, 0.94 to 0.99]) but poor interobserver agreement (Lin concordance correlation coefficient, 0.63 [95% CI, 0.37 to 0.79]). The lower 95% reference limit for adjusted HF volume was 0.56 cm(3) (90% CI, 0.52 to 0.60 cm(3)) for the right HF and 0.55 cm(3) (90% CI, 0.52 to 0.58 cm(3)) for the left HF. CONCLUSIONS AND CLINICAL RELEVANCE: HF volumes should be adjusted for intracranial volume to account for the large variation in canine skull size. The amount of time required to perform HF volumetry and low interobserver agreement may restrict this technique to research applications, such as the investigation of epileptic patients for hippocampal sclerosis or other cognitive disorders.

Central diabetes insipidus in a cat with central nervous system B cell lymphoma.

A 6-year-old male neutered cat presented with blindness, lethargy, polydipsia, hyposthenuria and severe hypernatraemia. Central diabetes insipidus was demonstrated by means of a low measured anti-diuretic hormone (ADH) concentration in the face of hypernatraemia, and clinical response to supplementation with desmopressin. Magnetic resonance imaging of the brain showed a discrete mass in the region of the hypothalamus. The cat was euthanased and post-mortem histological examination demonstrated B cell lymphoma involving the brain, optic nerves, urinary bladder wall and diaphragm. To the authors' knowledge, this case report is the first to describe central diabetes insipidus caused by central nervous system lymphoma in the cat.

Spontaneous feline pneumothorax caused by ruptured pulmonary bullae associated with possible bronchopulmonary dysplasia.

Spontaneous pneumothorax is rarely reported in the cat. This case report describes the use of computed tomography (CT) to diagnose pulmonary bullae in an adult cat with recurrent spontaneous pneumothorax. A large bulla in the right middle lung lobe and several blebs in other lobes were identified by CT. Partial lobectomy of the right middle and right and left cranial lung lobes was successfully performed to remove the affected portions of lung. Histopathological examination suggested bronchopulmonary dysplasia (BPD) as the underlying cause for development of the pulmonary bulla. This is the first case report in the veterinary literature describing the use of CT to identify pulmonary bullae in the cat with BPD as a possible underlying cause.