HEPATIC VOLUME ESTIMATION USING QUANTITATIVE COMPUTED TOMOGRAPHY IN DOGS WITH PORTOSYSTEMIC SHUNTS

The purpose of this study was to use quantitative computed tomography (CT) to estimate liver volume in dogs with a portosystemic shunt and to compare the liver volume in normal dogs to dogs with a shunt. Twenty-one dogs with a portosystemic shunt underwent contrast-enhanced abdominal CT for shunt characterization and preoperative planning. Six dogs without clinical signs relating to liver disease were used as a control group. In addition, liver volume was compared before and 2-4 months after surgical shunt attenuation in three dogs. All studies followed established clinical imaging protocols. Liver margins were defined on each image using an operator-defined region of interest and hepatic volume renderings were produced from which the liver volume was quantitatively estimated. There was a statistically significant association between liver volume and body weight in control and shunt dogs (r = 0.909 and 0.899, respectively, P < 0.01). Liver volume normalized to body weight was 15.5 +/- 5.2 cm3/kg in affected dogs and 24.5 +/- 5.6 cm3/kg in control dogs. Based on postligation CT studies in three affected dogs, liver volume increased by 43%, 51%, and 62%. Hepatic volume estimation may be a clinically useful parameter in the initial and postsurgical evaluation of dogs with portosystemic shunts.     

COMPUTED TOMOGRAPHY OF HEREDITARY MULTIFOCAL RENAL CYSTADENOCARCINOMAS IN GERMAN SHEPHERD DOGS

the purpose of the study was to characterize the renal lesions of hereditary renal cystadenocarcinomas in the German shepherd dog using computed tomography (CT), Fourteen dogs with renal cystadenocarcinomas and nodular dermatofibrosis, and two unaffected dogs were studied. There were nine dogs with spontaneous disease and seven dogs from a test mating. The characteristic renal CT findings of renal cystadenocarcinomas were bilateral multiple cysts and tumor masses of various sizes. The earliest change were detected between 4 and 5 years of age and the smallest cysts measured 2-3 mm in diameter. Abdominal CT examination gives a wide field view and excellent anatomic images of the kidneys. It is easy to differentiate between cysts and solid tumors. CT examination is useful for the early detection of renal cystadenocarcinomas and for screening suspected carrier dogs before breeding.     

RENAL ULTRASONOGRAPHIC AND COMPUTED TOMOGRAPHIC APPEARANCE, VOLUME, AND FUNCTION OF CATS WITH AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE

The purpose of this study was to describe the ultrasonographic (US) and computed tomographic (CT) appearance of autosomal dominant polycystic kidney disease (ADPKD) in cats; to compare renal volume in cats with ADPKD (n = 5; mean age 59 +/- 10 months)) and normal cats (n = 5; mean age 66 +/- 10 months) using 2 imaging modalities, US and CT; and to calculate cyst volume using CT. Glomerular filtration rate (GFR) was determined by 2 methods: 99mTc-diethylene-triaminepentaacetic acid (99mTc-DPTA) scintigraphic uptake and 99-Tc-DTPA plasma clearance. Sonographically, ADPKD affected kidneys were characterized by multiple anechoic to hypoechoic, round to irregularly shaped structures with variation in size. Affected kidneys had indistinct corticomedullary junctions and foci of mineralization. Intravenous (IV) contrast medium administration allowed more definitive identification of cysts with CT, and identification of distortion of renal pelves by cysts. A significant difference (Welch ANOVA, P = 0.05) was detected between the US-estimated renal volumes of normal and affected cats. No statistically significant differences were detected in CT volume (between the normal and affected cats, or between US and CT volume measurements) or the 2 GFR methods. In this group of clinically normal, middle-aged ADPKD cats, renal function was within normal limits and not significantly different than normal.     

NORMAL CROSS-SECTIONAL ANATOMY OF THE FELINE THORAX AND ABDOMEN: COMPARISON OF COMPUTED TOMOGRAPHY AND CADAVER ANATOMY

Computed tomographic images of two adult domestic short-haired cats were obtained with a whole body scanner. Images of the thorax and abdomen were compared with cross-sectional anatomy cadaver specimens from the same two cats. Anatomic structures were first identified on the cadaver specimens with the aid of numerous anatomy texts and references and were then identified and labeled on the computed tomographic images. Results from this project provide an atlas of normal cross-sectional gross and CT anatomy of the feline thorax and abdomen that can be used in the interpretation of any cross-sectional imaging modality.     

USE OF COMPUTED TOMOGRAPHY RENAL ANGIOGRAPHY FOR SCREENING FELINE RENAL TRANSPLANT DONORS

Preoperative knowledge of the renal vascular anatomy is important for selection of the appropriate feline renal donor. Intravenous urograms (IVUs) have been performed routinely to screen potential donors at the Veterinary Hospital of the University of Pennsylvania (VHUP), but the vascular phase views lack sufficient detail of the renal vascular anatomy. Computed tomography angiography (CTA), which requires a helical computed tomography (CT) scanner, has been found to provide superior renal vascular anatomic information of prospective human renal donors. The specific aims of this study were as follows: 1) develop the CTA technique for the feline patient; and 2) obtain preliminary information on feline renal vessel anatomy in potential renal donors. Ten healthy, potential feline renal donors were anesthetized and imaged using a third-generation helical CT scanner. The time delay between i.v. contrast medium injection and image acquisition, and other parameters of slice collimation, slice interval, pitch, exposure settings, and reconstruction algorithms were varied to maximize contrast medium opacification of the renal vascular anatomy. Optimal CTA acquisition parameters were determined to be: 1) 10-sec delay post-i.v. bolus of iodinated contrast medium; 2) two serially acquired (corresponding to arterial and venous phases) helical scans through the renal vasculature; 3) pitch of 2 (4 mm/sec patient translation, 2 mm slice collimation); and 4) 120-kVp, 160-mA, and 1-sec exposure settings. Retrospective reconstructed CTA transverse images obtained at a 2-mm slice width and a 1-mm slice interval in combination with two-dimensional reformatted images and three-dimensional reconstructed images were qualitatively evaluated for vascular anatomy; vascular anatomy was confirmed at surgery. Four cats had single renal arteries and veins bilaterally; four cats had double renal veins. One cat had a small accessory artery supplying the caudal pole of the left kidney. One cat had a left renal artery originating from the aorta at a 90 degrees angle with the cranial mesenteric artery. CTA of the feline renal vascular anatomy is feasible, and reconstruction techniques provide excellent anatomic vascular detail. CTA is now used routinely at VHUP to screen all potential feline renal donors.     

EVALUATION OF THE FELINE PANCREAS USING COMPUTED TOMOGRAPHY AND RADIOLABELED LEUKOCYTES

This study was designed to test the feasibility and utility of computed tomography and radiolabeled granulocytes in evaluating the feline pancreas in six normal cats. Autologous granulocytes were labeled with 99mTc-hexamethylpropyleneamine oxime (HMPAO) and injected into each cat. Whole body scintigraphic images were acquired at 1, 5, 15, and 30 minutes, and 1, 2, and 4 hours following injection. The following day, each cat was anesthetized and computed tomographic images of the abdomen were acquired both pre- and post-contrast. Following CT, a surgical pancreatic biopsy was collected. Feline granulocytes were successfully labeled with 99mTc-HMPAO with a labeling efficiency of 15-42% (average of 27%). An average of 5.42 x 10(7) cells in a 2 mL volume were injected into each cat. Less than 1 minute was required to acquire 500,000 count images. Granulocytes distributed predominantly to the lung, spleen and liver in order of decreasing activity. Only background activity was identified in the region of the pancreas. The pancreas was easily identified on CT images of the abdomen. The pancreas was hypoattenuating relative to both the spleen and liver. The pancreas enhanced with the administration of contrast medium, peaking immediately, then gradually clearing over the 30-minute test period. Following contrast medium administration the pancreas remained hypoattenuating relative to the spleen. All biopsies confirmed the absence of pancreatic inflammation in the study cats and no adverse effects were recognized as a result of pancreatic biopsy. Both computed tomography and radiolabeled granulocytes appear to hold promise as imaging procedures for the detection of feline pancreatitis. We predict that these described normal parameters may be altered in the face of inflammation, facilitating detection of feline pancreatitis. Data from cases of suspect feline pancreatitis are needed to evaluate these methods for clinical utility.     

DYNAMIC COMPUTED TOMOGRAPHY OF THE NORMAL FELINE HYPOPHYSIS CEREBRI (GLANDULA PITUITARIA)

The purpose of this study was to describe normal feline hypophyseal mensuration and contrast enhancement characteristics using dynamic computed tomography (CT) imaging. An intravenous bolus of an ionic iodinated contrast medium was administered to eight cats using a pressure injector while dynamic CT images were obtained every 5 s for five cats and every 7 s for three cats for a total imaging time of 5 min. Each pituitary was measured at its maximum height and width on the peak contrast medium enhancement image. A hand-drawn region of interest was placed around each hypophysis cerebri and time attenuation curves were generated. The specific enhancement pattern of the hypophysis cerebri for each cat was recorded. The mean width and height of the hypophysis cerebri was 5.2 +/- 0.4 (average +/- SD) mm and 3.1 +/- 0.3 mm, respectively. The mean time to maximum contrast enhancement was 28.6 +/- 14.8 s (range 14-50 s) from the onset of contrast medium injection. Four cats had initial dorsal and peripheral contrast enhancement patterns of the hypophysis cerebri, while four cats had an initial central contrast medium enhancement pattern. The hypophysis cerebri had a homogenous appearance in all cats, 28-50 s after contrast medium injection. The average (+/- SD) clearance half-time was 292 (+/- 87) s. Normal hypophysis cerebri mensuration and contrast medium enhancement characteristics will help in clinical evaluation of the feline hypophysis cerebri.     

ULTRASONOGRAPHIC DETERMINATION OF RENAL VOLUME IN THE DOG

Ultrasonographic linear and area measurements were performed on both kidneys of 15 clinically healthy dogs. Renal volumes were calculated from linear and area data applying three prolate ellipsoid models. Ultrasonographic volumes were then compared using linear regression analysis with kidney volumes measured in vitro by water displacement. In vivo ultrasonographic volumes had a statistically significant relationship with the in vitro volume. The highest correlation was provided by the single plane area method. There was also a correlation between body weight and ultrasonographically detected renal volume, suggesting that ultrasound imaging may be a useful method for assessment of renal volume changes in dogs with renal disease.     

COMPUTED TOMOGRAPHY OF THE NORMAL FELINE NASAL CAVITY AND PARANASAL SINUSES

Computed tomography (CT) images of the feline nasal cavity and paranasal were acquiredfrom noraml adult cats. Good resolutin and amatomic detail were obtained from the CT images using soft tissue formatting. A desciption of normal feline nasal cavity and paranasal sinus anatomy using CT is presented.     

EVALUATION OF THE LOWER RESPIRATORY TRACT IN PSITTACINES USING RADIOLOGY AND COMPUTED TOMOGRAPHY

In the last 2¹/₂ years, 288 grey parrot and amazon species with symptoms of respiratory disease clinically were presented to the clinic for avian medicine at the Justus-Liebig-University in Giessen. Ventro-dorsal and latero-lateral radiographs were taken from all birds; radiologic signs of lower respiratory tract disease were noted. Radiographs were normal in 55 of the birds. The results of the radiographic examination for the remaining 233 birds were compared with the necropsy results of terminally ill parrots, with the results of laboratory examinations/endoscopy/and/or with an examination by computed tomography. Thoracic radiographs were evaluated for occurring radiological abnormalities pertaining to the respiratory tract. The frequency of these lesions and their association with a disease process and/or specific etiology was noted.     

DETERMINATION OF GLOMERULAR FILTRATION RATE IN DOGS USING CONTRAST-ENHANCED COMPUTED TOMOGRAPHY

The purpose of this project was to establish a procedure and reference values for glomerular filtration rate (GFR) using contrast-enhanced computed tomography (CT) in eight healthy dogs. A single section of the kidney was scanned sequentially after bolus injection (3 ml/s) of iohexol (300 mg/kg). Time-attenuation curves were constructed and the GFR per volume of kidney was calculated using Patlak graphical analysis software. The GFR was then converted from contrast clearance per unit volume (ml/min/ml) to contrast clearance per body weight (ml/min/kg). Individual kidney and global GFR were calculated using both CT and nuclear scintigraphy. Global GFR for each dog was also determined by plasma iohexol clearance. Contrast-enhanced CT underestimated the global GFR compared with the other two methods. The average global GFR was 2.57 +/- 0.33 ml/ min/kg using functional CT and 4.06 +/- 0.37 ml/min/kg using plasma iohexol clearance. There was significant (P < 0.05) interobserver variability of CT GFR of the right kidney and total GFR. There was decreased interobserver variability for the left kidney. There was no difference in the intraobserver variability for CT-determined individual kidney and global GFR. There was no difference between the motion corrected and nonmotion corrected values for individual and global CT GFR. Nuclear scintigraphy produced a slightly higher coefficient of variation than contrast-enhanced CT, 2.9% and 1.0%, respectively. It is hypothesized that altered renal blood flow, hematocrit of the small vessels, and nephrotoxicity play a role in the underestimation of GFR by contrast-enhanced CT.     

EVALUATION OF THE GASTROINTESTINAL TRACT IN DOGS USING COMPUTED TOMOGRAPHY

Abdominal computed tomography (CT) studies of 19 dogs with no history or clinical signs of gastrointestinal disease, and two dogs with a histological diagnosis of gastrointestinal neoplasia were examined retrospectively. Gastrointestinal segments were evaluated subjectively for conspicuity, contrast enhancement, and wall layering after contrast medium administration. In dogs without gastrointestinal disease, there were 62.8% of gastrointestinal segments (serosa to serosa) and 77.7% of gastrointestinal walls (serosa to mucosa) visualized. Wall layering on postcontrast images was seen in 21.8% of gastrointestinal segments. There was significant association between gastrointestinal diameter and wall thickness. There was significant association between weight and gastrointestinal wall thickness in the following regions: gastric fundus, gastric body, gastric pylorus, gastric pyloric antrum, duodenal cranial flexure, jejunum and ascending colon, and between patient weight and gastrointestinal diameter in cranial duodenal flexure, descending duodenum, transverse duodenum, ascending duodenum, and jejunum. Measurements acquired from CT studies correlated well with previously published normal reference ranges for radiographic and ultrasonographic studies. Gastrointestinal neoplasia, diagnosed in two dogs, had a gastrointestinal wall thickness greater than the range of the dogs without gastrointestinal disease. Computed tomography offers identification of the gastrointestinal tract segments in dogs, allows for evaluation of gastrointestinal diameter and aids in investigation of gastrointestinal wall thickness.     

EVALUATION OF CANINE LUMBOSACRAL STENOSIS USING INTRAVENOUS CONTRAST-ENHANCED COMPUTED TOMOGRAPHY

The objective of this study was to evaluate intravenous contrast-enhanced computed tomography as a technique for predicting the within-level location(s) of compressive soft tissues in the canine lumbosacral spine. Pre-operative intravenous contrast-enhanced computed tomography of the L5-S3 vertebral levels was performed in 12 consecutive large breed dogs with lumbosacral stenosis. The images were evaluated for enhancement of soft tissues by two radiologists who were unaware of the surgical findings. For each within-level location (dorsal canal, ventral canal, right lateral recess, left lateral recess) enhancement was classified as present, absent or equivocal. The results were compared with the results of surgical exploration and histopathology of excised tissues. The positive predictive values of intravenous contrast-enhanced computed tomography for compressive soft tissues involving the dorsal canal, ventral canal and lateral recesses were 83%, 100%, and 81% respectively. Negative predictive values for compressive soft tissues involving these locations were 29%, 50%, and 40% respectively.     

USING SEMI‐AUTOMATED SEGMENTATION OF COMPUTED TOMOGRAPHY DATASETS FOR THREE‐DIMENSIONAL VISUALIZATION AND VOLUME MEASUREMENTS OF EQUINE PARANASAL SINUSES

The system of the paranasal sinuses morphologically represents one of the most complex parts of the equine body. A clear understanding of spatial relationships is needed for correct diagnosis and treatment. The purpose of this study was to describe the anatomy and volume of equine paranasal sinuses using three‐dimensional (3D) reformatted renderings of computed tomography (CT) slices. Heads of 18 cadaver horses, aged 2–25 years, were analyzed by the use of separate semi‐automated segmentation of the following bilateral paranasal sinus compartments: rostral maxillary sinus (Sinus maxillaris rostralis), ventral conchal sinus (Sinus conchae ventralis), caudal maxillary sinus (Sinus maxillaris caudalis), dorsal conchal sinus (Sinus conchae dorsalis), frontal sinus (Sinus frontalis), sphenopalatine sinus (Sinus sphenopalatinus), and middle conchal sinus (Sinus conchae mediae). Reconstructed structures were displayed separately, grouped, or altogether as transparent or solid elements to visualize individual paranasal sinus morphology. The paranasal sinuses appeared to be divided into two systems by the maxillary septum (Septum sinuum maxillarium). The first or rostral system included the rostral maxillary and ventral conchal sinus. The second or caudal system included the caudal maxillary, dorsal conchal, frontal, sphenopalatine, and middle conchal sinuses. These two systems overlapped and were interlocked due to the oblique orientation of the maxillary septum. Total volumes of the paranasal sinuses ranged from 911.50 to 1502.00 ml (mean ± SD, 1151.00 ± 186.30 ml). 3D renderings of equine paranasal sinuses by use of semi‐automated segmentation of CT‐datasets improved understanding of this anatomically challenging region.     

USE OF COMPUTED TOMOGRAPHY AND COMPUTED TOMOGRAPHIC MYELOGRAPHY FOR ASSESSMENT OF SPINAL TUMORAL CALCINOSIS IN A DOG

Spinal tumoral calcinosis is reported in a Berner sennenhund puppy. The condition was manifested clinically as a non-ambulatory tetraparesis associated with neck pain. On survey radiographs there was a focal calcified mass at the atlantoaxial articulation. Computed tomography and computed tomographic myelography gave additional information on the extent of the mass and on the degree of spinal cord compression. The mass was removed surgically and the dog made a complete recovery.     

COMPUTED TOMOGRAPHIC EVALUATION OF CANINE AND FELINE MEDIASTINAL MASSES IN 14 PATIENTS

A 15-year retrospective analysis of histologically proven canine and feline mediastinal malignancies at the University of Minnesota was conducted to identify patients imaged by computed tomography (CT). The goal of the study was to characterize the CT appearance, to determine if there were any tumor type-specific appearances, and to clarify the role of CT in patients with mediastinal masses. Fourteen patients meeting these criteria were available for evaluation. The masses were characterized based on the presence or absence of contrast enhancement, internal architecture, size, extent of local invasion, the presence of pleural fluid, and the presence of regional vascular invasion. Within the limits of this study and the histopathologic information available, there appeared to be no clinically exploitable relationship between the CT appearance and the histologic characterization of the mass. However, CT does provide reasonably accurate local staging information.     

COMPUTED TOMOGRAPHY IN HORSES

Computed tomography (CT) is a valuable imaging procedure but one that requires significant technical support. Although scanners are available for veterinary use, their successful installation requires in-depth facility planning. Maintenance costs for these highly complex systems are high and may greatly exceed acquisition costs. Equipment to move anesthetized horses and support them during scanning is also expensive. Transport and scan table equipment suitable for equine CT studies are described. Clinical scan protocols used for CT of the equine skull and extremities are detailed. Precise positioning is essential for interpretable scans. Significant training in anatomy and CT physics is required for the veterinary computed tomographer.     

COMPUTED TOMOGRAPHY AND BLOOD GAS ANALYSIS OF ANESTHETIZED BLOODHOUNDS WITH INDUCED PNEUMOTHORAX

Increasingly severe degrees of pneumothorax were produced in 6 adult anesthetized bloodhounds. Computed tomography (CT) of the thorax was performed on each dog to evaluate the effects of pneumo thorax on thoracic and on pulmonary cross-sectional area (TA and PA). Arterial PO₂ (PaO₂) and PCO₂ (PaCO₂), heart rate (HR), and mean arterial blood pressure (MAP) were determined and related to the severity of pneumothorax. Volumes of air equal to 1, 1.5 and 2 times functional residual capacity of the lung produced approximately 33%, 40%, and 50% reductions in pulmonary area respectively. These amounts of atelectasis correspond to a radiographically "moderate" degree of pneumothorax. As severity of pneumothorax increased, thoracic area consistently increased, PaO₂ consistently decreased, and PaCO₂ consistently increased, with all being statistically significant relationships (p<0.0001); but HR and MAP were variable and showed no statistical correlation to the degree of pneumothorax (p>0.2).     

MULTIDETECTOR ROW COMPUTED TOMOGRAPHY AND ULTRASOUND CHARACTERISTICS OF CAUDAL VENA CAVA DUPLICATION IN DOGS

Caudal vena cava duplication has been rarely reported in small animals. The purpose of this retrospective study was to describe characteristics of duplicated caudal vena cava in a large group of dogs. Computed tomography (CT) and ultrasound databases from two hospitals were searched for canine reports having the diagnosis “double caudal vena cava.” One observer reviewed CT images for 71 dogs and two observers reviewed ultrasound images for 21 dogs. In all CT cases, the duplication comprised two vessels that were bilaterally symmetrical and approximately the same calibre (similar to Type I complete duplication in humans). In all ultrasound cases, the duplicated caudal vena cava appeared as a distinct vessel running on the left side of the abdominal segment of the descending aorta and extending from the left common iliac vein to the left renal vein. The prevalence of caudal vena cava duplication was 0.46% for canine ultrasound studies and 2.08% for canine CT studies performed at these hospitals. Median body weight for affected dogs was significantly lower than that of unaffected dogs (P < 0.0001). Breeds with increased risk for duplicated caudal vena cava were Yorkshire Terrier (odds ratio [OR] = 6.41), Poodle (OR = 7.46), West Highland White Terrier (OR = 6.33), and Maltese (OR = 3.87). Presence of a duplicated caudal vena cava was significantly associated with presence of extrahepatic portosystemic shunt(s) (P < 0.004). While uncommon in dogs, caudal vena cava duplication should be differentiated from other vascular anomalies when planning surgeries and for avoiding misdiagnoses.     

COMPUTED TOMOGRAPHY OF SPONTANEOUS CANINE NEOPLASMS*

Five spontaneous extracranial canine neoplasms studied by a computed tomography whole body scanner are presented: an undifferentiated sarcoma of the scapula, a mast cell sarcoma of the hip, a mast cell sarcoma of the neck, a fibrosarcoma of the neck, and a malignant melanoma of the gingiva. Computed tomography enables accurate detection and definition of tumor size and extent and is, therefore, an aid to diagnostic evaluation, therapy, and prognosis.