THE USE OF99mTc RADIOAEROSOL VENTILATION AND MACROAGGREGATED ALBUMIN PERFUSION IMAGING FOR THE DETECTION OF PULMONARY EMBOLI IN THE DOG

This study was undertaken to design protocol for use of radioaerosol of technetium-99m-labeled diethylenetriaminepentacetic acid (^99mTc-DTPA) for ventilation imaging as clinical tool in the dog and to evaluate imaging characteristics in both normal dogs and dogs with simulated pulmonary embolism. Clearance of the 99mTc-DTPA radioaerosol from the lung was also evaluated. Six normal dogs were used in two phases: (1) as their own controls and (2) during pulmonary artery occlusion using Swan-Ganz catheter. Radioaerosol ventilation images were obtained and rate of clearance from normal and occluded lungs determined. Perfusion studies using technetium-99m-macroaggregated albumin (^99mTc-MAA) immediately followed. Clearance half-times (T_1/2) were found to be significantly increased (p < 0.05) in acutely occluded lungs; however, the small magnitude of this change was visually difficult to detect on the ventilation images. Good quality initial ventilation and perfusion images were obtained and provided ready evaluation of ventilation (V), perfusion (Q), and induced V/Q mismatches. A clinical case of pulmonary thromboembolic disease was also evaluated with diagnostic result, indicating that this method of V/Q scintigraphy can provide useful information in those clinical cases in which pulmonary thromboembolism is suspected.     

A COMPARISON OF PULMONARY ANGIOGRAPHY, DIGITAL SUBTRACTION ANGIOGRAPHY, AND 99mTc-DTPA/MAA VENTILATION-PERFUSION SCINTIGRAPHY FOR DETECTION OF EXPERIMENTAL PULMONARY EMBOLI IN THE DOG

The abilities of pulmonary angiography, digital subtraction angiography and ventilation-perfusion scintigraphy (V/Q) to detect experimental acute pulmonary emboli were evaluated in a group of 18 research dogs. Emboli were produced by forceful intravenous injection of clotted blood. In five dogs, emboli were labeled with thallium-201 prior to reinjection so that embolus position could be confirmed on scintigraphic studies.
Studies were independently reviewed by three observers. Results were combined so that the relative sensitivity, specificity, and accuracy of each imaging technique could be compared using chi-square and receiver-operating characteristic curve analysis. Digital subtraction angiography and V/Q studies proved to be significantly more specific and accurate than conventional pulmonary angiography. V/Q studies were uniformly of good to excellent quality while the quality of digital subtraction angiography studies was variable depending on the adverse effects of respiratory motion. It was concluded that ventilation-perfusion scintigraphy is the best available method to screen dogs suspected of having pulmonary thromboembolism.     

SCINTIGRAPHIC EVALUATION OF FOUR DOGS WITH PROTEIN-LOSING ENTEROPATHY USING 111INDIUM-INDIUM-LABELED TRANSFERRIN

The purpose of this sutdy was to determine the clinical utility of ¹¹¹ In-labeled transferrin ( 111 In-TF) scintigraphy for evaluating dogs suspected of having protein-losing enteropathies. Four dogs were injected intravenoulsy with autologous ¹¹¹In-TF after 30 min incubation (at 37°C) of 18.5 MBq (0.5mCi) ¹¹¹In CI₃ with one ml of autologous plasma, Serial right lateral, left lateral and dorsal images were obtained 2, 4, and 24 hours post ¹¹¹ In-TF administration, Images were subjectively evaluated for the presence or absence of ¹¹¹ within the gastrointestinal tract. The results of total protein, albumin and globulin legels and results form gastrointestinal tract. the results of total protein, albumin and globulin levels and results from gastrointestinal biopsies were recorded. In one dog, a follow-up scientigraphic study was done six months after initial evaluation and initiation of treatment for plasmocytic-lymphocytic enteritis. Gastrointestinal activity was noted by two hours in two dogs, while all four dogs had gastrointestinal activity on the 24 hour images. The mean (±std dev) plasma protein, albumin and globulin levels were 3.5 (±0.9), 1.7 (±1) and 1.8 (±0.3) respectively at the time of initial presentation. In the one dog that was evaluated after therapy, faint visualization of radioactivity within the colon was noted on the 24 hour image. Based on this study, ¹¹¹In-TF appears to be a viable scientigraphic method for evaluating dogs with suspected dogs withfd suspected protein-losing enteropathies, Potential limitations of tjis radiopharmaceutical include cost and prolonged isolation of the animal prior to release to the client due to the long physical half-life (T_½= 2.82 days).     

LUMBO-SACRAL VERTEBRAL SINUS VENOGRAPHY VIA TRANSJUGULAR CATHETERIZATION IN THE DOG

A technic for percutaneous transjugular catheterization of the median sacral vein (MSV) was developed in the dog. This technic provides a means for visualizing the vertebral sinuses in the lumbo-sacral area. Temporary external occlusion of the caudal vena cava coincident with injection of contrast medium was necessary to get consistent, symmetrical filling of the vertebral sinuses. Dissections confirmed variation in location of the MSV and presence of valves at the terminus of this vessel. Angiograms performed using the seventh lumbar intervertebral vein, cranial gluteal vein, and internal iliac vein were less satisfactory due to incomplete filling of the vertebral sinuses.     

Contrast radiographic findings in canine bacterial discospondylitis: a multicenter, retrospective study of 27 cases

A multicenter, retrospective study was undertaken to evaluate contrast radiographic findings in canine bacterial discospondylitis. Records and myelograms or epidurograms of 27 patients were obtained from five colleges of veterinary medicine. Fifteen cases (56%) were evaluated as having some degree of spinal cord compression. The majority (73.3%) of the cases had only soft tissue as the compressive mass. The median compression for all cases was 5% of the vertebral canal. No difference was noted for compression based on anatomical site (i.e., cervical versus thoracolumbar versus lumbosacral). No significant correlation between degree of lesion compression and clinical outcome was noted, but there was a trend toward increased mortality with greater compression. There was no correlation between the ambulatory status and the ultimate outcome. Three of the 15 (20%) cases showed vertebral subluxation. Results of this study indicate that static spinal cord compression is not a significant component of the neurological dysfunction associated with bacterial discospondylitis. Identification of vertebral subluxation in some patients may indicate a dynamic lesion that should be evaluated with stress radiography.     

CT-GUIDED BRAIN BIOPSY USING A MODIFIED PELORUS MARK III STEREOTACTIC SYSTEM: EXPERIENCE WITH 50 DOGS

This report describes the results of CT-guided stereotactic brain biopsies performed on 50 consecutive dogs using a modified Pelorus Mark III Stereotactic System. Based on available histopathologic samples (stereotactic biopsy [n = 50], surgery [n = 17], necropsy [n = 9]) the patient population consisted of 34 dogs with primary brain tumors, 2 with invasive nasal adenocarcinomas, and 13 with non-neoplastic brain lesions. Brain tissue was not obtained from one dog. In 22 dogs a final diagnosis was made from tissue subsequently obtained from surgical resection or at necropsy. The final diagnosis was in agreement with the stereotactic biopsy diagnosis in 20 of these 22 dogs. In 17 other dogs without follow-up, stereotactic biopsy provided a diagnosis of a specific primary brain tumor subtype. Postoperative complications associated with the biopsy procedure were assessed in 41 dogs. The other 9 dogs either went directly to surgery (n = 7) or were killed (n = 2) immediately after the biopsy procedure. Thirty-six dogs recovered without apparent clinical complications. Postoperative clinical complications in the remaining 5 dogs included transient epistaxis (1 dog), transient exacerbation of cerebellar signs (1 dog), obtundation progressing to coma (1 dog), and medically uncontrollable seizures (2 dogs). The latter 3 dogs with severe neurologic complications all had large primary brain tumors and had been receiving high doses of phenobarbital and glucocorticoids to control seizures at the time of biopsy. These results suggest that this CT-guided biopsy procedure can provide an accurate pathologic diagnosis of brain lesions detected by CT and MR neuroimaging. Further refinement of both technique and case selection is expected to reduce the rate of clinical complications and to improve the accuracy of the procedure.     

EVALUATION OF SURVEY RADIOGRAPHY, LINEAR TOMOGRAPHY AND COMPUTED TOMOGRAPHY FOR DETECTING EXPERIMENTAL LESIONS OF THE CRIBRIFORM PLATE IN DOGS

Survey radiography, linear tomography, and computed tomography were used to image cribriform plate lesions that were created experimentally using intramedullary pins in 18 dog cadaver skulls. Computed and linear tomographic images were taken along the dorsal imaging plane. Studies were independently reviewed by five observers. Results were combined so that the relative sensitivity, specificity, and accuracy of each imaging technique could be compared using chi-square analysis. Computed tomography proved to be significantly more sensitive and accurate (p<0.05) than either linear tomography or survey radiography. Computed tomographic images were consistently of good to excellent quality for imaging the cribriform plate. It was concluded that computed tomography of the skull using a dorsal imaging plane was the best available imaging modality for detecting 3-mm and 5-mm experimentally created cribriform plate defects.     

Use of hepatobiliary scintigraphy to diagnose bile duct atresia in a lamb

A neonatal lamb was admitted with icterus, hypoglycemia, increased liver enzyme activities, and delayed sulfobromophthalein clearance. Biliary and pancreatic duct atresia were documented in this lamb at necropsy. Hepatobiliary scintigraphy was useful in reaching an antemortem diagnosis of bile duct obstruction. Hepatobiliary scintigraphy, using 1.5 mCi of 99m technetium-labeled acid, was performed on the affected lamb and on an age-matched control lamb. Using a large field-of-view camera equipped with a low-energy parallel-hole collimator, right ventral oblique images of the thorax and abdomen were obtained. Images were simultaneously recorded on microdot film by use of a dedicated nuclear medicine computer. In the control lamb, there was rapid clearance of radioactivity from the blood pool, coincident with obvious accumulation of radioactivity in the liver and followed by sequential accumulation in the intrahepatic biliary system, gallbladder, common bile duct, and small intestine. Results of the study in the affected lamb were characterized by prolonged blood-pool radioactivity without appreciable hepatic uptake and by excessive renal and urinary bladder activity in the later phases of the study. Hepatobiliary scintigraphy was a safe and non-invasive procedure that provided quantitative information about the degree of bile duct obstruction in the affected lamb.     

LEFT VENTRICULAR EJECTION FRACTION IN THE NORMAL HORSE DETERMINED BY FIRST-PASS NUCLEAR ANGIOCARDIOGRAPHY*

A method to perform first-pass nuclear angiocardiography (FPNA) in the conscious, standing horse is proposed. Technetium ?99m (0.75–1.0 mCi per 5 kg body weight) is injected as a bolus into the peripheral venous circulation. The passage of the radioactive bolus is recorded in listmode format using a dedicated nuclear medicine computer and a gamma camera. A semiautomatic equine cardiac computer program to calculate left ventricular ejection fraction (LVEF) is described. Effects of region-of-interest selection, background correction, portion of levophase analyzed, and sampling rate on ejection fraction values are discussed. Mean LVEF determined for a group of 13 normal horses using separate end-systolic and end-diastolic LV regions of interest for the middle three levophase beats and background correction was 71%±5%. Additional LV parameters recorded were LV ejection time, 429±78 milliseconds; LV ejection rate, ?1.9±.5 midsytolic volumes per second; LV filling time, 238±33 milliseconds; and LV filling rate, 2.4±0.5 midfast filling volumes per second. LVEF determinations were repeated three times in four horses to determine reproducibility of the method. Results were independently determined for three horses by four persons to assess interobserver error in processing data. Paired FPNA and electrical conductivity (EC) studies were performed on four horses to determine correlation of the two methods (FPNA=1.16 EC+9.16, R=0.75). FPNA is a safe and reproducible method to measure LVEF in the horse. Additional valuable information regarding cardiac function can be easily obtained using this technique.     

QUANTITATIVE HEPATIC SCINTIGRAPHY IN THE DOG

Quantitative hepatic scintigraphy is a noninvasive test for measurement of relative arterial and portal blood flow to the liver. This technique has been used to evaluate human patients with known or suspected liver tumors or diffuse hepatocellular disease. A computer program to assess the hepatic perfusion index (HPI) in the normal dog is described. Factors affecting study quality and accuracy include injection technique, cardiac function, patient position, respiration, gross patient motion, and user intervention during data processing. HPI for a group of 12 normal dogs was 0.9±0.4 (X±SD). Quantitative scintigraphy could be used to evaluate dogs with primary or secondary liver tumors, portacaval shunts, or chronic liver disease