A COMPARISON OF TWO-DIMENSIONAL ULTRASONOGRAPHY AND RADIOGRAPHY FOR THE DETECTION OF SMALL AMOUNTS OF FREE PERITONEAL FLUID IN THE DOG

The detection of small amounts of free peritoneal fluid in the canine patient can be a diagnostic dilemma. Ultrasonography and radiography have been advocated to detect intraabdominal fluid not detectable by physical exam. The purpose of this study was to determine the more sensitive method for detecting small amounts of free peritoneal fluid. Ultrasound examinations and radiographs were performed after increments (1 ml/lb body weight) of fluid were injected intraperitoneally. Ultrasonography detected fluid in one animal at 2 ml/lb. AH other animals had fluid detected at 3 ml/lb. With radiographs fluid could be detected with a high degree of accuracy at 4 ml/lb. The lateral view was more accurate than the ventrodorsal view in detecting fluid. The authors concluded that Ultrasonography is more sensitive than radiography and is the method of choice to detect small amounts of free peritoneal fluid.     

ULTRASONOGRAPHY VERSUS RADIOGRAPHY FOR DETECTION OF FLUID IN THE CANINE TYMPANIC BULLA

The tympanic bullae of 20 previously healthy cadaver animals were randomly filled with sterile saline or air. The heads were positioned using tape ties and a rostrocaudal open mouth radiograph taken. The resulting radiographs were assessed by a blinded ECVDI diplomate, with each tympanic bulla being recorded as being either air or fluid filled. Ultrasound examination of the bullae was performed, by a blinded assessor, using a B-mode 5 mHz sector probe (Sonotron-VingMed Sound A/S, PO Box 141, N3191, Horten, Norway) operating at 3 mHz. Each bulla was recorded as being either air or fluid filled. Results of radiography and ultrasonography were each compared to the actual status of the bulla in a chi square analysis. Sensitivity of radiography was 80%, with specificity of 65%. Ultrasonographic sensitivity was 100% and specificity 100%. Ultrasonography may in future provide a cheap, noninvasive, rapid and widely available method for diagnosing otitis media in clinical cases.     

COMPARISON OF COMPUTED RADIOGRAPHY AND CONVENTIONAL FILM-SCREEN RADIOGRAPHY OF THE EQUINE STIFLE

Major advantages of computed radiography are the potential reduction of dose and the possibility of postprocessing. In our study, we compared conventional radiographs to digital radiographs of the equine stifle by subjective evaluation of diagnostic quality when using a decreasing photon flux (mAs). Twelve equine stifle joints from horses of different weight and size were examined. Conventional and digital radiographs were performed identically in a caudocranial projection with the tube angled 15 degrees. A series of four radiographs was performed in each technique with an increasing photon flux starting with 2.5 mAs and going up to 5, 10, and 20 mAs. All radiographs were evaluated subjectively in a blinded fashion by seven readers in terms of contrast, bone structure, and diagnostic value and were graded using a 1-5 scale. Results from conventional and digitized radiographs were compared, and differences between the individual observers were analyzed statistically. Contrast, bone structure, and diagnostic value from digital images were rated significantly better than from conventional images (p < .001). For both techniques, a decrease in ranking was found with a decrease of photon flux. There was only slight interobserver variability. A dose reduction up to a factor of 4 compared to a 100 speed film-screen system seems to be possible without loss of information. Weight and size of the horse are not major influences.     

DIAGNOSTIC SENSITIVITY AND INTEROBSERVER AGREEMENT OF RADIOGRAPHY AND ULTRASONOGRAPHY FOR DETECTING TROCHLEAR RIDGE OSTEOCHONDROSIS LESIONS IN THE EQUINE STIFLE

Osteochondrosis lesions commonly occur on the femoral trochlear ridges in horses and radiography and ultrasonography are routinely used to diagnose these lesions. However, poor correlation has been found between radiographic and arthroscopic findings of affected trochlear ridges. Interobserver agreement for ultrasonographic diagnoses and correlation between ultrasonographic and arthroscopic findings have not been previously described. Objectives of this study were to describe diagnostic sensitivity and interobserver agreement of radiography and ultrasonography for detecting and grading osteochondrosis lesions of the equine trochlear ridges, using arthroscopy as the reference standard. Twenty‐two horses were sampled. Two observers independently recorded radiographic and ultrasonographic findings without knowledge of arthroscopic findings. Imaging findings were compared between observers and with arthroscopic findings. Agreement between observers was moderate to excellent (κ 0.48–0.86) for detecting lesions using radiography and good to excellent (κ 0.74–0.87) for grading lesions using radiography. Agreement between observers was good to excellent (κ 0.78–0.94) for detecting lesions using ultrasonography and very good to excellent (κ 0.86–0.93) for grading lesions using ultrasonography. Diagnostic sensitivity was 84–88% for radiography and 100% for ultrasonography. Diagnostic specificity was 89–100% for radiography and 60–82% for ultrasonography. Agreement between radiography and arthroscopy was good (κ 0.64–0.78). Agreement between ultrasonography and arthroscopy was very good to excellent (κ 0.81–0.87). Findings from this study support ultrasound as a preferred method for predicting presence and severity of osteochondrosis lesions involving the femoral trochlear ridges in horses.     

ULTRASONOGRAPHY OF PERIPHERAL NERVES IN THE NORMAL ADULT HORSE

A study of the ultrasonographic appearance and size of the sciatic, tibial, peroneal, suprascapular, radial, median, and ulnar nerves and a comparison with the anatomic size and location of these nerves in the normal adult horse is reported. Cadavers and live horses were studied. Landmarks for localization and techniques for nerve identification are described. The depth and diameter of each nerve at various locations and the success rate in imaging each nerve are reported. Statistically significant correlations were found between anatomically and ultrasonographically measured nerve depths and diameters. The success rate in identifying nerves was 70% in the live horses and 49% in cadavers, with the deep peroneal nerve being the easiest to identify. Some applications of this technique in horses are discussed.     

COMPARISONS AMONG RADIOGRAPHY,ULTRASONOGRAPHY AND COMPUTED TOMOGRAPHY FOR EX VIVO CHARACTERIZATION OF STIFLE OSTEOARTHRITIS IN THE HORSE

A better understanding of imaging characteristics of equine stifle osteoarthritis (OA) may allow earlier detection and improve prognosis. Objectives of this ex vivo, prospective, methods comparison study were to (1) describe the location and severity of naturally acquired OA lesions in the equine stifle using ultrasound (US), radiography (XR), computed tomography (CT), and macroscopic evaluation (ME); (2) compare the diagnostic performance of each imaging modality with ME; and (3) describe subchondral bone mineral density (BMD) in equine stifle joints with OA using CT. Radiographic, CT, and US evaluations were performed on 23 equine cadaver stifles and compared with ME. Significant associations were found between osteophyte global scores for all imaging modalities (CT, P ? 0.0001; XR, P = 0.005; US, P = 0.04) vs. ME osteophyte global scores. Osteophytes were detected most frequently in the medial femorotibial (MFT) joint. A specific pattern of osteophytes was observed, with a long ridge of new bone at the insertion of the MFT joint capsule cranially on the medial femoral condyle. A novel caudo‐10°proximo‐5°lateral‐cranio‐disto‐medial oblique radiographic projection was helpful for detection of intercondylar osteophytes. Multiplanar CT reformatted images were helpful for characterizing all osteophytes. Osteophyte grades at most sites did not differ among modalities. Low sensitivity/specificity for subchondral bone sclerosis and flattening of femoral condyles suggested that these signs may not be reliable radiographic and CT indicators of equine stifle OA. Equine stifle OA was associated with a decrease in BMD and specific sites of focal subchondral bone resorption/cyst formation were found in some specimens.     

DETECTION OF PNEUMOTHORAX AND PLEURAL EFFUSION WITH HORIZONTAL BEAM RADIOGRAPHY

Forty‐seven patients with a known history of thoracic trauma or clinical suspicion of pneumothorax were selected for thoracic imaging. The patient population was composed of 42 dogs and five cats. Standard vertical beam (VB) left and right lateral and ventrodorsal/dorsoventral (VD/DV) projections were obtained for each patient, and at least one horizontal beam (HB) projection (VD projection made in lateral recumbency). A total of 240 images were reviewed. Subjective assessment for the presence and degree of pneumothorax and pleural effusion was made more confidently with HB projections. Pneumothorax was identified in at least one projection in 26 patients (26 dogs) and pleural effusion in 21 patients (19 dogs and two cats). Pneumothorax and pleural effusion were present concurrently in 17 dogs. Pneumothorax and pleural effusion were graded for each image as absent, mild, moderate, or severe. Right (P<0.001) and left (P<0.05) lateral HB VD projections and the standard VB left lateral projection (P<0.05) were significantly more likely to detect and grade pneumothorax severely than the VB VD/DV views. The right lateral HB projection had the highest rate of detection and gradation of severity for pneumothorax compared with other views. VD/DV projections had the lowest sensitivity for detection of the pneumothorax and gradation of severity for pneumothorax and pleural effusion. No significant difference in diagnosis (P=0.9149) and grade (P=0.7757) of pleural effusion were seen between views, although the left lateral HB had both the highest rate of detection and grade of severity.     

COMPARISON OF FLAT-PANEL DIGITAL TO CONVENTIONAL FILM-SCREEN RADIOGRAPHY IN DETECTION OF EXPERIMENTALLY CREATED LESIONS OF THE EQUINE THIRD METACARPAL BONE

Radiographic diagnosis of equine bone disease using digital radiography is prevalent in veterinary practice. However, the diagnostic quality of digital vs. conventional radiography has not been compared systematically. We hypothesized that digital radiography would be superior to film-screen radiography for detection of subtle lesions of the equine third metacarpal bone. Twenty-four third metacarpal bones were collected from horses euthanized for reasons other than orthopedic disease. Bones were dissected free of soft tissue and computed tomography was performed to ensure that no osseous abnormalities were present. Subtle osseous lesions were produced in the dorsal cortex of the third metacarpal bones, and the bones were radiographed in a soft tissue phantom using indirect digital and conventional radiography at standard exposures. Digital radiographs were printed onto film. Three Diplomates of the American College of Veterinary Radiology evaluated the radiographs for the presence or absence of a lesion. Receiver operator characteristic curves were constructed, and the area under these curves were compared to assess the ability of the digital and film-screen radiographic systems to detect lesions. The area under the ROC curves for film-screen and digital radiography were 0.87 and 0.90, respectively ( P =0.59). We concluded that the digital radiographic system was comparable to the film-screen system for detection of subtle lesions of the equine third metacarpal bone.     

A COMPARISON OF REAL-TIME ULTRASOUND, PALPATION AND RADIOGRAPHY IN PREGNANCY DETECTION AND LITTER SIZE DETERMINATION IN THE BITCH

Fifty-five bitches were examined once, at different intervals for pregnancy. Manual Papation, B-mode real-time ultrasoungraphy, and radiography were used to confirm pregnancy and to count the number of fetuses present. Predicted numbers were compared to whelping data obtained from owners. Radiography was confined to the last trimester of pregnancy and had an overall accuracy of 100% in pregnancy detection and 93% in correct litter size determination. A proor qualtiy radiograph contributed to the one incorrect count estimate. Ultrasound and palpation were used in all three trimester phases starting 3 weeks post coitus. For pregnancy detection ultrasound was 94% accurate (no false positives) and palpation was 88% accurate (one false positive). For fetal counting, ultrasound was 36% accurate and palpation was 12% accurate. Recommendations for the use of ultrasound and radiography in pregnancy evaluation are reviewed.     

RADIOGRAPHY AND COMPUTED TOMOGRAPHY IN THE DIAGNOSIS OF NONNEOPLASTIC EQUINE MANDIBULAR DISEASE

We compared the information gained from computed tomography (CT) vs. radiography in horses with nonneoplastic disease of the mandible. We hypothesized that CT would provide additional diagnostic information. Medical records, radiographs, and CT images of horses with nonneoplastic mandibular disease evaluated between 1994 and 2008 were reviewed. Nineteen horses were identified; 11 had a tooth root abscess and related disease, four had a fracture of the teeth and/or mandible, and four had a nonneoplastic mass. Both CT images and radiographs allowed identification of diseased teeth that appeared clinically normal otherwise. CT allowed identification of teeth that were clinically affected but appeared normal radiographically. Parameters such as tooth pulp involvement, lamina dura destruction, presence of bone fragments, lingual and buccal mandibular bone periosteal reaction, and cortical bone destruction were more conspicuous with CT. Performing radiography and CT in horses with nonneoplastic mandibular disease provides a more complete evaluation than either technique alone. CT contributes additional information that could otherwise be overlooked with radiographs alone in horses with a mandibular fracture. CT provides ancillary information to radiographs in horses with dental infection or a nonneoplastic mass of the mandible.     

SCINTIGRAPHIC EVALUATION OF THE THORACIC SPINE IN THE ASYMPTOMATIC RIDING HORSE

Scintigraphic evaluation of the spinous processes of the equine spine has been done by subjective evaluation of radiotracer uptake in clinically abnormal horses. To determine the range of variation in asymptomatic riding horses, 33 normal horses were examined. Two 60 degrees oblique views of the thoracic and lumbar spine were evaluated subjectively, and a semi quantitative method based on standardized regions of interest in each spinous process in T10-L3 was also applied. A ratio between each spinous process and a reference area (Rib 15 or 16) was calculated. The effects of two different color displays and a smoothing filter were assessed. The results of the subjective evaluation was compared to the calculated ratios, and the associations between age, gender, weight, height, use and increased radiotracer uptake, and ratios were analyzed. No significant association was found between age, gender, weight, height, use and increased radiotracer uptake, or ratio. One or more areas of increased radiotracer uptake between T13 and T18 were common in the asymptomatic riding horse, which may have implications for the interpretation of clinical patients. The blue, green and red color display had a higher sensitivity for detecting increased radiotracer uptake compared to the continuous grayscale. The smoothing filter used in this study had no effect on the detection of areas with increased radiotracer uptake. The association between the results of the subjective evaluation and the semi quantitative method was apparent when analyzed in T13-17. To evaluate if the semi quantitative method can replace the subjective evaluation, studies on clinically affected horses are necessary.     

USE OF RADIOGRAPHY, COMPUTED TOMOGRAPHY AND MAGNETIC RESONANCE IMAGING FOR EVALUATION OF NAVICULAR SYNDROME IN THE HORSE

Radiographic evaluation of navicular syndrome is problematic because of its inconsistent correlation with clinical signs. Scintigraphy often yields false positive and false negative results and diagnostic ultrasound is of limited value. Therefore, we assessed the use of computed tomography and magnetic resonance imaging in a horse with clinical and radiographic signs of navicular syndrome. Cadaver specimens were examined with spiral computed tomographic and high-field magnetic resonance scanners and images were correlated with pathologic findings. Radiographic changes consisted of bony remodeling, which included altered synovial fossae, increased medullary opacity, cyst formation and shape change. These osseous changes were more striking and more numerous on computed tomographic and magnetic resonance images. They were most clearly defined with computed tomography. Many osseous changes seen with computed tomography and magnetic resonance imaging were not radiographically evident. Histologically confirmed soft tissue alterations of the deep digital flexor tendon, impar ligament and marrow were identified with magnetic resonance imaging, but not with conventional radiography. Because of their multiplanar capability and tomographic nature, computed tomography and magnetic resonance imaging surpass conventional radiography for navicular imaging, facilitating earlier, more accurate diagnosis. Current advances in imaging technology should make these imaging modalities available to equine practitioners in the future.     

ULTRASOUND APPEARANCE OF NORMAL LUNG BORDERS AND ADJACENT VISCERA IN THE HORSE*

B-mode ultrasound was utilized to define the borders of the lungs and surrounding viscera in a normal horse. Characteristic reverberation artifacts produced by the air-filled lung allowed accurate definition of the lung borders. The liver on the right and the spleen on the left were the predominant parenchymal organs identified. These two organs were seen adjacent to the lung and medial to the diaphragm. Recognition of the liver and spleen is important in evaluating equine pleural effusion.     

应用氟氯化钡铕高速增感屏对马牛胸部X线摄影条件的研究

应用氟氯化钡铕高速增感屏,采用变动千伏值和变动曝光时间投照法,通过对93例马、牛(含胸部疾病28例)胸部的投照试验.研究了马、牛胸部后肺野及心区的X线摄影条件,并就氟氯化钡铕高速增感屏和中速钨酸钙增感屏的摄片效果进行了比较。结果如下:1.变动千伏值投照法的投照条件:后肺野FFD150cm,8mAs,kVP=胸厚(cm) 50(马、黄牛)或胸厚(cm) 55(奶牛);心区FFD150cm,18mAs,kVP=胸厚(cm) 55(马、黄牛)或胸厚(cm) 55～60(奶牛)。2.变动曝光时间投照法的投照条件:采用固定80kVP、FFD120cm时,后肺野的mAs=胸厚(cm)/2—8～10(马、黄牛)或胸厚(cm)—25～26。心区由于投照例数少,尚不能得出结论。3.马、牛胸部X线摄影的质量,用氟氰化钡铕高速增感屏投照较用中速钨酸钙增感屏为佳。     

COMPARISON OF RADIOGRAPHY AND ULTRASONOGRAPHY FOR DIAGNOSING SMALL‐INTESTINAL MECHANICAL OBSTRUCTION IN VOMITING DOGS

A cross‐sectional study was performed on acutely vomiting dogs to compare the accuracy of radiography and ultrasonography for the diagnosis of small‐intestinal mechanical obstruction and to describe several radiographic and ultrasonographic signs to identify their contribution to the final diagnosis. The sample population consisted of 82 adult dogs and small‐intestinal obstruction by foreign body was confirmed in 27/82 (33%) dogs by surgery or necropsy. Radiography produced a definitive result (obstructed or not obstructed) in 58/82 (70%) of dogs; ultrasonography produced a definitive result in 80/82 (97%) of dogs. On radiographs, a diagnosis of obstruction was based on detection of segmental small‐intestinal dilatation, plication, or detection of a foreign body. Approximately 30% (8/27) of obstructed dogs did not have radiographic signs of segmental small‐intestinal dilatation, of which 50% (4/8) were due to linear foreign bodies. The ultrasonographic diagnosis of small‐intestinal obstruction was based on detection of an obstructive lesion, sonographic signs of plication or segmental, small‐intestinal dilatation. The ultrasonographic presence or absence of moderate‐to‐severe intestinal diameter enlargement (due to lumen dilatation) of the jejunum (>1.5 cm) was a useful discriminatory finding and, when present, should prompt a thorough search for a cause of small‐intestinal obstruction. In conclusion, both abdominal radiography and abdominal ultrasonography are accurate for diagnosing small‐intestinal obstruction in vomiting dogs and either may be used depending on availability and examiner choice. Abdominal ultrasonography had greater accuracy, fewer equivocal results and provided greater diagnostic confidence compared with radiography.     

THORACIC RADIOGRAPHY IN THE NEONATAL FOAL: A PRELIMINARY REPORT

Thoracic radiographs from 22 neonatal foals were reviewed to investigate the radiographic appearance of the thorax in normal, immature, and septicemic foals, and in foals with neonatal respiratory distress syndrome. The size and radiographic appearance of intrathoracic structures and abnormal lung opacities were evaluated. The craniocaudal and apicobasilar dimensions of the heart were 5.6–6.3 and 6.7–7.8 times the length of a midthoracic vetebral body, respectively, in normal, immature and septicemic foals. Apicobasilar measurements were greater (8.0–8.7) in the foals with respiratory distress syndrome. Normal foals had clear lung fields within 12 hours of birth. A more marked interstitial pattern was observed in immature and septicemic foals compared to normals. Diffuse air–space (alveolar) pattern with air bronchograms was seen in foals with respiratory distress syndrome. It was concluded from this series that thoracic radiographs taken 24–48 hours after birth may aid differentiation of normal foals, septicemic or immature foals, and foals with respiratory distress syndrome.     

ULTRASONOGRAPHY OF THE SOLAR ASPECT OF THE DISTAL PHALANX IN THE HORSE

Ultrasonographic examinations were performed on the solar aspect of the distal phalanx of 10 feet of five normal live horses (Group 1), 22 feet of seven normal cadavers (Group 2), and nine feet of five horses with pathology of the dorsal solar aspect of the distal phalanx (Group 3). Lateromedial radiographs of the distal phalanx were made in all groups, and in Group 2, digits were sagitally sectioned after imaging. The ultrasonographic and radiographic appearance of the sagittal solar aspect of the distal phalanx was described. Measurements of the distance between the sole and the distal tip of the distal phalanx (A), the solar aspect of the apex of the frog and the distal phalanx (B), and the body of the frog's surface and flexor surface of the distal sesamoid bone (C) were made ultrasonographically, radiographically, and on the sectioned cadaver specimens. There was no statistical difference between the radiographic, ultrasonographic, and direct cadaver measurements in A and C. In B, there was a statistical difference between the radiographic, ultrasonographic, and cadaver measurements-most likely as a result of the difference in trimming of the frog apex. Ultrasonographic and radiographic examination of the nine feet of the five horses in Group 3 were performed and the abnormalities described. Color flow and power Doppler ultrasonography were performed on the normal sagittal solar distal phalanx, on the impar distal sesamoidean ligament, and at the insertion of the deep digital flexor tendon on the facies flexoria of the distal phalanx. Power Doppler in these horses showed blood flow at 0.16-0.48 kHz at the tip of the distal phalanx and at 0.16 kHz at the deep digital flexor tendon insertion and in the impar distal sesamoidean ligament. Using color flow Doppler in normal horses mean blood flows ranged from 1.8 to 5.4 cm/s at the tip of the distal phalanx and 1.8-2.0 cm/s at the deep digital flexor tendon insertion and in the impar distal sesamoidean ligament.     

SURVEY OF THE USE OF RADIOGRAPHY VS. ULTRASONOGRAPHY IN THE INVESTIGATION OF GASTROINTESTINAL FOREIGN BODIES IN SMALL ANIMALS

A question frequently asked by clinicians who are treating small animals suspected of having gastrointestinal foreign bodies is whether one imaging test such as survey radiography or ultrasonography is sufficient to make the diagnosis. A study was undertaken to try and answer this question. Survey abdominal radiography and ultrasonography was performed on 16 small animals (11 dogs, five cats) with clinical signs of an obstruction because of a confirmed gastrointestinal foreign body. The majority of the foreign bodies (14/16) were confirmed by surgical removal and were located in the small intestine. A gastric foreign body was retrieved endoscopically and a colonic foreign body was passed in the feces. Radiographically identifiable foreign bodies were evident in nine animals. Small intestinal overdistension was present radiographically in seven animals. Ultrasonography detected a foreign body in all 16 animals. The foreign bodies were identified by their distal acoustic shadowing and variable degrees of surface reflection. An intestinal perforation was detected sonographically but not radiographically. The value of additional sonographic findings including thickening of the gastrointestinal wall and loss of layering, free peritoneal fluid, and lymphadenopathy in these animals is discussed. The findings in this series suggest that in a small animal with a gastrointestinal foreign body, ultrasonography alone could be used to make the diagnosis and may be a more appropriate choice than survey radiography.     

A 200 CENTIMETER FOCAL SPOT-FILM DISTANCE (FFD) TECHNIQUE FOR EQUINE THORACIC RADIOGRAPHY

The construction of a variable kVp, variable mA radiographic technique chart for the equine thorax using linear regression analysis is described. The independent variables in the analysis were body weight (pounds) and thoracic girth (inches) and the dependent variables were the radiographic exposure techniques (mAs, kV.p). Four areas (lateral views only) of each horse's thorax were radiographed using a focal spot-film distance (FFD) of 200 cm with the animal standing. The four views were craniodorsal, cranioventral, caudodorsal and caudoventral. For comparison, an additional caudodorsal view was made at 100 cm FFD to quantitate the decrease in exposure, the increased magnification and the decreased area of the lung exposed on the x-ray tube side of the horse compared with 200 cm FFD technique. Body weight was a satisfactory means to determine radiographic technique factors for thoracic radiographs in the horse. Thoracic girth (inches) was also measured and used to determine radiographic technique factors but was less exacting and less convenient than body weight.     

RADIOGRAPHIC EVALUATION OF INDUCED PNEUMOTHORAX IN THE DOG

Serial radiographic examinations were used to assess the incidence of bilateral and unilateral pneumothorax and its resolution following the introduction of air into a pleural space in each of 24 adult mix-breed dogs. Twenty-two (92%) dogs developed bilateral pneumothorax and two dogs (8%) developed unilateral pneumothorax. Volumes of air equal to 5 ml/kg, 15 ml/kg, and 45 ml/kg of body weight had resolved in all dogs developing bilateral pneumothorax by 7, 10, and 14 days, respectively. The vertical beam left lateral recumhent and the expiratory horizontal beam ventrodorsal views were the most effective radiographic views for the detection of pneumothorax. Separation of the visceral and parietal pleural surfaces on the horizontal beam ventrodorsal view was a better indication of small amounts of air in the pleural spaces than separation of the heart from the sternum on the vertical beam lateral view. The right lateral recumbent view, regardless of heam orientation, was most sensitive for the detection of differences in the amount of air in the pleural spaces.