A COMPARISON OF NORMAL FELINE THORACIC RADIOGRAPHS MADE IN DORSAL VERSUS VENTRAL RECUMBENCY

Thoracic radiographs of 11 normal cats were made in dorsal (VD) and ventral (DV) recumbency with a vertically directed x-ray beam. These radiographs were compared subjectively and objectively with each other and with an additional pair of radiographs made with the cats in dorsal and ventral recumbency using a horizontally directed x-ray beam. Differences were found between VD and DV thoracic radiographs but they were minimal. In VD radiographs the caudal mediastinum and accessory lobe regïon of the lung were more clearly seen but cardiac shape varied somewhat. In DV radiographs, the appearance of the heart was more constant and caudal lobar pulmonary arteries more clearly seen. The results of this study indicated that both VD and DV radiographs are satisfactory for radiographic examination of the feline thorax     

THE EFFECT OF DORSAL VERSUS VENTRAL RECUMBENCY ON THE RADIOGRAPHIC APPEARANCE OF THE CANINE THORAX

The thorax of nine dogs was radiographed with a vertical beam in both dorsal (VD) and ventral (DV) recumbency. The radiographs were evaluated subjectively and objectively for differences in appearance. To help explain appearance differences, lateral thoracic radiographs were made with the dogs in dorsal and ventral recumbency using a horizontally (laterally) directed x-ray beam. The appearance of thoracic viscera in VD and DV vertical beam radiographs differed. In VD vertical beam radiographs the craniocaudal axis of the heart appeared longer, the heart had a more consistent positional relationship to the thoracic spine, a larger area of the accessory lung lobe was visible, and a greater length of the caudal vena cava was visible. In DV radiographs the caudal lobar pulmonary arteries were more easily identified. The selection of dorsal versus ventral recumbency for thoracic radiography should be based on the clinical status of the patient and the reason(s) for which the radiograph is being made.     

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.     

The clinical usefulness of the ventrodorsal versus dorsoventral thoracic radiograph in dogs

Differences exist in the ventrodorsal (VD) and dorsoventral (DV) radiographic views of the canine thorax. One view may be preferred over another because of how it portrays different areas of interest or different disease conditions. The VD view is indicated for evaluation of the cranial and caudal mediastinum, the caudal vena cava, and the accessory lung lobe, and in cases of pleural effusion. Indications for the DV view include assessment of a consistent cardiac silhouette, evaluation of the pulmonary lobar vessels, and evaluation of the structures of the dorsal thorax, such as hilar lymph nodes, the caudal dorsal lungs, trachea, mainstem bronchi, and left atrium.     

Thoractic radiographic appearance during lung inflation in neonatal calves

The effect of lung inflation on thoracic radiographic anatomy was determined in seven anesthetized calves less than one week of age. Radiographs were taken with the calves in dorsoventral (DV), ventrodorsal (VD), left and right lateral recumbency at functional residual capacity (FRC), at half inflation of the lung and at total lung capacity (TLC). Lung volumes were maintained by positive pressure ventilation. Increases in areas and linear dimensions during lung inflation were not uniform, being greatest in the caudal and especially the caudal ventral regions of the thorax. With inflation, heart size decreased and the heart shadow moved cauded as the diaphragm flattened. When the calf was shifted from the DV to the VD position, the heart displaced toward the left thoracic wall. Lung areas were larger on VD than on DV projections with the right lung being larger than the left. On lateral radiographs the most reliable, easily observed indication of the stage of lung inflation was the area bounded by the vena cava, the caudal heart border and the diaphragm. On the DV or VD radiographs the transthoracic width at the diaphragm was the best indicator of the degree of lung inflation.     

INFLUENCE OF CARDIAC CYCLE ON THE RADIOGRAPHIC APPEARANCE OF THE FELINE HEART

The effect of cardiac-cycle phase on the radiographic appearance of the feline heart was investigated. Results show that the size and shape changes in the cardiac silhouette due to the cardiac cycle were present in all three postural positions investigated. Cardiac size and shape changes were present more frequently and in more locations of the cardiac silhouette when patients were in ventral recumbency (DV) versus dorsal recumbency (VD). In most cases, the magnitude of differences was small and detection was facilitated by comparison viewing. It is suggested that these size and shape influences of the cardiac cycle on cardiac appearance should be kept in mind when interpreting feline radiographs for cardiac pathology.     

Effect of various thoracic radiographic projections on the appearance of selected thoracic viscera

OBJECTIVES: To assess the effect of different radiographic projections on thoracic width, as well as position and visibility of the trachea, principal bronchi, cardiac silhouette, aorta, caudal vena cava (CVC) and oesophagus. METHODS: Right lateral recumbency (RLR), left lateral recumbency (LLR), dorsoventral (DV) and ventrodorsal (VD) thoracic radiographs of 42 dogs were reviewed retrospectively. RESULTS: In 78 per cent of cases the thoracic width was significantly larger on the VD projection than on the DV projection. The angle of divergence formed by the principal bronchi was significantly larger on the VD projection than on the DV projection in 80 per cent of dogs. A cardiac silhouette bulge at 1 to 2 o'clock was apparent on the VD projection in 22 per cent of dogs but was never seen on DV projections. The descending aorta was more visible at the 4 to 5 o'clock cardiac silhouette level on the DV projection and laterally at the T8 level on LLR projections. The CVC was better seen on VD and LLR projections. The oesophagus was visible as a soft tissue opacity in LLR in large dogs with normal thoracic conformation in 35 per cent of cases. CLINICAL SIGNIFICANCE: The DV projection appears to be more reliable for assessing the cardiac silhouette, the descending aorta and the angle of divergence of the principal bronchi. The VD projection should be considered for evaluating the CVC. LLR should be used for assessing the descending aorta and CVC.     

PNEUMOPERICARDIOGRAPHY IN THE NORMAL DOG

To define the normal radiographic anatomy of the canine heart and pericardial space as outlined by air, pneumopericardiography was performed in ten normal, anesthetized dogs using a percutaneously introduced pericardial catheter. Room air was injected to produce pneumopericardiums without causing cardiac tamponade, and radiographs were obtained using a vertical beam with the dogs positioned in right lateral (RLAT), left lateral(LLAT), dorsal (VD), and ventral (DV) recumbency. Selective and nonselective angiocardiography was used to confirm the identity of the outlined structures. The RLAT and LLAT positions provided more information than the DV or VD positions. Pericardial air consistently outlined a distinct interventricular sulcus and the recesses around the aorta and pulmonary artery. The right auricle, outlined along the cranial heart border ventral to the ascending aorta in both RLAT and LLAT positions, varied considerably in size. The RLAT position best outlined structures to the left of midline, including the left auricle, interventricular sulcus, outflow region of the right ventricle, and the origin of the pulmonary artery. The LLAT position best demonstrated structures to the right of midline, including the right atrium, proximal part of the cranial and caudal vena cavae, and ascending aorta. The considerable range of normal variation between dogs in this study must be considered in the interpretation of clinical pneumopericardiograms.     

RADIOGRAPHIC HEART-VOLUME ESTIMATION IN NORMAL CATS

Heart volume mensuration was evaluated on conventional radiographs from eight normal cats in different body positions using computed tomography (CT). Heart volumes were calculated from orthogonal thoracic radiographs in ventral and dorsal recumbency and from radiographs exposed with a vertical X-ray beam in dorsal and lateral recumbency using the formula for an ellipsoid body. Heart volumes were also estimated with CT in ventral, dorsal, right lateral and left lateral recumbency. No differences between heart volumes from CT in ventral recumbency and those from CT in right and left lateral recumbency were seen. In dorsal recumbency, however, significantly lower heart volumes were obtained. Heart volumes from CT in ventral recumbency were similar to those from radiographs in ventral and dorsal recumbency and dorsal/left lateral recumbency. Close correlation was also demonstrated between heart volumes from radiographs in dorsal/ left lateral recumbency and body weights of the eight cats.     

THE EFFECT OF POSITIONING ON THE RADIOGRAPHIC APPEARANCE OF CAUDODORSAL MEDIASTINAL MASSES IN THE DOG

In this prospective study, the effect of thoracic positioning on the visibility and size of caudal esophageal masses caused by spirocercosis was investigated. Dorsoventral (DV), ventrodorsal (VD) as well as left lateral recumbent (LLR) and right lateral recumbent (RLR) thoracic radiographs of 28 dogs, diagnosed endoscopically with spirocercosis, were evaluated. The radiographic findings were compared with those of esophageal endoscopy. Masses were seen equally well in left vs. right recumbency as well as in DV vs. VD positions but in DV/VD views 86% of masses were detected whereas in lateral views only 50% of masses were identified. In spirocercosis-endemic areas DV and RLR views are advised as they also allow for better visualization of descending aorta aneurysms and to avoid interpreting the potentially normally visible esophagus in LLR in large dogs as a mass.     

A COMPUTED TOMOGRAPHIC STUDY OF VOLUME AND X-RAY ATTENUATION OF THE LUNGS OF BEAGLES IN VARIOUS BODY POSITIONS

The influence of body position on volume and x-ray attenuation of the lungs of three Beagles was investigated with computed tomography. In left and right lateral recumbency, the dependent lung had decreased volume and increased x-ray attenuation compared with ventral recumbency. Volume and x-ray attenuation of the nondependent lung, however, were unchanged. In dorsal recumbency, there was a vertical gradient of x-ray attenuation being increased dorsally and decreased ventrally compared with ventral recumbency where regional differences in x-ray attenuation were not found. Results indicate a risk of overlooking a mass in the dependent pulmonary parenchyma of dogs in lateral and dorsal recumbency. Regional differences in x-ray attenuation of the lungs of dogs can be avoided if the radiographs are obtained with the dog in ventral recumbency.     

Use of routine ventrodorsal radiographic views of the pelvis to assess inclination of the wings of the sacrum in dogs

OBJECTIVE: To determine the ratio of ventral-to-dorsal transverse diameters between the wings of the sacrum on ventrodorsal radiographic views of the pelvis in large dogs and to validate the reliability of this morphometric analysis for functional interpretation. SAMPLE POPULATION: Pelvic specimens from 40 large-breed dogs and radiographs of 113 large-breed dogs. PROCEDURE: In an anatomic and radiographic evaluation, the transverse dorsal diameter (TVDS) and transverse ventral diameter (TVV) between the wings of the sacrum were evaluated in sacrum specimens and on corresponding radiographs of the pelvis and sacrum. The ratio between TVV and TVDS (VD ratio) was calculated. Intraobserver reliability was determined by calculation of the coefficient of variation. In a retrospective radiographic evaluation, the VD ratio was determined in Rottweilers, Golden Retrievers, and German Shepherd Dogs. Correlations between VD ratio and breed, age, and sex were tested. RESULTS: The VD ratio was significantly higher in Rottweilers than in Golden Retrievers and German Shepherd Dogs, denoting an oblique alignment of the sacral wings in Rottweilers (ie, the dorsal aspects of the sacral wings were located more medially than the ventral aspects) and an almost sagittal alignment in the other breeds. The VD ratio was significantly associated with age but not with sex. CONCLUSIONS AND CLINICAL RELEVANCE: Sagittal alignment of the wings of the sacrum is considered to be biomechanically less efficient. These results provide a basis for further studies to evaluate radiographic assessment of the sacroiliac joints similar to the evaluation for hip dysplasia.     

Caudocranial horizontal beam radiographic projection for evaluation of femoral fracture and osteotomy repair in dogs and cats

A new radiographic projection of the femur was evaluated for use in the assessment of fracture or osteotomy repair in small animals. The view is obtained by directing the x-ray beam horizontally through the hind limb, from caudad to craniad, with the animal positioned in lateral recumbency, the hip flexed, and the stifle extended. Views obtained, using the new projection, were compared with the standard ventrodorsal views of the pelvis, with hind limbs extended. Osteotomy lines in the femoral shaft were significantly (P less than 0.01) more visible on the horizontal beam view. Significant difference was not evident in visibility of fracture lines between the 2 radiographic projections. The horizontal beam view was easily obtained, and equivalent to the standard ventrodorsal view for radiographic evaluation of femoral fracture and osteotomy repair.     

The radiology of the dog's diaphragm

The distinguishable radiographic features of the dog's diaphragm include the right and left crura, the intercrural cleft, the cupula and the phrenic origins of the postcava and cardiophrenic ligament. Of these the crura are the most mobile and in lateral recumbency the dependent one sags forward more than the upper. This causes the crura to appear parallel in right lateral recumbency but to cross one another in left lateral recumbency. It also often causes the liver to look larger, the postcava more dorsal and the kidneys further apart in right lateral recumbency than in left. In frontal (DV, VD) projection the diaphragm casts either a solitary dome-shaped shadow of the cupula alone, or a triple-domed clover-leaf diaphragm which includes the crura. Optimum radiographic technique and radiological diagnosis are not possible without an appreciation of the main factors which influence diaphragmatic form, namely, respiration, gravity, conformation and the geometrical factors associated with the projection. Résumé. Les caractéristiques radiographiques du diaphragme du chien, caractéristiques que l'on peut distinguer, comprennent la cuisse droit et la cuisse gauche, la division intercrurale, la coupole et les origines phréniques de la v. cave inférieure et du ligament cardiophrénique. De ceux-ci, les cuisses sont les plus mobiles et en position couchée celle qui est dépendante pend en avant plus que la cuisse supérieure. Cela fait que les cuisses semblent être parallèles en position couchée latérale à droite mais se croiser dans la position couchée latérale à gauche. Cela fait aussi que le foie, souvent, semble plus gros, la v. cave inférieure plus dorsale et les reins plus éloignés dans la position couchée latérale de droite que dans celle de gauche. Dans la projection frontale (DV, VD), le diaphragme projette soit une ombre solitaire en forme de dôme de la coupole seule, soit un diaphragme en forme de trèfle à triple dôme qui comprend les cuisses. Une technique optimum radiographique et un diagnostique radiologique ne sont pas possibles sans une appréciation des principaux facteurs qui influencent la forme du diaphragme, à savoir, la respiration, la gravité, la conformation et les caractéristiques géomètriques associées avec la projection. Zusammenfassung. Die unterschiedlichen radiographischen Merkmale von einem Hunde-Diaphragma schliessen die rechte und linke Crura ein, die Cupula und die phrenischen Ursprünge der V. cava inferior und der kardiophrenischen Sehne. Von diesen sind die Crura die beweglichsten und in liegender Stellung sackt die abhängige mehr vorwärts als die obere. Dieses läst die Crura parallel erscheinen in rechter liegender Stellung aber einander überkreuzend in linker liegender Stellung. Es verursacht auch oft die Leber grösser, die V. cava inferior mehr dorsal und die Nieren weiter auseinander, mehr in rechter liegender Stellung als in linker, scheinen zu lassen. In frontaler (DV, VD) Projektion wirft das Diaphragma entweder einen einzelnen domförmigen Schatten von der Cupula allein, oder ein dreidomiges Kleeblatt Diaphragma welches die Crura einschliesst. Optimale radiographische Technik und radiologische Diagnose sind nicht möglich ohne die Wahrnehmung der Hauptfaktoren welche die diaphragmatische Form beeinflussen, nämlich Atmung, Schwere des Falles, Korperbau und die geometrischen Merkmale die mit der Projektion verbunden sind.     

ASSESSMENT OF THREE RADIOGRAPHIC PROJECTIONS FOR DETECTION OF FLUID IN THE RABBIT TYMPANIC BULLA

Otitis media in the rabbit commonly results in fluid accumulation in the tympanic bulla. Radiographic detection of fluid in the tympanic bulla is only moderately sensitive in the dog and cat. The purpose of this study was to investigate the accuracy of radiographic detection of fluid in the rabbit tympanic bulla for three different radiographic projections. Forty rabbit cadavers were used. Half of the tympanic bullae were randomly allocated to be filled with soft tissue material. Following this procedure, each specimen was radiographed in three projections: dorsoventral (DV), rostro 40° ventral-caudodorsal (R40°V-CdDO), and left and right latero 40° ventral-laterodorsal (Lat40°V-LatDO). After imaging, each specimen was frozen and sectioned to determine the content of the tympanic bullae. Images were interpreted and scored independently by two board-certified radiologists. There was no significant difference in sensitivity or specificity between the three projections when compared with the gross findings following sectioning, but observer confidence was highest for the DV projection. Accuracy of radiographic fluid detection was similar to that reported in the dog and cat. The DV and R40°V-CdDO allow comparison of both tympanic bullae on a single radiograph, but the DV was subjectively easier to position, while the Lat40°V-LatDO requires two radiographs for comparison.     

RADIOGRAPHIC AND HISTOPATHOLOGIC CHARACTERISTICS OF PULMONARY FIBROSIS IN NINE CATS

Pulmonary fibrosis is a progressive fatal interstitial lung disease that is often idiopathic, occurs in multiple species, and may be caused by a number of inciting factors. The purpose of this retrospective, multicenter study was to describe the radiographic and histopathologic characteristics of idiopathic and induced pulmonary fibrosis in a group of cats. Cats with thoracic radiographs and histopathologically confirmed pulmonary fibrosis were recruited using the American College of Veterinary Radiology list serve. A board‐certified veterinary radiologist and diagnostic imaging intern reviewed radiographs and recorded characteristics by consensus. Findings from additional imaging modalities were also recorded when available. All histopathology samples were re‐reviewed by a veterinary pathology resident. A total of nine cats met inclusion criteria. All patients had a broad range of radiographic characteristics that included broncho‐interstitial pattern, alveolar pattern, pulmonary masses, pulmonary bullae, pleural effusion, and cardiomegaly. Cats with available echocardiographic studies had characteristics that included right ventricular dilation and hypertrophy and pulmonary arterial hypertension interpreted to be secondary to primary lung disease. Cats with available CT studies had characteristics that included focally increased soft tissue attenuation, masses, and ventral consolidation that exhibited no improvement with dorsal versus ventral recumbency. Histopathology showed pulmonary fibrosis, type II pneumocyte hyperplasia, and smooth muscle hypertrophy in all patients. Epithelial metaplasia was present only in one patient. Findings from the current study indicated that cats with pulmonary fibrosis have highly variable radiographic characteristics and that these characteristics may mimic other diseases such as asthma, pneumonia, pulmonary edema, or neoplasia.     

ASSESSMENT OF RESPIRATION‐INDUCED DISPLACEMENT OF CANINE ABDOMINAL ORGANS IN DORSAL AND VENTRAL RECUMBENCY USING MULTISLICE COMPUTED TOMOGRAPHY

Respiratory‐induced organ displacement during image acquisition can produce motion artifacts and variation in spatial localization of an organ in diagnostic computed tomography (CT) examinations. The purpose of this prospective study was to quantify respiratory‐induced abdominal organ displacement in dorsal and ventral recumbency using five normal dogs. All dogs underwent CT examinations using 64 multidetector row CT (64‐MDCT). A “3‐dimensional (3D) apneic CT exam” of the abdomen was acquired followed by a “4‐dimensional (4D) ventilated CT exam.” The liver, pancreas, both kidneys, both medial iliac lymph nodes, and urinary bladder were delineated on the 3D‐apneic examination and the organ outlines were compared to the maximum alteration in organ position in the 4D‐ventilated examination. Displacement was measured in dorsal‐to‐ventral (DV), right‐to‐left (RL), and cranial‐to‐caudal (CC) directions. Respiratory‐induced displacement of canine abdominal organs was not predictable and showed large variability in the three directions evaluated. For most canine abdominal organs, dorsal recumbency provided overall the least amount of displacement among all directions evaluated except for liver and urinary bladder. For liver, a large variability was found for all directions and a statistically significant difference was found only in the RL direction with ventral recumbency exhibiting less displacement (P = 0.0099). For the urinary bladder, ventral recumbency also provided less displacement but this was statistically significant only in the RL direction (P < 0.0001). Findings from this study indicated that dorsal recumbency may be preferred for minimizing respiratory motion artifacts in whole abdomen studies, but ventral recumbency may be preferred for liver and urinary bladder studies when respiration cannot be controlled.     

THE EFFECT OF POSITIONING ON THE APPEARANCE OF SELECTED CRANIAL THORACIC STRUCTURES IN THE DOG

In this retrospective study the effect of thoracic positioning on the visibility and size of selected cranial thoracic structures in dogs was investigated. Dorsoventral (DV), ventrodorsal (VD) as well as left lateral recumbent (LLR) and right lateral recumbent (RLR) thoracic radiographs of 17 large, 15 medium, and 10 small skeletally mature dogs were evaluated. The craniodorsal and cranioventral mediastinum, the cupula pleura and sternal lymph nodes were examined. The effect of obesity was also evaluated. The craniodorsal mediastinum was better delineated on DV radiographs and was wider on VD radiographs. The craniodorsal mediastinal width: width of T2 cranial end-plate on VD radiographs was 2.41 for all groups combined and obesity significantly influenced this value. The cranioventral mediastinum was more visible in RLR and VD radiographs. A normal sternal lymph node soft tissue opacity was seen most commonly in RLR in large breed dogs and had a mean length of 30 mm. The pulmonary cupula extended beyond the first rib on all views and extended more cranially and was better visualised on VD than DV views.     

Tracheal signs and associated vascular anomalies in dogs with persistent right aortic arch

Medical records of 55 dogs with 1 or more vascular rings around the esophagus and trachea were reviewed to determine the nature and frequency of related vascular anomalies and to determine the reliability of tracheal deviation on radiographs for the diagnosis of persistent right aortic arch (PRAA). Fifty-two (95%) of the 55 dogs had PRAA. Of the 52 dogs with PRAA, 44% had coexisting compressive arterial anomalies: 17 had retroesophageal left subclavian artery and 6 had double aortic arch with atretic left arch. Characteristic tracheal deviation was consistently present in dogs with PRAA. Moderate or marked focal leftward curvature of the trachea near the cranial border of the heart in dorsoventral (DV) or ventrodorsal (VD) radiographs was found in 100% of available radiographs of 27 dogs with PRAA. Moderate or marked focal narrowing of the trachea also was noted in 74% of DV or VD radiographs and 29% of lateral radiographs of the dogs. Tracheal position in 30 of 30 dogs with megaesophagus and 62 of 63 control dogs was midline or rightward in VD or DV radiographs. Histology in a neonatal dog with PRAA revealed evidence of tracheal deviation and compression even before birth. Focal leftward deviation of the trachea near the cranial border of the heart in DV or VD radiographs is a reliable sign of PRAA in young dogs that regurgitate after eating solid food, and contrast esophagrams are not necessary to confirm the diagnosis of vascular ring compression.