PSITTACINE SKULL RADIOGRAPHY

The psittacine skull is a complex anatomic structure, frequently traumatized but difficult to adequately image with standard radiographic procedures. Multiple views including a ventrodorsal, a lateral, and complementary oblique projections are necessary to fully evaluate potential skull fractures in the avian patient. Magnification radiography is a relatively easy procedure that aids the review of small osseous structures. Familiarity with psittacine skull anatomy greatly facilitates radiographic interpretation of cranial trauma.     

DIGITAL RADIOGRAPHY ARTIFACTS

Radiographic artifacts may mimic a clinical feature, impair image quality, or obscure abnormalities. With the development of digital radiography (DR), a new set of artifacts is introduced. Regardless of the technology, the classic technical errors that occur with film screen radiography still occur using DR. Artifacts created using computed radiography, DR, and incorrect image processing are discussed. Methods for correction of the artifacts are presented.     

RADIOGRAPHY OF THE CANINE HEAD

Through the use of a purebred dog skull collection, specific positioning recommendations were established for radiography for the three skull types. It is suggested that the central ray of the beam be maintained at the following mean angles relative to the hard palate for the rostrodorsal-to-caudoventral oblique projection of the foramen magnum: dolicocephalic, 30° mesaticephalic, 20° and brachycephalic, 10°. It is recommended that the head be axially rotated as follows to radiographically separate the roots of the superior canine teeth: dolicocephalic, 48° mesaticephalic, 43° and brachycephalic, 35°. If only the cheek teeth require evaluation, the head should be rotated as follows: dolicocephalic, 37° mesaticephalic, 34° and brachycephalic, 25°. For evaluation of the inferior cheek teeth, it is recommended that the head be rotated as follows: dolicocephalic, 46° mesaticephalic, 44° and brachycephalic, 28°. It is recommended that radiographs of the temporo-mandibular joint be made with the skull axially rotated 10° and longitudinally obliqued as follows: dolicocephalic, 10° mesaticephalic, 14° and brachycephalic, 27°. Suggestions for open-mouth projections for evaluation of the tympanic bullae are that the central ray maintain the following angles relative to the hard palate: dolicocephalic, 4° mesaticephalic, 9° and brachycephalic, 21°. It is recommended that a caudoventral-rostrodorsal oblique projection of the nasal cavity made at 30° to the hard palate replace the open-mouth ventrodorsal in brachycephalic breeds.     

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.     

RADIATION EXPOSURE DURING EQUINE RADIOGRAPHY

All personnel present in the X-ray examination room during equine radiography were monitored using low energy direct reading ionization chambers (pockets dosimeters) worn outside the lead apron at neck level. The individuals' task and dosimeter readings were recorded after each examination. Average doses ranged from 0 to 6 mrad per study. The greatest exposures were associated with radiography of the shoulder and averaged less than 4 mrad. The individual extending the horse's limb was at greatest risk although the individual holding the horse's halter and the one making the X-ray exposure received similar exposures.
A survey of the overhead tube assembly used for some of the X-ray examinations also was performed. Meter readings obtained indicated an asymetric dose distribution around the tube assembly, with the highest dose occurring on the side to which the exposure cord was attached.
Although the exposures observed were within acceptable limits for occupational workers, we have altered our protocol and no longer radiograph the equine shoulder unless the horse is anesthetized. Continued use of the pocket dosimeters and maintenance of a case record of radiation exposure appears to make the technologists more aware of radiation hazards.     

CONTRAST RADIOGRAPHY OF THE OVINE GASTROINTESTINAL TRACT

Contrast radiography of the alimentary canal was conducted in six adult sheep with barium sulfate (70% W/V, 25–30 ml/kg). A period of 12 hours was adequate for opacification of most parts of the gastrointestinal tract. The presence of contrast medium in different parts of the alimentary canal was noted for as long as 60 hours. The right lateral view was adequate for visualization of most structures, but the typical laminar mucosal pattern of the omasum and the spiral mucosal folds of the abomasum were demonstrated better on the ventrodorsal view.     

DENTAL RADIOGRAPHY IN THE DOG WITH A CONVENTIONAL X-RAY DEVICE

This study describes a method of using a conventional x-ray device and film-positioning system for dental radiography in dogs. This system is economical, safe and results in high quality dental radiographs.     

RADIOGRAPHY OF THE BOVINE CRANIOVENTRAL ABDOMEN

This study consists of a review of 115 consecutively accrued bovine cranial abdomial radiographs. The sensitivity and specificity of radiography in detecting traumatic reticuloperitonitis or pericarditis was 83% and 90%, respectively. Increased reticular size was associated with vagal indigestion. Increased reticulo-diaphragmatic separation did not correlate with a specific disease process, 25/35 (71%) cattle presented for radiographic examination with a 1 cm or longer metallic reticular foreign body unattached to a magnet had traumatic reticuloperitonitis. Standing lateral abdominal radiographs were determined to be a valuable tool in the diagnosis of cranial abdominal disorders in the bovine.     

COMPARISON OF COMPUTED TOMOGRAPHY, TANGENTIAL VIEW RADIOGRAPHY, AND CONVENTIONAL RADIOGRAPHY IN EVALUATION OF CANINE PELVIC TRAUMA

Thirteen dogs with fractures requiring surgical repair were evaluated by standard two-view (i.e., lateral and ventrodorsal) radiography, tangential view (ventro 20 degrees cranial-dorsocaudal [inlet] and ventro 20 degrees caudal-dorsocranial [outlet]) radiography, and computed tomography (CT). Radiographic and CT examinations were reviewed independently by the three authors, and specific anatomic sites were graded for the presence or possibility of lesions. The results of radiographic interpretations were compared to CT scan interpretations. Eighty-one percent of skeletal lesions detected by CT scans were diagnosed definitively radiographically. Differences between the interpretation of CT and radiographic examinations included abnormalities associated with soft-tissue structures (P < 0.0001), the sacroiliac joints (P = 0.02), and the acetabula (P = 0.04). Interpretation of the lateral/ventrodorsal and inlet/outlet radiographic series were not statistically different, although inlet views may be complimentary to the standard radiographic examination. Its use deserves further study. Reader variation was less on evaluation of CT examinations than radiographic examinations. CT multiplaner reformations and three-dimensional reconstructions were useful for surgical planning in seven dogs. CT scanning is superior to survey radiography in assessing skeletal and soft-tissue injuries in dogs with pelvic trauma, although all clinically significant surgical lesions were described accurately radiographically. Based on this small series, the routine CT examination of dogs with pelvic trauma may not be justifiable for diagnosis but may be advantageous for surgical planning, especially if acetabular fractures are suspected on radiographs.     

RADIOGRAPHY REVIEW: THE INTERSTITIAL PATTERN OF PULMONARY DISEASE

The interstitium supports and surrounds the blood vessels, lymph vessels, bronchi, and alveoli. One of the most common interstitial lung patterns is that of multiple, variably sized distinct nodules. Pulmonary granulomas, abscesses, and neoplasms usually have this radiographic appearance. Other interstitial patterns result from the summation of multiple areas of diseased perivascular and peribronchial interstitial tissue and/or alveolar septa. Diseases characterized by this unstructured increase in pulmonary density include pulmonary fibrosis, early dirofilariasis, interstitial edema, viral pneumonia, and certain types of metastatic neoplasia.     

PORTAL RADIOGRAPHY IN VETERINARY RADIATION ONCOLOGY: OPTIONS AND CONSIDERATIONS

Portal radiography involves the acquisition of images to visualize radiation treatment field(s) using the radiation treatment source. The standard has been the use of film-based systems with improvements over the years in film–screen technology providing near diagnostic quality images. More recent advances have included the development of digital systems with such notable improvements including ability to window/level images to enhance viewing and readability, and significant shortening of the time required to acquire images.     

SKULL RADIOGRAPHS: SILVER IMPREGNATION AS AN INTERPRETATION AID

Individual skull bones of newly killed young cats were stained with an aqueous solution of 0.5% silver nitrate. These bones became blackened grossly and more radiodense than adjacent unstained skull bones. It was possible to correlate the gross and radiographic appearance of selected bones stained with silver nitrate. This was a useful teaching aid.     

CONTRAST RADIOGRAPHY OF THE GASTROINTESTINAL TRACT IN SEA TURTLES

Intestinal obstruction by radiolucent foreign bodies is common in sea turtles. The absence of clinical signs and the extended fasting periods in these animals means that intestinal obstructions may not be diagnosed early. Digestive tract radiographic contrast procedures were performed to evaluate the gastrointestinal transit time and intestinal obstructions in loggerhead sea turtles. Barium sulfate and nonionic iodinate contrast medium were used for radiographic contrast procedures. Contrast medium was administered via a gastric tube or into the colon. These procedures are often necessary and are useful to document intestinal obstruction and foreign objects. The diagnostic procedures were not easily performed in some turtles, but often they were adequate for the diagnosis.     

PET FISH RADIOGRAPHY: TECHNIQUE AND CASE HISTORY REPORTS

Radiography can be used to aid in the diagnosis and treatment of pet fish diseases. Handling, restraint and radiographic technique for the radiographic examination of pet fish is described. Quality diagnostic images can be obtained with standard radiographic equipment and radiographic techniques. Fishes with undifferentiated sarcoma, swim bladder herniation and scoliosis are three clinical examples that are described where radiography was used in the management of the patient. Conventional radiography appears to be best for evaluating skeletal and swim bladder diseases. Alternate imaging techniques such as computed tomography and magnetic resonance imaging may enhance the evaluation of coelomic soft tissue structures.     

THE NORMAL XERORADIOGRAPHIC AND RADIOGRAPHIC ANATOMY OF THE ORANGE-WINGED AMAZON PARROT (AMAZONA AMAZONICA AMAZONICA)

The purpose of the study was to provide a reference for xeroradiographic and conventional radio-graphic anatomy of the orange-winged Amazon parrot ( Amazona amazonica amazonica ) as a representative of medium-sized psittacine birds that are commonly kept as pets. The head, body, wing, and pelvic limb of a mature bird were radiographed using xeroradiographic and conventional radiographic techniques. Ten xeroradiographs and ten corresponding radiographs were selected, and the xeroradiographs labeled to illustrate the normal radiographic anatomy of these regions. Also included is a short discussion of unique avian anatomic features which are important to clinical evaluation.     

IMAGING BASILAR SKULL FRACTURES IN THE HORSE: A REVIEW

Due to the complex nature of the anatomy of the equine head, superimposition of numerous structures, and poor soft tissue differentiation, radiography may be of limited value in the diagnosis of basilar skull fractures. However, in many horses radiographic changes such as soft tissue opacification of the guttural pouch region, irregular bone margination at the sphenoccipital line, attenuation of the nasopharynx, ventral displacement of the dorsal pharyngeal wall and the presence of irregularly shaped bone fragments in the region of the guttural pouches are suggestive of a fracture of the skull base. These findings in conjunction with physical examination findings and historical information may lead to a presumptive diagnosis of a fracture. When available and when the patient will accommodate the equipment, computed tomography may give a definitive diagnosis owing to its superior resolution and differentiation of soft tissue structures.     

DISTINGUISHING RHINITIS AND NASAL NEOPLASIA BY RADIOGRAPHY

To compare the incidence of radiographic signs in dogs with rhinitis and primary nasal neoplasia and to assess the performance of observers for distinguishing these conditions, the nasal radiographs of 72 dogs with either rhinitis (n = 42) or primary nasal neoplasia (n = 30) were examined by two independent observers using custom-designed forms to record their interpretations. Rhinitis was associated with a higher incidence of focal or multifocal lesions, localised soft tissue opacities, lucent foci, and a lack of frontal sinus involvement. Neoplasia was associated with soft tissue opacities and loss of turbinate detail that affected the entire ipsilateral nasal cavity, signs of invasion of the bones surrounding the nasal cavity, and soft tissue/fluid opacities within the ipsilateral frontal sinus. The signs with the highest positive predictive value (PPV) for rhinitis were absence of frontal sinus lesions and lucent foci in nasal cavity (PPV of each 82%), and invasion of surrounding bones for neoplasia (PPV 88%). There were no significant differences in the position of the lesion within the nasal cavity, incidence of unilateral versus bilateral lesions, calcified lesions, or absence of teeth. There was moderate agreement between observers about the diagnosis (kappa 0.59). Areas (SE) under ROC curves were 0.94 (0.03) and 0.96 (0.03) for observers A and B, respectively (not significantly different; P = 0.68). These results indicate a high accuracy for radiologists examining dogs with nasal diseases. Differentiation of rhinitis and nasal neoplasia should be based on finding combinations of radiologic signs that together have a high PPV. Differences in interpretation between experienced observers in this study suggest that certain signs are potential sources of error.     

COMPUTED TOMOGRAPHIC FEATURES OF SKULL OSTEOMYELITIS IN FOUR YOUNG DOGS

Computed tomography (CT) features of four immature to young adult dogs with osteomyelitis of the skull are described. Trauma or bite wounds were the cause of infection and Staphylococcus aureus was the most common pathogen. CT features were a combination of soft tissue thickening, bone lysis, and bone proliferation. Bone lysis was extensive in some dogs with a moth-eaten appearance and involved the calvarium, base of the skull, the frontal sinuses, and the temporomandibular joint. In other dogs it was more focal with thinning of the bone rather than complete lysis. Bone proliferation also varied in appearance from irregular palisading or spiculated to expansion and septation of the frontal bone. Sequestrum formation was seen in one dog. Widespread infection in one dog involved the tympanic bullae and the temporomandibular joint. Lysis of the calvarium resulted in bacterial meningitis in two dogs. One dog was euthanized and three were treated with surgical curettage of the affected bone and antibiotic therapy which resulted in resolution of the clinical signs in one dog whereas two dogs had recurrent disease. CT was very helpful for characterizing extent and localization of the infection. Despite the aggressive CT features, osteomyelitis should be considered especially in young animals with a history of trauma or bite wounds. The pathophysiology of skull bone infections is discussed.     

RADIOGRAPHY AND IMAGE-INTENSIFIED FLUOROSCOPY OF BARIUM PASSAGE THROUGH THE GASTROINTESTINAL TRACT IN SIX HEALTHY AMAZON PARROTS (AMAZONA AESTIVA)

Gastrointestinal contrast studies were performed in six clinically healthy blue-fronted Amazon parrots (Amazona aestiva) using radiography and image-intensified fluoroscopy. During examination, the birds were confined in a perspex cage. The quality of the lateral radiographs was adequate for assessment of the contrast medium-filled gastrointestinal tract. Thirty minutes after administration of 20 mL/kg of a 25% barium sulphate suspension directly in the crop, in all birds the ventriculus was totally outlined by barium. After 60 min, the small intestine was filled in five of six birds. After 180 min, the crop was empty in all birds. The barium-outlined ventriculus had differences in shape on radiographs of individual birds and also between birds. The colon and cloaca had further filling after 120 to 300 min. With image-intensified fluoroscopy, gastrointestinal motility was evaluated. Contractions of the crop were seen, and boluses of contrast medium passing through the esophagus toward the proventriculus were easily identified. Proventricular contractions were rarely noted, but ventriculus motility was present and clearly defined. The ventriculus had a mean of 3.7 contraction cycles/min. In the duodenum and small intestine, rapid antegrade and retrograde peristaltic movements in combination with segmental contractions were seen. In the colon, occasionally very slow peristaltic activity, mainly of segmental nature, was present. During the examinations, no defeacation was recorded. Confinement in a small perspex cage provides an adequate and handy radiological set-up for evaluation of gastrointestinal passage and motility in birds, minimizing the influences of stress and anesthesia.     

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.