COMPUTED TOMOGRAPHIC FINDINGS IN 35 DOGS WITH NASAL ASPERGILLOSIS

The purpose of this study was to describe the computed tomographic (CT) features of nasal aspergillosis in dogs. Initial (n = 35) and follow-up (n = 12) CT images were available from 35 dogs. The most commonly encountered CT findings were (1) moderate to severe cavitary destruction of the turbinates with presence of a variable amount of abnormal soft tissue in the nasal passages, (2) non-specific thickening of the mucosa adjacent to the inner surface of bones of the frontal sinus, maxillary recess and nasal cavity and, (3) thickened reactive bone. The findings were consistent with a disease initially affecting one nasal cavity then progressing into the ipsilateral frontal sinus, the contralateral nasal cavity and the contralateral frontal sinus. Two dogs with associated nasal foreign body had a more localized invasion of the nasal cavity. Attenuation values and contrast enhancement were not specific. With follow-up examinations, a reduction in the amount of abnormal soft tissue was observed in all dogs except one, but this reduction could not be quantified.     

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.     

COMPARISON OF RADIOGRAPHY, MYELOGRAPHY AND COMPUTED TOMOGRAPHY FOR THE EVALUATION OF CANINE VERTEBRAL AND SPINAL CORD TUMORS IN SIXTEEN DOGS

Radiographic, myelographic and computed tomographic (CT) studies from sixteen dogs with histologically diagnosed vertebral or spinal cord neoplasia (seventeen lesions) were retrospectively evaluated. Radiographs were compared with CT images to evaluate vertebral bony changes (bone production, lysis or both). Myelographic and CT images were evaluated to separate lesions into one of three categories, extradural, intradural/extramedullary, or intramedullary. These findings were compared to histologic tumor type from surgical or necropsy samples. Histologically, seven lesions were vertebral tumors and were classified as extradural lesions; ten lesions were spinal cord tumors of which eight were classified as intradural/extramedullary and two as intramedullary. Using CT, the amount of bony change associated with extradural lesions was greater than or equal to the amount of bony change visualized using radiographs. Myelography more correctly differentiated between intradural/ extramedullary and intramedullary lesions than did CT, although three open diagnoses detracted from the CT results. This study suggests that when evaluating extradural lesions, the amount of bony change was better visualized using CT than survey radiographs. Myelography was better when compared to CT for classifying spinal cord lesions, however, standardization of the CT imaging protocol may help determine the specific clinical indications for using CT in dogs with suspected vertebral or spinal cord tumors.     

COMPARATIVE PERFORMANCE OF RADIOGRAPHY AND COMPUTED TOMOGRAPHY IN THE DIAGNOSIS OF MIDDLE EAR DISEASE IN 31 DOGS

The purpose of this study was to compare computed tomography (CT) and radiography for diagnosing the presence and severity of middle ear disease in dogs with a history of chronic otitis externa. Thirty-one dogs undergoing a total ear canal ablation and bulla osteotomy were studied. Three normal dogs served as controls. All dogs were examined using radiography and CT. Three radiologists independently evaluated imaging studies in random order. A visual analog scale method was used for scoring certainty and severity of middle ear disease. Surgical findings were recorded intra-operatively. Bulla lining samples were submitted for histopathologic evaluation and scored by a single pathologist who also used a visual analog scale system. Findings from both imaging modalities agreed more closely with surgical findings than with histopathologic findings. With either surgical or histopathologic findings as the gold standard, CT was more sensitive than and as specific as radiographs for predicting presence and severity of middle ear disease. Observer performance with CT was more consistent than the performance with radiographs in the detection of changes that occur with middle ear disease. Both radiography and CT were more accurate for predicting the severity of the disease than its presence. Findings indicate that CT is more accurate and reliable than radiography in diagnosing middle ear disease for dogs having concurrent otitis externa, but only when severity of disease is moderate or high. With low severity of disease, diagnostic certainty for both modalities becomes more variable.     

AN OPTIMIZED PROTOCOL FOR MULTISLICE COMPUTED TOMOGRAPHY OF THE CANINE BRAIN

Computed tomography (CT) is commonly used in veterinary practice to evaluate dogs with suspected brain disease, however contrast resolution limitations and artifacts may reduce visualization of clinically important anatomic features. The purpose of this study was to develop an optimized CT protocol for evaluating the canine brain. The head of a 5‐year‐old Springer Spaniel with no neurological signs was imaged immediately following euthanasia using a 4‐slice CT scanner and 282 protocols. Each protocol used a fixed tube voltage of 120 kVp and 10 cm display field of view. Other acquisition and reconstruction parameters were varied. For each protocol, four selected images of the brain were reconstructed, anonymized and saved in DICOM format. Three board‐certified veterinary radiologists independently reviewed each of the four images for each protocol and recorded a numerical quality score for each image. The protocol yielding the lowest total numerical score was defined as the optimal protocol. There was overall agreement that the optimal protocol was the one with the following parameters: sequential mode, 300 mAs, 1 mm slice thickness, 1 s tube rotation time, medium image reconstruction algorithm and applied beam hardening correction. Sequential imaging provided optimal image resolution. The thin‐sliced images provided a small blur due to partial volume artifacts. A high tube current resulted in a relatively low noise level. Use of a medium frequency image reconstruction algorithm provided optimal contrast resolution for brain tissue. Use of a proprietary beam hardening correction filter (Posterior Fossa Optimization) markedly reduced beam‐hardening artifact.     

A COMPARISON OF RADIOGRAPHY, COMPUTED TOMOGRAPHY, AND MAGNETIC RESONANCE IMAGING FOR THE DIAGNOSIS OF PALMAR PROCESS FRACTURES IN FOALS

The relative sensitivity of radiography, computed tomography, and magnetic resonance imaging for detecting palmar process fractures of the distal phalanx in foals was determined and the imaging findings were compared with histomorphologic evaluations of the palmar processes. Compared to radiography, computed tomography and magnetic resonance imaging did not improve the sensitivity for detection of palmar process fractures. Statistical agreement for palmar process fracture diagnosis was excellent among the three imaging modalities. Histomorphologic evaluations were more sensitive for diagnosis of palmar process fracture than any of the imaging modalities. Three-dimensional image reconstructions and volume measurements of distal phalanges and palmar process fracture fragments from computed tomography studies provided more complete anatomical information than radiography. Magnetic resonance imaging confirmed that the deep digital flexor tendon insertion on the distal phalanx is immediately axial to the site where palmar process fractures occur, and differentiated cartilage, bone, and soft tissue structures of the hoof.     

COMPARISON OF RADIOGRAPHIC AND COMPUTED TOMOGRAPHY LYMPHANGIOGRAPHY FOR IDENTIFICATION OF THE CANINE THORACIC DUCT

Standard radiographic lymphangiograms and computed tomography (CT) lymphangiograms were performed on 10 female dogs without intrathoracic disease. Positive contrast lymphagiography was performed by injection into a catheterized mesenteric lymphatic vessel, and lateral thoracic radiographs, ventrodorsal thoracic radiographs, and thoracic CTs were obtained. The number of visible ducts was recorded for each image at the midbody of the ninth thoracic vertebra (T9) through the first lumbar vertebra (L1). Data were combined for all dogs at each data acquisition point. Data were analyzed by comparing data from all three images independently, and then by combining data for the radiographs and comparing the study with the highest number of visible duct branches to the CT. Significant differences in numbers of branches were found at T11 and L1. This study suggests that CT may be able to quantify branches of the thoracic duct more accurately than standard radiographic lymphangiography.     

RADIOGRAPHY OF THE CANINE NASAL CAVITY: SIGNIFICANCE OF THE PRESENCE OR ABSENCE OF THE TRABECULAR PATTERN

A radiographic study was performed on the maxilla of two healthy dogs to assess the effect of replacement of air by fluid and removal of conchae on the radiographic appearance. The purpose was to determine the significance of the presence or absence of the fine trabecular pattern on radiographs of the canine nasal cavity. The results indicate that the radiographic appearance of the maxillary conchae is primarily based on the presence of soft tissues covering the bony conchae, in combination with surrounding air. The radiographic appearance of the ethmoidal conchae is caused by the bony structures themselves. It is concluded that a loss of the characteristic parallel pattern in the cranial part of the nose is primarily the result of silhouetting of maxillary conchae by fluid. A loss of the fine trabecular pattern is caused by destruction of conchae.     

DIAGNOSTIC VALUE OF COMPUTED TOMOGRAPHY IN DOGS WITH CHRONIC NASAL DISEASE

Computed tomographic (CT) studies of 80 dogs with chronic nasal disease (nasal neoplasia (n = 19), nasal aspergillosis (n = 46), nonspecific rhinitis (n = 11), and foreign body rhinitis (n = 4)) were reviewed retrospectively by two independent observers. Each observer filled out a custom-designed list to record his or her interpretation of the CT signs and selected a diagnosis. Accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for the diagnosis of each disease. The agreement between observers was evaluated. The CT signs corresponded to those previously described in the literature. CT had an accuracy greater than 90% for each observer in all disease processes. The sensitivity, specificity, PPV, and NPV were greater than 80% in all dogs with the exception of the PPV of foreign body rhinitis (80% for observer A and 44% for observer B). There was a substantial, to almost perfect, agreement between the two observers regarding the CT signs and diagnosis. This study indicates a high accuracy of CT for diagnosis of dogs with chronic nasal disease. The differentiation between nasal aspergillosis restricted to the nasal passages and foreign body rhinitis may be difficult when the foreign body is not visible.     

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.     

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.     

COMPARISON OF COMPUTED TOMOGRAPHY AND ABDOMINAL RADIOGRAPHY FOR DETECTION OF CANINE MECHANICAL INTESTINAL OBSTRUCTION

Vomiting, often caused by mechanical intestinal obstruction, is common in dogs. Equivocal radiographic signs often necessitate repeat radiographs or additional imaging procedures. For our prospective, case‐controlled, accuracy study, we hypothesized the following: (1) using computed tomography (CT), radiologists will be more sensitive and specific for detecting mechanical intestinal obstruction and recommending surgery compared to using radiographs; and (2) using measurements, radiologists will be more sensitive and specific using radiographs or CT for detecting mechanical intestinal obstruction and recommending surgery. Twenty dogs had abdominal radiographs and abdominal CT. Seventeen dogs had abdominal surgery and three dogs were not obstructed based on clinical follow‐up. Confidence levels (five‐point scale) of three experienced radiologists for mechanical intestinal obstruction and recommending surgery were recorded before and after making selected measurements. Eight dogs had surgically confirmed mechanical intestinal obstruction, and 12 dogs did not have obstruction. For detecting mechanical intestinal obstruction, CT was more sensitive (95.8% vs. 79.2%) and specific (80.6% vs. 69.4%) compared to radiographs, but the difference was not statistically significant. For recommending surgery, radiography was more sensitive (91.7% vs. 83.3%) and specific (83.3% vs. 72.2%) than using CT, but differences were not statistically significant. We reported objective CT measurements for predicting small mechanical intestinal obstruction. By incorporating these objective data, the diagnosis of mechanical intestinal obstruction changed in five of 120 instances (radiographs and CT). In no instance (0/120), did the objective data change the recommendation for surgery. Using CT or abdominal radiographs for the detection of canine mechanical intestinal obstruction is sensitive and specific when evaluated by experienced veterinary radiologists.     

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.     

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.     

COMMUNICATIONS OF NORMAL NASAL AND PARANASAL CAVITIES IN COMPUTED TOMOGRAPHY OF HORSES

Heads from 15 male and female horses of various breeds and ages were examined with computed tomography under general anesthesia in dorsal recumbency. The main interest was the evaluation of the entire paranasal sinus system. Special attention was paid to the location, size, and shape of the conchomaxillary, nasomaxillary, frontomaxillary, and sphenopalatinal openings. The frontomaxillary opening was the largest aperture and was found to be age-dependent in size mostly. Orientation and shape of the openings were sagittal or horizontal; the narrowest of them was the slit-like nasomaxillary aperture. The thickness of the vascularized mucous membranes in the nasal cavity was obtained up to 6 mm; the surface was smooth and well defined. The paranasal lining was invisible in computed tomography (CT) images because of its thin layer. CT proved to be a very useful method for documentation of the paranasal openings and for evaluation of the state of the mucous membranes in the nasal and paranasal cavities.     

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.     

COMPUTED TOMOGRAPHY CHARACTERISTICS OF CANINE TRACHEOBRONCHIAL LYMPH NODE METASTASIS

Tracheobronchial lymph node evaluation is critical for accurate staging of canine thoracic neoplasia and is more accurately achieved with computed tomography (CT) than radiography. Thoracic CT scans of 18 canine patients with known tracheobronchial lymph node histopathology and 10 clinically normal dogs were compared to establish if enlargement or contrast enhancement pattern correlated with metastatic status. Absolute lymph node size and three anatomically normalized lymph node ratios were significantly correlated with metastasis or severe granulomatous lymphadenitis (P<0.0003). Transverse maximum lymph node diameter of 12 mm or lymph node to thoracic body ratio of 1.05 are proposed cutoffs, above which metastatic involvement is very likely; however, only minimal accuracy was gained with normalized ratios. Lymph node contrast enhancement pattern was also significantly correlated to disease. A heterogenous and/or ring pattern was related to metastatic disease (P=0.03). Recommended protocol for CT examination of the tracheobronchial lymph nodes is 1–1.5 mm slices and intervals, intravenous contrast, and control of respiratory motion.     

A REVIEW OF HIGH RESOLUTION COMPUTED TOMOGRAPHY AND A PROPOSED TECHNIQUE FOR REGIONAL EXAMINATION OF THE CANINE LUMBOSACRAL SPINE

High resolution computed tomography (CT) is a noninvasive imaging modality that has been used extensively in evaluating diseases of the human lumbosacral spine. Excellent spatial and contrast resolution, combined with multiplanar reformatting capability make high resolution CT scanners well-suited for similar applications in dogs. Consistently good quality images can be obtained when careful attention is given to factors affecting resolution. This paper reviews and illustrates some principles of high resolution CT, and proposes a technique for regional CT examination of the canine lumbosacral spine.     

THE EFFECTS OF PATIENT POSITIONING AND SLICE SELECTION ON CANINE ACETABULAR ANGLE ASSESSMENT WITH COMPUTED TOMOGRAPHY

Acetabular angles (AAs) and dorsal acetabular rim angles acquired by computed tomographic (CT) imaging have been used to assess patient response to juvenile pubic symphysiodesis surgery. The purpose of this study was to evaluate the effects of patient positioning and slice selection on these angles, and an attempt was made to devise a repeatable method of measuring these angles that would eliminate positioning effects. We found significant variation in AAs with small differences in pelvic tilt and slice selection. Dorsal acetabular rim angles were not affected. As a result of positioning differences from one CT study to the next, every attempt should be made to standardize pelvic tilt, or eliminate its effect on AAs by standardizing gantry angle in relation to an anatomic landmark that will not change over time. The floor of the sacral vertebral canal may be a reasonable landmark for this purpose and deserves further study.     

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.