Computed Tomography of the Mediastinum of the Dog by a Six-generation CT Scanner, Different Windows and Peroral and Intravenous Contrast Medium

The anatomical and clinical studies of computed tomography (CT) in the dog are still scarce. Particularly, there are few CT studies combining the use of rapid apparatus of the latest generation, the supply of contrast medium (digestive or intravenous) and the application of regional specific CT windows with different window width (WW) and window level (WL). The use of this CT methodology is particularly recommended in the evaluation of mediastinal masses, heart pathologies, etc. In this work the mediastinum of the dog was studied by using a sixth generation spiral CT scanner (Toshiba Ex Vision), belonging to the private Medical Institute of Radiology 'Irion' of Porto Alegre, Brazil. Four mixed-breed mature dogs (4–6 years, 15–20 kg) were used, two males and two females. The dogs were anaesthetized and kept at a maximum inspiration when getting the images. Previously, the urografin® contrast had been injected by peroral and intravenous (cephalic vein) via. Dogs were placed in a stretcher in sternal recumbency. Different CT windows were applied in order to increase the quality of the images and to obtain detailed attenuation shades of the mediastinum organs: soft tissue window (WW 652; WL -34), pulmonary window (WW 928; WL -680) and mediastinal-vascular window (WW 352; WL 220). The mediastinal space was studied craniocaudally from the level of the cranial cava vein, brachiocephalic trunk and left subclavian artery, to the caudal end of the lumbodiaphragmatic recess . The obtained images allowed a very good tomographic evidence of the great vessels, the heart, the thoracic portion of the trachea, the principal bronchi, the thoracic portion of the oesophagus, etc.     

Computed Tomography (Ct) of the Liver of the Dog by a Six-generation CT Scanner and Intravenous Contrast Medium

By computed tomography the liver has an intermediate degree of attenuation, with a CT value (HU) between 70 and 75. However, this number may vary according to the generation of the apparatus, the use of contrasts medium, the efficiency of the detector, etc. The purpose of the present work was to evaluate the liver of the dog and related structures by means of a six-generation spiral CT scanner (Toshiba Ex Vision [[Au: please provide manufacturers details for 'Toshiba Ex Vision': city, state code (if USA) and Country]]), and the previous injection of intravenous contrast medium via cephalic vein. Four half-breed mature dogs (4–6 years, 15–20 kg) were used, two males and two females. The dogs were anaesthetized and kept over a stretcher in sternal recumbency. To evaluate the liver two different CT windows with different window width and window level were applied: soft tissue window (WW 652; WL -34) and mediastinal-vascular window (WW 352; WL 220). The CT images obtained allowed an excellent resolution at the level of the hepatic lobules, the gall bladder, the porta vein, the hepatic artery, the caudal cava vein, etc. The attenuation shades of these structures were very similar in the two used windows, however a better contrast was obtained with the soft tissue window.     

Computed tomography (CT) of the lungs of the dog using a helical CT scanner, intravenous iodine contrast medium and different CT windows

The aim of this study was to determine the accuracy of helical computed tomography (CT) for visualizing pulmonary parenchyma and associated formations in normal dogs. CT scan was performed by using intravenous contrast medium and by applying different types of CT windows: soft tissue and lung windows, and high-resolution computed tomography of the lung. This technique allowed, especially with lung window types, a good view of the parenchyma, bronchial tree, vascular structures and pleural cavity. The selected images, with high anatomical quality and tissue contrast, may be a reference for future clinical studies of this organ. Thus, helical CT is a promising non-invasive method of diagnosing a wide variety of pulmonary diseases in dogs.     

Does the computed tomographic appearance of the lung differ between young and old dogs?

In computed tomographic (CT) images of humans, decreased lung attenuation, bronchial dilation, and/or thickening, air trapping, cysts, and thickened interlobular septa have been associated with increasing age. To determine if there are differences in the CT appearance of the lungs of young and old dogs that could affect interpretation of diagnostic studies, pulmonary CT images of dogs with conditions unrelated to the thorax were reviewed retrospectively in a case–control study. Computed tomography studies of 42 young dogs (range 0.3–4.8 years) and 47 old dogs (range 9–15.1 years) were jumbled and reviewed by an observer blinded to dog age. Computed tomography was performed under sedation in 62 (70%) dogs and under general anesthesia in 27 (30%). Heterotopic bone was more prevalent (62% vs. 14%) in old dogs. Lung collapse was significantly associated with old age, greater body weight, and anesthesia. There were no significant differences in median lung attenuation or occurrence of ground glass pattern, cysts, bronchial thickening, bronchial dilation, or degree of tracheal calcification. No examples of reticular pattern, emphysema, pleural thickening, or septal thickening were observed in any dog. Despite previous studies describing age‐related changes in the radiographic appearance of the lungs of old dogs, it appears that there are minimal observable differences in CT images. Old dogs are more likely to have visible foci of heterotopic bone and may be more prone to lung lobe collapse than young dogs, but neither of these differences should contribute to misdiagnosis of pulmonary disease.     

Anatomic study of the canine bronchial tree using silicone casts,radiography, and CT

This prospective anatomic study examined the canine lower airway lumen morphology by visual inspection, radiography, and CT of silicone casts of two dogs. Study results showed the lobar, bronchopulmonary segmental, and pulmonary lobular organization of the lungs grossly reflected in the hierarchically clustered branching structure of the bronchial tree. Study results also provided a basis for differentiating bronchial and bronchiolar patterns. Whereas images of silicone-filled bronchial lumens produced large-diameter, branching, tapering bands that radiated from the lung hilus, the pattern was different for small airways. Images of silicone-filled bronchiole lumens produced small-diameter, branching, tapering, nonradiating lines that created a speckled pattern resembling micronodules and, unexpectedly during radiography, small-diameter rings with air-filled lumens attributed to positive and negative summation shadows. Consequently, imaging patterns in dogs might be affected by pulmonary lobular morphology and might differentiate large and small airway diseases.     

COMPUTED TOMOGRAPHIC CHARACTERISTICS OF EOSINOPHILIC PULMONARY GRANULOMATOSIS IN FIVE DOGS

Canine pulmonary eosinophilic granulomatosis is a rare inflammatory pulmonary disease characterized by formation of eosinophilic granulomas that tend to obliterate the normal pulmonary architecture. The purpose of this retrospective study was to describe the CT characteristics of confirmed idiopathic pulmonary eosinophilic granulomatosis in a group of dogs. Five dogs met inclusion criteria. All patients were young adult dogs of variable breeds. No dog had concurrent occult heartworm disease. Computed tomographic characteristics most commonly included pulmonary masses and nodules of variable size, and lesions were most commonly located in the caudal lung lobes. Four dogs had large pulmonary masses with or without additional nodules and one dog had nodular lesions disseminated throughout the entire lung parenchyma. All large eosinophilic granulomas were smoothly margined, heterogeneous pulmonary masses displaying heterogeneous contrast enhancement. A honeycomb‐like enhancement pattern was observed in all but one mass and consisted of multiple hyperattenuating rims delineating central hypoattenuating areas, suggestive of bronchiectatic lung with peripheral enhancing airway walls and fluid‐filled, necrotic bronchial lumen. One dog had evidence of tracheobronchial lymphadenopathy. Findings indicated that canine eosinophilic pulmonary granulomatosis should be included as a differential diagnosis for dogs with CT characteristics of multiple pulmonary masses and/or nodules in caudal lung lobes, and a honeycomb‐like enhancement pattern in masses after intravenous administration of iodinated contrast medium.     

CT-soft tissue window of the cranial abdomen in clinically normal dogs: an anatomical description using macroscopic cross-sections with vascular injection

The aim of this study was to provide a detailed anatomic atlas of the cranial abdomen by means of computed tomography (CT). Three mature dogs, all mixed breed males, were used. The dogs were sedated, anaesthetized and positioned in sternal recumbency. CT scans from the eighth thoracic vertebra to the fourth lumbar vertebra were performed using a third-generation equipment (TOSHIBA 600HQ scanner) with 1 cm slice thickness. CT-images of the cranial abdomen were taken with soft-tissue window (WL: −14, WW: 658) settings. Dogs were killed and vascular-injection technique was performed: red and blue latex filled the vascular system. Injected dogs were frozen in the same position as used for CT examination and sectioned with an electric bandsaw at 1-cm-thick intervals. The cuts matched as closely as possible to the CT-images. The anatomic sections were compared and studied with the corresponding CT-images, and clinically relevant abdominal anatomic structures were identified and labelled on the corresponding CT-images. The results of our study could be used as a reference for evaluating CT-images of the canine cranial abdomen with abdominal diseases.     

COMPARISON OF SINGLE-SLICE COMPUTED TOMOGRAPHY PROTOCOLS FOR DETECTION OF PULMONARY NODULES IN DOGS

Two dogs (4 and 38 kg) with radiographic evidence of pulmonary nodules were evaluated using single-slice, helical computed tomography (CT). Each thorax was scanned using 12 combinations of examination parameters that included slice collimation width (3 and 5 mm for the small dog and 5 and 7 mm for the large dog), pitch (1, 1.5, and 2), and reconstruction interval (0.5 and 1). Sensitivity, specificity, and accuracy for nodule detection were evaluated for each protocol by three different observers, their results being compared with a consensus evaluation of images acquired with the protocol providing the best theoretic resolution (narrow collimation, pitch of 1, reconstruction interval of 0.5). For all observers, sensitivity and accuracy were significantly increased when using a protocol with narrow collimation ( P <0.0001–0.005 and P =0.0003–0.005, respectively). Pitch and reconstruction interval did not significantly influence the accuracy, sensitivity, or specificity for at least two of the observers. Additionally, nodule size (<3 mm vs. ≥3 mm) did not significantly affect nodule detection. Interobserver repeatability was variable among protocols (κ=0.32–0.78), highlighting the fact that nodule detection may be more dependent on the observer than on the choice of the CT protocol. For single-slice CT, the results of this study suggest that narrow collimation (3–5 mm, depending on the animal's size), a pitch of 2 and a reconstruction interval of 1 should be used in dogs for the detection of pulmonary nodules.     

COMPUTED TOMOGRAPHIC IMAGING OF INFILTRATIVE LIPOMA IN 22 DOGS

Twenty two dogs with an infiltrative lipoma had computed tomographic (CT) images acquired to evaluate the extent of local disease. Ten dogs had undergone at least one cytoreductive surgical procedure (range = 1-3; median = 2) prior to imaging. Twenty dogs had measurable disease on CT images; 2 dogs had diffuse disease at a previous surgical site that could not be measured. Tumor volume (n = 20) ranged from 20 to 5,632 cm3 (median = 345 cm3; mean = 996 cm3). None of the dogs had evidence of bone involvement on the CT images; 2 of the 22 dogs had tumors that did not come into direct contact with osseous structures. All dogs with measurable disease had evidence of a fat opacity mass with variable degrees of muscle infiltration. Eleven of 22 dogs were given intravenous contrast medium prior to image acquisition and there was not evidence of enhancement of the infiltrative lipoma in any dog. Based on CT images, tumors were classified as well-defined in 9 dogs, moderately well-defined in 4, not well-defined in 3 and a mix of well-defined and not well-defined in 6 dogs. Tumors tended to be less well-defined in regions where the infiltrative lipoma interdigitated with normal body fat. It appears CT imaging allows adequate discrimination of tumor with the caveat that differentiation of normal fat from infiltrative lipoma can be problematic.     

Bronchoalveolar lavage affects computed tomographic and radiographic characteristics of the lungs in healthy dogs

Bronchoalveolar lavage is a common diagnostic test for dogs with suspected pulmonary disease, however there is no published information on whether this procedure could affect the imaging characteristics of the lungs. Aims of this prospective experimental study were to describe computed tomography (CT) and radiographic features of the lungs after bronchoalveolar lavage in a sample of healthy dogs. Thoracic CT and radiographic images of eight healthy Beagles were acquired at the following time points: before bronchoalveolar lavage, immediately following bronchoalveolar lavage, and at 2, 4, 8, 12, and 24 h following bronchoalveolar lavage. Lung consolidation or interstitial patterns were seen in CT and radiographic images immediately after the procedure. Radiographic lung patterns resolved within 2 h and CT patterns resolved within 24 h. Resolution of the CT pulmonary patterns in the ventral areas of the lungs was delayed compared to the dorsal areas. Mean CT imaging scores differed over time (P < 0.001), while mean radiographic imaging scores did not differ over time. This study suggests that thoracic radiography and CT imaging assessments should precede bronchoalveolar lavage procedures if possible, or be performed at least 24 h afterward.     

Aortopulmonary window characterized with two- and three-dimensional echocardiogram in a dog

Aortopulmonary window is a rare congenital anomaly, resulting from incomplete septation of the truncus arteriosus into the aorta and the pulmonary artery during embryogenesis. The utility of three-dimensional (3D) echocardiogram has not been previously reported in dogs with aortopulmonary windows. The authors demonstrate the diagnostic potentials of 3D echocardiogram and its ability to more completely define the anatomical features of aortopulmonary window in a dog when compared to two-dimensional imaging. Ultimately 3D echocardiogram was considered to provide information critical to determining the feasibility of beating heart surgical correction in this case.     

COMPUTED TOMOGRAPHY BRONCHIAL LUMEN TO PULMONARY ARTERY DIAMETER RATIO IN DOGS WITHOUT CLINICAL PULMONARY DISEASE

Bronchiectasis is diagnosed in humans using multiple computed tomography (CT) criteria, the most important being dilatation of the bronchi. The most widely used criterion for detection of bronchial dilatation is a bronchial lumen to pulmonary artery diameter (bronchoarterial [BA]) ratio >1.0. No studies have been performed to determine the BA ratio in normal dogs. Thoracic CT images of 24 dogs without clinical pulmonary disease were reviewed. The BA ratio of the lobar bronchi of the left cranial (cranial and caudal parts), right cranial, right middle, left caudal, and right caudal lung lobes was measured. The mean of the mean BA ratio for all dogs was 1.45±0.21 (99% confidence interval [CI]=1.34–1.56). The mean of the mean BA ratio as determined by lung lobe was 1.45±0.04 (99% CI=1.41–1.49). The range of individual BA ratios was 0.8–2.0. There was no significant difference in mean BA ratios as a function of lung lobe ( P =0.60). The BA ratio in these clinically normal dogs was consistent and may be a useful tool in evaluating for bronchiectasis on CT images. BA ratios >2.0 were not identified in this population, suggesting a threshold to differentiate normal from abnormal bronchi.     

ULTRASONOGRAPHIC FINDINGS IN 14 DOGS WITH ECTOPIC URETER

To evaluate ultrasonography as an alternative to contrast radiography for diagnosis of ectopic ureter in dogs, ultrasonography of the urinary tract was performed prospectively in a series of urinary incontinent dogs anesthetized for contrast radiography. Fourteen dogs had ectopic ureter based on surgical, necropsy or unequivocal contrast radiographic findings. There were eight females and six males of a variety of breeds; five were Labrador retrievers. Mean (range) age at the time of diagnosis was 1.2 (0.2–4) years for females and 3.5 (0.3–5) for males (p < 0.05). Ectopic ureters were unilateral in five dogs (2 left; 3 right) and bilateral in nine dogs. Both ultrasound images and contrast radiographs were positive for 21 (91%) ectopic ureters; the same two ectopic ureters were not detected using either modality. The termination of each of the five normal ureters was visible on ultrasound images; two (40%) were visible on radiographs. Other ultrasonographic findings included dilatation of the ectopic ureter and/or ipsilateral renal pelvis in ten (43%) instances, evidence of pyelonephritis in two dogs (with enlargement of the contralateral kidney in one dog), and urethral diverticuli in one dog. Ultrasonography is a practical diagnostic test for ectopic ureter in dogs. In this series there was close correlation between the ultrasonographic and contrast radiographic findings for each ectopic ureter, but ultrasonography enabled more accurate determination of normal ureteral anatomy.     

Computed tomographic features of the normal canine thyroid gland.

The computed tomographic (CT) features of the normal thyroid gland were compiled from images acquired in 25 client-owned dogs without thyroid gland disease. The mean pre- and postcontrast attenuation values were 107.5 and 169.0 Hounsfield Units, respectively. After injection of intravenous contrast medium (600 mg iodine/kg), the apparent thyroid gland volume (both lobes combined) increased from a mean value of 1148.0 nm3 to a mean value of 1188.9 mm3. All thyroid lobes were homogeneous on pre- and postcontrast images. In a craniocaudal direction, the gland spanned a region from the 1st to the 8th tracheal ring and the right lobe was often more cranial than the left. On transverse images the lobe shape was ovoid in 72%, and its location was dorsolateral to the trachea in 90% of dogs. Parathyroid glands could not be identified and an isthmus connecting both thyroid lobes was only seen in one dog. Considering the excellent visibility of the normal canine thyroid gland, CT can be beneficial in the differentiation of thyroidal versus nonthyroidal neck masses. CT also yields potential in the staging of thyroid carcinomas.     

Computed Tomographic Lymphography of the Thoracic Duct by Mesenteric Lymph Node Injection

Objective— To document a novel technique to image the thoracic duct and its tributaries by contrast enhanced computed tomography (CT) lymphography.
Study Design— Clinical report.
Animals— Dogs (n=6) idiopathic chylothorax.
Methods— Ultrasonography was used to guide percutaneous injection of intestinal lymph nodes with nonionic iodinated contrast medium for preoperative CT lymphography of the thoracic duct in 6 dogs with chylothorax. Thoracic CT images were acquired immediately after contrast medium injection. All dogs had subtotal pericardectomy and thoracic duct ligation. Postoperative thoracic duct lymphography was performed in 3 dogs. Superficial cervical lymph node lymphography was performed in 2 dogs to determine cervical lymphatic contribution to thoracic effusions.
Results— Preoperative thoracic duct lymphography using this technique was successful in delineating the cisterna chyli, thoracic duct, and associated lymphatic vessels in all dogs. Immediate postoperative lymphography performed in 2 dogs revealed successful duct ligation in 1 dog and persistent lymphatic leakage in the other. A 1-month postoperative thoracic duct lymphogram performed in 1 dog revealed unsuccessful ligation or recannulation of 1 of 3 redundant vessels seen preoperatively.
Conclusion— Percutaneous CT lymphography results in excellent detection of the thoracic duct and abnormal thoracic duct drainage patterns both pre- and postoperatively. The contribution of superficial cervical lymph node drainage to reoccurrence of effusions can be evaluated.
Clinical Relevance— Percutaneous CT lymphography using ultrasound-guided contrast medium injection should be considered as an alternative to conventional open abdominal approaches to radiographic or CT lymphography.     

Use of computed tomography and minimum intensity projection in the detection of lobar pneumonia mimicking lung lobe torsion in a dog

A 10‐year‐old female spayed Dachshund was referred with progressive coughing for 1 month. The dog was tentatively diagnosed with right middle lung torsion based on pleural effusion, vesicular emphysema, abruptly ending bronchus in consolidated right middle lung, and no contrast enhancement of the affected lobe on radiography and computed tomography (CT). There was no evidence of torsion upon thoracotomy, and histological examination confirmed lobar pneumonia. The CT images were reevaluated using minimum intensity projection and revealed normal bronchial courses. The minimum intensity projection technique can be to assist in evaluation of the bronchial tree for dogs with suspected lung lobe torsion and other pulmonary diseases.     

PULMONARY ANGIOGRAPHY USING 16 SLICE MULTIDETECTOR COMPUTED TOMOGRAPHY IN NORMAL DOGS

We report a canine computed tomography (CT) pulmonary angiography technique using multidetector CT (MDCT). CT pulmonary angiography using a 16 slice MDCT was performed on five healthy, anesthetized beagles. A helical acquisition with pitch of 1.4 was used. The time delay for the angiographic study was determined using a bolus‐tracking program. A dose of 400 mg I/kg of nonionic contrast medium (Iohexol 300 mg I/ml) was administered to each dog via a cephalic catheter using an angiographic power injector at a rate of 5 ml/s. In two dogs a second study, using a contrast medium dose of 200 and 600 mg I/kg was performed. Arterial enhancement of transverse and reformatted images was classified subjectively as excellent, good, or poor, and assessed objectively by measuring Hounsfield units at the right main pulmonary artery. Angiographic studies were evaluated by two radiologists to determine the number of subsegmental arterial branches visualized. The median number of subsegmental arterial branches identified was five (range: 2–7). Based on the time attenuation curve obtained by the bolus‐tracking program, there was consistent enhancement of the right main pulmonary artery beginning at 6 s and peaking at 8 s in 4/5 dogs. The contrast medium dose of 400 mg I/kg produced good to excellent vascular enhancement in the same 4/5 dogs. A dose of 200 mg I/kg resulted in poor enhancement. CT pulmonary angiography using MDCT and an automated bolus‐tracking program allows rapid, consistent evaluation of the pulmonary vasculature using a single dose of 400 mg I/kg of contrast medium.     

POST-OPERATIVE COMPUTED TOMOGRAPHY IN TWO DOGS WITH CEREBRAL MENINGIOMA

Post-operative computed tomography (CT) has been described as a technique for diagnosing incomplete resection or recurrence of cerebral neoplasms in humans. The characteristics of immediate postoperative CT images in dogs with intracranial pathology are unknown. This report describes findings from preoperative, immediate post-operative, and 4 week to 9 month follow-up CT examinations in two dogs with histologically-confirmed cerebral meningiomas. In images of one dog after surgery there was mild contrast enhancement of the tissue surrounding the surgical site. This enhancement had resolved in later images and was probably the result of surgically induced trauma. In post operative images of the other dog there was significant hyperattenuation of the tissues around the surgical site. In post contrast images there was increased enhancement that was evident in later images. These findings, although not supported by necropsy, probably indicate incomplete excision of the tumor.