Robert T. O'Brien

Thoracic computed tomography in feline patients without use of chemical restraint

Computed tomography (CT) and thoracic radiography were performed in nonsedated, nonanesthetized, cats with thoracic disease. The final diagnosis was obtained with echocardiography, cytology, histopathology, necropsy, or response to therapy. For CT imaging, cats were in a positioning device using a 16 multislice helical CT system. Fifty-four cats had CT imaging of which 50 had thoracic radiography. The most common diagnoses were lung neoplasia, lower airway disease, and cardiomyopathy (nine each). Other disease groups included mediastinal mass (eight), infection (seven), trauma (four), and hernia (three). CT provided additional correct diagnoses in 28% (14/50) and additional information in 74% (37/50) of the cats. Additional correct diagnoses achieved only with CT were most common for cats with lower airway disease. The most common additional findings with CT were lung nodules (n=4), lung masses (n=4), bronchiectasis (n=4), and mediastinal lymphadenopathy (n=3). Survey CT led to a significant different diagnosis or different prognosis in 20 of the 50 cats that were imaged both modalities. Contrast CT was performed in 19 cats, most commonly in cats with lung neoplasia (n=6), a mediastinal mass (n=4) or an infection (n=3), and provided additional correct diagnosis in two cats not achieved with survey CT. Thoracic CT using a positioning device in diseased awake cats is feasible, safe, and clinically useful.

COMPUTED TOMOGRAPHIC IMAGING OF DOGS WITH PRIMARY LARYNGEAL OR TRACHEAL AIRWAY OBSTRUCTION

Seventeen dogs with clinical signs attributable to nonneoplastic obstruction of the larynx, trachea, or large bronchi underwent computed tomography (CT) imaging. In 16 of the 17 dogs, CT was performed without general anesthesia using a positioning device. Fifteen of these 16 dogs were imaged without sedation or general anesthesia. Three-dimensional (3D) internal rendering was performed on each image set based on lesion localization determined by routine image planes. Visual laryngeal examination, endoscopy, video fluoroscopy, and necropsy were used for achieving the cause of the upper airway obstruction. The CT and 3D internal rendering accurately indicated the presence and cause of upper airway obstruction in all dogs. CT findings indicative of laryngeal paralysis included failure to abduct the arytenoid cartilages, narrowed rima glottis, and air-filled laryngeal ventricles. Laryngeal collapse findings depended on the grade of collapse and included everted laryngeal saccules, collapse of the cuneiform processes and corniculate processes, and narrowed rima glottis. Trachea abnormalities included hypoplasia, stenosis, or collapse syndrome. The CT findings in tracheal hypoplasia consisted of a severely narrowed lumen throughout the entire length. Tracheal stenosis was represented by a circumferential decrease in tracheal lumen size limited to one region. Tracheal collapse syndrome was diagnosed by severe asymmetric narrowing. Lobar bronchi collapse appeared in CT images as a narrowed asymmetric lumen diameter. CT imaging of unanesthetized dogs with upper airway obstruction compares favorably with traditional definitive diagnostic methods.

COMPARISON BETWEEN SURVEY RADIOGRAPHY, B‐MODE ULTRASONOGRAPHY, CONTRAST‐ENHANCED ULTRASONOGRAPHY AND CONTRAST‐ENHANCED MULTI‐DETECTOR COMPUTED TOMOGRAPHY FINDINGS IN DOGS WITH ACUTE ABDOMINAL SIGNS

Contrast-enhanced multi-detector computed tomography (CE-MDCT) is used routinely in evaluating human patients with acute abdominal symptoms. Contrast-enhanced ultrasound (CEUS) continues to be in its infancy as it relates to evaluation of the acute abdomen. The purpose of this study was to compare survey radiography, B-mode ultrasound, CEUS, and CE-MDCT findings in canine patients presenting with acute abdominal signs; with a focus on the ability to differentiate surgical from non-surgical conditions. Nineteen dogs were prospectively enrolled. Inclusion required a clinical diagnosis of acute abdominal signs and confirmed surgical or non-surgical causes for the clinical signs. Agreement for the majority of recorded imaging features was at least moderate. There was poor agreement in the identification of pneumoperitoneum and in the comparison of pancreatic lesion dimensions for B-mode vs. CEUS. The CT feature of fat stranding was detected in cases including, but not limited to, gastric neoplasia with perforation, pancreatitis, and small intestinal foreign body. Ultrasound underestimated the size and number of specific lesions when compared with CE-MDCT. Contrast-enhanced ultrasound was successful in detecting bowel and pancreatic perfusion deficits that CE-MDCT failed to identify. Accuracy for differentiation of surgical vs. non-surgical conditions was high for all modalities; 100%, 94%, and 94% for CE-MDCT, ultrasonography and survey radiography respectively. Findings indicated that CE-MDCT is an accurate screening test for differentiating surgical from non-surgical acute abdominal conditions in dogs. Focused CEUS following CE-MDCT or B-mode ultrasonography may be beneficial for identifying potentially significant hypoperfused lesions.

Safety of contrast-enhanced ultrasonography in dogs and cats: 488 cases (2002-2011)

OBJECTIVE To determine the incidence of adverse events within 24 hours after contrast-enhanced ultrasonography (CEUS) in dogs and cats and compare the risk of death within 24 hours after imaging for animals that underwent ultrasonography with and without injection of a contrast agent. DESIGN Retrospective case-control study. ANIMALS 750 animals (411 case dogs, 238 control dogs, 77 case cats, and 24 control cats). PROCEDURES At 11 institutions, medical records were reviewed of dogs and cats that had CEUS performed (cases) as were medical records of dogs and cats with clinical signs similar to those of case animals that had ultrasonography performed without injection of a contrast agent (controls). Information regarding signalment; preexisting disease; type, dose, and administration route of contrast agent used; immediate (within 1 hour after CEUS) and delayed (> 1 and ≤ 24 hours after CEUS) adverse events; and occurrence and cause of death (when available) was extracted from each medical record. Risk of death within 24 hours after ultrasonography was compared between case and control animals. RESULTS Of the 411 case dogs, 3 had immediate adverse events (vomiting or syncope) and 1 had a delayed adverse event (vomiting). No adverse events were recorded for case cats. Twenty-three of 357 (6.4%) clinically ill case animals and 14 of 262 (5.3%) clinically ill control animals died within 24 hours after ultrasonography; risk of death did not differ between cases and controls. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that CEUS was safe in dogs and cats.

FEASIBILITY FOR USING DUAL‐PHASE CONTRAST‐ENHANCED MULTI‐DETECTOR HELICAL COMPUTED TOMOGRAPHY TO EVALUATE AWAKE AND SEDATED DOGS WITH ACUTE ABDOMINAL SIGNS

Canine patients with acute abdominal signs are often clinically unstable and need a rapid and accurate diagnosis. Contrast-enhanced multi-detector computed tomography (CT) is the current modality of choice for evaluating acute abdominal pain in people. We hypothesized that contrast-enhanced multi-detector CT would be a feasible and safe technique for use in awake and lightly sedated dogs with acute abdominal signs. Eighteen client-owned dogs were enrolled, all presenting with acute abdominal signs. Dogs were scanned using a dual-phase protocol that included precontrast, arterial, and portal venous phases. Eight dogs were scanned awake and ten were given light sedation as chosen by the primary care clinician. Two observers who were unaware of clinical findings and sedation status scored image quality for each scan by consensus opinion. Mean serum creatinine in the sedated group was higher than in the awake group but was within the normal reference range. Other laboratory and physiologic measures did not differ between awake and sedated groups. No IV contrast-related adverse reactions were seen. Median scan time for all patients was less than 10 min. Sixteen of 18 contrast-enhanced multi-detector CT scans were scored fair to excellent in diagnostic quality, with no statistical difference in diagnostic quality for awake vs. sedated patients. Causes for two poor quality diagnostic scans included severe beam hardening from previously administered barium contrast agent and severe motion artifacts. We conclude that dual-phase contrast-enhanced multi-detector CT is a feasible and safe technique for evaluating awake and minimally sedated dogs presenting with acute abdominal signs.

Intraoperative contrast-enhanced ultrasonography of normal canine jejunum.

Nine normal juvenile dogs were evaluated with direct jejunal contrast-enhanced ultrasonography via midline celiotomy. Three different doses of ultrasound contrast medium (Definity®) were injected through a peripheral venous catheter. Time-intensity curves were used to calculate baseline, time to initial rise, inflow slope, time-to-peak, peak intensity (PI), and outflow slope for each administered dose. PI was directly proportional to dose. Outflow slope was similar for all patients, independent of dose. The most favorable images were acquired with a dose of 0.030 ml/kg given as a rapid intravenous manual bolus. The technique and normal jejunal perfusion pattern described herein may provide useful data for evaluation of intestinal vascular, inflammatory, and neoplastic disease in the dog.

COMPUTED TOMOGRAPHY OF NONANESTHETIZED CATS WITH UPPER AIRWAY OBSTRUCTION

Upper airway obstruction is a potentially life-threatening problem in cats and for which a noninvasive, sensitive method rapid diagnosis is needed. The purposes of this prospective study were to describe a computed tomography (CT) technique for nonanesthetized cats with upper airway obstruction, CT characteristics of obstructive diseases, and comparisons between CT findings and findings from other diagnostic tests. Ten cats with clinical signs of upper airway obstruction were recruited for the study. Four cats with no clinical signs of upper airway obstruction were recruited as controls. All cats underwent computed tomography imaging without sedation or anesthesia, using a 16-slice helical CT scanner and a previously described transparent positional device. Three-dimensional (3D) internal volume rendering was performed on all CT image sets and 3D external volume rendering was also performed on cats with evidence of mass lesions. Confirmation of upper airway obstruction was based on visual laryngeal examination, endoscopy, fine-needle aspirate, biopsy, or necropsy. Seven cats were diagnosed with intramural upper airway masses, two with laryngotracheitis, and one with laryngeal paralysis. The CT and 3D volume-rendered images identified lesions consistent with upper airway disease in all cats. In cats with mass lesions, CT accurately identified the mass and location. Findings from this study supported the use of CT imaging as an effective technique for diagnosing upper airway obstruction in nonanesthetized cats.

Effect of MK‐467 on organ blood flow parameters detected by contrast‐enhanced ultrasound in dogs treated with dexmedetomidine

OBJECTIVE To evaluate the dexmedetomidine-induced reduction in organ blood flow with quantitative contrast-enhanced ultrasound (CEUS) method and to observe the influence of MK-467 on such reduction. STUDY DESIGN Randomized cross-over study. ANIMALS Six adult purpose-bred laboratory beagle dogs (mean body weight 15.3 ± 1.9 kg). METHODS Contrast-enhanced ultrasound was performed on six conscious healthy laboratory beagles. The animals on separate occasions underwent three treatments: awake without any medication (CTRL), dexmedetomidine 10 μg kg(-1) (DEX) and DEX + MK-467 500 μg kg(-1) (DMK) intravenously (IV). The kidney (10-15 minutes post-treatment), spleen (25-30 minutes post-treatment), small intestine (40-45 minutes post-treatment) and liver (50-55 minutes post-treatment) were examined with CEUS. A time curve was generated and the following perfusion parameters were analysed: arrival time (AT), time to peak from injection (TTPinj), peak intensity (PI) and wash-in rate (Wi). In addition to CEUS, renal glomerular filtration rate was indirectly estimated by the rate of iohexol elimination. RESULTS AT and TTPinj were significantly higher for DEX than for CTRL in all studied organs. The same parameters were significantly higher for DEX than for DMK in the kidney, spleen and small intestine. PI was significantly lower for DEX than for CTRL or DMK in the kidney. Wi was significantly lower for DEX than for CTRL or DMK in the kidney and significantly lower than for CTRL only in the small intestine. Plasma concentration of iohexol was significantly higher after DEX than CTRL administration. CONCLUSIONS Contrast-enhanced ultrasound was effective in detecting DEX-induced changes in blood flow. MK-467 attenuated these changes. CLINICAL RELEVANCE Clinicians should consider the effects of the sedation protocol when performing CEUS. Addition of MK-467 might beneficially impact the haemodynamic function of sedation with alpha-2 adrenoceptor agonists.

Qualitative and quantitative interpretation of computed tomography of the lungs in healthy neonatal foals

OBJECTIVE To qualitatively describe lung CT images obtained from sedated healthy equine neonates (≤ 14 days of age), use quantitative analysis of CT images to characterize attenuation and distribution of gas and tissue volumes within the lungs, and identify differences between lung characteristics of foals ≤ 7 days of age and foals > 7 days of age. ANIMALS 10 Standardbred foals between 2.5 and 13 days of age. PROCEDURES Foals were sedated with butorphanol, midazolam, and propofol and positioned in sternal recumbency for thoracic CT. Image analysis software was used to exclude lung from nonlung structures. Lung attenuation was measured in Hounsfield units (HU) for analysis of whole lung and regional changes in attenuation and lung gas and tissue components. Degree of lung attenuation was classified as follows: hyperinflated or emphysema, -1,000 to -901 HU; well aerated, -900 to -501 HU; poorly aerated, -500 to -101 HU; and nonaerated, > -100 HU. RESULTS Qualitative evidence of an increase in lung attenuation and patchy alveolar patterns in the ventral lung region were more pronounced in foals ≤ 7 days of age than in older foals. Quantitative analysis revealed that mean ± SD lung attenuation was greater in foals ≤ 7 days of age (-442 ± 28 HU) than in foals > 7 days of age (-521 ± 24 HU). Lung aeration and gas volumes were lower than in other regions ventrally and in the mid lung region caudal to the heart. CONCLUSIONS AND CLINICAL RELEVANCE-Identified radiographic patterns and changes in attenuation were most consistent with atelectasis and appeared more severe in foals ≤ 7 days of age than in older neonatal foals. Recognition of these changes may have implications for accurate CT interpretation in sedated neonatal foals with pulmonary disease.

Comparison of radiographic and computed tomographic images of the lungs in healthy neonatal foals

OBJECTIVE To compare CT and radiographic images of the lungs in sedated healthy foals positioned in sternal recumbency and to investigate whether a relationship exists between CT-derived measurements of lung attenuation and Paco2 and Pao2. ANIMALS 6 healthy Standardbred foals < 14 days of age. PROCEDURES Thoracic CT images were acquired followed by radiographic views with each foal sedated and positioned in sternal recumbency. For each foal, both CT and radiographic images were evaluated for severity and extent of changes by lung regions on the basis of a subjective scoring system by 3 investigators. Quantitative analysis of CT images was also performed. Assessments of Pao2 and Paco2 were performed before sedation, following sedation prior to CT, and after CT prior to radiography. RESULTS Interobserver agreement for CT and radiographic image scoring was strong (0.73) and fair (0.65), respectively; intraobserver agreement was near perfect for CT (0.97) and radiographic (0.94) image scoring. Increased CT attenuation and radiographic changes were identified for all foals and were preferentially distributed in the caudoventral portion of the lungs. Radiographic scores were significantly lower than CT image scores. A positive correlation (r = 0.872) between lung attenuation and CT image score was identified. A significant increase in Paco2 was not considered clinically relevant. Significant changes in Pao2 were not observed. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that interpretation of CT images may be less subjective, compared with interpretation of radiographic images. These findings may aid in the evaluation of CT and radiographic images of neonatal foals with respiratory tract disease.