Optimal injection rate and catheter size for brain perfusion computed tomography using non-ionic contrast medium in clinically normal Beagles.

OBJECTIVE: To evaluate the effects of contrast medium injection rates and intravenous injection catheter sizes on the time-density curve (TDC) of brain perfusion computed tomography (PCT) images in clinically normal Beagles and provide a reference range for the perfusion parameters for clinical application of PCT in veterinary medicine. ANIMALS: 5 healthy, sexually intact male Beagles. PROCEDURES: All dogs underwent general anesthesia for PCT. Contrast medium (350 mg I/kg) was injected at 3 different injection rates (2, 3, and 4 mL/second) and with 2 sizes of an intravenous catheter (20-gauge and 24-gauge). The rostral cerebral artery and dorsal sagittal sinus were selected as the regions of interest of the TDC. Initiation time of arterial inflow (ta), venous outflow (tv), peak time of arterial enhancement (Tap), and the peak time of venous enhancement (Tvp), were measured, and the difference between Tap and tv (Tap-tv) and between Tap and ta (Tap-ta) was calculated. RESULTS: Both Tap-tv and Tap-ta were significantly (P < .05) shorter at the rate of 3 mL/second than at 2 mL/second with the 24-gauge catheter. However, there was no significant difference according to catheter sizes. Particularly, a 4 mL/second injection rate using a 24-gauge catheter mostly resulted in contrast medium leakage and catheter rupture. CLINICAL RELEVANCE: CONTRAST MEDIUM INJECTION: At a rate of 3 mL/second and with a 24-gauge catheter ensures optimal image acquisition and stable contrast medium injection in brain PCT for small dogs. PCT may be useful for diagnosing cerebrovascular events and hemodynamic changes in small dogs.

Feasibility of ultrasonographic hepatic parenchymal attenuation imaging in healthy Beagles.

OBJECTIVE: To investigate the clinical feasibility of attenuation imaging of the hepatic parenchyma in healthy dogs, identify technical factors that influence measured attenuation coefficients, and determine intraobserver repeatability of measurements. ANIMALS: 10 healthy Beagles. PROCEDURES: Attenuation coefficients were calculated for various measurement sites (left vs central division of the liver), scanning planes (transverse vs sagittal plane), scanning depths (10 to 20 mm vs 20 to 30 mm), scanning approaches (intercostal vs subcostal approach), and breathing conditions (free breathing vs breath holding at end expiration). Intraoperator intraday and interday reliability was assessed by computing intraclass correlation coefficients. RESULTS: Attenuation coefficients were not influenced significantly by scanning plane (P = .120 to 1.000), measurement site (P = .292 to .848), or breathing condition (P = .166). However, coefficients were significantly (P < .01) less with deeper scanning depths and significantly (P < .05) more for the subcostal approach than the intercostal approach. The intraday and interday intraclass correlation coefficients showed good repeatability (0.799 and 0.771, respectively), regardless of the scanning plane and measurement site. Scanning the central division of the liver with the right intercostal approach at a depth of 10 to 20 mm from the liver capsule yielded good reliability. CLINICAL RELEVANCE: Attenuation imaging was a feasible technique for evaluating the hepatic parenchyma in healthy dogs with good repeatability. Measured attenuation coefficients were not affected by the scanning plane, measurement site, or breathing condition.

Comparison of shear-wave velocities obtained with shear-wave elastography of various peripheral lymph nodes in healthy Beagles.

OBJECTIVE: To compare shear-wave velocities (SWVs) with shear-wave elastography of various peripheral lymph nodes (LNs). ANIMALS: 11 healthy Beagles. PROCEDURES: For each dog, bilateral mandibular, medial retropharyngeal, superficial cervical, axillary, superficial inguinal, and popliteal LNs were evaluated with shear-wave elastography in sagittal and transverse scanning planes. Depth of each lymph node was recorded, and intra- and interobserver reliability was determined. RESULTS: SWVs for all LNs were significantly higher in the sagittal scanning plane, compared with those in the transverse scanning plane. The SWV of the most superficial LN, the mandibular LN, was significantly higher, compared with that for the other LNs, except for the medial retropharyngeal LN. The SWV of the deepest LN, the medial retropharyngeal LN, was as high as that for the mandibular LN. Intra- and interobserver reliability was excellent. CONCLUSIONS AND CLINICAL RELEVANCE: SWVs for normal peripheral LNs of Beagles may serve as a reference to compare with those for other breeds and diseased LNs. Scanning plane, LN depth, and interfering tissues between the LN and the transducer may affect SWV. Shear-wave elastography may not be operator dependent.