Veterinary Radiology & Ultrasound最新文献

This study aimed to optimize magnetic resonance angiography (MRA) protocols for time-resolved MRA imaging in dogs by using different injection rates and contrast volumes. In this experimental and prospective study, four protocols combining two flow rates (0.2 and 2.0 mL/s) and two contrast volumes (0.2 and 0.4 mL/kg, equivalent to 0.1 and 0.2 mmol/kg gadolinium) were applied in five healthy beagle dogs. Quantitative measurements, including maximum signal intensity, peak enhancement time, diagnostic window, and signal homogeneity, were obtained for the common carotid artery and external jugular vein. Qualitative assessment included arterial visibility persistence, wall margin clarity, and artifact evaluation. Statistical comparisons were performed using the Friedman and Wilcoxon signed-rank tests, and effect size analysis was used to further interpret nonsignificant trends. The low-flow-high-volume protocol (0.2 mL/s, 0.4 mL/kg) yielded the longest diagnostic window and superior vessel visibility with minimal venous contamination, while maintaining comparable maximum signal intensity to higher flow rate protocols. Artifact-related issues such as ringing and intravoxel dephasing were least observed in the low-flow-high-volume protocol. Although high-flow-high-volume protocol showed improved signal homogeneity, it was associated with greater artifact susceptibility. Interobserver agreement ranged from fair to substantial (κ = 0.457-0.681), with greater variability in artifact-related scores. These findings suggest that a slower injection rate with higher contrast volume, as seen in the low-flow-high-volume protocol, provides the best balance of image quality and diagnostic performance, supporting its recommendation as a preferred protocol for small-animal time-resolved MRA.

Nasoesophageal and nasogastric feeding tubes are commonly used in dogs and cats, but inadvertent tracheal placement can cause serious complications. Although radiographs are widely used for confirming tube position, standardized interpretive guidelines are lacking. This study aimed to introduce and validate novel radiographic guidelines for improving tube position identification. Six blinded interpreters (one radiology intern, two emergency and critical care residents, one general practitioner, and two fourth-year veterinary students) with varying clinical experience assessed tube positioning on 256 lateral canine and feline cervical/thoracic radiographs before and after receiving the guidelines. True tube position was determined by clinical history and radiographic assessment by two board-certified radiologists. The proposed guidelines for identifying correctly positioned tubes included (1) incomplete superposition of the tube on the tracheal lumen, (2) dorsal tube position relative to the carina, and (3) relative to the larynx when included. The study included 129 esophageal-positioned (correct) and 127 tracheal-positioned (incorrect) radiographs with nasoesophageal/nasogastric tubes. The implementation of the radiographic guidelines significantly improved the correct identification of tube positioning, increasing from 82.1% pre-guidelines to 95.8% post-guidelines (p < 0.001). Additionally, "uncertain" assessments decreased from 14.1% pre-guidelines to 2.4% post-guidelines (p < 0.001). Before guidelines, interpreters correctly identified tube position in 89.1% of radiographs that included the larynx. However, guideline implementation did not significantly impact the correct interpretation of tube position assessment when the larynx was included. These results validate the clinical utility of a novel radiographic guideline to improve the accuracy and confidence of identification of nasoesophageal/nasogastric tube position in dogs and cats.

Meningeal enhancement on magnetic resonance imaging (MRI) is commonly associated with pathological conditions, including inflammation, neoplasia, or ischemia. However, short and thin segments of contrast enhancement are considered normal in the brain meninges, but studies on spinal meningeal enhancement in dogs are limited. This prospective, exploratory study aimed to determine the presence and characteristics of cervical spinal meningeal enhancement in healthy dogs as well as the impact of acquisition time on enhancement. Cervical spinal MRI was performed from the dens of the axis to the C4-5 intervertebral disc (IVD) in 12 healthy beagles. T2-weighted, T1-weighted, contrast-enhanced T1-weighted (T1CE), immediate fat-saturated T1CE (T1CE_FS), and 15-min delayed T1CE_FS images were acquired. Enhancement patterns were categorized by their distribution, location (dorsal, lateral, or ventral aspect of the meninges), and shape (long segments, short segments, or spots). The enhancement percentage (E%) was calculated to quantitatively evaluate the enhancement. All dogs showed contrast enhancement at the IVD level, not the vertebral body. On immediate imaging, the enhanced regions predominantly appeared as short segments, most commonly at the C2-3, primarily in the dorsal aspect of the meninges. No significant differences were found between the two acquisitions except for the decrease in the E% in C3-4 after a 15-min delay. These results suggest that cervical spinal meningeal enhancement is a normal finding in healthy dogs, primarily appearing as short segments in the dorsal aspect of the meninges at the C2-3 level, with minimal changes between immediate and delayed imaging.

Computed tomography (CT) is a common imaging modality used to evaluate for a pituitary macrotumor in dogs. However, a standard definition of a pituitary macrotumor based on imaging characteristics has not yet been established. The human definition of a pituitary mass that measures >1 cm in diameter has previously been adopted for dogs but fails to account for variability in size, breed, and skull conformation. We hypothesized that normal pituitary gland size and macrotumor size vary by skull morphology. We also hypothesized that canine pituitary macrotumors may be smaller than 1 cm. In this retrospective, case-control analytical study, contrast CT scans from 89 dogs with imaging-diagnosed pituitary macrotumors and 89 dogs with normal pituitary glands were compared. The height, length, width, and volume of the pituitary gland, sella turcica, and brain were measured along with the brain area at the level of the pituitary gland. Of the pituitary macrotumors, 21.3% (19/89) were smaller than 1 cm in height. Data support that a pituitary gland height >0.60 cm or a pituitary volume of 0.17 cm³ may represent a macrotumor in brachycephalic dogs, and a pituitary gland height >0.65 cm or a pituitary volume of 0.31 cm³ may represent a macrotumor in mesocephalic dogs; small numbers of dolichocephalic dogs precluded determination of cutoffs. These data provide a foundation for future studies to classify pituitary macrotumors on CT imaging according to skull conformation, thereby aiding in the detection, treatment, and response assessment of dogs with pituitary neoplasms.

The intrathoracic lymph nodes (LN) of clinical interest in dogs are the sternal (STLN), cranial mediastinal (CrMLN), and tracheobronchial (TBLN) groups. Although computed tomography (CT) depicts and measures these nodes well, thoracic screening commonly relies on three-view radiographs. We hypothesized that enlargement of these nodes would not be consistently identified radiographically, even by experienced observers. In this retrospective, multicenter study (2012-2023), three board-certified radiologists independently graded three-view thoracic radiographs from 74 dogs. Each LN group was scored on a 5-point scale (1, cannot assess; 2, normal; 3, mild; 4, moderate; 5, marked). Corresponding per-group CT volumes (STLN, CrMLN, and combined TBLN) were calculated using the ellipsoid formula, and analyses were performed at the LN-group level. Inter-rater agreement was estimated with Gwet's AC1, and associations between radiographic grades and CT volumes were evaluated with Spearman's rank correlation. Observer agreement on radiographs was almost perfect (AC1: STLN 0.88, CrMLN 0.93, and TBLN 0.95). Correlations between radiographic grades and CT volumes were weak or nonsignificant; only one observer for TBLN showed a weak positive correlation (ρ = 0.27, p = 0.02). No CT-derived volume threshold yielded a unanimous radiographic classification of enlargement (grade ≥ 3) across observers. Radiographs frequently failed to detect enlarged nodes and occasionally overcalled normal-sized nodes. These findings indicate poor alignment between radiographic grading and CT-measured volume for intrathoracic lymphadenomegaly, despite high interobserver agreement. When accurate intrathoracic LN assessment is expected to influence clinical decision-making, CT should be considered.

Computed tomography (CT) is commonly used to evaluate external and middle ear disease and for surgical planning in dogs. However, there is limited literature regarding CT characteristics of benign and malignant canine external ear canal neoplasms. This retrospective, multicenter, secondary analysis, cross-sectional study compared the CT features of benign and malignant tumors in 39 dogs with 41 external ear canal masses by consensus of two veterinary radiologists. Recorded parameters were the presence of focal or multifocal tissue enlargement (mass/masses), lesion shape, location of the center of the mass, attenuation characteristics, features of contrast enhancement, involvement of otic structures, calvarial and brain changes, changes of nearby structures, and lymphadenopathy. The most common neoplasms in this study were ceruminous gland adenocarcinoma (13/41) and ceruminous gland adenoma (11/41). Although malignant tumors more commonly exhibited heterogeneous attenuation, heterogeneous contrast enhancement, aggressive periosteal proliferation, and compressed/displaced and/or invaded regional structures, benign tumors also exhibited aggressive characteristics, such as adjacent osteolysis. Given the degree of overlap of CT findings between benign and malignant external ear canal neoplasms, features may only aid in prioritizing differential diagnoses, and biopsy is required for definitive diagnosis.

Like with conventional myelography, circumferential attenuation of the subarachnoid space on magnetic resonance (MR) myelography may aid in the diagnosis of an acute compressive disc extrusion. Hydrated nucleus pulposus extrusion (HNPE) is characterized by the presence of extradural material above the intervertebral disc space that is isointense to CSF and may mask the attenuation of the ventral subarachnoid space. Concurrent failure of the dorsal subarachnoid space to attenuate may result in failure to recognize HNPE or underestimate its severity. Magnetic resonance imaging (MRI) studies of dogs diagnosed with cervical HNPE were reviewed for the presence or absence of CSF signal from the dorsal subarachnoid space. Available computed tomography (CT) studies from the same dogs were reviewed with the goal of identifying an anatomic cause of a maintained dorsal subarachnoid space. The dorsal subarachnoid space remained visible in 25/35 (71.4%) and was attenuated in 10/35 (28.6%) of MRI studies reviewed. On the basis of the CT study review, the location of the maintained signal corresponds to the location of the normal gap between adjacent vertebral arches (interarcuate space). This retrospective study describes a potential pitfall in the MR myelographic diagnosis of cervical HNPEs due to a maintained CSF signal in the dorsal subarachnoid space attributed to the displacement of the subarachnoid space into the interarcuate space between adjacent vertebrae.

Structural changes in the thalamus and basal nuclei (BN) have been documented in magnetic resonance imaging (MRI) studies of human epilepsy. Studies that specifically investigate whether equivalent structural changes exist in dogs with idiopathic epilepsy (IE) are limited. This retrospective study evaluated the morphology of the caudate nucleus and thalamus in dogs with IE (n = 40) compared to a control group (n = 38) using standard MRI studies. Measurements of the interthalamic adhesion (ITA) thickness and area, thalamic area and volume, and caudate nucleus area and volume were made to compare the size and symmetry of these structures between groups. Dogs with IE had a significantly larger ITA thickness (p < 0.0001) and area (p < 0.0001), smaller thalamic area (p < 0.0001) and volume (p < 0.0001), and smaller caudate nucleus volume (p = 0.0126) than controls. There were no significant differences in caudate nucleus area (p = 0.171) and asymmetry index for both thalamus (p = 0.104) and caudate nucleus (p = 0.853) between groups. Our findings indicate that a smaller thalamic and caudate nucleus size is associated with canine IE. However, further research is necessary to determine whether these findings can be generalized to other BN and to investigate the involvement of thalamocortical or BN-thalamocortical circuits in the pathophysiology of IE.