Chronological low field magnetic resonance appearance of canine spinal epidural hemorrhage model

The magnetic resonance (MR) features of spinal epidural hemorrhage depending with the passage of time have a meaning in veterinary medicine. The aim of this study is to propose the characteristic MR image of spinal epidural hemorrhage using a lower field permanent magnet scanner in dogs. A total of 8 clinically normal beagle dogs, weighing about 9 kg, were allocated. After a baseline MR examination, spinal epidural hemorrhage was created. MR scanning was executed on days 1, 2, 3, 4, 5, 10, 15, 20, 25, and 30 using 0.25 Tesla low field MR. Transverse MR images were attained for image examination. T2W, T1W, fluid-attenuated inversion recovery (FLAIR), short tau inversion recovery (STIR), and T2*-GRE sequences were used. Images were compared subjectively for signal transition assessment. Spinal epidural hemorrhage models were produced positively in 8 dogs at the T12 to L2 region. Initially, the spinal cord and epidural lesions were hyper-intense on T2W and T1W images. On T2W, FLAIR and STIR images, the spinal cord lesion was steadily hyperintense. No significant and consistent hypointense signal indicating hemorrhage was seen on T2*-GRE images. This study result suggests that relatively consistent hyperinstensity on T2 and FLAIR is observed for 30 days, meanwhile T2*-GRE imaging is less useful in hemorrhage detection.

Diagnostic imaging features of normal anal sacs in dogs and cats

This study was conducted to provide normal reference features for canine and feline anal sacs using ultrasound, low-field magnetic resonance imaging (MRI) and radiograph contrast as diagnostic imaging tools. A total of ten clinically normal beagle dogs and eight clinically normally cats were included. General radiography with contrast, ultrasonography and low-field MRI scans were performed. The visualization of anal sacs, which are located at distinct sites in dogs and cats, is possible with a contrast study on radiography. Most surfaces of the anal sacs tissue, occasionally appearing as a hyperechoic thin line, were surrounded by the hypoechoic external sphincter muscle on ultrasonography. The normal anal sac contents of dogs and cats had variable echogenicity. Signals of anal sac contents on low-field MRI varied in cats and dogs, and contrast medium using T1-weighted images enhanced the anal sac walls more obviously than that on ultrasonography. In conclusion, this study provides the normal features of anal sacs from dogs and cats on diagnostic imaging. Further studies including anal sac evaluation are expected to investigate disease conditions.

Time-dependent low-field MRI characteristics of canine blood: an in vitro study

This study was conducted to assess time-sensitive magnetic resonance (MR) changes in canine blood using low-field MR. Arterial and venous blood samples were collected from eight healthy beagle dogs. Samples were placed in 5-mL tubes and imaged within 3 hours of collection at 1 day intervals from day 1 to day 30. The following sequences were used: T1-weighted (T1W), T2-weighted (T2W), fluid-attenuated inversion recovery (FLAIR), short tau inversion recovery (STIR), and T2-star gradient-echo (T2*-GRE). Visual comparison of the images revealed that four relatively homogenous blood clots and twelve heterogeneous blood clots developed. The margination of the clot and plasma changed significantly on day 2 and day 13. On day 2, heterogeneous blood clots were differentiated into 2 to 3 signal layers in the T2W, T1W, and especially the STIR images. Hypointense signal layers were also detected in the blood clots in STIR images, which have T2 hypo, FLAIR hypo, and T1 hyper intense signals. In all images, these signal layers remained relatively unchanged until day 13. Overall, the results suggest that hematomas are complex on low-field MRI. Accordingly, it may not be feasible to accurately characterize hemorrhages and predict clot age based on low-field MRI.

Virtual otoscopy for evaluating the inner ear with a fluid-filled tympanic cavity in dogs

The feasibility of virtual otoscopy (VO) imaging was evaluated in five dogs with experimentally induced otitis media, two control dogs, and two canine patients with otitis media. VO images of the tympanic cavity and ossicles were generated with commercially available software using raw computed tomography (CT) data. Eight out of 10 ears inoculated with pathogen exhibited obvious clinical signs associated with otitis externa. CT images revealed soft tissue density material occupying the tympanic bulla compatible with otitis media in three dogs with experimentally induced otitis media and two patients. No remarkable features were observed on the radiographs. Four different VO views (ear canal, tympanic bulla, eustachian tube, and ossicular chain) were created. Promontory, cochlea window, tympanic, and septum bulla as well as ossicles were easily and clearly distinguished except for the incus and stapes of the clinical patients. VO images were not more suitable than images created with conventional CT for accurately diagnosing otitis media in this study. However, it appears that VO could be more feasible for assessing the complex structure of the inner ear in dogs with fluid-filled tympanic cavities since fluid accumulation within the tympanic bulla did not affect the evaluation of bony tissue in the middle ear on VO images.