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Investigation of abnormal magnetic resonance imaging signal in the tonsillar region of dogs

Kang, Kevin (2021) Investigation of abnormal magnetic resonance imaging signal in the tonsillar region of dogs. Other thesis, Murdoch University.

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Abstract

At The Animal Hospital at Murdoch University (TAHMU), an abnormal signal was observed in the tonsillar region of two dogs on brain MRI. Both dogs did not present with or demonstrate clinical signs of oropharyngeal disease. The abnormal signal in the two cases was interpreted as possible foreign bodies by veterinary teleradiologists. However, despite the abnormal signal in both cases demonstrating similar MRI features, the interpretation of the nature of the foreign body was different. In one of the two cases, the veterinary teleradiologist suspected that the abnormal signal in the tonsillar region was a metallic foreign body and likely a component of the endotracheal (ET) tube.

Objectives:
(1) Describe and characterise the appearance of the tonsillar region of dogs on brain MRI examinations.
(2) Describe and characterise any abnormal signal detected in the tonsillar region of dogs on brain MRI examinations at TAHMU.
(3) Investigate if any detected abnormality is associated with the ET tube used in anaesthetised dogs.

Material and Methods:
Retrospectively, all canine brain MRI examinations performed from 2017 to 2021 at TAHMU were reviewed. Prospectively, 20 dogs undergoing brain MRI for clinical investigation of neurological disease were included. An oral examination was performed at intubation, and details regarding the ET tube were recorded (ET tube diameter and manufacturer). During the review of the MRI images, the tonsillar region was evaluated for the presence of an abnormal signal (termed tonsillar abnormality; TA). If TA was detected, its location, size, shape, margin and signal intensity in pre-and post-contrast sequences were evaluated.

Results:
Foci of signal void in one or both tonsillar regions, consistent with gas, were detected in 160/170 retrospective studies. In 3/170 studies, TA was observed in the right tonsillar region at the level of the temporomandibular joint. All three TA exhibited a peripheral hyperintense rim and a less intense centre that was hypointense to the medial pterygoid muscle on T1-weighted sequences; and mildly hyperintense to the medial pterygoid muscle on T2-weighted and T2 FLAIR sequences. All three TA displayed signal void and excessive magnetic susceptibility artefact on T2* gradient echo sequences. No gas was detected in the tonsillar region in the remaining 7/170 studies. Gas was detected in one or both tonsillar regions in 19/20 prospective studies, but 0/20 demonstrated a TA.

Conclusion:
TA was infrequently detected in our study population and appeared unrelated to the ET tube. TA may be due to a larger volume of gas trapped in the tonsillar region or represent an atypical appearance of gas trapped in the tonsillar region.

Item Type: Thesis (Other)
Murdoch Affiliation(s): Veterinary Medicine
Notes: Accelerated Research Masters with Training
Supervisor(s): Hosgood, Giselle, Stander, Nerissa and Richardson, Jennifer
URI: http://researchrepository.murdoch.edu.au/id/eprint/64530
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