Evaluation of Presumptive Normal Feline Tonsils with Low-Field Magnetic Resonance Imaging: A Preliminary Retrospective Study

SIMPLE SUMMARY: Palatine tonsils are lymphoid organs within the tonsillar fossa. Their location provides them a role against antigens entering the body during feeding and breathing. MRI is considered the technique of choice in depicting soft tissue, and it can show concurrent bone involvement. In human medicine, MRI is used in the investigation of tonsillar diseases. In veterinary medicine, a recent study on healthy dogs has described the MRI appearance of presumed normal canine palatine tonsils. Due to the similarities between animals and humans, the authors aimed to evaluate the feasibility of low-field MRI to detect tonsils in cats and to describe features of presumed normal palatine tonsils, assessing the interoperator reproducibility of the findings in a population of adult cats. MRI is a potentially useful imaging modality for the assessment of palatine tonsils in cats; also, with a low-field MRI, their normal appearance has been described for the first time in this study. The authors recommend the evaluation of tonsils in the transverse plane and consider the most accurate estimation of the short axis. This study could be a baseline for the evaluation of MRI in the assessment of feline tonsils with high-field MRI. ABSTRACT: Palatine tonsils are lymphoid organs, whose anatomic localization gives them a role against antigens entering the body during feeding and breathing. In human medicine, MRI is used to investigate tonsillar diseases. In veterinary medicine, a recent study on healthy dogs described the MRI appearance of canine palatine tonsils, with no available reports about feline ones. Due to the similarities between animals and humans, and based on the study on canine tonsils, the authors aimed to evaluate the feasibility of low-field MRI to detect and describe presumed normal features of feline palatine tonsils, assessing the finding’s reproducibility. Low-field MRI of the heads of 14 cats was reviewed, and qualitative findings (visualization, shape, margins, signal intensity, and pattern) and size of each tonsil were recorded. Each observer recorded 71% of the expected tonsils. Most of them were classified as oval, ill-defined, and hyperintense structures with both homogeneous and heterogeneous signal patterns; the overall agreement was considered good. Low-field MRI is potentially a useful imaging modality to visualize palatine tonsils in cats, and their normal appearance has been described for the first time. The authors recommend the evaluation of tonsils in the transverse plane and consider the most accurate estimation of the short axis.