An Illustrated Scoping Review of the Magnetic Resonance Imaging Characteristics of Canine and Feline Brain Tumors

Simple Summary Magnetic resonance imaging is an invaluable tool for the diagnosis of brain diseases in veterinary medicine. In this review, we provide a comprehensive summary of the magnetic resonance imaging appearances of and diagnostic approach to brain tumors affecting dogs and cats. Characteristic imaging features often allow for accurate prediction of commonly encountered types of brain tumors in clinical practice, such as meningiomas, gliomas, and pituitary tumors. However, a limitation of magnetic resonance imaging remains that some types of brain tumors, as well as other causes of brain disease, display similar imaging features, which can lead to diagnostic uncertainty and errors. There are also several uncommon to rare variants of brain tumors for which published magnetic resonance imaging descriptions are extremely limited or non-existent, especially in cats. The recent development and clinical usage of quantitative imaging and artificial intelligence techniques show promise for improving the ability of magnetic resonance imaging to correctly diagnose brain tumors and discriminate different tumor types.Abstract Magnetic resonance imaging (MRI) is used pervasively in veterinary practice for the antemortem diagnosis of intracranial tumors. Here, we provide an illustrated summary of the published MRI features of primary and secondary intracranial tumors of dogs and cats, following PRISMA scoping review guidelines. The PubMed and Web of Science databases were searched for relevant records, and input from stakeholders was solicited to select data for extraction. Sixty-seven studies of moderate to low-level evidence quality describing the MRI features of pathologically confirmed canine and feline brain tumors met inclusion criteria. Considerable variability in data inclusion and reporting, as well as low case numbers, prohibited comparative data analyses. Available data support a holistic MRI approach incorporating lesion number, location within the brain, shape, intrinsic signal appearances on multiparametric sequences, patterns of contrast enhancement, and associated secondary changes in the brain to prioritize differential imaging diagnoses, and often allows for accurate presumptive diagnosis of common intracranial tumors. Quantitative MRI techniques show promise for improving discrimination of neoplastic from non-neoplastic brain lesions, as well as differentiating brain tumor types and grades, but sample size limitations will likely remain a significant practical obstacle to the design of robustly powered radiomic studies. For many brain tumor variants, particularly in cats, there remains a need for standardized studies that correlate clinicopathologic and neuroimaging data.