Magnetic Resonance Imaging Physics in Brain Tumor Imaging: A Primer for Neurosurgeons.

Magnetic resonance imaging (MRI) is central to the management of brain tumors and is deeply integrated into the neurosurgical workflow. From initial diagnosis through surgical planning and postoperative assessment, MRI guides nearly every stage of care. Yet the images that inform these decisions are shaped by underlying physical principles that may not be fully appreciated in clinical practice. This review provides a comprehensive and accessible overview of MRI physics as it applies to brain tumor imaging, with a focus on clinical relevance for neurosurgeons. We begin with core concepts such as spin behavior, relaxation mechanisms, and image formation and explain how these principles translate into the contrast mechanisms used in common and advanced imaging sequences. Key modalities, including T1-weighted, T2-weighted, fluid-attenuated inversion recovery, diffusion, perfusion, and functional imaging, are discussed in terms of what they reveal, how they operate, and the limitations that must be considered. We examine how these tools support surgical decision-making, including functional mapping, tractography, and intraoperative navigation, while also addressing common pitfalls such as pseudoprogression and imaging artifacts. The review concludes by highlighting emerging technologies such as artificial intelligence-based segmentation, ultra-high-field MRI, quantitative imaging, and radiomics, all of which may shape the future of neurosurgical imaging. For the modern neurosurgeon, fluency in MRI physics is not merely academic; it is essential for accurate interpretation, effective collaboration with radiology, and safer, more personalized surgical care.