MAGNETIC RESONANCE IMAGING: BIOPHYSICAL PRINCIPLES AND DIAGNOSTIC SIGNIFICANCE

Аннотация

Magnetic resonance imaging (MRI) is a non-invasive diagnostic imaging technique based on the physical properties of atomic nuclei exposed to a strong magnetic field and radiofrequency electromagnetic radiation. The method primarily exploits the magnetic properties of hydrogen nuclei, which are abundant in biological tissues because of their high water and lipid content. When placed within a static magnetic field, hydrogen nuclei undergo alignment and precession, while radiofrequency pulses alter their magnetic state. The subsequent relaxation of these nuclei generates measurable signals that are spatially encoded and mathematically reconstructed into cross-sectional images. The contrast observed in MRI depends mainly on tissue-specific relaxation characteristics, particularly longitudinal (T1) and transverse (T2) relaxation, as well as proton density and the parameters of the applied pulse sequence. Unlike X-ray-based imaging techniques, conventional MRI does not use ionizing radiation, which contributes to its extensive application in neurological, musculoskeletal, cardiovascular, abdominal, and oncological imaging. Recent developments, including low-field MRI, ultrahigh-field systems, quantitative MRI, magnetic resonance fingerprinting, and artificial intelligence-assisted image processing, have expanded the diagnostic potential of the technique. Understanding the biophysical mechanisms underlying MRI is essential for interpreting image formation, optimizing diagnostic quality, and maintaining patient safety. This article reviews the fundamental physical and biological principles of MRI and discusses their significance in modern medical diagnosis.