Video Upload Options

Magnetic resonance imaging (MRI) is a noninvasive imaging modality that forms spatially resolved maps of the internal structure and chemical composition of an object from the nuclear magnetic resonance (NMR) signals of atomic nuclei, most commonly the protons of water and fat, within a strong static magnetic field ^[1]. In MRI, the object is placed in a homogeneous static field that establishes a net longitudinal magnetization, while radiofrequency pulses tip this magnetization into the transverse plane, where precessing spins emit an induced detectable signal ^[2]. Spatial localization is achieved by superimposing time-varying magnetic field gradients that encode spin precession frequency and phase according to position, so that the acquired raw signal in k-space can be reconstructed by Fourier transformation into a two- or three-dimensional image ^[2]. Image contrast arises from differences in proton density and in the longitudinal (T1) and transverse (T2) relaxation times of tissue, which reflect the local biochemical and physical environment ^[3]. MRI is distinguished from other tomographic techniques by its reliance on resonant interactions of spins with magnetic fields rather than on transmission of ionizing radiation, and by the dependence of contrast on tissue relaxation properties ^[1].