In general, magnetic resonance imaging (MRI) is a technique of applying a gradient magnetic field and an RF (radio frequency) wave to a subject in a static magnetic field, and producing an image based on magnetic resonance signals emitted as an echo from protons in a region to be examined. Magnetic resonance imaging (MRI) systems typically include a super conducting magnet capable of producing a strong, homogenous magnetic field around a patient or portion of the patient; a radio frequency (RF) transmitter and receiver system, including transmitter and receiver coils, also surrounding or impinging upon a portion of the patient; a gradient coil system also surrounding a portion of the patient; and a computer processing/imaging system, receiving the signals from the receiver coil and processing the signals into interpretable data, such as visual images. Magnetic resonance imaging systems utilizing a superconductive electromagnetic device include tunnel-type and open-type systems when categorized according to the contours of vacuum containers for incorporating superconductive coils and the like. For the magnets of the MRI apparatus, permanent magnets, normal conducting magnets and superconducting magnets have been put into practical use. The superconducting magnets, which can achieve higher magnetostatic field strength, are finding wider applciations than permanent magnets and normal conducting magnets. Magnetic resonance imaging (MRI) utilizes hydrogen nuclear spins of the water molecules in the human body or other tissue, which are polarized by a strong, uniform, static magnetic field generated by a magnet. The magnetically polarized nuclear spins generate magnetic moments in the human body. The magnetic moments point in the direction of the main magnetic field in a steady state, and produce no useful information if they are not disturbed by any excitation. MRI involves the interrogation of the nuclear magnetic moments of a subject placed in a strong magnetic field with radio frequency (RF) magnetic fields. Typically, a high frequency magnetic field is applied to the subject placed in homogeneous static magnetic field to obtain a tomographic image of the region from nuclear magnetic resonance signals induced thereby. Radio frequency energy is applied to this region of the patient by a transmitter and antenna. The RF energy excites atomic nuclei within the patient's tissues. The excited nuclei spin at a rate dependent upon the magnetic field. As they spin, they emit faint RF signals, referred to herein as magnetic resonance signals. In order to select a specific region, a gradient magnetic field is applied together with the high frequency magnetic field and further, in order to provide correct positional information for the echo signals measured, it is necessary to correctly control the application time and intensity of the gradient magnetic field. By applying small magnetic field gradients so that the magnitude of the magnetic field varies with location within the patient's body, the magnetic resonance phenomenon can be limited to only a particular region or "slice" of the patient's body, so that all of the magnetic resonance signals come from that slice. Moreover, by applying additional magnetic field gradients, the frequency and phase of the magnetic resonance signals from different locations within the slice can be made to vary in a predictable manner depending upon the position within the slice. A magnetic resonance imaging system is equipped with a radio frequency oscillator. This oscillator is used to adjust the carrier frequency of a radio-frequency excitation pulse for selective excitation, depending on a slice-directional position of a specified section (single slice) to be imaged of an object, in cases where imaging is carried out while the object is moved.

Magnetic resonance imaging (MRI) detects the faint nuclear magnetic resonance (NMR) signals given off by protons in the presence of a strong magnetic field after excitation of the protons with a radio frequency signal. The NMR signals are detected using loop antennas termed coils. Magnetic resonance imaging (MRI) collects data in the Fourier domain, typically referred to as k-space, from the magnetic signals of protons processing in a magnetic field. The spin frequency, also referred to as the resonance frequency, is a function of a material's gyromagnetic ratio and the strength of the magnetic field. Magnetic resonance imaging (MRI) can be used to generate chemical shift specific images because protons in different chemical species may have different resonance frequencies. The chemical shift artifact (CSA) presents a significant barrier to the quantitative MR image analysis of small features, in which the amount of shift is comparable to the dimension of the object. The CSA appears as a "shadowing" effect in the read direction of MR images. In magnetic resonance image scanning (MRI scanning), images of a subject, usually a patient's body, are produced through the interaction of a magnetic field applied to the patient's body and the magnetic moment of protons. Each proton behaves as small bar magnet, and the strength of the bar magnet is referred to as the "magnetic moment" of the proton. The protons are the nuclei of hydrogen atoms. The hydrogen is chemically bonded in compounds of the patient's tissue. Magnetic resonance imaging (MRI) provides excellent soft tissue contrast with arbitrary scan-volume orientations, thus making MRI an extremely useful medical imaging modality. Magnetic resonance imaging offers a powerful, non-intrusive 3D imaging technique for various medical, engineering and scientific studies. This is achieved by spatially coding the precessing frequencies or phases of nuclear magnetic moments of a sample under study under a bias magnetic field and using radio frequency (RF) coils to excite and detect emitted signals with a certain sequence. A three-dimensional (3D) image is then reconstructed after signal processing with a processor. The MRI systems can be divided into two general categories mainly in terms of a magnetic field application method. One is a horizontal magnetic field apparatus in which an imaging volume is placed in an internal space of a group of coils arranged coaxially in multiple layers, and the other is a vertical magnetic field apparatus (open type) in which an imaging volume is sandwiched between opposing coil groups. Because of its openness the vertical magnetic field apparatus reduces a psychological burden on a patient and significantly improves an accessibility to the patient by an inspector.