摘要:
After spins in a subject being examined have been selectively excited, the application of gradient magnetic fields is interrupted to produce an FID signal. The intensity of the primary magnetic field is determined based on the central frequency of the Fourier spectrum of the FID signal, i.e., the Larmor frequency. The primary magnetic field is controlled or the observed data is corrected, according to the measured value of the primary magnetic field intensity.
摘要:
An NMR data processing method for use with an NMR tomograph, wherein signals, located in a period before and after an NMR signal to be sampled and containing substantially none of the NMR signal component, are measured as offset data for each view, so that even the offset slightly fluctuating in the view can be corrected for the NMR signal, on the basis of that data.
摘要:
A method of simultaneously correcting distortion in density due to uneven sensitivity of receiving coils, and location dependent phase distortion inherent in the system, wherein a phantom is scanned to determine echo signals, which echo signals are subjected to 2-dimensional inverse Fourier transformation, to obtain an image (Cij) and stored as it is in the form of a complex number, then the object to be examined is measured by similar operation to obtain an image (Oij) and wherein the image (Oij) is divided by computation with image (Cij) as follows .vertline.Sij.vertline.=.vertline.Oij.vertline./.vertline.Cij.vertline., by which equation computation is made to correct for density distortion, and wherein the angle of deviation is set as follows arg [Sij]=arg[Oij]-arg[Cij].ident.0, by which equation computation is made to correct for phase distortion. An image of the object is thus obtained which is corrected for density distortion and for phase distortion, by taking the real number part of the image Sij which is the determined image of the object.
摘要:
When a power switch is turned OFF, the execution of steady process is stopped, and backup data is written into a flash memory. If the power switch is turned ON during the writing of the backup data, the backup data writing execution is allowed to last for a predetermined time T1 after an instant when the power switch is turned ON, and if the writing of the backup data is not terminated at the time when the predetermined time T1 has elapsed, the writing of the backup data is interrupted so that the steady process is started for being executed.
摘要:
An open architecture magnetic resonance imaging permanent magnet assembly with moveable magnets and adjustable field inclination with automatic magnetic field homogeneity shimming to enhance imaging and positioning of the magnetic field about the portion of the patient to be imaged while enabling interventional physician access.
摘要:
With a view toward implementing an RF coil easy to uniformize the strength of a magnetic field, the RF coil is provided with a first current path group of wires including a plurality of linear current passes placed in parallel with one another, a second current pass group of wires placed so as to have the relations in mirror image with respect to the first current pass group, and a third current pass group of wires in which all the linear electrical passes are series-connected so as to be identical in current direction through both groups of the first and second current pass groups while bypassing the first and second current pass groups.
摘要:
There is disclosed a magnetic resonance imaging method which permits a scan to be made in a short time by collecting only the data that is used to reconstruct an image. The method is initiated by defining a circular region whose center lies at the point in a two-dimensional Fourier plane at which the spatial frequency is zero. The Fourier plane corresponds to a region containing an image to be reconstructed. The spin echo signals emanating from a region inside the circular region are observed by an ordinary Fourier method, said region having a length greater than a predetermined length as measured in the direction in which data obtained by the observation is read out. The spin echo signals emanating from the remaining region inside the circular region are observed while shortening the time for which a reading gradient magnetic field is applied whenever an excitation is effected and, at the same time, effecting an additional phase shift encoding.
摘要:
An improved selective excitation method applicable to NMR imaging, regardless of the NMR signal generation method used, wherein a non-scanned subject area is excited using an RF signal, then the excited area is spoiled with a gradient magnetic field to create an area that receives no other excitation RF signal for a set period, and then NMR signals are collected from the unspoiled area using a conventional method.
摘要:
An NMR imaging method and apparatus according to the present invention which enables collection of data to be effected within a minimum scanning time which can be desired for each object of inspection is arranged such that projection data concerning the object is collected from a plurality of directions, a direction in which the number of samples in the warp direction is minimized is obtained on the basis of the collected projection data, and then the scanning coordinate system is rotated in accordance with the obtained direction to collect data on the basis of the Fourier transformation method.
摘要:
In order to generate an RF magnetic field efficiently, an RF coil is used comprising electric paths 612 carrying electric current for generating the RF magnetic field within a space containing a subject, and an annular electric path 614 located farther from the subject than the electric paths 612 from the subject, for linking respective ends of the electric paths 612.