摘要:
An electromagnet having a current detecting device for detecting the current flowing through an electromagnet exciting coil, the output of which is utilized to control the power supplied to the coil to stabilize the current flowing through the coil; the electromagnet further including a separate power supply to supply current to the current detecting device which supplies current to the current detecting device when the electromagnet is not on working.
摘要:
An MRI flow imaging method and apparatus wherein a width of a relevant region in a direction is set, in which fluid in a subject body flows, and a first 90.degree. radio frequency pulse is applied thereto to excite selectively a relevant region; a gradient magnetic field is applied thereto in a direction, in which it is desired to project the fluid, after an application of a first 90.degree. radio frequency pulse so that a magnetization signal in a projection direction is zero, a second radio frequency pulse is applied to a relevant region to excite the relevant region selectively, after new fluid has poured in the relevant region, an echo signal is measured by applying an encoding gradient magnetic field and a reading out gradient magnetic field in a form of a flow sensitive pulse capable of detecting an echo signal from the fluid, and an echo signal is processed to obtain a two-dimensional image of the fluid.
摘要:
A three-dimensional NMR imaging method using phase encoding field gradients along two direction is disclosed. The measurement of an NMR signal is repeated in such a manner that among all combinations of a plurality of magnitudes of gradient prepared for the phase encoding field gradient along one of the two directions and a plurality of magnitudes of gradient prepared for the phase encoding field gradient along the other direction, combinations in which the magnitude of the phase encoding field gradient along the one direction is not larger than a predetermined value, are selected preceding the remaining combinations. A first image reconstruction processing is performed for data trains acquired on the basis of the precedently selected combinations, thereby obtaining a crude image. The crude image is displayed to confirm whether the location of measurement is proper or not. After the confirmation, the remaining combinations are successively selected to continue the measurement of the NMR signal and a second image reconstruction processing is performed for all of data trains acquired, thereby obtaining a detailed image.
摘要:
Disclosed is an NMR gated imaging apparatus in which an ultrasonic pulse signal is repeatedly transmitted toward the heart of a human body from an ultrasonic transducer to detect the position of the heart on the basis of the time of detection of a peak of an echo signal, and excitation and measurement of an NMR signal are executed only when a peak detector generates a detection output signal having a level included in a predetermined range. Thus, the NMR signal is repeatedly measured according to a programmable phase encoding amount at a limited phase of gated imaging.
摘要:
A field gradient generator in an NMR imaging apparatus comprises three sets of field gradient generating coils for respectively generating field gradients in three orthogonal directions in a space to be observed. Each set of coils includes a plurality of unit coils through which individual currents respectively flow. There are prepared a plurality of unit drivers which are for exclusive uses of the respective unit coils or are connected arbitrarily to each unit coil. Thereby, the lowering of an allowable operating voltage is implemented by use of a parallel operation of the unit drivers.
摘要:
In an imaging method called spin warp method in which a measuring sequence inclusive of nuclear spin excitation, application of phase-encoding gradient field, and measurement of NMR signals under the application of read-out gradient field, is repeated while changing the phase-encoding amount, and a data train thus obtained is subjected to the two-dimensional inverse Fourier transformation to reconstruct a magnetization distribution image of an object, wherein an NMR imaging method is characterized in that measurement of NMR signals is repeated a plural number of times for a particular phase-encoding amount only among many phase-encoding amounts, a plurality of NMR signals thus obtained are added up together and are averaged, and the data obtained by the addition and averaging is subjected to the two-dimensional inverse Fourier transformation.
摘要:
A method of measuring a static magnetic field distribution in a nuclear magnetic resonance (NMR) inspection system which comprises magnetic field generator for producing a static magnetic field, inclination or gradient magnetic fields and a high-frequency magnetic field, a signal detector for sensing nuclear magnetic resonance signals from an inspection sample, a computer for processing output signals from the signal detector and an output device for providing a computational result of the computer, wherein a time interval t.sub.1 from the center of a 90.degree.-pulse high-frequency magnetic field to the center of a 180.degree.-pulse high-frequency magnetic field is made different by a time difference t.sub.0 from a time interval t.sub.2 from the center of the 180.degree.-pulse high-frequency magnetic field to a peak of a spin echo, so that static magnetic field distribution is calculated based on the computer output which corresponds to the difference of the two time intervals.
摘要:
There is provided a probe to detect a nuclear magnetic resonance signal in which each of a plurality of arms forming a current path of an Alderman-Grant type coil is divided into two conductor plates, the two conductor plates are connected by an inductor, and a resonance frequency is reduced by increasing the inductance of the current path.
摘要:
A quadrature probe for nuclear magnetic resonance includes two sets of coils which are combined with an angle of 90.degree. therebetween. Four pieces of outer conductors and two pieces of ring-shaped inner conductors are capacitively coupled to each other through an insulator or an air gap. In the outer conductor(s) in at least one of a set of outer conductors disposed at positions symmetrical with respect to each other so as to form a first coil and a set of outer conductors disposed at positions symmetrical with respect to each other so as to form a second coil, a conductor member(s) for adjustment is attached in parallel to the arm portion(s) in that outer conductor(s) of that set. Alternatively, the arm portion(s) itself in that set is slidably attached to the wing portions in that set.
摘要:
An NMR imaging method is disclosed in which an object is measured in accordance with a pulse sequence capable of expressing a difference between two of a plurality of chemical shifts by a phase difference in a signal, that is, a pulse sequence 90.degree.-.tau..sub.a -180.degree.-.tau..sub.b -spin echo (where .tau..sub.a .noteq..tau..sub.b) to obtain spin distribution data, a histogram with respect to the phase of the spin distribution data is formed to regard a phase corresponding to that one of a plurality of peaks of the histogram which exists at one end of the histogram, as a position-independent offset phase which is contained in the spin distribution data and is peculiar to an NMR imaging apparatus, and the spin distribution data is corrected using the offset value thus obtained, to extract spin density distribution data for each of the chemical shifts from the corrected spin distribution data.
摘要翻译:公开了一种NMR成像方法,其中根据能够通过信号的相位差表示多个化学位移之间的差异的脉冲序列来测量物体,即脉冲序列90°-τa -180°-τb-自旋回波(其中τa NOTEQUAL tau b)为了获得自旋分布数据,形成相对于自旋分布数据的相位的直方图,以考虑与多个峰中的那一个相对应的相位 存在于直方图的一端的直方图作为自旋分布数据中包含的并且是NMR成像设备特有的与位置无关的偏移相位,并且使用由此获得的偏移值来校正自旋分布数据, 从校正的自旋分布数据中提取每个化学位移的自旋密度分布数据。