-
公开(公告)号：US5027071A
公开(公告)日：1991-06-25
申请号：US489124
申请日：1990-03-05
IPC分类号： A61B5/055 , G01R33/32 , G01R33/36 , G01R33/385 , G01R33/387 , G01R33/54 , G01R33/565 , G06T1/00
CPC分类号： G01R33/385 , G01R33/56518 , G01R33/3607 , G01R33/3852
摘要： A method of reducing slice profile degradation due to gradient signal amplitude ripple, has steps of: sensing the gradient signal ripple amplitude; normalizing the sensed ripple signal amplitude responsive to the gradient amplitude commanded; and modulating the RF signal amplitude with the adjusted-amplitude ripple signal, to cause the RF and gradient magnetic fields to have an effective vector pointing substantially in the same direction, during the slice-selection interval, as would the effective field vector formed with a gradient field devoid of ripple. Apparatus for reducing the slice profile degradation modulates the RF signal with the ripple envelope obtained from the output of the gradient signal amplifier, by a signal controlled by the gradient amplifier input.
-
32.发明授权
公开(公告)号：US4961054A
公开(公告)日：1990-10-02
申请号：US376074
申请日：1989-07-06
申请人： John N. Park , Otward M. Mueller , Peter B. Roemer
发明人： John N. Park , Otward M. Mueller , Peter B. Roemer
IPC分类号： G01R33/20 , A61B5/055 , G01R33/38 , G01R33/385 , G01R33/48 , H03K17/567
CPC分类号： G01R33/3852 , H03K17/567
摘要： A gradient current speed-up circuit, for use in a higher-speed NMR imaging system with a gradient power amplifier and an associated gradient coil, has an energy-storage element, with an inductance typically between 5 and 20 times the inductance of the associated gradient coil. A plurality of semiconductor switching elements receive the current output of the energy-storage element; and the associated gradient coil is connected between selected ones of these semiconductors devices. The semiconductor devices are turned on and off in selected patterns, to cause the energy-storage element current to be suddenly applied to and removed from flow through the associated gradient coil.
-
搜索结果
32 条记录 (耗时 0.015 秒)
