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    • 61. 发明授权
    • Gradient coil apparatus for magnetic resonance imaging
    • 磁共振成像用梯度线圈装置
    • US06680612B1
    • 2004-01-20
    • US10065417
    • 2002-10-16
    • Graeme Colin McKinnonQin Liu
    • Graeme Colin McKinnonQin Liu
    • G01V300
    • G01R33/385
    • A gradient coil assembly for use with an MR imaging system comprising: a main gradient coil disposed about an imaging axis to produce a gradient field; a corrector coil disposed about an imaging axis and positioned with a return portion substantially overlapping a return portion of main gradient coil. The main gradient coil and said corrector coil cooperate to provide a first field of view, the main gradient coil operates to provide a second field of view. A method of reducing power deposition in a gradient coil assembly comprising: determining a first current density corresponding to a first field-of-view for an effective gradient coil; computing a second current density corresponding to a second field of view, by reducing current from the first current density without changing a sign of said the associated therewith; determining a geometry for a main gradient coil; and ascertaining a geometry for a corrector coil.
    • 一种用于MR成像系统的梯度线圈组件,包括:围绕成像轴设置的梯度线圈,以产生梯度场; 校正器线圈,围绕成像轴设置并且具有大致与主梯度线圈的返回部分重叠的返回部分定位。 主梯度线圈和所述校正线圈协作提供第一视场,主梯度线圈操作以提供第二视场。 一种降低梯度线圈组件中的功率沉积的方法,包括:确定对应于有效梯度线圈的第一视场的第一电流密度; 通过从所述第一电流密度减少电流而不改变与其相关联的符号来计算对应于第二视场的第二电流密度; 确定主梯度线圈的几何形状; 并确定校正线圈的几何形状。
    • 65. 发明授权
    • Image compression method and apparatus which satisfies a predefined bit
budget
    • 满足预定义位预算的图像压缩方法和装置
    • US6118903A
    • 2000-09-12
    • US116563
    • 1998-07-15
    • Qin Liu
    • Qin Liu
    • G06T9/00H04N7/26H04N7/30G06K9/36
    • H04N19/126H04N19/60H04N19/124
    • A DCT based lossy compression method for compressing a digitized image composed of a matrix of image samples to provide a compressed image which satisfies a predefined bit budget. The digitized image is first sub-divided into blocks (e.g. of size 8.times.8 pixels). A discrete cosine transform (DCT) comprising a set of DCT coefficients is then derived for each block. A quantization table is selected from a set of quantization tables and, using the selected table, the coefficients of each DCT are quantized. A zero-value index, corresponding to the average number of zero value quantized DCT coefficients per DCT, is determined. A predicted zero-value index is calculated using said predefined bit budget and a quantization table selected from said set of tables using the determined index and the predicted index. Using that selected table, the unquantized coefficients of the DCTs are re-quantized and the requantized coefficients compressed using run-length encoding and Huffman encoding.
    • 一种基于DCT的有损压缩方法,用于压缩由图像样本矩阵组成的数字化图像,以提供满足预定比特率预算的压缩图像。 数字化图像首先被细分成块(例如大小为8×8像素)。 然后对于每个块导出包括一组DCT系数的离散余弦变换(DCT)。 从一组量化表中选择量化表,并且使用所选择的表来量化每个DCT的系数。 确定对应于每DCT的零值量化DCT系数的平均数的零值索引。 使用所确定的索引和预测索引,使用所述预定义位预算和从所述表组中选择的量化表计算预测零值索引。 使用该选择的表,对DCT的未量化系数进行重新量化,并且使用游程长度编码和霍夫曼编码来压缩重新量化的系数。