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    • 5. 发明授权
    • Correction algorithm for bone-induced spectral artifacts in computed
tomograph imaging
    • 计算机断层成像中骨诱导光谱伪影的校正算法
    • US6115487A
    • 2000-09-05
    • US4397
    • 1998-01-08
    • Thomas L. TothGuy M. BessonJiang HsiehTin-Su Pan
    • Thomas L. TothGuy M. BessonJiang HsiehTin-Su Pan
    • A61B6/03A61B6/00G01N23/04G06K9/00
    • A61B6/583G01N23/046A61B6/027G01N2223/419Y10S378/901
    • A spectral correction algorithm for correcting dense object-induced spectral artifacts is described. In one embodiment, a calibration object, representative of typical head scanning conditions is scanned and the data reconstructed to provide an image. A water or water-equivalent cylinder of about the same diameter also is scanned and reconstructed, on the same display field of view (DFOV). These two images are designated respectively by BWEQ and WEQ. The ratio of images BWEQ and WEQ is then evaluated, and a region of interest extracted by multiplying the ratio by a function II(r), to obtain a calibration pattern CP. The calibration pattern is then averaged in azimuth to obtain a calibration vector. This calibration vector is fitted with low--order polynomial, and then divided by the fitting polynomial, to take out from the vector the low frequency components that, for instance, would be introduced on an "ideal" scanner. By subtracting 1.0 from the ratio, and multiplying by a CT number scale factor (ctscale) and an apodizing window Aw(r), a calibration error vector CEV is obtained that is representative of the circularly symmetric image error introduced by the non-corrected bone-induced artifact. The corresponding error calibration vector can be expanded into a circularly symmetric image error pattern I[CEV(r)], and subtracted from the calibration image, to provide a substantially artifact free image. The method can be extended to extract and correlate error vectors on an image segment basis such that the resulting error image pattern is not circularly symmetric.
    • 描述了用于校正致密物体感应光谱伪影的光谱校正算法。 在一个实施例中,代表典型头部扫描条件的校准对象被扫描,并且重建数据以提供图像。 在相同的显示视野(DFOV)上也扫描和重构大约相同直径的水或水当量圆柱体。 这两个图像分别由BWEQ和WEQ指定。 然后评估图像BWEQ和WEQ的比率,并且通过将该比率乘以函数II(r)而提取的感兴趣区域以获得校准图案CP。 然后将校准图案在方位平均,以获得校准矢量。 该校准矢量装配有低阶多项式,然后用拟合多项式除以从矢量中取出例如将在“理想”扫描仪上引入的低频分量。 通过从该比值中减去1.0,乘以CT数比例因子(ctscale)和变迹窗口Aw(r),获得代表由未校正骨引入的圆对称图像误差的校准误差向量CEV 诱导的神器。 相应的误差校准矢量可以扩展成圆对称图像误差模式I [CEV(r)],并从校准图像中减去,以提供基本上无伪影的图像。 该方法可以扩展以在图像片段上提取和关联错误矢量,使得所得到的误差图像图案不是圆对称的。