改进的同态滤波方法校正磁共振图像中偏差场

为提高磁共振图像的均匀性并减小不同生理组织的灰度交叠，针对磁共振图像中存在的光滑、缓慢变化的乘性偏差场，提出了改进的同态滤波校正方法。该方法将同态滤波和B样条平滑相结合，首先采用高斯同态滤波器对污染图像滤波，得到初步估计的偏差场；然后从中选出感兴趣区域用B样条拟合出平滑的偏差场。该方法能快速、有效地校正偏差场，同时去除了滤波后产生的边缘伪迹。在有偏差场的人头模型图像和计算机仿真的MRI图像的校正中，均取得了满意的结果。

An Improved Homomorphic Filtering Method for Inhomogeneity Correction of Magnetic Resonance Images

In order to improve the uniformity and diminish the distributions overlapping of different tissue intensities in the magnetic resonance (MR) images, an improved homomorphic filtering correcting method was proposed, based on the smooth, multiplicative and slowly varying features of the bias field. This method combines I he homomorphic filtering and B spline smoothing. Firstly, a coarse bias estimation is got by Gaussian homomorphic filtering on the corrupted image. Secondly, B spline smoothing is performed on some interested area of the coarse estimation. Finally, a refined bias estimation is got by B spline extrapolation. This method can quickly remove the bias field from the corrupted MR images. Simultaneously, the spline smoothing step can eliminate the boundary artifacts caused by low-pass filtering. The simulations on both head phantom image and simulated MRI image show good results.