1. An image filtering method to filter an image in a parallel manner using a multi-core Computed Tomography (CT) imaging processor, the image filtering method comprising the following steps: determining, by said multi-core CT imaging processor, a plurality of computing directions for filtering processing according to a number of dimensions of an image and a predetermined neighborhood range of said filtering processing; computing in parallel by each of a plurality of processing threads of said multi-core CT imaging processor, respective directions filtering for each of the plurality of processing threads of said multi-core CT imaging processor, wherein the following processing is performed by said multi-core CT imaging processor according to each of the determined computing directions for one row of pixels in the image, by taking each pixel in the row as an object pixel, performing by each said processing thread predetermined filtering computing between an object pixel and respective neighborhood pixels of the object pixel in the computing direction; and storing the filtering computing results as filtering results of the object pixels and the respective neighborhood pixels in a cumulative manner, wherein the neighborhood pixels are pixels located within the neighborhood range of the object pixel; and obtaining, by said multi-core CT imaging processor, an image filtering result by accumulating filtering results of each said determined computing direction for each said respective parallel directions filtering computing step according to each pixel of the image so as to obtain the image filtering result of the image.