Fast shading correction for cone-beam CT via partitioned tissue classification.

Fast shading correction for cone-beam CT via partitioned tissue classification. Phys Med Biol. 2019 Feb 05;: Authors: Shi L, Wang AS, Wei J, Zhu L Abstract The quantitative use of cone beam computed tomography (CBCT) in radiation therapy is limited by severe shading artifacts, even with system embedded correction. We recently proposed effective shading correction methods, using planning CT (pCT) as prior information to estimate low-frequency errors in either the projection domain or the image domain. In this work, we further improve the clinical practicality of our previous methods by removing the requirement of prior pCT images. 
 Clinical CBCT images are typically composed of a limited number of tissue types. By utilizing the low-frequency characteristic of shading distribution, we first generate a "shading-free" template image by enforcing uniformity on CBCT voxels of the same tissue type via a technique named partitioned tissue classification. Only a small subset of voxels on the template image is used to generate sparse samples of shading errors. Local filtration, a Fourier transform based algorithm, is employed to efficiently process the sparse errors to compute a full-field distribution of shading errors for CBCT correction. We evaluate the method performance on an anthropomorphic pelvis phantom and 6 pelvis patients.
 The proposed method improves the image quality of CBCT on both phantom and patients to a leve...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research