The fast automatic algorithm for correction of MR bias field.

Purpose: To develop a method for efficient automatic correction of slow-varying nonuniformity in MR images.

Materials And Methods: The original MR image is represented by a piecewise constant function, and the bias (nonuniformity) field of an MR image is modeled as multiplicative and slow varying, which permits to approximate it with a low-order polynomial basis in a "log-domain." The basis coefficients are determined by comparing partial derivatives of the modeled bias field with the original image.

Results: We tested the resulting algorithm named derivative surface fitting (dsf) on simulated images and phantom and real data. A single iteration was sufficient in most cases to produce a significant improvement to the MR image's visual quality. dsf does not require prior knowledge of intensity distribution and was successfully used on brain and chest images. Due to its design, dsf can be applied to images of any modality that can be approximated as piecewise constant with a multiplicative bias field.

Conclusion: The resulting algorithm appears to be an efficient method for fast correction of slow varying nonuniformity in MR images.