“…Since then, sources of intensity inhomogeneity in MRI have been studied extensively (Alecci et al, 2001;Keiper et al, 1998;Liang & Lauterbur, 2000;Simmons et al, 1994) and can be generally divided into two groups: prospective methods and retrospective methods. According to the classification proposed by U. Vovk (Vovk et al, 2007), we may further classify the prospective methods into those that are based on phantoms, multi-coils, and special sequences. The retrospective methods are further classified into filtering, surface fitting, segmentation-based, and histogram-based, etc.…”