What is the appropriate means of bias field in image processing?
Bias field is magnetic based inhomogenity in results of MRI, which comes from magnetic settings, patient position etc.
This term has no standard definition in terms of image processing.
Essentialy this is smooth, low frequency, gradiented signal, which covers valuable data.
In terms of MRI this is just artifact and very often when somebody says that image will be preprocessed or will get rid of artifacts, bias field is included (naming it simply - noise from equipement).