REVIEW AND EVALUATION OF MRI NONUNIFORMITY CORRECTIONS FOR BRAIN-TUMOR RESPONSE MEASUREMENTS

Current MRI nonuniformity correction techniques are reviewed and inves tigated. Many approaches are used to remedy this artifact, but it is n ot clear which method is the most appropriate in a given situation, as the applications have been with different MRI coils and different cli nical applications. In this work four widely used nonuniformity correc tion techniques are investigated in order to assess the effect on tumo r response measurements (change in tumor volume over time): a phantom correction method, an image smoothing technique, homomorphic filtering , and surface fitting approach. Six brain tumor cases with baseline an d follow-up MRIs after treatment with varying degrees of difficulty of segmentation were analyzed without and with each of the nonuniformity corrections. Different methods give significantly different correctio n images, indicating that rf nonuniformity correction is not yet well understood. No improvement in tumor segmentation or in tumor growth/sh rinkage assessment was achieved using any of the evaluated corrections . (C) 1998 American Association of Physicists in Medicine.