Intra-pixel multispectral processing of magnetic resonance brain images for tissue characterization

Magnetic resonance (MR) image analysis is generally performed by spatial domainbased image processing, referred to as inter-pixel image processing, which takes advantage of spatial correlation among sample pixels. Unfortunately, in many areas, several tissue substances are usually present and mixed in a single image pixel in which such an inter-pixel processing either fails or is ineffective. To resolve this dilemma, this paper develops an unconventional approach, called intra-pixel processing, which considers MR images as multispectral images where a multispectral MR image pixel is actually a pixel vector, of which each component is captured by a particular image pulse sequence used for MR image acquisition. Since the commonly used receiver operating characteristic (ROC) curves cannot directly deal with the issues arising in intra-pixel processing, a 3D ROC analysis is developed by including a parameter t as the third dimension that represents abundance fractions thresholded by τ.