Disturbance elimination in near-infrared spectroscopy through L2-correlated empirical mode decomposition

A non-invasive and accuracy medical measurement method is important in homecare systems. Near-infrared spectroscopy (NIRS) is one of them, and widely used to acquire the biomedical information. Near-infrared light is used to penetrate into the tissue and to indicate the oxygen concentration. To provide accuracy and meaningful NIRS information is the aim of this article. Two major NIRS disturbances are environment optical interference and physical disturbances. To prevent these affection, correlated empirical mode decomposition (cEMD) with L2 norm selector is proposed, called L2-CEMD. Public NIRS data were used and mixed with some biomedical disturbances and white noise. The high similarity intrinsic mode functions associated with the known disturbances were eliminated through the screening process. The spectrum results indicated that the energy of the additional signals can be eliminated. L2-CEMD method can eliminate the disturbances and thus reduce their effects on signal analyses.

I. Introduction

By measurement technology, brain activation monitoring technologies can be divided into optical method and electric method. There are several electric brain activation monitoring technologies, such as electro-encephalography (EEG), functional magnetic resonance imaging (fMRI), and positron emission tomography (PET). Each one has either a high spatial resolution but low temporal resolution or a high temporal resolution but low spatial resolution. Relatively, optical methods such as Near-infrared spectroscopy (NIRS) exhibit both high temporal and spatial resolutions. Other advantages of optical methods and instruments include low cost, safety, portability, and low sensitivity to electrical artifact. In addition, optical methods are less sensitive to the geometrical configuration of individual neurons.