ABSTRACT
This paper describes the application of Independent Component Analysis (ICA) to signals from a pulse oximeter, an instrument that measures arterial blood oxygen content. ICA uses estimates of the second- and higher-order joint statistics of the input signals to separate the signal and interference. For time-derivative pulse oximetry signals, the skew of the arterial pulse component is generally much greater than that of the interference, and this can be used to aid the separation. This paper shows an example of ICA used on pulse oximetry signals and then presents simulations to demonstrate that, for pulse oximetry signals, ICA based on third-order statistics of the derivative is indeed superior to fourth-order ICA.
ABSTRACT
Methods for improving the contrast-to-noise ratio (CNR) of low-contrast lesions in medical ultrasound imaging are described. Differences in the frequency spectra and amplitude distributions of the lesion and its surroundings can be used to increase the CNR of the lesion relative to the background. Automated graylevel mapping is used in combination with a contrast-weighted form of frequency-diversity speckle reduction. In clinical studies, the techniques have yielded mean CNR improvements of 3.2 dB above ordinary frequency-diversity imaging and 5.6 dB over sharper conventional images, with no post-processing graylevel mapping.
