Multiple-measurement noise-reducing system
AssigneeThe Board of Trustees of the Leland Standford Junior University
InventorAlbert Macovski
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Abstract
In a multiple-measurement system, a weighted sum of the measurements is used to provide a selective image. An additional weighted sum is used to provide an increased signal-to-noise ratio of some desired parameter of the image. The high frequency components of the increased signal-to-noise ratio image are combined with the low frequency components of the selective image to provide a selective image with improved signal-to-noise ratio. The combining operation can utilize the ratios of the derivatives in each signal to provide the correct amount of high frequency signal at each transition.
Claims41
For use in an imaging system, a method for reducing the noise of a first processed image of an object representing a desired parameter derived from a plurality of measurements the steps of:
- processing said plurality measurements to provide a second processed image having greater signal-to-noise ratio than said first processed image;
- filtering said first processed image to reduce its noise;
- filtering said second processed image with a filter complementary to the filter used on said first processed image;
- and
- combining said filtered first processed image and said filtered second processed image to provide a reduced noise version of said first processed image.
A method for providing an improved processed image from a plurality of x-ray measurements comprising the steps of:
- deriving the low frequency portion of the processed image from functions of a first weighted sum of the measurements at different x-ray energies;
- and
- deriving the remainder of the frequency components from functions of a second weighted sum of the measurements having an improved signal-to-noise ratio.
Apparatus for providing a reduced noise version of a an image of an object formed by a plurality of measurements comprising:
- means for combining the plurality of measurements to provide an image signal;
- means for low pass filtering the image signal to provide a first processed image signal;
- means for combining the plurality of measurements to provide a lower noise processed image signal;
- means for high pass filtering the lower noise processed image to provide a second processed image signal;
- and
- means for combining said first and second processed image signals whereby a reduced noise version of the image signal is obtained having substantially the fidelity of the original image signal.
Apparatus for providing a reduced noise version of a processed image of an object formed by a plurality of measurements comprising:
- means for combining the plurality of measurements to provide said processed image;
- means for median filtering the processed image to provide a first processed image;
- means for combining the plurality of measurements to provide a lower noise processed image;
- means for subtracting a median filtered lower noise processed image from the lower noise processed image to provide a second processed image;
- and
- means for combining the first and second processed images whereby a reduced noise version of the processed image is obtained having substantially the fidelity of the original processed image.
Dependencies are inferred from the claim text.