Abstract: A computed tomography (CT) system utilizes a ring suppression filter for suppressing ring artifacts in a CT image. The system generates projections at a plurality of projection angles, and each projection includes one measurement of a plurality of projection data signals. The ring suppression filter includes a high pass filter, a histogram generator, and a combiner. The high pass filter generates a measurement of an error signal corresponding to each of the measurements of one of the projection data signals, and each of the error signal measurements is representative of the high frequency components in a portion of one of the projections. The histogram generator generates a histogram signal representative of a relationship between the measurements of the error signal and the measurements of the projection data signal. The combiner combines the measurements of the error signal and the histogram signal to generate a plurality of measurements of a ring corrected signal.

Abstract: A computed tomography (CT) system utilizes a ring suppression filter for suppressing ring artifacts in a CT image. The system generates projections at a plurality of projection angles, and each projection includes one measurement of a plurality of projection data signals. The ring suppression filter includes a high pass filter, a histogram generator, and a combiner. The high pass filter generates a measurement of an error signal corresponding to each of the measurements of one of the projection data signals, and each of the error signal measurements is representative of the high frequency components in a portion of one of the projections. The histogram generator generates a histogram signal representative of a relationship between the measurements of the error signal and the measurements of the projection data signal. The combiner combines the measurements of the error signal and the histogram signal to generate a plurality of measurements of a ring corrected signal.

Abstract: The disclosed streak suppression filter is for use with a Computed Tomography (CT) system. The CT system generates a plurality of projection data signals each of which is representative of the density of a portion of an object. The streak suppression filter includes a spatial filter for receiving the projection data signals and for generating therefrom a low frequency signal and a high frequency signal. The streak suppression filter further includes a non-linear filter for generating a filtered signal from the high frequency signal. The streak suppression filter further includes a device for combining the low frequency and filtered signals to generate a streak corrected signal. The streak suppression filter may form the low frequency signal by low pass filtering the raw density signals and may form the high frequency signal by subtracting the low frequency signal from the corresponding raw density signal.

Abstract: The disclosed motion artifact filter generates motion corrected signals from projection data signals to compensate for motion artifacts in CT images. Each measurement of the projection data signals is representative of the density of all the mass occupying a volume between an X-ray source and a detector at a particular projection angle. The motion artifact filter includes a high pass filter for generating high frequency signals representative of patient movement. Each measurement of the high frequency signals is generated by combining groups of measurements of the projection data signals corresponding to volumes that are proximal to each other. Each measurement of the motion corrected signals is generated by subtracting a portion of a measurement of a high frequency signal from its associated measurement of a projection data signal. The portions increase as the projection angle approaches a starting angle and the portions decrease as the projection angle approaches an intermediate angle.