Method and apparatus for creating a color blood flow image based upon ultrasonic echo signals received by an intravascular ultrasound imaging probe

A method for assigning an image signal state, corresponding to a display characteristic, to a designated image point within a field of view, the image signal state being one of at least two potential signal states, said method including the steps of:

• rendering a current display characteristic state for the designated image point, the rendering step including at least the step of comparing a current value associated with the designated image point to a first threshold value;
• summing image point values corresponding to the display characteristic states for a set of image points proximate to the designated image point for a current image frame and for a set of image frames generated in a period of time proximate to the current it image frame, to obtain a time and space averaged value for the display characteristic state of the designated image point;
• comparing the time and space averaged value to at least a second threshold value to render a time and space averaged display characteristic state for the designated image point;
• and
• calculating a display image signal for the designated image point based at least partially upon the time and space averaged display characteristic state for the designated image point.

A flow image processor for generating an image of a field of view within a patient based upon image data having both motion frequency and motion power components wherein motion frequency is represented in the form of designated colors and motion power is represented in the form of brightness levels, the processor comprising:

• means for generating instantaneous motion power data corresponding to the imaged field of view;
• means for generating instantaneous motion frequency data corresponding to the imaged field of view;
• an adjustable first feedback persistence factor establishing a first persistence period that is relatively long in comparison to a cardiac cycle for the patient;
• an adjustable second feedback persistence factor establishing a second persistence period that is relatively short in comparison to a cardiac cycle for the patient:
• a motion power filter for computing a time averaged motion power from a feedback averaged motion power, the instantaneous motion power, and at least the adjustable first feedback persistence factor;
• a motion frequency filter for computing a time averaged motion frequency from a feedback averaged motion frequency, the instantaneous motion frequency, and at least the adjustable second feedback persistence factor;
• a color image data generator for combining the time averaged motion power and time averaged motion frequency to define a color image;
• and
• means for generating an image for display on a visual display device in accordance with the color image.

An image processor space-time filter for assigning an image signal state, corresponding to a display characteristic, to a designated image point within a field of view, the image signal state being one of at least two potential signal states, said processor comprising:

• means for rendering a current display characteristic state for the designated image point, the means for rendering comprising a first comparator for comparing a current value associated with the designated image point to a first threshold value;
• means for summing image point values corresponding to the display characteristic states for a set of image points proximate to the designated image point for a current image frame and for a set of image frames generated in a period of time proximate to the current image frame, to obtain a time and space averaged value for the display characteristic state of the designated image point;
• means for comparing the time and space averaged value to at least a second threshold value to render a time and space averaged display characteristic state for the designated image point;
• and
• means for calculating a display image signal for the designated image point based at least partially upon the time and space averaged display characteristic state for the designated image point.