Method for tracking a catheter probe during a fluoroscopic procedure

Claim 1

A method for tracking a catheter or probe, said catheter being characterized by at least one of the following characteristics: A. relatively thin, less than 2 mm, wire-like shape; B. begins in periphery of an image; C. has smooth edges; D. does not bend much; and E. X-ray dense as compared to the surround; using an X-ray fluoroscopic apparatus for passing X-rays from an X-ray source means through a subject body to an X-ray detector means, including image processing means including image intensifier means, coupled thereto for providing said image and including a radiation reduction device comprising: a controllable filter member means being responsive to a control signal, and including a filter member being semi-transparent to X-rays and having at least one aperture formed therethrough, such that X-rays passing through said at least one aperture remain unattenuated and strike said subject body in a common region; wherein the X-rays passing through said filter member are attenuated and strike said subject body in a pattern that surrounds, and is adjacent to, said common region; control means coupled to said X-ray source means, to said image processing means, and to said controllable filter member means; said method comprising the following steps: 1. morphologically processing the image to enhance an image of said catheter; opening an input image, INPUT, with a flat, structuring element; subtracting said opened image from INPUT, to given ENHANCED; 2. threshold ENHANCED giving binary image, BINARY whereby said binary image contains silhouettes including a silhouette of said catheter; 3. analyzing regions or blobs, in BINARY to find said image of said catheter using properties of said catheter including said catheter being thin, relatively rigid, and X-ray dense; for each blob, make at least two of the following calculations: apply a thinning algorithm to obtain a medial axis; compute length of said medial axis, MEDIAL -- LENG; compute AREA and PERIMETER. DISTANCE -- TO -- PERIPHERY -- i (i=1,2), the distance of two endpoints of the medial axis to a periphery of said image intensifier; AREA -- TO -- PERIMETER, a ratio of the area to the perimeter; PERIMETER -- TO -- MEDIAL -- LENG, a ratio of the perimeter to the length of the medial axis; BENDING, an average local curvature of said medial axis; compute a mean intensity within the blob from ENHANCED; identify potential catheters by the following properties: a. One of the DISTANCE -- TO -- PERIPHERY measure should be close to zero; b. AREA -- TO -- PERIMETER should be close to half the width of said catheter; c. PERIMETER -- TO -- MEDIAL -- LENG should be close to 2.0; g. BENDING should be small; e. mean intensity should be within a predetermined value. for each potential blob, compute a score which is a function of measures identified above; select identification of said catheter as a blob from the set of potential catheters having the highest score; 4. finding the end of said catheter selected: the location of one endpoint of the medial axis farther away from a predetermined outer boundary is said end of said catheter selected; and 5. Ending.

Claim 2

A method for tracking a catheter or probe, said catheter being characterized by at least one of the following characteristics: A. relatively thin, less than 2 mm, wire-like shape; B. begins in periphery of an image; C. has smooth edges; D. does not bend much; and E. X-ray dense as compared to the surround; using an X-ray fluoroscopic apparatus for passing X-rays from an X-ray source means through a subject body to an X-ray detector means, including image processing means including image intensifier means, coupled thereto for providing said image and including a radiation reduction device comprising: a controllable filter member means being responsive to a control signal, and including a filter member being semi-transparent to X-rays and having at least one aperture formed therethrough, such that X-rays passing through said at least one aperture remain unattenuated and strike said subject body in a common region; wherein the X-rays passing through said filter member are attenuated and strike said subject body in a pattern that surrounds, and is adjacent to, said common region; control means coupled to said X-ray source means, to said image processing means, and to said controllable filter member means; said method comprising the following steps: 1. morphologically processing the image to enhance an image of said catheter; opening an input image, INPUT, with a flat, structuring element; subtracting said opened image from INPUT, to given ENHANCED; 2. threshold ENHANCED giving binary image, BINARY whereby said binary image contains silhouettes including a silhouette of said catheter; 3. analyzing regions or blobs, in BINARY to find said image of said catheter using properties of said catheter including said catheter being thin, relatively rigid, and X-ray dense; for each blob, make at least two of the following calculations: apply a thinning algorithm to obtain a medial axis; compute length of said medial axis, MEDIAL -- LENG; compute AREA and PERIMETER. DISTANCE -- TO -- PERIPHERY -- i (i=1,2), the distance of two endpoints of the medial axis to a periphery of said image intensifier; AREA -- TO -- PERIMETER, a ratio of the area to the perimeter; PERIMETER -- TO -- MEDIAL -- LENG, a ratio of the perimeter to the length of the medial axis; BENDING, an average local curvature of said medial axis; compute a mean intensity within the blob from ENHANCED; identify potential catheters by the following properties: a. One of the DISTANCE -- TO -- PERIPHERY measure should be close to zero; b. AREA -- TO -- PERIMETER should be close to half the width of said catheter; c. PERIMETER -- TO -- MEDIAL -- LENG should be close to 2.0; g. BENDING should be small; e. mean intensity should be within a predetermined value. for each potential blob, compute a score which is a function of measures identified above; select identification of said catheter as a blob from the set of potential catheters having the highest score; 4. finding the end of said catheter selected: the location of one endpoint of the medial axis farther away from a predetermined outer boundary is said end of said catheter selected; and 5. Ending.