Angioscopic system and method for dimensional measurement including measurement of the distance from angioscopic ends to designated planes

Claims

What is claimed is:

1. A system for angioscopic dimensional analysis comprising:

an optical fiber angioscope having a tip for insertion into the interior of a vessel;

a video camera connected to said angioscope;

a monitor to display images of the interior of a vessel from the tip of the angioscope; and

a computer connected to process data from said video camera, said computer having storage means with stored coefficients for conversion of pixels into dimensional units for feature planes at any distance within an operational range of said tip; and

wherein said computer includes input means to receive data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image and processing means to quantify the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units and by taking into account an actual distance, within said operational range, between said tip and the dimensional feature.

2. The system of claim 1 further comprising a guidewire for guiding the angioscope.

3. A system for angioscopic dimensional analysis comprising:

an optical fiber angioscope having a tip;

a video camera connected to said angioscope;

a monitor to display images from the angioscope; and

a computer connected to process data from said video camera, said computer having storage means with stored coefficients for conversion of pixels into dimensional units for feature planes at different distances from said tip; and

wherein said computer includes input means to receive data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image and processing means to quantify the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units; and further comprising a guidewire for guiding the angioscope; and wherein said guidewire has indicia marked thereon and separated by known distances for viewing by way of the angioscope, and wherein said input means to receive is operable to receive data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image with the tip positioned at a plurality of distances from a feature plane; and said processing means is operable to determine the distance from said tip to the feature plane based on changes in the data corresponding to moving the position of the tip an unknown amount, quantify this unknown amount of movement from changes in the image of the guidewire by use of at least one appropriate coefficient to convert from pixels to dimensional units, and quantify the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units; and said guidewire is operable to stabilize the angioscope and/or orient the angioscope such that the method of angioscopy is improved.

4. A system for angioscopic dimensional analysis comprising:

an optical fiber angioscope having a tip;

a video camera connected to said angioscope;

a monitor to display images from the angioscope; and

a computer connected to process data from said video camera, said computer having storage means with stored coefficients for conversion of pixels into dimensional units for feature planes at different distances from said tip; and

wherein said computer includes input means to receive data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image and processing means to quantify the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units; and

wherein said input means is operable to receive data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image with the tip positioned at a plurality of distances from a feature plane, and said processing means is operable to determine the distance from said tip to the feature plane based on changes in the data corresponding to moving the position of the tip an amount, and quantify the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units.

5. The system of claim 4 wherein said processing means is operable to determine the distance from said tip to the feature plane by converting said unknown dimensional feature from pixels into dimensional units Al when the feature plane is at a first unknown distance from said tip based upon a first hypothesized distance from the feature plane to said tip, converting said unknown dimensional feature from pixels into dimensional units A2 when the feature plane is at a second unknown distance from said tip based upon a second hypothesized distance from the feature plane to said tip, said second unknown distance being a known offset from said first unknown distance, and trying different values for said first and second hypothesized distances to yield different values for A1 and A2 by repetitive conversions until A1 and A2 are determined to be sufficiently close that& the hypothesized distances are accurate, and wherein the dimensional feature is quantified from A1 and/or A2.

6. The system of claim 5, wherein said processing means is operable to convert said unknown dimensional feature from pixels into dimensional units A3 when the feature plane is at a third unknown distance from said tip based upon a third hypothesized distance from the feature plane to the tip, said third unknown distance being a known offset from said first unknown distance and/or a known offset from said second unknown distance, and to try different values for said first, second, and third hypothesized distances to yield different values for A1, A2, and A3 by repetitive conversions until A1, A2, and A3 are determined to be sufficiently close that the hypothesized distances are accurate, and wherein the dimensional feature is quantified from A1, A2, and/or A3.

7. The system of claim 6 wherein the processing means is operable to select accurate distances by determining the hypothesized distances which provide the minimal differences in values for A1, A2, and A3.

8. A method of measuring angioscopic dimensional features using an angioscopic dimensional analysis system having:

an angioscope having a tip and two image-guiding fiber optic bundles spaced apart for providing a stereoscopic image by combining two images, one from each of said fiber optic bundles;

a video camera connected to said angioscope;

a monitor to display images from the angioscope; and

a computer connected to process data from said video camera, said computer having stored coefficients for conversion of pixels into dimensional units for feature planes at different distances from said tip;

the steps comprising:

having the computer receive data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image, the dimensional feature being at an unknown distance within an operational range from said tip;

determining the distance from said tip to the dimensional feature by use of difference in images supplied by the two fiber optic bundles; and

quantifying the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units.

9. A method of measuring angioscopic dimensional features using an angioscopic dimensional analysis system having:

an angioscopic having a tip;

a video camera connected to said angioscope;

a monitor to display images from the angioscope; and

a computer connected to process data from said video camera, said computer having stored coefficients for conversion of pixels into dimensional units for feature planes at different distances from said tip;

the steps comprising:

having the computer receive data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image; and

quantifying the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units, and

further comprising the step of determining the distance from the tip to the feature plane.

10. The method of claim 9 wherein the distance from the tip to the feature plane is determined by viewing indicia marked upon a guidewire extending beyond the tip.

11. A method of measuring angioscopic dimensional features using an angioscopic dimensional analysis system having:

an angioscope having a tip;

a video camera connected to said angioscope;

a motor to display images from the angioscope; and

a computer connected to process data from said video camera, said computer having stored coefficients for conversion of pixels into dimensional units for feature planes at different distances from said tip;

the steps comprising:

having the computer receive data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image; and

quantifying the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units, and

wherein the computer receives data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscope image with the tip positioned at a plurality of distances from a feature plane and further comprising the step of determining the distance from said tip to the feature plane based on changes in the data corresponding to moving the position of the tip an amount.

12. The method of claim 11 further comprising the steps of: converting said unknown dimensional feature from pixels into dimensional units A1 when the feature plane is at a first unknown distance from said tip based upon a first hypothesized distance from the feature plane to said tip, converting said unknown dimensional feature from pixels into dimensional units A2 when the feature plane is at a second unknown distance from said tip based upon a second hypothesized distance from the feature plane to said tip, said second unknown distance being a known offset from said first unknown distance, and

trying different values for said first and second hypothesized distances to yield different values for A1 and A2 by repetitive conversions until A1 and A2 are determined to be sufficiently close that the hypothesized distances are accurate, and wherein the dimensional feature is quantified from A1 and/or A2.

13. The method of claim 11 further comprising the steps of:

converting said unknown dimensional feature from pixels into dimensional units A1 when the feature plane is at a first unknown distance from said tip based upon a first hypothesized distance from the feature plane to said tip, converting said unknown dimensional feature from pixels into dimensional units A2 when the feature plane is at a second unknown distance from said tip based upon a second hypothesized distance from the feature plane to said tip, said second unknown distance being a known offset from said first unknown distance, converting said unknown dimensional feature from pixels into dimensional units A3 when the feature plane is at a third unknown distance from said tip based upon a third hypothesized distance from the feature plane to the tip, said third unknown distance being a known offset from said first unknown distance and/or a known offset from said second unknown distance, and trying different values for said first, second, and third hypothesized distances to yield different values for A1, A2, and A3 by repetitive conversions until A1, A2, and A3 are determined to be sufficiently close that the hypothesized distances are accurate, and wherein the dimensional feature is quantified from A1, A2, and/or A3.

14. The method of claim 13 further comprising having the computer select accurate distances by determining the hypothesized distances which provide the minimal difference in values for A1, A2, and A3.

15. A method for use with an angioscopic dimensional analysis system having:

an angioscope having a tip;

a video camera connected to said angioscope;

a monitor to display images from the angioscope; and

a computer connected to process data from said video camera;

the steps comprising calibrating the system by:

placing at least one known pattern at a series of known distances from the tip of the angioscope such that the video camera generates a corresponding series of images composed of pixels;

measuring the number of pixels in a dimensional feature of the pattern having known dimensions for each image; having the computer calculate at least one coefficient for each known distance, each coefficient useful for conversion of pixels to dimensional units; and storing each of the coefficients.

16. The method of claim 15 wherein said placing step includes the placing of several known patterns at the series of known distances.

17. The method of claim 16 wherein each of said images is a circle.

18. The method of claim 17 wherein a plurality of coefficients are calculated and the calculation of the coefficients includes curve fitting to determine the relationship between the known dimensions, the pixels in dimensional features, and the known distances.

19. The method of claim 15 wherein a plurality of coefficients are calculated and the calculation of the coefficients includes curve fitting to determine the relationship between the known dimensions, the pixels in dimensional features, and the known distances.

20. The method of claim 15 further comprising measuring angioscopic dimensional features with the system by the steps of:

having the computer receive data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image with the tip positioned at a plurality of distances from a feature plane;

determining the distance from said tip to the feature plane based on changes in the data corresponding to moving the position of the tip a known amount; and quantifying the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units.

21. The method of claim 20 further comprising the steps of;

converting said unknown dimensional feature from pixels into dimensional units A1 when the feature plane is at a first unknown distance from said tip based upon a first hypothesized distance from the feature plane to said tip, converting said unknown dimensional feature from pixels into dimensional units A2 when the feature plane is at a second unknown distance from said tip based upon a second hypothesized distance from the feature plane to said tip, said second unknown distance being a known offset from said first unknown distance, and trying different values for said first and second hypothesized distances to yield different values for A1 and A2 by repetitive conversions until A1 and A2 are determined to be sufficiently close that the hypothesized distances are accurate, and wherein the dimensional feature is quantified from A1 and/or A2.

22. The method of claim 20 further comprising the steps of:

converting said unknown dimensional feature from pixels into dimensional units A1 when the feature plane is at a first unknown distance from said tip based upon a first hypothesized distance from the feature plane to said tip, converting said unknown dimensional feature from pixels into dimensional units A2 when the feature plane is at a second unknown distance from said tip based upon a second hypothesized distance from the feature plane to said tip, said second unknown distance being a known offset from said first unknown distance, converting said unknown dimensional feature from pixels into dimensional units A3 when the feature plane is at a third unknown distance from said tip based upon a third hypothesized distance from the feature plane to the tip, said third unknown distance being a known offset from said first unknown distance and/or a known offset from said second unknown distance, and trying different values for said first, second, and third hypothesized distances to yield different values for A1, A2, and A3 by repetitive conversions until A1, A2, and A3 are determined to be sufficiently close that the hypothesized distances are accurate, and wherein the dimensional feature is quantified from A1, A2, and/or A3.

23. The method of claim 22 further comprising selecting accurate hypothesized distances by determining the distances which provide the minimal differences in values for A1, A2, and A3.

24. The method of claim 15 wherein the angioscope includes two image guiding fiber optic bundles spaced apart for providing a stereoscopic image by combining two images, one from each of said fiber optic bundles, and wherein the system is calibrated by performing the placing, measuring, having the computer calculate, and storing steps for each of the fiber optic bundles.

25. A method of obtaining an image from a vessel in a patient by an angioscope, the steps comprising:

inserting a guidewire having an end into the vessel;

inserting the angioscope into the vessel with the angioscope having a tip which is coupled to the guidewire; and

maintaining the tip of the angioscope spaced from the end of the guidewire such that the angioscope is oriented to provide a desired image, and

further comprising the step of determining a distance relative to the tip of the angioscope by viewing indicia on said guidewire.

26. The method of claim 25 wherein a video camera is connected to said angioscope; a monitor is connected to the video camera to display images from the angioscope; and a computer connected to process data from said video camera, said computer having stored coefficients for conversion of pixels into dimensional units for feature planes at different distances from said tip; the steps further comprising;

having the computer receive date representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image with the tip positioned at a plurality of distances from a feature plane;

determining the distance from said tip to the feature plane based on changes in the data corresponding to moving the position of the tip an unknown amount;

quantifying this unknown amount of movement from changes in the image of the guidewire by use of at least one appropriate coefficient to covert from pixels to dimensional units; and

quantifying the dimensional feature by use of at least one appropriate coefficient to covert from pixels to dimensional units.

BACKGROUND OF THE INVENTION

This invention relates to quantification of dimensional features appearing in an angioscope. More specifically, this invention relates to an angioscopic dimensional analysis system for determining the actual size of any feature within an angioscope image. Additionally, this invention relates to a method of calibrating an angioscopic dimensional analysis system and a method of using such a system.

Angioscopes have been used for viewing various features within the cardiovascular system of a patient. The angioscope is a fiber optic instrument which is inserted into the patient. Generally, a light source is provided to illuminate the part of the patient just beyond the tip of the fiber optic cable and a camera may be attached to the end of the fiber optic cable which is remote from the tip. The camera provides an image to a CRT such that a doctor may view the inside of the patient.

Although prior angioscopic systems have been useful, they have generally been unable to provide accurate information about the size of various features. For example, if a patient has a partial blockage in an artery, prior angioscopic systems have been unable to provide the doctor with accurate information as to the size of the blockage.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to provide an angioscopic system which is useful for relatively accurately and simply providing accurate measurements of the dimensions of features within an angioscopic image.

A further object of the present invention is to provide a simple and accurate technique for calibrating such an angioscopic dimensional analysis system.

Yet another object of the present invention is to provide a method of using an angioscopic dimensional analysis system in order to determine the dimensions of a feature within an angioscopic image.

The above and other objects of the present invention, which will become more apparent as the description proceeds, are realized by a system for angioscopic dimensional analysis including an angioscope having a tip. A video camera is connected to the angioscope. A monitor displays images from the angioscope. A computer is connected to process data from the video camera. The computer has stored coefficients for conversion of pixels into dimensional units for feature planes at different distances from the tip. The computer is operable to determine dimensional features within the angioscopic image by use of the following method. The computer receives data representative of the number of pixels corresponding to an unknown dimensional feature of an angioscopic image with the tip positioned at a plurality of distances from a feature plane. Next, the computer determines the distance from the tip to the feature plane based upon changes in the data corresponding to moving the position of the tip a known amount. The computer quantifies the dimensional feature by use of at least one appropriate coefficient to convert from pixels to dimensional units. The determination of the distance from the tip to the feature plane is performed by converting the unknown dimensional feature from pixels into dimensional units A1 when the feature plane is at a first unknown distance from the tip based upon a hypothesized distance from the feature plane to the tip, converting the unknown dimensional feature from pixels int dimensional units A2 when the feature plane is at a second unknown distance from the tip based upon a second hypothesized distance from the feature plane to the tip, the second unknown distance being a known offset from the first unknown distance, and trying different values for the first and second hypothesized distances to yield different values for A1 and A2 by repetitive conversions until A1 and A2 are determined to be sufficiently close that the hypothesized distances are accurate such that the dimensional feature is quantified from the final values of A1 and/or A2. A more sophisticated version of the present invention includes the conversion of the unknown dimensional feature from pixels into dimensional units A3 when the feature plane is at a third unknown distance from the tip based upon a third hypothesized distance from the feature plane to the tip, the third unknown distance being a known offset from the first unknown distance and/or a known offset from the second unknown distance and trying different values for the first, second, and third hypothesized distances to yield different values for A1, A2, and A3 by repetitive conversions until A1, A2, and A3 are determined to be sufficiently close that the hypothesized distances are accurate such that the dimensional feature is quantified from A1, A2, and/or A3. The invention further includes the selection of accurate hypothesized distances by determining the hypothesized distances which provide the minimal differences in values for A1, A2, and A3.

The present invention includes a method for use with the angioscopic dimensional analysis system having the steps comprising calibrating the system by placing at least one known pattern at a series of known distances from the tip of the angioscope such that the video camera generates a corresponding series of images composed of pixels. The number of pixels in a dimensional feature of the pattern having known dimensions for each image is then measured. The computer then calculates at least one coefficient for each known distance, each coefficient useful for conversion of pixels to dimensional units. Each of the coefficients is then stored. The placing step includes the placing of several known patterns at a series of known distances. Each of the images is preferably a circle. The calculation of the coefficients includes curve fitting to determine the relationship between the known dimensions, the pixels in dimensional features, and the known distances.

The measurement technique which relies upon moving the tip of the scope a known amount would, of course, require a technique for determining that amount. The present invention includes a technique for determining (i.e., making "known") the unknown amount of change in position of the tip of the angioscope. Specifically, the technique involves the use of a guidewire which extends beyond the tip of the angioscope and has indicia or markings separated by known distances. By moving the tip of the angioscope and considering the change in apparent distance between two of the indicia or markings, one can readily determine the amount of distance which the tip of the angioscope has been moved. Accordingly, the change in position of the tip of the angioscope is then a known amount which can be used in conjunction with the above techniques for measuring an image of an unknown dimensions. The guidewire, to which the tip of the angioscope is coupled, is also used to stabilize the angioscope and to orient the angioscope such that the field of view of the angioscope is better than would otherwise be the case.

The present invention also includes the technique of calculating the dimensional feature in an image from an angioscope where the distance from the tip of the angioscope to the feature is known. This somewhat simpler technique would involve converting the dimensional feature from pixels into dimensional units based upon knowledge of the relationship between the apparent size of a feature and its actual size, this relationship having been stored in the computer by storage of the various coefficients discussed in more detail above.

The present invention further includes an angioscope having two image-guiding fiber optic bundles spaced apart to provide a stereoscopic image. This arrangement uses stored coefficients for conversion of pixels into dimensional units as with the monoscopic version. However, the distance from the tip of the angioscope to the feature is determined by a comparison between the separate images produced by the different bundles. This stereoscopic angioscope may be used in conjunction with the angioscopic system including a video camera, a monitor, and computer in somewhat similar fashion to the monoscopic angioscope.

The invention further includes a method of obtaining an image from a vessel in a patient by an angioscope. The steps include: inserting a guidewire having an end into the vessel; inserting the angioscope into the vessel with the angioscope having a tip which is coupled to the guidewire; and maintaining the tip of the angioscope spaced from the end of the guidewire such that the angioscope is oriented to provide a desired image. That is, the image of the angioscope will provide a better view of the vessel. The guidewire includes indicia separated by a known distance.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will be more readily understood when the following detailed description is considered in conjunction with the accompanying drawings wherein like characters represent like parts throughout the several views, and in which:

FIG. 1 shows a simplified perspective view of the present system;

FIG. 2A shows a side view of a calibrate,. arrangement used corresponding image sensed by the angioscope and FIG. 2C shows a partial scope image to depict an area calculation technique;

FIG. 3A shows a table of data generated by the calibration technique of FIGS. 2A and 2B, whereas FIG. 3B shows a curve corresponding to the data;

FIG. 4 shows a simplified flow chart of the calibration method according to the present invention;

FIG. 5A shows a simplified side view illustrating the measurements process according to the present invention, whereas FIG. 5B shows the corresponding image on the angioscope;

FIG. 6A shows a simplified side view of an alternate measurement position to that of FIG. 5A, whereas FIG. 6B shows the angioscopic image corresponding to the position of FIG. 6A;

FIG. 7 shows a simplified flow chart for the measurement process of the present invention;

FIG. 8 shows a simplified end view of a stereoscopic angioscope;

FIG. 9 shows a simplified side view of the angioscope of FIG. 8;

FIG. 10 shows a schematic to illustrate the principles of stereovision as used with the arrangement of FIGS. 8 and 9 and illustrates the technique for quantification of objects within the field of view of a stereoscopic angioscope;

FIG. 11 shows a simplified side view of guide wire use according to the present invention;

FIG. 12 shows an enlarged view of a portion of FIG. 11;

FIG. 13 shows a flow diagram of an approximation technique which may be used with the present invention; and

FIG. 14 shows a flow diagram of a technique used in conjunction with the FIG. 13 technique to provide more accurate information.

DETAILED DESCRIPTION

The system 10 according to the present invention is illustrated in simplified form in FIG. 1 and includes an angioscope 12, a video camera 14 connected to the angioscope 12 in known fashion to supply an output signal corresponding to the image as viewed by the angioscope 12. The signal supplied by the video camera 14 is sent to a computer/image processor 16 and a video monitor 18. In addition to displaying the image from the angioscope 12, the monitor 18 allows one to use a cursor (not shown) in combination with the computer 16 in order to input data to the computer 16. Although this feature need not be described in detail, it should briefly be noted that the use of a cursor in connection with a video/computer system is well known and simply allows one to input data to the computer corresponding to points of interest on the image appearing on the video monitor. As shown in FIG. 1, the computer 16 may be considered as including an input means, a storage means, and a processing means.

The present invention is applicable to any angioscope/image processing combination. The choice of actual components for the system 10 would be governed largely by portability constraints. The present measurement technique imposes few limitations on such a system. Without limiting the application of the present invention, it may be noted that an American Edwards Laboratory 0.84 millimeter fiber optic angioscope, Pulnix solid-state color video camera, and IBM PC-AT with numeric coprocessor and Imaging Technology FG-100AT image processing card may be used to realize the system of FIG. 1 together with a video monitor.

The video camera 14 is connected to the image processing card in the computer 16. The image processing card will digitize video frames from the camera and store this video information in the computer's memory as a two-dimensional set of pixels contained in a closed region (i.e., a region corresponding to an area enclosed by a line whose start and end points are identical), each capable of representing any one of 4096 colors or grey levels. Each pixel in the image contains one small portion of the entire angioscope picture. This effectively allows the angioscope image to be broken into a set of individual points which can be analyzed by the computer. Furthermore, if the magnification of the system is known, then the number of pixels between two points in the scope image or the number of pixels contained in a closed region may be directly related to the distance between the two points or the area of the region.

The two-dimensional array of pixels which is stored in the computer's memory by the operation of the image processing card together with the computer in known fashion can be accessed by the computer in several ways. However, the image processing card generally stores the information in a cartesian coordinate system. Therefore, access to this data must likewise use a cartesian coordinate system. Although cartesian coordinates are fine for many applications, their use tends to complicate the expression of systems which exhibit circular symmetry about a central axis. As angioscopes exhibit this type of symmetry, the computer 16 may be programed in known fashion to map the cartesian coordinates into polar coordinates with the central axis of the polar system passing through the center of the scope image corresponding to the center of the angioscope.

It should briefly be noted that most optical fiber angioscopes are composed of several thousands of individual fibers fused into one larger bundle. The arrangement transmits an image from one end of the optical fiber to the other. The image produced at the observer's end of the optical fiberscope is distorted with respect to many parameters. This distortion tends to be non-linear, and the amount of distortion varies from scope to scope. It is the non-linearity of this distortion which allows absolute measurements to be made using the present system.

At the outset, it may be useful to note two assumptions which are made in