WO1991005360A1

WO1991005360A1 - Video pixel spectrometer

Info

Publication number: WO1991005360A1
Application number: PCT/US1990/005479
Authority: WO
Inventors: Sol Nudelman; Richard A. Buchroeder
Original assignee: The University Of Connecticut
Priority date: 1989-09-26
Filing date: 1990-09-26
Publication date: 1991-04-18

Abstract

A video pixel spectrometer system employs an image aquisition device (12) and a spectrometer (14) to provide a video display of the spectral characteristics of an image sector for a series of discrete positions of the image sector. The output from the spectrometer (14) is converted to digital data and processed for displaying various video displays (D1, D2, D3, D4 and D5) of the spectral characteristics. Cameras (24, 26 and 28) are also employed to acquire images for processing of various physical features and to aid in positioning the input image.

Description

VIDEO PIXEL SPECTROMETER

Background of the Invention

This invention relates generally to diagnostic imaging systems such as employed in the medical technologies. More particularly, the present invention relates to imaging systems which can employ spectrometers to undertake spectral analysis of various structures and substances.

Spectrometers have long been employed for conducting spectral analysis of various substances and/or structures. Conventional spectrometers employ a narrow input slit to essentially direct radiation from a point or an area-type source through the slit to a prism or a grating for dispersion into various wavelength components. Recent advancements in digital processing technology have made possible the increasingly sophisticated and complex processing of spectral data. In addition, the improvements in various medical imaging devices have resulted in high resolution images which can be employed fo medical diagnoses and analyses. Summary of the Invention

Briefly stated, the invention in a preferred form is a vide pixel spectrometer having an input slit and an output opening. The spectrometer includes a prism for dispersing radiation and various optical components providing a two dimensional spectral image. The image corresponds to discrete positions along a line of an image sector which is projected through the spectrometer input slit. An image acquisition device such as an endoscope can be employed for acquiring the image of the object to be examined. An optical coupler transmits the image acquired by the acquisition device to the input jaws and the slit of the spectrometer. A digital processor communicates with the output of the spectrometer for processing the spectral output and displaying spectral characteristics of the output for each of the series of pixels corresponding to the discrete positions of the input image along the slit.

A beam splitter may be incorporated into the optical coupler. A video camera optically communicates with the beam splitter for viewing the acquired image. This image is also fed to an image processor. In addition, a second camera may be employed for viewing the image projected onto the jaws of the slit. The second camera serves to identify the sector of the image passing through the slit. The spectrometer in a preferred form employs a prism having a spectral response in the range of approximately 3000 Angstroms to 2 microns. An intensifier is employed to intensify the signal received at the output of the spectrometer. A positioner is also employed for variably positioning the image which is projected onto the slit.

The output spectra is processed and can be displayed on one or more video screens with information such as : the intensity spectrum for each wavelength from any individual pixel; the intensity spectrum from any two or more pixels displayed simultaneously; and a comparison of the spectrum from any two or more pixels.

A method for analyzing tissue for diagnostic purposes in accordance with the invention comprises acquiring an image of the tissue. A sector of the image is projected through the input slit of a spectrometer. The sector image is dispersed to provide a spectral image corresponding to discrete linear positions of the sector. The spectral images are converted to digital data and processed to form enhanced images. The spectral image has a two dimensional format which may be displayed on a video display. Spectral images can be compiled in a library, displayed on a video display and compared to the spectral images from the tissue.

Simultaneously, a video image of the tissue may be processed for feature characteristics such as texture, boundaries and growth patterns. Such data can be correlated with spectral characteristics for improved diagnosis. Such data can also be compiled in a library and subsequently compared with data from newly acquired imaging data for further processing and/or display. An object of the invention is to provide a new and improved video pixel spectrometer.

Another object of the invention is to provide a new and improved video pixel spectrometer which is capable of being employed in conjunction with medical image acquisition systems.

A further object of the invention is to provide a new and improved video pixel spectrometer which is capable of providing simultaneous spectral analysis for a series of points along the line of an image.

Other objects and advantages of the invention will become apparent from the drawings and the specification.

Brief Description of the Drawings

Figure 1 is a general schematic diagram of a video pixel spectrometer system in accordance with the present invention;

Figure 2 is a schematic view illustrating various components of the video pixel spectrometer system in accordance with the present invention;

Figure 3 is an interior side elevational view, partly in schematic, partly in section, and partly in diagrammatic form with portions being removed, of a video pixel spectrometer in accordance with the present invention;

Figure 4 is an interior top plan view, partly in schematic, partly in section, and partly in diagrammatic form with portions being removed, of the spectrometer of Figure 3;

Figure 5 is an interior side elevational view, partly in schematic, of the spectrometer of Figure 3;

Figure 6 is fragmentary interior rear view viewed from the left of Figure 3;

Figure 7 is a schematic diagram of the spectrometer system of Figure l including a schematic side elevational view of an optical coupler employed in the spectrometer system of Figure 1;

Figure 8 is an output display for the spectrometer system o Figure 1 illustrating a spectral plot from two pixel elements; Figure 9 is a second output display for the spectrometer system of Figure 1 illustrating a columnar spectral plot from tw pixel elements; and

Figure 10 is a third output display for the spectrometer system of Figure 1 illustrating spectra from a color test pattern. Detailed Description of the Invention

With reference to the drawings wherein like numerals represent like parts throughout the figures, a video pixel spectrometer (VPS) optical system in accordance with the present invention is generally designated by the numeral 10. The VPS system 10 is adapted for acquiring an image of an object to be examined and for processing said image to provide a detailed examination of selected physical characteristics simultaneously with spectral analysis of the radiation emerging from a selected portion of the image. The VPS system 10 has particular applicability in connection with medical diagnostic technologies although the invention is not limited to medical applications.

For example, the invention is readily applicable to imaging systems employed in non-distructive testing.

With reference to Figure 1, the VPS system 10 comprises a medical image acquisition device 12 such as an endoscope, microscope, fundus camera or other device which generates an image of tissue and/or structure to be examined. The image is transmitted to a video pixel spectrometer 14 via an optical coupler 16. The optical output from the spectrometer is transmitted via a light intensifier 18 and an intensified video camera 28 to a digital image acquisition and processing system

20. The output from the image acquisition and processing system

20 is displayed on a display console designated generally by the numeral 22. Video cameras 24 and 26 are also connected with the optical coupler 16 to provide unprocessed and/or processed readily viewed images of the principal images acquired by the medical image acquisition device and readily viewed images of the selected image portion which is projected into the spectrometer 14.

With additional reference to Figures 3 through 6, the spectrometer 14 has a generally rectilinear housing 30 which houses the various optical components. A pair of jaws 32 define an input slit 34 which in one embodiment has a length of approximately 10 millimeters. The input slit 34 defines the image line to be analyzed. The jaws are preferably coated with reflective surface to provide an optical path for communication with video camera 26.

An input mirror 36 behind slit 34 is pivotally mounted to a support bracket 35 which extends perpendicularly at the interior. Mirror 36 directs the image toward a spherical mirror 38 which is supported by a bracket 40 secured to a support 41 mounted at the rear of the housing. A fused silica prism 50 is mounted at the housing interior by means of a bracket 52. The image is reflected from mirror 38 through the dispersing prism 50 and onto aspheric mirror 54. The image is reflected from the aspheric mirror 54 back through the prism 50 to mirror 38. The optical path then extends from mirror 56 to an outlet mirror 42 which directs the spectral output through the spectrometer outlet 44. The aspheric mirror is mounted by a bracket 55 which is pivoted about pin 57. A dial gage 60 includes a stem 62 which is moved by rotation of the aspheric mirror 54. A micrometer driving screw 64 has an adjustment knob 65 which moves the aspheric mirror 54. The dial gage 60 gives the location of the aspheric mirror 54 in millimeters for which a corresponding angular location can be determined. In one embodiment of spectrometer 14, the angular range of movement in the visible spectrum is approximately 1.22 degrees and corresponds to a 1.49 millimeter travel for the dial gage or the micrometer. The aspheric mirror 54 can be selectively pivoted about pin 57 to select any wavelength as the central wavelength. This adjustment minimizes spherical aberration and coma. In one embodiment, the spectrometer was calibrated for a central wavelength of 632.8nm at minimum deviation angles through the prism.

The optical coupler 16 comprises a housing 70 having an input end 72 which couples with the medical image acquisition device 12. A holder 75, such as illustrated in Figure 7, may be employed for mechanically coupling the image acquisition device 12 to the input end 72 of the coupler 16. The input coupler may have a bayonet-type configuration. The outlet coupler 74 may also have a bayonet configuration which couples to the spectrometer exterior surrounding the jaws 32. Beam splitters 76 and 78 are interposed in an optical path within the housing 70 for providing an optical path to the video cameras 24 and 26. Alternately, the beam splitters may be opposite surfaces of one beam splitter unit. Camera 24 records the image of the tissue examined as viewed from the image acquisition device. Camera 26 records the image which is projected onto the jaws of the spectrometer and the location of the slit. Reflective coating applied to the jaws provides an optical path to the beam splitte 78.

One or both of the beam splitters may be removed from the coupler 16 to enhance the light intensity to the spectrometer. The beam splitters 76 and 78 may each be readily mounted as a unit to the coupler housing 70 and/or dismounted therefrom in accordance with a given application. A positioning mechanism 80 may be attached to provide a position adjustment wherein the portion of the tissue which is projected onto the jaws of the spectrometer may be selectively determined. A micrometer knob 82 may be employed for implementing the positioning. The images from camera 24 and 26 (as described hereafter) are employed in conjunction with manual operation of the positioning mechanism 80. Camera 26 is optional. In alternative embodiments, a single video camera system could be employed to accomplish both image acquisition and positioning of the acquired image. Alternately, the positioning may be accomplished by variably positioning the distal end of the image acquisition device and fixing the optical interface between the proximal end of the device and the coupler. Ordinarily positioning of the acquired image is accomplished by the latter procedure.

The length of the spectrometer input slit 34 approximately corresponds to one dimension of the two dimensional projection of the output spectrum through the outlet opening 44 of the spectrometer. The output spectrum is essentially planar at the outlet opening 44 and generally perpendicular to the central optical axis through the opening 44. Each point (pixel) of the input image along the slit has a corresponding point along an axis of the orthogonally oriented spectrometer output. The spectral resolution is determined by the prism 50 and the various optical components as previously described for the spectrometer. Each pixel element corresponds with a spectrum which is projected preferably in the vertical direction in Figure 2 with the short wavelength limit (approximately 3000 Angstroms) at the bottom of the graphical illustration and the near infrared (approximately 2 microns) at the top of the illustration.

The output spectrum is recorded by a third video camera 28 which is essentially one or more imaging devices depending upon the particular spectral range of concern for a given procedure and the intensity of the spectrum. A low light level intensifier

18 which is used for low light level images is selected for a specific spectral response. The intensifier 18 is coupled to the video camera 28. Intensifiers may also be employed with cameras

24 and 26. The low light intensifier 18 may be a proximity focused intensifier such as the Varian Model Proximity Focused

Intensifier.

The output from the light intensifier 18 is input to the

T.V. camera 28 and thence to the digital imaging processing system 20. The digital processing system 20 may comprise a digital image processor such as a Gould IP 9000 digital image processor or an IBM-type compatible computer. Software such as the "Gould Graphic User Menu" may be employed to distribute the digital images and to aid in processing. The computer preferably communicates with the video console 22 having video displays Dl, D2, D3, D4 and D5. The video displays can assume a number of configurations, examples of which are described as follows:

Video display Dl may be a display which provides an image screen depicting the principal image acquired by the medical image acquisition device. The display Dl may be employed for determining the suitability of an image on a preliminary basis.

The depicted image may additionally include reflected radiation which is beyond the visible spectral range. The video camera 24 may have sensors which are responsive to ultraviolet and near infrared so that the non-visible spectrum can be displayed in shades of grey or pseudo-color.

Video display D2 displays the image from the medical acquisition device which is projected onto the jaws 32 of the input slit 34 of the spectrometer. Naturally, the positioning of the portion of the image to be analyzed onto the spectrometer jaws must be accomplished in a precise manner. The video camera 26 is trained on the jaws of the input slit which are coated so as to function as an efficient reflector. The image which is acquired by camera 26 is shown on display D2. The slit 34 essentially defines the analyzed sector of the image having a length corresponding to the slit length and a width corresponding to precisely the slit width. In one embodiment, the positioner 80 allows for the viewer or operator to position the image so that a given sector can be selected to fall on the entrance slit 34. In an alternate embodiment, positioning is accomplished by maneuvering the image acquisition device. For example, any object such as a lesion within the overall image can be positioned so that the radiation passes through the spectrometer for a detailed spectral analysis. Displays Dl and D2 are used to obtain the displayed image sector to be examined. Video display D3 represents the output image from video camera 24 which is also transmitted to the digital image processing system 20. Display D3 thus represents a processed image which is composed to account for processing techniques suc as edge enhancement, contrast enhancement, pseudo-color, real color, size discrimination, texture, magnification and other processing techniques which are appropriate for a given procedure. Display D3 is preferably interactive to permit viewing during and after the processing of the image. Video camera 24 thus requires sensitivity throughout the spectral rang of interest and also requires excellent performance specifications in terms of dynamic range plus spatial resolution which is sufficient to send a non-degraded image to the processing system 20.

Video display D4 represents the output spectrum from the spectrometer. With reference to Figure 2, the spectrum may, for example, be illustrated wherein the longitudinal expanse of the slit 34 is projected along the horizontal axis. The scale along the horizontal axis corresponds to positions along the entrance slit. Spectral information is displayed vertically so that the ordinate scale corresponds to wavelength. The data can be displayed as a matrix of numbers where each number corresponds to the number of recorded photons such as illustrated in Figure 9 for two selected pixels designated as pixel 100 and pixel 250.

Ordinarily, the display can be illustrated in terms of shades of grey to provide visual comparison of spectra such as illustrated in the color test display pattern of Figure 10. Moreover, pseudo-color may also be employed to illustrate both visible and non-visible spectra for purposes of analysis.

Video display D5 represents the graphic plot of spectra which is derived for one or more pixels selected on the horizontal axis of display D4 such as illustrated in Figure 8 for pixels 100 and 250. A physician may view an image on display Dl and observe a region of suspicion such as, for example, a lesion. The image on display D2 is viewed to aid in positioning the desired image section of display Dl onto the slit 34 of the spectrometer. The physician may then examine display D4 and note the relative spectrum changes from one pixel to another so that one pixel (pixel 100) may be located within the lesion and a second pixel (pixel 250) may be located just outside the lesion. With reference to Figure 8, the spectrum from each pixel is then plotted simultaneously on display D5 revealing their similarities and differences.

Automation of the diagnosis (or hypothetical diagnosis) is made possible by a library of spectra which is associated with known normal and disease tissue. A library is compiled into a database and easily made available for comparison. The library is accessed or displayed on display D5 when required.

In general, spectral recorded in medical procedures are broad band. Thus, it is likely that in many instances such broa band spectra will often not be sufficient to provide readily apparent characteristics suitable for identifying many kinds of diseased tissue with a simple spectral signature. In such cases, the spectra must be processed to reveal any subtle indentifying features. Furthermore, it is possible that the subtle changes i spectra will have to be correlated with various physical characteristics of the tissue to ascertain a final diagnosis. Such characteristics can include texture, growth patterns plus boundary shapes and conditions.

The spatial resolution which is achievable by the VPS system 10 is a function of the size of the pixel element. The size of the pixel element is a function of the performance of the components of the VPS system including the image acquisition device 12, the spectrometer 14 and the digital image acquisition system 20. Each raster line of the image may be subdivided into as many pixels as the digital computer system will allow. For example, for a 2048 x 2048 matrix system, a 6 to 10 inches linear section of an imaged breast could be composed of 2,048 pixels or alternately a few millimeters of linear sector from a small tissue sample could be composed of 2,048 pixels. Naturally, a number of different pixel matrices systems could be employed. Ordinarily, a 512 or 1,024 pixel format would be sufficient for most diagnostic practices. A 2,048 pixel format could be implemented with procedures which need a greater spatial resolution and/or span large areas.

It should be appreciated that the spectral band for the spectrometer 14 can be quite broad. A broad spectral band would be required for a general medical diagnostic applicator. In a preferred embodiment, the spectral band of the spectrometer ranges from approximately 3,000 Angstroms to approximately 2 microns. This could be accomplished with a quartz prism. A grating (not illustrated) may be employed instead of a prism when only certain selected spectral regions are required for analysis.

While the preferred embodiment of the foregoing invention has been set forth for purpose of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and the scope of the present invention.

Claims

WHAT IS CLAIMED IS

1. A video pixel spectrometer system comprising: spectroscope means comprising input means and output means, and prism means for dispersing incident radiation, sai input means defining a slit, and optical path means traversing said prism means and extending from said slit to said output means for providing a spectral output having a spectral image corresponding to discrete positions along a line of an image projected through said slit; image acquisition means for acquiring an image of an object to be examined; optical coupling means for coupling said image to the input means of said spectroscope means; and digital processing means communicating with said output means for processing said spectral output and displaying spectral characteristics of said output for each of a series of pixels corresponding to the discrete positions of said input image.

2. The spectrometer system of claim 1 wherein said optical coupling means further defines an optical path and comprising beam splitter means interposed in said path.

3. The spectrometer system of claim 2 further comprising camera means optically communicating with said beam splitter means for viewing the acquired image.

4. The spectrometer system of claim 1 further comprising second camera means for viewing the image portion projected onto said slit.

5. The spectrometer system of claim 1 wherein said spectroscope means further comprises a prism having a spectral response in the range of approximately 3,000 Angstroms to 2 microns.

6. The spectrometer system of claim 1 wherein said image acquisition device is an endoscope.

7. The spectrometer system of claim 1 wherein said processing means comprises intensifier means for intensifying the spectrum output from the spectrometer.

8. The spectrometer system of claim 1 further comprising positioning means for variability positioning the image projected onto said slit.

9. The spectrometer system of claim 1 further comprising first display means for displaying the light intensity spectrum for each pixel.

10. The spectrometer system of claim 1 further comprising second display means for displaying the electromagnetic spectrum intensity corresponding to each of a series linear positions of the input image.

11. A method for analyzing tissue for diagnostic purposes comprising:

(a) acquiring an image of the tissue;

(b) projecting a sector of the image through an input slit of a spectrometer;

(c) dispersing the sector image to provide a spectral characteristics corresponding to discrete linear positions of said sector; and

(d) displaying said spectral output on a video display.

12. The method of claim 11 further comprising:

(e) comparing said spectral images to corresponding images compiled in a library.

13. The method of claim 11 further comprising:

(f) converting said spectral images to digital data and processing said data to form an enhanced image.

14. The method of claim 11 further comprising:

(h) acquiring an image of the sector and employing the sector image to position the sector projected through the input slit.

15. The method of claim 11 further comprising:

(i) processing said spectral image and producing an enhanced video display having an axis corresponding to discrete positions of the sector and a second axis corresponding to wavelength.

16. A video pixel spectrometer system comprising: spectroscope means comprising input means and output means, and dispersing means for dispersing incident radiation, said input means defining a slit, and optical path means traversing said dispersing means and extending from said slit to said output means for providing a two dimensional spectral output at said output means having a spectral image corresponding to discrete positions of an input image projected through said slit; image acquisition means for acquiring an image of an object to be examined; optical coupling means for coupling said acquired image to the input means of said spectroscope means; and digital processing means comprising light intensifier means for intensifying said spectral output, computer means for converting said spectral output into digital data and for processing said data and display means communicating with said computer means for displaying spectral characteristics for each of a series discrete positions of said input image.

17. The spectrometer system of claim 16 wherein said optical coupling means further defines an optical path and comprising beam splitter means interposed in said path for splitting said optical path and further comprising camera means optically communicating with said beam splitter means for viewin the input image.

18. The spectrometer system of claim 16 further comprising enhancement means for deriving and displaying spectral characteristics of said input image for wavelengths beyond the visible spectrum.

19. The spectrometer system of claim 16 further comprising positioning means for variably positioning the sector of the acquired image which is projected through said slit.

20. The spectrometer system of claim 16 wherein said dipersing means further comprises a prism and said optical path means defines an optical path which traverses said prism twice.

21. The spectrometer system of claim 3 wherein said camera means transmits the image to the processing means for quantification of physical characteristics of the object being imaged.

22. The spectrometer system of claim 21 wherein said physical characteristics are correlated in processing with spectral characteristics of said output.