Abstract:
A novel medical diagnostic imaging system, method, and apparatus is disclosed. In one embodiment, a reference image is compared with each image in an image stream, and a similarity value is calculated to reflect the degree of similarity between them. If the similarity value is high enough, the image is saved for later use by the diagnostician. 
     In other embodiments, a running list is maintained of the x best-matching frames from the video stream. Images from the list are displayed for the operator.

Description:
BACKGROUND 
     The present invention relates to a system, method, and apparatus for diagnostic imaging. More specifically, a stream of images is compared to a reference image of the diagnostic subject, and image frames with a level of similarity to the reference image are stored for use by a diagnostician in comparison with the reference image. 
     Imaging is used for diagnosis and analysis in various medical fields. In many such applications, a series of images of the diagnostic subject (e.g., a tooth, bone, tumor, or breast), typically including an initial baseline, or “reference,” image and subsequent images, depict changes in a particular structure or structures. Similarities and differences between the baseline image and the later-acquired images are examined and interpreted to aid in the diagnosis or study. 
     A major difficulty with these tools for diagnosis is acquisition of the baseline and later-acquired images from (at least approximately) the same angle, rotation, and zoom/distance with the same lighting conditions and (especially when soft tissues are involved) locations of structures within the subject. Rigid frames have been used in attempts to fix the camera and subject in the same relative position for each image acquisition. Such frames, however, often result in significant discomfort for the patient and may still yield images that are not very well matched with the baseline image. Poorly matched images are, of course, less useful than well matched images for diagnosis and study. 
     There is thus a need for improved systems, methods, and apparatuses to acquire images for use in diagnosis and study. 
     SUMMARY 
     It is, therefore, an object of this invention to provide a novel imaging system, method, or apparatus for medical diagnostic imaging. Another object is to provide a medical diagnostic imaging system, method, or apparatus that is easier to use than certain available systems. A still further object is to provide a system, method, or apparatus that yields time-series images with improved suitability for use in medical diagnostics and study. 
     One form of the present invention is a unique medical diagnostic imaging. 
     In another form of the present invention, a reference image is compared to a series of captured images from an image stream. The level of similarity between the reference image and the captured image is determined and used to decide whether to store the captured image for diagnostic use. In one embodiment of this form, all captured images with a level of correlation above a pre-determined level are stored. In another embodiment, the best n captured images are stored for diagnostic use. In some embodiments, the level of similarity is represented by a number, the similarity value. In some embodiments, the evaluation of the similarity between a captured image and the reference image is accomplished using analog techniques, while in other embodiments the level of similarity is determined using digital techniques. 
     Another form of the present invention is a method for collecting images for medical diagnostic use, wherein a reference image is compared with a captured image from an image stream to determine the level of similarity between the two images. Based on that level of similarity, a decision is made whether to retain or discard the captured image. In some embodiments, the reference image and the image stream are displayed together as the image stream is captured, for example, in side-by-side windows on a computer monitor. Other embodiments show the reference image and the image stream in the same window, wherein the lines from the two images are interlaced. In yet other embodiments, the difference image between the reference image and the image stream is displayed during capture. In still other embodiments, the shadow of one is placed over the other and displayed during capture. 
     In another form of the present invention, a system comprises data storage (containing a reference image of a diagnostic subject); an image stream of captured images showing the diagnostic subject; a processor, connected to the data storage, that receives the image stream; and a computer readable medium encoded with programming instructions executable by the processor to (1) calculate a similarity value for each captured image; and (2) determine whether to store the captured image based on its similarity value. 
     Other embodiments, forms, variations, objects, features, and applications may appear to those skilled in the art from the drawings and description contained herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a diagnostic imaging system according to one embodiment of the present invention. 
     FIGS. 2A and 2B are complimentary portions of a flow chart of an automatic selection process according to one embodiment of the present invention. 
     FIG. 3 is a partial block diagram of a remote access storage and analysis system for use with one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will, nevertheless, be understood that no limitation of the scope of the invention is thereby intended; any alterations and further modifications of the described or illustrated embodiments, and any further applications of the principles of the invention as illustrated therein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
     The present invention relates to a system for obtaining medical diagnostic images that are easier to compare with prior images of the same structure. While the present description will be given in terms of oral structures, such as teeth, the principles of the invention may easily be applied to other medical diagnostic scenarios such as, for example, mammography or endoscopy. 
     Furthermore, while the illustrated embodiment uses video to acquire the new image stream, it will be understood by those skilled in the art that other means for acquiring a series of images (such as a fixed camera or self-contained frame grabber) may be used without undue experimentation. 
     Still further, while the illustrated embodiment and associated description uses the term “correlation” to indicate a measure of similarity between two images (quantified as a “correlation value”), any metric and method that would occur to one skilled in the art may be used for this comparison. The terms “similarity,” “similarity calculation,” and “similarity value” refer herein to the full scope of available metrics and methods that one skilled in the art might use in the context of this invention. For example, the various correlation calculations shown in U.S. Pat. Nos. 5,907,641, 5,987,162, and 5,982,915 (hereby incorporated by reference, as if included in their entireties) may be used. 
     Generally, the system  20  illustrated in FIGS. 1 is used by an operator (not shown) to acquire one or more new images of a diagnostic subject  30  (illustrated here as a tooth), such that the new images show the diagnostic subject  30  from approximately the same angle and orientation, with similar lighting and magnification (and/or distance from the subject  30 ) as does a reference image  48 . The operator aims camera  22  in the general direction of the diagnostic subject  30 , and the camera  22  captures video  24  of the diagnostic subject  30 . The video stream  24  is displayed on monitor  51  along with the reference image  48 . The operator uses this video feedback to position and control the camera  22  so that the frames of the video signal approximate the reference image  48 . The video signal  24  output from camera  22  comprises image frames  42 ,  44 , and  46 , which are processed by logic and storage unit  50 . One or more of video frames  42 ,  44 , and  46  are selected for storage in storage  52  based on their degree of similarity to reference image  48 . Diagnosis or study related to diagnostic subject  30  is then carried out using the selected frames. 
     System  20  will now be discussed in further detail with continuing reference to FIG.  1 . Video stream  24  of diagnostic subject  30  is acquired by camera  22 , which in this example is an intra-oral camera such as model LS1 manufactured and marketed by Sony Electronics. Other models and manufacturers may, of course, be used, and the invention may easily be applied in different medical diagnostic contexts as will occur to those skilled in the art. 
     Video stream  24  comprises a series of video frames illustrated here as frames  42 ,  44 , and  46 . In operation, a doctor, nurse, or technician (generically “operator” herein) aims camera  22  at the diagnostic subject  30  so that most of the frames  42 ,  44 , and  46  in video stream  24  show all or part of diagnostic subject  30 . Video feedback techniques (described in more detail below) provide assistance to the operator as he or she controls the position, zoom, rotation, focus, and other properties of camera  22  to match the qualities of the newly captured images to the reference image, and thereby achieve the best possible results. 
     The video stream  24  is transmitted from the camera to logic and storage unit  50 , which in this example is a general-purpose computer. Correlator  54  receives the video stream  24  and compares each frame  42 ,  44 , and  46  to reference image  48 , which is stored in storage  52 . The level of correlation between a given frame and the reference image  48  is expressed by a number, the correlation value. The correlation value is communicated to processor  56 , which operates switch  58  as described below to store in storage  52  the video frames  42 ,  44 , and  46  that best correlate to reference image  48 . 
     Video processor  53  retrieves from storage  52  the reference image  48  and the images previously selected from video frames  42 ,  44 , and  46 , then displays them on monitor  51  using any of the many techniques that would occur to one skilled in the art. For example, the illustrated embodiment displays the reference image (shown here as reference image  48 A) in the center of a 3×3 array of images. Previously captured images  41 ,  43 ,  45 ,  47  are displayed in other cells of the array, with the current image  49  displayed in a highlighted cell, as indicated by a heavier bordering line around current image  49  compared to the other images  41 ,  43 ,  45 , and  47  illustrated on monitor  51 . In the present example, alternating scan lines for image  49  are drawn from the reference image  48 A and from the current video frame of video stream  24 . The operator, therefore, receives feedback by way of image  49  to assist in achievement of proper positioning, orientation, and control of camera  22  to acquire a new image  49  of diagnostic subject  30  that closely matches reference image  48 . 
     In other embodiments, image  49  is formed by shadowing the reference image  48  over the current frame of video stream  24 . In still other embodiments, the operator observes image  49  (consisting only of the video stream  24 ) and manually compares it to the reference image  48 A on monitor  51 , then moves and controls camera  22  as needed to achieve a good match between the current video frame from video stream  24  and reference image  48 A. 
     In the illustrated embodiment, operation of the various elements and components of logic and storage unit  50  is controlled by processor  56  according to programming instructions encoded on a computer-readable medium comprising program store  55 . Besides camera  22 , additional input device(s)  57  (for example, a keyboard, a pointing device, a microphone, and a portable data storage unit) may be used by the system  20  to receive input from the operator. Besides monitor  51 , additional output device(s)  59  (for example, a sound synthesizer and speakers, a printing device, and an additional monitor) may be used by the system  20  to interact with the operator. 
     The selection process implemented by system  20  of FIG. 1 will now be described with reference to FIGS. 2A and 2B, and with continuing reference to elements shown in FIG.  1 . Process  100  begins at start point  101 , and a reference image  48  of the diagnostic subject  30  is acquired or selected (input block  103 ) using any suitable means. Correlator  54  is initialized (block  105 ) and an empty list of images (and their corresponding correlation values) is created, to be filled as process  100  proceeds. The list is preferably implemented as a priority queue keyed on the correlation value of the respective video frames in the list. 
     The process  100  waits (decision block  107 ) for the user to start the video capture routine. When the user indicates (positive result at decision block  107 ) that the process should commence, a frame is grabbed (block  109 ) from the video stream  24 . A correlation value, representative of the level of correlation between the grabbed frame and the reference image  48 , is calculated (block  111 ). This calculation can use any metric that might occur to one skilled in the art. (After the correlation calculation in block  111 , the process  100  continues through point A on FIG. 2B.) 
     Next it is determined (decision block  113 ) whether the correlation value of the current frame (computed at block  111 ) is good (high) enough to warrant retention of the frame. In one form of decision block  113 , the correlation value for the current frame is compared with the correlation value for the worst-matching frame on the list. If the correlation value for the current frame is higher (positive result at decision block  113 ), the current frame is retained as will now be discussed in relation to blocks  115 - 119 . 
     It is first determined (decision block  115 ) whether the maximum allowable number of images is already in the list. If so (positive result at decision block  115 ), the worst image on the list is deleted (block  117 ). Then (or following a negative result at decision block  115 ) the current frame is inserted (block  119 ) into the list. 
     After the insertion (block  119 ) or a determination that the correlation value is too low to justify retaining the image (negative result at decision block  113 ), the image/frame display on monitor  51  is updated ( 121 ) to reflect the current list of “best” images. The process  100  checks (decision block  123 ) whether the operator has signaled the end of the image acquisition phase. If so (positive result at decision block  123 ), process  100  ends at end point  199 . If not (negative result at decision block  123 ), process  100  continues (via point B back to FIG. 2A) by grabbing (block  109 ) another image from the video stream  24 . 
     Many alternative display schemes may be used with the present invention. In one arrangement, a single image is displayed on monitor  51 ; while in other arrangements, two or more images are displayed simultaneously (side-by-side, in an array, etc.) or in alternating scans. In any of these arrangements, the images being displayed may be the reference image, the video stream  24 , one or more previously selected images (e.g., image  41 ,  43 ,  45 , or  47 ), or a combination thereof formed by alternating lines or overlaying any of the above, using any means, arrangement, format, and technique that might occur to one skilled in the art. 
     In an alternative embodiment illustrated in FIG. 3 (with reference numerals from FIGS. 1,  2 A, and  2 B being re-used here for analogous components), the processing illustrated and discussed above in relation to logic and storage unit  50  (in FIG.  1 ), and process  100  (except the display at block  121  in FIGS. 2A and 2B) is done remotely from the diagnostic subject  30  by an independent service vendor (ISV)  201 . The video stream  24  and reference image  48  are transmitted from a patient location  203  through a network  205  (for example, the Internet) to the ISV  201 . The ISV  201  selects the best image(s)  207  from the video stream  24  as described above in relation to FIGS. 1,  2 A, and  2 B (see especially blocks  111 ,  113 , 115 , 117 , and  119  of FIGS.  2 A and  2 B). ISV  201  then sends those best image(s)  207  back to the patient location  203  through network  205 . 
     Additional interconnections, processors, and networking elements may be added to or substituted for the items described herein. Furthermore, all or some of the elements of logic and storage unit  50  (such as correlator  54  and switch  58 ) may be implemented in software executed by processor  56 . 
     In some embodiments of the present invention, the additional input device(s)  57  (see FIG. 1) may be used to accept override input from the operator. For example, if the operator considers one of the images in the current list of “best” images to be unacceptable (or simply less desirable than another), an override input signal related to that image triggers deletion by processor  56  of that image from the current list of images to be stored. Other operator override signals may be implemented without undue experimentation by those skilled in the art. 
     In various embodiments of the present invention, some or all of the components, structures, and tasks disclosed herein may be implemented by one or more general-purpose computers, such as those manufactured by Dell, Compaq, and IBM. In some embodiments, some or all of the components, structures, and tasks disclosed herein may be implemented by one or more application-specific integrated circuits (ASICs). Furthermore, in many embodiments, the correlation calculation may be implemented in one or more analog components. 
     Other wiring, networking, and storage structures may be used as appropriate for a particular implementation of the present invention and would occur to one skilled in the art. 
     Modifications of the present disclosure and claims, as would occur to one skilled in the art, may be made within the scope of the present invention. While the disclosure above has been made in relation to preferred embodiments, the scope of the invention is defined by the claims appended hereto.