Abstract:
A method and apparatus for recording and analyzing the gait of an animal is provided. The apparatus can take the form of a gait imaging system. The system includes a movable belt track upon which a subject can ambulate. An imaging device is disposed below the belt track to record contact between at least one limb of the subject and the belt track. The subject can ambulate along the belt track in a substantially stationary location above the imaging device as the belt track moves, and the imaging device can record the contact by the subject. A method of recording a gait of an ambulating subject is also provided. The method includes locating the subject on a movable belt track. The subject is motivated to ambulate along the movable belt track at about the same rate as the movable belt track, while the belt track is moving, such that the location of the subject does not substantially change. Contact made by at least one limb of the subject with the belt track is recorded with a recording device underneath the belt track. Additional kinematic analysis can occur of the subject&#39;s gait. The method of recording can further include transmission of the gait images to a computing apparatus. The computing apparatus can identify footprint image data, including filtering out unwanted noise. The computing apparatus can then carry out the kinematic analysis, including calculation of physiological information relating to the subject.

Description:
RELATED APPLICATION  
       [0001]    This application claims priority to co-pending U.S. Provisional Application No. 60/322,563, filed Sep. 17, 2001, for all subject matter common to both applications. The disclosure of said provisional application is hereby incorporated by reference in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to an apparatus and method suitable for monitoring locomotion kinematics in ambulating animals, and more particularly to monitoring, measuring, and imaging the gait of a small animal, such as a mouse.  
         BACKGROUND OF THE INVENTION  
         [0003]    Animals, for example mice, are used extensively in the examination of gene function, the development of drugs, and in other laboratory research applications. Often, the animals are constantly moving around, making it difficult to examine them for measurements of physiological parameters. However, mice are desirable mammalian models for examining locomotion kinematics, such as stride length, foot placement, and speed of ambulation.  
           [0004]    A conventional method for measuring locomotion indices, such as stride, is by painting the feet of the mice and allowing the mice to walk on a clean, stationary, sheet of white paper. Analysis of the tracks created by the painted feet of the mice can be interpreted for derivation of the gait and stride indices. See for example, Gurny, M E et al.,  Science  264:1772-1775, 1994.  
           [0005]    Another conventional method for measuring locomotion indices is described in Clarke and Still,  Physiology and Behavior  66:723-729, 1999. The method involves gait analysis in a mouse using simultaneous video and reaction force analysis. An extension of a similar system described by Clarke for rats can be found in Physiological Behavior 58:415-419, 1995. The system for rats consisted of two cameras positioned below a U-shaped Plexiglas tunnel about 12 inches in length. One or two cameras positioned below the central part of the tunnel record under-views of the walking mouse. The images of the walking mouse are recorded on videotape. The videotape is then analyzed for locomotive indices. A minimum number of steps, about six, is needed for robust interpretation of the data. A longer tunnel would better provide the space required to obtain good data of the walking mouse. However, a longer tunnel would require additional cameras, movement of the camera approximately at the same speed as the walking mouse, or rotation of the cameras following an approaching mouse and a departing mouse. The last option results in some optical distortion as the viewing angle of the mouse changes, along with the distance to the mouse.  
         SUMMARY OF THE INVENTION  
         [0006]    There is a need in the art for a system and method for recording and analyzing the gait of an animal that simplifies the acquisition of data and images, improves the quality of data and images retrieved, and increases the amount of data obtainable without significantly increasing the time or complexity of the data acquisition process. The present invention is directed toward further solutions to address this need.  
           [0007]    A gait imaging system is provided. The system includes a movable belt track upon which a subject can ambulate. An imaging device is disposed below the belt track to record contact between at least one limb of the subject and the belt track. The subject can ambulate along the belt track in a substantially stationary location above the imaging device as the belt track moves, and the imaging device can record the contact by the subject.  
           [0008]    In accordance with aspects of the present invention, the belt track can be a substantially transparent belt track through which the imaging device can view the contact of the subject with the belt track. The imaging device can take the form of a camera, camcorder, or a digital image capturing device, suitable for recording ambulation of the subject over a desired period of time.  
           [0009]    In accordance with further aspects of the present invention, the belt track can be a belt having a markable surface. The imaging device can be a reservoir of ink upon which the at least one limb of the subject can apply pressure, through the belt track, transferring ink from the reservoir to the markable surface of the belt track.  
           [0010]    In accordance with further aspects of the present invention, the speed of movement of the belt track is adjustable. The system can further include a structure disposed to substantially surround the subject while the subject is on the belt track, for motivating the subject to ambulate when the belt track is moving and prevent the subject from escape. The structure can have a plurality of walls forming an enclosure hovering above the moving belt track. The structure can have one or more additional enclosures for motivating more than one subject to ambulate concomitantly.  
           [0011]    In accordance with further aspects of the present invention, the system can further include a computing apparatus supporting a software application for manipulating and analyzing the data from the recorded subject contact. The software application can identify placement of the at least one limb of the subject based on the recorded subject contact. The software application can execute at least one algorithm for analysis of a gait of the subject based at least in part on the subject contact. The imaging device can record images at a rate of at least about 60 frames per second.  
           [0012]    In accordance with another aspect of the present invention, a method of recording a gait of an ambulating subject is provided. The method includes locating the subject on a movable belt track. The subject is motivated to ambulate along the movable belt track at about the same rate as the movable belt track, while the belt track is moving, such that the location of the subject does not substantially change. Contact made by at least one limb of the subject with the belt track is recorded with a recording device underneath the belt track.  
           [0013]    In accordance with further aspects of the present invention, locating includes placing the subject within an enclosure hovering above the movable belt track. Motivating the subject includes initiating movement of the belt track while the subject is surrounded by an enclosure, such that the subject must ambulate to avoid collision with the enclosure. Recording includes utilizing at least one of a camcorder and a digital image capturing device to record contact made by the at least one limb of the subject with the belt track for a desired period of time. The belt track can be sufficiently transparent to enable viewing of the contact made by the at least one limb from underneath the belt track.  
           [0014]    In accordance with further aspects of the present invention, recording includes transferring ink from an ink reservoir underneath the belt track to a markable surface of the belt track upon each instance of the at least one limb of the subject applying pressure, through the belt track, to the ink reservoir.  
           [0015]    In accordance with further aspects of the present invention, the method further includes forwarding information relating to the contact made by the at least one limb to a computing apparatus supporting a software application for analyzing the gait of the subject based on the recorded contact. The method further includes reading the information to a data storage device. The method further includes converting the information to a standardized format. Recording can occur at a rate of at least about 60 frames per second. The method can further include identifying footprint image data from the contact made by at least one limb of the subject with the belt track. Extracting can include converting image data to binary and filtering out noise, leaving footprint image data. The method can also include calculating physiological information based on the footprint image data. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The present invention will become better understood with reference to the following description and accompanying drawings, wherein:  
         [0017]    [0017]FIG. 1 is a diagrammatic illustration of a locomotion monitoring apparatus, according to one aspect of the present invention;  
         [0018]    [0018]FIG. 2A is a top view of a portion of the apparatus of FIG. 1, according to one aspect of the present invention;  
         [0019]    [0019]FIG. 2B is a bottom view of a portion of the apparatus of FIG. 1, according to one aspect of the present invention;  
         [0020]    [0020]FIG. 3 is a flow chart illustrating a method of monitoring, according to one aspect of the present invention;  
         [0021]    [0021]FIG. 4A is a flow chart illustrating a method of image data capture;  
         [0022]    [0022]FIG. 4B is a flow chart illustrating a method of image data manipulation and analysis;  
         [0023]    [0023]FIG. 5 is a diagrammatic illustration of another embodiment of the locomotion monitoring apparatus, according to one aspect of the present invention; and  
         [0024]    [0024]FIG. 6 is a diagrammatic illustration of still another embodiment of the locomotion monitoring apparatus, according to one aspect of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0025]    An illustrative embodiment of the present invention relates to a locomotion monitoring apparatus for capturing the image of relatively large quantities of steps taken by animals, such as mice. The apparatus includes a motor-driven belt upon which the mouse is positioned. The belt can be substantially transparent or translucent. The motor drives the belt, and a partition, or other mechanism, motivates the mouse to ambulate to maintain approximately the same lateral position. An image capturing device captures and records the dynamic motion of the limbs of the mouse, and in particular the footprints, as the mouse ambulates on the belt. Because the belt is motor driven, the number of steps taken by the mouse and recorded by the monitoring apparatus is limited only by time spent on the belt and ability of the mouse to continue ambulating. For purposes of illustration, the small animal will be described and illustrated as a mouse. However, one of ordinary skill can appreciate that other animals can be monitored using the apparatus of the present invention. Further, the size of the animal monitored and the size of the apparatus can be scaled up or down, accordingly.  
         [0026]    [0026]FIGS. 1 through 6, wherein like parts are designated by like reference numerals throughout, illustrate example embodiments of an apparatus for monitoring locomotion kinematics in ambulating animals, according to the present invention. Although the present invention will be described with reference to the example embodiments illustrated in the figures, it should be understood that many alternative forms can embody the present invention. One of ordinary skill in the art will additionally appreciate different ways to alter the parameters of the embodiments disclosed, such as the size, shape, or type of elements or materials, in a manner still in keeping with the spirit and scope of the present invention.  
         [0027]    [0027]FIG. 1 shows an example embodiment of a locomotion monitoring apparatus  10 . The apparatus  10  includes a belt  12  that weaves between a plurality of rotating drums, cogs, or wheels  16 . The wheels  16  enable the belt  12  to move in a circumnavigating motion. The belt  12  is substantially transparent or translucent. A motor  14  couples to at least one of the wheels  16 , forming a driving wheel for providing the motion to the belt  12 . At least one mouse  18  can ambulate along the belt  12  as described herein.  
         [0028]    A number of different materials can be used to form the belt  12 . The resulting belt  12  must be pliable enough, and strong enough, to be repeatedly flexed as it travels through the wheels  16  while in motion. In addition, the belt  12  must be sufficiently transparent to permit a camera, or other image collection device, to see through the belt  12  from underneath to observe the ambulating animal, in accordance with one embodiment of the invention and as further discussed herein. Alternatively, the belt  12  must be sufficiently transparent to heat emissions, such that a heat sensing camera can see through the belt  12  to observe the ambulating animal.  
         [0029]    The motor  14  can be an electric motor. The motor  14  can further have a single speed, multiple speeds, or be infinitely variable. The different speeds made available by the motor  14  results in the motor  14  being able to move the belt  12  at different rates and urge the mouse to ambulate at different rates.  
         [0030]    An image collection device  28 , in accordance with one embodiment, is disposed beneath the belt  12 . The image collection device  28  can take the form of, for example, a camera, a video camera, a digital camera, a digital camcorder, a digital image capture device, and the like. The image collection device  28  can also take the form of an ink pad, touch pad, or other pressure sensing pad or technology, as will be discuss in a later embodiment herein.  
         [0031]    The image collection device  28  can capture the image of the mouse  18  ambulating along the moving belt  12  above. At least one light can aid in the capturing of the image. For example, a first light  20  can shine from above the mouse  18  to provide better contrast between the mouse  18  and the background. A second light  22  can shine from beneath the belt  12 , to highlight the feet of the mouse  18  as they make contact with the belt  12 . The position and use of the lights  20  and  22  can vary as situations dictate, and as understood by one of ordinary skill in the art.  
         [0032]    The mouse  18  is motivated to move as the belt  12  moves because a back partition  24  prevents the mousel  8  from being able to ride the belt  12  backwards. As the belt  12  moves the mouse  18  backwards, the mouse  18  eventually makes contact with the back partition  24 , which urges the mouse  18  to begin ambulating. A front partition  26  can be disposed in front of the mouse  18  to prevent the mouse  18  from running faster than the belt  12 , and running off of the front. In addition, the image collection device  28  can maximize the magnification of the image if the image collection device  28  is given a more limited span to view. By including the front partition  26 , this limits the mouse  18  to ambulate in the more limited span of between the back partition  24  and the front partition  26 .  
         [0033]    [0033]FIGS. 2A and 2B additionally show side walls  32  on either side of the mouse  18 . The side walls are not required, but can be helpful in preventing the mouse  18  from ambulating off the side of the belt  12  as the belt  12  is in motion.  
         [0034]    A computing apparatus  30  can communicate with the image collection device  28  and/or the motor  14 . Computing apparatus  30 , as used herein, refers to a programmable device that responds to a specific set of instructions in a well-defined manner and can execute a set of instructions. The computing apparatus can include one or more of a storage device, which enables the computing apparatus to store, at least temporarily, data, information, and programs (e.g., RAM or ROM); a mass storage device for substantially permanently storing data, information, and programs (e.g., disk drive or tape drive); an input device through which data and instructions enter the computing apparatus (e.g., keyboard, mouse, or stylus); an output device to display or produce results of computing actions (e.g., display screen, printer, or infrared, serial, or digital port); and a central processing unit including a processor for executing the specific set of instructions.  
         [0035]    A connection between the computing apparatus  30  and the image collection device  28  enables a user of the apparatus  10  to control the image collection device  28  in its acquisition of images of the ambulating mouse  18 . In addition, the connection enables the image collection device (for example, if it is a digital camera or digital camcorder) to transmit images of the ambulating mouse  18  to the computing apparatus  30  for analysis, as described later herein.  
         [0036]    [0036]FIGS. 2A and 2B illustrate a portion of the locomotion monitoring apparatus  10  from views above and below the apparatus  10 , respectively. As the belt  12  moves, the mouse  18  ambulates, surrounded on all four sides by the back partition  24 , front partition  26 , and side walls  32 . Again, the side walls  32  and front partition  24  are not requirements of the invention, they can however, aid in motivation of the mouse  18  to ambulate. As the mouse  18  ambulates, the feet or paws of the mouse  18  make contact with the belt  12 , which results in images of the underside of all or part of the feet in the form of footprints  34 . In the case of the relatively transparent belt  12 , the contact of the feet or paws with the belt  12  improves the view of the feet or paws relative to the other portions of the mouse  18 . FIG. 2B illustrates the view of the footprints  34  that result from the contact of the feet or paws with the belt  12 . Analysis of the footprints  34  can be performed, either manually or using the computing apparatus  30  and associated software, to analyze the locomotion kinematics of the mouse  18 , including gait.  
         [0037]    In operation as shown in FIG. 3, the teachings of the present invention enable the monitoring, measuring, and imaging of the gait and general locomotion kinematics of a small animal, such as a mouse. In accordance with one example embodiment, if not already on the belt  12 , the mouse  18  is placed on the belt  12  of the locomotion monitoring apparatus  10  (step  50 ). Each of the rear partition  24 , front partition  26 , and side walls  32 , if not already in position, can be inserted into position (step  52 ). For better illumination, an operator can turn on the first light  20  and/or the second light  22  (step  54 ). However, the lighting step is optional, based on environmental conditions. In addition, continual adjustments of the lighting can be made throughout the monitoring process.  
         [0038]    At some point during the process, the image collection device  28  must be activated to gather the footprints  34  of the mouse  18  (step  56 ). The operator initiates the belt  12  operation, causing the belt  12  to begin circumnavigation through the wheels  16  (step  58 ). One of ordinary skill will appreciate that the belt  12  need not circumnavigate, but could be spooled or stored at one end and fed through the wheels  16  to a destination location, without circumnavigation. In addition one of ordinary skill in the art can appreciate that the wheels  16  are shown to rotate such that the belt moves in the direction of arrow A, but that the direction of movement can be reversed.  
         [0039]    As the belt  12  begins to move, the mouse  18  moves toward the back partition  24  until the mouse  18  either beings ambulating or collides with the back partition  24 . If the mouse  18  does collide with the back partition  24 , there is a substantial motivation for the mouse to begin ambulating to correct the state of collision. Thus, the back partition  24  urges the mouse to ambulate while the belt  12  is moving. The image collection device  28  records the footprints  34  of the mouse  18  as the mouse  18  ambulates (step  60 ). The image collection device  28  can operate at a number of different recording speeds, however it has been found that using current technology, a rate of at least about 60 frames per second is preferable, and a rate of between about 60 frames per second and about 90 frames per second was found to be adequate. One of ordinary skill will appreciate that the recording rate can be adjusted to accommodate new recording technology, and different analysis processes. At some point after the collection of the footprints  34 , analysis occurs to determine the locomotion kinematics accordingly (step  62 ). The analysis need not take place in conjunction with the recording of the ambulating, nor within any specified amount of time following the recording of the ambulating. However, analysis can occur contemporaneous with, or subsequent to, recording of the ambulating images.  
         [0040]    The locomotion monitoring apparatus  10  captures images of mice from underneath as they are urged to ambulate upon, and counter to, the direction of a moving motor driven belt. Discrete images of portions of the feet of the animal as it ambulates, are spliced together, either physically or in digital format. The images generate a dynamic map of the articulation and timing of foot movement of the animal through an unlimited number of continuous strides not bounded by a walking track of finite length. The movement of the belt enables the image collection device  28  to remain stationary, thus avoiding distortion of the footprint image from the image collection device  28  either angling to capture a moving animal, or moving laterally to stay approximately beneath an animal as it ambulates. Thus, the locomotion monitoring apparatus  10  enables the acquisition of gait signals based on sequential steps of an ambulating animal as viewed from a fixed location.  
         [0041]    If desired, or if configured appropriately, the image collection device  28  can be operated or controlled by the operator inputting instructions into the computing apparatus  30  to guide the operation of the image collection device  28 . In addition, the image collection device  28  can transfer the footprints  34  to the computing apparatus  30  for analysis of the locomotion kinematics by the computing apparatus. Further, the computing apparatus  30  can convey instructions to the image collection device  28  to transmit or store the images accordingly.  
         [0042]    The computing apparatus  30  can include one or more software applications that can take gait image information from the image collection device  28  and analyze the image information to determine locomotion kinematics of the ambulating mouse  18 . FIG. 4A illustrates the taking of gait image formation, and subsequent data manipulation. The image collection device  28  captures the image of the mouse  18  ambulating on the belt  12  (step  100 ). The image collection device  28  can either directly transmit the image data to the computing apparatus  30  (step  102 ) or store the image data on a storage device, such as a video cassette or digital cassette (step  104 ). If stored on a cassette, the computing apparatus  30  must first identify the image data (step  106 ), and read the identified image data to a storage device associated with the computing apparatus  30  (step  108 ). The computing apparatus  30  can then convert the image data to a standardized format, such as AVI format (step  110 ).  
         [0043]    [0043]FIG. 4B illustrates the extraction of the images from the standardized AVI format to a JPG image. The computing apparatus  30  reads the desired AVI file and creates a Multi Matrix Mathematical Model of the AVI file (step  112 ). Image matrices are then extracted for each frame associated with the AVI file (step  114 ). Using a rule-based selection criterion, the mouse is identified from the image matrix (step  116 ). The computing apparatus  30  then names the image matrix with, for example, a sequential numbering system, and saves the image matrix as a JPG file (step  118 ).  
         [0044]    Once JPG (or other standardized format) files are created, the computing apparatus  30  can continue with the analysis. The computing apparatus  30  sequentially reads images into memory and creates a matrix representing all the red, green, and blue color components of each pixel of the image (step  120 ). A graphical interface is created for the user to refine a default criterion or to choose a new criterion, if desired, to identify mouse  18  paw color as seen in the image (step  122 ). The color image matrix is then converted to a binary equivalent, using the paw color as a base (step  124 ). The image data noise is identified and filtered based on size, shape, and positioning of the identified and probable paw like regions in the image (step  126 ). The particular paw of the four mouse paws is identified in each instance as left-front, right-front, left-rear, or right-rear, accordingly (step  128 ). The area of each paw or footprint  34  is then calculated, in addition to other desirable physiological information, such as X and Y coordinates of paw placement, bounding box, orientation, timing, and the like (step  130 ). The physiological information can be further analyzed to determine locomotion kinematics of the ambulating mouse  18 . The extracted information is then saved to a text base format, such as Microsoft Word® or Microsoft Excel® format (Word® and Excel® are produced by the Microsoft Corporation, Redmond, Wash.) for reporting purposes and further user analysis (step  132 ).  
         [0045]    [0045]FIG. 5 illustrates another example embodiment of a locomotion monitoring apparatus  10 ′ in accordance with the teachings of the present invention. The locomotion monitoring apparatus  10 ′ includes a number of same or similar elements as the embodiment depicted in FIG. 1, in addition to some variations. For example, the locomotion monitoring apparatus  10 ′ includes a paper belt  36  that weaves between the plurality of wheels  16 . The wheels enable the belt to move in a circumnavigating motion. The motor  14  couples to at least one of the wheels  16 , forming a driving wheel for providing the motion to the paper belt  36 . At least one mouse  18  can ambulate along the paper belt  36 .  
         [0046]    In the example embodiment, the paper belt  36  is formed of paper or a paper-like surface that can flex around the wheels  16  and is strong enough not to break, while also supporting a surface upon which ink or paint markings can be applied. One of ordinary skill will appreciate that the belt  12  need not circumnavigate, but could be spooled or stored at one end and fed through the wheels  16  to a destination location, without circumnavigation. This feature would be required if the operator desired a record of footprints longer than the circumnavigatory path of the paper through the wheels  16 . Otherwise, the footprints  34  of the mouse  18  would overlap as the paper belt  36  continued to run.  
         [0047]    The image collection device  28 , in accordance with the present embodiment, is disposed beneath the paper belt  36 . The image collection device  28  is in the form of a first pad  38 A and a second pad  38 B. The first pad  38 A and second pad  38 B can utilize different technologies, such as being an ink pad, or paint pad.  
         [0048]    The first pad  38 A and second pad  38 B capture the image of the mouse  18  ambulating along the moving paper belt  36  above. The mouse  18  is motivated to move as the paper belt  36  moves. As the mouse  18  ambulates, the weight of the mouse  18  on its feet or paws forces the paper belt  36  to make contact with the first pad  3   8 A and the second pad  38 B. As the paper belt  36  makes contact with the first pad  38 A and the second pad  38 B, ink or paint transfers from the first pad  38 A and the second pad  38 B to form the footprints  34  on the paper belt  36 . There is an area of no contact  40  between the locations of the feet or paws forming the footprints  34  where the paper belt  36  does not make contact with the first pad  38 A or the second pad  38 B. This prevents errant marks from forming on the paper belt  36 .  
         [0049]    Once a desired amount of footprints  34  are collected on the paper belt  36 , the paper belt  36  can be removed from the wheels  16  an analysis performed to determine locomotion kinematics of the mouse  18  based on the placement of the footprints  34 . The first pad  38 A, due to its more forward position, records the placement of the two front feet or paws, and the second pad  38 B records the placement of the two back feet or paws. To differentiate the footprints  34 , the first pad  38 A can contain ink or paint of a first color (e.g. red), and the second pad  38 B can contain ink or pain of a second color (e.g. blue). Thus the footprints  34  are more easily identified.  
         [0050]    The first pad  38 A and the second pad  38 B can also take the form of a touch pad, or other pressure sensing pad or technology. In such an instance, the belt can be the paper belt  36  or the previously described belt  12 , or even a belt with any variation of transparency, or no transparency. As the mouse ambulates, the feet or paws apply pressure at the footprints  34  to the first pad  38 A and the second pad  38 B. This pressure translates to an electronic signal received by the computing apparatus  30 . The computing apparatus  30  manipulates the electronic signal to depict the footprints  34  for analysis.  
         [0051]    [0051]FIG. 6 illustrates still another example embodiment in accordance with the teachings of the present invention. A locomotion monitoring apparatus  10 ″ is shown. As with previous embodiments, the belt  12  passes through the plurality of wheels  16 , and can be powered by the motor  14 . The present embodiment includes the image collection device  28  and an additional second image collection device  46 . In addition to the back partition  24  and front partition  26 , a middle partition  44  creates two areas for mice to occupy. Therefore, the first mouse  18  can be ambulating along the moving belt  12  while a second mouse  42  is also ambulating along the same belt  12  contemporaneously. One of ordinary skill in the art will appreciate that there can be a plurality of middle partitions between the front partition  26  and back partition  24  to create a plurality of areas in which mice can ambulate on the moving belt. The illustrated embodiment is merely an example showing how such partitioning can be executed.  
         [0052]    Numerous modifications and alternative embodiments of the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure may vary substantially without departing from the spirit of the present invention, and exclusive use of all modifications that come within the scope of the appended claims is reserved. It is intended that the present invention be limited only to the extent required by the appended claims and the applicable rules of law.