Abstract:
A device and method for verifying positional alignment between a visible light beam and an x-ray beam by providing a radio-opaque body that is to be positioned in the center of the visible light beam in the x-ray field. The image of the radio-opaque body provides an indication of whether the position of the visible light beam is colinear and coincident with the central ray of the x-ray beam of an imaging system.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     Applicants hereby claim priority on earlier filed provisional application Ser. No. 60/081,396, filed Apr. 10, 1998, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to the field of aligning an x-ray and a visible light beam in a fluoroscope. More particularly, the invention relates to a device containing a radio-opaque material that provides a means to check for precise physical alignment between an x-ray in a fluoroscope and a laser beam in a laser targeting system attached to the fluoroscope. 
     2. Background Art 
     Producing and positioning a laser beam that indicates the exact surface point of entry and the precise angle of approach to a subcutaneous structure can be used in many fluoroscopically guided procedures, such as biopsies of deep tissue anatomy, screw, wire and implant placement, vertebroplasty, spinal procedures, arthrograms, selected interventional cardiology, and craniofacial and plastic surgery procedures. In these procedures the laser or other visible light beam usually serves as an accurate visible guide for accessing a subcutaneous structure. Thus, in order to correlate the position of a subcutaneous structure in an x-ray image and the point and direction of entry of a medical instrument on the skin of a patient, it is necessary to achieve the most accurate alignment of an x-ray beam with a visible light beam in a fluoroscopic machine. 
     The use of a visible light system together with an imaging system to mark or indicate areas of medical interest has been known in the art. For example, U.S. Pat. No. 5,031,203 to Trecha and U.S. Pat. No. 4,117,337 to Staats describe an arrangement where a patient is moved within an imaging system to a predetermined location of a laser system. A method and device for aligning x-rays and a laser beam by aligning x-rays and the bore of a cylindrical device are disclosed in U.S. Pat. No. 4,356,400 to Polizzi et al. A device for aligning a patient at the proper distance from an x-ray source by intersecting two laser beams at a predetermined position is described in British Patent No. GB 2175778A published Dec. 3, 1986. None of these patents discloses a device and method for verifying and perfecting coaxial and coincident alignment between an x-ray and a visible light beam by verifying and correcting alignment of the visible light beam within the source of the visible light beam. 
     U.S. Pat. Nos. 5,212,720 and 5,644,616 to Landi et al. disclose a technique that uses a calibration device with a marking made of radio-opaque material for coaxially and coincidentally aligning a laser beam with the central ray from an x-ray source. 
     The techniques of using a radio-opaque material as a marker to mark or encircle a particular area on an x-ray image has been known in the past. For example, U.S. Pat. No. 5,193,106 to DeSena discloses a device for providing percutaneous-based markings in association with x-ray examination procedures. The DeSena patent shows a tape having adhesive backing with a radio-opaque marker made of radio-opaque material affixed to the tape. The radio-opaque marker encloses an area of interest and serves to focus the attention of a podiatrist reviewing an x-ray photograph of the area of interest. U.S. Pat No. 5,565,678 to Manian discloses a system and methods for performing a quantative assessment of the image quality of a radiographic image. A calibration target comprising a stack of circular disks for attenuating an incident beam is employed to form a latent image and ultimately a visible radiographic image to which an examination target may be compared. U.S. Pat. No. 4,698,836 to Minasian discloses a radio-opaque movable ball disposed within a dish shaped opening. The ball is used to record position information on a patient&#39;s x-ray film. None of these patents uses a radio-opaque member to verify alignment between an x-ray and a visible light beam in a fluoroscope or any other kind of x-ray equipment. Moreover, none of these patents discloses a method and device for verifying alignment of the visible light beam in the light beam source itself. 
     The system of aligning an x-ray beam with a visible light beam disclosed in the Landi et al. patents comprises a visible light source with a colinearizer that are attached to an x-ray machine such as a fluoroscope. The colinearizer includes a pair of reticles mounted at each end of the colinearizer. Each reticle has radio-opaque cross-hairs that produce an image of the reticles on a x-ray image. By observing the relative position of the two pairs of cross-hairs on the x-ray image a surgeon or a bio-engineering technician can make a conclusion about the proper alignment of the visible light beam and the central ray of the x-ray beam. Such system and method, however, do not take into account the fact that the visible light beam may deflect from its intended direction inside the colinearizer when, for example, the fluoroscope is moved or when the visible light source is somehow disturbed. In the Landi et al. systems and methods the alignment of the two reticles in the colinearizer with respect to the x-ray does not solve the problem of verifying the alignment of the visible light beam inside the visible light beam source itself. The Landi et al. systems and methods presume that if the colinearizer is aligned with the x-ray beam, the visible light beam will necessarily always be properly aligned with the x-ray. That is not always so, because during the exploit of the x-ray machine the initial alignment between the reticles in the colinearizer and the visible light beam may get lost. Such loss of an alignment will inevitably cause imprecise identification of the point and direction of entry to subcutaneous structures in a patient during a medical procedure. 
     If a doctor could verify the alignment between the visible light beam and the x-ray as well as between the visible light beam and the source of the visible light beam itself and then print out an image corresponding to the correctly aligned equipment, the doctor would have proof of the fact that he or she operated properly functioning, precisely aligned equipment. Therefore, it would be desirable to have a device and method for verifying alignment of the direction of the visible light beam with respect to the colinearizer in addition to the alignment with respect to the direction of the central ray of the x-ray beam. 
     SUMMARY OF THE INVENTION 
     It is, therefore, a primary object of the present invention to provide a new and improved method for determining positional alignment of a visible light beam in a fluoroscopic x-ray system. 
     It is also an object of the present invention to provide a device and method for physically verifying the position of a visible light beam in the x-ray field of an x-ray machine. 
     In the alignment verification device and method of the present invention a body of radio-opaque material is incorporated into a supporting member coated or covered with an adhesive. The device can be removably attached to an image intensifier of an x-ray machine which both the x-rays and the visible light beam impinge upon. Once the general alignment between the visible light beam and the x-rays is achieved, the two reticle images will form a single superimposed reticle image on a monitor. After that the alignment verification device is placed on the image intensifier so that the visible light beam and the radio-opaque body are in direct alignment. In such an arrangement the position of the radio-opaque material indicates the place where the visible light beam hits the image intensifier. When later the visible light beam is turned off, the position of the image of the radio-opaque body in an x-ray image relative to the center of the reticle image will indicate the position of the visible light beam relative to the colinearizer, and therefore, to the x-rays. In the case of misalignment between the visible light beam and the x-rays, the visible light beam is realigned with the colinearizer and the alignment verification procedure is repeated. 
     These and other objects and advantages of the present invention will become increasingly more apparent to those skilled in the art by reference to the following description and to the accompanied drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1 is a schematic representation of non-aligned visible light beam and x-rays in an x-ray machine. 
     FIG. 2 is a schematic representation of aligned visible light beam and x-rays in an x-ray machine. 
     FIG. 3A is a schematic representation of non-aligned colinearizer and x-rays. 
     FIG. 3B is an image formed by cross-hairs of two reticles when the colinearizer is not aligned with the x-rays. 
     FIG. 3C is a schematic representation of aligned colinearizer and x-rays. 
     FIG. 3D is a superimposed image formed by cross-hairs of two reticles when the colinearizer is aligned with the x-rays. 
     FIG. 4 is a schematic representation of misalignment between a visible light beam and a colinearizer. 
     FIG. 5A is a top view of an alignment verification device of the present invention. 
     FIG. 5B is a side view of the alignment verification device of the present invention. 
     FIG. 5C is a perspective view of the alignment verification device with a peel-off covering. 
     FIG. 6 is a schematic representation of an x-ray machine as used with the alignment verification device. 
     FIG. 7A is a representation of an image corresponding to precise alignment between a visible light beam and x-rays. 
     FIG. 7B is a representation of an image corresponding to misalignment between the visible light beam and the x-rays. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the preferred embodiment the device and method of the present invention are used with C-Arm fluoroscope machines, such as the ones manufactured by OEC, Siemens, General Electric, Phillips, Toshiba and others. A system comprising a visible light source attaches to the fluoroscope. An example of a system with a visible light source suitable for use with a C-Arm fluoroscope is the Dual Radiation Targeting System (DRTS™) platform described in U.S. Pat. Nos. 5,212,720 and 5,644,616 to Landi et al., which patents are incorporated herein by reference. 
     As illustrated in FIG. 1, in an x-ray/visible light beam imaging system x-rays  10  exit an x-ray source  12  of a fluoroscope in a conical array. As the x-rays pass through a target  14 , they form an image  16  of target  14  on a monitor  18 . A visible light source  20  that is attached to the fluoroscope generates a visible light beam  22 . As shown in FIG. 1, visible light beam  22  and a central x-ray  24  are coaxially and coincidentally unaligned. Because beam  22  and central x-ray  24  are unaligned, point A 1  of image  16  on monitor  18  appears to be the point of entry at which beam  22  impinges upon image  16 . However, point A of target  14  that corresponds to point A 1  of image  16  is not the point of entry of beam  22 , as illustrated in FIG.  1 . Therefore, when beam  22  and central x-ray  24  are unaligned, the information of the relative positions of target  14  and beam  22  provided by image  16  is incorrect. If beam  22  and central x-ray  24  are coaxially and coincidentally aligned, as illustrated in FIG. 2, then the point of entry B on target  14  correctly corresponds to the point of entry B 1  on image  16  formed on monitor  18 . In order to coaxially and coincidentally align beam  22  and central x-ray  24  the DRTS™ platform utilizes a visible light source  20  that generates visible light beam  22  along a central axis Z of a colinearizer  26 , as shown in FIG. 3A. A pair of reticles  28  and  30  are inserted at each end of colinearizer  26 . Each reticle has radio-opaque cross-hairs  32  and  34  marked on the reticles. When axis Z of colinearizer  26  is not aligned with central x-ray  24  of the array of x-rays  10 , radio-opaque cross-hairs  32  and  34  will produce two separate unaligned reticle images  36  and  38  on monitor  18 , as illustrated in FIG.  3 B. Therefore visible light beam  22  is also unaligned with central x-ray  24 . However, when axis Z of colinearizer  26  is colinear with central x-ray  24  of the array of x-rays  10 , as shown in FIG. 3C, the images of two radio-opaque cross-hairs will superimpose, forming a single reticle image  40  on monitor  18 , as illustrated in FIG.  3 D. Therefore, when a surgeon or a medical technician observes two reticle images on monitor  18 , he or she will be able to correct the position of visible light beam source  12  so that the two images superimpose and form a single reticle image  40 . 
     The above-described alignment mechanism provides correct alignment only when the direction of visible light beam  22  coincides with the direction of axis Z of colinearizer  26 . If for any reason the direction of visible light beam  22  is not coaxial with axis Z of colinearizer  26 , then a single reticle image  40  of superimposed radio-opaque cross-hairs will not be indicative of visible light beam  22  being coaxially aligned with central x-ray  24 , as shown in FIG.  4 . Indeed, as illustrated in FIG. 4, axis Z of colinearizer  26  and central x-ray  24  are coaxial, but visible light beam  22  is not coaxial with central x-ray  24  even thought a single superimposed image  40  of two reticles will indicate, falsely in this case, proper alignment between visible light beam  22  and central x-ray  24 . 
     The alignment verification device of the present invention is used to check the accuracy of the actual alignment between visible light beam  22  and central x-ray  24 . One of the embodiments of the alignment verification device of the present invention is illustrated in FIG.  5 A. The embodiment shows a device  50  comprising a supporting member  52  capable of attaching device  50  to a surface that is impinged upon by visible light beam  22  (not shown). In the preferred embodiment of the present invention supporting member  52  is in the form of a strip, a part  54  of which is covered by an adhesive for attaching member  52  to an x-ray machine. In the preferred embodiment strip  52  can be made of a transparent plastic material. Additionally, the preferred embodiment contemplates that part  54  which is covered or coated with the adhesive is also covered by a removable peel-off covering  58 , as illustrated in FIG.  5 C. 
     Supporting member  52  incorporates into it a three-dimensional radio-opaque body  56  which is permanently attached to supporting member  52 . In the preferred embodiment of the present invention three-dimensional radio-opaque body  56  is a spherically shaped member made of lead located in the center of a strip-like supporting member  52 , as illustrated in FIGS. 5A,  5 B and  5 C. It is contemplated by the present invention that three-dimensional radio-opaque body  56  can be made of any radio-opaque material. The diameter of the spherically shaped member preferably is within the range of 0.5 mm to 2 mm. Strip-like supporting member  52  is preferably from 2 cm to 20 cm long and from 0.5 cm to 5 cm wide. It is also preferable that part  54  comprises a plurality of circles ( 51  and  53  in FIG. 5A) that help a person to align visible light beam  22  and radio-opaque body  56 . Furthermore, the preferred embodiment of the present invention calls for the diameter of the spherically shaped member to be comparable to the cross-section of visible light beam  22  to facilitate a person aligning light beam  22  with body  56 . 
     Alignment verification device  50  of the present invention calls for the following procedure of achieving verification of alignment of visible light beam  22  from visible light beam source  20  and central x-ray  24 , as shown in FIG.  6 . With conical array of x-ray  10  turned on in an x-ray machine  60 , visible light beam  22  is aligned with central x-ray  24  by aligning colinearizer  26  and central x-ray  24  using reticles  28  and  30  to obtain a single superimposed reticle image like image  40 , as described above in connection with FIGS. 3C and 3D. Once colinearizer  26  and central x-ray  24  are in alignment, x-ray  10  is turned off and visible light beam  22  is turned on. After that alignment verification device  50  of the present invention is attached to image intensifier  62  of x-ray machine  60  so that three-dimensional radio-opaque member  56  is in direct alignment with visible light beam  22 , as illustrated in FIG.  6 . 
     With x-ray  10  turned on again and visible light beam  22  off, a user then observes a position of an image  70  of three-dimensional radio-opaque member  56  in an x-ray image on monitor  18  relative to the center of aligned superimposed reticles  40 , as illustrated in FIGS. 7A and 7B. If image  70  coincides with the intersection of radio-opaque cross-hairs of aligned superimposed reticles  40  on monitor  18 , as shown in FIG. 7A, it means that visible light beam  22  and central x-ray  24  are indeed in alignment. If, on the other hand, image  70  does not fall in the intersection of aligned superimposed reticles  40 , as illustrated in FIG. 7B, it means that visible light beam  22  and colinearizer  26  are misaligned and that actual alignment between visible light beam  22  and central x-ray  24  has not been achieved. In that case directions of visible light beam  22  and central x-ray  24  are adjusted relative to each other and their alignment is verified again in accordance with the method of the present invention described above. 
     It should be noted that even though the visible light beam described above can be any collimated visible light beam, in the preferred embodiment of the present invention the visible light beam is a laser beam. 
     It is appreciated that various modifications to the inventive concept described herein may be apparent to those of ordinary skill in the art without departing from the spirit and scope of the present invention as defined by the appended claims.