Abstract:
An apparatus, method and program storage device are provided for co-registration of multi-modal images in a three-dimensional environment, where the apparatus includes a source of excitation light, an electromagnetic-ray source disposed relative to the source of excitation light, an electromagnetic-ray transparent mirror having a first surface disposed towards the excitation light and a second surface disposed towards the electromagnetic-ray source, a target location disposed towards the first surface of the electromagnetic-ray transparent mirror for locating a target and receiving the excitation light and the electromagnetic rays, an electromagnetic-ray detector disposed on an opposite side of the target location relative to the electromagnetic-ray transparent mirror for detecting electromagnetic-rays transmitted through the target, a second electromagnetic-ray transparent mirror having a light-reflective surface disposed towards the target location, and a light detector disposed towards the light-reflective surface of the second electromagnetic-ray transparent mirror for detecting light from the target.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 60/460,086, filed Apr. 3, 2003 and entitled “System and Method for Real-Time Acquisition of Co-Registered X-Ray and Optical (Fluorescence, Coherent, Diffused or Transmission) Images”, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The present disclosure is directed towards systems and methods for acquiring co-registered X-ray and optical imagery. Medical image data, for example, is typically desired and/or obtained through various types of imaging modalities. 
     A co-pending U.S. patent application Ser. No. 10/001,552, entitled “System and Method for Highlighting a Scene Under Vision Guidance”, which is subject to the same duty of assignment as the present application, discloses a system and method for processing coordinates of a target point in a captured image of a real scene, and converting the image coordinates into the coordinates of a light projector to illuminate the target point. In addition, issued U.S. Pat. Nos. 6,227,704; 6,229,873; 6,447,163 and 6,473,489; which are also subject to the same duty of assignment as the present application, disclose systems and methods for acquisition of video and X-ray images. 
     What is needed is a new system and method for real-time acquisition of co-registered optical (e.g., fluorescence, coherent, diffused or transmission) and X-ray images. Such a system could provide physicians with new imaging abilities for applications including, for example, Arthritis treatment monitoring. For such an application, an optical image could show the enzyme activities, while a co-registered X-ray image could allow a physician to exactly locate the activity in relation to bone structure. In this way, a physician could take advantage of both imaging systems at the same time, by viewing the superimposed images, and thereby be relieved from having to relate the two types of images in his/her mind. The desired system could allow the physician to visualize each of the optical or X-ray images alone or in combination with a co-registered image. The present disclosure addresses these and other related issues. 
     SUMMARY 
     These and other drawbacks and disadvantages of the prior art are addressed by an apparatus, method and program storage device for co-registration of multi-modal images in a three-dimensional environment. 
     A first embodiment apparatus for co-registration of multi-modal images in a three-dimensional environment includes a source of excitation light, a one-way mirror having a transmissive side disposed towards the excitation light for transmitting the excitation light and a reflective side for reflecting light received from a target, an electromagnetic-ray source disposed relative to the source of excitation light, an electromagnetic-ray transparent mirror having a light-reflective surface disposed towards a reflecting side of the one-way mirror and an electromagnetic-ray transmissive surface disposed towards the electromagnetic-ray source, a target location disposed towards the light-reflective surface of the electromagnetic-ray transparent mirror for locating a target and receiving the excitation light and the electromagnetic-rays, an electromagnetic-ray detector disposed on an opposite side of the target location relative to the electromagnetic-ray source for detecting electromagnetic-rays transmitted through the target, and a light detector disposed towards the reflective side of the one-way mirror for detecting light from the target. 
     A second embodiment apparatus for co-registration of multi-modal images in a three-dimensional environment includes a source of excitation light, an electromagnetic-ray source disposed relative to the source of excitation light, an electromagnetic-ray transparent mirror having a first surface disposed towards the excitation light and a second surface disposed towards the electromagnetic-ray source, a target location disposed towards the first surface of the electromagnetic-ray transparent mirror for locating a target and receiving the excitation light and the electromagnetic rays, an electromagnetic-ray detector disposed on an opposite side of the target location relative to the electromagnetic-ray transparent mirror for detecting electromagnetic-rays transmitted through the target, a second electromagnetic-ray transparent mirror having a light-reflective surface disposed towards the target location, and a light detector disposed towards the light-reflective surface of the second electromagnetic-ray transparent mirror for detecting light from the target. 
     These and other aspects, features and advantages of the present disclosure will become apparent from the following description of exemplary embodiments, which is to be read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure teaches an apparatus and method for image segmentation in a three-dimensional environment, in accordance with the following exemplary figures, in which: 
         FIG. 1  shows a schematic diagram of an optical imaging system where the source of the excitation light and the optical camera detecting the emitted or reflected light have the same projection geometry; 
         FIG. 2  shows a schematic diagram of an optical imaging system where the source of the excitation light and the optical camera detecting the emitted or reflected light have the same projection geometry, and are each on the same side and attached side-by-side; 
         FIG. 3  shows a schematic diagram of a co-registered imaging system in accordance with an illustrative embodiment of the present disclosure where the excitation is done with a source of coherent light; 
         FIG. 4  shows a schematic diagram of a co-registered imaging system in accordance with an illustrative embodiment of the present disclosure where the detector of the transmitted light is positioned such that its images are co-registered with X-ray images; 
         FIG. 5  shows a schematic diagram of a co-registered imaging system in accordance with an illustrative embodiment of the present disclosure where the detector of the transmitted light is positioned such that its images are co-registered with X-ray images and the detector is attached to the side of the X-ray detector; and 
         FIG. 6  shows a schematic diagram of a co-registered imaging system in accordance with an illustrative embodiment of the present disclosure where the system is capable of rotating by at least 200 degrees around a patient. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present disclosure introduces a system and method for real-time acquisition of co-registered X-ray and optical images, including, for example, fluorescence, coherent, diffused or transmission images. System embodiments provide physicians with new imaging capabilities applicable to many applications, including, for example, Arthritis treatment monitoring. 
     In an Arthritis treatment monitoring example, the optical image shows the enzyme activities. The co-registered X-ray image allows the physician to precisely locate the enzyme activities in relation to the bone structure of the patient. In this way, the different types of images are superimposed so that the physician may take advantage of both imaging systems at the same time without the need to relate the two images manually. A preferred system embodiment permits the physician to visualize each of the optical or X-ray images alone, or combined into one co-registered image. 
     In the description that follows, an X-ray or X-ray fluoroscopy system is illustrated with its two main components: a) X-ray source; and b) X-ray detector. An optical imaging device is also illustrated by its two main components: a) source of excitation light; and b) detector of emitted, reflected, diffused or transmitted light. 
     As shown in  FIG. 1 , a first exemplary optical imaging system is indicated generally by the reference numeral  100 . The imaging system  100  includes a source of excitation light  110  projecting through a non-reflecting side of a one-way mirror  120  to a target  130 . The light emitted or reflected from the target  130  is reflected by a reflecting side of the one-way mirror to a detector of emitted or reflected light  140 . Thus, in the optical imaging system  100 , the source of the excitation light and the optical camera detecting the emitted or reflected light have the same projection geometry. 
     Turning to  FIG. 2 , a second exemplary optical imaging system is indicated generally by the reference numeral  200 . The imaging system  200  includes a source of excitation light  210  projecting through a non-reflecting side of a one-way mirror  220  to a target  230 . The light emitted or reflected from the target  230  is reflected by a reflecting side of the one-way mirror to a mirror  222 , which reflects the light to a detector of emitted or reflected light  240 . Thus, in the optical imaging system  200 , the source of the excitation light and the optical camera detecting the emitted or reflected light have the same projection geometry. In addition, the source and the detector are on the same side and can be attached side-by-side. 
     Turning now to  FIG. 3 , a first exemplary co-registered imaging system is indicated generally by the reference numeral  300 . The imaging system  300  includes a source of excitation light  310  projecting through a non-reflecting side of a one-way mirror  320  to a mirror  360 . The mirror  360  is an X-ray transparent mirror that reflects the light to a target  330 . The light emitted or reflected from the target  330  is reflected by the mirror  360  to a reflecting side of the one-way mirror  320 , which reflects the light to a detector of emitted or reflected light  340 . The imaging system  300  further includes an X-ray source  350  projecting through the X-ray transparent mirror  360  to the target  330 . An X-ray detector plate  370  receives the X-rays transmitted through the target  330 . 
     Thus, the resulting system  300  provides co-registered X-ray and emitted or reflected images. In a case where the excitation is done with a source of coherent light, the detector detects the reflected light. In a case of fluorescence imaging, the detector will detect the emitted light from the object. Note that different detectors and special filters may be used for each of the imaging systems described herein. 
     As shown in  FIG. 4 , a second exemplary co-registered imaging system is indicated generally by the reference numeral  400 . The imaging system  400  includes a source of excitation light  410  reflecting from a mirror  422 . The light reflected from the mirror  422  to a mirror  460 . The mirror  460  is an X-ray transparent mirror that reflects the light to a target  430 . The light transmitted through the target  430  is reflected by another X-ray transparent mirror  462 , which reflects the light to a detector of transmitted light  442 . The imaging system  400  further includes an X-ray source  450  projecting through the X-ray transparent mirror  460  to the target  430 . The light transmitted through the target  430  is further transmitted through the other X-ray transparent mirror  462 . An X-ray detector plate  470  receives the X-rays transmitted through the target  430  and the other X-ray transparent mirror  462 . Thus, in the system  400 , the detector of the transmitted light is positioned in a way that the images it provides are co-registered with X-ray images. 
     Turning to  FIG. 5 , a third exemplary co-registered imaging system is indicated generally by the reference numeral  500 . The imaging system  500  includes a source of excitation light  510  reflecting from a mirror  522 . The light reflected from the mirror  522  to a mirror  560 . The mirror  560  is an X-ray transparent mirror that reflects the light to a target  530 . The light transmitted through the target  530  is reflected by another X-ray transparent mirror  562 , which reflects the light to a detector of transmitted light  542 . The imaging system  500  further includes an X-ray source  550  projecting through the X-ray transparent mirror  560  to the target  530 . The light transmitted through the target  530  is further transmitted through the other X-ray transparent mirror  562  to another mirror  524 . An X-ray detector plate  570  receives the X-rays transmitted through the target  530 , the other X-ray transparent mirror  562  and the other mirror  524 . Thus, in the system  500 , the detector of the transmitted light is positioned in a way that the images it provides are co-registered with X-ray images, and this detector can be conveniently attached to the side of the X-ray detector. 
     Turning now to  FIG. 6 , a fourth exemplary co-registered imaging system is indicated generally by the reference numeral  600 . The imaging system  600  includes a source of excitation light  610  reflecting from a mirror  622 . The light reflected from the mirror  622  to a mirror  660 . The mirror  660  is an X-ray transparent mirror that reflects the light to a target  630 . The light transmitted through the target  630  is reflected by another X-ray transparent mirror  662 , which reflects the light to a detector of transmitted light  642 . The imaging system  600  further includes an X-ray source  650  projecting through the X-ray transparent mirror  660  to the target  630 . The light transmitted through the target  630  is further transmitted through the other X-ray transparent mirror  662  to another mirror  624 . An X-ray detector plate  670  receives the X-rays transmitted through the target  630 , the other X-ray transparent mirror  662  and the other mirror  624 . The entire system  600 , excluding the target  530 , is mounted to gimbals, tracks or like devices for rotating about the centrally disposed target  530 . 
     Thus, in a particularly preferred embodiment, the co-registered X-ray and Transmitted Optical Imaging system  600  rotates around the target or patient by at least 200 degrees, while acquiring X-ray and transmitted optical images. These images are then used for tomographic reconstruction. The two sets of resulting reconstructed 3D data are thus fully co-registered by design. This allows the physician to visualize the data as two separate data sets or one composite data set. 
     According to one aspect of the present disclosure, the image capture device and the illumination device comprise common optical properties. This may be realized by means of one one-way mirror.  FIG. 1  provides an exemplary construction of such a system.  FIG. 2  provides a second exemplary construction where the source and the detector can be attached side-by-side using an additional mirror. 
     In another aspect of this present disclosure, the system allows the acquisition of real-time X-ray and fluorescence or coherent optical imaging.  FIG. 3 , illustrates an exemplary construction of such a system. The system allows the user to choose a target to be illuminated in a real scene using X-ray image data of the same scene. 
     In one aspect, a method for illuminating a target point in a real scene comprises the steps of capturing X-ray image data of a scene, identifying X-ray image data associated with a target point, and projecting a light beam at the target point in the rear scene. The step of projecting comprises the steps of converting image coordinates of the target point to light coordinates for directing the light beam, and processing the light coordinates to direct the light beam to the target point in the real scene. 
     The illumination system and its control for embodiments of the present disclosure may be realized as described in the co-pending U.S. patent application Ser. No. 10/001,552, entitled “System and Method for Highlighting a Scene Under Vision Guidance”. A difference here is that the system can also be guided by X-ray vision in cases where the target for illumination can be better defined in respect to the anatomical targets visible under X-rays. Once the target is illuminated, the reflected or the emitted light, in the case of fluorescence imaging, is captured by an optical sensor with the same imaging geometry as the X-ray imaging system. This allows the user, such as a physician, to see a composite image, which includes both information from X-ray and optical imaging. Such system embodiments can provide new imaging possibilities, which can play an important role in improving the diagnosis and treatment monitoring procedures for many diseases. 
       FIGS. 4 and 5  illustrate two other aspects of the present disclosure. In these cases the system co-registers the X-ray and transmitted optical imaging. The Transmitted Optical Imaging here is defined as a system composed of a light source, which emits the light rays towards an object of interest and a detector on the other side of the target, which measures the intensity of the transmitted light. This intensity is a function of the absorption of the tissues and/or material forming the object (for example see “Imaging through Random Media Using Low Coherence Optical Heterodyning” by A. Schmidt, R. Cotey, and P. Saulnier, Optics Letters, Volume 20, Number 4, Feb. 15, 1995). System embodiments of the present disclosure can use two, three or four mirrors, for example, depending on the choice of having the light source and transmitted light optical detector on the side, or orthogonal to, the X-ray source and detector, respectively. 
     According to another aspect of this present disclosure, the co-registered X-ray and Transmitted Optical Imaging system rotates around the patient or animal target by at least 200 degrees, while acquiring both X-ray and optical images. These images can then be used for tomographic reconstruction. The two sets of resulting reconstructed 3D data are thus fully co-registered. This allows the physician to visualize the data as two separate or one composite data set. The calibration and reconstruction from rotating C-arms have been extensively discussed in the literature. For example, the following U.S. patents propose different methods for calibration and tomographic reconstruction using such system: U.S. Pat. No. 6,049,582; U.S. Pat. No. 6,038,282; U.S. Pat. No. 5,963,613; U.S. Pat. No. 5,963,612; U.S. Pat. No. 5,923,727; U.S. Pat. No. 5,835,563 and U.S. Pat. No. 5,822,396. In preferred embodiments of the present disclosure, a particularly advantageous feature is in the co-registration of the X-ray and Transmitted Optical Imaging systems by the particular construction and calibration of this system. This allows obtaining co-registered 3D reconstruction data from these two modalities. 
     The relative placement of the elements of embodiments of the present disclosure are important. The X-ray imaging system, the optical imaging system, and the mirrors need to be placed correctly, as will be understood by those of ordinary skill in the pertinent art. There is also a feature for computing a transformation, taking into account the differences in the intrinsic imaging parameters of the X-ray and Optical images. These geometrical and imaging calibrations can be considered as modifications and improvements of those described in U.S. Pat. Nos. 6,473,489; 6,447,163; 6,229,873 and 6,227,704, for example. 
     These and other features and advantages of the present disclosure may be readily ascertained by one of ordinary skill in the pertinent art based on the teachings herein. It is to be understood that the teachings of the present disclosure may be implemented in various forms of hardware, software, firmware, special purpose processors, or combinations thereof. 
     Most preferably, the teachings of the present disclosure are implemented as a combination of hardware and software. Moreover, the software is preferably implemented as an application program tangibly embodied on a program storage unit. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (“CPU”), a random access memory (“RAM”), and input/output (“I/O”) interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the application program, or any combination thereof, which may be executed by a CPU. In addition, various other peripheral units may be connected to the computer platform such as an additional data storage unit and a printing unit. 
     It is to be further understood that, because some of the constituent system components and methods depicted in the accompanying drawings are preferably implemented in software, the actual connections between the system components or the process function blocks may differ depending upon the manner in which embodiments of the present disclosure are programmed. Given the teachings herein, one of ordinary skill in the pertinent art will be able to contemplate these and similar implementations or configurations of the present disclosure. 
     Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present disclosure is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present disclosure. All such changes and modifications are intended to be included within the scope of the invention as set forth in the appended claims.