Patent Publication Number: US-2015073433-A1

Title: MR Compatible Fluorescence Viewing Device for Use in the Bore of an MR Magnet

Description:
This application is a continuation of application Ser. No. 13/040,037 filed Mar. 3 2011 which is a continuation in part of application Ser. No. 13/012,164 filed Jan. 24 2011. 
    
    
     This invention relates to an MR compatible stereoscopic viewing device for use in the bore of a magnet and to its cooperation with MR images and with a robot surgical system. The system may be used to generate combined fluorescence and MR images for improved surgery guidance in the resection of tumors. 
     BACKGROUND OF THE INVENTION 
     In U.S. Pat. No. 7,155,316 (Sutherland) issued Dec. 26 2006 is disclosed a system for Robotic microsurgery within the bore of an MR scanner. The disclosure of this patent is incorporated herein by reference or should be referred to for further details of the MR and robotic surgery system with which the present invention is concerned. 
     The above patent discloses a microsurgical robot system which is intended for use with an MR imaging system where the imaging magnet is retracted during the operating procedure since the system cannot function within the bore of the magnet. A disclosure of procedures within the bore is shown but this is limited to stereotactic procedures using one arm only and is limited by the fact that the microscope disclosed is not suitable for use within the bore thus precluding effective microsurgery. 
     That is the microsurgery is limited by the availability of a MR compatible stereoscopic microscope device with interactive high resolution to view the surgical site. In addition, line-of-sight issues exist in the following configuration: patient in the bore of the magnet; in-bore microscope surveying the surgical site; in-bore robotic arms between the surgical site and operating on the patient; other in-bore devices (camera, lights, HFD, etc). These line-of-sight issues may exist regardless of whether the surgeon is located in the OR or the control room. Therefore, the microscope needs to be compact and flexible for positioning. Sufficient lighting must also be available. 
     In addition, MR compatible microscopes are not available to allow fluorescence capabilities for viewing tumor boundaries. 
     The ability to combine MRI (for internal soft-tissue characterization) and microscopy (for high resolution dissection) and fluorescent microscopy (for enhanced tumor boundaries) along with an in-bore surgical robot is a powerful integration of technologies for neurosurgery. 
     Fluorescence imaging in neurosurgery has a long historical development, with various biomarkers and biochemical agents being used, and numerous technological approaches. This review focuses on contrast agents, summarizing endogenous fluorescence, exogenously stimulated fluorescence, and exogenous contrast agents, and then on tools used for imaging. It ends with a summary of key clinical trials that lead to consensus studies. The practical utility of protoporphyrin IX (PpIX) as stimulated by administration of δ-aminolevulinic acid has had substantial pilot clinical studies and basic science research completed. Recently, multi-center clinical trials using PpIX fluorescence to guide resection have shown efficacy for improved short-term survival. Exogenous agents are being developed and tested pre-clinically, and hopefully hold the potential for long-term survival benefit if they provide additional capabilities for resection of micro-invasive disease or certain tumor subtypes that do not produce PpIX or help delineate low-grade tumors. The range of technologies used for measurement and imaging varies widely, with most clinical trials being carried out with either point probes or modified surgical microscopes. Currently, optimized probe approaches are showing efficacy in clinical trials, and fully commercialized imaging systems are emerging, which will clearly help to lead adoption into neurosurgical practice. 
     In a randomized phase ill multi-center clinical trial using ALA-induced PpIX fluorescence as the tumor tissue contrast agent for neurosurgical guidance, tumor tissue was more completely resected and 6-month progression-free survival was extended. 
     Clinical use of microscopy has been largely limited to research trials, where mechanistic information is sought about the origins of uptake or localization. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention there is provided an apparatus for viewing a part of a patient in which a fluorescent agent is applied to the patient so as to distinguish between tumor cells which take up the agent from non-tumor cells which do not take up the agent, the apparatus comprising: 
     an optical assembly for receiving light from the part of the patient including visible light and fluorescent light emitted from the fluorescing cells within the part of the patient; 
     a control system for generating from the light received a visual image of the part and including thereon the fluorescent light; 
     a display for viewing of the visual images generated from the light received from the part, the display including the fluorescent light; 
     a mount arranged to locate the optical assembly within a bore of an MRI magnet; 
     wherein the optical assembly, control system and the communication arrangement are compatible with the MRI magnet so as to allow simultaneous communication and MR imaging; and 
     wherein the MRI system is arranged to generate MR images and wherein the control system is arranged to cooperate with a control system of the MRI in order to overlay the MR images on the visual images including the fluorescent light on the display. 
     Preferably the fluorescence is analyzed quantitatively such that the quantitative measurement of the fluorescence is a measure of the concentration of tumor cells. 
     Preferably the MR imaging is used in conjunction with the quantitative measurement of the fluorescence to provides a more complete picture of the amount of tumor cells present. 
     Preferably the MR images which are co-registered with the fluorescent images are involved in the segmentation to provide tumor cell zones and also keep out zones related to eloquent and sensitive brain structures. 
     Preferably the imaging rate for the fluorescence imaging is of the order of 30 frames per second so it allows the resection to be monitored as it occurs. 
     Preferably the MR imaging is carried out including diffusion tensor imaging which shows on the image all the fiber tracks in the brain and of particularly importance, those around the tumor. 
     Preferably the fluorescent agent also contains MRI markers so that the cells appear on both the MR images and the fluorescence images. 
     Preferably there is provided a fluorescence delivery system for delivering the fluorescence agent to the patient and wherein the control system is arranged to determine when more fluorescence is required and to automatically activate the delivery system in response to this detection. 
     Preferably the apparatus is used with a surgical robot system including at least one robotic arm with at least one end effector for operating one or more surgical tools. However the system can be used where surgery is effected manually outside the magnet. 
     In this case, preferably the optical assembly is mounted on the robotic arm or the tool so as to be moveable therewith. In this case, preferably the control system is arranged to provide automatic orientation correction of the arm or tool mounted vision system&#39;s 3D scene visual output by incorporating information relating to the orientation of the tool and by adjusting the visual image data using this information. 
     Preferably there is provided in the bore a surgical illumination system for illuminating the part of the patient and wherein the system is arranged to automatically change the illumination based on one or more of the position and orientation of the robot arm, operating parameters of the optical assembly and operating parameters of the MRI. 
     Preferably the image representing the residual tumor mass is segmented and the data transferred to the robot which is used to resect the tumor to the level assigned by the quantitative analysis of the fluorescent images. 
     Preferably the robot is programmed to stop as each MRI image is recorded. 
     According to a second aspect of the invention there is provided an apparatus comprising: 
     an MRI system including an MRI magnet having a cylindrical bore; 
     an optical assembly for receiving light from the part of the patient, the optical assembly including stereoscopic viewing components arranged for use in generating 2D and 3D images, the optical assembly being adjustable to change at least a field of view; 
     a display for viewing of images generated from the light received from the part; 
     and a control system for controlling the optical assembly and for generating the images; 
     a communication arrangement for communicating between the optical assembly and the processing system; 
     a mount arranged to locate the optical assembly within the bore of the MRI magnet; 
     the optical assembly, control system and the communication arrangement being compatible with the MRI magnet so as to allow simultaneous communication and MR imaging; 
     and a surgical robot system including at least one robotic arm with at least one end effector for operating one or more surgical tools within the bore. 
     Preferably the control system is arranged to provide automatic orientation correction of the image as displayed by incorporating information relating to the orientation of the tool and by adjusting the visual image data using this information. 
     Preferably there is provided in the bore a surgical illumination system for illuminating the part of the patient and wherein the control system is arranged to automatically change the illumination based one or more of the position of the tool, operating parameters of the optical assembly and operating parameters of the MRI. 
     According to a third aspect of the invention there is provided an apparatus for viewing a part of a patient in which a fluorescent agent is applied to the patient so as to distinguish between tumor cells which take up the agent from non-tumor cells which do not take up the agent, the apparatus comprising: 
     an optical assembly for receiving light from the part of the patient including visible light and fluorescent light emitted from the fluorescing cells within the part of the patient; 
     a control system for generating from the light received a visual image of the part and including thereon the fluorescent light; 
     a display for viewing of the visual images generated from the light received from the part, the display including the fluorescent light; 
     a fluorescence delivery system for delivering a fluorescence agent to the patient; 
     wherein the control system is arranged to quantitatively analyze the fluorescence and to determine therefrom when more fluorescence is required and to automatically activate the delivery system in response to this detection. 
     Preferably the control system is arranged to change the viewing parameters of the optical assembly including one or more of zoom, depth of field, focus, pan, tilt, window levelling, color, balance, magnification. 
     Preferably an illumination source is integrated into the optical assembly to illuminate viewing of the part. 
     Preferably there is provided an imaging/encoding device or CCD for encoding light from the optical assembly from the part into digital information. 
     In one arrangement, the imaging/encoding device is located near the patient in the bore of a magnet at the optical assembly and the control system is located outside of the bore with communication therebetween using wires for communication the electrical signals carrying the image data. 
     In another arrangement, the imaging/encoding device is located remotely from the optical assembly and the communication arrangement comprises a fiber optic system. 
     In yet another arrangement, the imaging/encoding device is located remotely from the optical assembly and the communication arrangement comprises a light tube movable with the optical assembly. 
     Preferably the display is a remote display outside the bore so that the microsurgery is carried out by a surgeon at a remote operating location using robotic control of the effectors. 
     Preferably the display provides a visual real-time update of the surgical site and is combined with a real-time overlay of MR images for the real-time update of the stereoscopic display. That is the images from the MR system are registered with the visual images and overlaid to be viewed simultaneously by the surgeon. 
     In another arrangement, the display comprises a head mounted display for mounting on the surgeon. 
     In a yet further arrangement, the display is a traditional binocular setup or a stereoscopic 3D display. That is a conventional microscope type located at the bore for direct viewing of the site. 
     Preferably the optical assembly is sterilizable using conventional techniques. 
     Preferably the optical assembly, control system and the communication arrangement are made compatible with the MRI magnet by one or more of: 
     an RF filter on electrical communication cables to prevent stray RF from the electrical communication cables signals from effecting the imaging; 
     an RF filter on electrical communication cables to prevent the RF imaging signals from affecting the imaging/encoding device; 
     an RF enclosure around the optical assembly and the imaging/encoding device; 
     the optical assembly and imaging/encoding device being formed of materials which are compatible with the magnetic field; 
     cable traps on electrical communication cables to prevent heating thereof in the RF field of the imaging system; 
     a magnetic shield around or adjacent the components to prevent the magnetic field from affecting the components. 
     In one arrangement the optical assembly is mounted by the mount to the bore. 
     In another arrangement the optical assembly is mounted by the mount on an arm extending into the bore. 
     Preferably the apparatus is used with a surgical robot system including at least one robotic arm with at least one end effector for operating one or more surgical tools. 
     In this arrangement the optical assembly can be mounted on the robotic arm so as to be moveable therewith, that is the optical assembly is mounted on the robotic arm so as to movable with the tool and so as to have a field of view including a tip of the tool. 
     Mounting the optical assembly to the end effector or tool provides the surgeon with a view that is always inline with the surgical site and area that is being operated on. The problem with doing this is that the camera view moves with the tool or end effector and this changes the orientation of the 3D view. Changing the orientation of the view means that the surgeon would lose their sense of where the tool or arm is in relation to the real world. For example if the tool or arm is rotated by 90 degrees, the left hand side of the 3D view would now be pointing straight up and anything which is brought in to the field of view from the left would be displayed as it is coming from the top of the view. 
     Automatic orientation correction of the arm or tool mounted vision system&#39;s 3D scene visual output can be provided in the software controlling the image as displayed by incorporating information relating to the orientation of the tool and therefore the optical assembly into the software and by adjusting the visual image data using this information. That is, if the system acts to rotate the vision system then the 3D output view on the monitor would also be rotated and now what was left is could now be top or bottom (for example) The solution is to manipulate the visual information digitally (i.e. rotate the data) with the orientation information for the robot end effector and/or tool. The orientation information can be obtained from the tool manipulation system using a sensor on the end effector or tool or from feedback information from the manipulator which of course contains data at all times as to the position and orientation of the tool. 
     The optical assembly can be mounted on the tool itself, so as to movable with the tool, at a position spaced from the tip so as to have a field of view including the tip of the tool or the optical assembly can be mounted on the tool directly at the tip of the tool so as to have a field of view looking out from the tip. 
     Preferably the optical assembly can be mounted on a support arm separate from the robotic arm or arms so as to be moveable with the support arm where the support arm is controlled to avoid interference with the robot arms which move to effect the surgical procedures. 
     Preferably the control system is arranged to operate the optical assembly to change one or more of the viewing parameters thereof in response to movement of the robot arm. 
     Alternatively the control system is arranged to operate the optical assembly to change one or more of the viewing parameters thereof in response to movement of the tool relative to the optical assembly. 
     For example the control system is arranged to operate the optical assembly to change the focal position thereof in response to movement of the tool relative to the optical assembly to focus in the area of the tool tip. 
     For example the control system is arranged to operate the optical assembly to change the focal depth thereof in response to movement of the tool relative to the optical assembly. 
     Preferably the robot arm or arms are controlled to be moved in response to input from a user and the movement of the arm or arms is scaled in relation to the image displayed. 
     Preferably the robot arm or arms are controlled to be moved in response to input from a user and the movement of the arm or arms is limited by no-touch zones indicated on the image. 
     Preferably the MRI system is arranged to generate MR images and the control system is arranged to cooperate with a control system of the MRI in order to overlay the MR images on the visual images on the display. 
     In this arrangement, preferably the control system of the MRI is arranged to operate in response to changes in the visual image displayed. 
     In this arrangement, preferably the control system of the MRI is arranged to change the MR images acquired for overlay in response to changes in the visual image displayed. 
     In an arrangement where the apparatus is used with a surgical robot system including at least one robot arm with at least one end effector for operating one or more surgical tools, preferably the control system of the MRI is arranged to operate in response to movement of the tool and/or to changes in the visual image displayed. 
     Preferably the control system of the MRI is arranged to change one or more of: 
     the scan parameters of the MR images including one or more of resolution, slice thickness and dimension; 
     the scan type (T1, T2, etc); 
     the part of the patient/anatomy is being scanned based on either the visual image changing or the tool moving. 
     For example the control system of the MRI is arranged to trigger a scan. 
     For example the control system of the MRI is arranged to change the MR imaging from detecting a position of the tool tip to providing an anatomical image. 
     Preferably the control system is integrated with an IGS system which can overlay or augment the surgeon&#39;s view with image guidance data. 
     Preferably the optical assembly is arranged to detect visual images, IR images and/or florescence. 
     Preferably the optical assembly is arranged for receiving light from the part of the patient including visible light and florescent light emitted from fluorescing cells within the part, wherein the MRI system is arranged to generate MR images and wherein the control system is arranged to cooperate with a control system of the MRI in order to overlay the MR images on the visual images including the florescent light on the display. 
     Preferably the combination of quantitative fluorescence imaging with MR imaging is used to determine the amount of residual tumor present during a neurosurgical procedure, to guide the surgeon or the surgical robot in the resection of this residual tumor and guarantee that normal brain is left intact. 
     Preferably the patient receives a drug which enters brain tumor cells exclusively and fluoresce once resident therein. 
     Preferably the fluorescence is analyzed quantitatively, such that, since the fluorescent drug resides exclusively in the tumor cells, the quantitative measurement of the drug concentration is a measure of the concentration of tumor cells. 
     Preferably the MR imaging is used to provides a more complete picture of the location of tumor cells present. 
     Preferably the image representing the residual tumor mass is segmented and the data transferred to the robot which is used to resect the tumor to the level assigned by the quantitative analysis of the fluorescent images. 
     Preferably the MR images which are co-registered with the fluorescent images are involved in the segmentation to provide tumor cell zones and also keep out zones related to eloquent and sensitive brain structures. 
     Preferably the imaging rate for the fluorescence imaging is of the order of 30 frames per second so it allows the resection to be monitored as it occurs. 
     Preferably the robot is programmed to stop as each MRI image is recorded. 
     Preferably the MR imaging includes diffusion tensor imaging which shows on the image all the fiber tracks in the brain and of particularly importance, those around the tumor. 
     Preferably the fluorescent chemicals which attach to the tumor cells also contain MRI markers so that they appear on both the MR images and the fluorescence images. 
     Preferably the registration of the images is achieved by placing markers on a tool of the robot or surgical instrument. 
     Surgery in the bore requires proper lighting in the bore or the surgeon will not be able to operate. The surgeon requires the ability to change the lighting level, the focus of the lighting and the colour temperature very quickly and efficiently. In the present arrangement, changing the surgical lighting and lighting parameters is achieved automatically by using information from the position and orientation of the robot arm, using the information from the microscope such as magnification level, focus and depth of field, and information on the volume being scanned by the MRI and the MRI scan parameters. 
     In the present arrangement, the in-bore fluorescent microscope system can be connected with a fluorescence delivery system. It will be appreciated that the amount of fluorescence of a tissue sample being viewed can vary dependent on the amount of fluorescence activating agent which is applied to the patient. Thus, in some cases during a procedure, it can be determined by a reduction in the level of fluorescence being detected that the amount of the fluorescence agent needs to be increased. This can be applied in different ways well known to a person skilled in this art including for example, aerosol or an intravenous injector. 
     The invention includes an MR compatible microscope that provides a surgeon with the ability to view a surgical site in 2D or 3D either locally or remotely at a remote viewing station, along with a novel mounting mechanism that is optimized for use in the bore of an imaging magnet (e.g., in combination with a surgical robot in the bore). 
     The device can have controls which give the surgeon the ability to change the viewing parameters of the microscope including zooming, depth of field, focus, pan, tilt, window levelling, color, balance, etc. Surgical lighting can be integrated into the microscope to allow viewing of the surgical site. The device can be integrated with IGS system which can overlay or augment the surgeon&#39;s view with image guidance data. 
     The microscope system contains an imaging/encoding device, a processing device, and one or more display devices. The imaging/encoding device is located near the patient in the bore of a magnet, whereas the processing device is located outside of the RF shield. The display devices can be located within or outside of the RF shield. For example, to support remote viewing as may be needed with a surgical robot, the display device can be located in a control room. 
     While the MR is imaging (e.g., real-time update of MR images for use in surgery), the MR compatible microscope can produce the stereoscopic display for the corresponding visual real-time update of the surgical site. These can also be combined for real-time overlay of the MR images for the real-time update of the stereoscopic display. 
     The stereoscopic signals are displayed on screens for both 2D and 3D displays, and can optionally be sent to a head mounted display. The output of the microscope can be a traditional binocular setup or be part of a stereoscopic 3D display either with or without 3D glasses. Video can also recorded and archived. 
     The microscope is minimally sized to allow it to be located in the bore of an imaging magnet, and can contain the following characteristics: 
     Different magnification levels that are adjustable from a remote location (outside of bore) 
     Focusing capabilities from a remote location (outside of bore) 
     Integrated surgical lighting. 
     Fluorescent viewing support. 
     Since the components of the microscope can be near the surgical field, they are sterilizable. 
     For MR compatibility the system can: 
     Include integrated optics and digitizing in a device located in the bore 
     Use optics including lenses with fiber optics in the bore to route the optical signals out of the bore, with all electronics mounted outside of the bore and RF shielded 
     Use MR compatible circuits and imaging chips mounted at the tip of the device (where the optics are located, that is, chip in the tip). 
     Use images which are digitally encoded. 
     The 3D image from the MR compatible microscope can be integrated into any application where a tradition microscope view is integrated. 
     This device can work standalone or can be part of a surgical robotic system. 
     The MR compatible microscope can be mounted on apparatus that allow the microscope to be positioned over a patient in the bore of the magnet, such as free-standing on the OR floor and extend the microscopy into the bore, mounted to the magnet bore or other equipment in the bore. 
     The microscope can also be mounted onto a surgical robot, for example, mounted onto or near the end-effectors of a robot arm. If two robot arms operate in the bore, then each arm could have a separate microscope. The microscope can also be combined and integrated directly with the tools or instruments which are attached to the robot end effector(s). This can also be combined with a microscope display independent of a robot. 
     The system can provide the surgeon with the ability to view in either 2D or 3D the surgical site in the bore of an MRI either remotely or locally, this enables microsurgery to take place in the bore of an MRI, for example, in combination with a surgical robot 
     Attaching the microscope to each end effector and/or integrated tool of a robot working in the bore provides the surgeon with view of the surgical site which is always inline with the surgical tool. For example, the microscope can be mounted under, on top of, or beside the tools/end effector to maximizes the viewing capabilities of the device while minimizing the interference with performing surgery. 
     The small size allows multiple microscopes to be used for the same surgery in the bore. 
     The arrangement described above can also be used for the Detection and Removal of residual Brain Tumors during Neurosurgery. 
     Intra cranial malignant brain tumors are the most common and aggressive primary tumors in the central nervous system and carry one of the worst prognosis of all types of cancers. Radical surgical resection is the major treatment for these tumors and this is often supplemented with radiation treatment and/or chemotherapy. The goal of the surgical procedure is to remove all of the tumor tissue or at least as much as possible without causing any neurological deficit to the patient. Most brain tissue is eloquent and so the surgeon cannot remove any normal brain tissue since this could result in neurological dysfunction. The advent of intra operative MRI has increased the surgeon&#39;s ability to increase the amount of resection without removing normal brain tumor. Intra operative MRI also eliminates the problem of brain shift which can make navigation equipment inaccurate and therefore of limited utility in defining tumor boundaries. 
     Another method for detecting residual tumor cells during surgical resection which has been developed is to use fluorescence imaging of chemicals which attach only to the tumor cells and which fluoresce under optical irradiation. This optical image when taken during the surgical procedure provides the location of tumor cells within the surgical cavity. This can be achieved in real time but is only visible at the surface of the residual tumor tissue. The optical image does not provide information as to what is just below the surface which may be highly sensitive brain tissue. MRI imaging is not as sensitive as fluorescent imaging and therefore a larger number of cancer cells need to be present for detection by MRI. 
     The invention is to combine quantitative fluorescence imaging with MR imaging determine the amount of residual tumor present during a neurosurgical procedure, to guide the surgeon or the surgical robot in the resection of this residual tumor and verify that normal brain is left intact. The surgical procedure can be performed in the operating room equipped with a moveable MRI magnet capable of moving over the magnet for imaging at the appropriate time or in the bore of the magnet when in an MRI equipped operating theatre. 
     The patient receives a drug which enters brain tumor cells exclusively and fluoresce once they are resident therein. The fluorescence is monitored at the appropriate frequency by an operating microscope or a camera. The fluorescence is analyzed quantitatively. Since the fluorescent drug resides exclusively in the tumor cells the quantitative measurement of the drug concentration is a measure of the concentration of tumor cells. The drug does not enter all the tumor cells but the concentration is representative. 
     The MR imaging provides a much more complete picture of the amount of tumor cells present. Co-registration of the MR images to the fluorescent images is used to calibrate the fluorescent images. It is well known that tumors are very heterogeneous with the heterogeneity being both in terms of tumor cells and even more importantly in the grade. The grade is a measure of the malignancy of a tumor and ranges from 1 to 4 with 4 being the most malignant. Often the ability of the fluorescent drugs to enter a cell depends on its grade and some drugs may just enter and hence mark only a specific grade of tumour, for example only grade  4  tumors. The MRI image is normally relatively independent of grade and therefore provides a more complete picture of the cancer cell population. 
     The image representing the residual tumor mass can be segmented and the data transferred to the robot and the robot resect the tumor to the level assigned by the quantitative analysis of the fluorescent images. The resection of the tumor mass is monitored by the rapid fluorescent imaging. The MR images which are co-registered with the fluorescent images are involved in the segmentation to provide tumor cell zones and also keep out zones related to eloquent and sensitive brain structures. These zones are registered for both MR and Fluorescent guided resection. The imaging rate for the fluorescence imaging is of the order of 30 frames per second so it monitors the resection as it occurs. The resection can be performed out of the magnet by the surgeon or in the magnet using the robot. The robot can resect the tumor automatically using the segmented images updated by the rapid fluorescent imaging. MRI in the brain can not reach these rates and each image of reasonable resolution takes about 5 seconds so that the robot should be programmed to stop as each MRI image is recorded. The quantization of the fluorescence images guides the robot. As stated above the robot can resect automatically or can be guided by the surgeon as to which tissue should be removed. The MRI shows the surgeon the proximity of sensitive brain tissue to the tool held by the robot and permits the robot to resect much closer to the sensitive brain tissue. There are many types of tissue but a good example is the optic nerve. Cancer tissue can essentially wrap itself around the nerve. The surgeon wishes to resect as much tissue as possible but not have any deleterious effect on the nerve function. The combination of real time fluorescence and rapid MRI permits maximum resection of the tumor tissue without impacting nerve function. MR Imaging in the operating room using diffusion tensor imaging shows all the fiber tracks in the brain and of particularly importance, those around the tumor. Again, the combined imaging techniques allow the robot to resect any tumor tissue very close to these tracks without impacting the functionality of the tracks. The resection of tumors close to sensitive areas can be controlled by the surgeon or can be controlled by programming keep out zones as described above. 
     The fluorescent chemicals which attach to the tumor cells can also contain MRI markers so that they appear on both the MRI images and the fluorescence images. The two sets of images need to be registered to one another and this can be achieved by placing appropriate markers on a tool of the robot or a surgical instrument. 
     In summary the combination of the two imaging technologies takes advantage of the high sensitivity, the rapid imaging and ease of acquisition capabilities of fluorescence with the three dimensional and independence of tumor grade imaging of MRI. MRI also provides a significant level of safety for normal brain tissue during the resection. 
     The advantage of the invention is that it results in increased resection percentage and decreased neurological deficit. It is the combination of intra operative MRI, intra operative fluorescence and the robot which makes this unique and innovative. The aim is always to improve patient outcome and having the imaging technologies essentially simultaneous available when the surgeon (robot) performs the surgery leads to the best result. The fluorescence imaging brings the dimensions almost to the cellular level and the robot is much more accurate than any human surgeon. 
     This invention bring together real time imaging at a cellular level of tumor cells with almost real time imaging of the environment of these tumor cells in the human brain at the time when the surgeon is actually performing the surgical procedure. This means that the surgeon knows precisely where the tumor cells that are being resected are and their location relative to the all other parts of the brain. The addition of MRI to fluorescence imaging permits all the tumor mass to be detected even when the tumor is heterogeneous. The combination of fluorescent imaging with MRI imaging allows imaging to monitor tumor resection both in the bore and out of the bore. The use of the robot to perform the procedure allows the tumor to be resected in the bore of the magnet with both MRI and fluorescence imaging. The combination of both imaging modalities when processed enables the system to define both the target tissue and the no go zones to the robot or the surgeon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic side elevational view of a microsurgical robot system operating with the bore of an MR magnet with a viewing device for real time viewing of the tools and operation site which can be overlaid with real time MTR images from the imaging system. 
         FIG. 2  is a schematic side elevational view similar to that of  FIG. 1  showing a different mounting for the viewing system. 
         FIG. 3  is a schematic view showing the viewing system. 
         FIG. 4  is a schematic side elevational view of one robot arm of the system of  FIG. 1  with the viewing device mounted on the tip of the tool. 
         FIG. 5  is a schematic side elevational view of the end effector of one robot arm of the system of  FIG. 1  with the viewing device mounted on the end effector adjacent the tool. 
         FIG. 6  is a schematic illustration of an MR image and visual image controlled micro-surgery system. 
     
    
    
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     DETAILED DESCRIPTION 
     An overview of the system is shown in  FIG. 6  which comprises a robot manipulator  10 , a work station  11  and a controller  12  which communicates between the robot manipulator and the work station. As an input to the work station is also provided a stereo microscope  13 , an MRI imaging system  14  and a registration system  15 . 
     The work station includes a number of displays including at first display  16  for the MRI image, a second display  17  for the microscope image and a third display  18  for the system status. Further the work station includes two hand controllers schematically indicated at  19  and an input interface  20  allowing the surgeon to control the systems from the work station while reviewing the displays. The work station further includes a computer or processor  21 , a data recording system  22  and a power supply  23 . 
     The display  17  includes a stereoscopic display  17 A which provides a simulated microscope for viewing the images generated by the stereo-microscope system  13 . Further the display  17  includes a monitor  17 B which displays a two dimensional screen image from the microscope system  13 . 
     The robot manipulator  10  includes a field camera  24  which provides an image on a monitor  25  at the work station. 
     The magnetic resonance imaging system  14  is of a conventional construction and systems are available from a number of manufacturers. The systems are of course highly complicated and include their own control systems so that the present workstation requires only the display of the image on the monitor  16  where that image is correlated to the position of the tool using known registration systems. 
     The hand controllers  19  are also of a commercially available construction available from a number of different sources and comprise 6 degrees of freedom movable arms which can be carefully manipulated by the surgeon including end shafts  19 A which can be rotated by the surgeon to simulate the rotation of the tool as described hereinafter. An actuator switch on the tool allows the surgeon to operate the actuation of the tool on the robot as described hereinafter. 
     The robot manipulator comprises a cabinet  101  and two arms  102  and  103  which are mounted on the cabinet together with the field camera  24  which is also located on the cabinet. The field camera is mounted at the back of the cabinet viewing past the arms of the front of the cabinet toward the patient and the site of operation to give a general overview field of the situation for viewing on the display  25 . 
     The control system  12  for communication between the work station and the robot manipulator and for controlling the operation of each of those components includes a force sensor sub system  121  and a motion control sub system  122  together with power supplies and further components as indicated schematically at  123 . The force sensor sub system controls the feed back forces as detected at the end effector of the robot arm to the hand control systems  19 . The motion control subsystem  122  converts the motion control sensors from the hand-control system  19  into individual operating instructions to the various components of the arms. The motion control sub system also provides an output which is communicated to the work station for display on the MRI imaging monitor  16  of the location of the tip of the tool relative to the image displayed on the screen  16 , as generated by the registration system  15 . 
     The structure of the arms is shown schematically in  FIG. 4 , where the arms are mounted with their base  111  for attachment to the cabinet support. Each of the arms  102  and  103  includes a number of joints which allow operation of a tool schematically indicated at  26 . Thus each arm includes a first joint defining a shoulder yaw pivot  131  defining a vertical axis of rotation. On the vertical axis is mounted a second joint  132  forming a shoulder roll joint which provides rotation around a horizontal axis. The shoulder yaw axis extends through the joint  132 . A rigid link  135  extends from the joint  132  to an elbow joint  136  which is cantilevered from the shoulder roll joint  132 . The elbow joint includes an elbow yaw joint  137  and an elbow roll joint  138 . The yaw joint  137  is connected to the outer end of the link  135  and provides rotation about a vertical axis. The roll joint  138  is located on the axis and provides a horizontal axis. A link  141  lies on the horizontal axis and extends outwardly from the joint  138  to a wrist joint generally indicated at  142 . The wrist joint  142  includes a wrist yaw joint and wrist roll joint. The wrist yaw joint provides a vertical axis about which a link can pivot which carries the roll joint. The roll joint provides a horizontal axis which allows the tool  26  to rotate around that horizontal axis. The tool  26  includes a roll joint  148  which provides rotation of the tool  26  around its longitudinal axis. The tool further includes a tool actuator  149  which can move longitudinally along the tool to provide actuation of the tool using various known tool designs. 
     Thus the forces required to provide rotation around the various axes are minimized and the forces required to maintain the position when stationary against gravity are minimized. This minimization of the forces on the system allows the use of MRI compatible motors to drive rotation of one joint component relative to the other around the respective axes. 
     The arrangement described above allows the use of piezoelectric motors to drive the joints. Such piezoelectric motors are commercially available and utilize the reciprocation effect generated by a piezoelectric crystal to rotate by a ratchet effect a drive disc which is connected by gear coupling to the components of the joint to effect the necessary relative rotation. 
     The robot therefore can be used in the two arm arrangement for microsurgery in an unrestricted area outside of the closed bore magnet or for microsurgery within an open bore of a magnet where the arrangement of the magnet can be suitable to provide the field of operation necessary for the two arms to operate. The two arms therefore can be used with separate tools to effect surgical procedures as described above. In some cases a single arm can be used to effect stereotactic procedures including the insertion of a probe or cannula into a required location within the brain of the patient using the real time magnetic resonance images to direct the location and direction of the tool. 
     In  FIG. 1 , the system is shown schematically in operation within the bore of a magnet  30  of the MRI system  14 . The bore  31  is relatively small allowing a commercially available patient table  32  to carry the required portion of the patient into the bore to the required location within the bore. The field camera is used within the bore for observing the operation of the robot  10  and particularly the tool  26 . 
     The stereo microscope system of the present invention as shown in mounted on a suitable support adjacent the patient for viewing the necessary site. The stereo microscope includes two separate imaging systems one for each channel which are transmitted through suitable connection to the display  17  at the work station. Thus the surgeon can view through the microscope display  17 A the three dimensional image in the form of a conventional microscope and can in addition see a two dimensional image displayed on the monitor  17 B. 
     The stereo microscope system shown in  FIG. 3  comprises an optical assembly  50  for receiving light from the part of the patient, the optical assembly including stereoscopic viewing components  51  and  52  arranged for use in generating 2D and 3D images as described above. 
     The optical assembly is adjustable using the opto-electronics  53  to adjust one or more of the field of view, zoom, depth of field, focus, pan, tilt, window levelling, color, balance, magnification in response to control signals from a remote controller  56 . 
     An illumination source  54  is integrated into the optical assembly to illuminate viewing of the part. 
     The light images from the left and right optics are converted using a CCD or similar system at the electronics system  53  into digital electrical signals which are transmitted to the microscope control system  56  for display on the display  70  of the work station  10  for viewing of images generated from the light received from the part. The control system  56  acts to control the optical assembly and for generating the images. A communication arrangement in the form of a cable  55  is provided for communicating between the optical assembly  50  and the processing system  56  outside the bore. 
     The optical assembly  50  includes a mount  57  arranged to locate the assembly within a bore of an MRI magnet. In  FIG. 1 , the mount is arranged to attach the assembly to a fixed position within the bore at a location where it does not interfere with the arms  102 ,  103 . The optical assembly  50  is sterilizable using conventional techniques. 
     The optical assembly, control system and the communication arrangement are arranged to be compatible with the MRI magnet so as to allow simultaneous communication and MR imaging. This is achieved by the following: 
     an RF filter  57  on the electrical communication cable  55  to prevent stray RF from the electrical communication cables signals from effecting the imaging; 
     an RF filter  58  on the electrical communication cable  55  to prevent the RF imaging signals from affecting the imaging/encoding device; 
     an RF enclosure  59  around the optical assembly and the imaging/encoding device; 
     the optical assembly  50  and imaging/encoding device  53  being formed of materials which are compatible with the magnetic field; 
     cable traps  60  on the electrical communication cable  55  to prevent heating thereof in the RF field of the imaging system; 
     a magnetic shield  61  around or adjacent the components to prevent the magnetic field from affecting the components. 
     In  FIG. 1 , the imaging/encoding device or CCD  53  is located near the patient in the bore of a magnet at the optical assembly and the control system  56  is located outside of the bore with communication therebetween using wires for communication the electrical signals carrying the image data. 
     The display  70  is a remote display outside the bore so that the microsurgery is carried out by a surgeon at the remote operating location  10  using robotic control of the effectors. The display  70  provides a visual real-time update of the surgical site and is combined with a real-time overlay of MR images for the real-time update of the stereoscopic display. That is the images from the MR system are registered with the visual images and overlaid to be viewed simultaneously by the surgeon. The visual images and also the MT images are also controlled as explained hereinafter so that the views are compatible with each other and with the operation of the tools  26 . 
     The apparatus is used with the surgical robot system described above. In  FIG. 5  the optical assembly is mounted on the robotic arm  102  or two separate systems are mounted on respective ones of the arms  102  and  103  so as to be moveable therewith. That is the optical assembly is mounted on the robotic arm so as to movable with the tool and so as to have a field of view F including a tip of the tool. 
     In  FIG. 4  the optical assembly  50  is mounted on the tool at a tip of the tool. In this case the assembly can be made much smaller to be movable with the tip possibly endoscopically. 
     In  FIG. 2 , the optical assembly  50  is mounted on a support arm  50 A separate from the robotic arm or arms so as to be moveable with the support arm  50 A where the support arm  50 A is controlled in its movement to avoid interference with the robot arms  102 ,  103  which move to effect the surgical procedures. 
     As explained previously, the control system  53  includes motors  62 ,  63  arranged to operate the optical assembly to change one or more of the viewing parameters thereof in response to movement of the robot arm or in response to movement of the tool relative to the optical assembly. For example the control system is arranged to operate the optical assembly using the motors  62 ,  63  to change the focal position thereof in response to movement of the tool relative to the optical assembly to focus in the area of the tool tip. For example the control system is arranged to operate the optical assembly using the motors  62 ,  63  to change the focal depth thereof in response to movement of the tool relative to the optical assembly. 
     In addition, the robot arm or arms  102  and  103  are controlled to be moved in response to input from the surgeon with the movement of the arm or arms being scaled in relation to the image displayed. This is obtained by providing information from the display  70  and the system  56  to the motion controller sub system  122  so that the amount of movement of the tool in response to an input from the hand controllers  19  changes, that is increases or decreases depending on the size of the image displayed and the display  70 . This assists the surgeon in controlling the movement since the amount of movement he achieves by moving the hand controllers by a predetermined distance matches the amount of movement viewed regardless of the scale of the displayed image. 
     In addition, the surgeon can set up in the image a no-touch zone which is intended to never be entered by the tool in view of potential damage to the patient. The controller  122  is arranged to operate robot arm or arms so that they are controlled to be moved in response to input from a user while preventing their entering the no-touch zones indicated on the image. This requires coordination of the processing programs of the control system  122  and the imaging system  56 . 
     In addition the MR control system  14  is arranged to operate the MR imaging in response to changes in the visual image displayed as controlled by system  56  and in response to movement of the tool as controlled by system  122 . 
     For example, the MR control system  14  is arranged to control, in response to changes in image and/or movement of the tool, the scan parameters of the MR images including one or more of resolution, slice thickness and dimension; the scan type (T1, T2, etc); the part of the patient/anatomy. In addition the control system  14  can be used to trigger a scan in response to a change in image displayed and/or the movement of the tool. 
     In addition the control system  14  of the MRI is arranged to change the MR imaging from detecting a position of the tool tip to providing an anatomical image. 
     In addition the control system is integrated with the IGS system which can overlay or augment the surgeon&#39;s view with image guidance data. 
     Preferably the optical assembly is arranged to detect visual images, IR images and/or florescence. These can be converted to visual images displayed on the display 
     Where the imaging/encoding device is located remotely from the optical assembly as shown in  FIG. 2 , the communication arrangement between the optical portion  71  and a remote CCD  72  is provided by a fiber optic system or a light tube movable with the optical assembly. The use of a light tube or a fiber optic avoids the possibility of interference between the RF signals of the MR system and any RF field generated by the signals in the cable of  FIG. 1 . 
     In another arrangement, the display can be provided as a head mounted display for mounting on the surgeon. 
     The arrangement described above can also be used for the Detection and Removal of residual Brain Tumors during Neurosurgery. The arrangement combines quantitative fluorescence imaging with MR imaging determine the amount of residual tumor present during a neurosurgical procedure, to guide the surgeon or the surgical robot in the resection of this residual tumor and verify that normal brain is left intact. The surgical procedure can be performed in the operating room equipped with a moveable MRI magnet capable of moving over the magnet for imaging at the appropriate time or in the bore of the magnet when in an MRI equipped operating theatre. 
     Thus in this arrangement, as explained above, the optical assembly, control system  56  and the communication arrangement  55  are compatible with the MRI magnet so as to allow simultaneous communication and MR imaging and the MRI system is arranged to generate MR images and the control system  56  is arranged to cooperate with a control system  20  of the MRI in order to overlay at the display  70  the MR images on the visual images including the florescent light on the display. 
     The apparatus is used with a surgical robot system  10  including at least one robotic arm  102 ,  103  with at least one end effector  149  for operating one or more surgical tools  26 . The control system  56  of the imaging system is arranged to generate quantitative information relating to the amount of light emitted in the fluorescence. The combination of quantitative fluorescence imaging with MR imaging is used to determine the amount of residual tumor present during a neurosurgical procedure, and to display this on the display  70  to guide the surgeon or the surgical robot in the resection of this residual tumor and verify that normal brain is left intact. 
     In the operation, the patient receives a drug which enters brain tumor cells exclusively and fluoresce once resident therein. Thus the fluorescence is analyzed quantitatively, such that, since the fluorescent drug resides exclusively in the tumor cells, the quantitative measurement of the drug concentration is a measure of the concentration of tumor cells. This allows the MR imaging is used to provides a more complete picture of the amount of tumor cells present. 
     The control system can be operated so that the image representing the residual tumor mass is segmented and the data transferred to the robot which is used to resect the tumor to the level assigned by the quantitative analysis of the fluorescent images. 
     On the display, the MR images which are co-registered with the fluorescent images are involved in the segmentation to provide tumor cell zones and also keep out zones related to eloquent and sensitive brain structures, 
     The control  56  is operated so that the imaging rate for the fluorescence imaging is of the order of 30 frames per second so it allows the resection to be monitored as it occurs in real time. 
     The control system  10  of the robot is programmed to stop movement of the robot as each MRI image is recorded. 
     The MR control  20  is arranged such that the MR imaging includes diffusion tensor imaging which shows on the image all the fiber tracks in the brain and of particularly importance, those around the tumor. 
     The fluorescent chemicals injected which attach to the tumor cells can also contain MRI markers so that they appear on both the MR images and the fluorescence images. 
     The registration system is arranged such that the registration of the images is achieved by placing markers on a tool of the robot or on surgical instruments. 
     Mounting the optical assembly to the end effector or tool as shown in  FIG. 5  provides the surgeon with a view on the display  70  that is always inline with the surgical site and area that is being operated on. The problem with doing this is that the camera view moves with the tool or end effector and this changes the orientation of the 3D view. Changing the orientation of the view means that the surgeon can lose his or her sense of where the tool or arm is in relation to the real world. Automatic orientation correction of the 3D scene on the visual display is provided in the software of the control system  20  controlling the image as displayed. This is done by incorporating into the control  20  information relating to the orientation of the tool. As shown in  FIG. 5  input as to the orientation is provided from a gyroscope system  50 A mounted on the optical system or formed as part of the optical system. As an alternative, where the robot system itself has data defining the orientation of the tool holder or end effector, either from sensors in the system or from analysis of the movements of the system, this data from the robot is incorporated into the control  20 . Therefore the optical assembly data is fed into the software and by adjusting the visual image data using this information the image can be properly oriented. That is, if the system acts to rotate the vision system then the 3D output view on the monitor would also be rotated and now what was left is could now be top or bottom (for example). The solution is to manipulate the visual information digitally (i.e. rotate the data) with the orientation information for the robot end effector and/or tool. The orientation information can be obtained from the tool manipulation system using a sensor on the end effector or tool or from feedback information from the manipulator which of course contains data at all times as to the position and orientation of the tool. 
     As shown in  FIG. 5 , the optical assembly is mounted on the tool itself, so as to movable with the tool, at a position spaced from the tip so as to have a field of view including the tip of the tool or the optical assembly can be mounted on the tool directly at the tip of the tool so as to have a field of view looking out from the tip. 
     Surgery in the bore requires proper lighting in the bore or the surgeon will not be able to operate. This is shown in  FIG. 1  at  80  including light sources  80 A and  80 B. The surgeon requires the ability to change the lighting level, the focus of the lighting and the colour temperature very quickly and efficiently. In the present arrangement, changing the surgical lighting and lighting parameters is achieved automatically at the control system  80 C by using information available from the control system  20  in relation to the position and orientation of the robot arm, by using the information available at the control system  20  in relation to the microscope such as magnification level, focus and depth of field, and information available at the control system  20  on the volume being scanned by the MRI and the MRI scan parameters. 
     In the present arrangement, the in-bore fluorescent microscope system can be connected with a fluorescence delivery system  90 . It will be appreciated that the amount of fluorescence of a tissue sample being viewed can vary dependent on the amount of fluorescence activating agent which is applied to the patient. Thus in some cases during a procedure, it can be determined by a reduction in the level of fluorescence being detected that the amount of the fluorescence agent needs to be increased. This can be applied to the patient by the system  90  in different ways well known to a person skilled in this art including for example, aerosol or an intravenous injector. 
     Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.