Abstract:
In the present invention, a system and associated method is provided for image-guided navigation during a medical procedure. The system includes a movable gantry having an X-ray source, an X-ray detector and a laser disposed on the detector offset from the area of the detector receiving the beam from the source, a movable table and a system controller operably connected to the gantry, the X-ray source, the X-ray detector, the laser and the table. In the method, the controller determines an optimal trajectory for the insertion of an interventional device into the body to intersect the target, positions the gantry to locate the laser at a point where a laser beam is emitted from the laser along the optimal trajectory outside of the X-ray beam, and takes additional images during the procedure to show the position of the interventional device in the body as compared with the optimal trajectory.

Description:
BACKGROUND OF INVENTION 
       [0001]    The subject matter disclosed herein relates to the field of image-guided interventional devices and methods, and more specifically to guiding devices and techniques utilized with the interventional devices and methods. 
         [0002]    Interventional devices, procedures and methods are used in a variety of situations, such as providing the necessary treatment or diagnostic interaction with the tissue or region of interest within the patient but in a minimally invasive manner, thereby greatly lessening the trauma and recovery time for the patient undergoing the procedure or treatment. As a result, these minimally invasive medical interventional devices, procedures and methods are becoming increasingly important in the treatment of various conditions, including coronary heart disease and are also increasing in the field of biopsies, spinal column treatments and tumor ablations. 
         [0003]    In a minimally invasive interventional procedure, one or more medical devices, e.g., a needle, are introduced into the body of a patient for treatment or diagnostic purposes. After the initial insertion of the needle into the patient&#39;s body, at least the tip of the needle is no longer visible for a physician performing the interventional procedure. In order to navigate the needle within the body of the patient, the needle must therefore be visualized in a suitable way to illustrate the position of the needle to enable the clinician to move the needle to the desired area of interest within the patient. 
         [0004]    Various systems and methods are available today for determining the position of the instrument in the patient&#39;s body during minimally invasive medical interventions, which is necessary for visualizing the instrument, in particular the tip of the instrument, in image information from inside the patient&#39;s body. Some examples of these types of systems and methods are illustrated in U.S. Pat. No. 6,487,431 entitled Radiographic Apparatus And Method For Monitoring The Path Of A Thrust Needle and US Patent Application Publication No. US2008/0200876 entitled Needle Guidance With Dual-Headed Laser, both of which are expressly incorporated by reference herein in their entirety for all purposes. These systems and methods involve the use of image information obtained on the body region acquired preoperatively or intraoperatively by an imaging system, such as a computed tomography scanner, a magnetic resonance device or a C-arm X-ray device as 2D images, or as a 3D image. The information provided by the images can be utilized to assist the clinician in determining an appropriate insertion path along which to insert the interventional device into the patient. The initial point of the insertion path on the skin of the patient can be illuminated by a laser or other suitable light emitting device to enable the clinician to insert the device at the proper starting point. The imaging system can then obtain addition image information on the positioning of the device relative to the area of interest to guide the device. 
         [0005]    However, certain significant issues are present with regard to these prior art systems and methods relates to the laser utilized to illuminate the insertion point on the skin of the patient. For example, in those systems where the laser is aligned coaxially with the imaging system, i.e., in a bull&#39;s-eye view where the laser and the X-ray beam emitted by the imaging system to strike the detector are coaxial, depending upon the position of the body of the patient, the area of interest within the patient, and the desired path of insertion, it may not be possible to position the imaging system at the proper location to enable the laser to illuminate the entry point on the patient. 
         [0006]    A further drawback of the coaxial position of the laser and the X-ray beam is that, because the point identified by the laser is positioned within the imaging field defined by the imaging system, the clinician must place his or her hands within the field in order to properly locate the interventional device on the patient. Doing so necessarily exposes the clinician to the radiation from the imaging system which is detrimental to the clinician, unless the clinician is utilizing an extender for the device, which necessarily limits the effectiveness of the positioning of the device by the clinician. 
         [0007]    To address this issue, other prior art systems have been developed in which the laser is disposed on an armature separate from the imaging system, such as on a robotic arm. The arm can be positioned in order to illuminate the entry point on the patient for the interventional device, without need to be coupled to the imaging system. However, in these systems the clinician has to assume that the armature has properly positioned the laser with regard to the patient to illustrate the entry path, which is often not the case due to errors with regard to the operation of the system. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    There is a need or desire for a system and method that can provide images for the guidance of an interventional device used in a minimally invasive surgical procedure that does not include the above-mentioned drawbacks and needs in the prior art. These issues are addressed by the embodiments described herein in the following description of the invention, which is a system and method for increasing the angular positions for the detector in which the procedure can be performed and without the need for the clinician/physician performing the procedure to place their hands within the beam striking the detector. 
         [0009]    In the exemplary embodiments of the system and associated method, an imaging system utilized to obtain X-ray/fluoro images of the area of interest and the position of the interventional device within the patient includes one or more light sources or emitters, e.g., lasers, positioned on the detector for the imaging system. The lasers are positioned in multiple different offset locations with regard to the detector, such that the lasers are not coaxial with the X-ray beam. This positioning enables each laser to direct a laser beam at a location on the patient within the X-ray beam generated by the imaging system that enables the physician to access the point indicated by the laser beam with a tool without obstructing the view of the positioning laser and without the physician having to place their hands within the field of the X-ray beam. Further, the offset location of the laser enables the detector to be positioned at locations relative to the patient where the laser can project an entry point for the tool on the patient that were previously not possible with prior art coaxial systems. In addition, the system and method allows the clinician/physician to position the tool while simultaneously using the imaging system to check the position/depth of the interventional device as it is moved towards the area of interest. 
         [0010]    According to one exemplary embodiment of the invention, a system for image-guided navigation of a tool is provided that includes an X-ray source capable of emitting an X-ray beam, an X-ray collimator capable of limiting the beam extent, an X-ray detector capable of detecting the X-ray beam on a first position of the detector and a light emitting device disposed on the detector in a second position, wherein the second position is offset from the first position. 
         [0011]    According to another exemplary embodiment of the invention, a method of providing image-guided navigation during a medical procedure includes the steps of providing an image-guided navigation system including a movable gantry on which is disposed an X-ray source capable of emitting an X-ray beam, an X-ray detector capable of detecting the X-ray beam on a first position of the detector and a light source disposed on the detector in a second position, wherein the second position is offset from the first position, a target support disposed within the field of movement of the gantry and a system controller including a user input operably connected to the gantry, the X-ray source, the X-ray detector, the laser and the target support, operating the X-ray source and X-ray detector to obtain at least one image of a target within a body, determining an optimal trajectory for the insertion of a tool into the body to intersect the target, positioning the gantry to locate the light source at a point where a light beam is emitted from the light source along the optimal trajectory outside of the X-ray beam. 
         [0012]    According to another exemplary embodiment of the invention, a method of providing image-guided navigation of a tool includes the steps of providing an image-guided navigation system including a movable gantry on which is disposed an X-ray source capable of emitting an X-ray beam, an X-ray detector capable of detecting the X-ray beam on a first position of the detector and a laser disposed on the detector in a second position, wherein the second position is offset from the first position, a target support disposed within the field of movement of the gantry and a system controller including a user input operably connected to the gantry, the X-ray source, the X-ray detector, the laser and the table, operating the X-ray source and X-ray detector to obtain at least one image of a target within a body, determining an optimal trajectory for the insertion of a tool into the body to intersect the target, positioning the gantry to locate the laser at a point where a laser beam is emitted from the laser along the optimal trajectory, marking a calculated entry point on the body with the laser beam along the optimal trajectory, positioning a tip of the tool at the entry point, aligning the tool with the laser beam marking the optimal trajectory, inserting the tool into the body at the entry point along the optimal trajectory and obtaining an image of a position of the tool and the target within the body to compare with the optimal trajectory. 
         [0013]    It should be understood that the brief description above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The drawings illustrate the best mode presently contemplated of carrying out the disclosure. In the drawings: 
           [0015]      FIG. 1  is a schematic view of an X-ray/fluoro imaging and navigation system according to an exemplary embodiment of the invention. 
           [0016]      FIG. 2  is a flowchart of a method of operation of an X-ray/fluoro imaging and navigation system according to an exemplary embodiment of the invention. 
           [0017]      FIG. 3  is a schematic view of the operational capability of an X-ray/fluoro imaging and navigation system according to another exemplary embodiment of the invention compared with a prior art X-ray/fluoro imaging and navigation system. 
           [0018]      FIG. 4  is a schematic view of an X-ray/fluoro imaging and navigation system according to another exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments, which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense. 
         [0020]    Exemplary embodiments of the invention disclosed herein relate to a system and method for identifying an optimal trajectory for the insertion of an interventional device into a patient and displaying the position of the device as it is inserted into the body of the patient towards an area of interest. 
         [0021]    The system and method disclosed herein may be suitable for use with a range of imaging and navigation systems. To facilitate explanation, the present disclosure will primarily discuss the invention in the context of a C-arm fluoroscopic system. However, it should be understood that the following discussion may also be applicable to other and navigation systems. 
         [0022]    With this in mind, an example of a C-arm fluoroscopic imaging and navigation system  10  designed to acquire X-ray attenuation data at a variety of views around a patient and suitable for tomographic reconstruction is provided in  FIG. 1 . In the embodiment illustrated in  FIG. 1 , imaging system  10 , such as that disclosed in U.S. Pat. No. 9,076,255, incorporated herein by reference in its entirety for all purposes, includes a source of X-ray radiation  12  positioned adjacent to a collimator  14 . The X-ray source  12  may be an X-ray tube, a distributed X-ray source (such as a solid-state or thermionic X-ray source) or any other source of X-ray radiation suitable for the acquisition of medical or other images. 
         [0023]    The collimator  14  permits X-rays  16  to pass into a region in which a patient  18 , is positioned. In the depicted example, the X-rays  16  are collimated to be a cone-shaped or pyramidal-shaped beam, i.e., a cone-beam, that passes through the imaged volume of the patient  18  containing the area of interest or target T. A portion of the X-ray radiation beam  20  passes through or around the patient  18  (or other subject of interest) and impacts a detector array, represented generally at reference numeral  22 . Detector elements of the array produce electrical signals that represent the intensity of the incident X-rays  20 . These signals are acquired and processed to reconstruct images of the features within the patient  18 . 
         [0024]    Source  12  is controlled by a system controller  24 , which furnishes both power, and control signals for the examination sequences. In the depicted embodiment, the system controller  24  controls the source  12  via an X-ray controller  26  which may be a component of the system controller  24 . In such an embodiment, the X-ray controller  26  may be configured to provide power and timing signals to the X-ray source  12 . 
         [0025]    Moreover, the detector  22  is coupled to the system controller  24 , which controls acquisition of the signals generated in the detector  22 . In the depicted embodiment, the system controller  24  acquires the signals generated by the detector using a data acquisition system  28 . The data acquisition system  28  receives data collected by readout electronics of the detector  22 . The data acquisition system  28  may receive sampled analog signals from the detector  22  and convert the data to digital signals for subsequent processing by a processor  30  discussed below. Alternatively, in other embodiments the digital-to-analog conversion may be performed by circuitry provided on the detector  22  itself. The system controller  24  may also execute various signal processing and filtration functions with regard to the acquired image signals, such as for initial adjustment of dynamic ranges, interleaving of digital image data, and so forth. 
         [0026]    In the embodiment illustrated in  FIG. 1 , system controller  24  is coupled to a linear and rotational subsystem  32  and a linear and rotational positioning subsystem  34 . The rotational subsystem  32  enables the X-ray source  12 , collimator  14  and the detector  22  to be rotated one or multiple turns around the patient  18 , such as rotated primarily in an x, y-plane, or angulated with respect to the patient. The distance between the detector  22  and the X-ray source  12  can also be adjusted. It should be noted that the rotational subsystem  32  might include a gantry upon which the respective X-ray emission and detection components are disposed. Thus, in such an embodiment, the system controller  24  may be utilized to operate the gantry. 
         [0027]    The linear and rotational positioning subsystem  34  may enable the patient  18 , or more specifically a table supporting the patient, also called the target support, to be displaced within the imaging field of view of the system  10 . Thus, the table may be linearly or rotationally moved (in a continuous or step-wise fashion) within the gantry to generate images of particular areas of interest or target T within the patient  18 . In the depicted embodiment, the system controller  24  controls the movement of the gantry  32  and/or the positioning of the table  34  via a motor controller  36 . 
         [0028]    In general, system controller  24  commands operation of the imaging system  10  (such as via the operation of the source  12 , detector  22 , and positioning systems described above) to execute examination protocols and to process acquired data. For example, the system controller  24 , via the systems and controllers noted above, may rotate a gantry supporting the source  12  and detector  22  about an area of interest or target T so that X-ray attenuation data may be obtained at a variety of views relative to the target T. In the present context, system controller  24  may also include signal processing circuitry, associated memory circuitry for storing programs and routines executed by the computer (such as routines for executing image processing techniques described herein), as well as configuration parameters, image data, and so forth. 
         [0029]    In the depicted embodiment, the image signals acquired and processed by the system controller  24  are provided to a processing component  30  for reconstruction of images. The processing component  30  may be one or more conventional microprocessors. The data collected by the data acquisition system  28  may be transmitted to the processing component  30  directly or after storage in a memory  38 . Any type of memory suitable for storing data might be utilized by such an exemplary system  10 . For example, the memory  38  may include one or more optical, magnetic, and/or solid state memory storage structures. Moreover, the memory  38  may be located at the acquisition system site and/or may include remote storage devices for storing data, processing parameters, and/or routines for image reconstruction, as described below. 
         [0030]    The processing component  30  may be configured to receive commands and scanning parameters from an operator via an operator workstation  40 , typically equipped with a keyboard and/or other input devices. An operator may control the system  10  via the operator workstation  40 . Thus, the operator may observe the reconstructed images and/or otherwise operate the system  10  using the operator workstation  40 . For example, a display  42  coupled to the operator workstation  40  may be utilized to observe the reconstructed images and to control imaging. Additionally, the images may also be printed by a printer  44  which may be coupled to the operator workstation  40 . 
         [0031]    Further, the processing component  30  and operator workstation  40  may be coupled to other output devices, which may include standard or special purpose computer monitors and associated processing circuitry. One or more operator workstations  40  may be further linked in the system for outputting system parameters, requesting examinations, viewing images, and so forth. In general, displays, printers, workstations, and similar devices supplied within the system may be local to the data acquisition components, or may be remote from these components, such as elsewhere within an institution or hospital, or in an entirely different location, linked to the image acquisition system via one or more configurable networks, such as the Internet, virtual private networks, and so forth. 
         [0032]    It should be further noted that the operator workstation  40  may also be coupled to a picture archiving and communications system (PACS)  46 . PACS  46  may in turn be coupled to a remote client  48 , radiology department information system (RIS), hospital information system (HIS) or to an internal or external network, so that others at different locations may gain access to the raw or processed image data. 
         [0033]    While the preceding discussion has treated the various exemplary components of the imaging system  10  separately, these various components may be provided within a common platform or in interconnected platforms. For example, the processing component  30 , memory  38 , and operator workstation  40  may be provided collectively as a general or special purpose computer or workstation configured to operate in accordance with the aspects of the present disclosure. In such embodiments, the general or special purpose computer may be provided as a separate component with respect to the data acquisition components of the system  10  or may be provided in a common platform with such components. Likewise, the system controller  24  may be provided as part of such a computer or workstation or as part of a separate system dedicated to image acquisition. 
         [0034]    Referring now to  FIGS. 1 and 4 , the system  10  additionally includes a light source or emitter, such as a laser  50 , that is mounted to the detector  22  and operable by the system controller  24 . The laser  50  can be secured to the detector  22  in any suitable manner such that the laser  50  is located in an offset position relative to the axis  52  of the X-ray beam  20  striking the detector  22 . The laser  50  can be mounted directly to the detector  22 , such as within a housing for the detector  22 , or to the exterior of the detector  22  using a suitable support arm  56  or similar apparatus extending between the detector  22  and the laser  50 , which may be collapsible or fold-away for storage within the detector  22  or that can be removable from the detector  22  by mechanical, magnetic or other suitable supporting devices. The laser  50  can include a battery (not shown) to power the laser  50 . In another exemplary embodiment, the power, control and sensing signals used for the positioning and operation of the laser  50  can be provided by the system controller  24  as a feature of the attachment of the laser  50  to the detector  22 . Further, while one laser  50  is shown in the exemplary embodiments of  FIGS. 1, 3 and 4 , multiple lasers  50  can be mounted to the detector  22  at different positions and angular orientations relative to the detector  22 . Each additional laser  50  can extend the angular reach of the system  10 , allowing it to align at least one laser  50  with the desired needle path when the bull&#39;s eye view is not reachable, such as shown in  FIG. 3 . In the case where the desired needle path can be aligned with multiple lasers  50  without patient-gantry interference, the system controller  24  decides which laser  50  to turn on and align with the optimized trajectory  64  using computation and the clinical task information provided by the user. In this position the laser  50  can project a laser beam  58  onto the patient  18  that corresponds to the entry point  63  and trajectory  64  calculated for the particular tool or interventional device  60  to be utilized, such as in a medical procedure. The physician  62  performing the procedure can then place the interventional device tip  61  at the entry point  63  then the interventional device  60  along the trajectory  64  indicated by the laser beam  58  in order to insert the device  60  into the patient  18 . 
         [0035]    Each laser  50  is mounted to the detector  22  at a static and known position, such that the system  10  includes a value for the offset angle and distance that the laser  50  is positioned from the center of the X-ray beam  20  striking the detector  22 . However, in another exemplary embodiment, the laser(s)  50  can be movably positionable relative to the detector  22 . In this exemplary embodiment, once the laser(s)  50  is in the desired position, the system  10  determines the location (e.g., the offset angle and distance) of each laser  50  relative to the detector  22  for use in the procedure to be performed utilizing the system  10 . 
         [0036]    Looking at  FIG. 2 , an exemplary embodiment of the method of operation of the imaging/navigation system  10  to perform a procedure and track the device  60  is depicted in flowchart form. As depicted at block  100 , initially the system controller  24  computes and plans the trajectory  64  for the insertion of the interventional device  60  including the entry point  63  and the angle of the device  60  in one or more planes relative to the entry point  63 . This determination can be performed by imaging the target T within the patient  18  using the system  10  and using the images obtained in a suitable program, such as the Innova TrackVision software package available from GE Healthcare and disclosed in U.S. Pat. No. 8,600,138 entitled Method for processing radiological images to determine a 3D position of a needle, which is expressly incorporated herein by reference in its entirety for all purposes, to create a suitable 3D image of the target T and surrounding tissues in the patient  18  and determine/compute the optimal trajectory  64  for reaching the target T from the exterior of the patient  18 . 
         [0037]    Once the optimal trajectory  64  is determined, in block  102  the system controller  24  determines the gantry  32  and patient support  34  position for the Bull&#39;s Eye view as well as for the “Laserview” and a Progress view used by the system  10 . The Laserview is defined by the location of the detector  22  relative to the patient  18  where the selected laser  50  is positioned to illuminate the entry point  63  by directing the laser beam  58  along the computed optimal trajectory  64  to the target T, as shown in  FIG. 4 . The laser beam can be a simple line projecting a dot or in the shape of a cross-hair. In the Bull&#39;s-Eye view, the detector  22  and source  12  are aligned to project the X-ray beam  20  along the trajectory  64 . In a Progress view, the detector  22  and source  12  are oriented to project the X-ray beam  20  at a ninety degree (90°) angle relative to the trajectory  64 . As there are multiple Progress views, which is any view for the X-ray beam  20  that is oriented perpendicular to the needle trajectory  64 , the system controller  24  selects one Progress view which can be reached while minimizing the likelihood of a collision between the detector  20  and the table/patient support  34  and while also minimizing the distance between the Laserview position and the selected Progress view position, thereby preventing excessive travel for the system  10 . The Laserview may not be coplanar with the Bull&#39;s eye view and/or the selected Progress view. 
         [0038]    The Laserview position is achieved by adjusting the gantry  32  and patient support/table  34  linearly and/or rotationally to align the laser beam  58  with the desired angles for the trajectory  64 . The position of each angle/axis is determined by the system controller  24  using the trajectory (α,β) determined at step  100  offset by the known angle/position of the laser  50  relative to the detector  22 . In one exemplary embodiment, the gantry  32  and table  34  provide up to 5 extra degrees of freedom (2 rotations and 3 translations) enabling multiple solutions for the Laserview position to be determined, in which case, the system controller  24  selects an optimal position given the clinical task/procedure to be performed as indicated to the system  10  by the operator. The Laserview can be reached by the movement of the gantry  32  alone, provided that it has 2 rotational and 3 translational degrees of freedom such as the Discovery IGS 740 from GE Healthcare. However, many implementations will have the gantry  32  provide the 2 rotational degrees of freedom and the patient support/table  34  provide the 3 translational degrees of freedom. 
         [0039]    In determining the Laserview configuration for the source  12  and detector  22 , the system controller  24  additionally determines which laser  50  should be aligned to the trajectory  64  based on whether the position for the detector  22  at that trajectory  64  is reachable or not due to potential interference/collisions, for example between the detector  22  and/or tube  12  and the patient  18  and/or table  34  on which the patient is positioned and in order to optimize the access of the physician  62  at that trajectory  64 , as shown in  FIG. 3  in comparison with a prior art system  10 ′ including a source  12 ′, an X-ray beam  20 ′ emitted from the source  12 ′ and a detector  22 ′. As illustrated, the system  10  including the laser  50  allows the detector  22  to be used to reach targets T using paths which would not have been possible with prior art systems  10 ′. Further, with more lasers  50  disposed on the detector  22 , the span of reachable angles or trajectories  64  is increased. Further, the step in block  100  can be performed completely automatically by the system controller  24 , by inputs from the physician  62  to the system controller  24 , or a combination thereof. 
         [0040]    After the Laserview to be utilized in the procedure has been determined, in block  102  the system controller  24  can optionally operate rotational subsystem  26  to position the source  12  and the detector  22  in a Bull&#39;s-eye view configuration relative to the trajectory  64  where the target T is centered in the image, if this view is reachable. At this position one or more images are taken at this position to verify the location of the target T and that the patient  18  has not moved thereby confirming the trajectory  64 . If the Bull&#39;s eye view is not reachable, other suitable views such as two orthogonal views can be used. 
         [0041]    Once the position of the target T and patient  18  has been confirmed, the method proceeds to block  104  where the system controller  24  moves the source  12  and detector  22  back to the Laserview configuration where the physician places the tip  61  of the interventional device/needle  60  at the entry point  63  indicated by the beam  58  emitted from the laser  50 . 
         [0042]    In block  106  the physician then moves the device  60  in order to align the device  60  with the trajectory  64  indicated by the angles of the beam  58  relative to the entry point  63 , while keeping the tip  61  on the entry point  63 , schematically shown in  FIG. 4 . In block  108 , once the device  60  has been positioned at the entry point  63  along the planned trajectory  64 , the physician  62  then inserts the device  60  into the body of the patient  18 . These steps can be readily accomplished as shown in  FIG. 3  where the tip of the device  60  is placed at the entry point  63  while the hands of the physician  62  remain outside of the X-ray beam  20 . In addition, the laser beam  58  can be readily and easily viewed due to the unobstructed view of the trajectory  64  indicated by the laser beam  58  based on the offset position of the laser  50 . 
         [0043]    As the physician is inserting the device  60  into the patient  18 , upon the request of the physician, in block  110  the system controller  24  can position the gantry  32  and/or table  34  at the Laserview or Progress view. In doing so, the system controller  24  can take one or more additional images of the patient  18  in order to display the position of the tip of the device  60  relative to the trajectory  64  and to the target T. In the Laserview configuration, with the only assumption being that the device  60  is inserted at the entry point  63  and aligned with the laser beam  58 , the system controller  24  can readily illustrate to the physician the three-dimensional position and depth of the device  60  along the trajectory  64  simultaneously with the physician holing the device  60  to assist in guiding the device  60  to the target T. This can be shown to the physician on the display  42 , optionally with the image taken in the Laserview position used as an overlay over a three-dimensional image of the planned trajectory through the patient  18  compiled from prior images. From this combined image, the system controller  24  can indicate to the physician the exact position of the device  60  in the patient  18 , accuracy of the insertion of the device  60  along the trajectory  64 , can identify any corrections that need to be made to the device  60  placement, and can display the remaining distance between the device  60  and the target T, among other suitable information concerning the procedure. 
         [0044]    Alternatively, where the image is obtained in a Progress view configuration for the source  12  and detector  22 , the system controller  24  moves the gantry  32  to the appropriate position to obtain the Progress view image, and then optionally returns the gantry  32  to the Laserview position. The Progress view image can then be used by itself or with the three-dimensional trajectory planning image to enable the physician to see the device  60  as it is being manipulated and its position in the patient  18  relative to the planned trajectory  64 . Also, switching between these view configurations can provide access to more information at a lower dose while maintaining the accuracy. 
         [0045]    After insertion of the device  60  in block  110 , or as another check prior to the insertion of the device  60 , the physician can request that the system controller  24  perform a check on the position of the patient  18  in order to determine that the patient  18  is still in the proper position relative to the planned trajectory  64 . To do so, in block  112 , upon the request of the physician, the system controller  24  operated the gantry  32  and/or or the table  34  to place the source  12  and detector  22  in one or more suitable views, potentially including the Bull&#39;s-eye view configuration. The system controller  24  then operates the source  12  and detector  22  to obtain an image is taken of the target T and check that the target T is at the proper location relative to the planned trajectory  64 . 
         [0046]    The written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.