Patent Description:
Imaging systems may acquire image data of a subject. The image data may be used to generate images. The images may be displayed for viewing by a user and/or further analyzed and/or augmented for various purposes. The images may illustrate a selected portions of a subject.

An imaging system that acquires image data of the subject may acquire a plurality of image data projections of the subject. The plurality of projections may be acquired at a plurality of positions of the imaging system relative to the subject. For example, a system may include an arm or a projector that moves in space relative to a subject to acquire a plurality of positions of image projections relative to the subject.

<CIT> discloses a method for image stitching. The method may include obtaining a reference image of a first portion of a subject and a target image of a second portion of the subject, and determining at least one pair of feature points based on a preliminary registration accuracy. The first and second portions may at least partially overlap with each other. Each pair may include a reference feature point in the reference image and a target feature point in the target image that matches the reference feature point. For each pair, the method may further include determining an updated pair of feature points based on a superior registration accuracy higher than the preliminary registration accuracy and a neighboring region of the target feature point of the pair. The method may further include generating a stitched image based on the at least one updated pair.

<CIT> discloses apparatus and methods for merging of overlapping two-dimensional (2D) images which are formed by an image pick-up device as projections of a three-dimensional (3D) scene. In particular, the merging includes image registration by projective transformation of one of the 2D images, the transformation being derived from corresponding feature found in both images. In order to achieve improved accuracy and stability, the coordinates of the corresponding feature points are chosen or are translated so that, on average, the numerical ranges of coordinate values are minimized. Apparatus of the invention includes an appropriately configured image processor or computer with an attached image acquisition device, which in one embodiment, is a diagnostic x-ray apparatus.

The invention provides a method of generating a combined image from a plurality of image data according to claim <NUM> and a system to generate a combined image from a plurality of image data according to claim <NUM>.

Generally, an imaging system may include a portion that moves relative to a selected position. A subject may be placed at the position for acquiring image projections thereof. The imaging system may acquire one or a plurality of image projections, including image data, at a plurality positions relative to the subject.

The plurality of image projections may be acquired to generate images of views of the subject at a plurality of positions, including a plurality of locations and/or a plurality of orientations. For example, the imaging portion of the imaging system may translate axially (i.e., along a Z-axis) relative to the subject to acquire an image projections at a plurality of positions along the axis. As the imaging portion moves, the imaging portion may move relative to the subject or a selected pose relative to the subject. For example, the imager may change a positioned in at least one degree of freedom other than movement along the Z-axis. For example, the imaging system may tilt, rotate, sag, etc. Accordingly, a system, such as a system including a processor module, may evaluate the image data and/or additional data signals to determine an alignment for generating a composite or combination image based upon the plurality of image projections of the subject.

<FIG> is an environmental view of a procedure system that may be used during a procedure during which an instrument, such as a powered drill assembly <NUM>, may be used by a user <NUM>, to perform a procedure on a subject (e.g. a patient) <NUM>. In various embodiments, the powered drill assembly <NUM> may include a powered dissection tool <NUM> for performing a select procedure, such as forming a burr hole in a cranium of the subject <NUM>, operating on one or more a vertebra <NUM>, or other selected procedure. The instrument <NUM>, according to various embodiments, may include an appropriate motor component such as the LEGEND MR8® and/or LEGEND EHS STYLUS® motor systems, sold by Medtronic, Inc. The motor component may include a motor that is powered such as a pneumatic powered, such as the LEGEND MR7® motors although other power motors or drives may be used such as electric power motors LEGEND EHS STYLUS® motors. It is understood, however, that the powered drill assembly <NUM> may be used for performing other procedures such as a removal of material relative to and/or in the vertebrae.

For example, the powered drill assembly <NUM> may be operated to remove a portion of the vertebra in a selected procedure, including a laminectomy procedure or other appropriate spinal procedure. Further, it is understood that the powered drill assembly <NUM> may be used to perform a procedure on a non-living subject such as to drill a hole in an airframe, an automotive frame, or the like. Accordingly, the powered drill assembly <NUM> is not required to be used with a living subject, such as a human patient.

The powered drill assembly <NUM> may include a motorized drill that is tracked and/or navigated relative to the subject <NUM> according to various embodiments with various systems and/or for various procedures. A navigation system <NUM> may include a tracking system, as discussed further herein, and may include a tracking device <NUM> that may be connected to the powered drill assembly <NUM> to track a position or pose of a tool relative to the subject <NUM>, such as the vertebra <NUM>. Generally, the pose includes both a coordinate location (such as a location in 3D space) and an orientation (such as at least one or more, including three, degrees of freedom). Thus, a pose or position may include a selected amount of degrees of freedom, such as six degrees of freedom information regarding an object (e.g., the instrument <NUM>). Appropriate tracking systems include those disclosed in <CIT>. It is understood that image data may be acquired of the subject <NUM> to create images, as discussed herein. To acquire the image data, an imaging system <NUM> may be used prior to beginning a procedure or after a procedure has begun, the procedure may include operation of the powered drill <NUM>. The imaging system <NUM> may include an O-arm ® imaging system sold by Medtronic, Inc. and/or may include those disclosed in <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>. The imaging system <NUM>, therefore, may include an annular gantry include an annular volume in which a detector and/or source are rotated around the subject <NUM>. Other possible imaging systems include C-arm fluoroscopic imaging systems which can also generate three-dimensional views of the patient <NUM>, such as the ZIEHM VISION® RFD 3D imaging system sold by Ziehm Imaging GmbH having a place of business at Nuremberg, Germany.

The tracking system may be a part of the navigation system <NUM> to assist in performing selected procedures, such as a surgical procedure on the subject <NUM>, and may include those as generally known in the art. For example, navigation systems may include those as disclosed in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>; and <CIT> and those disclosed in <CIT>. Tracked positions may be displayed on images or relative to images due to registration of a position of a subject or real space to an image space, also as disclosed in the U. patents and publications as mentioned above. Further, tracking systems may include the Stealth Station® S8® tracking system, and AxiEM™ tracking system, all sold by Medtronic Navigation, Inc.

The tracking systems may include various features such as an optical tracking systems, EM tracking systems, ultrasonic tracking systems, or the like. Nevertheless, as illustrated in <FIG>, for example, a tracking system may include one or more localizers that may include portions that include cameras and/or antennas for receiving/and or transmitting a signal for tracking. Localizers may include an optical localizer <NUM> that includes one or more cameras <NUM> that may detect or "view" the tracking device <NUM> connected to the power drill <NUM>. The localizer <NUM> including the cameras <NUM> may emit a selected radiation, such as infrared radiation from emitters <NUM>, that is reflected by one or more trackable portions <NUM> that are associated with the tracking device <NUM>. The trackable portions <NUM> may be viewed by the cameras <NUM> and a signal may be transmitted to a navigation processor unit <NUM>. The navigation processor unit <NUM> may include various features, such as a navigation probe interface (NPI), as discussed further herein. The navigation processor unit <NUM> may also include a coil array controller (CAC) for various types of tracking systems. Various features such as the NPI, the CAC, or other portions may be provided as separate units from the navigation processor unit <NUM> or separate modules for interacting with various portions of the navigation system, as is generally known in the art.

The localizer <NUM> may communicate with the navigation processor unit <NUM> via a selected communication line <NUM>. The communication line <NUM> may be a wired or a wireless communication with the navigation processor unit <NUM>. The navigation processor unit <NUM> may communicate with a selected system, such as a workstation, a terminal, or the like that includes a display system or display module <NUM> having a display screen <NUM> and one or more user inputs <NUM>. It is understood, however, that the display screen <NUM> may be separated for the processor unit <NUM> and/or in addition thereto, such as a projected display, a headset display (e.g., augmented reality systems). The user inputs <NUM> may include a keyboard, a mouse, a touch screen, or other tactical input. Further inputs may also include a foot switch, verbal inputs, visual inputs, or the like.

A subject tracking device <NUM> may also be connected, such as fixed, relative to the subject <NUM>. In various embodiments, the subject tracking device <NUM> may be fixed to one or more of the vertebra <NUM> and/or other portion of the subject <NUM>. Generally, the subject tracking device is fixed relative to a selected portion of the subject <NUM>. In various embodiments, for example, the subject may be fixed to a subject support <NUM> (such as with a mount <NUM>) to which the subject <NUM> is fixed, at least for a selected period. Thus, the subject tracked <NUM> is generally fixed relative to the subject <NUM> at least for a selected period, such as while acquiring image data, during a procedure, etc..

In various embodiments, alternative or additional tracking systems may be provided, such as an electromagnetic tracking systems including an electromagnetic tracking array, such as a coil array <NUM>. The coil array <NUM> may include one or more coil elements <NUM> that emit and/or receive an electromagnetic signal from an electromagnetic (EM) tracking devices, such as the subject tracking device <NUM> associated and/or connected to the patient <NUM> or a tracking device <NUM>' connected to the power drill <NUM>. The coil array <NUM> may communicate with navigation processing unit <NUM> via a communication line <NUM> similar to and/or the same as the communication line <NUM> from the localizer device <NUM> to the navigation processing unit <NUM>. Further, each of the tracking devices may communicate with the navigation processing unit <NUM> via selected communication lines such as communication line <NUM> so that a position of the selected tracking devices, including tracking device <NUM> and tracking device <NUM> may be determined with a navigation processing unit <NUM>. It is understood that one or more than one tracking system may be used simultaneously and/or serially during the selected procedure.

The display screen <NUM> may display an image <NUM> of a portion of the subject <NUM>, such as a vertebra image 36i of the vertebra <NUM>. The image <NUM> may be based on or generated with image data acquired with the imaging system <NUM> as discussed above. Displayed relative to the image <NUM> and/or superimposed on the image <NUM> of the patient <NUM> may be a graphical representation, also referred to as an icon, <NUM>. The icon <NUM> may represent a position such as a pose, of the powered drill assembly <NUM> that may include the tool <NUM>, relative to the subject <NUM>. The represented position may also be of only a portion of the assembly <NUM>. The position of the powered drill assembly <NUM>, or a portion thereof, relative to the subject <NUM> may be determined by registering the powered drill assembly <NUM> relative to the subject <NUM> and thereafter tracking the location of the powered drill assembly <NUM> relative to the subject <NUM>.

Registration may include various techniques, such as those disclosed in <CIT>;<CIT>; <CIT>; <CIT>; and <CIT>; and <CIT>. Generally, registration includes a mapping between the subject space and the image space. This may be done by identifying points in the subject space (i.e. fiducial portions) and identifying the same points in the image (i.e. image fiducials). A map of the image space to the subject space may then be made, such as by the navigation system. For example, points may be identified manually, automatically, or a combination thereof in the image data, such as in the image <NUM>.

Related points may be identified in a subject space, such as defined by the subject <NUM>. For example, the user <NUM> may identify a spinous process in the image <NUM> and an instrument tracked by one or more of the tracking systems, including the localizers <NUM>, <NUM>, may be used to identify a spinous process at the vertebrae <NUM>. Once an appropriate number of points are identified in both the image space of the image <NUM> and the subject space of the subject <NUM>, a map may be made between the two spaces. The map allows for a registration between the subject space defined by the subject, also referred to as a navigation space, and the image space defined by the image <NUM>. Therefore, the instrument, or any appropriate portion, may be tracked with a selected tracking system and a poise of the instrument may be identified or represented relative to the image <NUM> with the graphical representation <NUM>.

As discussed above, registration of the powered drill assembly <NUM> relative to the subject <NUM>, such as with or to the subject tracking device <NUM>, may be made at a selected point in a procedure. The image <NUM> may then be displayed on the display screen <NUM> and a tracked location of the powered drill assembly <NUM> may be displayed as the icon <NUM> relative to the image <NUM>. The icon <NUM> may be superimposed on the image <NUM> to display a pose of at least a selected portion of the powered drill assembly <NUM>, such as a distal end, of the tool <NUM> powered by the powered drill assembly <NUM>. As briefly noted above, the pose or position may include a location that includes three degrees of freedom in space (for example, including at least one of a XYZ position) and a selected number (e.g., three) degrees of freedom orientation information location (for example, including at least one of yaw, pitch and roll orientation). The pose may be determined and/or calculated by the navigation processing unit <NUM> and communicated to the display device <NUM> via a selected communication line, such as a communication line <NUM>. The communication line <NUM> may be a wired or wireless or other appropriate communication line.

Further, it is understood that the navigation processor unit <NUM> may include various features such as a selected processor (e.g., an application specific integrated circuit (ASIC), general purpose processor or the like). The navigation processor unit <NUM> may also include a memory system (e.g., non-transitory memory systems including spinning hard disks, non-volatile solid state memory, etc.) that includes selected instructions, such as those to perform the tracking, registration, superimposing of the icon <NUM> on the image <NUM>, or the like. Therefore, the determined pose of the powered drill assembly <NUM> (for example the selected portion of the powered drill assembly <NUM>, as discussed further herein), may be displayed relative to the subject <NUM> by the icon <NUM> relative to the image <NUM>. The user <NUM> may then be able to view the display screen <NUM> to view and/or comprehend the specific pose of the selected portion of the powered drill assembly <NUM> relative to the subject <NUM> by viewing the display <NUM>.

With continued reference to <FIG> and additional reference to <FIG>, the imaging system <NUM>, also referred to as an imager, may include a plurality of portions, such as a first or base portion <NUM> and a gantry or movable portion <NUM>. The gantry portion <NUM> may be movable relative to the subject <NUM> and/or the base <NUM>. The gantry <NUM> may move, for example, such as between a first position 134i and a second or final position 134n. It is understood, as illustrated in <FIG>, <FIG> that the gantry <NUM> may move between the initial position 134i and a final position 134n. Although two positions are illustrated, a plurality of positions greater than two positions may be used. For example the gantry <NUM> may move through a total of three positions, four positions, or any appropriate number of positions to acquire image data of the subject <NUM>. Thus, one or more intermediate positions may be determined for movement of the gantry <NUM>, although they are not illustrated. The intermediate position(s) may be between the first position 134i and the final position 134n, and/or outside of the first position 134i and the final position 134n. The gantry <NUM> may, for example, include a maximum range of movement relative to the console or base portion <NUM> and an appropriate number of movements or positions of the gantry <NUM> may be selected or achieved to ensure image data acquired at all possible positions or enough image data is acquired to achieve a selected final image for display with the display device <NUM>. For example, the positions of the imaging system <NUM>, including the gantry <NUM> (e.g., the first, final, and any possible selected intermediate positions), for collection of image data may be selected and/or determined based on a selected dimension of a combined image, as discussed herein.

As illustrated in <FIG>, <FIG>, the gantry <NUM> may be at different positions relative to the subject <NUM> at the different gantry positions 134i, 134n. For example, the subject <NUM> may extend along an axis <NUM>. It is understood that the axis <NUM> may be of the subject <NUM> or any appropriate axis that may be define a reference axis or plane for movement of the gantry <NUM>. The axis <NUM> may also be reference to as a Z-axis that may be used to define or determine at least one degree of freedom of movement of the imaging system <NUM>. Relative to the axis <NUM> may be a perpendicular axis <NUM>. The perpendicular axis <NUM> may be perpendicular to the long axis <NUM> and/or perpendicular to a floor or surface <NUM>, such as a floor on which the console <NUM> is positioned and/or fixed. Further, the subject <NUM> and the axis <NUM> may be fixed relative to the surface <NUM>.

As illustrated in <FIG>, the gantry <NUM> at the initial position 134i may extend along or define an axis <NUM> that is at a first angle <NUM> to the axis <NUM>. At the final position 134n, the gantry <NUM> may extend along or define an axis <NUM> that is at a second angle <NUM> relative to the axis <NUM>. As illustrated in <FIG>, the first angle <NUM> at the position 134i and the angle <NUM> at the second position 134n may differ. Accordingly, as discussed further herein, image projections acquired at the first position 134i may differ, such as not being aligned along the Z-axis, from those acquired at the second position 134n.

Additionally, with reference to <FIG>, the gantry <NUM> may also be at other orientations at the first position 134i and the final position 134n. The console <NUM> and the gantry <NUM> may be viewed from a top view, as illustrated in <FIG>, and viewed relative to an axis <NUM> that extends perpendicular to the axis <NUM> through the subject, but parallel to the base or floor <NUM>. The gantry <NUM> in the first position 134i may extend along an axis <NUM> that forms a first angle <NUM> relative to the axis <NUM> and the gantry <NUM> at the second position 134n may extend along or oriented along an axis <NUM> that extends at a second angle <NUM> relative to the axis <NUM>. As illustrated in <FIG>, the angle <NUM> may differ from the angle <NUM> and/or position the gantry <NUM> at a different orientation relative to the subject <NUM>, such as the axis <NUM>.

As illustrated in <FIG>, therefore, it is understood that the gantry <NUM> may be at a different positions relative to the subject <NUM> to acquire a plurality of image projections of the subject <NUM>. The different projections according to the different orientations may, therefore, differ and not be initially aligned relative to each other, as discussed further herein.

It is also understood, however, that various other movements of the gantry <NUM> may occur during an acquisition of projections at a plurality of positions. For example, the gantry may move, such as "wobble" due to a weight distribution of the gantry <NUM> relative to the based <NUM>. Further, the gantry <NUM> may move in other ways due to movement of the gantry <NUM> to acquire the plurality of projections along a length or along the axis <NUM> of the subject <NUM>. Accordingly, the movement of the gantry <NUM> as illustrated in <FIG> is merely exemplary of a process discussed further herein.

With continued reference to <FIG>, <FIG>, the subject or patient tracker (DRF) <NUM> may be tracked relative to the subject <NUM> for a selected period with the navigation system <NUM> including the relevant or appropriate tracking system. The tracking system including the respective localizers <NUM>, <NUM> may be used to track the DRF <NUM> during a selected procedure and/or for a period of time. Further, the tracking systems may track other appropriate tracking devices, such as the tracking device <NUM> associated with the instrument <NUM>. In addition, a tracking device, also referred herein to as an imaging tracking device <NUM>, may be associated with the gantry <NUM>. The tracking device <NUM> may be tracked with the respective tracking system included with the navigation system <NUM>. Therefore, the position of the gantry <NUM> may be determined with the navigation system <NUM>, similar to determining a position of the various other instruments or portions with respective tracking devices. In various embodiments, for example, the tracking device <NUM> may be tracked relative to the subject tracking device <NUM> during the selected procedure, such as acquiring image data of the subject <NUM>. This allows the position of the gantry <NUM> to be determined relative to the subject <NUM>, where the position of the subject <NUM> may be determined based upon the position of the patient tracker <NUM>.

The position of the gantry <NUM>, therefore, may be determined at a plurality of positions relative to the subject <NUM>. As discussed above, the gantry <NUM> may move between at least the positions 134i and 134n and/or other selected or determined intermediate positions. The position of the gantry <NUM> may be tracked at both the gantry positions 134i and 134n. Thus, the position, which includes location and orientation of the gantry <NUM>, may be determined at a plurality of positions relative to the subject <NUM>. As discussed above, image data may be acquired of the subject with the imaging system <NUM> at the plurality of positions of the gantry <NUM>. The positions of the gantry may change, such as by the various angle and/or translational position relative to the subject <NUM>.

With continued reference to <FIG> and additional reference to <FIG>, the imaging system <NUM> may acquire a plurality of projections through the subject <NUM>. In various embodiments, the imaging system <NUM> may include a x-ray imaging system that may acquire a plurality of projections of the subject <NUM>. The imaging device <NUM> may acquire a plurality of projections that may be two-dimensional projections and/or three-dimensional image or image data. For example, image data at each position may include a three-dimensional image projection or reconstruction based on a plurality of two-dimensional image data.

Further, the plurality of projections may be combined in a selected manner, as discussed further herein, to generate a selected image such as a three-dimensional image, a long film image, or the like. In various embodiments, a long film image may be an image that is longer than what is acquired with a single acquisition projection through the subject <NUM> with the imaging system <NUM>. Accordingly, a plurality of projections or images may be combined to form a combination image in a selected manner, such as "stitched" together to form a long film.

With reference to <FIG>, for example, the imaging system <NUM> may acquire a first image projection <NUM> and a second image projection <NUM>. Both of the image projections may have a selected dimension <NUM>. The dimension <NUM> may be about <NUM> centimeters (cm) to about <NUM>, including about <NUM> to about <NUM>, and further including about <NUM>. The selected projections <NUM>, <NUM> may have the dimension <NUM> that is determined or a maximum dimension based upon the imaging system <NUM>. For example, a detector of the imaging system <NUM> may have a maximum dimension that is the dimension <NUM> or allows a maximum projection dimension of <NUM>. Any single one image projection of the subject <NUM> may be limited by the physical dimensions of the imaging system <NUM>.

As illustrated in <FIG>, the two projections <NUM>, <NUM> may include selected portions of the subject, such as vertebrae <NUM>. For example, the first projection <NUM> may be acquired at the position 134i. The projection <NUM> may include selected vertebrae such as a first vertebrae <NUM><NUM>, <NUM><NUM>, and <NUM><NUM>. The three vertebrae <NUM><NUM>, <NUM><NUM>, and <NUM><NUM> may be viewed in the projection <NUM> that is acquired with image data that may be acquired with the gantry <NUM> in a selected first position, for example the position 134i. The second projection <NUM> may include a selected number of vertebrae, such as the vertebrae <NUM><NUM> and <NUM><NUM>. The second projection <NUM> may further include the vertebrae <NUM><NUM>. Accordingly, the second projection <NUM> may include additional image data that is then included in the first image <NUM>. Further, the second image <NUM> may not include image data that is in the first projection <NUM>, such as a portion of a sacrum S of the subject <NUM>. As discussed further herein, the two images <NUM>, <NUM> may be stitched together in a selected manner, as discussed further herein, to obtain an image that includes a dimension greater than the dimension <NUM>.

The two images <NUM>, <NUM> are acquired with the gantry <NUM> that may be initially selected to have only be linearly displaced from each other, such as along the axis <NUM> (Z-axis). Movement of the gantry <NUM>, however, may create the projections through the subject <NUM> at slightly different positions that are not only due to a direct translation or straight translation along the axis <NUM>. As discussed above, the gantry <NUM> may include a plurality of positions relative to the subject <NUM>, such as due to a movement at an angle relative to the axis <NUM> and/or the surface <NUM>. As discussed above, the gantry <NUM> may be moved to selected positions including the first position 134i and the second position 134n that are not a straight linear translation along the axis <NUM>. Therefore, while the two projections <NUM>, <NUM> may initially include image portions that are along the axis <NUM> they may differ from one another, such as due to or by a distance <NUM> exemplary illustrated between a first line or plane <NUM> and a second line or plane <NUM>. It is understood that the distance <NUM> is merely exemplary, and that the difference between the two projections <NUM>, <NUM> may be due to any movement of the gantry <NUM> including a vertical translation away from or toward the surface <NUM>, a rotation or angle change relative to the axis <NUM> and/or the surface <NUM>, or other appropriate difference. Therefore, the gantry <NUM> may not only move in a linear translational along the axis <NUM> to acquire the multiple projections <NUM>, <NUM>, but may include other movement relative to the axis <NUM>. The relative movements may generate projections that include the spatial difference <NUM> between the two projections <NUM>, <NUM>.

It is understood that the number of projections may be any appropriate number of rejections such as one or at least one projection acquired at each position of the gantry <NUM>. Therefore, the illustration of two projections <NUM>, <NUM> is merely exemplary for the current discussion. Further the type of movement may be a complex movement that includes both a rotational movement and a translational movement other than along the axis <NUM>. For example, the gantry <NUM> may both rotate relative to the axis <NUM> and include a vertical movement relative to the surface <NUM> and the axis <NUM>. Accordingly a complex or plurality of movements may occur during the acquisition of a plurality of image projections of the subject <NUM> with the imaging system <NUM>.

In various embodiments, however, the navigation system <NUM> may track or determine a position of the gantry <NUM> at each or during each image acquisition or image data acquisition. During the acquisition of the first projection <NUM>, the gantry tracking device <NUM> may be tracked and the position determinative of the navigation system <NUM>. Similarly during the acquisition of the second projection <NUM>, the gantry tracking device <NUM> may be tracked to determine a second position of the gantry <NUM> during the acquisition of the second projection <NUM>. The position of the imaging portion of the gantry <NUM> may be known relative to the position of the gantry <NUM>, therefore the position of the gantry that is tracked may be used to determine the position at various acquisitions.

As noted above, the image projection <NUM> or image data <NUM> may be acquired with the imaging system <NUM>. The projection <NUM> may be acquired with a gantry at the initial position 134i. As discussed above the imaging system <NUM> may include the imaging system tracker <NUM>. The imaging system tracker may be tracked with a navigation system <NUM> to allow for a determination of a pose or position of the gantry <NUM> relative to the patient tracking device <NUM> during acquisition of the projection <NUM>. The position during the acquisition of the projection <NUM> may be noted and saved with the navigation system <NUM> and/or appropriate system, such as with a memory associated with a processor system <NUM>, such as a memory <NUM>. Therefore, the image projection <NUM> may have a determined and stored pose of the gantry <NUM> during the acquisition thereof. Similarly, the tracking system may track a position of the gantry <NUM> during the acquisition of the second projection <NUM>, such as in the position 134n. The position of the gantry <NUM> during the acquisition of the second projection <NUM> may also be stored with the imaging system or the navigation system <NUM>, as discussed above.

As is understood by one skilled in the art, the imaging system tracking device <NUM> may be tracked as may be the patient tracking device <NUM>. Accordingly, a position or pose of the gantry <NUM> may be determined relative to the patient tracker when in the first position, such as schematically illustrated by the line <NUM> and a position when the gantry is in the second position 134n may be determined such as schematically illustrated by the line <NUM>. Thus, the position of the gantry <NUM> during the acquisition of the plurality of projections through the subject <NUM> may be known or determined during the acquisition of the projections. Each of the projections, such that the projections <NUM>, <NUM> may include the position information regarding the gantry <NUM>, as noted above. It is understood, as discussed above, that the number of acquisitions and/or positions of the gantry may be any appropriate number and two is illustrated merely for the current discussion. Further, it is understood that any appropriate amount of position data and projections may be acquired at any one of the positions of the gantry relative to the subject <NUM>.

With reference to <FIG>, at each position of the gantry for acquisition of image data 134i, 134n the position of the patient tracker <NUM> may be determined and the tracked position of the imaging system tracker <NUM> may be determined. Accordingly, the schematic line <NUM> may be understood to be a transformation or a correlation of a tracked position of the patient and a tracked position of the imaging system at the first position 134i. Similarly the schematic line <NUM> may be understood to be a tracked position of the patient relative to or transformed to a tracked position of the imaging system at the second position 134n. Accordingly, a determination of a position of the imaging system relative to a reference, such as the axis <NUM>, and the subject <NUM>, may also be determined at each of the gantry positions. This also allows for each of the projections <NUM>, <NUM> to be registered to the subject <NUM>, as noted above, at least because the position of the imaging system and the subject <NUM> are determined and known for each projection <NUM>, <NUM>.

The position of the gantry <NUM> at the first position 134i may include or be determined relative to the axis <NUM> and may be an orientation of the gantry <NUM> relative to the axis <NUM> at the angle <NUM>. The axis <NUM> of the gantry <NUM> may be tracked to determine with the navigation system <NUM> while acquiring the projection <NUM>. Similarly, the axis <NUM> may be determined relative to the axis <NUM> by tracking the gantry <NUM> by acquiring the second projection <NUM>. The angle <NUM> may include or illustrate a portion of the position information relative to the axis <NUM> and may identify a difference of position between the first position of the gantry 134i and the second position of the gantry 134n. It is understood, however, that the gantry tracking device <NUM> may allow for tracking of the gantry <NUM> and all position information.

At each of the positions, therefore, a transformation of the tracked position of the patient with the patient tracker <NUM> to the tracked position of the gantry <NUM> may be made. As illustrated in <FIG>, therefore, two transformation or correlations of the position of the patient and the position of the gantry <NUM> may be determined. Further, at each of the positions of the gantry 134i, 134n a transformation or correlation of a position of the gantry <NUM> relative to a reference, such as the axis <NUM> may be determined therefore a first transformation or position may be determined at the first gantry position 134i and a second transformation or position may be determined at the second gantry position 134n.

According to various embodiments, therefore, a transformation of the position of the gantry during the acquisition of the projections may be made. The projection <NUM> may be transformed to the position of the image <NUM>, or vice versa. Such a process allows for combining various images and correcting for or removing distortion or error due to a non-linearity of the acquisition of the images. The transformation allow for aligning the two projections, <NUM>, <NUM> as discussed further herein.

For example, a transformation of the first position of the gantry to the second position of the gantry may be determined such as using auto-registration systems or techniques such as those included with the StealthStation® S8 navigation system, sold by Medtronic, Inc. having a place of business in Minnesota. For example, with reference to Equation <NUM>: <MAT> Where TISiISn represents a transformation of the position of the gantry at the first position 134i (ISi) and the position of the gantry of the second position 134n (ISn). This may be determined by combining the various correlations or transformations of the patient to the imaging system. This may include a product of TISRi that is a determination or transformation of the tracked first position of the gantry and the determined position of the gantry, an inverse of TISPi that is a transformation of a tracked position of the patient and a tracked position of the imaging system at a first position, a transformation TISPn of a tracked position of the patient at the second position to a tracked position of the imaging system at the second position, and an inverse of TISRn which is a position of the imaging system at the second position transformed to a tracked position of the imaging system.

With continued reference to <FIG> and additional reference to <FIG>, a method <NUM> of acquiring image data, such as the first projection <NUM> and the second projection <NUM> and determining and/or correcting for movement or positions of the gantry <NUM> that is in addition to a predetermined selected movement, such as a linear or straight translation relative to a reference, such as the translation along the axis <NUM> (Z-axis). It is understood that the gantry <NUM> includes various imaging systems, as described above, and therefore reference to movement or the positioning of the gantry may be understood to include and/or refer to movement or positions of the imaging portions that acquire the image data of the subject <NUM>.

The method <NUM> may be initiated by the user <NUM> in a start block <NUM>. The start block <NUM> may include various procedures, such as preparing the subject <NUM>, attaching the patient tracker <NUM> relative to the subject <NUM>, initiating the navigation system <NUM>, or other appropriate procedures or steps. Nevertheless in the start block <NUM> the method <NUM> may be initiated to acquire in a line image data.

The method <NUM> includes various processes or steps that may be further subdivided such as a first subroutine or process of an initial registration and image acquisition subprocess or subroutine <NUM>. The subprocess <NUM> may include various portions that may occur in any appropriate manner and/or order is understood by one skilled in the art. The subject <NUM> may be tracked at the initial gantry position 134i in block <NUM>. The tracking of the subject at the initial position in block <NUM> may include tracking the subject tracker <NUM> when the gantry <NUM> is in the initial position 134i. Additionally, the imaging system may be tracked at the initial position in block <NUM>. Tracking the imaging system (IS) at the initial position may also be performed with the navigation system <NUM> that includes the various tracking systems and may be used to track the IS tracking device <NUM>. Accordingly, the subject <NUM> may be tracked at the initial position in block <NUM> and the imaging system <NUM> may be tracked in the initial position of block <NUM>. The imaging system <NUM> may acquire image data at the initial position in block <NUM>. The initial image data projection may include the projection <NUM> as discussed above. Accordingly, the image data may be acquired at a tracked position of the subject <NUM> and a tracked position of the imaging system <NUM>, including the gantry <NUM>. Thus, the image data is acquired at the initial position 134i may have associated therewith the tracked position of the subject block <NUM> and the tracked position of the imaging system in block <NUM>.

As discussed above, the imaging system <NUM> may be used to acquire a plurality of projections of the subject. As illustrated in <FIG> the process <NUM> exemplary illustrate the acquisition of initial image data in block <NUM> and a second subprocess to acquire subsequent image data referred to as "n". It is understood that any appropriate number of projections may be acquired and that a second image acquisition subprocess <NUM> may refer to a second or any appropriate number of image projections. Accordingly, the process <NUM> may be used to acquire a selected number of projections to generate a final image volume of a selected dimension, such as length, of the subject <NUM>. In various embodiments, as discussed above, the vertebrae <NUM> may be imaged and the length of the image may be selected to include a selected number of the vertebrae <NUM> of the spinal column of the subject <NUM>. It is further understood that an image acquisition may be used to acquire additional image data, such as portions of a pelvis, sacrum S, leg bones, or the like. Nevertheless the subprocess <NUM> may include the acquisition of any appropriate number of projections in addition to the initial projection.

The subprocess <NUM> may include tracking the subject at a position n in block <NUM>. The position n may be any appropriate position other than the initial position, such as a position after the initial position and may include the second position, a third position, or any appropriate position. As used herein, therefore, "n" may refer to any appropriate position. The imaging system may be tracked at the position n at block <NUM>. The imaging system <NUM> may acquire image data of the subject in block <NUM>. The position of the imaging system in block <NUM> may be the position of the gantry 134n as discussed above. As exemplary illustrated in <FIG>, the imaging system may have an initial position 134i and a second position or "n" position 134n. The subprocess <NUM> may include the acquisition of the image data at the 134n position such as the second projection <NUM>, while tracking the subject <NUM> in block <NUM> and the gantry in block <NUM>. Accordingly, the imaging system <NUM> may be used to acquire a plurality of projections such as an initial projection and other, including subsequent, projections with a tracked position of the gantry <NUM> and the subject <NUM> during the acquisition of the image data.

As discussed herein, due to the tracking of the imaging system, including the gantry <NUM> and the subject <NUM> while acquiring the image data, the acquired image data projections are registered to the subject. Thus, the image data <NUM>, <NUM> may be used to define a coordinate system that is registered (i.e., transformed) to a subject space defines by the subject <NUM>.

The tracked information regarding the subject <NUM> and the gantry <NUM> may be used to determine movement of the imaging system, generate a stitched or combined model or image of the subject <NUM> based on or including a plurality image data acquisition at a plurality of positions of the imaging system including the gantry <NUM>. The tracked information and the acquired image data may then be further analyzed at any appropriate time, such as after each of the individual image data acquisitions. It is further understood, the process <NUM> need not occur in the specific order of acquiring the image data and the subprocesses <NUM>, <NUM> prior to any registration and/or transformation, such as generated in a transformation subprocess <NUM>.

The subprocess <NUM> may be referred to as a transformation or correction process by evaluating the tracking information of the subject and the imaging system of the various subprocesses <NUM>, <NUM> discussed above. For example, an evaluation of the tracked position of the imaging system at position i may be made, such as its position relative to a selected reference, which may include the axis <NUM> in block <NUM>. Further, an evaluation of the tracked position of the imaging system may be made relative to the subject at position i in block <NUM>. The evaluation of the tracked position of the imaging system at the initial position i relative to the subject <NUM>, such as with the patient tracker <NUM>, may be used to determine a transformation of the imaging system to the subject TISPi in block <NUM>. The transformation TISPi may be made to transform a position of the imaging system, such as the gantry <NUM> to the subject <NUM>. The transformation TISPi may optionally be stored for further recall or later recall in block <NUM>. The initial imaging system to patient transformation may be used as a reference for later transformations. In other words, later image data may be aligned to the initial image data for further processing, such as combining the plurality of image data. It is understood, however, that any appropriate transformation may be used as a reference as discussed further herein.

Further in the transformation subprocess <NUM>, an evaluation regarding the tracked position of the subject and the imaging system at the position n may also be made in block <NUM>. An evaluation of a tracked position of the imaging system relative to a reference, such as an imaging plane including the axis <NUM> may also be made in block <NUM>. A transformation TISPn may be determined of the imaging system (IS) to the subject at the second or other position "n" when the second image data is collect in block <NUM>. The transformation may be similar to that discussed above regarding the initial position, but regarding the later or second positions, as noted above, identified as "n". After determining the transformation of the imaging system to the subject at the position n, the transformation may be stored, optionally, in block <NUM>. As discussed above, storing various data may include storing in the memory system <NUM>, and/or any appropriate memory system. The selected processing system, such as the processor system <NUM>, may then recall the data from the selected memory for further analysis, such as by executing selected instruction that may be included in various applications, programs, or the like.

With the evaluated and/or stored data regarding the tracked positons of the imaging device and the subject for each of the image data acquisitions, transformations regarding the position of the gantry <NUM> to the tracked position may be made based upon an evaluation of the position of the imaging system at positions i and n to a selected reference, such as from blocks <NUM>, <NUM>. Thus, a determination of a transformation of the imaging system to the reference axis or portion at the initial position TISRi may be made in block <NUM> and a determined transformation of the imaging system to reference axis or plane at the second or other positions TISRn may be made at block <NUM>. Again, the transformations may be optionally stored in a selected memory system in block <NUM>. In this manner, the transformations of the imaging system, such as the gantry <NUM>, to the subject may be determined and/or recalled to allow for a correction of a unselected misalignment of the plurality of image data at the various positions relative to each other. Thus, transformations of the imaging system to a reference axis at the various positions, such as i and n, (TISRi and TISRn) may be used for further analysis of the image data.

Based upon the various transformations discussed above, the image data acquired at the various positions may be aligned to allow for a stitching or combination of the various images to a combined or final image or image data that is a long image relative to the individual projections. As discussed above and illustrated in <FIG>, each of the projections <NUM>, <NUM> may include a selected length <NUM> of the subject. The length <NUM> may be substantially identical to the two images based upon the position of the image or gantry <NUM> and various geometries thereof. Further, each of the image projections may include a selected overlap <NUM>' that may overlap between subsequent or selected images. The combination of the images may include a total length that is greater than an initial length, such as a combined or stitched image <NUM>, as illustrated in <FIG>, and which may also be illustrated as the image <NUM>. The image <NUM> may include a dimension <NUM> that is generally along the same axis as the dimension <NUM> of the projections <NUM>, <NUM>. The dimension <NUM> may be greater than the dimension <NUM> and may include all selected portions of the subject <NUM> as selected by the user <NUM>. For example, the composite of stitched image <NUM> may include four of the vertebrae <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, and <NUM><NUM> and other portions of the anatomy, such as the sacrum S. Thus, the stitched image <NUM> may include a greater amount of image data than may be acquired with any one of the projections of the imaging system <NUM>.

The imaging system, as noted above, may acquire a plurality of projections, such as the projections <NUM>, <NUM>. These may be stitched together to form the stitched image or model <NUM>. It is understood, that the stitched image <NUM> and the individual selected projections may be two-dimensional, three-dimensional, or otherwise reconstructed into a three-dimension from a plurality of two-dimensional projections. In various embodiments, for example, the imaging system <NUM> may acquire a plurality of projections at each of the positions, such as the initial position 134i and the second position 134n and generate a three-dimensional model regarding the subject at each position. The individual projections may be two-dimensions and/or the three-dimensional models that may then be stitched to form the final or selected to stitch image or model <NUM>, as illustrated in <FIG>. Thus, it is understood that the stitched image <NUM> may be two-dimensional, three-dimensional, or any of the appropriate dimensions. The various transformations determined in the process <NUM> may be used to transform the various image data, including reconstructions based thereon at each of the selected positions, to a selected reference frame to allow for generation of the stitched model <NUM> that does not include artifacts or errors due to the movement of the imaging system <NUM> which generates the projections at different positions of the imaging system <NUM> relative to the subject <NUM>, as illustrated in <FIG>.

With continuing reference to <FIG>, an alignment of the image data at position n to the image data at position i may be made based upon a transformation matrix as defined by Eq. <NUM> to determine an orientation or change of the gantry position during the acquisition between the initial position i and the second or subsequent position n in block <NUM>. <MAT> where TISn'->n is the transformation of the corrected position imaging system (IS) to the non-aligned IS position as a product of a transformation of the corrected IS position to the initial IS position and the initial IS positon to the second IS position. The transformation allows for a determination of a transformation matrix that may be determined in block <NUM> as a correction matrix for the current or second image data at position n to the image data at the position i. The correction transformation is illustrated in Eq. <NUM> and accounts for a corrected position of the gantry n' that may also be referred as a virtual corrected positon as illustrated in <FIG> that allows for a transformation of the image at position n. Eq. <NUM>: <MAT> with RISn'->l defining the rotation transform matching the initial and second image data coordinate systems orientation; and TISn'->l defining the translation transform matching the initial and second image data coordinate systems origin. The transformation allows for an alignment of the two image data sets based upon a tracked position of the gantry <NUM> during the acquisition of the image data. With reference to <FIG>, for example, the gantry at the position 134i includes the orientation or position relative to the axis <NUM>, as discussed above. At the second position 134n, the gantry may have a different orientation relative to the axis <NUM>. Although the gantry <NUM> may move generally along the axis in the direction that may also be referred to as the z-axis, the gantry may not maintain a substantially identical orientation relative to the axis <NUM> between the initial position 134i and the second position 134n. Nevertheless, the transformation, as discussed above in the process <NUM>, may allow for a determination of a coordinate system that may be used to transform an orientation of the gantry <NUM> in the same orientation and only translated in the z-direction. The corrected or virtual position may be referred to as 134n' and have the angle <NUM>', as illustrated in <FIG>. Thus, the image data, such as the second projection <NUM>, may be aligned to the image data acquired at the initial position 134i. Once the image data is corrected or a determination of a correction matrix is made in block <NUM> a combination of the image data may be made in block <NUM>.

The combination of the image data at the initial position i and the image data at the second position n may be performed in appropriate manner. In various embodiments, for example, the image data may be stitched together by identifying appropriate or identical portions in stitching the related portions together. Such stitching techniques may include estimating the transformation by registering intrinsic features in both image data (which may include image data volumes) by a method such as, but not limited to, non-parametric, block matching image registration algorithms, fiducial- or image-based 3D image registration, as generally understood in the art. In various embodiments, for example, a weighted stitching process may occur and weights may be determined, optionally, in block <NUM>. As discussed above, the various projections may be acquired with a selected amount of overlap. The amount of overlap may be known due to the known translation along the z-axis. Accordingly, the overlap amount <NUM>' may be known for each of the projections. Along a distance of the overlap a selected weight may be provided or determined for each position along the image. For example, as illustrated in <FIG>, based upon a position of the gantry <NUM> that moves along the axis <NUM>, as discussed above which may refer to a z position or translation, a weight factor may be determined based upon the image data <NUM>, <NUM>. As illustrated in <FIG>, for example, a weight factor 204w for voxels/pixels may increase as the z-position of the overlap and stitching moves closer to the second projection <NUM> and finally includes only voxels/pixels the second projection <NUM>. Conversely a weight for the first projection <NUM> may decrease, as illustrated by wave line 200w, as the z-position moves away from the position of the initial projection <NUM>. Accordingly a weight may be determined in block <NUM> to assist in the blending or stitching to perform or generate a combined image in block <NUM>. It is understood, however, that weighting may not be required and that a selected position may be identified or determined to create a stitching between the two images.

The combined image may then be output in block <NUM>. As discussed above a combined image may include the image <NUM>, which may be displayed as the display image <NUM>. The combined image <NUM> may registered to the subject <NUM> due to the tracking of the subject <NUM> with the subject tracker <NUM> and the tracking of the image system with the imaging system tracker <NUM> during image projection acquisition. Therefore, the image data <NUM>, <NUM> may be individually registered to the subject <NUM> and the combination image or model <NUM> may also, therefore, be registered due to the inherent or included registration of the initial image data and the transformation in light of the navigation or tracked data as discussed above. This allows the combined image to include the dimension <NUM> that may include a selected dimension, such as by the user <NUM> and input to the imaging system <NUM>, of the subject <NUM>. The image <NUM> may be used for a selected procedure, such as a navigated procedure, that may allow for an illustration of the graphical representation <NUM> of the tracked instrument <NUM> relative to the subject <NUM> for the selected procedure. Therefore, an image that have a dimension, e.g., that is longer, than one that may be created with a single projection with the single projection with the imaging system <NUM> may be created and movement of the imaging system other than along a straight line, such as along the axis <NUM> that may also be referred to as the z-axis may be accounted for to create a selected or combined stitched image.

As discussed above, image data acquired of the subject may be corrected due to movement of the gantry <NUM> that is not only in a straight line and along an axis or plane, such as the axis <NUM>. In various embodiments, movement of the gantry may be identified as movement along a z-axis which may be parallel and/or collinear to the axis <NUM>.

In various embodiments, the movement of the gantry may not be only in the z-axis during the acquisition of a plurality of projections through the subject <NUM>. In various embodiments, one or more portions may not be tracked. For example, tracking devices, including one or more of the imaging device tracking device <NUM> and/or the subject tracking device <NUM> may not be present. Further, the navigation systems <NUM> may not be present. It is understood that the image data may, however, be aligned according to various techniques, such as those discussed further herein. It is also understood that the various techniques may be combined, such as combining the navigation as discussed above to assist in aligning a plurality of projections to account for or correct for movement of the imaging device that is not only in a z-axis. Accordingly the navigation process, as discussed above, may or may not be used alone and may be used in combination with other processes, such as those discussed further herein.

Turning reference to <FIG>, two projections, such as a first projection <NUM> and a second <NUM> may be acquired with the imaging system <NUM>. The projections <NUM>, <NUM> may be similar or identical to the projections <NUM>, <NUM>, as discussed above. The projections <NUM>, <NUM> may be acquired without the imaging system being tracked, the subject being tracked, or the use of the navigation system <NUM>. The image projections <NUM>, <NUM> may, therefore, include a misalignment distance <NUM> between lines <NUM> and <NUM>. In each of the projections <NUM>, <NUM> selected vertebrae may be imaged which may be the same or different vertebrae, including the vertebrae <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>. In addition, each of the image projections may include selected features that may be selectively or optionally positioned relative to the subject <NUM>, such as a fiducial member, such as a rod or member <NUM>.

Each of the projections <NUM>, <NUM> may include a selected dimension, such as a length or dimension along the z-axis <NUM>. As discussed above, the dimension <NUM> may be based on or limited on the dimensions of selected portions of the imaging system <NUM>, such as a dimension of the detector, a dimension of the source, or other dimensions of the imaging device <NUM>. Accordingly, the dimension <NUM> may be a dimension that is a maximum dimension of any single projection based upon the imaging system <NUM>. Further, as discussed above, when acquiring the projections a certain amount of overlap, such as an overlap distance <NUM>' may be included in each of the image projections <NUM>, <NUM>. The overlap <NUM>' may include portions that are imaged of the subject <NUM> that are identical or substantially identical between each of the projections. For example, the vertebrae <NUM><NUM> and <NUM><NUM> may be included entirely in both projections. In addition or alternatively a member, such as the rod <NUM> may be included or imaged in both projections. The rod <NUM> may include selected dimensions and geometry that may be predetermined and stored, such as in the memory <NUM>. The imaging system or other selected processing systems, such as the processor <NUM>, may recall the dimensions to assist in further procedures, such as in registration of the two projections <NUM>, <NUM>.

To assist in aligning the projections and to correct for the spatial difference <NUM> that may be called due to movement of the imaging device, such as the gantry <NUM>, various portions in the respective images <NUM>, <NUM> may be identified and registered. For example the rod <NUM> may be imaged and occur in both projections <NUM>, <NUM>, as illustrated in <FIG>. Further, anatomical portions, such as the vertebrae <NUM><NUM> may occur in both of the images <NUM>, <NUM>. These similar or identical portions may identified in both projections. Identification of the portions in both of the projections <NUM>, <NUM> may be made manually, such as by identification by the user <NUM>. In addition or alternatively, automatic identification may occur such as through selected automatic segmentation features or programs, such as model based anatomical segmentation algorithms such as, but not limited to, like deep learning image segmentation or supervised min-cut/max-flow image segmentation algorithms. Also, there may be combinations including the user identifying one or more voxels or pixels and a selected segmentation program identifying identical or similar (e.g., color, contrast gradient, etc.) voxels and/or edges relative to the voxels or selected portions.

In various embodiments, various high contrast features, such as an image of the rod <NUM> and/or other selected features, such as the vertebrae <NUM><NUM> may be identified and segmented in each of the projections <NUM>, <NUM>. Once the selected identical or common features are identified in each of the projections <NUM>, <NUM>, the projections may be registered to one another. The registration may include a transformation of pixels or voxels to align the respective projections <NUM>, <NUM>. The overlap region <NUM>' in each of the image projections <NUM>, <NUM> may be used to perform the alignment. For example, if the rod <NUM> is identified and segmented in both of the two projections <NUM>, <NUM> these pixels or voxels may be aligned and the other pixels and voxels in the projection <NUM>, <NUM> may be transformed or moved in a similar or identical manner to achieve alignment of the entire projection such that the first projection <NUM> can be aligned with the second projection <NUM>. Selected transformations can include non-rigid, affine, and/or rigid transformations. In various embodiments, an entire object need not be imaged in both projections. For example, given a known geometry of the rod <NUM>, only a portion of the rod <NUM> need be imaged in both projections to allow a registration. Further, as discussed above, registration between more than two projections, such as three, four, or more projections, may occur with the similar process.

It is further understood that the projections <NUM>, <NUM> may include two-dimensional data, three-dimensional data, or any appropriate data type. For example, the projection <NUM> may be a two-dimensional image data projection generated by the imaging system <NUM> at a first position, such as the position 134i of the gantry and the second projection <NUM> may also be a two-dimensional at the second position 134n of the gantry. It is further understood, however, that each of the projections <NUM>, <NUM> may be three-dimensional projections or models generated with image data at each of the respective positions 134i, 134n. In various embodiments, the imaging system <NUM> may generate three-dimensional image data by acquiring a plurality of projections relative to the subject <NUM>. Therefore, the projections <NUM>, <NUM> may be three-dimensional and the alignment may be a registration of three-dimensional image data or model between the projection <NUM> and the second projection <NUM>.

With continuing reference to <FIG> and additional reference to <FIG>, a process <NUM> may be used to access and align and combine the projections <NUM>, <NUM>. The process <NUM> may begin in start block <NUM> which may be similar to the start block <NUM>, as discussed above. In various embodiments, the subject <NUM> may be positioned relative to the imaging system <NUM>, such as in preparation for procedure, preparation to acquire image data for various purposes including planning a selected procedure, performing a selected procedure, or other appropriate processes. The start block <NUM>, therefore, may include various actions that may include preparing the imaging system <NUM>, preparing the subject <NUM>, or other appropriate steps to acquire or access image data.

After starting in block <NUM>, image data may be accessed or acquired at imaging system position i. As discussed above, the gantry <NUM> may be positioned at an initial or selected position 134i. The image data accessed or acquired in block <NUM> may be image data that is acquired in real time of the subject <NUM>, pre-acquired image data that is accessed, or any appropriate image data at a first or initial position. Image data may also be accessed or acquired at imaging system position n. As also discussed above, the imaging system <NUM> may be moved to a second or additional position including the gantry position 134n. Again the image data accessed or acquired in block <NUM> may be image data that is acquired in real time, image data that is accessed that is pre-acquired, or any appropriate image data. In various embodiments, image data acquired at the initial position may include the projection <NUM> and image data acquired or accessed at the second position <NUM> may be the projection <NUM>.

In both of the image data, a similar or identical feature, such as the same rod <NUM> and/or vertebrae <NUM><NUM> may be identified in block <NUM>. As discussed above, for example, the rod <NUM> and/or a portion of the rod <NUM> may be identified in both of the projections <NUM>, <NUM>. The identification of the feature may be manual, automatic, or a combination of manual and automatic techniques. In various embodiments, the feature may be identified by use of edge detection or edge identification programs, such as segmentation, that are executed by a processor, such as the processor <NUM>. Further, contrast gradients may be identified in the respective images that may be identified as the same or similar feature. Nevertheless the same or similar feature may be identified in both of the image data acquired or accessed in the respective blocks <NUM>, <NUM>. It is understood, therefore, that the identification may include various processes or steps that are carried out automatically, such by execution of program instructions with a processor, such as the processor <NUM>.

After identifying the same or similar feature in block <NUM>, a determination of a transformation to align the identified similar or same feature is made in block <NUM>. The determination of a transformation may include the required movement (e.g., translation) of image elements, such as pixels or voxels, to align the identified feature in one image projection to a second image projection. As discussed above, the rod <NUM> may be identified in both image projections and a transformation may be determined to align the rod <NUM> between both of the image projections <NUM>, <NUM>. Accordingly, a transformation may be determined in block <NUM> to perform the alignment of the identified feature.

Once the transformation is determined in block <NUM>, the transformation may be applied or used to determine an image transformation that is applied to the entire image data i and/or the image data n in block <NUM>. As discussed above, the imaging system, including the gantry <NUM>, may move between the acquisition of a first and second image data projection. The transformation may be applied to one or both of the image data to align both of image data <NUM>, <NUM> to each other. In various embodiments, for example, the initial position may be determined to be the first position for the registration or alignment and the other image or images are aligned thereto. The transformation may be applied to the image data at position n to align the image data projection to the initial projection. Therefore, for example, the projection <NUM> may have the transformation applied thereto to align the second projection <NUM> to the first projection <NUM>.

Once the projections are aligned in block <NUM>, they may be combined or merged, as discussed above. In various embodiments, the combination may include determining one or more weights in block <NUM>. The determination of weights in block <NUM> is optional and many include a weighting or gradient along a z-axis of one image data projection or the other during the combination, as discussed above and illustrated in <FIG>.

The image data may be combined in block <NUM> using the optional weights, if determined. The combination may include various combination procedures such as blending the image data acquired in block <NUM> and the image data acquired in block <NUM>. Various combination techniques can include a blending such as those known as weighted averaging, gamma blending, and/or feathering.

After the image data is combined in block <NUM>, the combined image data may be output in block <NUM>. The output of the combined image data can include storing or saving the image data for later viewing, planning, or other appropriate actions. Outputting the combined image data may also or alternatively include displaying the image data for viewing by the user <NUM> or other appropriate techniques. In various embodiments, for example, the combined image data may be used to be viewed and/or for navigation of selected instruments. As discussed above, the image data may be registered to the subject <NUM> and, therefore, the navigation system <NUM> may use the combined image data output in block <NUM> to assist in navigation, such as displaying a position graphical representation of the instrument <NUM>.

After combining the image data in block <NUM>, a determination of whether additional image data is to be acquired in block <NUM> may be made. If no additional image data is to be acquired a NO path <NUM> may be followed to an end block <NUM>. Accordingly, the procedure <NUM> may combine at least two image data projections, as discussed above, into a combined image data that may be output in block <NUM>.

If additional image data is determined to be acquired in block <NUM>, a YES path <NUM> may be followed to access or acquire additional image data in block <NUM>. Accordingly, any additional image data may be accessed and/or acquired and registered or aligned to a selected reference, such as the initial or image data and IS position i in block <NUM>. The process <NUM> may align a plurality or any appropriate number of projections that may be selected. As discussed above, for example, the single projection may include a dimension <NUM>. A combination of a selected number of image projections may be used to generate an image or image data having the dimension <NUM> as illustrated in <FIG>. Therefore the process <NUM> may also be used to generate the combined image data <NUM> that may be combined in block <NUM> and output in block <NUM>.

As discussed above the process <NUM> may be used to generate the combined image <NUM>. In addition and/or alternatively, the process <NUM> may be used to generate the combined image <NUM>. In addition, as discussed above, the procedures may be combined and/or augmented with each other. For example, the tracked location of the gantry <NUM> may be used to assist in determining a transformation of two image data projections. Also, identification of a similar feature in process <NUM> may also be used to assist in the combining images, such as confirming the tracked position and/or augmenting the transformation between the first and second image projections. Therefore, the combination image data <NUM> may include or be generated with one or more selected procedures.

Regardless, the combination image data <NUM> may include the dimension <NUM> that is greater than the dimension <NUM>, <NUM> of any single projection, as discussed above. Therefore, the combined image <NUM> may include a larger dimension for various procedures, such as of the subject <NUM> including the vertebrae <NUM>. The user <NUM> may view an image of a plurality of vertebrae in a single image greater than a single projection that may be generated with the imaging system <NUM>. Further, as discussed above, as the image data is registered to the subject <NUM>, the combination image <NUM> is also registered to the subject <NUM> and the navigation system <NUM> may, therefore, allow for navigation and tracking of tracked instruments, such as the instrument <NUM>, relative to the combined projection <NUM>. This allows the image <NUM> on the display <NUM> may be the combined image <NUM> with the icon or graphic representation <NUM> illustrated at the tracked or navigated position of the instrument <NUM> relative thereto. Also, the combined image <NUM> may be a two-dimensional and/or a three-dimensional image or reconstruction.

Instructions may be executed by a processor and may include may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects.

The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may include a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services and applications, etc..

The computer programs may include: (i) assembly code; (ii) object code generated from source code by a compiler; (iii) source code for execution by an interpreter; (iv) source code for compilation and execution by a just-in-time compiler, (v) descriptive text for parsing, such as HTML (hypertext markup language) or XML (extensible markup language), etc. As examples only, source code may be written in C, C++, C#, Objective-C, Haskell, Go, SQL, Lisp, Java®, ASP, Perl, Javascript®, HTML5, Ada, ASP (active server pages), Perl, Scala, Erlang, Ruby, Flash®, Visual Basic®, Lua, or Python®.

Communications may include wireless communications described in the present disclosure can be conducted in full or partial compliance with IEEE standard <NUM>-<NUM>, IEEE standard <NUM>-<NUM>, and/or IEEE standard <NUM>-<NUM>. In various implementations, IEEE <NUM>-<NUM> may be supplemented by draft IEEE standard <NUM>. 11ac, draft IEEE standard <NUM>. 11ad, and/or draft IEEE standard <NUM>.

Claim 1:
A method of generating a combined image from a plurality of image data (<NUM>, <NUM>), comprising:
accessing a first image data (<NUM>) acquired (<NUM>) at a first imager position (134i) of an imager (<NUM>); wherein said imager (<NUM>) comprises a C-arm fluoroscopic imaging system or an O-arm imaging system;
accessing a final image data (<NUM>) acquired (<NUM>) at a final imager position (134n) of the imager (<NUM>);
determining at least a portion of a feature included in both the first image data (<NUM>) and the final image data (<NUM>);
determining an alignment transformation to align the feature between the first image data (<NUM>) and the final image data (<NUM>);
determining a transformation matrix based on the alignment transformation to align the first image data (<NUM>) and the final image data (<NUM>) based on the determined transformation matrix, wherein the transformation matrix is operable to correct for misalignment of the first image data (<NUM>) and the final image data (<NUM>) in at least one degree of freedom of movement of the imager (<NUM>) between the first imager position (134i) and the final imager position (134n) that is outside a Z-axis movement of the imager (<NUM>);
outputting the transformation matrix;
characterised in that the method further comprises:
receiving an input of a selected image dimension;
determining if at least one intermediate imager position is required in addition to the first imager position (134i) and the final imager position (134n) to achieve the selected image dimension; and
if determined that at least one intermediate imager position is required, determining at least one intermediate imager position.