Patent Publication Number: US-2009221908-A1

Title: System and Method for Alignment of Instrumentation in Image-Guided Intervention

Description:
FIELD OF THE INVENTION 
     This invention relates to systems, methods, and instrumentation for facilitating accurate image-guided interventions using an ultrasound simulation device. 
     BACKGROUND OF THE INVENTION 
     When performing image-guided interventions (IGI), it is often required to guide a needle or instrument to a location in the body. In many forms of IGI, preoperative or intraoperative scans are performed. In some instances preoperative scans include computerized tomography (CT), magnetic resonance (MR), positron emission tomography (PET), or single proton emission tomography (SPECT). These modalities tend to utilize volumetric data acquisition, providing full 3D data sets comprising multiple “slices” of data representing contiguous or overlapping cross sections through the data. 
     During an intervention, a physician may use a position sensing system (referred to herein as a “tracking device”) together with position indicating elements attached to individual instruments. The tracking device may be an optical camera array or an electromagnetic (EM) tracking device, a fiber optic device, a GPS sensor device, an instrumented mechanical arm or linkage, or other type of tracking device. In the case of optical camera tracking devices, the position indicating elements may be Light Emitting Diodes (LEDs) and in the case of EM tracking devices the position indicating elements may be sensor coils that receive or transmit an EM signal to or from the tracking device. 
     During image-guided interventions, physicians typically watch a screen onto which a representation of the location and trajectory of an instrument is displayed. Often the display can take the form of a 3D display in which the instrument is indicated in the screen as a graphic representation overlayed on a volume rendering, surface rendering, or other rendering of the patient anatomy. Another representation is an “axial-coronal-sagittal” reformat, where a crosshair shows the location of the tip of the instrument on an axial view of the data as well as coronal and sagittal views that have been fabricated from the slice stack. Another common display includes an “oblique reformat” view, in which the dataset from the preoperative scan is reformatted along a plane representing the instrument path. The instrument is shown within a cut representing the current and future trajectory of the device. Another representation is a so called targeting view or “flight path” view, in which a preplanned target is shown and graphic elements such as circles or other graphic elements representing the location and orientation of the instrument are aligned so that the device is presented in the correct view. Such views are similar to views available in airplane cockpits to assist in navigation. Many other representations are also possible. 
     In all of these cases, difficulties may be presented. The oblique reformat requires the physician to view multiple image displays at one time in order to properly line up the device. This can be mentally challenging and require great concentration. This format may also require a learning phase during the alignment of the needle due to disparate coordinate systems preventing the graphic representation of the device from moving “sensibly.” The flight path can sometimes be more intuitive, but requires a planning stage in which the physician preplans at least the target. Unless he also preplans the path, he may be unaware of the material which will be transversed during the insertion of the device, potentially leading to complications if a critical anatomical structure is breached along the path. 
     By contrast, many physicians are familiar with ultrasound devices and find the interface intuitive and instructive, since the transducer can be held and moved in a way so as to follow the instrument, to view anatomy and examine an instrument&#39;s path. By manipulating the transducer, views can be changed at will, unlike the aforementioned views that require manipulation of the computer&#39;s user interface. Unfortunately, this type of view is not available though existing image guided surgery systems. 
     For these reasons and others, current techniques may pose many difficulties. 
     SUMMARY OF THE INVENTION 
     The invention addresses these and other difficulties in the art by providing a system, device, and methods for alignment and navigation of instrumentation during image-guided interventions. In some embodiments, a volumetric medical scan (image data) of a portion of the anatomy of a patient is loaded onto a computer that is connected to a tracking device capable of tracking the position and orientation of multiple position indicating elements in the tracking device&#39;s coordinate system. Patient space data regarding the anatomy of the patient may be obtained for example, using a registration device having one or more position indicating elements tracked by the tracking device. The patient space data is then registered to the volumetric image data. 
     A handheld ultrasound simulator fitted with one or more position indicating elements whose position and orientation (i.e., location within the coordinate system of the tracking device) are tracked by the tracking device is introduced to the surface or other portion of the anatomy of the patient. The position and orientation information of the ultrasound simulator is used to determine a simulated or imaginary ultrasound scan plane for the ultrasound simulator. This scan plane is used to reformat the image data so that the image data can be displayed to a user in a manner analogous to a handheld ultrasound transducer by re-slicing the image data according to the location and orientation of the ultrasound simulator. The location of an instrument fitted with one or more position sensors tracked by the tracking device may be projected onto the re-sliced scan data and the intersection of the trajectory of the tracked instrument and the imaginary scan plane may be calculated and displayed. 
     The various objects, features, and advantages of the invention will be apparent through the detailed description and the drawings attached hereto. It is also to be understood that the following detailed description is exemplary and not restrictive of the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of system for alignment of instrumentation during an image-guided intervention according to various embodiments of the invention. 
         FIG. 2  illustrates an ultrasound simulator according to various embodiments of the invention. 
         FIGS. 3A and 3B  illustrate an ultrasound simulator, its associated scan plane and a tracked instrument according to various embodiments of the invention. 
         FIG. 4  illustrates a process for alignment of instrumentation during an image-guided intervention according to various embodiments of the invention. 
         FIG. 5  illustrates an ultrasound simulator, a body, and a tracked instrument according to various embodiments of the invention. 
         FIG. 6A  illustrates a reformatted image according to various embodiments of the invention. 
         FIG. 6B  illustrates a coordinate system including an actual path of a tracked instrument through a scan plane of an ultrasound simulator according to various embodiments of the invention. 
         FIG. 7  illustrates a process for alignment of instrumentation on a training apparatus according to various embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a system  100 , which is an example of a system for alignment and navigation of instrumentation during an image-guided intervention. System  100  may include a computer element  101 , a registration device  121 , an ultrasound simulator  123 , a tracking device  125 , an imaging device  127 , a tracked instrument  129 , and/or other elements. 
     Computer element  101  may include a processor  103 , a memory device  105 , a power source  107 , a control application  109 , one or more software modules  111   a - 111   n,  one or more inputs/outputs  113   a - 113   n,  a display device  117 , a user input device  119 , and/or other elements. 
     Computer element  101  may be or include one or more servers, personal computers, laptop computers, or other computer devices. In some embodiments, computer element  101  may receive, send, store, and/or manipulate data necessary to perform any of the processes, calculations, image formatting, image display, or operations described herein. In some embodiments, computer element  101  may also perform any processes, calculations, or operations necessary for the function of the devices, elements, instruments, or apparatus described herein. 
     In some embodiments, computer element  101  may host a control application  109 . Control application  109  may comprise a computer application which may enable one or more software modules  111   a - 111   n.  One or more software modules  111   a - 111   n  enable processor  103  to receive (e.g., via a data reception module), send, and/or manipulate image data in the coordinate system of an imaging modality (including volumetric image data) regarding the anatomy of a patient, one or more objects (e.g., a phantom object or representative anatomical model) and/or other image data. This image data may be stored in memory device  105  or other data storage location. In some embodiments, one or more software modules  111   a - 111   n  may also enable processor  103  to receive (e.g., via the data reception module), send, and/or manipulate data regarding the location, position, orientation, and/or coordinates of one or more position indicating elements (e.g., sensor coils or other position indicating elements). This data may be stored in memory device  105  or other data storage location. 
     In some embodiments, one or more software modules  111   a - 111   n  such as, for example, a registration module may also enable processor  103  to calculate one or more registration transformations, perform registration (or mapping) of coordinates from two or more coordinate systems according to the one or more transformation calculations. 
     In some embodiments, one or more software modules  111   a - 111   n  such as, for example, a display module, may enable processor  103  to produce, format, and/or reformat one or more images from image data, position/orientation/location data, and/or other data. In some embodiments, images produced from image data, position/orientation/location data, other data, or any combination thereof may be displayed on display device  117 . In some embodiments, one or more software modules  111   a - 111   n  such as, for example, the display module, may enable the generation and display of images of the anatomy of the patient or an object (e.g., a phantom object or representative anatomical model) with the position and/or orientation of a tracked instrument superimposed thereon in real time (such that motion of the tracked instrument within the anatomy of the patient is indicated on the superimposed images) for use in an image-guided procedure. In some embodiments, the images on which the tracked instrument are displayed may be formatted to specifically display any anatomy or portion of a device intersected by an imaginary scan plane of an ultrasound simulator and/or any number of perspective views of or involving this imaginary scan plane. For example, if the imaginary scan plane is aligned so that it extends into the patient to from a cut extending from the anterior of the patient through to the posterior, the view displayed to a user may appear as an axial cut through the patient. Similarly, if the imaginary scan plane was aligned longitudinally along the patient&#39;s body, a sagittal cut may be displayed. Any oblique orientation of the imaginary scan plane may yield a view of an oblique cut through the patient. 
     In some embodiments, system  100  may include a registration device  121  connected to computer element  101  via an input/output  113 . Registration device  121  may provide position and or orientation data regarding one or more points or areas within or on an anatomical region of a patient. The registration device may otherwise enable registration of the anatomical region the patient, (including soft tissues and/or deformable bodies) and may include one or more position indicating elements (e.g., sensor coils) whose position and/or orientation are trackable by tracking device  125  in the coordinate system of tracking device  125 . 
     In some embodiments, system  100  may include an ultrasound simulator  123 .  FIG. 2  illustrates an example of ultrasound simulator  123 , which may be representative of a conventional ultrasound hand-piece. In some embodiments, ultrasound simulator  123  may include a handle portion  201 , a front portion  203 , one or more position indicating elements  205 , one or more LEDs  207 , a cable  209 , a connector  211 , and/or other elements. 
     The one or more position indicating elements  205  may enable the determination of a position (for example, position in Cartesian, spherical space, or other coordinate system) and orientation (for example, the roll, pitch, and yaw) of ultrasound simulator  123  in a coordinate system of tracking device  125 . As such, ultrasound simulator  123  may be connected to tracking device  125  and/or computer element  101  such that position and orientation information regarding the one or more position indicating elements  205  is communicated to computing element  101 . 
     In some embodiments, ultrasound simulator  123  may be tracked in 6 degrees of freedom using the one or more position indicating elements  205 . In another embodiment, it may be tracked in fewer degrees of freedom. While  FIG. 2  illustrates two position indicating elements  205 , in some embodiments, only one position indicating element may be used. For example, if a single position indicating element  205  were capable of providing information regarding 6 degrees of freedom and information regarding 6 degrees of freedom were desired, only a single position indicating element  205  may be used. However, if position indicating elements  205  capable of determining less than 6 degrees of freedom were used and information regarding 6 degrees of freedom were desired, two or more position indicating elements  205  may be used. In some embodiments, the one or more position indicating elements  205  may be embedded or integrated into ultrasound simulator  123  (hence they are illustrated using dashed lines in  FIG. 2 ). However, in some embodiments, they may be mounted on the surface of ultrasound simulator  123  or located elsewhere on or in ultrasound simulator  123  such that they are rigidly associated with ultrasound simulator  123 . 
     Cable  209  and connector  211  may connect the one or more position indicating elements  205 , LEDs  207 , and/or other elements of ultrasound simulator  129  to tracking device  125 , computer element  101 , and/or a power source. In some embodiments, data from position indicating elements  205  may be otherwise exchanged (e.g., wirelessly) with tracking device  125  or computer element  101 . 
     In some embodiments, ultrasound simulator  123  may be mechanically attached to additional elements such, for example, a mechanical digitizing linkage type of tracking device that enables measurement of the location and orientation of ultrasound simulator  123 . The mechanical digitizing linkage tracking device may be used in place of or in addition to tracking device  125  and one or more position indicating elements  205  to obtain position and orientation information regarding ultrasound simulator  123 . 
     In some embodiments, ultrasound simulator  123  may include additional emitter or sensor elements such as, for example, temperature sensors, pressure sensors, optical emitters and sensors, ultrasound emitters and sensors, microphones, electromagnetic emitters and receivers, microwave sensors or emitters, or other elements that perform therapeutic, diagnostic, or other functions. It may also include visual indication elements such as visible LEDs (e.g., LED  207 ), LCD displays, video displays or output or input devices such as buttons, switches or keyboards. 
     Ultrasound simulator  123  may be calibrated so that the location and orientation of front portion  203  (which contacts a patient) is known relative to the coordinate system of position indicating elements  205  and therefore tracking system  125 . In particular, ultrasound simulator  123  may be calibrated so that a plane representing the “scan plane” of the simulator that is analogous to an ultrasound transducer scan plane is known. Such an “imaginary” or “simulated” scan plane may be orientated extending out from front portion  203  of ultrasound simulator  123 . See for example, scan plane  301  as illustrated in  FIGS. 3A and 3B . 
     In some embodiments, system  100  may also include a tracking device  125 . In one embodiment, tracking device  125  may be operatively connected to computer element  101  via an input/output  113 . In some embodiments, tracking device  125  need not be operatively connected to computer element  101 , but data may be sent and received between tracking device  125  and computer element  101 . Tracking device  125  may include an electromagnetic tracking device, global positioning system (GPS) enabled tracking device, an ultrasonic tracking device, a fiber-optic tracking device, an optical tracking device, radar tracking device, or other type of tracking device. Tracking device  125  may be used to obtain data regarding the three-dimensional location, position, orientation, coordinates, and/or other information regarding one or more position indicating elements (including position indicating elements  205  of ultrasound simulator  123  and any position indicating elements located on registration device  121 , tracked instrument  129 , or other elements used with system  100 ). In some embodiments, tracking device  125  may provide this data/information to computer element  101 . 
     In some embodiments, system  100  may include an imaging device  127 . In one embodiment, data may be sent and received between imaging device  127  and computer element  101 . This data may be sent and received via an operative connection, a network connection, a wireless connection, through one or more floppy discs, CDs DVDs or through other data transfer methods. Imaging device  127  may be used to obtain image data (including volumetric or three dimensional image data) or other data necessary for enabling the apparatus and processes described herein. Imaging device  127  may provide this data to computer element  101 , where it may be stored. In some embodiments, a system for aligning instrumentation during an image-guided intervention need not include an imaging device  127 , rather ultrasound simulator  123  may be connected to a computer element  101  to which data regarding scans from an imaging device  127  previously is loaded. 
     Imaging device  127  may include one or more of a computerized tomography (CT) device, positron emission tomography (PET) device, magnetic resonance (MR) device, single photon emission computerized tomography (SPECT) device, 3D ultrasound device or other medical imaging device that provides scans (image data) representing a volume of image data (i.e., volumetric image data). In some embodiments the scans or image data may be stored in the memory  105  (such as, for example, RAM, flash memory, hard disk, CD, DVD, or other storage devices) of computer element  101 . The image data may be capable of being manipulated (e.g., by a display module) so as to enable the volume of data to be mathematically reformatted in such a way as to display a representation of the data as it would appear if it were cut, sliced, and/or viewed in any orientation. 
     System  100  may also include one or more tracked instruments  129 . A tracked instrument  129  may include therapy devices or diagnostic devices that include one or more positions indicating elements whose position and orientation can be tracked by tracking device  125  simultaneously to ultrasound simulator  123 . For example, in some embodiments, a tracked instrument  129  may include tracked needles, endoscopes, probes, scalpels, aspiration devices, or other devices. Other examples include the devices disclosed in US Patent Publication No. 20060173291 (U.S. patent application Ser. No. 11/333,364), 20070232882 (U.S. patent application Ser. No. 11/694,280), and U.S. Patent Publication No. 20070032723 (U.S. patent application Ser. No. 11/471,604), each of which are hereby incorporated by reference herein in their entirety. 
     In some embodiments, one or more tracked instruments  129 , registration devices  121 , ultrasound simulators  123 , and/or other elements or devices described herein may be interchangeably “plugged into” one or more inputs/outputs  113   a - 113   n.  In some embodiments, various software, hardware, and/or firmware may be included in system  100 , which may enable various imaging, referencing, registration, navigation, diagnostic, therapeutic, or other instruments to be used interchangeably with system  100 . In some embodiments, the software, firmware, and/or other computer code necessary to utilize various elements described herein such as, for example, display device  117 , user input  119 , registration device  121 , ultrasound simulator  123 , tracking device  125 , imaging device  127 , tracked instrument  129  and/or other device or element, may be provided by one or more of modules  111   a - 111   n.    
     Those having skill in the art will appreciate that the invention described herein may work with various system configurations. Accordingly, more or less of the aforementioned system components may be used and/or combined in various embodiments. It should also be understood that various software modules  111   a - 111   n  (including a data reception module, a registration module, and a display module) and control application  109  that are used to accomplish the functionalities described herein may be maintained on one or more of the components of system recited herein, as necessary, including those within individual medical tools or devices. In other embodiments, as would be appreciated, the functionalities described herein may be implemented in various combinations of hardware and/or firmware, in addition to, or instead of, software. 
       FIG. 4  illustrates a process  400 , which is an example of a process for aligning and/or guiding instrumentation during an image-guided intervention according to various embodiments of the invention. Process  400  includes an operation  401 , wherein one or more volumetric images (image data) of all or a portion of the anatomy of a patient are acquired by an imaging device (e.g., imaging device  127 ). As mentioned above, the image data may comprise or include a volume of data that can be mathematically reformatted in such a way as to display a representation of the data as it would appear if it were cut, sliced, and/or viewed in any orientation. The image data may then be communicated to and loaded onto computer element  101 . For purposes of registration of the anatomy of the patient (or a region thereof) or other purposes, the image data may be considered or referred to as “image space data.” 
     In some embodiments, prior to obtaining the image data, the patient may be outfitted with one or more registration aids in anticipation of a registration operation. In some embodiments, the registration aids may include active or passive fiducial markers as known in the art. In some embodiments, no such registration aids are required. 
     In an operation  403 , “patient space” data regarding the portion of the anatomy of the patient whereupon the image-guided intervention is to be performed may be obtained. For example, the patient space data may be obtained using a registration device having one or more position indicating elements (e.g., registration device  121 ) whose position and orientation are tracked by a tracking system (e.g., tracking system  125 ). The patient space data may be obtained in any number of ways depending on the surgical environment, surgical application, or other factors. For example, registration device  121  may be placed within the anatomy of the patient and information regarding the positions and/or orientation of the one or more position indicating elements of registration device  121  may be sampled by tracking device  125  and communicated to computer element  101 . Information regarding obtaining patient space data and other information regarding registration of image space data to patient space data can be found in U.S. Patent Publication No. 20050182319 (U.S. patent application Ser. No. 11/059,336), which is hereby incorporated herein by reference in its entirety. 
     In an operation  405 , the image space data may be registered to the patient space data. Registering the position of an anatomical object or region in a patient coordinate system (“patient space”) to views of the anatomical object in an image coordinate system (“image space”) may be performed using various methods such as, for example, point registration, path registration, surface registration, intrinsic registration or other techniques. Additional information relating to registration techniques can be found in U.S. Patent Publication No. 20050182319 (U.S. patent application Ser. No. 11/059,336) and U.S. Patent Publication No. 20060173269 (U.S. patent application Ser. No. 11/271,899), both of which are hereby incorporated by reference herein in their entirety. In some embodiments, the registration of operation  405  may be performed after scanning/imaging of operation  401  so that the patient&#39;s coordinate system is known in the coordinate system that the images were acquired in and vice versa. 
     Once registration has been performed, it may be possible to represent any tracked tool or instrument (e.g., tracked instrument  129 ) positioned in the coordinate system of the tracking device used to obtain the patient space data (e.g., tracking device  125 ) and thus the patient, in the coordinate system of the preoperative scan (e.g., overlayed or superimposed or otherwise integrated onto a graphical representation of the image data obtained in operation  401 ). As ultrasound simulator  123  is also tracked by the tracking device (due to being equipped with one or more position indicating elements  205 ), the location and orientation of ultrasound simulator  123  may also be determined relative to the coordinate system of the preoperative scan in an operation  407  and displayed as a graphical representation on the preoperative image data. Additionally, in operation  407 , the location of scan plane  301  of ultrasound simulator  123  may be determined relative to the coordinate system of the preoperative scan and displayed on the preoperative image data. 
     In an operation  409 , the position and orientation of ultrasound simulator  123  may be used to reformat the image data so that a view of the image data coincident to scan plane  301  of ultrasound transducer  123  can be displayed. The reformatting of the volumetric image data may include “re-slicing” the image data along the plane defined by scan plane  301  of ultrasound simulator  123 . This may involve determining the intersection plane of scan plane  301  with the image data and displaying the intersection of scan plane  301  with the volume images acquired in operation  401 . As ultrasound simulator  123  is moved over the patient, the view displayed to a user (e.g., via display  117 ) may be reformatted in real-time according to the position and orientation of ultrasound simulator  301  to provide a view, using the image data, of scan plane  301  of ultrasound simulator  123 . In some embodiments, an algorithm may be used to reformat the image data to simulate the data of an ultrasound, so to create an oblique reformat along the scan plane of the simulator that appears similar to an ultrasound view. 
     In an operation  411 , the location of additional instrumentation (e.g., tracked instrument  129 ) may be projected onto or otherwise integrated into the displayed image data (e.g., the reformatted view of the scan plane). In some embodiments, the location and orientation of tracked instrument  129  may be simultaneously displayed on the dataset that has been reformatted as determined by the location and orientation of ultrasound simulator  129 . Since the reformatted dataset may generally be oriented in a different plane than tracked instrument  129 , a “projection” of the instrument may be displayed on the slice relative to any anatomy or other elements intersecting the scan plane  301 . 
     In some embodiments, the location that tracked instrument  129  crosses scan plane  301  of ultrasound simulator  123  may be indicated on the slice.  FIGS. 3A and 3B  illustrate that the crossing of the additional instrumentation (tracked instrument  129 ) with the scan plane may be indicated as an intersection point  303  for a substantially linear device such as a needle or catheter. To indicate an approximate crossing point, a circle  305  may be used to represent the crossing point within an amount of error. In some embodiments, the crossing may be indicated as a line for a substantially planar tracked instrument such as, for example, a blade. To indicate an approximate crossing line, a rectangle may be used to represent the crossing within an amount of error. In some embodiments, for a volumetric tracked instrument such as, for example, a deployable radiofrequency ablation device, the crossing may be indicated as the shape formed by the intersection of the device with the scan plane of the simulator. An enlarged intersection region may be used to indicate some degree of error in the system. In general, the intersection of scan plane  301  of ultrasound simulator  123  and tracked instrument  129  will change as tracked instrument  129  and/or ultrasound simulator  123  (and thus scan plane  301 ) are moved. 
       FIG. 5  illustrates ultrasound simulator  123  in contact with body  501  (which may be or simulate an anatomy of a patient), having minor internal features  503  and major internal feature  505 . Scan plane  301  of ultrasound simulator  123  is also shown, as well as tracked instrument  129  and crosshairs  507  and  509 , which pinpoint the tip of tracked instrument  129 .  FIG. 6A  illustrates an image  600  that is an oblique reformatted view of scan plane  301  created using reformatted volumetric image data regarding body  501  and position and orientation data regarding ultrasound simulator  123 . The volumetric image data is reformatted according to the position and orientation information of ultrasound simulator  123  to enable image  600 , which is a view of a scan plane of ultrasound simulator  123  similarly positioned to the position shown in  FIG. 5 . However, unlike  FIG. 5 , wherein the tip of tracked instrument  129  is indicated as outside of body  501 , image  600  illustrates that tracked instrument  129  has been partly inserted into body as evidenced by the solid indicator  601 , which indicates the space occupied by tracked instrument  129  as projected onto the scan plane of the ultrasound simulator. A predicted path of tracked instrument  129  may also be provided, likewise projected onto the scan plane. Image  600  illustrates dots or marks  603 , indicating the predicted path of tracked instrument  129 . Circle  605  indicates the calculated area where tracked instrument  129  will cross the scan plane of ultrasound simulator  123  on its current trajectory. 
       FIG. 6B  illustrates a coordinate system  650 , wherein the scan plane  301  of ultrasound simulator  123  is represented by the X and Y axes. As illustrated, the plane of the trajectory of tracked instrument  129  is not in the same plane as scan plane  301 . However, indicator  601  is projected onto scan plane  301  (and thus image  600  of  FIG. 6A ) for the benefit of the user. Similarly, the predicted path of tracked instrument, indicated as line  607  may also be projected onto the image (e.g., as dots  603  [or dashes  603  in  FIG. 6B ]). As stated above, the predicted point where tracked instrument  129  will intersect scan plane  301  is indicated on the image by circle  605 . 
     As tracked instrument  129  is moved, indicator  601 , dots  603 , and circle  605  are adjusted accordingly on image  600 . If ultrasound simulator  123  is moved, then the scan will be reformatted or “sliced” differently to show an image relative to the new scan plane of ultrasound simulator  123 . Depending on the orientation of the ultrasound simulator, the view of  FIG. 6  will be different. If the trajectory of the instrument  129  is substantially in the same plane as the scan plane of the ultrasound simulator, the instrument will no longer cross the scan plane, since it is already in it. Also, what was previously a “projection” of the instrument path in the scan plane would in fact represent the actual predicted path of the instrument. The physician may move the ultrasound simulator handle to view many different cut planes through the anatomy and see the predicted location that the instrument&#39;s path will cross or does cross that plane. 
     In some embodiments, the invention includes a system and process for training users (e.g., physicians) to utilize ultrasound simulator  123  (and/or other system elements) for alignment of instrumentation during an image-guided intervention.  FIG. 7  illustrates a process  700 , which is an example of a process for training users to utilize ultrasound simulator  123  for alignment of instrumentation during an image-guided intervention. Process  700  may be performed using part or all of the system components of system  100 . Process  700  may also utilize a surrogate patient anatomy element or “phantom object” (also referred to as a “phantom”) upon which training is performed (rather than the anatomy of a patient) to simulate or substitute for the actual anatomy of the patient. In some embodiments, the phantom object may be constructed of an inert material such as, for example, rubber, gel, plastic, or other material. In some embodiments, the shape of the phantom object may be anthropomorphic. In some embodiments, the phantom object may be non-anthropomorphic. In some embodiments, the phantom object any include features that are representative of a real patient including simulated bones, simulated tumors, or other features. 
     Process  700  includes an operation  701 , wherein, similar to operation  401 , image data of an actual patient may be obtained. In an operation  703 , image data regarding the phantom object may also be obtained. In some embodiments, at least one of the image data sets (i.e., actual patient image data or phantom object image data) may be volumetric image data. In an operation  705 , the patient image data may be co-registered to the phantom object image data. In embodiments wherein only one type of image data is used (e.g., only actual patient image data or phantom object image data, thus there may be no co-registration operation  705 ), the image data used may be volumetric image data. In an operation  707 , patient space data regarding the phantom object may be obtained. This patient space data may be obtained using a tracked probe or other tracked device such as, for example, registration device  121  in a manner similar to that described herein regarding operation  403 . 
     In an operation  709 , the co-registered image data (patient and phantom object image data) may be registered to the patient space data from the phantom object. In instances where phantom object image data is not obtained, the image data from the patient may be registered to the patient space data from the phantom object. In other embodiments, training may be performed using only image space data regarding the phantom object that is registered to patient space data regarding the phantom object. Registration may be carried out by any of the aforementioned methods or other methods of registration. 
     In an operation  711 , an ultrasound simulator that is tracked by the tracking device used to obtain the phantom object patient space data (e.g., ultrasound simulator  123 ) may be introduced to the surface or other portion of the phantom object and the position and orientation of the ultrasound simulator may be determined. Additionally, the intersection of the scan plane of the ultrasound simulator and the image data may be determined. 
     In an operation  713 , the image data (e.g., co-registered patient and phantom object data, patient image data only, or phantom object image data only), may then be reformatted to display a view of the “scan plane” of the ultrasound simulator (e.g., at an oblique view). In an operation  715 , an instrument tracked by the tracking device used to obtain the patient space data of the phantom object and track the ultrasound simulator (e.g., tracked instrument  129 ), may be introduced to the phantom object and displayed on the reformatted view of the image data. As the tracked instrument moves, its display on the reformatted image data may be moved. As the ultrasound simulator is moved, the image data is reformatted or “re-sliced” (including a new determination of where the new scan plane intersects the image data) to show a view of the new scan plane of the ultrasound simulator and thus the tracked instrument relative to the portions of the phantom object intersected by the scan plane. 
     In this manner, a user may be trained to navigate any number of tracked instruments while manipulating the ultrasound simulator around the phantom object. Depending on the design of the phantom object, the user may train for countless specific circumstances (e.g., for specific types of anatomy specific targets, or other scenarios, as reflected by the features of the phantom object). 
     For example, in some embodiments, the phantom object may include a “pre-selection apparatus.” The pre-selection apparatus may include one or more elements that enable an operator to pre-select a three dimensional location (“target point”) in the phantom object that may act as a target for training purposes. For example, the pre-selection apparatus may be used to designate a “proxy tumor” in a phantom object for the purposes of training a user. The systems and methods of the invention may be then be used by a trainee to help locate the proxy tumor. For example, a needle or crossing light beams may be used to demarcate the proxy tumor. In one example, a real patient&#39;s image data may be co-registered with an inert gel phantom object that enables the trainee to insert tracked therapy devices such as needles into it. In some embodiments, the phantom object may include actual (physical) proxy tumors such as blobs of different colored or different density of gel. In some embodiments, a tracked needle or therapy device is directed using the systems and methods of the invention to the location of the proxy tumor within the phantom object. To score the trainee, the proximity of the tracked device may be compared to the position of the proxy tumor. 
     In some embodiments, the pre-selection apparatus may be a mechanical device such as a stereotactic framework for positioning a needle or device to a particular location. The framework may enable the location of the needle or device to be adjusted by dials, knobs, motors, or other elements included in the framework. As discussed above, in some embodiments, the tip of the needle or device may act as a lesion or other feature for training in order to co-locate a tracked instrument to the same location using the systems and method of the invention. 
     In some embodiments, the pre-selection apparatus may include elements for optically designating an interior target point in a transparent or translucent phantom object, for example, by using two or more lasers to intersect on a location. In some embodiments, the lasers may be positioned using framework and/or a motor system. 
     While the methods processes described herein have been described as method and processes for aligning and navigating instrumentation during image guided surgery, the invention may also provide systems and methods (or processes) for visualizing or displaying a portion of the anatomy of a patient using an ultrasound simulator (e.g., ultrasound simulator  123 ) and/or other system elements described herein. 
     In some embodiments, the invention includes a computer readable medium having computer readable instructions thereon for performing the various features and functions described herein, including one or more of the operations described in process  400  and  700 , and/or other operations, features, or functions described herein. 
     It should be understood by those having skill in the art that while the operations of the methods and processes described herein have been presented in a certain order, that the invention may be practiced by performing the operations, features, and/or functions described herein in various orders. Furthermore, in some embodiments, more or less of the operations, features, and/or functions described herein may be used. 
     Other embodiments, uses and advantages of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The specification should be considered exemplary only, and the scope of the invention is accordingly intended to be limited only by the following claims.