Patent Publication Number: US-2018054880-A1

Title: Gated Image Acquisition And Patient Model Construction

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/908,189 filed on Oct. 20, 2010. The entire disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to imaging a subject, and particularly to determining and performing an optimal image data acquisition of the subject to model various physiological characteristic and anatomical features of the subject. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     A subject, such as a human patient, may select or be required to undergo a surgical procedure to correct or augment an anatomy of the patient. The augmentation of the anatomy can include various procedures, such as movement or augmentation of bone, insertion of implantable devices, or other appropriate procedures. A surgeon can perform the procedure on the subject with images of the patient that can be acquired using imaging systems such as a magnetic resonance imaging (MRI) system, computed tomography (CT) system, fluoroscopy (e.g. C-Arm imaging systems), or other appropriate imaging systems. 
     Images of a patient can assist a surgeon in performing a procedure including planning the procedure and performing the procedure. A surgeon may select a two dimensional image or a three dimensional image representation of the patient. The images can assist the surgeon in performing a procedure with a less invasive technique by allowing the surgeon to view the anatomy of the patient without removing the overlying tissue (including dermal and muscular tissue) when performing a procedure. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     According to various embodiments, a system to acquire image data of a patient with an imaging system using enhanced contrast imaging can include an imaging system having a first energy source with a first energy parameters and a second energy source with a second energy parameters. The imaging system can also include a pump operable to inject a contrast agent into the patient with an instruction. A controller can be in communication with both the imaging system and the pump. The imaging system can communicate with the pump through the controller regarding timing of the injection of a contrast agent into the patient and is further operable to acquire image data based upon the timing of the injection of the contrast agent and/or the clinical procedure. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is an environmental view of an imaging system in an operating theatre; 
         FIG. 2  is a detail view of an imaging system with a dual energy source system; 
         FIG. 3A  is a schematic representation of non-contrast enhanced image data; and 
         FIG. 3B  is a schematic representation of a contrast enhanced image data. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     With reference to  FIG. 1 , in an operating theatre or operating room  10 , a user, such as a surgeon  12 , can perform a procedure on a patient  14 . In performing the procedure, the user  12  can use an imaging system  16  to acquire image data of the patient  14  for performing a procedure. A model can be generated using the image data and displayed as image data  18  on a display device  20 . The display device  20  can be part of a processor system  22  that includes an input device  24 , such as a keyboard, and a processor  26  which can include one or more processors or microprocessors incorporated with the processing system  22 . A connection  28  can be provided between the processor  26  and the display device  20  for data communication to allow driving the display device  20  to illustrate the image data  18 . 
     The imaging system  16  can include an O-Arm® imaging system sold by Medtronic Navigation, Inc. having a place of business in Louisville, Co., USA. The imaging system  16 , including the O-Arm® imaging system, or other appropriate imaging systems in use during a selected procedure are also described in U.S. patent application Ser. No. 12/465,206 filed on May 13, 2009, incorporated herein by reference. 
     The O-Arm® imaging system  16  includes a mobile cart  30  that includes a control panel or system  32  and an imaging gantry  34  in which is positioned a source unit  36  and a detector  38 . The mobile cart  30  can be moved from one operating theater to another and the gantry  34  can move relative to the cart  30 , as discussed further herein. This allows the imaging system  16  to be mobile thus allowing it to be used in multiple locations and with multiple procedures without requiring a capital expenditure or space dedicated to a fixed imaging system. 
     The source unit  36  can emit x-rays through the patient  14  to be detected by the detector  38 . As is understood by one skilled in the art, the x-rays emitted by the source  36  can be emitted in a cone and detected by the detector  38 . The source/detector unit  36 / 38  is generally diametrically opposed within the gantry  34 . The detector  38  can move in a 360° motion around the patient  14  within the gantry  34  with the source  36  remaining generally 180° opposed to the detector  38 . Also, the gantry  34  can move isometrically relative to the subject  14 , which can be placed on a patient support or table  15 , generally in the direction of arrow  40  as illustrated herein. The gantry  34  can also tilt relative to the patient  14  illustrated by arrows  42 , move longitudinally along the line  44  relative to a longitudinal axis  14 L of the patient  14  and the cart  30 , can move up and down generally along the line  46  relative to the cart  30  and transversely to the patient  14 , to allow for positioning of the source/detector  36 / 38  relative to the patient  14 . The O-Arm® imaging device  16  can be precisely controlled to move the source/detector  36 / 38  relative to the patient  14  to generate precise image data of the patient  14 . The imaging device  16  can be connected with the processor  26  via connection  50  which can include a wired or wireless connection or physical media transfer from the imaging system  16  to the processor  26 . Thus, image data collected with the imaging system  16  can be transferred to the processing system  22  for navigation, display, reconstruction, etc. 
     Briefly, according to various embodiments, the imaging system  16  can be used with an unnavigated or navigated procedure. In a navigated procedure, a localizer, including either or both of an optical localizer  60  and an electromagnetic localizer  62  can be used to generate a field or receive or send a signal within a navigation domain relative to the patient  14 . The navigated space or navigational domain relative to the patient  14  can be registered to the image data  18  to allow registration of a navigation space defined within the navigational domain and an image space defined by the image data  18 . A patient tracker or dynamic reference frame  64  can be connected to the patient  14  to allow for a dynamic registration and maintenance of registration of the patient  14  to the image data  18 . 
     A patient tracking device or dynamic registration device  64  and an instrument  66  can then be tracked relative to the patient  14  to allow for a navigated procedure. The instrument  66  can include an optical tracking device  68  and/or an electromagnetic tracking device  70  to allow for tracking of the instrument  66  with either or both of the optical localizer  60  or the electromagnetic localizer  62 . The instrument  66  can include a communication line  72  with a navigation interface device  74  as can the electromagnetic localizer  62  with communication line  76  and/or the optical localizer  60  with communication line  78 . Using the communication lines  74 ,  78  respectively, the probe interface  74  can then communicate with the processor  26  with a communication line  80 . It will be understood that any of the communication lines  28 ,  50 ,  76 ,  78 , or  80  can be wired, wireless, physical media transmission or movement, or any other appropriate communication. Nevertheless, the appropriate communication systems can be provided with the respective localizers to allow for tracking of the instrument  66  relative to the patient  14  to allow for illustration of the tracked location of the instrument  66  relative to the image data  18  for performing a procedure. 
     It will be understood that the instrument  66  being any appropriate instrument, such as a ventricular or vascular stent, spinal implant, neurological stent or stimulator, ablation device, or the like. The instrument  66  can be an interventional instrument or can include or be an implantable device. Tracking the instrument  66  allows for viewing the instrument&#39;s  66  location relative to the patient  14  with use of the registered image data  18  without direct viewing of the instrument  66  within the patient  14 . 
     Further, the gantry  34  can include an optical tracking device  82  or an electromagnetic tracking device  84  to be tracked with a respective optical localizer  60  or electromagnetic localizer  62 . Accordingly, the imaging device  16  can be tracked relative to the patient  14  as can the instrument  66  to allow for initial registration, automatic registration or continued registration of the patient  14  relative to the image data  18 . Registration and navigated procedures are discussed in the above incorporated U.S. patent application Ser. No. 12/465,206. 
     With reference to  FIG. 2 , according to various embodiments, the source  36  can include a single x-ray tube  100  that can be connected to a switch  102  that can interconnect a power source A  104  and a power source B  106  with the x-ray tube  100 . X-rays can be emitted generally in a cone shape  108  towards the detector  38  and generally in the direction of the vector  110 . The switch  102  can switch between the power source A  104  and the power source B  106  to power the x-ray tube  100  at different voltages and amperages to emit x-rays at different energies generally in the direction of the vector  110  towards the detector  38 . It will be understood, however, that the switch  102  can also be connected to a single power source that is able to provide power at different voltages and amperages rather than the  102  switch that connects to two different power sources A  104 , and B  106 . Also, the switch  102  can be a switch that operates to switch a single power source between different voltages and amperages. The patient  14  can be positioned within the x-ray cone  108  to allow for acquiring image data of the patient  14  based upon the emission of x-rays in the direction of vector  110  towards the detector  38 . 
     The two power sources A and B  104 ,  106  can be provided within the source housing  36  or can be separate from the source  36  and simply be connected with the switch  102  via appropriate electric connections such as a first cable or wire  112  and a second cable or wire  114 . The switch  102  can switch between the power source A  104  and the power source B  106  at an appropriate rate to allow for emission of x-rays at two different energies through the patient  14  for various imaging procedures, as discussed further herein. The differing energies can be used for material separation and/or material enhanced reconstruction or imaging of the patient  14 . 
     The switching rate of the switch  102  can include about 1 millisecond to about 1 second, further including about 10 ms to 500 ms, and further including about 50 ms. Further, the power source A  104  and the power source B  106  can include different power characteristics, including different voltages and different amperages, based upon selected contrast enhancement requirements. For example, as discussed further herein, it can be selected to allow for contrast enhancement between soft tissue (e.g. muscle or vasculature) and hard tissue (e.g. bone) in the patient  14  or between a contrast agent injected in the patient  14  and an area without a contrast agent injected in the patient  14 . 
     As an example, the power source A  104  can have a voltage of about 75 kV and can have an amperage of about 50 mA, which can differ from the power source B which can have a voltage of 125 kV and 20 mA. The selected voltages and amperages can then be switched with the switch  102  to power the x-ray tube  100  to emit the appropriate x-rays generally in the direction of the vector  110  through the patient  14  to the detector  38 . It will be understood that the range of voltages can be about 40 kV to about 80 kV and the amperages can be about 10 mA to about 500 mA. Generally, the power characteristics differences between the first power source A  104  and the second power source B  106  can be about 40 kV to about 60 k V and about 20 mA to about 150 mA. 
     The dual power sources allow for dual energy x-rays to be emitted by the x-ray tube  100 . As discussed above, the two or dual energy x-rays can allow for enhanced and/or dynamic contrast reconstruction of models of the subject  14  based upon the image data acquired of the patient  14 . Generally an iterative or algebraic process can be used to reconstruct the model of at least a portion of the patient  14  based upon the acquired image data. It will be understood, however, that any appropriate number of power sources or switching possibilities can be provided. Two is included in the subject disclosure merely for clarity of the current discussion. 
     The power sources can power the x-ray tube  100  to generate two dimension (2D) x-ray projections of the patient  14 , selected portion of the patient  14 , or any area, region or volume of interest. The 2D x-ray projections can be reconstructed, as discussed herein, to generate and/or display three-dimensional (3D) volumetric models of the patient  14 , selected portion of the patient  14 , or any area, region or volume of interest. As discussed herein, the 2D x-ray projections can be image data acquired with the imaging system  16 , while the 3D volumetric models can be generated or model image data. 
     Appropriate algebraic techniques include Expectation maximization (EM), Ordered Subsets EM (OS-EM), Simultaneous Algebraic Reconstruction Technique (SART) and Total Variation Minimization (TVM), as generally understood by those skilled in the art. The application to performing a 3D volumetric reconstruction based on the 2D projections allows for efficient and complete volumetric reconstruction. Generally, an algebraic technique can include an iterative process to perform a reconstruction of the patient  14  for display as the image data  18 . For example, a pure or theoretical image data projection, such as those based on or generated from an atlas or stylized model of a “theoretical” patient, can be iteratively changed until the theoretical projection images match the acquired 2D projection image data of the patient  14 . Then, the stylized model can be appropriately altered as the 3D volumetric reconstruction model of the acquired 2D projection image data of the selected patient  14  and can be used in a surgical intervention, such as navigation, diagnosis, or planning. The theoretical model can be associated with theoretical image data to construct the theoretical model. In this way, the model or the image data  18  can be built based upon image data acquired of the patient  14  with the imaging device  16 . 
     The 2D projection image data can be acquired by substantially annular or 360° orientation movement of the source/detector  36 / 38  around the patient  14  due to positioning of the source/detector  36 / 38  moving around the patient  14  in the optimal movement. Also, due to movements of the gantry  34 , the detector need never move in a pure circle, but rather can move in a spiral helix, or other rotary movement about or relative to the patient  14 . Also, the path can be substantially non-symmetrical and/or non-linear based on movements of the imaging system  16 , including the gantry  34  and the detector  38  together. In other words, the path need not be continuous in that the detector  38  and the gantry  34  can stop, move back the direction from which it just came (e.g. oscillate), etc. in following the optimal path. Thus, the detector  38  need never travel a full 360° around the patient  14  as the gantry  34  may tilt or otherwise move and the detector  38  may stop and move back in the direction it has already passed. 
     In acquiring image data at the detector  38 , the dual energy x-rays generally interact with a tissue and/or a contrast agent in the patient  14  differently based upon the characteristics of the tissue or the contrast agent in the patient  14  and the energies of the two x-rays emitted by the x-ray tube  100 . For example, the soft tissue of the patient  14  can absorb or scatter x-rays having an energy produced by the power source A  104  differently than the x-rays having energy produced by the power source B  106 . Similarly, a contrast agent, such as iodine, can absorb or scatter the x-rays generated by the power source A  104  differently from those generated by the power source B  106 . Switching between the power source A  104  and the power source B  106  can allow for determination of different types of material properties (e.g. hard or soft anatomy), or contrast agent, implants, etc. within the patient  14 . By switching between the two power sources  104 ,  106  and knowing the time when the power source A  104  is used to generate the x-rays as opposed to the power source B  106  to generate the x-rays the information detected at the detector  38  can be used to identify or segregate the different types of anatomy or contrast agent being imaged. 
     A timer can be used to determine the time when the first power source A  104  is being used and when the second power source B  106  is being used. This can allow the images to be indexed and separated for generating different models of the patient  14 . Also, as discussed herein, the timer, which can be a separate system or included with the imaging system  16  or the processor system  26 , can be used to index image data generated with the contrast agent injected into the patient  14 . 
     With reference to  FIG. 3A , image data acquired when powering the x-ray tube  100  with the power source  104  is schematically illustrated. As illustrated in  FIG. 3A , the image data can include image data of soft tissue, such as surrounding tissues  150  that surround a vasculature  152 . As illustrated in  FIG. 3A , the power source A  104  can generate x-rays of the x-ray tube  100  that provide substantially little contrast between the vasculature  152  and the surrounding tissue  150 , even if a contrast agent is present in the vasculature agent  152 , such as iodine. With reference to  FIG. 3B , however, the second power source B  106  can be used to generate second energy x-rays to acquire image data that illustrates the surrounding tissue  150 ′ relative to the vasculature  152 ′. This can be further enhanced with a contrast agent that can be injected into the patient  14 . As is understood in the art, the two power levels have different attenuations based on the materials in the patient  14 . This differing attenuation can be used to differentiate materials, e.g. vasculature  152  and the surrounding tissue  150 , in the patient  14 . 
     With the acquisition of the image data illustrated in  FIG. 3A  and  FIG. 3B , a reconstruction can be made to clearly identify the vasculature  152  of the patient  14  separate from the surrounding tissue  150  of the patient  14 . The dual energy system can be used to reconstruct a model of the vasculature  152  of the patient  14  to discriminate the vasculature  152  from the surrounding tissue  150  of the patient  14 . In identifying the vasculature  152 , the imaging system  16 , including the O-Arm® imaging system, can be used to efficiently image the vasculature  152  of the patient  14  in the operating theatre  10  during a procedure, such as a valve replacement procedure, a stent procedure, an inclusion ablation procedure, or an angioplasty procedure. 
     At least because the x-ray tube  100  is in a moveable imaging system, such as the imaging system  16 , it can be moved relative to the patient  14 . Thus, the x-ray tube  100  may move relative to the patient  14  while the energy for the x-ray tube  100  is being switched between the first power source  104  and the second power source  106 . Accordingly, an image acquired with the first power source  104  may not be at the same pose or position relative to the patient  14  as the second power source  106 . If a model is desired or selected to be formed of a single location in the patient  14 , however, various interpolation techniques can be used to generate the model based on the amount of movement of the x-ray tube  100  between when the projection with the first power source  104  and the projection with the second power source  106  was acquired. 
     The dual energy of the x-rays emitted by the x-ray tube  100  due to the two power sources  104 ,  106  can allow for substantially efficient and enhanced contrast discrimination determination between the vasculature  152  and the musculature  150  of the patient  14 . Moreover, the switching by a switch  102  between the power source A  104  and the power source B  106  allows for an efficient construction of the source  36  where the single x-ray tube  100  can allow for the generation of x-rays at two different energies to allow for enhanced or dynamic contrast modeling of the patient  14 , such as modeling the vasculature of the patient  14  including a contrast agent therein. 
     The patient  14  can also be imaged with the injected contrast agent by gating the acquisition of the image data of the patient  14  based upon the injection of the contrast agent. According to various embodiments, a contrast agent, such as iodine, can be injected into the patient  14  to provide additional contrast in the image data acquired of the patient  14  with the imaging system  16 . During the image acquisition, however, the contrast agent flows through the vasculature of the patient  14  from an artery phase to a venous phase. For example, the contrast agent can be injected into the patient  14  into an artery where the contrast agent can flow through the vasculature of the patient  14  to the heart, through the heart, to the lungs through the venous system, back through the heart, and out into the arterial portion of the vasculature of the patient  14 . 
     When acquiring image data of the patient  14  to identify or reconstruct the vasculature of the patient  14 , knowing the timing of when image data is acquired relative to the timing of the injection of the contrast agent can allow for a reconstruction of the various phases based on the known movement of the contrast agent through structures of the patient  14 . In other words, it is generally understood that the contrast agent will flow through the patient  14  as described above at a known or generally known rate. As illustrated in  FIG. 3B , the dual energy x-rays, generated with the x-ray tube  100  based upon the power source A  104  and the power source B  106 , can be used to generate image data of any portion of the vasculature of the patient  14 . 
     The acquisition of the image data, therefore, can be gated relative to the injection of the contrast agent into the patient  14 . For example, the controls  32  of the imaging system  16  can be associated or communicate with a control of a pump  170  (illustrated in  FIG. 1 ) through a communication line  172  (illustrated in  FIG. 1 ) that pumps or injects the contrast agent into the patient  14 . The communication  172  between the pump  170  and the imaging device control  32  can be any appropriate communication such as a wired, wireless, or other data communication system. Also, the control  170  for the pump can be incorporated into the controls  32  of the imaging system  16  or the processor system  26 . 
     According to various embodiments, the control system  32  for the imaging system  16  can control the pump  170  to initiate injection of the contrast agent into the patient  14 . The imaging system  16  can then acquire image data of the patient  14  over a set period of time to identify the difference between an arterial phase and a venous phase in the patient  14 . For example, the imaging system can control the pump  170  to inject the contrast agent and then acquire image data for approximately 10 seconds to approximately 20 second including approximately 13 seconds. The imaging system  16  can identify or separate a first portion of the image data, such as about 5 second to about 7 seconds, including about 6 seconds as an arterial phase and a second phase of the image data, such as image data acquired after about 6 second to about 8 seconds, including about 7 seconds as a venous phase. In other words, the control system  32 , or other appropriate processor system, can index the image data to determine when the image data was acquired. Also, it will be understood that the image data can be acquired at the two energies. Thus, the controls  32  or other appropriate processing system (e.g. a timer) can index the image data based on which of the two power sources  104 ,  106  were used to power the x-ray tube  100 . 
     After the acquisition of the image data and determining a segregation of time of image data acquisition, a reconstruction of the vasculature of the patient  14  can then be made to illustrate or identify or reconstruct an arterial phase of the patient  14  and separately a venous phase of the patient  14 . Accordingly, the imaging system  16  controlled with the controller  32  can be used to acquire image data of both a venous phase and an arterial phase of the patient  14  in a single image data acquisition sweep or period. In other words, the phase determination and reconstruction of an arterial phase and a venous phase of the vasculature of the patient  14  can be based on a single image data acquisition phase of the patient  14 . Again, this can minimize or limit the exposure of the patient  14  and operating room staff to x-rays emitted from the x-ray tube  100  by requiring only a single image data acquisition phase. It will be understood, however, that a plurality of image data acquisition phases can be acquired of the patient  14 . 
     The control system  32  of the imaging system  16  can be used to gate acquisition of the image data in addition to or with timing of the pump  170 . For example, it can be selected to acquire image data of the vasculature of the patient  14  during diastole of the heart. During diastole of the heart of the patient  14 , the heart generally does not move and blood in the vasculature is also relatively still. Accordingly, the image data can be acquired of the patient  14  by gating the acquisition of the image data relative to the heart movement of the patient  14 . The generation of the x-rays with the x-ray tube  100  can be switched with the switch  102  to allow for time emission of x-rays from the x-ray tube  100 . 
     The image data can be acquired by emitting x-rays from the x-ray tube  100  substantially sequentially such that at a selected period of time no x-rays are emitted by the x-ray tube  100  and at a different or second selected time x-rays are emitted from the x-ray tube  100 . The x-rays emitted from one period to another can be at either of the two energies allowed by the power source A  104  or the power source B  106 . Accordingly, at various times no x-rays can be emitted from the x-ray tube  100 , but at other times x-rays can be emitted from the x-ray tube at a selected energy. 
     In being able to control the image system to emit or not emit x-rays image data acquisition can be gated relative to a physiological event of the patient  14 . It will be further understood that gating of the image acquisition can be based upon respiration of the patient  14 , physical movement of the patient  14 , and other physiological events. The control system  32  can also be used to index the image data regarding whether acquired during a physiological event or not. The physiological event can be determined with an appropriate system, such as an electrocardiogram, or based on a regular rate of image acquisition (e.g. diastole occurs about 2 seconds in the patient  14 ). 
     Also, due to gating of the imaging system  16  relative to the patient  14 , the control system  32  can also be used to control the imaging system  16  to control the speed of the detector  38  relative to the patient  14 . As discussed above, the detector  38  of the imaging system can translate within the gantry  34  of the imaging system  16  to acquire image data of the patient  14 . Further as discussed above, image data can be selected to be acquired of the patient  14  during only selected physiological events, such as diastole of the heart. To generate or form a three-dimensional model of at least a portion of the patient  14 , it can be selected to have separation of a selected amount between acquisitions of images of the patient  14 . 
     The detector  38  can be moved at a selected speed and change speeds to ensure appropriate separation of the images during the selected physiological events. The detector  38  can move at a first speed during a first physiological event such as systole of the heart, and at a second speed, such as a greater speed, during diastole of the heart to ensure appropriate separation of acquisition of images of the patient  14  during the selected physiological event. 
     In generating the 3D volumetric reconstruction to form the model, as discussed above, the model may be multi-phase to illustrate a selected portion of the patient to illustrate a first phase of physiological action and anatomical location and a second phase of physiological action and anatomical location. Thus, the model, or more than one model, can be used to illustrate a first phase (e.g. an arterial phase) and a second phase (e.g. venous phase) of the patient  14 . Also, due to gating and movement of the detector  38  a first position of the detector  38  during image data acquisition and a second position of the detector  38  during image data acquisition can be used in the generating the first model and generating the second model to illustrate more than one phase of a physiological action of the patient  14 . Additionally, the anatomy of the patient  14  and the physiology of the patient  14  can be used to form the 3D reconstruction. For example, the configuration of a bone of the patient  14  or a phase of a heart beat of the patient  14  can be used as a priori knowledge to assist in model reconstruction. 
     Also, the controller  32  of the imaging system  16  can be used to “rewind” or move the detector  38  back over the same path just traversed by the detector  38 . Even while moving in a selected single path or direction, the detector  38  can be stopped and started, for example for gating or acquiring additional image data (e.g. x-ray projections) at a selected location. Accordingly, the controller  32  can control the imaging system  16  to achieve a selected separation of images relative to the patient  14  for reconstruction of an appropriate or selected model of the patient  14  based upon the required image data. 
     The reconstruction based on the image data or the raw image data can be used to perform a procedure on the patient  14 . As discussed above selected navigation or tracking systems can be associated with the imaging system  16 . Accordingly, the patient  14  can be registered to the image data and a navigation procedure can be performed. The navigated procedure can include placement of a stent in the patient&#39;s  14  heart, brain, or other vasculature, ablation procedures, angioplasty, implant placement or bone resection. Navigation can include tracking or determining automatically a location of an instrument positioned in a navigation field relative to a selected reference frame, such as in patient space, during a surgical procedure. The location of the instrument  66  can be illustrated on the display device  20  with an icon  174  that can be superimposed on the image data or the reconstructed model or image data  18 . 
     It will also be understood that the image data and/or model can be used to plan or confirm a result of a procedure without requiring or using navigation and tracking. The image data can be acquired to assist in a procedure, such as an implant placement. Also, the image data can be used to identify blockages in the vasculature of the patient  14 , such as with the contrast agent. Thus, navigation and tracking are not required to use the image data in a procedure. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.