WO2013057641A1

WO2013057641A1 - Cathlab planning tool

Info

Publication number: WO2013057641A1
Application number: PCT/IB2012/055540
Authority: WO
Inventors: Bharat RAMACHANDRAN; Ameet Kumar Jain; Robert Manzke; Vijay Parthasarathy; Raymond Chan
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2011-10-21
Filing date: 2012-10-12
Publication date: 2013-04-25

Abstract

A method, system, and program product are provided for planning a cathlab intervention with optimal tracking performance. The method comprises: determining electromagnetic tracking error as a function of pose for a plurality of possible poses of an x-ray machine, planning an intervention procedure using the x-ray machine, and iteratively determining an optimal pose for the x-ray machine based upon electromagnetic tracking using the determined electromagnetic tracking error for each of the plurality of possible poses.

Description

CATHLAB PLANNING TOOL

FIELD OF THE INVENTION

The invention relates to the field of medical imaging and more particularly to a method, system and computer program product for planning a cathlab intervention with optimal tracking performance.

BACKGROUND

The principle behind electro-magnetic (EM) tracking is that a field generator produces spatially varying magnetic fields which induce currents in the sensor coils. A measurement system is then used to calculate the position and orientation of the sensors, based on measured voltages in the sensors. EM tracking techniques provide realtime position and orientation information in 3D space, which may be used to aid interventional procedures. Since the size of these sensor coils is very small, they can be embedded into a catheter and be used for guided navigation. As a result, EM tracking systems are very well suited to in-body interventions.

The presence of ferromagnetic or paramagnetic conductors, such as in medical equipment, can distort the EM field. Also, electromagnetc interference from nearby electronics is known to reduce the accuracy of EM tracking. As a result, it is difficult for an interventionalist to determine the accuracy of a tracked position of a sensor, due to the distortion and interference caused by medical equipment used in the intervention.

Various approaches have been taken to provide intra-operative quality control for EM tracking. Most of these schemes aim to detect and compensate for errors during EM tracking that are caused by large metallic distorters. One such scheme for real-time estimation of error confidences is based on calibration wands. Another technique relies on calibration phantoms and known sensor geometry. Another technique relies on calibration between EM and other imaging modalities, such as x-ray or ultrasound to provide intra-operative quality control. SUMMARY

A method, system and program product are provided for

planning a cathlab intervention with optimal tracking performance. According to one aspect of the present invention, a method for planning a cathlab intervention with optimal tracking performance comprises: determining electromagnetic tracking error as a function of pose for a plurality of possible poses of an x-ray machine, planning an intervention procedure using the x-ray machine, and iteratively determining an optimal pose for the x- ray machine based upon electromagnetic tracking using the determined electromagnetic tracking error for each of the plurality of possible poses.

According to one embodiment, the method further

comprises providing expected accuracy value for current pose during a procedure.

According to one embodiment, the step of determining electromagnetic tracking error as a function of pose, comprises for each of a plurality of poses, measuring the tracking error using a sensor in a plurality of known positions in x-ray space.

According to one embodiment, the tracking error is saved as a three- dimensional image of the operative range of the x-ray machine with gradations of tracking error.

According to one embodiment, the step of iteratively determining an optimal pose comprises iteratively testing possible poses and selecting a pose with the lowest maximum error.

According to one embodiment, the step of iteratively determining an optimal pose further comprises iteratively testing comparable x-ray images for possible poses and selecting a pose with the lowest maximum error that provides adequate x-ray clarity.

According to one embodiment, the clarity of each possible pose is determined from a library of previously captured images for the respective pose.

According to one embodiment, the expected error is dynamically determined during an intervention procedure.

According to another aspect of the present invention, a system is provided for planning a cathlab intervention with optimal tracking performance. The system comprises: at least one processor operably connected with an electromagnetic tracking system and an x-ray system, at least one memory, operably connected with the at least one processor, and a program of instruction encoded on the at least one memory and executed by the at least one processor. The program of instruction, when executed by the processor: determines electromagnetic tracking error for the electromagnetic tracking system as a function of pose for a plurality of possible poses of the x-ray machine, plans an intervention procedure using the x-ray machine, and iteratively determines an optimal pose for the x-ray machine based upon electromagnetic tracking using the determined electromagnetic tracking error for each of the plurality of possible poses.

According to one embodiment, the system further comprises an electromagnetic tracking system and a sensor positioned in known positions in x-ray space, wherein, for each of a plurality of poses, a tracking error is determined as a function of pose by measuring the tracking error with the sensor at each known position in x-ray space.

According to one embodiment, the system further comprises a library of x-ray images from poses comparable to the plurality of poses, and the optimal pose is further determined by testing the library of previously captured images to determine acceptance of a pose.

According to one embodiment, the system further comprises a user interface providing procedural data during an intervention indicating compliance with an error constraint.

According to one embodiment, the user interface further provides a warning when the error constraint is not met.

According to one embodiment, the user interface further provides data for at least one additional procedural parameter.

According to one embodiment, the user interface further modifies at least one constraint or parameter during a procedure.

According to another aspect of the present invention, a computer program product for planning a cathlab intervention with optimal tracking performance is provided. The computer program product comprises a computer readable storage device having encoded thereon a computer-executable program of instruction. The program of instruction comprises: program instructions for determining electromagnetic tracking error as a function of pose for a plurality of possible poses of an x-ray machine, program instructions for planning an intervention procedure using the x-ray machine, and program instructions for iteratively determining an optimal pose for the x-ray machine based upon electromagnetic tracking using the determined electromagnetic tracking error for each of the plurality of possible poses.

According to one embodiment, the computer program of instruction further comprises program instructions for providing expected accuracy value for current pose during a procedure.

According to one embodiment, the program instructions for determining electromagnetic tracking error as a function of pose, comprise program instructions for measuring, for each of a plurality of poses, the tracking error using a sensor in a plurality of known positions in x-ray space.

According to one embodiment, the program instructions for determining electromagnetic tracking error as a function of pose save the tracking error as a three- dimensional image of the operative range of the x-ray machine with gradations of tracking error.

According to one embodiment, the program instructions for iteratively determining an optimal pose comprise iteratively testing possible poses and selecting a pose with the lowest maximum error.

According to one embodiment, the program instructions for iteratively determining an optimal pose further comprise iteratively testing comparable x-ray images for possible poses and selecting a pose with the lowest maximum error that provides adequate x-ray clarity.

According to one embodiment, the program of instruction further comprises program instructions for dynamically determined expected error during an intervention procedure. BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the invention will be more clearly understood from the following detailed description of the preferred embodiments when read in connection with the accompanying drawing. Included in the drawing are the following figures:

Fig. 1 is an isometric view of a system for planning a cathlab intervention with optimal tracking performance according to an embodiment of the present invention;

Fig. 2 is a block diagram of a system for planning a cathlab

intervention with optimal tracking performance according to an embodiment of the present invention;

Fig. 3 is a flow diagram of a method for planning a cathlab

Fig. 4 is a flow diagram of a method for planning for optimal performance with x-ray-EM trade-off;

Fig. 5 is a representation of visualization of tracking accuracy for a plurality of poses for use in planning a cathlab

Fig. 6 is representation of planning a cathlab intervention with optimal tracking performance according to an embodiment of the present invention;

Fig. 7 is a representation of displaying expected EM tracking accuracy for a current pose during an intervention according to an embodiment of the present invention; and

Fig. 8 is an EM dashboard for providing monitoring and control of procedural parameters during an intervention according to an embodiment of the present invention. DETAILED DESCRIPTION

The present invention provides a method, system, and computer program product for planning a cathlab intervention with optimal tracking performance.

According to one embodiment of the present invention, electromagnetic tracking error is determined as a function of pose for a plurality of possible poses of an x-ray machine. An intervention procedure is planned using the x-ray machine. An optimal pose for the x-ray machine is iteratively determined based upon electromagnetic tracking and x-ray performance using the determined electromagnetic tracking error for each of the plurality of possible poses.

Fig. 1 shows a system 300 for planning a cathlab intervention with optimal tracking performance according to an embodiment of the present invention. The system comprises: an EM tracking system 100, an x-ray system 200, and a planning console 310. The EM tracking system 100 is used for tracking the location of a tool, typically a catheter, during a catheter intervention. The EM tracking system 100 comprises a field generator 120 positioned below the patient table 10. The field generator generates an electromagnetic field. The EM tracking system also comprises a sensor 132, such as a coil. The sensor may be embedded in a surgical instrument 130, such as a catheter or may be positioned internal or external to a patient. The electromagnetic field from the field generator 120 induces an electrical current in the sensor 132 with a strength

corresponding to the position and orientation of the sensor 132. A processing unit 110 receives the current signal from the sensor 132 and calculates the position and orientation of the sensor 132. In practice, a plurality of sensors 132 would typically be used to resolve for the six degrees of freedom of the sensors.

The x-ray system 200 is used for visualizing internal structures, fluid movement, tissue movement, and the like during the catheter intervention. A processing system 210, such as a general purpose computer is operably connected to an x-ray machine 220. In the illustrated embodiment, the x-ray machine is a C-arm. The x-ray machine 220 is disposed for taking x-ray imagers of a patient on a table 10. The processing unit 210 processes x-ray images from the x-ray machine 220. The processed image may be presented on a display 240 showing internal structures, fluid movement, tissue movement, and the like during the catheter intervention. The x-ray system 200 may be operably connected with the EM tracking system to show the location and orientation of a surgical instrument 130 with an embedded sensor 132, such as a catheter overlaid on the x-ray images. Alternatively, the x-ray images may be presented separately from the x-ray images for tracking a surgical instrument 130 in 3D image space.

The planning console 310 is used to plan poses for the intervention procedure that provide desired visualization, while minimizing tracking error due to EM interference from the x-ray components, particularly, the x-ray source. The planning console 310 may comprise a processor 311 (Fig. 2), such as a general purpose computer, with a planning program 392 (Fig. 2) loaded on and executed by the computer. The planning console 310 visualizes EM tracking error as a function of various C-arm 220 poses. Then, the planning console 310 plans a procedure with optimal performance through x-ray - EM trade-off. The planning console 310 may further provide correlation between a pose and error showing expected accuracy for a current pose during a procedure.

Fig. 2 is a block diagram of a system for planning a cathlab intervention with optimal tracking performance according to an embodiment of the present invention. In the illustrated embodiment, the EM tracking system 100 comprises an EM tracking console 1 10, which is a general purpose computer connected to the field generator 120 and the sensor 132 through communication connectors 1 16. The communication connectors 116 may be any suitable wired or wireless connection. The EM tracking module 110 comprises a processor 11 1 operably connected to a memory 1 13, such as through a system bus 112. It should be understood that other suitable architectures are also possible within the scope of the present invention. The processor 111 may be any suitable processor, such as one or more microprocessors. The memory 1 13 may be any suitable memory, including but not limited to: RAM, ROM, an internal hard drive, a disk drive, a USB flash drive, or any other memory device suitable for storing program code. The memory 113 has encoded on it a program of instruction 1 19 executed by the processor 1 11 to set and monitor the field generator, receive sensor data, and calculate sensor position and orientation from the field and sensor data. The EM tracking system also comprises one or more displays 114 for presenting a user interface and/or EM tracking information and one or more input and/or output devices 1 15 for entering user inputs, for example.

In the illustrated x-ray system 200, the x-ray console 210 is a general purpose computer connected to the x-ray machine 220 through a communication connection 216. Similar to the EM tracking console, the x-ray console 210 comprises a processor 211 operably connected to a memory 213, such as through a system bus 212. It should be understood that other suitable architectures are also possible within the scope of the present invention. The processor 21 1 may be any suitable processor, such as one or more microprocessors. The memory 213 may be any suitable memory, including but not limited to: RAM, ROM, an internal hard drive, a disk drive, a USB flash drive, or any other memory device suitable for storing program code. The memory 213 has encoded on it a program of instruction 229 executed by the processor 211 to receive and process x- ray data. The x-ray system 200 also comprises one or more displays 214 for presenting a user interface and/or x-ray information and one or more input and/or output devices 215 for entering user inputs, for example.

The planning console 310 comprises a processor 31 1 operably connected to a memory 313, such as through a system bus 312. It should be understood that other suitable architectures are also possible within the scope of the present invention. The processor 31 1 may be any suitable processor, such as one or more microprocessors. The memory 313 may be any suitable memory, including but not limited to: random access memory (RAM), read-only memory (ROM), an internal or external hard drive, a disk drive, a USB flash drive, or any other memory device suitable for storing program code. The memory 313 has encoded on it a visualization application 391 , such as a

visualization tool kit (VTK) for resolving 3D images from x-ray data. The memory 313 also has encoded on it a program of instruction 392 executed by the processor 311 to plan an intervention with optimal tracking performance with acceptable x-ray quality.

The planning console 310 may further comprise one or more communication connections 316 for receiving x-ray and EM tracking data. The communication connections may be Uniform Serial Bus (USB) connectors, internet adapters, or any other connector suitable for sending and/or receiving data from another device, either directly or through a network, such as an intranet or the Internet. The planning console 310 also comprises one or more displays 314 for presenting a user interface and/or tracking and setting information and one or more input and/or output devices 315 for entering user inputs, for example. While the planning console 310, the EM tracking console 110, and the x-ray console 210 are shown as 3 different general purpose computers, any two or all three may be combined into one general purpose computer. Also, any other suitable processing architecture may be used instead of a general purpose computer.

Fig. 3 is a flow diagram of a method for planning a cathlab intervention with optimal tracking performance according to an embodiment of the present invention. The planning program of instruction 392 determines an EM tracking error data as a function of various C-arm poses (Step 410). This determination may be performed, for example, as a weekly calibration. The C-arm 220 is set to various poses, which may comprise a viewing angle, a source to intensifier distance (SID), table 10 orientation, and any other parameter that may affect tracking accuracy. Then a sensor is positioned at predetermined positions and measured to determine tracking accuracy. The tracking accuracy may be represented by a 3D image as shown in Fig. 5, showing the accuracy as a pose visualization 510 with error gradations for the operable range of the C-arm. The error gradations are represented as areas or regions within the operable range of the C- arm for the particular pose, and can be resolved into coordinates in 3D x-ray space. In the illustrated example, the error gradations range from regions with an error of 0 mm to regions with an error of 5 mm.

The calibration to determine the error characteristic as a function of C-arm position may be performed by the planning console 310 directing a user through the physical steps of positioning the C-arm 220 and making error measurements.

Alternatively, the calibration may be performed independently of the planning console 310, such as by the EM tracking console 110 or be user directed, and provided to or retrieved by the planning console.

Prior to a planned intervention, a clinician uses an expected navigation of a surgical tool during the planned intervention to predict the positions of the surgical tool in 3D x-ray space (Step 420). The expected navigation may be determined using a generic image of an anatomical region where the intervention is planned, or the expected navigation may be determined from pre-operative imaging. The planning image is then registered to the 3D x-ray space, and a planned path for the surgical tool is determined in x-ray space. The planning image can be registered or matched to the X-ray space using a number of standard techniques that are well known in literature. Some examples are 2D- to-3D image based registration, or landmark based registration (wherein you choose or know specific landmark positions) or feature based registration.

The planning program 392 iteratively determines the maximum tracking error for the planned path for a plurality of C-arm poses by comparing the determined path in x-ray space to the visualized EM error as a function of C-arm pose to determine the expected accuracy for each of a plurality of poses (Step 430). That is, for each C-arm pose, the planning program determines for each point along the determined navigation path the EM error gradation corresponding to that point in x-ray space. Then, the planning program determines the maximum EM tracking error during the procedure for the selected C-arm pose. The planning program compares the maximum errors for each of the plurality of C-arm poses, and selects the C-arm pose with the optimal or lowest expected error. For example, as shown in Fig. 6, the pose with the lowest maximum error for a particular procedure is a left anterior oblique angle (LAO) of 30 degrees, with a source to intensifier distance (SID) of 700 mm. This setting, for example, gives an estimated maximum error of 1.9 mm.

According to one embodiment, the planning program 392 provides a live correlation between the current pose and error profile (i.e., the error gradations) for that pose to show the expected accuracy for the actual position of the surgical instrument (Step 440). For example, as shown in Fig 7, at a particular point during an intervention with a current C-arm pose, and with the surgical instrument at a current location in x-ray space, the expected error is about 1.9 mm, which is presented to a user on the planning console display 340 (Fig. 1) as an accuracy of about 1.9 mm.

According to one embodiment, the planning program 392, performs an x-ray - EM tracking trade-off as part of the pose selection step (Step 430). As shown in Fig. 4, the planning program 392 identifies a proposed C-arm pose and a determined EM sensor path (in x-ray space) (Step 431). The determined EM sensor path is determined in Step 420, for example. The proposed C-arm pose may be derived from a history of poses previously used for similar procedures, derived from analysis of pre-operative images, supplied as input by a physician, or be identified by any other suitable means.

The planning program 392 calculates the expected EM tracking error from the pose visualizations 510 and the determined path for the EM sensor (Step 432). The 3D coordinates of the sensor location are compared to the pose visualization to determine the gradation of the pose visualization corresponding to the sensor location.

The planning program 392 presents simulated or stored x-ray images comparable to images expected from the proposed C-arm pose to a user on the display 340. The comparable images may be selected from a library of images taken from the same pose or may be simulated images derived from a 3D image constructed from preoperative imaging, or any other method that provides the user with a visual representation of characteristics of an x-ray image useful in determining usability for an intended purpose. Characteristics that may be shown include but are not limited to: foreshortening, presence of imaging artifacts, distortions, truncation of anatomical features, image quality, and optimal viewing angle of anatomical features.

In response to a user's indication, the planning program 392 determines whether or not the comparable x-ray is accepted (Step 434). The user indication may be received through a dialog box, a pull down menu, a prompt, or any other suitable method for receiving a user indication of acceptance or approval. If the comparable x-ray is not accepted, then the program of instruction 392 determines whether or not additional poses are proposed (Step 435). This determination may be made in any suitable manner, such as by checking a stored list of proposed poses to determine whether they have all been tried. Alternatively, the planning program may calculate whether additional poses need to be tried by incrementing various pose parameters and calculating whether the maximum error is increasing.

If additional poses are proposed, then the planning program returns to step 431 and identifies the next proposed pose and calculates the expected error for the new pose. When the comparable x-ray for a proposed pose are accepted (Y at Step 434), the accepted pose is stored (Step 438), and the planning program determines whether or not to test additional poses (Step 435).

When the planning program determines that no additional poses are to be tested (N at Step 435), the planning program selects the best pose (Step 436), and displays information for the selected pose (Step 437). The best pose, according to one embodiment, is the saved pose with the lowest maximum error. Alternatively, the poses may all be tested for accuracy and the comparable x-ray images may be presented for acceptance in accuracy order.

According to one embodiment, the live correlation (step 440) is realized by an EM dashboard. The EM dashboard is available to a clinician during an intervention procedure at a user interface presented on a monitor. The clinician may interact with the EM dashboard through an I/O device such as a mouse or keyboard, or the like. Fig. 8 shows an EM dashboard according to one embodiment of the present invention. The dashboard comprises one or more tools for monitoring and/or controlling procedural parameters during an intervention. The EM dashboard tools may be software programs for monitoring such parameters as error constraints. According to one embodiment, the EM dashboard provides an automatic warning if a preset EM tracking error limit is exceeded. The warning may be a visual image on the display, an audible warning sound, or any other readily perceived stimulus.

The EM dashboard may also present visual images to allow a clinician to visualize haw well previously set constraints are being satisfied. The EM dashboard may also allow a clinician to change constraints. Examples of changing constraints include: changing an average tracking error limit, suggesting modification of the SID, and changes or suggesting changes to any other limit settings or physical settings of the system.

The EM dashboard may present data in the form of intuitive graphs, 3D maps, histograms, and other data visualization methods. The EM dashboard may also comprise tools for directing manual adjustment of for performing automatic adjustment of the patient table and/or the imaging system for increased tracking accuracy. The EM dashboard may further comprise tools for repositioning the navigation system and various interventional tools either through directing manual repositioning or driving the tool controls to automatically reposition them.

The EM dashboard may also load configurations from a previous similar procedures. The invention can take the form of an entirely hardware embodiment or an embodiment containing both hardware and software elements. In an exemplary embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, etc.

Furthermore, the invention may take the form of a computer program product accessible from a computer-usable or computer-readable medium providing program code for use by or in connection with a computer or any instruction execution system or device. For the purposes of this description, a computer-usable or computer readable medium may be any apparatus that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device.

The foregoing method may be realized by a program product comprising a machine -readable medium having a machine-executable program of instructions, which when executed by a machine, such as a computer, performs the steps of the method. This program product may be stored on any of a variety of known machine -readable medium, including but not limited to compact discs, floppy discs, USB memory devices, and the like.

The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device). Examples of a computer- readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk an optical disk. Current examples of optical disks include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W) and DVD.

While the foregoing description is directed to a planning console for use in a cathlab, any interventional suite, like a CT-guided intervention or an MR-guided intervention (in addition to the X-ray C-arms, and adding mobile X-ray units) that makes use of the planning tool and external tracking using EM are contemplated within the scope of the invention. The planning console may also be used in operating room scenarios where EM tracking based planning is envisioned/used in the presence of a large distorter. In fact, the planning console may be used any place where an EM based planning tool is used in a field where larger EM distorters are present. The preceding description and accompanying drawing are intended to be illustrative and not limiting of the invention. The scope of the invention is intended to encompass equivalent variations and configurations to the fall extent of the following claims.

Claims

CLAIMS:

1. A method for planning a cathlab intervention with optimal tracking performance, comprising the steps of:

determining electromagnetic tracking error as a function of pose for a plurality of possible poses of an x-ray machine;

planning an intervention procedure using the x-ray machine; and iteratively determining an optimal pose for the x-ray machine based upon electromagnetic tracking using the determined electromagnetic tracking error for each of the plurality of possible poses.

2. The method of claim 1, further comprising providing expected accuracy value for current pose during a procedure.

3. The method of claim 1 , wherein determining electromagnetic tracking error as a function of pose, comprises for each of a plurality of poses, measuring the tracking error using a sensor in a plurality of known positions in x-ray space.

4. The method of claim 3, wherein the tracking error is saved as a three- dimensional image of the operative range of the x-ray machine with gradations of tracking error.

5. The method of claim 4, wherein iteratively determining an optimal pose comprises iteratively testing possible poses and selecting a pose with the lowest maximum error.

6. The method of claim 5, wherein iteratively determining an optimal pose further comprises iteratively testing comparable x-ray images for possible poses and selecting a pose with the lowest maximum error that provides adequate x-ray clarity.

7. The method of claim 6, wherein the clarity of each possible pose is determined from a library of previously captured images for the respective pose.

8. The method of claim 1, wherein the expected error is dynamically determined during an intervention procedure.

9. A system for planning a cathlab intervention with optimal tracking performance, comprising:

at least one processor operably connected with an electromagnetic tracking system and an x-ray system,

at least one memory, operably connected with the at least one processor; and

a program of instruction encoded on the at least one memory and executed by the at least one processor to:

determine electromagnetic tracking error for the electromagnetic tracking system as a function of pose for a plurality of possible poses of the x-ray machine;

plan an intervention procedure using the x-ray machine; and iteratively determine an optimal pose for the x-ray machine based upon electromagnetic tracking using the determined electromagnetic tracking error for each of the plurality of possible poses.

10. The system of claim 9, further comprising an electromagnetic tracking system and a sensor positioned in known positions in x-ray space, wherein, for each of a plurality of poses, a tracking error is determined as a function of pose by measuring the tracking error with the sensor at each known position in x-ray space.

11. The system of claim 10, wherein the optimal pose is further determined by testing a library of previously captured comparable images for use in determining acceptance of a pose.

12. The system of claim 9, further comprising a user interface providing procedural data during an intervention indicating compliance with an error constraint.

13. The system of claim 12, wherein the user interface further provides a warning when the error constraint is not met.

14. The system of claim 12, wherein the user interface further provides data for at least one additional procedural parameter.

15. The system of claim 12, wherein the user interface further modifies at least one constraint or parameter during a procedure.

16. A computer program product for planning a cathlab intervention withoptimal tracking performance, the computer program product comprising a computer readable storage device having encoded thereon a computer-executable program of instruction comprising:

program instructions for determining electromagnetic tracking error as a function of pose for a plurality of possible poses of an x-ray machine;

program instructions for planning an intervention procedure using the x- ray machine; and

program instructions for iteratively determining an optimal pose for the x- ray machine based upon electromagnetic tracking using the determined electromagnetic tracking error for each of the plurality of possible poses.

17. The computer program product of claim 16 further comprising, program instructions for providing expected accuracy value for current pose during a procedure.

18. The computer program product of claim 16, wherein the program instructions for determining electromagnetic tracking error as a function of pose, comprise program instructions for measuring, foreach of a plurality of poses, the tracking error using a sensor in a plurality of known positions in x-ray space.

19. The computer program product of claim 18, wherein the program instructions for determining electromagnetic tracking error as a function of pose save the tracking error as a three-dimensional image of the operative range of the x-ray machine with gradations of tracking error.

20. The computer program product of claim 19, wherein the program instructions for iteratively determining an optimal pose comprise iteratively testing possible poses and selecting a pose with the lowest maximum error.

21. The computer program product of claim 20, wherein the program instructions for iteratively determining an optimal pose further comprise iteratively testing comparable x-ray images for possible poses and selecting a pose with the lowest maximum error that provides adequate x-ray clarity.

22. The computer program product of claim 21 , wherein the clarity of each possible pose is determined from a library of previously captured images for the respective pose.

23. The computer program product of claim 16, further comprising program instructions for dynamically determined expected error during an intervention procedure.