Patent Description:
Techniques to guide an invasive probe inside a cavity of an organ to target tissue have been previously proposed in the patent literature. For example, <CIT> describes a number of improvements related to computer aided surgery (CAS) utilizing an on-board tool tracking (OTT) system. Some of the improvements relate to methods of providing feedback during a procedure to improve either the efficiency or quality, or both, for a procedure including the rate of and type of data processed depending upon a CAS mode. In an embodiment, to provide navigation assistance during an OTT CAS procedure, an OTT device monitors the position of the associated surgical tool within the surgical field. The OTT CAS system may use none, or one or more reference frames, including one or more position sensors or one or more fiducial markers depending upon the requirements of the OTT CAS procedure being undertaken.

As another example, <CIT> describes a method of guiding an interventional instrument within a patient anatomy that comprises processing a target location within the patient anatomy and receiving a position for a tip portion of an interventional instrument at a first location within the patient anatomy. The method also comprises determining a three-dimensional distance between the first location and the target location and displaying a symbol representing the target location and a symbol representing the tip portion of the interventional instrument. In an embodiment, a rotational orientation of a feature of the distal tip portion may also be displayed by the navigation aid image with a rotation assistance symbol. For example, if a biopsy instrument has a side opening, the side with the opening may be indicated on the navigation aid image with the rotation assistance symbol.

<CIT> describes devices, systems and methods for performing image guided interventional and surgical procedures, including various procedures to treat sinusitis and other disorders of the paranasal sinuses, ears, nose or throat. In some applications, a preoperative tomographic scan (e.g., a CT scan) may be obtained and the image guidance system may be programmed to display the tomographic images on a video monitor along with a real time indication (e.g., cross hairs, an illuminated dot, etc.) of the location of the working device relative to the anatomical structures shown on the tomographic image.

<CIT> describes hybrid magnetic-based and impedance-based position sensing. <CIT> describes an apparatus for performing vidian neurectomy procedure. <CIT> describes multi-axial position sensors printed on a folded flexible circuit board. <CIT> describes a catheterscope 3D guidance and interface system. <CIT> describes a system for medical instrument navigation and targeting.

Certain surgical methods are described with reference to the system of the present invention. Whilst no claim is directed to these methods per se, the system is capable of being used and is intended to be used in such methods.

A distal end section of a probe, such as an ear-nose-throat (ENT) probe used with a guiding system, can be tracked to be visually used as a cursor (i.e., pointer) of a location in a 3D view (e.g., medical image) of a cavity of a patient. For example, an ENT suction tool, or a shaver, can be used in such a way with the TruDi™ ENT tracking system (made by Acclarent, Irvine, California). The medical image can be generated, for example, from a CT or MRI image.

The distal end section of the probe (e.g., an ENT suction device) can be tracked using a magnetic sensor attached to the distal end, with the tracked position projected onto a location on the medical image along a direction of a center longitudinal axis of the distal end (e.g., center of a suction aperture of the suction tool). In this manner, a physician can view a cursor location on the medical image (on a display) as if "viewed" distally from the tool itself.

However, for some clinical procedures, it might be preferable for the user to toggle the image cursor between an image location projected along the center longitudinal direction, and a different image location corresponding to a visually-guiding object disposed on a perimeter of the distal edge of the distal end of the probe. The different image locations are interchangeably viewed as if viewed distally from the tool via virtual crosshairs put, for example, by the physician using a user interface of the position tracking system, on center and perimeter tracked positions on the distal edge of the distal end of the probe.

Embodiments of the present invention that are described hereinafter provide means that allow a user to toggle the displayed cursor on a 3D view (e.g., a medical image) between medical image locations received by projecting the tracked position along the above two different directions. In one embodiment, the tracked object is a guiding bump, as described below. In another embodiment, the distal edge of the tubular distal end section (e.g., nosepiece) is colored to show several angular sections (e.g., four quadrants) that each of can be tracked based on user decision on which of the sections to put the crosshair.

Using a video image from an endoscope (e.g., otoscope) inserted into the cavity, the physician can see the bump or at least part of the angular sections in real time, as well see target tissue (e.g., polyp) and nearby tissue not to affect with the tool (e.g., brain tissue). Based on known orientations of the colored angular sections relative to the object, a processor redefines the object as any of the colored angular sections viewed using the endoscope, and toggles a cursor on the medical image accordingly.

Typically, at a beginning of a medical procedure, frames of reference of the medical image and the magnetic tracking system are registered. The position, direction and angular orientation of the sensor are tracked by the system to enable putting crosshairs at the different tracked positions to thereby enable toggling the cursor on the medical image between the central and tilted directions, as described above.

The disclosed techniques allow a physician to direct the distal edge of the ENT tool to a target an intrabody location with the distal edge of the tool optimally aligned in position, direction, and rotational orientation for performing, for example, a therapeutic procedure, such as ENT suction.

<FIG> is a schematic, pictorial illustration of an ear-nose-throat (ENT) system <NUM>, in accordance with an embodiment of the present invention. In the following description an ENT tool <NUM> in system <NUM> is assumed to be used to perform a suction procedure in the sinuses of a patient <NUM>, although it will be understood that the tool may be used to perform other procedures on the patient.

As is described below, in an embodiment, tool <NUM> comprises a tilted dual axis magnetic sensor <NUM> attached to a distal end (distal end and sensor described in <FIG>) of tool <NUM>, which is tracked during the procedure by a magnetic tracking system <NUM>. For the tracking to be effective in system <NUM>, frames of reference of a medical image <NUM>, e.g., computerized tomography (CT) images of patient <NUM>, and of magnetic tracking system <NUM>, are registered. While CT image <NUM> may typically comprise a magnetic resonance imaging (MRI) image or a fluoroscopic image, in the description herein the image is assumed to comprise, by way of example, a fluoroscopic CT image.

Prior to and during the sinus procedure, a magnetic radiator assembly <NUM>, comprised in the magnetic tracking system, is positioned beneath the patient's head. Assembly <NUM> comprises magnetic field radiators <NUM> which are fixed in position and which transmit alternating magnetic fields into a region <NUM> wherein the head of patient <NUM> is located. Potentials generated by sensor <NUM> in region <NUM>, in response to the magnetic fields, enable the measurement of its position, direction, and angular orientation in the magnetic tracking system's frame of reference.

By way of example, five radiators <NUM> of assembly <NUM> are arranged in an approximately horseshoe shape around the head of patient <NUM>. However, alternate configurations for the radiators of assembly <NUM> may be used, and all such configurations are assumed to be comprised within the scope of the present disclosure.

Prior to the procedure, the registration of the frames of reference of the magnetic tracking system with the CT image may be performed by positioning a magnetic sensor at known positions of the image, such as the end of the patient's nose. However, any other convenient system for registration of the frames of reference may be used.

Elements of system <NUM> are under overall control of a system processor <NUM>. Processor <NUM> may be mounted in a console <NUM>, which comprises operating controls <NUM> that typically include a keypad and/or a pointing device such as a mouse or trackball. Console <NUM> connects to radiators <NUM> and to sensor <NUM> wirelessly and/or via one or more cables. A physician <NUM> uses operating controls <NUM> to interact with the processor while performing the ENT procedure using system <NUM>. While performing the procedure, the processor presents a cursor <NUM> on medical image <NUM> on a screen <NUM> to assist the physician in guiding the distal end to a target tissue location in the sinuses.

Processor <NUM> uses software stored in a memory <NUM> to operate system <NUM>. The software may be downloaded to processor <NUM> in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory.

<FIG> is a side view of a distal end section <NUM> of the ear-nose-throat (ENT) tool <NUM> used in <FIG>, in accordance with an embodiment of the present invention. Distal end section <NUM> comprises a dual axis coil sensor <NUM>, which its two coils (34a, 34b) are aligned non-parallel with each other. Both coils 34a and 34b have their axes of symmetry (340a, 340b) aligned perpendicularly to a direction <NUM> of a central axis of the distal end. For any given direction of the distal end relative to the direction of the magnetic field of system <NUM>, and for any roll angle about axis <NUM>, dual-axis sensor <NUM> allows system <NUM> to find tilted direction <NUM> and center longitudinal direction <NUM> and use the direction as described below.

On insertion of tool <NUM>, distal end section <NUM> of the tool is typically in air, i.e., is in a cavity region <NUM> of a schematically illustrated anatomy <NUM>, that corresponds to a zero Hounsfield Unit (HU) value in <NUM> planes of a medical image, such as a CT image <NUM> of the anatomy. During the medical procedure, the nosepiece is conveniently observed with an endoscope (not shown), which is typically operated by the physician to acquire and display a video image, so that the physician can see the location of the nosepiece relative to anatomy <NUM>. As seen in <FIG>, anatomy <NUM> comprises anatomical features at surface locations <NUM> and <NUM> that the physician wants to view with the endoscope.

In the shown embodiment, the processor projects the position of sensor <NUM> onto the anatomy in directions defined by tracked center position <NUM> and bump <NUM> position over the perimeter of the distal edge of distal end section <NUM>. In the shown embodiment, positions <NUM> and <NUM> define directions <NUM> and <NUM>, respectively. The frames of reference of CT <NUM> image and the magnetic tracking system are registered, so that processor <NUM> can use an actually aimed at anatomical location by distal end <NUM> to mark a matching location on image <NUM> with a cursor. Thus, the tracking system relates the visually viewed locations <NUM> and <NUM> that a physician aiming the ENT tool at these wishes to resolve, to respective locations <NUM> and <NUM> in <NUM> planes of CT image <NUM>.

To select direction <NUM> or <NUM> of the tool relative to anatomy, the physician puts, using a user interface, virtual crosshairs <NUM> and <NUM> on positions, such as positions <NUM> and <NUM>, respectively. The physician may move a crosshair to any other arbitrary tilted location over the distal perimeter, which results in the cursor marking another location than location <NUM> on CT image <NUM>. Therefore, the physician may toggle the cursor on the medical image between a first location <NUM> and a second location <NUM>, that match preselected crosshairs locations <NUM> or <NUM> on the tool, so as to view anatomy locations <NUM> or <NUM> from direction <NUM> and <NUM>, respectively.

Toggling the cursor on the planes of CT image <NUM> between locations <NUM> and <NUM> therein, in correspondence to actual anatomical locations <NUM> and <NUM> pointed at by different portions of distal end section <NUM>, respectively, allows the physician better control on the use of the tool on either marked tissue locations.

Note, only a single cursor is presented at all times on a plane of CT image <NUM>, and showing the cursor for both locations <NUM> and <NUM> in <FIG> is done purely for the purpose of describing the toggling of the cursor according to chosen positions on the medical tool to put at (by software) crosshairs <NUM> and <NUM>.

The magnetic navigation system can further tell the physician how far the nearest tissue location is (e.g., locations <NUM> or <NUM>) from bump <NUM> or center location <NUM>. The processor may display a distance from the selected tracked location on the tool to the nearest tissue region (an area having non-zero HU values) in order to aid the physician in assessing proximity.

<FIG> is a top view of a distal end section <NUM> of the ear-nose-throat (ENT) tool, in accordance with another embodiment of the present invention. In the shown embodiment, dual-axis magnetic sensor <NUM> is the same as in <FIG>.

As seen in <FIG>, the nosepiece of distal end <NUM> is visually marked (e.g., colored) into quadrants <NUM>. In the shown embodiment, one of colored quadrants <NUM> defines a direction 55a while another of colored quadrants <NUM> defines a direction 55b. Based on the known geometry of the distal end, and using sensor <NUM>, crosshairs can be put on any of the position tracked quadrants <NUM>, where in the shown embodiment, the physician have put crosshairs <NUM> and <NUM> on quadrant locations that defines directions 55a and 55b, respectively. As described above, a cursor appearing on a registered medical image, such as <NUM> plane CT image <NUM>, on can be toggled between corresponding locations <NUM> and <NUM>, respectively. Note again, only a single cursor is presented at all times on each plane of a medical image.

While observing the nosepiece with the endoscope, the physician can toggle between the different quadrants, and so choose the cursor for the 3D view to be in a location and direction that corresponds to an angular segment the physician selects to have a crosshair on. For example, based on a physician selection, processor <NUM> can select one of quadrants <NUM> to have the cursor pointing at a location <NUM> on the medical image that corresponds to an anatomy location <NUM> in region <NUM> of anatomy <NUM>, projected along a direction 55a via crosshairs positioned (<NUM>) on that quadrant, or have the cursor pointing at a location <NUM> on the medical image that corresponds to an anatomy location <NUM> in region <NUM> of anatomy <NUM> having non-zero HU, projected along a direction 55b via crosshairs <NUM> positioned (<NUM>) as seen on another quadrant.

<FIG> is a perspective view of a distal end section <NUM> of ear-nose-throat (ENT) tool <NUM> that shows implementations of elements of the ENT tools of <FIG> and <FIG>, in accordance with embodiments of the present invention. Such a perspective view of distal end section <NUM> may be part of a video image taken by the aforementioned endoscope.

In the shown embodiment, coils 34a and 34b of a transverse dual axis sensor <NUM> are formed so that their axes of symmetry 340a and 340b are with an angle α between them. The axes are non-parallel to each other and in typically are closer to be orthogonal (in the shown embodiment α~<NUM> degrees). Dual axis sensor <NUM> is configured to provide different sets of voltage signals according to the rotational orientation of distal end <NUM> about axis <NUM> (seen in <FIG>).

Forming a multi-axis magnetic sensor on a distal end, such as sensor <NUM>, was described in <CIT> which describes a position sensor including a flexible substrate formed into a three-dimensional (3D) shape, which is assigned to the assignee of the present patent application. There, at least first and second field-sensing coils are formed in first and second respective layers of the flexible substrate, such that in the 3D shape the first and second field-sensing coils have first and second respective axes that are not parallel to one another.

<FIG> also visualizes the aforementioned guiding bump <NUM> and angular sections <NUM> (e.g., quadrants <NUM>) that are visually marked (e.g., colored) over distal end <NUM> (i.e., the nosepiece).

<FIG> is a flow chart of a method for toggling a cursor between locations on a medical image using distal end section <NUM> of ear-nose-throat (ENT) tool <NUM> of <FIG>. The process begins with an initial step <NUM>, in which the frames of reference of magnetic tracking system <NUM> and a medical image, such as derived from CT images of patient <NUM>, are registered, as described above. In order to perform registration with the medical image, magnetic tracking system <NUM> is activated and is used to track the position, direction, and angular orientation of dual axis sensor <NUM>, as described above. The tracking is assumed to be updated in real time.

In an insertion step <NUM>, physician <NUM> inserts distal end section <NUM> of tool <NUM> into a nostril of patient <NUM>. Once inserted, using the signals from sensor <NUM>, processor <NUM> finds locations on the medical image of nearest internal elements of patient <NUM> from virtual crosshairs positioned on distal end section <NUM> of tool <NUM>, in a range finding step <NUM>.

Next, at a cursor placement step <NUM>, processor <NUM> places a cursor over the medical image, so as to point to the nearest internal element of patient <NUM> to the specified location of distal end section <NUM> of tool <NUM>.

At a cursor toggling step <NUM>, physician <NUM> toggles the cursor on the medical image between two imaged locations that correspond to the crosshairs put at the two tracked locations on the distal end section <NUM> of tool <NUM>. As the physician moves the distal end the process repeats itself, as indicated by the dashed direction line: the cursor locations on the medical image change while the physician continues to move the device or toggle the cursor.

The example flow chart shown in <FIG> was chosen purely for the sake of conceptual clarity. <FIG> shows only steps relevant to embodiments of the present invention. Other steps, such as selecting tracked positions other than center <NUM> and bump <NUM> on the distal end section <NUM> of tool <NUM> to put the crosshairs on and subsequently toggle the cursor between newly selected respective locations on the medical image are omitted.

Although the embodiments described herein mainly address ENT applications, the methods and systems described herein can also be used in other applications, such as in cardiac, neurological, or ophthalmic applications.

Claim 1:
A system (<NUM>), comprising:
a probe (<NUM>), comprising a tubular distal end section (<NUM>) configured to be inserted into a cavity (<NUM>) of a patient, wherein the distal end section comprises:
a visually guiding object (<NUM>, <NUM>) disposed over a perimeter of a distal edge of the distal end section; and
a magnetic field sensor (<NUM>) comprising two sensor coils (34a, 34b) aligned non-parallel with each other, the magnetic field sensor attached to the distal end section, and having:
a first axis of symmetry (340a), of one of the coils, which is aligned perpendicular to a central longitudinal axis (<NUM>) of the distal end section; and
a second axis of symmetry (340b), of the remaining coil, which is aligned perpendicular to the central longitudinal axis of the distal end section and not parallel to the first axis of symmetry; and
a processor (<NUM>) of a magnetic tracking system (<NUM>), which is configured to:
using signals received from the magnetic field sensor coils, calculate a position, direction and rotational orientation of the distal end section in the cavity of the patient; and
register the measured position with a medical image;
characterised in that the processor is further configured to:
using the calculated direction and rotational orientation, find in the medical image:
a first anatomical surface location (<NUM>) along the direction of the central longitudinal axis; and
a second anatomical surface location (<NUM>) along a direction (<NUM>) from the calculated position through the visually guiding object; and
toggle a cursor (<NUM>) between the first and second anatomical surface locations on the medical image on a display.