WO2020081725A1

WO2020081725A1 - Biopsy navigation system and method

Info

Publication number: WO2020081725A1
Application number: PCT/US2019/056594
Authority: WO
Inventors: Rizk El-Galley; Joseph Mcginty
Original assignee: El Galley Rizk
Priority date: 2018-10-16
Filing date: 2019-10-16
Publication date: 2020-04-23

Abstract

A system for image guided delivery of a medical tool to a target site uses ultrasound, infrared, and/or other types of communication between a reference guide fixed to a location on a patient and the tool to measure the position and orientation of the tool relative to the reference guide. The position and orientation can be superimposed on a medical image to guide the tool to the target site. The system is applicable to non-medical tools with or without imaging.

Description

TITLE OF THE INVENTION:

Biopsy Navigation System and Method

BACKGROUND OF THE INVENTION:

Field of the Invention

The present invention relates generally to tracking the position and orientation of a tool or implement. Some embodiments of the invention relate more specifically to medical apparatus, methods, systems, and non-transitory computer-readable storage media for navigating a medical instrument, such as a biopsy needle, within the body of a patient. More specifically, embodiments of the invention relate to systems and methods for image guided medical and surgical procedures in which images are used to indicate the relative positions of a medical instrument and locations inside the body of a patient.

Description of Related Art

Minimally invasive medical procedures have become common alternatives to traditional surgical interventions. Precise computed tomography (CT) and/or fluoroscopy image guidance is an important feature for many percutaneous procedures including tissue biopsies and ablations, injections, and abscess drainage. Image guided minimally invasive surgical procedures involve the use of scans, for example x-ray scans, obtained before and/or during a surgical procedure to generate images that are used by a surgeon to guide a surgical instrument during the surgical procedure.

Percutaneous image guided procedures involve the acquisition of initial images and the determination by an operator of a desired surface entry point, trajectory angle, and penetration distance for a needle that is manually directed to a target site in an organ or a tissue. The desired surface entry point for a procedure may involve the use of a standard metallic fiducial and grid with penetration distance measured using initial images. Images are obtained in a region of interest with a radio-opaque grid on a surface of the patient to plan an optimal needle trajectory and needle depth to reach an anatomic target. The surface entry point for the needle is marked with a fiducial marker and the operator slowly advances the needle and adjusted as needed using image guidance until the target is reached. Absent visual references, the operator may unintentionally deviate from the correct needle angle, particularly as the needle is advanced deeply or encounters interfaces of tissues with different densities. Correction of the needle angle at depth is only possible for very small needle angle errors. Significant errors in needle angle require the needle to be withdrawn, followed by reinsertion. This increases tissue injury and exposure to pain and/or sedation and x-rays when fluoroscopy is used or ionizing radiation when CT is used. During image guided surgery, needle placement involves an iterative cycle image acquisition and needle movement in which successive images are used to track the movement of a needle relative to visualized anatomical structures and a fiduciary marker. For example, three-dimensional movement of a needle can be tracked using a combination of two fluoroscopic images taken from two angles, usually from the top down and from side to side. The delay of needle movements between successive image capture is significant and, if eliminated, would reduce the duration of the procedure. A reduction in the number of iterations of image capture and needle movement would reduce the total exposure of the patient to x-rays, or ionizing radiation in the case of CT guided surgery.

The number of iterations of image capture and needle movement can be reduced by sensing the timed position and orientation in space, or pose, of the needle and projecting, or superimposing, the pose of the needle onto two-dimensional or 3-dimensional preoperative images of the patient along with fiduciary marks to provide reference points. The process may involve using a computer to translate the pose of the needle in a reference frame of the tracking process to the reference frame of the images with the aid of fiduciary marks or other reference element in the image. A surgeon may guide a surgical tool within the body of the patient by viewing an image indicating the position and orientation of the needle, superimposed on and registered with one or more fluoroscopic images of the body.

One approach that has been proposed to track the position of a surgical instrument involves the use of radio frequency (RF) sensors. For example, the position and orientation a biopsy needle or catheter can be measured using RF fields with the three-dimensional position of the needle displayed by superposition of a graphic symbol on static X-ray images obtained at two different view angles. A disadvantage to the use of RF fields involves interference by RF signals produced by electronic devices used in or near the operating room, which may cause inaccuracies and/or require that the components of the RF sensor system be isolated.

An approach proposed for brain surgery is to use an array of microphone sensors mounted to the ceiling of an operating room in a line of sight with a surgical probe having sound emitters that interact with the microphone array and with a microphone array on a ring fixed to the head of a patient. Sound signals received by both microphone arrays can be used to track the position of the probe relative to the microphone arrays. One drawback to the use of ultrasound is that, when used over a wide area, the speed of sound may not be uniform throughout the area due to variability in temperature or other environmental factors. A temperature compensation signal may be used to establish a reference velocity of sound, but variations in temperature in different parts of an operating room comprising multiple heat sources and sinks may cause inaccuracy and/or require multiple compensation signals. While a number of solutions have been proposed to reduce the number of iterations of image capture and needle movement and thereby reduce the duration of image guided procedures and exposure to potentially harmful radiation, the proposed solutions suffer from various drawbacks affecting their accuracy and/or requiring expensive or complex components that make them expensive and/or insufficiently reliable.

BRIEF SUMMARY OF THE INVENTION:

Embodiments of the present invention preferably seek to mitigate, alleviate or eliminate one or more deficiencies, disadvantages or issues in the art, such as the above-identified, singly or in any combination, by providing systems, apparatus and methods according to the appended patent claims. Embodiments of the present invention also seek to expand the technical solutions disclosed herein, singly or in any combination, to systems, apparatus and methods of guiding tools or implements with the aid of a reference guide.

In one aspect, the invention provides a system for image guided delivery of a medical device, such as a needle, trocar, implant, stillette, or catheter, to a target site inside the body of a human or non-human patient. The system may be used in combination with medical imaging techniques including fluoroscopy, computed tomography (CT), magnetic resonance imaging (MRI) ultrasound, and positron-emission tomography (PET). The pose, or position and orientation in space, of the medical device, e.g. a needle, is tracked relative to a reference guide positioned in apposition to an entry point into the body of the patient. The reference guide is fixed relative to the patient and may serve as a guide for a piercing tool at an entry point in addition to providing a frame of reference for tracking the pose of the piercing tool in real time as it moves into the body to a target site. The pose of the reference guide in the reference frame of an imaging system may be determined by taking images of the reference guide in place in apposition to the body. This may be facilitated by fiduciary marks on the reference guide. The pose of the piercing tool may be translated from the reference frame of the reference guide to the reference frame of an imaging device to superimpose the pose of the piercing tool on images that include the target site. Additionally or alternatively, the reference frame of the reference guide and the reference frame of an imaging device may be translated to a common reference frame for image display and superimposition.

The position and orientation of the piercing device relative to the reference guide is determined by measuring distances between one or more points on the piercing device and points on the reference guide and measuring angles between a plane of the reference guide and the longitudinal axis of the piercing device. The distances may be determined using range finding sensors including ultrasonic, laser, optical sensors or combinations of these. Angles may be determined from measured distances between one or more points on the piercing device and different points on the reference guide and/or by accelerometry.

In another aspect, the invention provides a system for image guided delivery of a tool to a target site, optionally in combination with industrial tomography techniques.

In yet another aspect, the invention provides a piercing device for a system for image guided delivery of a medical device.

In a further aspect, the invention provides a reference guide for a system for image guided delivery of a medical device.

In yet another aspect, the invention provides a method for image guided delivery of a medical device.

In yet another aspect, the invention provides a non-transitory computer-readable storage media comprising software for implementing a method according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS:

The elements of the drawings are not necessarily to scale relative to each other, with emphasis placed instead upon clearly illustrating the principles of the disclosure. Like reference numerals designate corresponding parts throughout the several views of the drawings in which: Fig. 1 is an elevated proximal perspective view of one embodiment of a biopsy guidance system;

Fig. 2 is an elevated distal perspective view of one embodiment of a biopsy guidance system; Fig. 3A is an elevated distal perspective view of one embodiment of a piercing device of a biopsy guidance system;

Fig. 3B is a top, cross sectional view of an embodiment a piercing device comprising a guide; Fig. 4 is an enlarged distal perspective view of a proximal portion of one embodiment of a biopsy guidance system;

Fig. 5 is an enlarged proximal perspective view of a proximal portion of one embodiment of a biopsy guidance system;

Fig. 6 is a flow chart of an exemplary method for guiding a biopsy needle using a guidance system according to the invention; and

Fig. 7 shows directions of data flow between modules of computer software for performing a method for real time tracking of the position of a tool.

DETAILED DESCRIPTION OF THE INVENTION:

All art specific terms used herein are intended to have their art-accepted meanings in the context of the description unless otherwise indicated. All non art specific terms are intended to have their plain language meaning in the context of the description unless otherwise indicated. In this description, the word“needle,” unless otherwise indicated, is meant to include hollow or solid needles used in medicine as well as other semi-rigid, needle-shaped medical instruments that are used to pierce into a body, such as a trocar or a cannula. A needle is typically straight but may also comprise curves and/or bends. Semi-rigid medical needles typically do not bend or flex when encountering soft tissues but may bend or flex when encountering bone or cartilage.

Figs. 1 and 2 are drawings showing an embodiment of components of a system for image guided surgery 100 comprising a piercing device 101 and a reference guide 102. The piercing device 101 comprises a housing 110 that is configured to act as a hand grip for manipulation of the device by an operator during use. The housing 110 is at the proximal end of the device with respect to an operator. The housing is fixed to a needle 111 , which extends from the housing 110 in a distal direction relative to an operator.

The needle may be any type of solid or hollow needle designed for piercing the body of a subject. The needle may be, for example, a trocar or a cannula having a lumen 111a that may be used to deliver a medical tool or implant to a target site in the body. The needle 111 is normally made of a medical grade stainless steel that can be sterilized using common medical sterilization methods such as autoclaving. The needle 111 for use with a human subject is preferably 10 cm to 20 cm in length. The length of needle 111 may be greater or smaller for different procedures and/or for different types of subjects depending on their size and/or the depth of the target tissue under the skin.

The piercing device 101 may comprise a passage 113 that is configured for the insertion of a flexible medical device such as a needle, catheter, or wire into a proximal opening 118 of the passage 113 and into the lumen 111a of the needle 111. This arrangement facilitates the delivery of medical devices such as biopsy needles, catheters, and medical implants to interstitial locations within the body. The proximal opening 118 in is shown as being off center but may be located centrally on the proximal side of the housing 110 or on a lateral side of the housing.

The needle 111 is reversibly or permanently fixed to the housing 110 so that the needle cannot move relative to the housing. Reversible means for fixing the needle to the housing may include clamping, snapping, and/or quick release means. Permanent fixing may comprise adhesive, screws, bolts, rivets or combinations of these. The needle 111 may pass through the center of the housing 110 to a proximal opening 118 located on the proximal end of the housing 110. For an embodiment with such an arrangement, the position of the ultrasonic receiver 114 may be changed as described in more detail below. Additional support for fixing the needle 111 relative to the housing may be provided by one or more support struts 112 as shown in Figs. 1-5. A segment of the passage 113 may be embodied as a support strut 112 that forms part of an enclosed passage 113 from the proximal opening 118 to the lumen 111a of the needle and may comprise a curved portion of the needle 111. Entry of a flexible medical device into the lumen 111a of the needle 111 may be through an opening in, or in apposition to, the proximal end of the needle 111. In a preferred embodiment, a proximal portion of the needle 111 is curved to form the passage 113. For such an embodiment, the needle 111 may be permanently fixed to the housing 110 or reversibly connected to the housing, for example via clamping, form fitting, pressure-fitting, screw attachments or combinations thereof.

The embodiment shown in Figs. 1-3 comprise an ultrasonic receiver 114 fixed to the housing 110 with the ultrasonic receiver 114 facing the distal end D of the needle 111. In this embodiment, the ultrasonic receiver 114 is oriented to receive ultrasonic signals from ultrasonic transmitters 123L.123R separated by a gap distance G on reference guide 102. Ultrasonic signals received by receiver 114 are used to determine the distance, or range, dR,dl_ (Fig. 5) from the receiver 114 to the two ultrasonic transmitters 123R.123L, respectively. These distances and the known length of the needle 111 are used to calculate the distance dD of penetration into the subject through a needle entry point. Typically, this distance is the distance between the distal end of the needle 111 and the the back side of the reference guide positioned in apposition to an entry point identified on the skin of the subject. The distance dD, which may be considered the depth of the needle tip in the body, may be determined based on the distance between the ultrasonic receiver 114 and ultrasonic transmitters 123L.123R the known length of the needle, and an initial measurement of dl_ and dR when the tip, or distal end, of the needle 111 is positioned at an entry point on the skin of the subject. A method for finding the distance dD is described in more detail further below.

Ultrasonic receiver 114 is shown as being centrally located on the distal end of housing 110 with support struts 112 fixing the needle 111 to the housing 110. The central aperture visible may be a part of the receiver or it may be an opening in the housing 110 behind which the ultrasonic receiver 114 is located. The struts 112 do not interfere with ultrasound transmission from the transmitters 123L.123R to the receiver 114. For alternative embodiments comprising an ultrasonic transmitter on the housing 110 and ultrasonic receivers on the reference guide 102, or in which laser light is used in place of ultrasound for measuring dD, dl_, and dR, the needle 111 is preferably fixed to the housing 110 without the use of struts 112.

Fig. 3B illustrates that the ultrasonic receiver 114 and may be positioned to be out of the direct line of sight of the ultrasonic transmitters 123L.123R by the inclusion of a hollow tube acting as a guide 114b configured to guide ultrasonic pulses from a first open end 114a facing the transmitters 123L.123R to the ultrasonic receiver 114. The ultrasonic receiver is preferably positioned centrally within the guide 114b or centrally at a second open end 114c not facing the ultrasonic transmitters 123L.123R. The second open end 114c may be located at an opening in the housing 110 on a surface of the housing that is not facing the ultrasonic transmitters. The second open end 114c may be located inside the housing 110 where ultrasound pulses that have passed through the guise 114b can disperse. The example shown in the figure comprises a guide 114b having a constant diameter that bends approximately 90° but the constant diameter and degree of curvature are not critical. For example, the guide may be a tube having a larger diameter at the first open end 114a than at the second open end 114c or vice versa and the curvature may be more or less than 90°, for example 0°, 15°, 30, 45°, 60°, 120°, or 180°. For the purposes of measuring the distances dR and dl_ (Fig. 5), the known distance from the first open end 114a to the receiver 114 may accounted for within the programming of the microprocessor 402 (Fig. 4).

Fig. 3B illustrates that the needle 111 and the guide 114b may be configured such that the needle 111 passes through the first open end 114a of the guide 114b. The figure shows a distal portion of the housing 110 with the needle 111 exiting at the center of the housing 110 through the first open end 114a of the guide 114b. This arrangement provides an embodiment in which ultrasound pulses from ultrasonic transmitters 123L.123R pass around the needle 111 and are guided to the ultrasound receiver 114 by guide 114b. The needle 111 is preferably positioned centrally with respect to the first open end 114a of the guide 114b so that rotation of the housing 110 with respect to the ultrasonic transmitters 123L.123R does not influence the distances measured between either of the transmitters and the first opening 114a. Another advantage of positioning the needle centrally within the housing is that the needle may extend through the housing 110, which serves as a grip for the user, to the proximal opening 118 with the proximal end of the needle optionally serving as the passage 113.

The needle 111 may be positioned off-center with respect to the the housing 110 and/or the first opening 114a or the ultrasonic receiver 114 in the absence of a guide with known offset direction and distance being used to compensate for rotation of the housing as measured, for example, by an accelerometer fixed with respect to the housing 110. The embodiment shown in the figure is for an ultrasound emitter and receiver system, however the same principles apply to other types of emitter-receiver systems disclosed herein.

Ultrasound data allows the calculation of the angle a between a line between the ultrasonic transmitters 123L.123R and the longitudinal axis A of the needle 111. In this example, reference guide 102 comprise a housing 120 having opposing planar surfaces with transmitters 123L.123R positioned in the same plane equidistantly from reference point 125 (Fig. 5). Additional transmitters may be positioned on the reference guide allowing the calculation of additional angles between the plane of the reference guide 102 and the longitudinal axis A of the needle 111. For example, and with reference to Fig. 1 , the reference guide 102 may comprise a third ultrasound transmitter positioned in the same plane as transmitters 123L.123R and bridging the gap 121 so that an angle perpendicular to angle a may be measured. With two angles and the distance dD, the pose of the piercing device 101 relative to the reference guide can be determined. In an alternative embodiment to that shown in the figures, the piercing device 101 may comprise an ultrasonic transmitter while the reference guide 102 comprises two or three ultrasonic receivers. The reference guide 102 may comprise a microprocessor 505 configured for processing ultrasonic ranging data to calculate the distances between the ultrasonic receivers and the ultrasonic transmitter on the piercing device 101 or the calculations may be performed by the remote computing device 502 communicating with microprocessor 505 or the ultrasonic receivers.

To calculate the distances between each of the ultrasonic transmitters 123L, 123R and the ultrasonic receiver 114, the time required for transmitted pulses to reach the receiver must be known. The receiver must also know whether a received pulse originated from transmitter 123L or transmitter 123R. This may be accomplished by setting the sound frequencies of the two transmitters to different values and/or sending instructions to one or the other of the transmitters 123L.123R before each transmitted pulse or series of pulses. The needles used for medical procedures are typically no longer than 20 cm for human subjects, but may be longer or shorter depending on the size of the subject and/or location of the tissue to be reached. This results in a limited distance dD being measured corresponding to dD between ultrasonic emitters and receiver(s). As a consequence, the ultrasonic ranging measurements are more accurate and precise than those of ultrasonic ranging systems that cover a larger volume because the speed of sound is constant with respect to the area in which ultrasound measurements are being made. Time variations in the speed of sound may be accounted for by periodic reference pulses to calibrate the ultrasound system to the speed of sound at time intervals.

Communications between the piercing device 101 and reference guide 102 is preferably by infrared (IR) transmissions. The embodiment shown in the Figs. 1-5 comprises an IR transmitter 115 and an IR receiver 116 fixed to the housing 110 of the piercing device 101 to communicate with IR receiver 125 and IR transmitter 126 fixed to the housing 120 of the reference guide 102. An advantage of using IR frequencies for this communication is that it provides high speeds required for controlling the ultrasonic ranging system and it avoids possible interference from mobile phones and other electronic devices. Bluetooth latency, for example, is too long for communication between the reference guide 102 and the piercing device 101 in this system.

In an alternative embodiment to those shown in the figures, the ultrasonic range finding system may be replaced by a laser range finding system. For example, ultrasonic receiver 114 and transmitters 123L.123R may be replaced by a laser range finding system comprising two single axis laser range finding sensors in place of transmitters 123L.123R and a reference reflective marker on the housing 110 in place of receiver 114. In another alternative embodiment, a two-dimensional laser range finding device fixed to the needle 111 of the piercing device 101 may be oriented to toward the proximal planar surface of the reference guide 102 to generate point cloud data from which dD, a first angle a, and a second angle perpendicular to angle a may be derived. Struts 112 are preferably not present in embodiments comprising laser range finding systems and may not be required for an embodiment in which the needle 111 extends into and is attached to the housing 110. In yet another alternative embodiment, the ultrasonic range finding system may be replaced by a stereo optical range finding system. For example, ultrasonic receiver 114 and transmitters 123L.123R may be replaced by an optical range finding camera and optical fiduciary markers.

The reference guide 102 may comprise an opening 121 optionally comprising a cradle point 125 that may be used as a physical guide for steadying the needle 111 near an entry point on the subject. The cradle point 125 may be at the vertex of a v-shaped opening 121 as shown in the figures but the shape of the reference guide 102 and opening 121 may be different from that shown. For example, the opening 121 may be circular with a diameter not much larger than the needle 111 or the reference guide 102 may be u-shaped or have the shape of a bar, a ring, or a polygon with or without an opening comprising a cradle point. An advantage provided by the opening 121 is the ability to position the reference guide 102 on a patient so that the ultrasonic emitters 123L.123R may be located on opposite sides of a surgical entry point. The thickness of the reference guide housing 120 may be uniform or variable In use, the reference guide 102 is preferably placed so that a line between the ultrasonic emitters 123L.123R is close to horizontal with respect to gravity. This provides an angle a that is substantially perpendicular to a vertical angle with respect to gravity measured by the accelerometer 401. The wide end of opening 121 helps the operator to see the planned entry pint for the needle 111. The open end also allows removal of the reference guide 102 without withdrawing the needle from the patient, if necessary.

For the embodiments shown in Figs. 1-5, the pose of the piercing device 101 , including needle 111 , relative to the reference guide 102 is calculated using distance dD, a first angle a, and second angle measured in plane different to the plane of angle a. Both angles may be measured relative to the plane of the reference guide 102, but in different directions. The second angle is preferably a vertical angle with respect to gravity measured using an accelerometer 401 fixed relative to the needle 111. The piercing device shown in Fig. 4 comprises an accelerometer 401 mounted to a circuit board 400 that is fixed to the housing 110. The accelerometer 401 , for example a three-axis solid state accelerometer, senses acceleration due to gravity and measures the timed vertical angle of the housing 110, and thereby the needle 111 , with respect to gravity. A microprocessor 402 in communication with the accelerometer receives the timed vertical angle data and timed distance data from the ultrasonic receiver 114 to calculate the pose of the needle 114 relative to the reference guide 102, which may be transmitted wirelessly by transmitter 403 to a remote computing device 502 (Fig. 5) for further processing. The remote computing device 502 receives real time position data in the reference frame of the system 100 and translates the position of the needle 114 to a display reference frame, which is superimposed on one or more images displayed on a display 501 communicating with the remote computing device 502. The images may be two-dimensional or three-dimensional images taken before and/or during surgery.

Electronic components of the piercing device are preferably powered by a rechargeable battery battery (not shown) that may be recharged via charging port 119. The charging port 119 may additionally or alternatively serve as a wired communications connection to the microprocessor 402, accelerometer 401 , and/or transmitter 403 for transfer of data and/or software/firmware. The electrical components are preferably contained within the housing 110 as shown but one or more of the components may alternatively be distributed on or around the housing.

Fig. 6 is a flowchart of one embodiment of a method for tracking the position and orientation of a medical device. This example involves the use of a reference guide 102 and a piercing device 101 comprising an accelerometer 401 and ultrasonic sensors to track the position and orientation of the needle 111 during an image guided medical procedure.

Before the procedure beings, one or more images of the subject encompassing a treatment site are taken. For example, a horizontally oriented lateral image and a vertically oriented downward image may be obtained by fluoroscopy. The two images may be displayed separately or combined into one image. In another example, an image may be obtained using a tomographic method. Each image comprises one or more standard fiduciary marks caused by one or more standard fiduciary markers of known dimensions. The reference frame of the imaging system may be converted to mm, for example, using a pixel to pixels per mm conversion.

A computer implemented method for tracking and displaying the position and orientation of the needle may be performed using software stored on non-transitory computer-readable storage media associated with a computer communicating with a visual display. The software comprises modules of computer code for running algorithms that perform the computer implemented method.

The length of needle 111 may be known and preprogrammed in software or it may be selectable on a graphical user interface or entered via a data input module of the software. The orientations of the images used, e.g. angle relative to horizontal, may be entered manually and received by the program. Additionally or alternatively, the computer may be connected to the imaging device and comprise software code for receiving image orientation data from the imaging device including the orientation of the imaging device associated with each image used.

If the imaging device does not comprise a means for automatically tracking the orientation of the images taken, an orientation tracking device may be attached to the imaging device to track the orientation of the images taken. The orientation tracking device may be a mechanical apparatus attached to the imaging device, such as an x-ray tube, that physically measures angle between the emitter/detector and the surface the body is on or between the emitter/detector and a reference orientation (e.g. vertical or horizontal). The orientation tracking device may be an accelerometer placed on a portion of the imaging device that moves with the emitter/detector pair and measures the angle with respect to gravity for transmission to the computing device 502. Additionally or alternatively, the system may comprise a device, e.g. an accelerometer fixed to an x-ray tube or other imaging radiation emitter to send signals to the computing device 502 including information on 3D angles of the radiation source. This information may be used to adjust the alignment of images in 3D.

The reference guide is placed on the subject in apposition to an entry point for the needle. The distal end of the needle 111 is contacted with the entry point with the housing of the piercing device 101 gripped by the operator. The reference guide 102 and piercing device 101 are preferably oriented such that the angle of the needle is 45 degrees or less with respect to the horizontal and angle a that is close to 90 degrees. The piercing device 101 , reference guide 102, and/or the display 501 may provide a visual and/or audible signal indicating that the piercing device 101 is positioned relative to the reference guide 102 with angle a at 90 degrees or 90 degrees +/- a tolerance value that may be selected or preprogrammed. With the distal end of the needle 111 in contact with the entry point, the system is calibrated to set the needle depth or dD to zero.

As the needle penetrates the skin and enters tissues in the body of the subject, dD, angle a, and the vertical angle of the needle with respect to gravity are measured in a reference frame of the system 100. These real time measurements may be performed by a measurement module that performs the algorithms required for the measurements (Fig. 7). The units measured are scalable to the reference frame of the display image, which may be, for example, in mm or multiples thereof. For example, dl_, dR, and dD may be measured with a resolution of 0.25 mm using a measurement scaled to 40 measurement units per cm. These measurements, along with those of the accelerometer 401 may be scaled by a measurement conversion module to the same scale as the medical image(s) on the display, the scale of which may be determined using standard fiduciary markers of known dimensions. Additional images may be taken during the procedure to compensate for any movement of the reference guide relative to the patient and/or movement of tissues in the patient caused by shifting of the patient’s body during the procedure.

Embodiments of the system 100 in which the piercing device comprises an accelerometer 401 may be configured to measure a rotational angle, or roll, of the needle 111 , which may or may not be indicated in the needle orientation superimposed on the medical image(s).

The invention has been described with the aid of particular examples and primarily in the context of image guided surgery. The systems, apparatus, and methods described herein are not intended to be limited to medical use. The piercing device 101 may be a non medical instrument or tool for which the pose is to be determined with the aid of the reference guide. The reference guide 102 may be fixed with respect to any structure or working space so that the pose of the tool or instrument may be determined with respect to the reference guide and to a fixed structure to which the reference guide is affixed or a working space near the fixed position of the reference guide..

For example, the housing 110, rather than being attached to a needle, may be attached to a rotating tool such as a drill or screw diver. Software present in the microprocessor 402 and/ or the computing device 502 may monitor the depth and angle of the rotating tool with respect to the reference guide 102. The measured values may be reported to a human or robotic operator to control and/or achieve a desired depth and angle of a hole or a connection.

Claims

CLAIMS:

1. A system configured for image guided delivery of a medical tool to a target site in a body, said system comprising:

a piercing device comprising a needle configured for piercing the body;

a reference guide;

a means for determining a distance between a point on the piercing device and a point on the reference guide;

a means for determining a first angle between the needle and a plane of the reference guide;

a means for determining a second angle between the needle and a plane of the reference guide; and

a means for transmitting timed data including said distance, said first angle, and said second angle to a computing device.

2. The system according to claim 1 , wherein the means for determining the distance between a point on the piercing device and a point on the reference guide comprises ultrasonic range finding, laser range finding, or any combination of these.

3. The system according to either of claims 1 and 2, wherein the means for determining the distance between a point on the piercing device and a point on the reference guide comprises an ultrasonic transmitter on one of said piercing device and said reference guide and an ultrasonic receiver on the other of said piercing device and said reference guide.

4. The system according to any of claims 1-3, wherein the means for determining the first angle between the needle and the plane of the reference guide comprises ultrasonic range finding, laser laser range finding, or any combination of these.

5. The system according to any of claims 1-4, wherein the means for determining the first angle between the needle and the plane of the reference guide comprises two ultrasonic transmitters on said reference guide and an ultrasonic receiver on said piercing device.

6. The system according to any of claims 1-5, wherein the means for determining the second angle between the needle and the plane of the reference guide comprises ultrasonic range finding, laser range finding, accelerometry, or any combination of these.

7. The system according to claim 6, wherein the means for determining the second angle between the needle and the plane of the reference guide comprises two ultrasonic transmitters on one of said piercing device and said reference guide and an ultrasonic receiver on the other of said piercing device and said reference guide.

8. The system according to either of claims 6 and 7, wherein the means for determining the second angle between the needle and the plane of the reference guide comprises an accelerometer attached to the piercing device and fixed with respect to the needle.

9. The system according to any of claims 1-8, and further comprising a computing device functionally coupled to a display device, said computing device comprising software configured to superimpose a real time position and orientation of the needle over a medical image.

10. The system of claim 9, wherein said computing device comprises software configured to: receive image data from an imaging device collecting image data of the body;

translate the pose of the needle and the image data to a common reference frame;

display an image of the body in the common reference frame on the display device; and superimpose the real time pose of the needle onto the image of the body.

11. The system according to any of claims 1-10, and further comprising an orientation tracking device configured to measure orientation data indicating the orientation of an imaging device and provide the orientation data to the computing device.

12. A piercing device for use with the system according to either of claims 5 and 8, said piercing device comprising:

a needle fixed to a housing, said needle being configured to pierce into the body;

an ultrasonic receiver fixed to the housing and positioned to receive ultrasonic pulses from the reference guide;

an accelerometer fixed to the housing; and

a processor communicating with said ultrasonic receiver, said accelerometer; and ultrasonic transmitters

wherein said ultrasonic receiver and said processor are configured to measure said first angle and

wherein said second angle is measured with respect to gravity and said accelerometer and said processor are configured to measure said second angle.

13. The piercing device of claim 12, wherein the ultrasonic receiver is mounted to the housing to face the distal end of the needle.

14. The piercing device of claim 12, wherein the housing comprises an ultrasonic guide having a first open end facing the distal end of the needle and a second open end not facing the distal end of the needle and the ultrasonic receiver is positioned within the guide or near the second open end.

15. The piercing device either of any of claims 12 to 14, further comprising an infrared (IR) transmitter and an IR receiver fixed to the housing and directed in the direction of the distal end of the needle and configured to provide communication between said piercing device and said reference guide.

16. The piercing device of any of claims 12, to 15 further comprising a wireless transmitter configured to provide wireless communication between said processor and a remote computing device and wherein said communication comprises information including said distance, said first angle, and said second angle.

17. The piercing device any of claims 12, to 16, wherein a central axis of said needle is aligned with a center of said ultrasonic receiver.

18. A reference guide for the system of claim 1 , said reference guide comprising:

a configured for placement on a body in apposition to a surgical entry point into the body;

a first ultrasonic transmitter fixed to the housing and a second ultrasonic transmitter fixed to the housing, wherein said first and second ultrasonic transmitters are separated by a lateral gap distance G;

an IR receiver fixed to the housing; and

an IR transmitter fixed to the housing

wherein:

the first and second ultrasonic transmitters, IR Receiver, and IR transmitter face a same direction and away from the body when in use;

the first and second ultrasonic transmitters are configured to transmit ultrasonic signals to the ultrasonic receiver of the piercing apparatus;

the IR receiver is configured to receive IR signals from the IR transmitter of the piercing apparatus; and the IR transmitter is configured to transmit IR signals to the IR receiver of piercing apparatus.

19. A computer implemented method for tracking the position and orientation of a tool with respect to a reference guide, said method comprising:

measuring a distance between a point on the tool and a point on the reference guide; measuring a first angle between the tool and a plane of the reference guide;

measuring a second angle between the tool and a plane of the reference guide;

transmitting data including said distance, said first angle, and said second angle to a computing device; and

computing the position and orientation of the tool with respect to the reference guide from said distance, said first angle, and said second angle.

20. A non-transitory computer-readable storage media comprising software for implementing the method of claim 19.