WO2001047413A1

WO2001047413A1 - Ultrasonic marker for use in surgery

Info

Publication number: WO2001047413A1
Application number: PCT/IL2000/000852
Authority: WO
Inventors: Shmuel Ben-Muvhar
Original assignee: Lifschitz & Co.
Priority date: 1999-12-23
Filing date: 2000-12-22
Publication date: 2001-07-05
Also published as: AU2021801A

Abstract

A surgical designator (20) includes a fixation member (24), adapted to be inserted into hard tissue (27) of a patient at a single point on the tissue. A plurality of emitters (26, 28, 30), including at least first and second emitters, are rigidly attached to the fixation member at predetermined, mutually-spaced locations and are operative to emit energy such that when the energy emitted by the emitters is received by a receiver (25) remote from the designator, the energy received from the first emitter is distinguishable from the energy emitted from the second emitter.

Description

ULTRASONIC MARKER FOR USE IN SURGERY

FIELD OF THE INVENTION

The present invention relates generally to surgical devices and methods, and specifically to devices for determining and guiding the position of a surgical tool in the course of operating on hard tissue

BACKGROUND OF THE INVENTION

Before carrying out surgery involving hard tissues, such as an orthopedic or neurosurgical procedure, X-ray images are generally taken of the area of the operation Frequently, CT or MRI images are also acquired In many cases, such as repairing a compound or complex fracture, the surgeon will also take X-ray images, typically fluoroscopic images, during the surgery For example, when an intermedullary nail must be installed in a fractured bone, the surgeon typically uses intraoperative X-ray images to position the nail and to secure it with interlocking screws Even using X-ray imaging, however, precise positioning of all of the elements can be difficult and time-consuming Consequently, the patient is exposed both to surgical trauma and to large X-ray dosage

Various solutions have been proposed for this problem One class of solutions is based on position sensing systems, with reference points fixed to the hard tissue and to a surgical tool used to operate on the tissue Typically, the reference points comprise emitters of electromagnetic or ultrasonic radiation The position sensing system receives the radiation from the emitters and analyzes it to determine the positions of the reference points Alternatively, the reference points may comprise receivers, such as coils in which a current flows in response to an external magnetic field Before surgery, images of the hard tissue, with the reference points fixed to it, are captured using techniques such as X-ray, CT or MRI During surgery, the position sensing system is used to detect the positions of the reference points on the tissue and the tool, so as to provide continuous updating of the relative positions The positions are automatically registered and displayed on the images captured before the surgery, so that the surgeon can visualize and guide the position of the tool with a reduced need for intraoperative imaging

For example, U S patent 5,383,454, whose disclosure is incorporated herein by reference, describes a position tracking and imaging system for use in neurosurgery Before surgery, ultrasonic emitters are fixed to a number of reference points on the patient's head, and a set of CT images of the head are produced showing the positions of the reference points Similar emitters are fixed to a surgical probe for insertion into the head During surgery, an array of microphones in the operating room receives ultrasound signals emitted by the emitters on the patient's head and on the probe These signals are used to determine the position and orientation of the probe relative to the reference points The position and orientation information is used to display an image of the probe superimposed on the prerecorded CT images

U S Patents 5,265,610 and 5,577,502 and PCT patent application PCT/IL98/00034, whose disclosures are incorporated herein by reference, suggest performing invasive medical procedures during which multiple X-ray images are periodically acquired, in order to give the operator information on the three-dimensional location of an invasive tool In order to minimize the X-ray dosage to the patient, RF transmitters and receivers are used to receive positional information on the invasive tool The positional information from the RF transmitters is used to superimpose the position of the tool on the X-ray images The patient's motion may also be tracked, and the image display adjusted accordingly Thus, it is maintained that the X-ray images may be updated less frequently than in conventional X-ray tracking systems

U S Patent 5,558,091, whose disclosure is incorporated herein by reference, describes a method of aligning sections of a broken bone, by observing a continually-updated image The image is initially acquired using X-rays, but is then updated by computer image processing, based on a position determining system which tracks the movements of sensors attached to the bones

Similarly, PCT Patent Application PCT/LL98/00032, whose disclosure is incorporated herein by reference, describes a system in which position sensors are used in measuring and aligning bone fractures, generally in order to minimize the distance and/or space between pieces of fractured bone that are being fixed Position sensors are fixed to each of the pieces of the fractured bone, using screws, adhesive or any other suitable connection method The position coordinates of the sensors are registered with specific points in a coordinate frame associated with an image of the fracture region When the fracture pieces are moved, the display on the screen is updated according to the position coordinates of the sensors, which are updated continuously by the position determining system. Thus an on-line image of the bone fracture is produced, so that the fracture can be aligned without additional imaging U.S. Patent 5,772,594, whose disclosure is incorporated herein by reference, describes a system that allows an orthopedic surgeon to determine the trajectory of insertion of a guide pin or screw into an object bone and to check the accuracy of the procedure using real-time feedback. Light-emitting diodes (LEDs) are fixed to a reference bar positioned on the object bone, as well as on a surgical drill and on a C-arm fluoroscope used to image the bone. The positions of the LEDs are detected by a camera and are analyzed to present the surgeon with an image showing the relative positions of the drill and the bone.

SUMMARY OF THE INVENTION It is an object of some aspects of the present invention to provide an improved device for marking reference points in hard tissue and on surgical tools, in order to determine the relative positions of the tools and the tissue during surgery.

A single emitter, such as an ultrasonic emitter, fixed to hard tissue or a surgical tool is generally insufficient by itself to enable the position and orientation coordinates of the tissue or the tool to be fully determined. Even when an array of microphones is used to receive ultrasonic signals from the emitter, the data are not sufficient to enable all six coordinates of the tissue (translation and rotation with respect to three axes) to be accurately tracked. For this reason, methods for intraoperative position detection known in the art use multiple emitters, which are generally fastened to a bone or tool at different points along its length or are fixed to the patient's body by a bulky external frame. The need to fasten emitters to a bone at multiple different points adds complication and trauma for the patient, while external frames tend to interfere with the surgery.

It is therefore a further object of some aspects of the present invention to alleviate these problems by providing an improved device for use in intraoperative tracking of tissue and tools, which can be fastened to hard tissue at a single point and still enable accurate determination of all six translation and rotation coordinates of the tissue.

In preferred embodiments of the present invention, an ultrasonic designator comprises a fixation member and multiple, mutually-spaced ultrasonic elements. The fixation member typically comprises a screw or nail, which can be fastened easily to hard tissue at a selected point. The ultrasonic elements, preferably three ultrasonic emitters, are rigidly connected to the fixation member by respective legs, which hold the emitters at fixed, known positions relative to the fixation member. Preferably, the emitters are controlled to emit ultrasonic signals at different, respective times or frequencies, so that the signals are distinguishable one from another (most preferably with gaps between the different times or frequencies to prevent mutual interference) Alternatively or additionally, the signals of the different emitters are distinguished by coding patterns applied to the signals, or by variations in phase and/or amplitude The signals are received by a detection system, using a microphone array, for example, which analyzes the signals to find the position coordinates of each of the emitters These position coordinates can be used to accurately derive all six of the translation and rotation coordinates.

In some preferred embodiments of the present invention, ultrasonic designators of this sort are fixed to different portions of a fractured bone or to multiple adjoining bones, such as vertebrae In further preferred embodiments, a designator is fixed to a surgical tool, as well as to the hard tissue, in order to guide the surgeon in aligning the tool with the tissue Preferably, although not necessarily, position detection of the designators is used in conjunction with pre-operative and/or intraoperative imaging to register the relative positions of the tool and the tissue on such an image The designator can be attached to substantially any tool, regardless of the design or manufacturer of the tool

Although preferred embodiments described herein are based on ultrasonic emitters, it will be appreciated that the principles of the present invention may also be applied using ultrasonic receivers, as well as sonic emitters or receivers in the audible range, as well as emitters and receivers of other types, such as electromagnetic types, particularly in the radio frequency, infrared or optical range.

There is therefore provided, in accordance with a preferred embodiment of the present invention, a surgical designator, including a fixation member, adapted to be inserted into hard tissue of a patient at a single point on the tissue, and a plurality of emitters, including at least first and second emitters, rigidly attached to the fixation member at predetermined, mutually-spaced locations and operative to emit energy such that when the energy emitted by the emitters is received by a receiver remote from the designator, the energy received from the first emitter is distinguishable from the energy emitted from the second emitter Preferably, the fixation member includes a fastener having an insertion end for insertion into the bone of the patient, wherein the fastener typically includes a nail or a screw Further preferably, the fixation member includes a head opposite the insertion end thereof, and the designator includes one or more legs having first and second ends, wherein the first end of each leg is fixed to the head, and one of the emitters is fixed to the second end of each leg

Preferably, the plurality of emitters includes three emitters, most preferably ultrasonic emitters, which are configured to emit energy at different frequencies Alternatively, the emitters are configured to emit energy in different, predetermined time slots or at different phases or amplitudes

In a preferred embodiment, the emitters further comprise at least one infrared emitter

There is also provided, in accordance with a preferred embodiment of the present invention, surgical apparatus, including a tissue designator, which includes a fixation member, adapted to be inserted into hard tissue of a patient at a single point on the tissue, and a plurality of emitters, including at least first and second emitters, rigidly attached to the fixation member at predetermined, mutually- spaced locations and operative to emit energy such that when the energy emitted by the emitters is received by a receiver remote from the designator, the energy received from the first emitter is distinguishable from the energy emitted from the second emitter, and a detection system, adapted to receive the energy emitted by the emitters and to determine, responsive to the received energy, position and orientation coordinates of the tissue designator

Preferably, the detection system is adapted to determine, based on the coordinates of the tissue designator, position and orientation coordinates of the hard tissue

In a preferred embodiment, the apparatus includes a tool designator, adapted to be fastened to a surgical tool and including a further plurality of energy emitters, wherein the detection system is adapted to receive further energy emitted by the emitters of the tool designator and to determine, responsive to the received energy, position and orientation coordinates of the tool designator relative to the tissue designator Preferably, the apparatus is further configured to provide a visual indication of a position and orientation of the surgical tool relative to the tissue, responsive to the coordinates of the tool designator relative to the tissue designator Preferably, the emitters include ultrasonic emitters, and the detection system includes an array of acoustic detectors In a preferred embodiment, the emitters further include at least one infrared emitter, and the detection system further includes at least one infrared detector

There is additionally provided, in accordance with a preferred embodiment of the present invention, a method for performing surgery on hard tissue of a patient, including inserting a fixation member into the hard tissue at a single point on the tissue, the fixation member having a plurality of emitters rigidly attached thereto at predetermined, mutually-spaced locations, actuating the emitters to emit energy such that when the energy emitted by the emitters is received by a receiver remote from the designator, the energy received from a first one of the emitters is distinguishable from the energy emitted from a second one of the emitters, receiving the energy emitted by the emitters, and determining, responsive to the received energy, position and orientation coordinates of the hard tissue Preferably, the method includes: fastening a tool designator to a surgical tool, the tool designator including a plurality of emitters, actuating the emitters of the tool designator, receiving further energy emitted by the emitters of the tool designator; and determining, responsive to the received energy, position and orientation coordinates of the tool relative to the hard tissue

Further preferably, the method includes providing a visual indication of a position and orientation of the surgical tool on an image of the tissue, responsive to the coordinates of the tool designator relative to the tissue designator Preferably, inserting the fixation member includes inserting the fixation member into a bone, wherein the bone most preferably includes a long bone of the arm or leg or a vertebra

There is moreover provided, in accordance with a preferred embodiment of the present invention, a surgical designator, including a fixation member, adapted to be inserted into hard tissue of a patient, one or more ultrasonic emitters, rigidly attached to the fixation member, and one or more infrared emitters, rigidly attached to the fixation member and operative in conjunction with the ultrasonic emitters There is furthermore provided, in accordance with a preferred embodiment of the present invention, surgical apparatus, including a tissue designator, which includes a fixation member, adapted to be inserted into hard tissue of a patient, one or more ultrasonic emitters, rigidly attached to the fixation member and operative to emit ultrasonic energy, and one or more infrared emitters, rigidly attached to the fixation member and operative to emit infrared energy, and a detection system, adapted to receive the ultrasonic and infrared energy emitted by the emitters and to determine, responsive to the received energy, position and orientation coordinates of the tissue designator

Preferably, the detection system is adapted to determine that the ultrasonic energy has been interfered with responsive to the received infrared energy Additionally or alternatively, the detection system is adapted to measure a time of flight of the ultrasonic energy based on the received infrared energy.

There is additionally provided, in accordance with a preferred embodiment of the present invention, a method for performing surgery on hard tissue of a patient, including inserting a fixation member into the hard tissue, the fixation member having one or more ultrasonic emitters and one or more infrared emitters rigidly attached thereto, actuating the emitters to emit ultrasonic and infrared energy; receiving the ultrasonic and infrared energy emitted by the emitters; and determining, responsive to the received ultrasonic and infrared energy, position and orientation coordinates of the hard tissue

Preferably, determining the position and orientation coordinates includes analyzing the received ultrasonic energy to calculate the coordinates, while monitoring the received infrared energy to detect interference with the ultrasonic energy Additionally or alternatively, actuating the emitters includes controlling the emitters to emit pulses of the ultrasonic and infrared energy in mutual synchronization, and determining the position and orientation coordinates includes determining a time of flight of the ultrasonic energy by measuring a difference in times of receiving the ultrasonic and infrared pulses

The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings in which BRIEF DESCRIPTION OF THE DRAWINGS

Fig 1A is a schematic side view of an ultrasonic designator, in accordance with a preferred embodiment of the present invention,

Fig IB is a schematic side view showing a detail of the designator of Fig 1A, in accordance with a preferred embodiment of the present invention,

Fig 2 is a schematic, pictorial illustration of a fracture bone to which ultrasonic designators have been fixed, in accordance with a preferred embodiment of the present invention,

Fig 3 is a schematic, pictorial illustration of a surgical procedure performed using ultrasonic designators, in accordance with a preferred embodiment of the present invention,

Fig 4 is a schematic, pictorial illustration, shown in a cutaway view, of another surgical procedure performed using ultrasonic designators, in accordance with a preferred embodiment of the present invention,

Fig 5 is a schematic, pictorial illustration of vertebrae to which ultrasonic designators have been fixed, in accordance with a preferred embodiment of the present invention, and

Fig 6 is a schematic side view of a designator with both ultrasonic and infrared functions, in accordance with a preferred embodiment of the present invention

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fig 1A is a schematic side view of an ultrasonic designator 20 for use in surgery, in accordance with a preferred embodiment of the present invention The figure is not drawn to scale The designator comprises a fixation member 24, typically a nail (smooth) or a screw (threaded), which is designed to be fastened to hard tissue, such as a bone Typically member 24 is made of stainless steel or titanium, with a length of about 35 mm and a diameter of about 2 mm, although other lengths and diameters may also be used Fig IB is a schematic side view showing a detail of fixation member 24, inserted into a bone 27, in accordance with a preferred embodiment of the present invention A shoulder 25 is optionally provided on member 24 in order to limit the depth of penetration of the member into the tissue

Returning now to Fig 1A, multiple ultrasonic emitters 26, 28, 30 are fixed by respective legs 32, 34, 36 to a head 22 of fixation member 24 The head preferably comprises a material insensitive to ultrasound, such as a hard plastic The legs may be permanently attached to the head, or alternatively, they may be removable In the latter case, the legs and emitters are preferably removed from the head while the fixation member is driven into the bone, in order to make insertion of the fixation member easier and to avoid damage to the emitters The connection between the legs and head is preferably a positive connection, allowing only a certain, fixed mutual orientation This also makes it possible to remove the emitters from the fixation member after the surgery is finished, so that the emitters can be sterilized and reused Alternatively, the entire designator, including the fixation member, may be sterilized and reused or, further alternatively, it may be disposed of after use

Emitters 26, 28 and 30 preferably comprise ultrasonic transducers, such as piezoelectric crystals, which are driven by a controller 38, as is known in the art Preferably, the emitters are less than 10 mm in diameter and emit ultrasonic radiation in the 50 kHz range The controller may be structurally integrated into designator 20, in which case it is preferably battery-powered, or it may be a separate unit, connected to the designator by wires The controller drives the emitters in such a manner that the ultrasonic signal emitted by each of the emitters is distinguishable from those of the other emitters Substantially any system of multiplexing may be used for this purpose, such as frequency-multiplexing, time-multiplexing or code multiplexing In the case of frequency-multiplexing, each of the emitters emits ultrasonic radiation at a different, known frequency Spectral analysis is then applied to the combined signals received from all of the emitters in order to distinguish the individual signals In time-multiplexing, each of the emitters is actuated in a different, predetermined time slot In code multiplexing, a different coded pattern is applied to the signal emitted by each of the emitters

Preferably, legs 32, 34 and 36 are substantially rigid and are fixed to head 22 at known positions and angles As a result, the geometry of designator, and particularly the locations of emitters 26, 28 and 30 relative to one another and to fixation member 24, is precisely known in advance Alternatively, the positions of the emitters may be adjusted, by the surgeon, for example, and then ascertained in a calibration process before continuing with the surgery Although designator 20 is shown to comprise three legs and respective emitters, those skilled in the art will recognize that greater or smaller numbers of legs and emitters may be used, and that the number of legs need not equal to number of emitters In one such embodiment (not shown in the figures), at least one of the emitters is fixed directly to head 22, without an intervening leg The head can even be made wide enough and of appropriate material so that all of the emitters can be fixed to it, so that legs are not required During surgery, a detection system 25, preferably comprising an array of acoustic detectors, such as microphones, detects the respective ultrasonic signals emitted by the different emitters These signals are analyzed to determine position coordinates of each of the emitters, as is known in the art Any suitable detection system and method of analysis may be used, such as those described in the Background of the Invention, for example Preferably, system 25 comprises at least four detectors, sufficiently widely spaced so that even if the surgeon or one of the surgical tools blocks the acoustic signals to one of the detectors, the other detectors continue to function and to give accurate position readings The determined positions of the individual emitters 26, 28 and 30, together with the known geometry of designator 20, are then used to find complete, six-dimensional position and orientation coordinates of the designator and hence of the bone or other hard tissue to which the designator is fixed Preferably, if any of emitters 26, 28 and 30 is found to have coordinates that are incompatible with the structure of designator 20 or with other known geometrical aspects of the procedure, the coordinates of the incompatible emitter are ignored There is no need to attach multiple emitters to different points on the bone Designator 20 thus reduces the trauma to which a patient is subjected and is also suitable for attachment to small bones, such as the bones in the hand or foot

Fig. 2 is a schematic, pictorial view of a broken bone 40, which is repaired using designators 46 and 48, in accordance with a preferred embodiment of the present invention Although bone 40 is shown to be a femur, substantially any fractured bone may be treated in this fashion, particularly the other long bones of the arms and legs. Designators 46 and 48, similar to designator 20 described above, are attached to respective segments 42 and 44 of the broken bone, using surgical methods known in the art Preferably, X-ray or CT images are taken of the bone after attachment of the designators, and the positions of the designators, as determined by the detection system, are registered with the respective positions in the images As the surgeon manipulates the bone segments to bring them into alignment with one another for the purpose of setting the bone, the coordinates of the designators are continually updated by the detection system The updated coordinates are used to guide the surgeon so that segments 42 and 44 are optimally aligned, while minimizing the X-ray exposure of the patient and surgeon

Optionally, in order to facilitate registration and calibration of the designators, fixation member 24 comprises one or more radial protrusions (not shown) Preferably, there are two such protrusions, perpendicular to one another, having the same diameters, typically 1 mm, but different lengths, for example, one protrusion 1 mm and the other 2 mm The known dimensions of the protrusions can be compared to the lengths of the images of the protrusions as they appear in the X-ray or CT images in order to determine an accurate calibration of the scale of the images The calibration may be performed either manually or automatically

Alternatively, for some procedures, it is desirable to capture magnetic resonance images (MRI) before the procedure and to register the positions of designators 46 and 48 with these images For such procedures, in order that the designators show up clearly under MRI, a portion of the designator is preferably made to afford high MRI contrast For example, the designator may comprise one or more spherical plastic balls (not shown in the figures), which are filled with water Optionally, the plastic balls are removable and may be replaced by a metal ball for CT imaging, or by ultrasonic emitters 26, 28 and 30

Fig 3 is a schematic, pictorial illustration showing another surgical procedure, in which a tool 50 is used to drill a channel in bone 40, in accordance with a preferred embodiment of the present invention A bone designator 52 is fixed to bone 40, and a tool designator 54 is fixed to tool 50 Both of the designators are substantially similar to designator 20 Preferably, suitable adjustments are made in the lengths and positions of legs 32, 34, 36 of the designators in order to distance the respective emitters sufficiently from the bone and from the tool itself so as to avoid interference with the ultrasonic emissions Designator 52 is preferably fixed to the bone at a defined landmark chosen by the surgeon, such as the great trochanter

Preferably, after designators 52 and 54 have been fixed in place, but before beginning the surgery, an X-ray or CT image is taken The image is analyzed, as is known in the art, in order to register the positions of the respective designators with bone 40 and, preferably, with tool 50 Alternatively, the position of designator 54 relative to tool 50 is input based on a given mechanical drawing or known dimensions of the tool Once the surgery begins, the position detection system continually updates the coordinates of designators 52 and 54 Preferably, the updated coordinates are used to superimpose a schematic image of tool 50 on the image of bone 40, showing the current position of the tool relative to the bone Most preferably, the image also shows a trajectory 56 of the tool into the bone, based on the current position and orientation coordinates. The surgeon watches this trajectory in aiming the tool Alternatively, when designator 52 is fixed to a known landmark on the bone in a well-defined location and orientation, it may be possible to orient and aim tool 50 using the relative coordinates of designators 52 and 54, without the expense and complication involved in continually processing and updating X-ray or CT images In this case, the use of designator 52 is valuable at least in ensuring that the position and orientation of bone 40 do not change during the surgery.

In another preferred embodiment (not shown in the figures), fixation member 24 comprises a fixture, such as an intramedullary nail or cannulated screw, which is inserted permanently or semi-permanently into the bone In this case, emitters 26, 28 and 30 are used to determine the position and orientation of the fixture inside the bone This information is useful both in finding the proper angle for insertion of the fixture and in afterwards locating parts of the fixture that cannot be seen, inside the bone The location of the fixture determined in this way can be used, for example, to guide the surgeon in inserting interlocking screws through the bone, in order to hold the fixture in place Figs. 4 and 5 are schematic, pictorial illustrations showing another surgical procedure in which tool 50 is used to operate on a vertebra 60, in accordance with a preferred embodiment of the present invention. Fig 4 is a cutaway view of the vertebra, seen along the axis of the spine, while Fig. 5 is a side view of vertebra 60 and other, adjoining vertebrae, including a vertebra 70. Designators 62 and 72, similar to designator 20, are respectively fixed to spinous processes 64 of vertebrae 60 and 70. The designators allow the positions and orientations of the vertebrae to be determined and tracked, even when the spine moves or flexes. This information is useful, for example, in surgery on the intervertebral disks In Fig 4, designator 54 is used to guide tool 50 in drilling adjacent to a transverse process 66 of vertebra 60. Alternatively, the approach to the vertebrae may be made through the abdominal cavity, preferably using a much longer designator.

Although certain types of surgical procedures are described hereinabove, those skilled in the art will appreciate the usefulness of designators in accordance with the present invention in other types of procedures, performed on substantially any type of hard tissue in the body Furthermore, although the preferred embodiments described herein are based on ultrasonic emitters, it will be appreciated that the principles of the present invention may also be applied using acoustic emitters in other frequency ranges, such as sonic emitters in the audible range Designator 20 may also be adapted to work with emitters of other types, such as emitters of electric or magnetic fields, particularly in the radio frequency range, or electromagnetic emitters at higher frequencies, such as in the infrared or optical range

In an alternative embodiment, for example (not shown in the figures), the designators fixed to the tissue comprise microphones, which receive signals from an array of emitters positioned away from the body In this case, the designators must communicate with a control unit, typically by a wired or infrared link, for example The control unit preferably determines the coordinates of the designators by measuring the times of flights of the acoustic signals form the emitters to each of the microphones Alternatively, the designators fixed to the tissue comprise ultrasonic reflectors, and both the emitters and the receivers (microphones) are positioned away from the body In this case, the reflectors are preferably asymmetrical in order to enable their respective reflections to be distinguished one from another

In still another embodiment (not shown), one or more designators are fixed to a mold that fits over a patient's teeth This embodiment is useful particularly for neurosurgery and maxillo-facial procedures The mold is preferably custom-made in advance for the patient, so as to give a tight fit over the upper teeth The mold can then be removed when it is not needed and repositioned over the teeth with high precision during surgery

Fig 6 is a schematic side view of a designator 120, in accordance with another preferred embodiment of the present invention This designator is substantially similar to designator 20, shown in Fig 1A, except that alongside ultrasonic emitters 26, 28 and 30, designator 120 comprises infrared emitters 126, 128 and 130, typically LEDs Detection system 125 in this case comprises both acoustic receivers 136 and infrared receivers 138 The infrared emitters are useful in improving the accuracy and reliability of the ultrasonic position measurement results in at least two ways

• If an object blocks or interferes with the acoustic signals from one or more of the ultrasonic emitters, the corresponding infrared signal will also be blocked Based on the absence of the infrared signal, system 125 preferably ignores the corresponding acoustic signal

• The infrared emitters are preferably pulsed at the same time as the corresponding ultrasonic emitters Reception of the infrared signal by detection system 125 then serves as a trigger for a more accurate measurement of the time of flight of the corresponding acoustic signal It will thus be appreciated that the preferred embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.

Claims

I A surgical designator, comprising a fixation member, adapted to be inserted into hard tissue of a patient at a single point on the tissue, and a plurality of emitters, including at least first and second emitters, rigidly attached to the fixation member at predetermined, mutually-spaced locations and operative to emit energy such that when the energy emitted by the emitters is received by a receiver remote from the designator, the energy received from the first emitter is distinguishable from the energy emitted from the second emitter.

2 A designator according to claim 1, wherein the fixation member comprises a fastener having an insertion end for insertion into the bone of the patient

3 A designator according to claim 2, wherein the fastener comprises a nail

4 A designator according to claim 2, wherein the fastener comprises a screw.

5 A designator according to claim 2, wherein the fixation member comprises a head opposite the insertion end thereof, and wherein the designator comprises one or more legs having first and second ends, wherein the first end of each leg is fixed to the head, and one of the emitters is fixed to the second end of each leg

6. A designator according to claim 1, wherein the plurality of emitters comprises three emitters

7 A designator according to claim 1, wherein the emitters comprise ultrasonic emitters.

8 A designator according to claim 7, wherein the emitters further comprise at least one infrared emitter

9 A designator according to any of claims 1-8, wherein the emitters are configured to emit the energy at different frequencies

10 A designator according to any of claims 1-8, wherein the emitters are configured to emit the energy in different, predetermined time slots

I I A designator according to any of claims 1-8, wherein the emitters are configured to emit the energy as waves having different phases

12 A designator according to any of claims 1-8, wherein the emitters are configured to emit the energy with different coding patterns applied thereto

13 Surgical apparatus, comprising: a tissue designator, which comprises a fixation member, adapted to be inserted into hard tissue of a patient at a single point on the tissue; and a plurality of emitters, including at least first and second emitters, rigidly attached to the fixation member at predetermined, mutually-spaced locations and operative to emit energy such that when the energy emitted by the emitters is received by a receiver remote from the designator, the energy received from the first emitter is distinguishable from the energy emitted from the second emitter, and a detection system, adapted to receive the energy emitted by the emitters and to determine, responsive to the received energy, position and orientation coordinates of the tissue designator.

14. Apparatus according to claim 13, wherein the detection system is adapted to determine, based on the coordinates of the tissue designator, position and orientation coordinates of the hard tissue.

15 Apparatus according to claim 13, and comprising a tool designator, adapted to be fastened to a surgical tool and comprising a further plurality of energy emitters, wherein the detection system is adapted to receive further energy emitted by the emitters of the tool designator and to determine, responsive to the received energy, position and orientation coordinates of the tool designator relative to the tissue designator

16 Apparatus according to claim 15, which is further configured to provide a visual indication of a position and orientation of the surgical tool relative to the tissue, responsive to the coordinates of the tool designator relative to the tissue designator

17. Apparatus according to any of claims 13-16, wherein the emitters comprise ultrasonic emitters, and wherein the detection system comprises an array of acoustic detectors

18. Apparatus according to claim 17, wherein the emitters further comprise at least one infrared emitter, and wherein the detection system further comprises at least one infrared detector 19 A method for performing surgery on hard tissue of a patient, comprising inserting a fixation member into the hard tissue at a single point on the tissue, the fixation member having a plurality of emitters rigidly attached thereto at predetermined, mutually-spaced locations, actuating the emitters to emit energy such that when the energy emitted by the emitters is received by a receiver remote from the designator, the energy received from a first one of the emitters is distinguishable from the energy emitted from a second one of the emitters, receiving the energy emitted by the emitters, and determining, responsive to the received energy, position and orientation coordinates of the hard tissue

20 A method according to claim 19, and comprising fastening a tool designator to a surgical tool, the tool designator comprising a plurality of emitters, actuating the emitters of the tool designator, receiving further energy emitted by the emitters of the tool designator, and determining, responsive to the received energy, position and orientation coordinates of the tool relative to the hard tissue

21 A method according to claim 20, and comprising providing a visual indication of a position and orientation of the surgical tool on an image of the tissue, responsive to the coordinates of the tool designator relative to the tissue designator

22 A method according to claim 19, wherein actuating the emitters comprises driving the emitters to emit ultrasonic energy

23 A method according to claim 22, wherein actuating the emitters further comprises driving the emitters to emit infrared energy 24 A method according to claim 23, wherein determining the position and orientation coordinates comprises analyzing the received ultrasonic energy responsive to the received infrared energy

25 A method according to any of claims 19-24, wherein inserting the fixation member comprises inserting the fixation member into a bone 26 A method according to claim 25, wherein the bone comprises a long bone of the arm or leg

27 A method according to claim 25, wherein the bone comprises a vertebra

28 A surgical designator, comprising a fixation member, adapted to be inserted into hard tissue of a patient, one or more ultrasonic emitters, rigidly attached to the fixation member, and one or more infrared emitters, rigidly attached to the fixation member and operative in conjunction with the ultrasonic emitters

29 Surgical apparatus, comprising a tissue designator, which comprises a fixation member, adapted to be inserted into hard tissue of a patient, one or more ultrasonic emitters, rigidly attached to the fixation member and operative to emit ultrasonic energy, and one or more infrared emitters, rigidly attached to the fixation member and operative to emit infrared energy, and a detection system, adapted to receive the ultrasonic and infrared energy emitted by the emitters and to determine, responsive to the received energy, position and orientation coordinates of the tissue designator

30 Apparatus according to claim 29, wherein the detection system is adapted to determine that the ultrasonic energy has been interfered with responsive to the received infrared energy

31 Apparatus according to claim 29 or 30, wherein the detection system is adapted to measure a time of flight of the ultrasonic energy based on the received infrared energy

32 A method for performing surgery on hard tissue of a patient, comprising inserting a fixation member into the hard tissue, the fixation member having one or more ultrasonic emitters and one or more infrared emitters rigidly attached thereto, actuating the emitters to emit ultrasonic and infrared energy, receiving the ultrasonic and infrared energy emitted by the emitters, and determining, responsive to the received ultrasonic and infrared energy, position and orientation coordinates of the hard tissue 33 A method according to claim 32, wherein determining the position and orientation coordinates comprises analyzing the received ultrasonic energy to calculate the coordinates, while monitoring the received infrared energy to detect interference with the ultrasonic energy

34 A method according to claim 32 or 33, wherein actuating the emitters comprises controlling the emitters to emit pulses of the ultrasonic and infrared energy in mutual synchronization, and wherein determining the position and orientation coordinates comprises determining a time of flight of the ultrasonic energy by measuring a difference in times of receiving the ultrasonic and infrared pulses