Abstract:
Medial device comprising a housing, a magnetic detection probe, for detecting a plurality of magnetic fields, a biometric unit and a controller, connected to said magnetic detection probe, said biometric unit and said storage unit, wherein said controller receives magnetic field detection information from said magnetic detection probe, and wherein said controller operates said biometric unit in association with said magnetic field detection information.

Description:
FIELD OF THE INVENTION 
     The present invention relates to positioning systems in general, and to methods and systems for positioning an item within a living tissue, in particular. 
     BACKGROUND OF THE INVENTION 
     Minimal Invasive Endoscopic Surgery (MIES) provides the means by which less invasive medical procedures can be employed cost-effectively for a huge segment of the patient population, covering the most important medical specialties and surgical interventions. While patients benefit from this innovative technique, much of the credit for its success must be given to physicians/endoscopists and to manufacturers who created the endoscopic video imaging systems and unique procedure-specific devices, which together made millions of procedures possible each year since the technique gained prominence in the late 1980&#39;s. 
     MIES reduces the cost of the overall procedure by reducing the number of days that a patient spends in a medical facility and by significantly reducing the trauma which is inflicted on the patient, which reduces the chance for complication during a procedure and afterwards. 
     Systems for determining the location of a medical device within a treated living tissue are known in the art. In general, these systems are divided into two major groups, which are visual systems, semi visual systems and non-visual positioning system. 
     A conventional visual system includes an optical imaging element such as a fiber optic based device. The imaging element is inserted into the body of the patient and assists the physician in locating any surgical tool therein. One such system is called an endoscope. A conventional endoscope includes a dilating catheter in which lighting means, visual image unit and a surgical tool, are inserted. 
     Semi-visual systems often include a real time imaging device such as an ultrasound mechanism, which is combined with the tip of the endoscope. An example for such a system is the EUB-525 ultrasound system with the 10R probe, manufactured and sold by Hitachi. 
     Non visual systems include additional means, which assist the user in determining the location of the medical device within the body of the patient. U.S. Pat. No. 5,729,129 to Acker is directed to a magnetic location system with feedback adjustment of magnetic field generator. It is noted that this system is subjected to metal object interference, which is produced by various metal objects, located in the vicinity of the system. Another disadvantage of this system is that the general method of operation of such a system includes three consecutive steps: transmitting an electromagnetic signal; detecting this signal and adjusting the electromagnetic signal according to the detected one. Hence the refresh rate of this system is significantly slow. 
     U.S. Pat. No. 5,840,025 to Ben-Haim, is directed to an Apparatus And Method for Treating Cardiac Arrhythmias. According to Ben-Haim, a catheter is inserted into the body of the patient and located in selected locations within the heart. The tip of the catheter includes a transmitting antenna, which transmits an electromagnetic signal. This signal is detected by external antennas and is then used to determine the location of the tip of the catheter. Finally, this information is super imposed on a pre-acquired image of the treated area. 
     U.S. Pat. No. 5,752,513 to Acker et al is directed to a Method And Apparatus for Determining the Position of an Object. The system uses an electromagnetic transmitter and receiver arrangement to determine the location and orientation of a medical device, which is inserted in the body of a patient. The location and orientation information is incorporated with a pre-acquired image of the treated area, using a plurality of markers, which have both visual as well as magnetic characteristics. It is noted that the accuracy of this apparatus significantly decreases in the presence of metal objects, which deform the magnetic fields. 
     A Bronchoscope is a specific type of an endoscope, which is directed for treating lungs. During a conventional lung treatment, the physician inserts the bronchoscope into the lung of the patient and operates the surgical tool (which can be a clamp, a brush, a laser device and the like) while viewing the inside volume of the lung, using the visual image unit. 
     It will be appreciated by those skilled in the art that the width of the bronchoscope is significant. Hence, a bronchoscope can not be used to treat places, where the access thereto is narrower than the diameter of the bronchoscope. In the case of lung treatment, the conventional method is to place the patient on an X-ray table system and place an X-ray video camera on top, which provides continuous images of the treated area and the surgical tool inserted therein. It will be appreciated by those skilled in the art that this method suffers several disadvantages. The imaging resolution is often not high enough and provides only vague indication of the location of the surgical too. Operating an X-ray table requires a medical staff of several people. X-ray based technology is known in the art as inflicting considerable hazards on the medical staff operating it. 
     Gastroscopy is also known in the art. One type of gastroscopes includes an ultrasound transceiver at the tip end, providing continuous semi-visual information, enabling the physician to operate a surgical tool using this information. It will be appreciated by those skilled in the art that operating an ultrasound-visualizing device requires a considerable training period, which conventionally is in the order of 18-24 months. Such a combined ultrasound gastroscopy system is the FG-34UX model, manufactured and soled by Pentax. 
     Another type of positioning system includes the UltraGuide 1000, which is a combined ultrasound and magnetic location system. This system includes an external ultrasound transducer and a magnetic field based location detection system, which is mounted on a firm surgical tool, such as a large needle. This ultrasound device enables the user to select an insertion point and angle that permit access, with a long needle, to a target within the body of the patient. 
     SUMMARY OF THE PRESENT INVENTION 
     It is an object of the present invention to provide a novel method and system for determining the location and orientation of objects, within a scanning volume, which overcomes the disadvantages of the prior art. It is another object of the present invention to provide a novel method and system for initiating and calibrating the location and orientation of a detector of the system, within the scanned volume. 
     It is a further object of the present invention to provide a novel method and system for obtaining an inner body three-dimensional image from a plurality of two dimensional images. 
     It is yet another object of the present invention to provide a novel method and system to operate within the body of the patient, wirelessly. 
     In accordance with the present invention, there is thus provided an apparatus for determining the position and orientation of a surgical tool relative to a reference frame, in association with an image. The apparatus includes a magnetic field transmitter, a detection probe, a signal generation module, connected to the magnetic field transmitter, a detection processor, connected to the detection probe and mounting means, for mounting onto the surgical tool. 
     The magnetic field transmitter, includes at least one magnetic field generating element. The detection probe includes at least one magnetic field detector 
     The combined number of the magnetic fields generators and the magnetic field detectors is at least four. The signal generation module determines a transmit signal and provides the transmit signal to the magnetic field transmitter. The detection processor receives a detected signal from the detection probe, determines the location and orientation of the detection probe from the detected signal and indicates the location of the surgical tool within the image. The detection probe can include any number of magnetic field detectors. 
     The signal generation module can include a digital to analog converter and a signal processor connected thereto. The signal processor determines a digital transmit signal. The digital to analog converter converts the digital signal to a respective analog signal and provides the analog signal to the magnetic field transmitter. The digital signal can include any number of transmission channels. Each of the channels can include any number of frequencies. 
     In accordance with one aspect of the invention, each of the channels includes a plurality of frequencies. 
     In accordance with another aspect of the invention, the apparatus can further include an ultra-sound interface, for connecting to an ultrasound system capturing ultrasound frames. The detection processor constructs the image from the ultrasound frames, with respect to the detected location and orientation of the surgical tool 
     It is noted that the detection probe can be wirelessly connected to the detection processor. The frequencies and for that matter the channels themselves, can either be transmitted in accordance with a predetermined non overlapping sequence or simultaneously 
     In accordance with another aspect of the invention, there is provided a medial device which includes a housing, a magnetic detection probe, a biometric unit and a controller, connected to the magnetic detection probe, to the biometric unit and to the storage unit. The controller receives magnetic field detection information from the magnetic detection probe. The controller operates the biometric unit in association with the magnetic field detection information. It is noted that the housing can be shaped like a capsule. 
     The medial device can further include a transmitter, which is connected to the controller, for transmitting the magnetic field detection information. The biometric unit includes at least one of the devices in the list consisting of an image detection unit, a substance releasing unit and a biometric sampling unit. The medial device can further include a storage unit for storing the magnetic field detection information, connected to the controller. 
     The biometric unit can include a biomedical sensor, wherein the biometric unit provides detected biometric information to the controller and wherein the controller produces a plurality of records. Each of the records can thus include a portion of the biometric information and a respective portion of the detected magnetic field information. The controller can store the records in the storage unit. 
     The medial device can further include a wireless transmitter, connected to the controller, wherein the controller provides the records to the wireless transmitter and wherein the transmitter transmits the records to an external receiver. It is noted that the magnetic fields, which are detected by the medical device are generated by an external transmitter. These electromagnetic fields can be generated in accordance with either a predetermined non overlapping sequence, semi overlapping sequence or simultaneously and continuously. 
     In accordance with another aspect of the invention, there is provided a method for calibrating a reference image onto a volume, from which the image is produced. The method includes the steps of determining a plurality of locations in the volume, the locations being visible, and present in the reference image, detecting a magnetic field reading in each of the locations, and calibrating the reference image with respect to the magnetic field readings, onto the volume. This method eliminates the need to place special markers, which can be located either in the image or by a detector. 
     The method can further include the steps of receiving additional magnetic field readings, each in an additional location within the volume, and determining the location and orientation of the additional location, within the reference frame. 
     In accordance with yet a further aspect of the invention, there is thus provided an Imaging system which includes an inner body ultrasound detector, and a location and orientation detector, firmly attached to the inner body ultrasound detector. The inner body ultrasound detector detects a plurality of two-dimensional images and the location and orientation detector detects the location and orientation of each of the two-dimensional images. The system can further include a three dimensional image generator, connected to the inner body ultrasound detector and to the location and orientation detector. The three dimensional image generator processes the two-dimensional images, each with its respecting location and orientation information, thereby producing a three dimensional image. 
     The imaging system can include a storage unit, connected between the three dimensional image generator the inner body ultrasound detector and the location and orientation detector, for intermediately storing the two-dimensional images, each with its respecting location and orientation information. 
     The imaging system can further include a combining processor, connected to the three dimensional generator and interfacing at least one additional location and orientation detector. The combining processor receives additional location and orientation information from the additional location and orientation detectors. The combining processor produces an indication of the additional location and orientation information onto the three-dimensional image. The inner body ultrasound detector can include either an angular ultrasound transceiver or a radial ultrasound transceiver. 
     The location and orientation detector can include at least one axial magnetic detector. Each of the location and orientation detectors can detect magnetic field in at least one axial magnetic direction. The location and orientation detector can detect magnetic field in at least one frequency in each of the axial magnetic directions. The location and orientation detector is generally mounted on the inner body ultrasound detector. 
     The inner body ultrasound detector can be mounted on a catheter. In this case the location and orientation detector can be mounted on the tip of the catheter, in the vicinity of the inner body ultrasound detector. 
     In accordance with yet another aspect of the invention, there is provided a method for producing a three dimensional image, which includes the step of detecting a plurality of two-dimensional ultrasound images, from the inner section of a scanned volume. The method can further include the steps of detecting the location and orientation of a selected vector in each of the two dimensional ultrasound images, and determining a three dimensional representation for each of the two-dimensional images, according to the location and orientation thereof. 
     The method can further include the step of producing a three-dimensional image from the three-dimensional representations. 
     The method can further include the step of receiving additional location and orientation information and producing an indication thereof onto the three-dimensional image. 
     The method can further include the step of producing a visible representation of the three-dimensional image and the indication. 
     The method can further include the step of inserting an ultrasound detector into the inner section of the scanned volume. According to one aspect of the invention, the two-dimensional ultrasound images can include angular two-dimensional ultrasound images. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: 
     FIG. 1A is a schematic illustration of a location and orientation determination system, constructed and operative in accordance with a preferred embodiment of the present invention; 
     FIG. 1B is an illustration in detail of the sensor of the system of FIG. 1A; 
     FIG. 1C is an illustration of a sensor, constructed and operative in accordance with a further preferred embodiment of the present invention; 
     FIG. 2A is an illustration of a patient and an invasive system, constructed and operative in accordance with another preferred embodiment of the invention; 
     FIG. 2B is an illustration of a 3D image, a positioning representation and the super imposing of both of them; 
     FIGS. 3A,  3 B and  3 C are illustrations of the location and orientation determination system of FIG. 1A, incorporated within a bronchoscope, constructed and operative in accordance with a further preferred embodiment of the present invention; 
     FIG. 4A is an illustration of a patient, a catheter and a location and orientation detection system, constructed and operative in accordance with another preferred embodiment of the present invention; 
     FIG. 4B is an illustration of the superimposing of the location information provided by the location and orientation detection system of FIG. 4A and a three dimensional image of a treated portion of the body of the patient; 
     FIG. 4C is an illustration in detail of the tip end of the catheter of FIG. 4A; 
     FIG. 5 is a schematic illustration of an inspection system, constructed and operative in accordance with a further preferred embodiment of the present invention 
     FIG. 6 is a schematic illustration in detail of the electromagnetic generator section of a positioning system, constructed and operative in accordance with another preferred embodiment of the present invention; 
     FIG. 7 is a schematic illustration of a method for generating a complicated magnetic field waveform, operative in accordance with a further preferred embodiment of the present invention; 
     FIG. 8 is a schematic illustration of a method for operating a system, operative in accordance with another preferred embodiment of the present invention; 
     FIG. 9 is a schematic illustration of a three dimensional imaging system, which combines an inner ultrasound transceiver and a location and orientation detector, constructed and operative in accordance with a further preferred embodiment of the present invention; 
     FIGS. 10A and 10B are illustrations in perspective of an inner body ultrasound assembly of FIG. 9, constructed and operative in accordance with another preferred embodiment of the present invention; 
     FIG. 10C is an illustration in perspective of a plurality of angular ultrasound slice images; 
     FIGS. 11A and 11B are illustration in perspective of an inner body ultrasound assembly, constructed and operative in accordance with a further preferred embodiment of the invention; 
     FIG. 12 is a schematic illustration of a method for operating a system, operative in accordance with another preferred embodiment of the invention; 
     FIG. 13 is a schematic illustration of a method for initially positioning a location and orientation detector onto a reference image, operative in accordance with a further preferred embodiment of the present invention; and 
     FIG. 14 is an illustration of two minimal invasive tools, constructed and operative in accordance with another preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention overcomes the disadvantages of the prior art by providing a novel method and a novel system which provide accurate and harmless positioning of a medical device within a living tissue. 
     Reference is now made to FIG. 1A, which is a schematic illustration of a system, generally referenced  100 , constructed and operative in accordance with a preferred embodiment of the present invention. 
     System  100  includes a position &amp; orientation processor  102 , a super imposing processor  104 , a sensor interface  106 , a main sensor  110 , an auxiliary sensor  112 , a 3D electromagnetic field generator  108 , an image interface  116 , a 3D image database  120  and a display unit  114 . It is noted that system  100  can include additional 3D electromagnetic field generators. 
     The position &amp; orientation processor  102  is connected to the 3D electromagnetic field generator  108 , to the super imposing processor  104  and to the sensor interface  106 . The image interface is connected to the 3D-image database  120  and to the super imposing processor  104 . The super imposing processor  104  is further connected to the display unit  114 . The sensor interface is further connected to the main sensor  110  and to the auxiliary sensor  112 . 
     The 3D electromagnetic field generator  108  includes a plurality of electromagnetic generating elements such as coils, which produce a plurality of electromagnetic fields in a plurality of directions and in a plurality of magnitudes. It is noted that these fields can either be fixed or alternating. These fields are detected by each of the sensors  110  and  112 . The electromagnetic field detection results, provide an indication of the location and orientation of the main sensor  110 . 
     The main sensor  110  of system  110  is generally located on a probe or a medical tool, which is inserted within the inspected tissue. Auxiliary sensor  112  is generally located in the vicinity of the inspected tissue. It is noted that the use of such an auxiliary sensor enhances the performance of system  100  but is not essential. It is noted that more auxiliary sensors can be added to the system. For example, an auxiliary sensor can be attached to the body of the patient, providing reference to his movement. 
     The sensors  110  and  112  provide information related to detected electromagnetic fields, to the position and orientation processor  102 . From this information and with respect to the fields generated by the 3D electromagnetic field generator  108 , the position and orientation processor  102  determines the location and orientation of the sensor  110  and of auxiliary sensor  112 . The position and orientation processor  102  produces respective location and orientation data, and provides it to the super imposing processor  104 . It is noted that a system according to the present invention, can include a plurality of electromagnetic generators, such as the 3D electromagnetic field generator  108 . 
     The 3D-image database  120  includes a pre-detected image of the inspected tissue and provides it to the super imposing processor  104 . It is noted that the pre-detected image can be provided from any 3D image generating device, such as an X-ray detection system, a magnetic resonance imaging (MRI) system, an ultrasound imaging system and the like. 
     The 3D-image database  120  provides 3D image data to the super imposing processor  104 , via the image interface  116 . The super imposing processor  104  processes the location and orientation data, received from the location and orientation processor  102 , with the 3D image data, received from the 3D image database. The super imposing processor  104  thereby produces an image, which includes a representation of the pre-detected 3D image, and an indication of the position and orientation of the sensor  110 , thereon. The super imposing processor  104  provides this representation to the display unit  114 , which in turn produces a respective image. 
     Reference is further made to FIGS. 1B and 1C. FIG. 1B is an illustration of sensor  110  of system  100  of FIG.  1 A. FIG. 1C is an illustration of a sensor, generally referenced  170 , constructed and operative in accordance with a further preferred embodiment of the present invention. 
     Sensor  110  includes a core  150  and three coils  152 ,  154  and  156 . It is noted that core  150  can be ferromagnetic. Each of the coils detects an electromagnetic field in a different direction. Hence, sensor  110  provides information with respect to three dimensions (x,y,z). It is noted that the core  150  can be replaced by other known means for amplifying the detected signal, such as using higher gain coils and the like. It is noted that any type of electromagnetic field sensors, such as Hall effect sensors, and the like, which is known in the art, is applicable for the present invention. Furthermore it is noted that the sensor can be used without a ferromagnetic core. 
     With reference to FIG. 1C, sensor  170  includes a core  172  and two coils  174  and  176 . It is noted that core  172  can be ferromagnetic. Each of these coils  174  and  176  detects electromagnetic field in a different direction. Hence, sensor  170  provides information with respect to two dimensions, for example (x,y). 
     A location and orientation detection system for helmets, which operates according to the same principle is disclosed in U.S. Pat. Nos. 5,646,524 and 5,646,525, which are hereby incorporated by reference. The present invention utilizes such a system to determine the location and the orientation of invasive medical devices within a living tissue. 
     In accordance with a further aspect of the invention, each of the magnetic fields is generated using a plurality of frequencies. This novel aspect of the invention overcomes several disadvantages of the prior art, such as increasing the metal effect and the like. By taking into account the field measurements of a plurality of detected electromagnetic fields, the system of the invention, eliminates the disturbing effects of metal objects which may disrupt these electromagnetic fields. 
     Reference is now made to FIG. 6, which is a schematic illustration in detail of the electromagnetic generator  108  section of a system  100 , constructed and operative in accordance with further preferred embodiment of the present invention. 
     Electromagnetic generator  108  includes a digital signal processor (DSP)  132 , a plurality of channel modules, generally referenced  131 , an analog to digital converter  138 , three amplifiers  140 A,  140 B and  140 N, three coils  142 A,  142 B and  142 N, three capacitors  144 A,  144 B and  144 N and a plurality of precise resistors  148 A,  148 B and  148 N. Coils  142 A,  142 B and  142 N have values L 1 , L 2  and L 3 , respectively. Capacitors  144 A,  144 B and  144 N have capacitance values of C 1 , C 2  and C 3 , respectively. Resistors  148 A,  148 B and  148 N have resistance values of R 1 , R 2  and R 3  respectively. It is noted that the system  108  uses capacitors  144 A,  144 B and  144 N so as to be operated in resonance modes. It is noted that system  108  can be operated in non-resonance modes, for addressing a wide band of transmission frequencies, when the capacitors  144 A,  144 B and  144 N are removed and the coils are directly connected to the resistors. 
     Each of the cannel modules  131  includes a look-up table module, generally referenced  130 , a digital to analog module, generally referenced  136  and an automatic gain control (AGC) module, generally referenced  134 . It is noted that each of the channel modules controls a magnetic generation unit, and hence a magnetic field generation channel. 
     DSP  132  and the DAC  136  are each connected to the look-up table module  130  and to the AGC module  134 . The AGC module is further connected to the positive input ports of amplifiers  140 A,  140 B and  140 N. Each of the coils  142 A,  142 B and  142 N is connected between an output of a respective one of the amplifiers  140 A  140 B and  140 N and a respective one of the capacitors  144 A,  144 B and  144 N. Each of the precise resistors  148 A,  148 B and  148 N is connected between the capacitors  144 A,  144 B and  144 N and the negative input of a respective amplifier  140 A,  140 B and  140 N. Coils  142 A,  142 B and  142 N are positioned in different directions, to each other. It is noted that the DSP  132  receives feedback from the coils  142 A  142 B and  142 C, using the precise resistors  148 A,  148 B and  148 N. The ADC converter  138  is connected to a plurality of voltage measurement units  150 A,  150 B and  150 N, each measuring the voltage across a selected one of the resistors  148 A,  148 B and  148 N. The ADC  138  is further connected to the DSP  132 . 
     Each of the power amplifiers  140 A,  140 B and  140 N drives a respective current I 1 , I 2  and I 3  through a respective coil  142 A,  142 B and  142 C, thereby generating three respective magnetic fields B 1 , B 2  and B 3 . Sensor  110  (FIG. 1B) simultaneously detects a magnetic signal which includes these three magnetic fields B 1 , B 2  and B 3 , which are translated to voltage in each of the coils  152 ,  154  and  156  of sensor  110 . It is noted that the system  100  can include additional magnetic field generators and hence can generate additional magnetic fields. The produced voltage signals are: 
     
       
           V   x ( t ) =X   1 ×sin(ω 1   t ) +X   2 ×sin(ω 2   t ) + . . . +X   N ×sin(ω N   t ) 
       
     
     
       
           V   y ( t ) =Y   1 ×sin(ω 1   t ) +Y   2 ×sin(ω 2   t ) + . . . +Y   N ×sin(ω N   t ) 
       
     
     
       
           V   z ( t ) =Z   1 ×sin(ω 1   t ) +Z   2 ×sin(ω 2   t ) + . . . +Z   N ×sin(ω N   t ) 
       
     
     The detector voltage amplitude matrix (for a 3×3 example) is:        Amp   =     [           X   1           X   2           X   N               Y   1           Y   2           Y   N               Z   1           Z   2           Z   N           ]                            
     the present example, provides an explanation which addresses a three channel case. It is noted that the invention is not limited to the number of channels, and can be easily expanded as desired. Additional channels increase the level of accuracy of the detection of the location of the sensor. A plurality of measurements, produced from a plurality of transmitters, each at a different location, provide a lot of information, which can be used to eliminate distortions, interference and the like. 
     According to the present invention, this matrix is measured continuously at the detector end. At the same time, the currents I 1 , I 2  and I 3 , are measured at the transmitting end. Hence, since both the transmission and the reception processes are executed at the same time, then the system  100  can determine the location of the detector with respect to the transmitter at a fast refresh rate, which is in the order of 10 ms or less. 
     In accordance with a further aspect of the invention, the currents I 1 , I 2 and I N  are measured using precise value resistors, which are connected in with each of the coils  142 A,  142 B and  142 N. Measuring the voltage across these resistors yields a precise determination of the currents therein. The measurements of the voltage values is provided in digital form from the ADC  138  to the DSP  132 . 
     In accordance with another aspect of the invention, a special hardware structure is used to improve the speed and quality of the sinusoidal waveform of the generated magnetic fields. The DSP  132  determines the signal, which is to be transmitted by each of the coils  142 A,  142 B and  142 N. Each of these signals includes a combination of a plurality of simple waveforms, such as sinusoids and the like. The DSP  132  can further determine a sequence in which each of the waveforms is to be transmitted. It is noted that according to the present invention, the signals can be transmitted simultaneously. 
     The DSP  132  stores the waveforms in the look-up table  130 . The look-up table  130  eliminates the need for the DSP  132  to compute waveforms during operation of the system. The waveforms are stored in a continuous wave format, where they can be retrieved directly from the look-up table and transmitted endlessly. 
     When the system is initiated, then the DSP  132  transmits a sequence of test signals and detects combines the selected numeric representations and produces a numeric representation, which is a summation thereof. At this point, the DSP  132  provides the summed numeric representation to the DAC  136 , via the look-up table  130 . The DAC  132  produces a respective analog signal for each of the coils  142 A,  142 B and  142 N and provides it to the respective amplifier  140 A,  140 B and  140 N. The DSP  132  detects signals, which are received on the transmitting coils, respective of cross talk and other interference. At this stage, the DSP  132  can recalculate the waveforms, thereby compensating for the detected interference and update the look-up table  130 , accordingly. 
     Reference is now made to FIG. 7, which is a schematic illustration of a method for generating a complicated magnetic field waveform, operative in accordance with another preferred embodiment of the present invention. In step  180 , a plurality of numeric representations, of simple signals are computed. 
     In step  181 , a plurality of complex waveforms, each including a plurality of selected simple signals is determined. Each of the waveforms, is basically a super-positioning of a plurality of such simple waveforms at selected frequencies. For example, such a complex waveform can include: 
     
       
           S   complex ( t ) =A   1 ×sin(1000 π·t ) +A   2 ×sin(1100 π·t ) +A   3 ×sin(1500 π·t ) 
       
     
     It is noted that a complex waveform signal can include as many simple signals as desired. In general, this depends on many factors such as the power of the determining DSP, the speed of the communication between the various components of the system, the accuracy specified for the system and the like. At this point the DSP  132  processes the wave forms, with respective parameters, such as amplitude, offset and the like thereby producing a numeric expression of the complex waveform. It is noted that the DSP  132  can further determine a sequence. for transmitting the waveforms (step  182 ). 
     In step  183 , the numeric representations of the waveforms are stored in the storage unit, which in the example of system  100  is the look-up table  130 . 
     In step  184  the waveforms are retrieved and transmitted according to the determined sequence. The numeric expression of the complex waveform is converted into an analog signal by the digital to analog converter  136  and transmitted using the transmission section. 
     In step  185  the DSP detects cross talk and general interference, which are received from the AGC unit  134 . Accordingly, the DSP  132  modifies the waveforms so as to compensate for the detected cross talk and updates the storage unit accordingly (step  186 ). The waveforms stored in the look-up table  130  can now be transmitted continuously. It is noted that only a drastic change in the electromagnetic environment requires repeating of this procedure. 
     Hence. the present invention eliminates the need to co-compute the numeric representation of each of complex waveforms, which include each of the magnetic field signals, thereby dramatically increasing the speed in which such signals are produced. 
     The magnetic fields B 1 , B 2  and B N , in each of the coils  142 A,  142 B and  142 C are dependant on the currents I 1 , I 2  and I N , flowing there through. In a physically ideal system there would be independence between I 1 , I 2  and I N . However, any multi dimensional magnetic field generator incorporates some cross talk between the field generating elements. The X direction field generating coil induces currents in the Y and Z direction field generating coils, the Y direction field generating coil induces currents in the X and Z direction field generating coils and the Z direction field generating coil induces currents in the X and Y direction field generating coils. The measured currents are:              I   x          (   t   )       =         V   1     ·     sin        (       ω   1        t     )           R   1         ;         I   y          (   t   )       =             V   2     ·     sin        (       ω   2        t     )           R   2                     and                     I   z          (   t   )         =         V   N     ·     sin        (       ω   N        t     )           R   N                                  
     The actual currents, as transformed to voltage across resistors R 1 , R 2  and R N  are:              I   x          (   t   )       =           V   1     ·     sin        (       ω   1        t     )         +       B   1     ·     V   2     ·     sin        (       ω   2        t     )         +   …   +       N   1     ·     V   N     ·     sin        (       ω   N        t     )             R   1         ,                    I   y          (   t   )       =           A   2            V   1     ·     sin        (       ω   1        t     )           +       V   2     ·     sin        (       ω   2        t     )         +   …   +       N   2     ·     V   N     ·     sin        (       ω   N        t     )             R   2         ,              and                 I   z          (   t   )       =           A   3            V   1     ·     sin        (       ω   1        t     )           +       B   3            V   2     ·     sin        (       ω   2        t     )           +   …   +       V   N     ·     sin        (       ω   N        t     )             R   N         ,                          
     where A 2 , A 3 , B 1 , B 3 , N 1  and N 2  are predetermined coefficients. 
     According to the present invention, system  100  measures the cross-talk components in each axis and provides a respective compensation. In accordance with a further aspect of the invention, there is provided a method for compensating for cross talk between cnannels. Reference is now made to FIG. 8, which is a schematic illustration of a method for operating system  100 , operative in accordance with a further preferred embodiment of the invention. At first, the DSP  132  (FIG. 6) determines a plurality of function current signals (step  190 ), one for each axis. These functions are provided as electrical currents to the coils, which in turn produce magnetic fields (step  191 ). 
     In step  192 , the system measures the voltage values across the resistors connected in series with each of the coils. It is noted that these are high precision resistors and thus the system  100  can determine an accurate current value, from each of them for a respective one of the axis (step  193 ). 
     In step  194 , the system  100  determines the induced currents in each of the coils, by subtracting the original function current from the determined current value. In step  195  the DSP  132  determines a compensation function for each of the determined magnetic fields, according to the determined induced currents and combines each of the compensation functions with the respective current function signals (step  196 ). Finally, the system  100  repeats from step  190   
     In accordance with another aspect of the present invention, multi-frequency signals are used so as to overcome metal distortions. Each of the coils receives a signal, which includes a different set of frequencies. The signal, which is provided to each of the coils, is of the form:            F   i          (   t   )       =       ∑     i   =   1     N            A   i     ·     sin        (       w   i        t     )                                  
     where A is the amplitude vector for each of the frequencies. 
     The system of the present invention can be implemented in any invasive device, which is inserted within a living tissue. Reference is now made to FIGS. 2A and 2B. FIG. 2A is an illustration of a patient and an invasive system, generally referenced  200 , constructed and operative in accordance with another preferred embodiment of the invention. FIG. 2B is an illustration of a 3D image, a positioning representation and the super imposing of both of them. 
     System  200  includes a main unit  210 , an invasive device  202  and a display unit  206 . Invasive device  202  includes a 3D magnetic sensor  204 , which is located on its tip. It is noted that system  200  is generally similar to system  100 . The invasive device  202  can be selected from a plurality of invasive devices such as an endoscope, catheters, needles, surgery devices, and the like. 
     With further reference to FIG. 2B, the sensor  204  detects electromagnetic fields, which are generated within the main unit  210 , and produces a respective signal. The system  200  (FIG. 2A) analyses this information and produces a determination of the location and orientation of the sensor  204  (reference  222 ). It is noted that since the sensor  204  is firmly attached to the tip of invasive device  202 , then the determination of location and orientation also indicates the location and orientation of the tip of the invasive device  202 . 
     In the present example, the inspected living tissue is the head (reference  230 ) of a patient (reference  290 ). The system  200  combines a pre-scanned image (reference  220 ) of the inspected living tissue and the location and orientation of the sensor  204  (reference  222 ), thereby producing a superimposed image  224 . Superimposed image  224  provides visual information of the location and orientation of the tip  204  of invasive device  202 , within the inspected living tissue  204 . 
     According to this aspect of the invention the system  100  can be mounted on to a bronchoscope. Reference is now made to FIGS. 3A,  3 B and  3 C, which are illustrations of system  100  of FIG. 1A, incorporated within a bronchoscope, constructed and operative in accordance with a further preferred embodiment of the invention. 
     FIG. 3A shows a bronchoscope, referenced  260 , inserted into the lungs  280  of a patient. A typical bronchoscope includes three main devices, which are a lighting unit, a set of optic fibers for capturing the image at the tip of the bronchoscope and a surgical too. According to the present invention, a bronchoscope further, includes a sensor such as sensor  110 , attached to its tip. Reference is further made to FIG. 3C, which is an illustration in detail of the tip of the bronchoscope  260 , of FIG.  3 A. 
     Bronchoscope  260  includes an optic fiber  262 , a set of optic fibers  266 , a surgical tool  264  and sensor  110  of system  100 . Optic fiber  262  transfers light from an external source to the tip of the bronchoscope. The set of optic fibers  266  captures the image in the vicinity of the tip and optically conveys this image to an external optical assembly (not shown) for viewing by the physician. The surgical tool  264 , which in the present example is a remote controlled clamp, enables the operating physician to perform surgical actions. The sensor  110 , being firmly attached to the tip of surgical tool detects the electromagnetic fields in close vicinity of this tip and transfers this information to system  100 . 
     The system  100  analyzes this information and determines the location and orientation (reference  250 ) of the tip of the surgical tool  264 . The system  100  then superimposes the coordinates  250  of the tip of surgical tool  264   264  with a pre-detected image  252  of the treated area, which in the present example, is the lungs  280  of the patient. The outcome  254  is displayed on display unit  114  (FIG.  3 B). 
     It is noted that the diameter of the tip of the dilating catheter  260  is conventionally significantly larger than the diameter of the surgical tool  264 . Hence, when the surgical procedure requires accessing areas which are too narrow for the dilating catheter, then the physician can proceed with just the surgical tool, where the location and orientation of the tip of this tool are provided by system  100   264 . 
     According to another aspect of the present invention, the location and orientation detection system, can be combined with a catheter, thereby determining the position of its tip. Reference is now made to FIGS. 4A,  4 B and  4 C. FIG. 4A is an illustration of a patient, a catheter and a location and orientation detection system, constructed and operative in accordance with another preferred embodiment of the invention. FIG. 4B is an illustration of the superimposing of the location information  322  provided by the location and orientation detection system of FIG. 4A and a three dimensional image  320  of a treated portion of the body of the patient. FIG. 4C is an illustration in detail of the tip end of the catheter of FIG.  4 A. 
     Catheter  310  is a general dilation catheter, which is used to guide a specific device to the vicinity of the area to be treated. The physician operating the system inserts a mounting catheter  306 , which includes a balloon mechanism  312 . A sensor  304  is firmly attached to the end of the mounting catheter  306 . 
     The sensor  304  detects electromagnetic fields (produced by generator  302 ) in a plurality of directions and provides information to the processing unit  308  of system  300 . The processing unit  308  analyzes this information, thereby determining the location and orientation of the sensor  304 . The system  300  uses these coordinates to produces a superimposed image of the treated area (reference  324 ). 
     According to the present invention, the communication between the electromagnetic sensor and the analysis unit of the system can be in a wired or wireless manner. Reference is now made to FIG. 5, which is a schematic illustration of an inspection system, generally referenced  400 , constructed and operative in accordance with another preferred embodiment of the invention. 
     System  400  includes a base unit  402  and a remote unit  404 . The base unit  402  includes a receiver  412 , a three dimensional electromagnetic field generator  414 , a coordinate processor  410 , an imaging processor  418 , and imaging source  416  and a display unit  420 . The coordinate processor  410  is connected to the receiver  412 , the three-dimensionaL electromagnetic field generator  414  and the imaging processor  418 . The imaging processor  418  is further connected to the display unit  420  and to the imaging source  416 . 
     The remote unit  404  includes a storage unit  422 , a transmitter  424 , a processor  428 , a three-dimensional electromagnetic field sensor  430  and a biometric unit  426 . The processor  428  is connected to the storage unit  422 , the transmitter  424 , the three-dimensional electromagnetic field sensor  430  and the biometric unit  426 . It is noted that the base unit  402  can use any information received therein. with respect to the detected magnetic fields, so as to modify the electromagnetic fields, which are transmitted by generator  414 . 
     The biometric unit  426  is designed to perform an inner operation on the living tissue. It is noted that such a biometric unit can include an image detector such as a camera, a substance releasing unit for releasing materials at predetermined locations, according to the location and orientation of unit  404 , a sampling unit such an oxymeter. The biometric unit can further include a glucometer, a thermometer, an acidity detector and any other physiological probe which can detect predetermined properties of pre-specified tissues of the examined living tissue. According to another aspect of the present invention, biometric units of several types are included in unit  404 , such as a physiological probe and a video camera which detects the image of a specified organ of the examined patient. 
     The physiological probe provides information, with respect to the detected characteristics, to the processor  428 . It is noted that the processor can perform an interim analysis of this information, so as to determine if this physiological data is to be transmitted to the base unit  402 . 
     At the same time, the sensor  430  detects electromagnetic field properties in a plurality of directions and provides the detection results to the processor  428 . The electromagnetic fields are produced by the three-dimensional electromagnetic field generator  414 . It is noted that the system  400  can include a plurality of three-dimensional electromagnetic field generators, such as the one referenced  414 . The use of additional electromagnetic field generators enhances the location and orientation measurements accuracy. 
     The processor  428  packs the detection results with the physiological data and transmits it to the receiver  412 , using the transmitter  424 . It is noted that the processor  428  can also store selected portions of the data received from the physiological probe  426  and the sensor  430 , in the storage unit  422 . 
     The receiver  412  provides the received data to the coordinate processor  410 . The processor  410  extracts the data, which relates to the detected electromagnetic fields and determines the location and orientation of the sensor  430  at the time of detection 
     The processor  410  provides the coordinate location data to the imaging processor  418 , together with the physiological data. The imagine processor  418  uses this data together with a three dimensional image received from the imaging source  416 , to produce a superimposed image and displays it on the unit  420 . 
     Such a superimposed image can include the trail of acidity within the digestion system of the examined patient, where at each point of the journey of the remote unit, both location and acidity level are detected and recorded. 
     The remote unit  404  is basically designed to be inserted into the body and move about, with minor intervention from the physician. For example, the remote unit  404  can be designed as a capsuie which can be taken through the mouth, make its way through the digestion system of the patient, sampling various properties along the way, and transmit the findings along with the accurate location from which they were taken. 
     In accordance with a further aspect of the invention, the position and orientation device is combined with an inner body ultrasound transceiver, thereby providing a real-time three dimensional image generation system. Reference is now made to FIG. 9, which is a schematic illustration of a three dimensional imaging system, which combines an inner ultrasound transceiver and a location and orientation detector, generally referenced  500 , constructed and operative in accordance with another preferred embodiment of the invention. 
     System  500  includes an inner body ultrasound assembly  540 , a storage unit  532 , a three-dimensional image generator  530 , a combining processor  536 , a general location and orientation detector  534  and a display unit  536 . The inner body ultrasound assembly  540  includes an ultrasound detector  502  and a location and orientation detector  510 , which are firmly attached to each other. It is noted that detector  502  can be replaced with any type of ultrasound transceiver of sensor, such as an inner vascular ultrasound (IVUS) element, and the like. The inner body ultrasound assembly  540  is connected to the storage unit  532 . The three-dimensional image generator  530  is connected to the storage unit  532  and to the combining processor  536 . The combining processor  536  is further connected to the general location and orientation detector  534  and to the display unit  538 . It is noted that the storage unit  532  is redundant when the three-dimensional image generator  530  is powerful enough for real-time image processing. In this case, the inner body ultrasound assembly  540  is directly connected to the three-dimensional image generator  530 . 
     The inner body ultrasound assembly  540  detects a plurality of two dimensional ultrasound images, and a plurality of location and orientation readings of the ultrasound detector  502 , each associated with a selected one of the two dimensional ultrasound images. Each of the two dimensional ultrasound images presents a different slice of a scanned three-dimensional volume. Each such pair of a two-dimensional ultrasound image and a location and orientation reading of the ultrasound detector is stored, as a record, in storage unit  532 . It is noted that the location and orientation detector  510  can operate according to the electromagnetic methods, which are presented according to the present invention, as well as according to any other electromagnetic method which is known in the art, such as rotating field, simple magnetic feedback and the like. 
     The three-dimensional image generator  530  retrieves the records and produces a three dimensional representation of the scanned volume. This representation can be further combined with location and orientation data provided from another location and orientation detector which is associated with any surgical tool such as a camera, clamps, a laser device and the like. The final result, including a three dimensional representation of the scanned volume, combined with an indication of the location and orientation of the surgical tool. is displayed on display unit  538 . 
     Reference is now made to FIGS. 10A and 10B, which are illustrations in perspective of an inner body ultrasound assembly  540 , of FIG. 9, constructed and operative in accordance with another preferred embodiment of the invention. System  540  further includes a dilation catheter  508 , a mounting catheter  506  and a surgical tool  542 . The ultrasound transceiver  502  is fixed to the mounting catheter  506 , which is inserted in the dilation catheter  508 . The location and orientation detector  510  is attached to the rear side of the ultrasound transceiver  502 . The surgical tool  542  includes clamps, where the location and orientation detector  544  surrounds the tip of the guiding tube  546  thereof 
     The location and orientation detector  510  continuously detects the location and orientation of the ultrasound transceiver  502 . The ultrasound transceiver  502  continuously transmits and detects ultrasound waves, from its front end  504 , thereby generating an angular ultrasound slice image, generally referenced  512 A. The image  512 A is a two dimensional representation of the objects which are located in front of section  504 . 
     With reference to FIG. 10B, the user can direct the ultrasound transceiver  502  in various directions, for example by means of rotation, thereby producing additional angular ultrasound slice images such as the one denoted  512 B. Reference is now made to FIG. 10C, which is an illustration in perspective of a plurality of angular ultrasound slice images, generally referenced  512 . The angular ultrasound slice images  512 A (FIG.  10 A),  512 B (FIG.  10 B),  512 C and  512 D are two-dimensional representations of various sections of the scanned volume. These images are combined to a three dimensional image, by the three-dimensional image generator  530 . 
     It is noted that using system  500 , the physician can operate on the patient immediately after creating the image of the treated area and further update the image, at any desired moment, thereafter. 
     Reference is now made to FIGS. 11A and 11B, which are illustration in perspective of an inner body ultrasound assembly, generally referenced  550 , constructed and operative in accordance with another preferred embodiment of the invention. Inner body ultrasound assembly  550  includes a radial ultrasound transceiver  552  and a location and orientation detector  556 . The radial ultrasound transceiver  552  is mounted on a mounting catheter  554 , which is further inserted in a dilation catheter  558 . The location and orientation detector  556  is located at the tip of the mounting catheter  554 , near the base of the radial ultrasound transceiver  552 . As can be seen in FIG. 11A, the location and orientation detector  556  includes a single coil, which is twisted around the tip of the mounting catheter  554 . The inner body ultrasound assembly  550  can replace the inner body ultrasound assembly  540  of FIG.  9 . The operating user can move the inner body ultrasound assembly  550  back and forth (denoted by a bi-directional arrow) as well as in various directions as will be further illustrated in FIG. 11B, herein below. 
     The location and orientation detector  556  continuously detects the location and orientation of the tip of the mounting catheter  554 , and hence, the location and orientation of the base of the radial ultrasound transceiver  552 . The location and orientation detector  556  provides the detected information to the storage unit  532  (FIG.  9 ). The radial ultrasound transceiver  552  continuously detects a radial ultrasound slice image, generally referenced  570 . The radial ultrasound transceiver  552  provides the detected image information to the storage unit  532 . 
     The storage unit  532  includes a plurality of records, each including a two dimensional radial slice of the scanned volume and a location and orientation or a predetermined point with respect to that slice. Reference is now made to FIG. 11B, which is an illustration in perspective of a plurality of radial ultrasound slice images, generally referenced  570 . Radial angular ultrasound slice images  570 A,  570 B,  570 C,  570 D,  570 E and  570 F are two-dimensional representations of various sections of the scanned volume. These images are combined to a three dimensional image, by the three-dimensional image generator  530 . 
     Reference is now made to FIG. 12, which is a schematic illustration of a method for operating system  500 , operative in accordance with a further preferred embodiment of the invention. In step  580 , the ultrasound detector  502  with the location and orientation detector  510  are inserted into the body of the patient and located at the area to be inspected and treated. In step  582  the ultrasound detector  502  detects a plurality of two-dimensional images (references  512  in FIG.  9 C). In step  584 , the location and orientation detector  510  detects the location and orientation of each of the two-dimensional images. 
     In step  586 , records, which include image and location and orientation information, are stored. It is noted that this step is redundant, provided the three-dimensional image generator is powerful enough. In step  588 , the three image generator  530  processes the records thereby producing a three dimensional representation of the scanned volume. This image, produced from the inner part of the scanned volume can now be displayed. For example, an inner body ultrasound assembly using MPS sensor with an IVUS can be used to produce reconstructed three-dimensional images of blood vessels. 
     In step  590 , the system receives additional location and orientation information which are originated from a different location and orientation detector, associated with any of a plurality of surgical tools. Such a surgical tool can be selected from the list consisting of any type of operational catheter, a camera, a lighting device and the like. It is noted that the present invention is not limited to one additional location and orientation sensor, rather a plurality of such sensors can be incorporated in a single system, where each is indicated on the three dimensional image (step  592 ) and displayed thereafter (step  594 ). 
     In accordance with a further aspect of the invention, there is provided a method for positioning a location and orientation detector on a reference image, prior to maneuvering it inside the body of the patient. 
     Reference is now made to FIG. 13, which is a schematic illustration of a method for initially positioning a location and orientation detector onto a reference image, operative in accordance with a further preferred embodiment of the invention. The method of the present invention utilizes known locations on the treated area, which are visible thereon and also visible on the reference image, which is to be associated therewith. At first, a plurality of such locations is determined (step  600 ). With respect to FIG. 3B, the main junctions of the lung system are easily detected, so are specific bone areas such as the solar plexus, vocal cords. and the like 
     In step  602 , the location and orientation detector is places in each of these locations and a reading is taken accordingly (step  604 ). It is noted that two or three such locations are enough to position the detector within the reference image. Any more such locations can be used to improve the accuracy of the positioning process. Finally the reference image is oriented onto the treated area (step  606 ) and the location and orientation detector can be positioned within the reference image (step  608 ). 
     In accordance with a further aspect of the invention, the position and orientation system of the invention is incorporated in laparoscopy devices and procedure Reference is now made to FIG. 14, which is an illustration of two minimal invasive tools, generally referenced  630  and  640 , constructed and operative in accordance with another preferred embodiment of the invention. 
     Minimal invasive tool  630  is generally a guiding element, which is ended by a surgical tool, generally referenced  632 . The surgical tool  632  can be any known device which is used in the process of minimal invasive surgery, such as a marking device, devices used for performing biopsies, surgical devices, laser cutting, treating and tissue welding devices and the like. 
     Minimal invasive tool  640  is generally similar to tool  630  and includes a surgical tool  642  and a pair of position and orientation sensors  644  and  646 , where sensor  644 is directed in the axial direction of tool  640  and sensor  646  is directed perpendicular thereto. 
     The minimal invasive tools  630  and  640  are inserted into the body of the patient through minimal size holes,  638  and  648 , respectfully, in the skin layer  636 . The use of such techniques reduces the trauma caused to the treated area. Conventional laparoscopy often requires that a camera and illumination means be inserted into the treated volume, since a simple line of sight is not available to the physician. In accordance with this aspect of the invention, no camera or illumination device have to be inserted into the treated volume. The position and orientation of the surgical tools are determined by the system of the invention and are indicated on an image of the treated volume, for the physician to see. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove Rather the scope of the present invention is defined only by the claims, which follow.