CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Patent Application No.

13/798,637 filed March 13, 2013, the disclosure of which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] Not Applicable.

BACKGROUND OF THE INVENTION

[0003] The present invention relates to systems and methods for tracking and navigating medical devices. More particularly, the invention relates to a method for tracking and navigating an interventional medical device while utilizing low-voltage feedback signals generated by an array of electrical sensors on the interventional medical device.

[0004] In the medical arts, interventional medical devices, such as catheters or endoscopes, are frequently used to diagnose and treat various disorders in a patient, such as clogged or blocked blood vessels. An interventional medical device is introduced into a blood vessel of a patient by, for example, making an incision in the patient over the blood vessel and inserting the interventional medical device into the blood vessel of the patient. A interventional medical device operator such as a physician then maneuvers the interventional medical device through the blood vessels of the patient until the interventional medical device is properly situated to diagnose or treat the disorder. Similar techniques are used to insert interventional medical devices into other types of lumens within a patient.

[0005] In maneuvering the interventional medical device through the blood vessels or other lumens within the patient, there is a recurrent need to know the location of the interventional medical device within the body space of the patient. Conventional imaging systems create an of the blood vessel or other lumen to provide 3-dimensional spatial relationships. If the position in three dimensions of the imaging head on the interventional medical device can be determined, then through use of three- dimensional imaging software, the true positions and locations of the curves, twists, and turns, as well as the locations of the branch points, of the lumens can be determined. Knowing the true positions allows a more accurate map of the patient to be created, which yields more effective diagnosis and treatment of the patient. For example, gathering accurate 3-D position data allows for an accurate blood flow map and consequent blood flow monitoring and modeling.

[0006] Traditionally, x-ray based technology, such as computed tomography (CT] has been used to provide a global roadmap of X-ray visible devices, showing their position within the patient. However, prolonged exposure to X-rays may be harmful to the patient, and it is therefore desirable to avoid such exposures. Thus there is a need for a tracking system which can easily determine the location of a interventional medical device within a patient, without exposing the patient to harmful side effects, and which can be used with a wide variety of interventional medical devices or other imaging medical devices.

SUMMARY OF THE INVENTION

[0007] The present invention overcomes the aforementioned drawbacks by providing a system and method that tracks and navigates an interventional medical device during a medical procedure without using external imaging such as fluoroscopy, computed tomography (CT] and magnetic resonance imaging (MRI}. In particular, the present invention utilizes the generation of low-voltage feedback signals generated by an array of electrodes on the interventional medical device. The feedback signals create an electric image of the local volume surrounding the interventional medical device, thereby eliminating the need for electromagnetic tracking or radiation for guidance during the positioning of the interventional medical device by combining diagnostic or interventional imaging with intra-operative signal processing.

[0008] In accordance with one aspect of the invention a system for tracking a position of an interventional medical device configured to be deployed into a subject during a medical procedure is disclosed. The system includes an interventional medical device configured to be deployed into a subject during a medical procedure. The system further includes at least one electrical sensor disposed along the interventional medical device to receive electrical signals available to the interventional medical device when deployed within the subject during the medical procedure and generate a feedback signal based on the received electrical signals. An anatomical dataset including anatomical information about the subject is stored on a non-transitive memory. The system includes a processor, communicatively coupled to the electrical sensor, which is configured to access the anatomical dataset from the non-transitive memory in order to receive the feedback signal from the electrical sensor and analyze the feedback signal to identify positional information of the interventional medical device relative to the anatomical dataset. The position of the interventional medical device with respect to the anatomical dataset is then communicated on a display coupled to the processor.

[0009] In accordance with another aspect of the invention, a method for tracking a placement of an interventional medical device deployed into a subject is disclosed. The method includes acquiring an anatomical dataset of the subject and providing an interventional medical device having at least one electrical sensor disposed along the interventional medical device. The interventional medical device is configured to be positioned within the subject during a medical procedure utilizing the interventional medical device. A feedback signal generated from the electrical sensor is then processed and analyzed to identify positional information of the interventional medical device. A position of the interventional medical device with respect to the anatomical dataset is identified and the position of the interventional medical device with respect to the anatomical dataset is then displayed.

[0010] The foregoing and other aspects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims and herein for interpreting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 is a block diagram of a system configured to implement the present invention.

[0012] Fig. 2 is a block diagram of an interventional medical device with electrical sensors configured to implement the present invention.

[0013] Fig. 3 is a flow chart setting forth the steps of processes for mapping a feedback signal to an anatomical dataset in accordance with the present invention.

[0014] Fig. 4 is a schematic diagram of a vessel and corresponding impedance measurement over time as the interventional medical device is navigated through the vessel using the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Referring particularly now to Fig. 1, a subject 12 on a patient bed 10 with an interventional medical device 14 inserted into the femoral artery and the carotid artery is shown. The interventional medical device 14 may be, for example, a catheter, laparoscope or endoscope. An electrical source 16 may be externally attached to the subject 12 or internally attached to the interventional medical device 14, or both as shown in Fig. 2. The electrical source 16 can emit an electrical signal to be received by a distal electrical sensor 18 and a proximal electrical sensor 20 coupled to the interventional medical device 14, as shown in Fig. 2. The electrical source 16 may emit, for example, low voltage, high frequency signals. The distal electrical sensor 18 and the proximal electrical sensor 20 may be, for example, electrodes coupled to the interventional medical device 14. The distal electrical sensor 18 and the proximal electrical sensor 20 generate a feedback signal 22, shown in Fig. 4, based on the received electrical signals emitted by the electrical source 16.

[0016] A coupling device 24 is configured to receive the feedback signal 22 from the distal electrical sensor 18 and the proximal electrical sensor 20 and transmit the feedback signal 22 to a processor 28. The processor 28 is communicatively coupled to the distal electrical sensor 18 and the proximal electrical sensor 20 to receive and measure the feedback signal 22. The processor 28 is configured to access a non- transitive memory 30 to receive a previously acquired anatomical dataset which includes anatomical information about the subject 12. The anatomical dataset may include, for example, a prior fluoroscopy, computed tomography (CT] or magnetic resonance imaging (MRI] dataset. Inputs 26 are provided to the processor and can include patient demographics, a patient's previous medical history, and the like. A display 32 is also coupled to the processor 28 to communicate the position of the interventional device 14 with respect to the anatomical dataset.

[0017] Referring now to Fig. 2, the interventional medical device 14 is shown. As previously described, the distal electrical sensor 18 and the proximal electrical sensor 20 may be coupled to the interventional medical device 14. The distal electrical sensor 18 and the proximal electrical sensor 20 are spaced apart from one another a predetermined distance 44 in order to identify positional information from the of the interventional medical device 14 during a medical procedure. The processor 28 is communicatively coupled to the distal electrical sensor 18 and the proximal electrical sensor 20. The electrical source 16 may be, for example, internal to the subject 12 and may be, for example, an electrical sensor coupled to the interventional medical device 14. The electrical source 16 is coupled to a signal generator 42 and configured to emit an electrical signal to be received by the distal electrical sensor 18 and the proximal electrical sensor 20.

[0018] Referring now to Fig. 3, a flow chart setting forth exemplary steps 100 for mapping a feedback signal 22 to an anatomical dataset is provided. To start the process, a stimulus is delivered at process block 102. The stimulus can be an electrical signal emitted by the electrical source 16. The nature of the emitted electrical signal is not limited to a sinusoidal or periodic waveform, but should have a high signal-to-noise ratio. As described above, the electrical source 16 can be configured to emit an electrical signal from a location internal to the subject 12, from a location external to the subject 12 or from other defined positions. If the electrical source 16 is configured to emit an electrical signal from a location external to the subject 12, the electrical signal propagates into the subject 12 to the distal and proximal electrical sensors 18, 20. The electrical source 16 may also be formed by external signal dischargers (ESD] attached to the subject 12 and configured to create a spatial varying signal overlay. During an inspection scan the spatial varying signal overlay can be observed and mapped to the geometrical information acquired through the previously acquired anatomical dataset. Throughout the intervention the ESD signal mix can then be mapped directly to the inspection scan, which allows localization and navigation of the interventional medical device 14 based on pre-interventional imaging.

[0019] At process block 104 the distal electrical sensor 18 and the proximal electrical sensor 20 receive the electrical signal emitted from the electrical source 16. In response, the distal electrical sensor 18 and the proximal electrical sensor 20 generate the feedback signal 22 and send the feedback signal 22 to the processor 28. The feedback signal 22 indicates, for example, bio-electric signals received by the distal electrical sensor 18 and the proximal electrical sensor 20 thereby creating an electric image of a local volume surrounding the interventional medical device 14. The local volume may be, for example, a vessel 34 as shown in Fig. 4. The processor 28 then performs a fast Fourier transform to the feedback signal 22 at process block 106 in order to analyze the feedback signal 22 and facilitate removal of signal noise.

[0020] Once the fast Fourier transform is performed to the feedback signal 22, the magnitude of the feedback signal 22 is determined at specific frequencies at process block 108. Specifically, the magnitude of the feedback signal 22 at frequencies below 5 kHz are reviewed due to ionization interferences at low frequencies. An impedance measurement 40 waveform of the feedback signal 22 is then calculated at process block 110, as shown in FIG. 4, and mapped over time. The feedback signal 22 is then mapped to the anatomical data set at process block 112.

[0021] As illustrated in Fig. 4, the impedance measurement 40 waveform of the feedback signal 22 from both the proximal electrical sensor 20 and the distal electrical sensor 18 are shown. From the previously acquired anatomical dataset a reconstruction of the subject's 12 vessel 34 is provided. As the user navigates the interventional medical device 14 through the vessel 34, the interventional medical device 14 facilitates the transmission and simultaneous recording of the feedback signals 22 on the array of distal and proximal sensors 18, 20, giving rise to an electrical image. During the medical procedure, the feedback signals 22 are reconciled with the anatomical dataset, and the position of the interventional medical device 14 is displayed within the medical images on the display 32. The medical images provide the user positional information and allows the guidance of interventional medical device 14.

[0022] More specifically, as the user navigates the interventional medical device

14 through the vessel 34, the impedance measurement 40 waveform of the feedback signal 22 from both the proximal electrical sensor 20 and the distal electrical sensor 18 are mapped over time, as illustrated in Fig. 4. When the interventional medical device 14 reaches a first bifurcation 36, or extreme geometry change, in the vessel 34 while the user is navigating the interventional medical device 14 in a first direction, a corresponding change in the impedance measurement 40 occurs. As shown in Fig. 4, the first bifurcation 36 occurs approximately at 14-15 seconds as indicated on the horizontal time axis, such that the distal electrical sensor 18 passes the first bifurcation 36 slightly before the proximal electrical sensor 20 passes the first bifurcation 36. Similarly, when the in interventional medical device 14 reaches a second bifurcation 38, in the vessel 34 while the user is navigating the interventional medical device 14 in the first direction, a corresponding change in the impedance measurement 40 occurs. As shown in Fig. 4, the second bifurcation 38 occurs approximately at 16-17 seconds as indicated on the horizontal time axis, such that the distal electrical sensor 18 passes the second bifurcation 38 slightly before the proximal electrical sensor 20 passes the second bifurcation 38.

[0023] As the user retracts the interventional medical device 14, or moves the interventional medical device 14 in a second direction that is opposite the first direction, the interventional medical device 14 passes the second bifurcation 38 and the first bifurcation 36 in the vessel 34. Similar to movement in the first direction, corresponding changes in the impedance measurement 40 occurs while navigating the interventional medical device 14 in the second direction as shown in Fig. 4. The impedance measurement 40 waveform of the feedback signal 22 is illustrated a symmetrical signal in Fig. 4 as a result of the electrical source 16 being coupled to the interventional medical device 14. However, if the electrical source 16 is configured to emit an electrical signal from a location external to the subject 12, the electrical signal propagates into the subject 12 to the distal and proximal electrical sensors 18, 20, thereby creating a differential signal.

[0024] By observing the biological electric signals at process block 114 and mapping the biological electric signals to spatial properties retrieved from the anatomical dataset at process block 112, the current position of the interventional medical device 14 can be determined at process block 116. Because the pre-determined distance 44 between the distal and proximal electrical sensors 18, 20 are known, the processor 28 can identify positional information of the interventional medical device 14 relative to the anatomical data set can be identified based on the impedance measurement 40. Once the positional information of the interventional medical device 14 is known, a velocity measurement can be computed because a positional change and changes in time are known at process block 118.

[0025] In summary, the present invention is advantageous by providing a system and method that tracks and navigates an interventional medical device during a medical procedure without using external imaging such as fluoroscopy, computed tomography (CT] and magnetic resonance imaging (MRI}. In particular, the present invention utilizes the generation of low-voltage feedback signals generated by an array of electrodes on the interventional medical device. The feedback signals create an electric image of the local volume surrounding the interventional medical device, thereby eliminating the need for electromagnetic tracking or radiation for guidance during the positioning of the interventional medical device by combining diagnostic or interventional imaging with intra-operative signal processing. [0026] The present invention has been described in terms of one or more preferred embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly stated, are possible and within the scope of the invention.