Method and system for detecting contact status using electrode

Abstract

To provide medical devices and systems and methods of detecting contact between electrodes on a medical device and adjacent tissue based on measured impedance.SOLUTION: A method of determining a contact status of electrodes includes applying drive signals between pairs of electrodes, measuring a bipolar electrode complex impedance (BECI) value generated in response to the drive signals over a collection period, and determining a baseline BECI value representing a minimum value measured during the collection period. The method further includes determining a contact status of the electrode by applying drive signals between pairs of electrodes over a given interval, measuring a BECI value generated in response to the drive signals, measuring a peak-to-peak value associated with the BECI values measured over the given interval, and determining a contact status by determination based on a combination of the baseline BECI value, the measured BECI value, and the peak-to-peak value associated with the measured BECI values.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates generally to medical devices and systems and methods for detecting contact between electrodes of a medical device and adjacent tissue based on measured impedance. [Background technology]

[0002] Catheters are utilized for many operations within the human body. In many such applications, whether to collect data from the surrounding tissue or to administer therapy, it is important to determine the proximity of the catheter, and particularly the electrodes that collect data or administer therapy, to adjacent tissue. Many methods are utilized to make this determination, such as monitoring the electrocardiogram signal (e.g., the voltage measured between the electrodes) and / or the impedance of the electrodes. For example, impedance is generally understood to increase in response to contact with tissue. However, many other factors can also result in impedance variations, including the location of the electrode within the body (i.e., different ventricles may be exposed to different amounts of blood flow and exhibit different impedance values) and the movement of the surrounding tissue, e.g., from the heartbeat. These factors make it difficult to rely on raw electrode impedance measurements. It would therefore be beneficial to develop a method for more reliably detecting contact based on such impedance measurements. Summary of the Invention [Means for solving the problem]

[0003] According to some aspects, a method for determining an electrode contact state includes applying a drive signal between an electrode pair and measuring, over a collection period, a bipolar electrode current generated in response to the drive signal. ComplexThe method further includes measuring impedance (BECI) values ​​and determining a baseline BECI value representing the minimum value measured during a collection period. The method further includes determining the contact condition by applying a drive signal between the electrode pair for a fixed interval, measuring BECI values ​​generated in response to the drive signal, and determining a baseline BECI value related to the measured BECI values ​​over the predetermined interval. Peak to Peak BECI values ​​and baseline BECI values, measured BECI values, and related Peak to Peak determining a contact state based on the combination of values; and determining a contact state of the electrode by

[0004] According to another aspect, a system for use with a medical device configured for insertion into a patient includes a signal generator configured to apply a drive signal to one or more pairs of electrodes disposed on the medical device, a measurement circuit configured to measure a response of the electrode pairs to the drive signal, and a contact assessment module. The contact assessment module comprises a bipolar electrode for each of the electrode pairs. Complex Generate impedance (BECI) values ​​and determine a baseline BECI value representing the minimum BECI value measured during a collection period, subsequently measuring BECI values ​​generated in response to the applied drive signal over a predetermined interval, and determining a time series associated with the BECI values ​​measured over the predetermined interval. Peak to Peak values ​​and compare baseline BECI values, measured BECI values, and values ​​related to measured BECI values. Peak to Peak and determining a contact condition based on a combination of the values.The system further comprises a display for indicating a proximity of the electrode to the tissue based on the output received from the contact assessment module.

[0005] According to another aspect, a contact assessment system for determining a contact status of an electrode included as part of an electrode pair located at a distal end of a medical instrument includes an input configured to receive collected signals in response to a source signal applied to the electrode pair, and a processor operative upon execution of certain program instructions stored in a computer readable storage medium, the execution of the certain program instructions causing the processor to determine a contact status of a bipolar electrode based on the input signals received during a collection period. Complex The method includes calculating impedance (BECI) values, determining a baseline BECI value representing the minimum value measured during a collection period, and then determining an electrode contact state by applying a drive signal between the electrode pair for a predetermined interval. The processor measures the BECI values ​​generated in response to the applied drive signal for the predetermined interval, and generates a BECI associated with the BECI values ​​measured over the predetermined interval. Peak to Peak values ​​and compare baseline BECI values, measured BECI values, and values ​​related to measured BECI values. Peak to Peak A combination of values ​​is used to determine the contact state of the electrodes. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a diagrammatic depiction of a system including a medical device for insertion into a patient, according to some embodiments, configured to utilize measured bipolar electrode complex impedance between electrodes to determine a proximity or contact state of one or more electrodes located at a distal end of the medical device.

[0007] [Diagram 2] FIG. 2 is a diagrammatic depiction of a distal end of a medical device having multiple splines and multiple electrodes disposed on each spline, according to some embodiments.

[0008] [Diagram 3]FIG. 3 is a flow chart illustrating steps utilized to determine the contact status of electrodes placed on a medical device using bipolar electrode complex impedance (BECI) measurements, according to some embodiments.

[0009] [Figure 4] FIG. 4 is a flow chart illustrating steps utilized to determine a contact condition based on a combination of a BECI baseline value, a measured BECI value, and a peak-to-peak BECI value, according to some embodiments.

[0010] [Diagram 5] FIG. 5 is a flow chart illustrating steps utilized to determine a contact condition based on a combination of a BECI baseline value, a measured BECI value, and a peak-to-peak BECI value, according to some embodiments.

[0011] [Figure 6] FIG. 6 is a diagrammatic depiction of components utilized to measure impedance between two electrodes placed on a medical device, according to some embodiments.

[0012] [Figure 7] FIG. 7 is a diagrammatic depiction of a distal end of a medical device having an array of electrodes arranged in a plane, according to some embodiments.

[0013] [Figure 8] FIG. 8 is a pictorial depiction of a distal end of a medical device having multiple splines for holding one or more electrodes, according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] According to some embodiments, the claimed invention provides a method for determining the proximity or contact state of a pair of electrodes to tissue using a bipolar electrode. ComplexThe claimed invention utilizes impedance (BECI) measurements. The ratio of a baseline BECI value (representing the BECI when the electrodes are not in contact with tissue) to a measured BECI value is calculated for a given interval (e.g., 1 second). Peak to Peak It is used in combination with the measured BECI value to determine contact.

[0015] 1 is a schematic depiction of a system 100 including a medical device 102 and a local system 103. In some embodiments, the local system 103 includes a switch 108, a digital-to-analog (D to A) converter 110, a filter 112, an analog-to-digital (A to D) converter 114, a filter 116, a display 130, and an electronic control unit (ECU) 118, which may include a signal source 120, a synchronous demodulation circuit 122, a contact assessment module 124, a memory 126, and a processor 128. In some embodiments, one or more surface patch electrodes 105 may be attached to the patient's skin.

[0016] In some embodiments, the medical device 102 is an elongated medical device, such as a diagnostic and / or therapeutic catheter, introducer, sheath, or other similar type of device. The medical device 102 includes a distal end 104 and a proximal end (not shown) that includes a handle that is manipulated by a technician and an interface for interfacing the medical device 102 to a local system 103. The distal end 104 may include various sensors and / or components for locating / navigating the distal end 104 within a patient, mapping physiological parameters within the patient, and providing therapy. In particular, the distal end 104 of the medical device includes multiple electrodes that may be utilized for one or more of these purposes.

[0017] The contact state of one or more electrodes located at the distal end 104 of the medical device 102 may be a bipolar electrode. ComplexThe electrical impedance (BECI) measurements are based on the electrical impedance (BECI) measurements. In general, BECI measurements are generated by driving an excitation signal between two electrodes that form a bipolar pair. The resulting voltage at each electrode is measured. Complex The measured BECI measurements are utilized to derive an impedance signal. The contact assessment module 124 utilizes the measured BECI measurements to determine a contact state, as described in more detail with respect to the steps illustrated in FIGS. 3-5. In some embodiments, the term "contact state" is a binary determination of whether the electrode is "in contact" or "not in contact" with the tissue. In other embodiments, the term "contact state" may include additional contact states, such as "intermittent contact." In still other embodiments, the term "contact state" may refer to the proximity of the electrode to the adjacent tissue.

[0018] In the embodiment shown in FIG. 1, a signal source 120 is utilized to generate excitation signals. In some embodiments, the signal source 120 generates one or more excitation or drive signals, each at a unique frequency. More specifically, the signal generator 120 may generate a plurality of excitation or drive signals having unique frequencies, in one embodiment, within a range of about 1 kHz to above 500 kHz, more typically within a range of about 2 kHz to 200 kHz, and even more typically within a range of about 10 kHz to about 20 kHz. Each of the drive signals may have a constant current, in one embodiment, typically within a range of 1-200 μA, more typically about 5 μA. The signal generator 120 may also generate signals involved in determining the location of the electrodes within the patient's body, which may be utilized, for example, for mapping, navigation, and / or delivery of therapy. The digital signals generated by the signal source 120 are converted to analog signals by the D-to-A converter 110 and provided to the selected bipolar electrodes via the filter 112 and the switch 108. In response to an analog signal provided between selected bipolar electrodes, the resulting voltage is measured at the electrode pair by the switch 108, filter 116, A-to-D converter 114, and synchronous demodulation circuitry 122. In some embodiments, the switch 108 selects the electrode to monitor in response to an excitation or drive signal provided. The filter 116 and A-to-D converter 114 convert the analog signal to a digital signal that the ECU 118 can manipulate. The synchronous demodulation circuitry 122 separates the signals from one another based on the frequency of the excitation or drive signals, allowing multiple bipolar electrode pairs to be analyzed substantially simultaneously based on multiple excitation or drive signals provided to the electrode pairs.

[0019] In some embodiments, the memory 126 may be configured to store respective data for the medical device 102, the patient, and / or other data (e.g., calibration data). Such data may be known prior to the medical procedure (medical device specific data, number of catheter electrodes, etc.) or may be determined and stored during the procedure. The memory 126 may also be configured to store instructions that, when executed by the processor 128 and / or the contact assessment module 124, cause the ECU 118 to perform one or more methods, steps, functions, or algorithms described herein. For example, but not by way of limitation, the memory 126 may store instructions for storing respective impedances of one or more electrodes of the medical device 102 (e.g., bipolar electrodes, Complex The ECU may include data and instructions for determining a contact status of one or more electrodes (impedance or BECI measurements) and utilizing the impedance measurements to determine a contact status of one or more electrodes. In some embodiments, the contact assessment module 124 utilizes a processor, application specific integrated circuit (ASIC), or other type of processor to execute instructions stored in the memory 126 to perform the functions described in FIGS. 3-5. The ECU may be coupled to a display 130, which may display an output of the sensed tissue (e.g., heart), the medical device (not shown), and / or the determined contact status of one or more electrodes of the medical device 102.

[0020] FIG. 2 is a diagrammatic depiction of a distal end 202 of a medical device 200 having multiple splines and multiple electrodes 204a, 204b disposed on each spline disposed adjacent to cardiac tissue, according to some embodiments. In the embodiment shown in FIG. 2, the electrodes 204a, 204b form a bipolar electrode pair. BECI measurements are generated by providing an excitation signal to the electrodes 204a and 204b, which results in a current flow between the electrodes 204a and 204b, as indicated by the dashed arrows 208a, 208b. At least a portion of the current 208a, 208b flows through the patient tissue 206 at the electrode-tissue interface, thereby affecting the inductive, capacitive, and resistive effects of the electrode response to the drive signal. That is, tissue contact affects the impedance measurements of the electrodes 204a, 204b. Generally, when the electrodes 204a, 204b are not in contact with the tissue 206, a circuit is formed in the patient's blood pool and the BECI measurements are decreased due to the conductive path formed in the blood pool. As shown in FIG. 2, when the circuit path includes the tissue 206, the BECI measurements are increased reflecting the higher impedance of the tissue 206 compared to measurements made in the blood pool. As will be described in more detail with respect to FIGS. 3-5, the BECI measurements are utilized to determine the tissue contact status of the electrodes. In some embodiments, the contact status may include a determination of contact or no contact. In other embodiments, the contact status may include other contact statuses, such as intermittent contact, or a range of contact statuses.

[0021] In other embodiments, the distal end of the medical device can incorporate a number of different shapes and / or designs. In some embodiments, the distal end of the medical device is a grid-like array of electrodes, as shown in more detail in FIG. 7. In other embodiments, the distal end of the medical device includes a number of splines, but each spline includes only a single electrode, as shown in FIG. 8. In this embodiment, a bipolar electrode pair is formed between electrodes located on adjacent splines. In other embodiments, the distal end of the medical device can be curved or looped, with a number of electrodes spaced along the distal end. Similarly, a variety of different types, shapes, and sizes of electrodes may be utilized at the distal end of the medical device.

[0022] FIG. 3 illustrates a bipolar electrode according to some embodiments. Complex 3 is a flow chart illustrating steps utilized to determine contact status of electrodes placed on a medical device using impedance (BECI) measurements. BECI measurements include both real and imaginary (quadrature) portions. In some embodiments, BECI measurements utilize both real and imaginary portions. In other embodiments, only the real portion of the BECI measurements is utilized. For simplicity, reference is made to BECI measurements that are comprised of only a real portion (e.g., magnitude). However, it should be understood that in other embodiments, BECI measurements may include both real and imaginary portions. At step 302, a medical device is placed within a body cavity of a patient. For example, a cardiac application may include positioning the medical device within the patient's heart, and more specifically, within one of the patient's ventricles.

[0023] At steps 306 and 308, a baseline BECI magnitude is determined for each electrode. Ideally, the baseline BECI magnitude represents the impedance of the electrode when it is located in the blood pool and not in contact with tissue. In some embodiments, at step 306, multiple BECI measurements are collected for each electrode during a collection period. Generally, the lowest BECI measurement recorded during a collection period represents the electrode impedance when the electrode is not in contact with tissue. Thus, at step 308, the baseline BECI value M B is determined as the smallest magnitude measured during the collection period. As will become apparent, the baseline BECI value M B One advantage of determining the baseline BECI value M for each individual electrode is that B Determining the baseline BECI value M accounts for differences in impedance due to differences in size, shape, etc. between the electrodes. For example, referring to FIG. 2, the baseline BECI value M B is determined for electrode 204a, and another baseline BECI value M B is determined for electrode 204b. In some embodiments, the surgeon may be instructed to move the distal end of the medical device within the patient's body cavity to ensure that a baseline measurement can be established for each electrode where the electrode is not in contact with tissue.

[0024] In step 310, the baseline BECI value M for each electrode is calculated. B After determining, BECI values ​​are measured at one or more electrodes. In some embodiments, the BECI values ​​are collected over a predefined interval or window (e.g., 1 second). In some embodiments, the BECI values ​​collected over the predefined interval or window are stored in memory 126. For example, memory 126 may implement a circular queue in which older measurements are rewritten with newer measurements. In other embodiments, other data structures may be utilized to collect and store the BECI values ​​during the predefined interval. In some embodiments, the duration of the predefined interval is equal to about 1 second, but may be shorter or longer depending on the application.

[0025] In step 312, the BECI values ​​collected over a given interval are calculated to represent the measured difference between the maximum and minimum BECI values ​​collected for a given electrode within the given interval. Peak to Peak BECI value (PP) is calculated. Peak to Peak The BECI value increases Peak to Peak The measured difference, calculated as the BECI value, is the calculated increase in the BECI value measured for a given electrode. Peak to Peak In the case of BECI values, if the measured BECI value decreases over a given interval, Peak to Peak The BECI value will be zero. Conversely, if the measured BECI value increases over a given interval, Peak to Peak The BECI value will be the difference between the minimum and maximum BECI values ​​measured during that interval. As will be described in more detail below. Peak to Peak The BECI value is utilized in combination with the baseline BECI magnitude and the measured BECI magnitude (i.e., the most recently measured BECI value) to determine the contact condition. Peak to Peak The BECI value indicates (at least) intermittent tissue contact with the electrode. In some embodiments, Peak to Peak Increase the BECI value Peak to Peak Limiting the BECI value is beneficial in preventing loss of contact with tissue, which would likely result in a decrease in the measured BECI value as the electrode moves from contact with the tissue to contact with the blood pool, from being interpreted as contact with tissue. Peak to Peak Preferably, the BECI value is interpreted not to include decreasing magnitudes of the measured BECI value, which are indicative of contact, or even intermittent contact, with the tissue. Peak to Peak Utilizing increasing BECI values ​​to determine the BECI value ensures that an electrode that moves from the blood pool to some level of contact with adjacent tissue is interpreted as indicating at least some level of contact with tissue.

[0026] In step 314, for each electrode, the magnitude of the baseline BECI M B , the magnitude M of the current BECI, and over a given interval Peak to Peak Based on the combination of BECI values ​​P P , the contact state is determined. Various combinations of these values ​​may be utilized, one of which is illustrated in FIG. 4. In general, the magnitude M of the current BECI is used as one factor in determining the contact state, and the magnitude M of the baseline BECI is used as the other factor in determining the contact state. B and these may be related to each other as ratios. Peak to Peak The BECI value provides another factor that can be used to determine contact status: the baseline BECI magnitude, the current BECI magnitude, and Peak to Peak By using a combination of BECI sizes, bipolar electrodes Complex Based on the impedance measurements, the contact state is more reliably determined.

[0027] At step 316, the contact status of each of the multiple electrodes is displayed to the technician / physician (e.g., via the display 130). In some embodiments, a graphical user interface is provided to display various degrees of contact status (e.g., no contact, intermittent contact, contact in progress).

[0028] FIG. 4 illustrates a method for determining a contact variable D according to some embodiments, using a BECI baseline value, a measured BECI value, and Peak to Peak 4 is a flow chart showing the steps utilized to determine a contact condition based on a combination of BECI values. In step 402, a baseline bipolar impedance ComplexAn impedance (BECI) value is calculated for each electrode. As described above, in some embodiments, a baseline BECI value for each electrode is determined by monitoring the BECI values ​​associated with the electrode over a collection period and selecting the minimum value as the baseline BECI value. In some embodiments, the BECI values ​​are filtered so that momentary contact between electrodes that results in an abnormally low BECI value is not utilized as the baseline BECI value.

[0029] In step 404, the magnitude of the BECI is measured for each electrode over a predefined interval. As described above with respect to FIG. 3, in some embodiments, the BECI values ​​collected over the predefined interval or window are stored in memory 126. For example, memory 126 may implement a circular queue in which older measurements are overwritten with newer measurements. In other embodiments, other data structures may be utilized to collect and store the BECI values ​​during the predefined interval. In some embodiments, the duration of the predefined interval is equal to about 1 second, but may be shorter or longer depending on the application.

[0030] In step 406, a contact variable D is calculated based on the baseline BECI magnitude, the current BECI measurement, and Peak to Peak is calculated for each electrode based on a combination of BECI measurements. Peak to Peak The BECI measurement is the difference between the maximum and minimum BECI values ​​collected during a given interval. As mentioned above, in some embodiments, Peak to Peak BECI measurements increase Peak to Peak a BECI measurement, and if the BECI measurement decreases in amplitude during a predetermined interval, Peak to Peak The BECI measurement will be zero regardless of the difference between the maximum and minimum BECI values ​​during a given interval.

[0031] In the embodiment shown in FIG. 4, the contact variable D is calculated as in Equation 1:

number

[0032] At step 408, the contact variable D is compared to one or more thresholds to determine a contact state for each of the multiple electrodes. In some embodiments, only a single threshold is necessary. If the contact variable D is less than the threshold, the electrode is assigned a status of "no contact." If the contact variable D is greater than the threshold, the electrode is assigned a status of "in contact." Typically, the threshold is greater than "1" and may vary based on the type of device (or type of electrode) being analyzed. In other embodiments, multiple thresholds may be utilized, each threshold indicating a different level of contact. For example, in some embodiments, the contact variable D is compared to a first threshold T 1 If the contact variable D is greater than the first threshold, the electrode is assigned a status of "no contact". If the contact variable D is greater than the first threshold, the electrode is assigned a status of "intermittent contact" and if the contact variable D is greater than the second threshold T 2 If it is greater, then the electrode is assigned an "in contact" status. In other embodiments, additional thresholds may be utilized to further delineate various stages of contact between the electrode and the tissue.

[0033] At step 410, a contact status is displayed for each of the multiple electrodes. In some embodiments, the display may include coloring the electrodes based on the assigned contact status. In other embodiments, various other means of indicating the contact status of each electrode may be utilized. In some embodiments, the contact status is displayed as a running average of the contact variable D over a predetermined number of samples. For example, in some embodiments, the contact variable D is averaged over 25 samples (e.g., 1 second) to smooth out sudden changes in the contact variable D. In some embodiments, the number of samples used to average the contact variable can be varied. For example, a smaller number of samples may make the contact variable more responsive (at the expense of more jitter in the contact variable) and a larger number of samples may provide a more stable contact assessment, but at the expense of slower responsiveness to changes in contact status.

[0034] FIG. 5 is a graph showing a BECI baseline value, a measured BECI value, and Peak to Peak 5 is a flow chart showing the steps utilized to determine a contact condition based on a combination of BECI values. In step 502, a baseline bipolar impedance Complex An impedance (BECI) value is calculated for each electrode. As described above, in some embodiments, a baseline BECI value for each electrode is determined by monitoring the BECI values ​​associated with the electrode over a collection period and selecting the minimum value as the baseline BECI value. In some embodiments, the BECI values ​​are filtered so that momentary contact between electrodes that results in an abnormally low BECI value is not utilized as the baseline BECI value.

[0035] At step 504, the magnitude of the BECI is measured for each electrode over a predefined interval. As described above with respect to Figures 3 and 4, in some embodiments, the BECI values ​​collected over the predefined interval or window are stored in memory 126. For example, memory 126 may implement a circular queue in which older measurements are overwritten with newer measurements. In other embodiments, other data structures may be utilized to collect and store the BECI values ​​during the predefined interval. In some embodiments, the duration of the predefined interval is equal to about 1 second, but may be shorter or longer depending on the application.

[0036] In step 506, for each new measured BECI magnitude M, a minimum BECI value M min But the past W M In some embodiments, sample W is selected from the sample M The number of samples W corresponds to the length of the predetermined interval. M The number of is independent of the given interval.

[0037] In step 508, the minimum BECI value M min is the threshold T Mwhere T M is M min represents a value below which "firm contact" is absolutely prohibited. As a result, the comparison in step 508 is M The BECI value measured in the sample was compared with the past W M Determine whether a value indicating that the electrode was not in "good contact" with the tissue was assigned during any sample of the minimum BECI value M min is the threshold T M If so, in step 510 the BECI value M N is calculated based on the following formula:

number

number

[0038] In step 514, Peak to Peak The BECI value PP is the threshold PP G Compared with PP G teeth Peak to Peak This is the value below which "no contact" is absolutely certain. Peak to Peak BECI value PP is threshold PP G Less than and measured Peak to Peak If the BECI value indicates no contact, then in step 516 the contact value D is set to M N The minimum value and threshold T1 Thus, Peak to Peak If the value PP indicates that contact is unlikely, the contact value D is set to a threshold T 1 is assigned an upper bound defined by T 1 A contact value D less than indicates no contact.

[0039] Peak to Peak Value PP is PP G If so, then in step 518, Peak to Peak The value PP is the threshold PP F is compared with the threshold value PP F is the PP value above which "no contact" is absolutely prohibited or impossible (i.e., indicating at least intermittent contact with tissue). Peak to Peak value). Peak to Peak The value PP is the threshold PP F If so, then in step 520, the contact value D is set to the BECI value M N and threshold T 1 is assigned. In this way, Peak to Peak If the value PP indicates that there is at least some possibility of contact, the contact value D is set to a value greater than or equal to the threshold T 1 (i.e., the contact value D is constrained by a floor defined by the threshold T 1 (It is not possible to assign a lower value), and at least T 1 A contact value D of indicates at least some intermittent contact.

[0040] Peak to Peak The value PP is set to the threshold value PP G is greater than the threshold value PP F If it is less than Peak to Peak With the value PP indicating no specific contact or no specific contact, in step 522 the contact value D is assigned a value based on the formula:

number

number

[0041] Thus, the term α is the threshold PP G , P.P. F for Peak to Peak It represents the size of the BECI. For example, Peak to Peak The value PP is the upper threshold PP F When α is approximately equal to α, the value of α approaches 1 and the term max(M N ,T 1 )" and the second term "min(M N ,T 1 )" to reduce the impact of Peak to Peak The value PP is the lower threshold PP G When the value of α is close to 0, the second term, min(M N ,T 1 )" while increasing the influence of the first term "max(M N ,T 1 )" to reduce the impact of

[0042] In step 524, the contact value D is equal to or smaller than the threshold T 1 , T 2 and the contact state is determined (for example, D <T 1 = no contact, D ≤ T 2 = intermittent contact, D>T 2 = firm contact).

[0043] At step 526, a contact status is displayed for each of the plurality of electrodes. As discussed above, in some embodiments, the display may include coloring the electrodes based on the assigned contact status. In other embodiments, various other means of indicating the contact status of each electrode may be utilized. In some embodiments, the contact status is displayed as a running average of the contact variable D over a predetermined number of samples. For example, in some embodiments, the contact variable D is averaged over 25 samples (e.g., 1 second) to smooth out sudden fluctuations in the contact variable D. In some embodiments, the number of samples used to average the contact variable can be varied. For example, a smaller number of samples may make the contact variable more responsive (at the expense of more jitter in the contact variable) and a larger number of samples may provide a more stable contact assessment, but at the expense of slower responsiveness to changes in contact status.

[0044] FIG. 6 illustrates the excitation of a bipolar pair of electrodes and the resulting ComplexFIG. 1 is a circuit diagram illustrating circuit elements utilized to measure impedance. In particular, the circuit diagram includes a signal source 120 (shown in FIG. 1), a pair of electrodes 204a, 204b (shown in FIG. 2), first and second operational amplifiers 602a, 602b, and an ECU 118 (also shown in FIG. 1). In some embodiments, the signal source 120 generates an excitation signal that is provided to the first and second electrodes 204a, 204b. The first operational amplifier 602a includes a first terminal (e.g., a positive terminal) connected to the first electrode 204a and a second terminal (e.g., a negative terminal) connected to a reference electrode 105 (e.g., a surface electrode). The output of the operational amplifier 602a reflects the difference in voltage between the first electrode 204a and the reference electrode 105. The second op-amp 602b includes a first terminal (e.g., a positive terminal) connected to the second electrode 204b and a second terminal (e.g., a negative terminal) connected to the reference electrode 105 (e.g., a surface electrode). The output of the op-amp 602b reflects the difference in voltage between the second electrode 204b and the reference electrode 105. The outputs of the first op-amp 602a and the second op-amp 602b are provided to the ECU 118, which uses the respective measurements to calculate the bipolar electrode Complex Determine impedance (BECI).

[0045] 7 is a top view of a grid array catheter 700. In some embodiments, the grid array catheter 700 comprises a shaft 702, shaft electrodes 704a and 704b, a proximal end 706, a number of splines 708a, 708b, 708c, 708d, a distal end 710, and a number of spline electrodes 712. In some embodiments, a bipolar electrode Complex Impedance measurements may be taken between any pair of adjacent electrodes. For example, BECI measurements may be taken between shaft electrodes 704a, 704b. In other embodiments, BECI measurements may be taken between any pair of spline electrodes 712, and methods described with respect to Figures 3-5 may be utilized to assess contact or proximity of multiple electrodes 704, 712 to adjacent tissue.

[0046] FIG. 8 is an isometric view of a basket catheter 800. In some embodiments, the basket catheter 800 comprises a shaft 802, a proximal end 804, a distal end 806, and a plurality of splines 810a-810f extending between the proximal end 804 and the distal end 806. Each of the plurality of splines 810a-810f includes a corresponding electrode 812a-812f. In some embodiments, BECI measurements may be measured between a pair of adjacent electrodes, such as between electrode 812a and electrode 812b, or between electrode 812c and electrode 812d, and the methods described with respect to FIGS. 3-5 may be utilized to assess the contact or proximity of each of the electrodes to adjacent tissue.

[0047] Although the invention has been described with reference to exemplary embodiments, those skilled in the art will recognize that various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is not intended that the invention be limited to the particular embodiments disclosed, but it is intended to include all embodiments falling within the scope of the appended claims.

[0048] Consideration of possible embodiments The following is a non-exclusive description of possible embodiments of the present invention.

[0049] According to some aspects, a method for determining an electrode contact state includes applying a drive signal between an electrode pair and measuring, over a collection period, a bipolar electrode current generated in response to the drive signal. Complex The method further includes measuring impedance (BECI) values ​​and determining a baseline BECI value representing a minimum value measured during a collection period. The method further includes applying a drive signal between the electrode pair for a predetermined interval, measuring BECI values ​​generated in response to the drive signal, and determining a baseline BECI value associated with the BECI values ​​measured over the predetermined interval. Peak to Peakvalues ​​and compare baseline BECI values, measured BECI values, and values ​​related to measured BECI values. Peak to Peak Determining the contact state of the electrodes by determining the contact state based on the combination of values.

[0050] The method of the preceding paragraph may optionally additionally and / or alternatively include any one or more of the following features, steps, structures, and / or additional components.

[0051] For example, the BECI value may include a real portion and a quadrature portion, and may include a baseline BECI value, a measured BECI value, and Peak to Peak All values ​​represent the magnitude of the BECI value.

[0052] Determining a baseline BECI value representing the minimum value measured during the collection period may include applying a filter to the measured BECI values ​​to filter out spurious minima due to contact with other electrodes.

[0053] Related to the BECI values ​​measured over a given interval Peak to Peak Measuring the value may include calculating a maximum positive deviation of the measured BECI values ​​over a predetermined interval.

[0054] Baseline BECI values, measured BECI values, and Peak to Peak Determining the contact state based on the combination of values ​​further includes calculating a ratio value representing a ratio of the measured BECI value to a baseline BECI value, and determining whether the ratio value or Peak to Peak Scale at least one of the values ​​to obtain a ratio value and Peak to Peak To enable comparison of values ​​and the scaled ratio values Peak to Peak This may include defining a variable as a maximum value and comparing the variable to one or more thresholds to determine a touch condition.

[0055] Baseline BECI values, measured BECI values, and Peak to Peak Determining the contact state based on a combination of values ​​is

number

[0056] The method further includes comparing the contact variable to one or more thresholds to determine a contact state, where if the contact variable is less than a first threshold a "no contact" state is assigned, if the contact variable is greater than the first threshold and less than a second threshold a "intermittent contact" state is assigned, and if the contact variable is greater than the second threshold a "good contact" state is assigned.

[0057] According to another aspect, a system for use with a medical device configured for insertion into a patient includes a signal generator configured to apply a drive signal to one or more pairs of electrodes disposed on the medical device, a measurement circuit configured to measure a response of the electrode pairs to the drive signal, and a contact assessment module. The contact assessment module comprises a bipolar electrode for each of the electrode pairs. Complex Generate impedance (BECI) values ​​and determine a baseline BECI value representing the minimum BECI value measured during a collection period, subsequently measuring BECI values ​​generated in response to the applied drive signal over a predetermined interval, and determining a time series associated with the BECI values ​​measured over the predetermined interval. Peak to Peak values ​​and compare baseline BECI values, measured BECI values, and values ​​related to measured BECI values. Peak to Peak and determining a contact condition based on a combination of the values. The system further comprises a display for indicating a proximity of the electrode to the tissue based on the output received from the contact assessment module.

[0058] The system of the preceding paragraph may additionally and / or alternatively optionally include any one or more of the following features, configurations, and / or additional components.

[0059] For example, the contact assessment module may determine a baseline BECI value that represents the minimum value measured during a collection period by applying a filter to the measured BECI values ​​to filter out false minima due to contact with other electrodes.

[0060] The contact assessment module calculates the maximum positive deviation of the BECI values ​​measured over a given interval. Peak to Peak The value may be measured.

[0061] The contact assessment module calculates a ratio value that represents the ratio of the measured BECI value to the baseline BECI value, and Peak to Peak To allow comparison with BECI values, ratio values ​​or Peak to Peak Scaling at least one of the BECI values ​​and the scaled ratio value and Peak to Peak The baseline BECI value, the measured BECI value, and the BECI threshold value are calculated by comparing the variable to one or more threshold values ​​to determine the contact state. Peak to Peak The contact state may be determined based on a combination of values.

[0062] The contact evaluation module is

number

[0063] The contact assessment module may compare the contact variable D to one or more thresholds to determine the contact state, where if the contact variable is less than a first threshold a “no contact” state is assigned, if the contact variable is greater than the first threshold and less than a second threshold a “intermittent contact” state is assigned, and if the contact variable is greater than the second threshold a “good contact” state is assigned.

[0064] According to another aspect, a contact assessment system for determining a contact status of an electrode included as part of an electrode pair located at a distal end of a medical instrument includes an input configured to receive collected signals in response to a source signal applied to the electrode pair, and a processor configured to operate in executing specific program instructions stored in a computer readable storage medium. Execution of the specific program instructions causes the processor to determine a contact status of a bipolar electrode based on the input signals received during a collection period. Complex The contact condition is determined by calculating impedance (BECI) values ​​and determining a baseline BECI value representing the minimum value measured during a collection period, and then applying a drive signal between the electrode pair for a predetermined interval. The processor measures the BECI values ​​generated in response to the applied drive signal for the predetermined interval, and generates a BECI associated with the BECI values ​​measured over the predetermined interval. Peak to Peak values ​​and compare baseline BECI values, measured BECI values, and values ​​related to measured BECI values. Peak to Peak A combination of values ​​is used to determine the contact state of the electrodes.

[0065] The contact assessment system of the preceding paragraph may optionally additionally and / or alternatively include any one or more of the following features, configurations, and / or additional components.

[0066] For example, the processor may output the determined contact state to a display.

[0067] The step of determining a baseline BECI value representing the minimum value measured during the collection period may further include applying a filter to the measured BECI values ​​to filter out false minimum values ​​due to contact with other electrodes.

[0068] Related to the BECI values ​​measured over a given interval Peak to Peak The step of measuring the BECI value may further include calculating a maximum positive deviation in the measured BECI value over a predetermined interval.

[0069] Baseline BECI values, measured BECI values, and Peak to Peak The step of determining the contact state based on the combination of values ​​includes calculating a ratio value representing a ratio of the measured BECI value to a baseline BECI value, and Peak to Peak Scale at least one of the BECI values ​​to obtain the ratio value and Peak to Peak To enable comparison with BECI values ​​and the scaled ratio values Peak to Peak The method may further include defining the variable as a maximum value and comparing the variable to one or more thresholds to determine a touch condition.

[0070] Baseline BECI values, measured BECI values, and Peak to Peak The step of determining a contact state based on a combination of values ​​includes:

number

[0071] The contact variable may be compared to one or more thresholds to determine a contact state: if the contact variable is less than a first threshold, a "no contact" status is assigned; if the contact variable is greater than the first threshold and less than a second threshold, an "intermittent contact" status is assigned; and if greater than the second threshold, a "good contact" status is assigned.

Claims

1. 1. A method of operating a system for determining electrode contact status, comprising: The system further comprises: applying a drive signal between the electrode pair; measuring bipolar electrode complex impedance (BECI) values ​​generated in response to said drive signals over a collection period; determining a baseline BECI value that represents the minimum value measured during said collection period; The contact state is applying a drive signal between the electrode pair for a predetermined interval; measuring a BECI value generated in response to the drive signal; measuring a peak-to-peak value associated with the BECI values ​​measured over the predetermined interval; determining the contact condition based on a combination of the baseline BECI value, the measured BECI value, and the peak-to-peak value associated with the measured BECI value; A method of operating the system, comprising:

2. 2. The method of claim 1, wherein the BECI value includes a real portion and a quadrature portion, and the baseline BECI value, the measured BECI value, and the peak-to-peak value all represent a magnitude of the BECI value.

3. A method of operating the system described in claim 1, wherein the system determining a baseline BECI value representing the minimum value measured during the collection period includes applying a filter to the measured BECI value to filter out spurious minimum values ​​due to contact with other electrodes.

4. The system, Measuring a peak-to-peak value associated with the BECI values ​​measured over the predetermined interval comprises: calculating a maximum positive deviation of the BECI values ​​measured over said predetermined interval; A method for operating the system of claim 1.

5. The system, Determining a contact condition based on a combination of the baseline BECI value, the measured BECI value, and the peak-to-peak value further comprises: calculating a ratio value representing a ratio of the measured BECI value to the baseline BECI value; scaling at least one of the ratio value or the peak-to-peak value to allow comparison of the ratio value and the peak-to-peak value; defining a variable as the maximum of said ratio value so scaled and said peak-to-peak value; comparing said variables to one or more thresholds to determine a touch condition; A method of operating the system of claim 1 comprising:

6. The system, Determining a contact condition based on a combination of the baseline BECI value, the measured BECI value, and the peak-to-peak value includes: and applying where D is the contact variable, M is the measured BECI value, and M Ｂ is the baseline BECI value, PP is the peak-to-peak value calculated during the given interval, and PP Ｃ is the upper limit or maximum peak-to-peak BECI measurement, and S Ｖ is the peak-to-peak BECI measurement M / M Ｂ 2. The method of claim 1, wherein the scaling variables are selected for appropriate scaling into a reference frame of ratios defined by:

7. A method of operating the system described in claim 6, wherein the system determines the contact state by comparing the contact variable with one or more thresholds, and if the contact variable is less than a first threshold, a "no contact" state is assigned, if the contact variable is greater than the first threshold and less than a second threshold, an "intermittent contact" state is assigned, and if the contact variable is greater than the second threshold, a "good contact" state is assigned.

8. 1. A system for use with a medical device configured for insertion into a patient, comprising: a signal generator configured to apply a drive signal to one or more pairs of electrodes disposed on the medical device; a measurement circuit configured to measure a response of the electrode pair to the drive signal; a contact assessment module configured to generate a bipolar electrode complex impedance (BECI) value for each of the electrode pairs, determine a baseline BECI value representing a minimum BECI value measured during a collection period, subsequently measure BECI values ​​generated in response to the applied drive signal over a predetermined interval, measure a peak-to-peak value associated with the BECI values ​​measured over the predetermined interval, and determine a contact condition based on a combination of the baseline BECI value, the measured BECI values, and the peak-to-peak value associated with the measured BECI values; a display for indicating the proximity of the electrodes to tissue based on output received from the contact assessment module; A system comprising:

9. 10. The system of claim 8, wherein the contact assessment module determines a baseline BECI value representing the minimum value measured during the collection period by applying a filter to the measured BECI value to filter out false minima due to contact with other electrodes.

10. The system of claim 8 , wherein the contact assessment module measures the peak-to-peak value by calculating the maximum positive deviation of the BECI values ​​measured over the predetermined interval.

11. The contact assessment module includes: calculating a ratio value representing the ratio of the measured BECI value to the baseline BECI value; scaling at least one of the ratio value or the peak-to-peak BECI value to enable comparison of the ratio value with a peak-to-peak BECI value; defining a variable as the maximum of said ratio value and said peak-to-peak value so scaled; Comparing the variables to one or more thresholds to determine a contact state; The system of claim 8 , wherein the contact condition is determined based on a combination of the baseline BECI value, the measured BECI value, and the peak-to-peak value.

12. The contact assessment module includes: where D is a contact variable, M is the measured BECI value, and M Ｂ is the baseline BECI value, PP is the peak-to-peak value calculated during the given interval, and PP Ｃ is the upper limit or maximum peak-to-peak BECI measurement, and S Ｖ is the peak-to-peak BECI measurement value M / M Ｂ 9. The system of claim 8, wherein the scaling variables are selected for appropriate scaling into a reference frame of a ratio defined by:

13. 13. The system of claim 12, wherein the contact assessment module compares the contact variable D to one or more thresholds to determine the contact state, and assigns a "no contact" state if the contact variable D is less than a first threshold, an "intermittent contact" state if the contact variable is greater than the first threshold and less than a second threshold, and a "good contact" state if the contact variable is greater than the second threshold.

14. 1. A contact assessment system for determining a contact status of an electrode included as part of an electrode pair located at a distal end of a medical instrument, the system comprising: an input configured to receive signals collected in response to a source signal applied to the electrode pair; A processor, when executing specific program instructions stored on a computer-readable storage medium, Calculating a bipolar electrode complex impedance (BECI) value based on the input signals received during the acquisition period; determining a baseline BECI value that represents the minimum value measured during said collection period; a processor configured to determine a contact condition by then applying a drive signal between the electrode pair for a predetermined interval, measuring a BECI value generated in response to the drive signal applied for the predetermined interval, measuring a peak-to-peak value associated with the BECI value measured over the predetermined interval, and determining the contact condition of the electrodes using a combination of the baseline BECI value, the measured BECI value, and the peak-to-peak value associated with the measured BECI value; A system comprising:

15. The system of claim 14 , wherein the processor outputs the determined contact condition to a display.

16. 15. The system of claim 14, wherein determining a baseline BECI value representing a minimum value measured during the collection period further comprises applying a filter to the measured BECI value to filter out spurious minimum values ​​due to contact with other electrodes.

17. 15. The system of claim 14, wherein the step of measuring a peak-to-peak BECI value associated with the BECI values ​​measured over the predetermined interval further comprises calculating a maximum positive deviation in the BECI values ​​measured over the predetermined interval.

18. determining a contact condition based on a combination of the baseline BECI value, the measured BECI value, and the peak-to-peak value, calculating a ratio value representing a ratio of the measured BECI value to the baseline BECI value; scaling at least one of the ratio value or the peak-to-peak BECI value to permit comparison of the ratio value with the peak-to-peak BECI value; defining a variable as the maximum of said ratio value so scaled and said peak-to-peak value; comparing said variables to one or more thresholds to determine a touch condition; The system of claim 14 further comprising:

19. Determining a contact state based on a combination of the baseline BECI value, the measured BECI value, and the peak-to-peak value, where D is a contact variable, M is the measured BECI value, and M Ｂ is the baseline BECI value, PP is the peak-to-peak value calculated during the given interval, and PP Ｃ is the upper limit or maximum peak-to-peak BECI measurement, and S Ｖ is the peak-to-peak BECI measurement value M / M Ｂ 15. The system of claim 14, wherein the scaling variables are selected for appropriate scaling into a reference frame of ratios defined by:

20. 20. The system of claim 19, wherein the contact variable is compared to one or more thresholds to determine the contact state, and if the contact variable is less than a first threshold, a "no contact" status is assigned, if the contact variable is greater than the first threshold and less than a second threshold, an "intermittent contact" status is assigned, and if the contact variable is greater than the second threshold, a "good contact" status is assigned.

Images