WO2017007018A1

WO2017007018A1 - Nerve detecting device, and nerve detecting method

Info

Publication number: WO2017007018A1
Application number: PCT/JP2016/070275
Authority: WO
Inventors: 徹中野; 清水　一夫
Original assignee: 国立大学法人東北大学; 日本ＳＲｉ株式会社
Priority date: 2015-07-08
Filing date: 2016-07-08
Publication date: 2017-01-12
Also published as: JP6830310B2; JP2017018197A

Abstract

The objective of the present invention is to provide a nerve detecting device and a nerve detecting method with which it is possible for nerves to be suitably detected. This nerve detecting device is provided with: a means for generating a stimulation signal having a characteristic pattern; a stimulation means for imparting stimulation based on the stimulation signal to a nerve; a first detecting means for detecting a magnetic field that is generated around the nerve concomitantly with the transmission of stimulation through the nerve; and a second detecting means for detecting a detection signal corresponding to the characteristic pattern, on the basis of the measured signal corresponding to the magnetic field.

Description

Nerve detection device and nerve detection method

Some embodiments according to the present invention relate to a nerve detection device and a nerve detection method.

When performing surgery in humans or animals, it is preferable to specify the position and function of the nerve in advance and take care not to damage the nerve. For example, if the recurrent nerve is injured during surgery for esophageal cancer, vocal cord paralysis occurs, and symptoms such as hoarseness and aspiration occur. In other words, if the nerve and its function cannot be identified and the patient hurts, another symptom may be caused by treatment of the chief complaint. However, since the running of each nerve in humans or animals varies depending on the individual, it is not easy to specify the position of the nerve and the type of nerve found.

Conventionally, as one of the methods for specifying a nerve, there is a method of observing whether or not a reflection occurs in a target organ related to the nerve after applying an electrical stimulus by bringing an electrode probe into contact with the nerve. is there. Moreover, although it is not for detecting nerves, Non-Patent Document 1 and the like disclose research relating to nerve functions and the like.

In the technique of stimulating nerves with an electrode probe, it is necessary for a human to observe the reflection of the target organ and determine the presence or absence of the reflection. However, the surgeon cannot fully identify the function of the nerve because the target organ does not respond sufficiently because the level of stimulation applied to the nerve is low or the judgment of the presence or absence of reflexes is wrong. In some cases.

Some aspects of the present invention have been made in view of the above-described problems, and an object thereof is to provide a nerve detection device and a nerve detection method capable of suitably detecting a nerve.

One nerve detection device according to the present invention includes a means for generating a stimulation signal having a characteristic pattern, a stimulation means for giving a stimulation based on the stimulation signal to a nerve, and the nerve surroundings in accordance with the transmission of the stimulation in the nerve. First detecting means for detecting an electromagnetic field generated in the first and second detecting means for detecting a detection signal corresponding to the feature pattern based on a measurement signal corresponding to the electromagnetic field.

One nerve detection device according to the present invention detects means for generating a stimulation signal having a characteristic pattern, stimulation means for applying a stimulation based on the stimulation signal to the nerve, and an electrical signal accompanying the transmission of the stimulation in the nerve. First detection means and second detection means for detecting a detection signal corresponding to the feature pattern based on a measurement signal corresponding to the electrical signal.

One nerve detection method according to the present invention includes a step of generating a stimulus signal having a characteristic pattern, a step of giving a stimulus based on the stimulus signal to a nerve, and transmission of the stimulus in the nerve, around the nerve The apparatus performs a step of detecting the generated electromagnetic field and a step of detecting a detection signal corresponding to the feature pattern based on a measurement signal corresponding to the electromagnetic field.

One nerve detection method according to the present invention includes a step of generating a stimulus signal having a characteristic pattern, a step of giving a stimulus based on the stimulus signal to a nerve, and a step of detecting an electrical signal accompanying the transmission of the stimulus in the nerve And a step of detecting a detection signal corresponding to the feature pattern based on the measurement signal corresponding to the electrical signal.

In the present invention, “part”, “means”, “apparatus”, and “system” do not simply mean physical means, but “part”, “means”, “apparatus”, “system”. This includes the case where the functions possessed by "are realized by software. Further, even if the functions of one “unit”, “means”, “apparatus”, and “system” are realized by two or more physical means or devices, two or more “parts” or “means”, The functions of “device” and “system” may be realized by a single physical means or device.

It is a figure for demonstrating the nerve search method which concerns on embodiment. It is a figure which shows the position of the magnetic sensor arrange | positioned in the nerve periphery in the nerve search method which concerns on embodiment. It is a figure which shows the specific example of the signal waveform which concerns on the nerve detection apparatus which concerns on embodiment. It is a figure which shows the function structure of the nerve detection apparatus which concerns on embodiment.

Embodiments of the present invention will be described below. In the following description and the description of the drawings to be referred to, the same or similar components are denoted by the same or similar reference numerals.

1. Outline When performing surgery in humans or animals, it is preferable to consider the position and function of a nerve in advance and take care not to damage the nerve. For example, if the recurrent nerve is injured during surgery for esophageal cancer, vocal cord paralysis occurs, and symptoms such as hoarseness and aspiration occur. In other words, if the nerve and its function cannot be identified and the patient hurts, another symptom may be caused by treatment of the chief complaint. However, since the running of each nerve in humans or animals has individual differences, it is difficult to identify the position, function, and state of the nerve at first glance.

As one of the methods for identifying the function or damage of a nerve, the electrode probe is brought into contact with the nerve and electrically stimulated, and then whether or not the reflection of the target organ related to the nerve has occurred is observed. A method can be considered. However, in the technique of stimulating nerves with an electrode probe, the human operator himself / herself must determine whether or not the target organ is reflexed. In this case, there is a case where the target organ does not respond sufficiently because the level of stimulation applied to the nerve is low, or the function of the nerve or the like cannot be specified sufficiently by misjudging the presence or absence of reflexes.

In order to give an electrical stimulus to a nerve, first, the position of the nerve is specified, and after the specified nerve is exposed from a tissue such as fat protecting the nerve, an electrode probe is applied to the nerve. There is a need. However, as described above, it is never easy to specify a nerve, and the nerve may be damaged in the process of exposure.

Furthermore, since an electrical signal is also used in electrocardiogram monitors and surgical instruments such as an electric scalpel, if an electrode probe is used during nerve detection, the electrical signal applied by the electrode probe interferes with the electrocardiogram monitor or electric scalpel, and these Affects the equipment. That is, there is a problem that surgical devices such as an electrocardiogram monitor and an electric scalpel and nerve detection using an electrode probe cannot be performed simultaneously.

Therefore, in the nerve detection device according to the present embodiment, an artificial stimulus having a specific feature pattern having a feature such as a period is given to the nerve by magnetism, and the stimulus is applied to the electric field generated around the nerve and / or Alternatively, it is detected as a magnetic field (hereinafter simply referred to as an electromagnetic field). Accordingly, it is possible to determine the presence / absence of nerve detection, the relative distance from the nerve, and the like by signal processing of a detection signal obtained as a result of detecting the electromagnetic field. Further, it is possible to search for nerves in a state where nerves are covered with surrounding tissues, and to preserve nerve functions.

Hereinafter, a specific example of the nerve detection method according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram for explaining a technique for searching for the recurrent nerve 19. Here, a technique for searching for the recurrent nerve 19 during esophagectomy in an endoscopic operation will be mainly described. However, the nerve to be searched is not limited to the recurrent nerve 19. For example, a similar nerve detection method may be applied to searching for a nerve such as a urinary nerve.

First, the structure of the human body 10 from the neck to the chest will be briefly described. The left common carotid artery 13A and the right common carotid artery 13B (hereinafter collectively referred to as the common carotid artery 13) pass through the inside of the cervical skin 11, and these left common carotid artery 13A and right common carotid artery 13B are Connected to the aortic arch 15. Further, the left vagus nerve 17A and the right vagus nerve 17B (hereinafter collectively referred to as the vagus nerve 17) run along the left common carotid artery 13A and the right common carotid artery 13B inside the skin 11 of the neck. ing. The vagus nerve 17 is a basic parasympathetic nerve that passes from the brain through the neck to the chest. The left vagus nerve 17A and the right vagus nerve 17B branch into the left recurrent nerve 19A and the right recurrent nerve 19B (hereinafter collectively referred to as the recurrent nerve 19) in the thoracic cavity, respectively. The recurrent nerve 19 extends along the trachea 21 and the esophagus toward the thyroid cartilage 23 and reaches the vocal cord muscle 25.

Here, the common carotid artery 13 runs directly under the skin 11 of the neck, and the position can be easily determined by palpation or the like. Therefore, the position of the vagus nerve 17 that travels along the common carotid artery 13 can also be easily identified. In the present embodiment, an artificial signal generated by a stimulation signal having a specific feature pattern without contact with the vagus nerve 17 that travels directly under the skin 11 by magnetic means using the magnetic stimulation probe 110. Give a stimulus. Here, the case where the stimulus signal having the characteristic pattern is a pulse signal having a constant cycle, which is periodically switched ON / OFF, will be described. In magnetic stimulation for the vagus nerve 17, a magnetic flux density of about 0.1 to 2.0 T is required. The stimulus given to the vagus nerve 17 is transmitted to the peripheral side of the vagus nerve 17 by jump conduction described later, and further transmitted to the recurrent nerve 19 branched from the vagus nerve 17.

Note that the nerve stimulation method is not limited to magnetic stimulation, and a method of giving an electrical signal to the nerve is also conceivable. In this case, for example, the vagus nerve 17 that travels in the vicinity of the common carotid artery 13 is exposed after the neck is incised, and the vagus nerve 17 is brought into contact with an electrode probe by a bipolar electrode or a monopolar electrode. Stimulate it. When bipolar electrodes are used, the vagus nerve 17 can be stimulated by applying a pulse voltage of about 0.1 to 5 V between the bipolar electrodes. The voltage value / current value suitable for stimulation of the vagus nerve 17 varies depending on the distance between electrodes contacting the nerve, the electrode size, the contact state with the living body, and the like. Note that a technique for electrically stimulating nerves will be briefly described in modified examples and the like described later.

As described above, in this embodiment, the vagus nerve 17 is magnetically stimulated, and the recurrent nerve 19 is searched for by detecting an electromagnetic field corresponding to the stimulation. Here, the vagus nerve 17 is a parasympathetic nerve, and the excitement of the parasympathetic nerve causes a decrease in heart rate, a decrease in blood pressure, an increase in gastrointestinal function, an increase in exocrine secretion, relaxation of active muscles, contraction of bladder smooth muscle, miosis, and the like. . That is, if the stimulation to the vagus nerve 17, which is a parasympathetic nerve, is too great, it may hinder life maintenance, and thus it is necessary to keep the stimulation as low as possible. Therefore, prior to searching for the vagus nerve 17, it is necessary to adjust the intensity of the stimulation signal for applying a magnetic stimulus to the vagus nerve 17.

Therefore, first, the vagus nerve 17 is magnetically stimulated on the head side of the subclavian artery, and the heartbeat response due to the nerve stimulation is confirmed. When the vagus nerve 17 is stimulated to a certain degree or more, a heart rate drop occurs according to the stimulus, and by observing the heart rate response, the stimulation level that is the minimum threshold value at which the heart rate reduction occurs can be specified. As a result, it is possible to confirm an appropriate level of the stimulus signal used when searching for the recurrent nerve 19. Such a threshold stimulation level may be automatically specified by a nerve detection device that detects a heartbeat from a sensor or the like, or specified by an operator inputting an operation while confirming the heartbeat on an electrocardiogram monitor or the like. May be.

In order to suppress the effects of neural stimulation, that is, to reduce the energy applied to the nerve, a method of reducing the pulse level of the pulse signal included in the stimulation signal is considered in addition to the method of suppressing the stimulation level of the stimulation signal described above. It is done. Therefore, it is necessary to predetermine a suitable pulse width of the pulse signal included in the stimulation signal. Specifically, for example, the initial value of the pulse width is set to 1 msec, and it is confirmed whether or not a heart rate decrease occurs at the pulse width and the previously specified neural stimulation level. As a result, if a decrease in heart rate is observed, the pulse width is reduced by 0.1 msec. By repeating such operations, it is possible to confirm the threshold pulse width which is the shortest pulse width capable of confirming a decrease in heart rate. Such a threshold pulse width may be automatically specified by a nerve detection device that detects a heartbeat from a sensor or the like, or specified by an operator performing operation input while confirming a heartbeat on an electrocardiogram monitor or the like. Also good.

After the threshold values of the stimulation level and the pulse width when the nerve is stimulated in this way are determined, a neural signal including a pulse signal equal to or higher than the threshold stimulation level and the threshold pulse width is searched for the recurrent nerve 19 ( Search). More specifically, the surgeon uses the stimulation signal to stimulate the vagus nerve 17 with the magnetic stimulation probe 110, while magnetizing a region where the recurrent nerve 19 in the human body 10 is estimated to be traveling. Search by the sensor 120. As a result, when an electromagnetic field associated with the transmission of the stimulus based on the stimulus signal is detected by the magnetic sensor 120, it is determined that the recurrent nerve 19 is running in the vicinity of the detection position and the stimulus is transmitted normally. Is done. That is, it is possible to specify the running position of the recurrent nerve 19, the presence or absence of damage to the recurrent nerve 19, and the like only by signal processing. Here, the stimulation level and the pulse width of the pulse signal included in the nerve signal used for nerve stimulation are the same as the threshold value or slightly less because the influence on the human body 10 can be suppressed when the stimulation given to the nerve is as small as possible. It is preferable to make it a value that exceeds.

If the magnetic sensor 120 cannot detect magnetism, it is possible to identify the damaged site by gradually expanding the nerve search range from the stimulation site of the vagus nerve 17 toward the nerve periphery.

Referring to FIG. 2, a method for transmitting a stimulus applied to the nerve 200 will be described. The transmission method is the same for other nerves as long as it is a myelinated nerve including the vagus nerve 17 and the recurrent nerve 19 described above.

The nerve 200 includes an axon 203 and a myelin sheath 205 (myelin sheath) wound around the axon 203 and made of insulating lipid. The length of each myelin sheath 205 is about several millimeters, and between the myelin sheaths 205, a Lambie diaphragm 207 in which the axon 203 is exposed is formed. When a stimulus is applied to the nerve 200, Na + ions move between the inner and outer sides of the cell membrane of the axon 203 in response to the stimulus in the Lambier diaphragm 207, and depolarization occurs. As a result of the depolarization, Na + ions move at the adjacent diaphragm 207. That is, depolarization moves to the adjacent diaphragm 207. By repeating this, depolarization by Na + ions as a stimulation signal moves on the nerve 200. The method of transmitting the stimulus is called jumping conduction. In jump conduction, the movement of the cell membrane potential caused by the movement of Na + ions occurs for each lambier diaphragm that is separated from one or more myelin sheaths 205. Thereby, the movement of the stimulus on the nerve 200 by jumping electric motor has a higher signal transmission speed than other cell tissues such as muscle and fat.

When an electric field is generated around the axon 203 due to the movement of Na + ions, a magnetic field is also generated around the nerve 200. In addition, an electric field is also generated around the nerve 200 in response to depolarization in the Lambier diaphragm 207. The magnetic sensor 120 detects these electromagnetic fields generated around the recurrent nerve 19. As shown in FIG. 2, the magnetic sensor 120 may detect an electromagnetic field generated around the nerve 200 by sequentially moving positions shown as the magnetic sensors 120A to 120C, or may be arranged in an array, for example. As the magnetic sensors 120A to 120C, an electromagnetic field generated around the nerve 200 may be detected. By using the magnetic sensors 120 arranged in a two-dimensional or three-dimensional array, the operator can search a wide range simultaneously. Further, as will be described later, by comparing the detection results of the magnetic sensors 120, it is possible to determine the relative distance from the nerve stimulation position and the relative spatial distance on the nerve path from the nerve 200.

In addition, since a plurality of nerves 200 are running in the human body 10 and signals are transmitted at random, an electromagnetic field accompanying the signal transmission is always generated. There is also geomagnetism generated by the earth. Therefore, the magnetic sensor 130A disposed near the human body 10 and the magnetic sensor 130B disposed at a position away from the nerve 200 in the human body 10 (hereinafter, the

magnetic sensors

130A and 130B are collectively referred to as the magnetic sensor 130). A peripheral electric field and / or a peripheral magnetic field (hereinafter referred to as a peripheral electromagnetic field) is detected from at least one of the above. An electromagnetic stimulus related to a peripheral electromagnetic field detected by the magnetic sensor 130 from an electromagnetic field signal detected by the magnetic sensor 120 after applying an artificial stimulus having a specific characteristic pattern to the nerve 200 by the magnetic stimulation probe 110. By subtracting the field signal, the signal generated based on the artificially applied stimulus can be detected. Further, by using an artificial stimulus having such a specific pattern, it is possible to distinguish it from a signal transmitted from the brain or the like to the nerve 200.

Hereinafter, the stimulation signal given to the nerve 200 and the detected signal will be described with reference to FIG. FIG. 3 is a diagram illustrating a specific example of a signal related to the nerve detection device according to the present embodiment.

First, the nerve detection device generates a periodic signal shown in FIG. In the periodic signal, the High level corresponds to a period during which the nerve 200 is stimulated, and the Low level corresponds to a period during which no stimulation is applied. That is, the stimulation given to the nerve 200 is provided with a period for stimulation and a period for which stimulation is not performed, and the nerve signal becomes a burst signal to which stimulation is intermittently applied. Thus, by providing the period during which the stimulation is applied and the period during which the stimulation is not performed, it is possible to suppress the influence on each organ accompanying the nerve stimulation. For example, the duty ratio in the periodic signal is desirably 50% or less. Generation | occurrence | production of a side effect can be suppressed by making the period which does not stimulate the nerve 200 long as compared with the period which stimulates the nerve 200. Therefore, the period length of this periodic signal can be set, for example, as 100 msec for the period for applying the stimulus and 900 msec for the period for not applying the stimulus.

Here, considering the stimulation of the vagus nerve 17 in particular, if the vagus nerve 17 is stimulated for 5 seconds or more, the heart rate decreases and there is a risk of bradycardia. Therefore, the period for applying the stimulation is 5 seconds or less. It is desirable. When the duty ratio in the periodic signal is 50%, the risk of bradycardia can be reduced by setting the frequency of the periodic signal to 0.1 Hz or more. In particular, the frequency of the periodic signal can be 0.1 Hz or more and 100 Hz or less.

Further, the nerve detection device generates a stimulation signal shown in FIG. 3B based on the periodic signal shown in FIG. More specifically, the stimulus signal is a pulse signal having a constant period when the periodic signal is at a high level, and is a constant level (level zero in FIG. 3B) while the periodic signal is at a low level. By using a stimulation signal having such an artificial feature pattern, it is possible to distinguish a signal given from the brain to the nerve 200 and this stimulation signal.

Here, a pulse signal having a frequency of 1 Hz or more can be used as a stimulation signal having a characteristic pattern for applying stimulation to the nerve 200. In particular, by making the pulse width of the pulse signal sufficiently narrow (to the minimum necessary width), the side effects associated with the applied stimulus can be kept low. However, as described above, the characteristic pattern of the stimulation signal may be a variable frequency pulse with a variable frequency, instead of a single frequency pulse of 1 Hz or higher.

By the way, a signal having a low frequency of 1 kHz or less can be transmitted to other tissues such as muscle and fat. In this respect, the nerve 200 can transmit a high-frequency signal because it transmits a stimulus by jumping conduction at a high speed. Therefore, the pulse signal included in the stimulation signal for stimulating the nerve 200 is about 1 kHz or more that is difficult for other tissues such as muscles to transmit, and about 10 kHz that the myelinated nerve can transmit. The frequency is preferably within the following range. Therefore, for example, the frequency of the pulse signal included in the stimulus signal can be 2.0 kHz (the cycle is 0.5 msec). When the frequency of the pulse signal is 2.0 kHz and the period for applying the stimulus is 100 msec as described above, the pulse signal includes 200 pulses in the period for applying the stimulus.

Here, the stimulation to the nerve 200 using the stimulation signal is detected by a lock-in amplifier (described later). If the number of pulses per unit time included in the stimulus signal is small, the output level of the detection signal output from the lock-in amplifier is lowered, and as a result, the possibility of erroneous detection is increased. On the other hand, if the number of stimulation pulses per unit time included in the stimulation signal is too large, as described above, the influence on each organ to which the vagus nerve 17 is connected becomes large. Therefore, it is necessary to keep the stimulation period as short as possible. is there. As a method of giving a constant number of stimulation pulses per unit time, the number of stimulation pulses included in one cycle (corresponding to the signal cycle in FIG. 3A) is reduced while the time of one cycle is shortened (neural) A method of reducing the period of no stimulation) and a method of increasing the number of stimulation pulses included in one cycle while increasing the time of one cycle (increasing the period of no nerve stimulation) are conceivable. Considering the side effects in the living body, it is preferable to adjust so as to take a long period of time when no continuous nerve stimulation is performed. Therefore, the time for applying and not applying the stimulation pulse signal, and the number of stimulation pulses included in one cycle are not limited to the above-mentioned 100 msec, 900 msec, and 200 pulses, and can be appropriately adjusted. However, considering the above points, when stimulating the vagus nerve 17, for example, the vagus nerve to each organ to which the vagus nerve 17 transmits the stimulation, such as the pharynx, heart, stomach, small intestine, liver and kidney. It is possible to reduce the side effects associated with applying artificial stimulation to 17.

The magnetic stimulation probe 110 magnetically stimulates the nerve 200, for example, using the stimulation signal shown in FIG. The stimulus is transmitted to the nerve 200 by jump conduction. Since jump conduction is non-attenuating transmission, when the stimulation amount exceeds the threshold value for the nerve 200 to transmit the stimulation, the stimulation is transmitted at the same level until extinction.

It should be noted that the nerve 200 does not respond to a certain period of time called the absolute refractory period immediately after the nerve 200 is stimulated, no matter how strong the stimulus is given. Thereby, the stimulus applied during the absolute refractory period is not transmitted because the period of the stimulus signal becomes shorter than the length of the absolute refractory period of the nerve 200. That is, the period of stimulation transmitted by the nerve 200 is always longer than the length of the absolute refractory period.

The magnetic sensor 120 detects an electromagnetic field generated around the nerve 200. As described above, the magnetic sensor 130 detects the peripheral electromagnetic field. With respect to the measurement signal obtained by subtracting the signal of the peripheral electromagnetic field from the signal of the electromagnetic field detected by the magnetic sensor 120 and the reference signal which is the stimulation signal shown in FIG. By performing the processing, the detection signal shown in FIG. 3C can be obtained. Specifically, first, the measurement signal and the reference signal are multiplied while sequentially shifting the phase of the reference signal, which is a bursty signal. A detection signal is obtained by applying a low-pass filter to a reference signal having a phase to which the multiplied value reacts most. When a detection signal equal to or greater than a certain threshold value can be observed, it means that the stimulation signal artificially given to the nerve 200 by the magnetic stimulation probe 110 is detected by the magnetic sensor 120 at the position of the magnetic sensor 120. To do. That is, it can be specified that the nerve 200 is traveling in the vicinity of the magnetic sensor 120.

In the above description, when generating the measurement signal, it has been described that the signal of the peripheral electromagnetic field is subtracted from the signal of the electromagnetic field detected by the magnetic sensor 120. However, the present invention is not limited to this. In particular, when the fluctuation of the surrounding electromagnetic field detected by the magnetic sensor 130 is weak, it is conceivable to use the electromagnetic field signal detected by the magnetic sensor 120 as a measurement signal as it is.

2. Functional Configuration Hereinafter, the functional configuration of the nerve detection device 100 according to the present embodiment will be described with reference to FIG. FIG. 4 is a diagram illustrating a specific example of the configuration of the nerve detection device 100. The nerve detection device 100 includes a periodic signal generator 101, a burst signal generator 103, a stimulation pulse generator 105, a driver 107, a stimulation amount adjustment unit 109, a magnetic stimulation probe 110, a stimulation pulse width adjustment unit 111, a magnetic sensor 120, and a driver. 121, a driver 123, an adder 125, a lock-in amplifier 127, and a determination unit 133.

The periodic signal generator 101 generates a periodic signal whose specific example is shown in FIG. As described above, the periodic signal is for switching ON / OFF whether or not to generate a pulse signal for stimulation that gives stimulation to the nerve 200. By providing a period during which no stimulation signal is applied to the nerve, the amount of stimulation given to the nerve 200 can be suppressed, and as a result, the influence of the nerve 200 on each stimulation transmission destination organ can be kept low.

The burst signal generator 103 generates the stimulation signal illustrated in FIG. 3B based on the periodic signal received from the periodic signal generator 101. The burst signal generator 103 generates pulse signals at regular intervals during a period when the periodic signal is at a high level, and prevents a pulse signal from being generated during a period when the period signal is at a low level. Thereby, the stimulation signal generated by the burst signal generator 103 becomes a burst pulse signal.

The stimulation pulse generator 105 inputs a stimulation signal to the driver 107 so that the magnetic stimulation probe 110 generates magnetism based on the stimulation signal generated by the burst signal generator 103. The driver 107 causes the magnetic stimulation probe 110 to generate magnetism based on the stimulation signal. Here, the magnitude (stimulation level) of magnetism generated by the driver 107 is adjusted by the stimulation amount adjustment unit 109. As described above, it is preferable that the stimulation level is set to a value as low as possible while the heart rate lowers. The pulse width of the pulse signal included in the stimulation signal is adjusted by the stimulation pulse width adjustment unit 111. As described above, it is preferable that the pulse width is set to a value as low as possible while the heart rate decreases.

The magnetic stimulation probe 110 applies magnetic stimulation to the nerve 200 by generating magnetism based on the stimulation signal. The stimulus given to the nerve 200 is transmitted by jump conduction. The magnetic sensor 120 detects an electromagnetic field generated around the nerve 200 according to the jump conduction, and the driver 121 outputs an electrical signal corresponding to the electromagnetic field to the adder 125.

Further, the magnetic sensor 130 detects a peripheral electromagnetic field, and the driver 123 outputs an electrical signal corresponding to the peripheral electromagnetic field to the adder 125. The adder 125 subtracts the electrical signal from the magnetic sensor 130 from the electrical signal from the magnetic sensor 120. As a result, only the measurement signal related to the electromagnetic field generated along with the jump conduction in the nerve 200 excluding the influence of the peripheral electromagnetic field is obtained. This is because both the magnetic sensor 120 and the magnetic sensor 130 are affected by the peripheral electromagnetic field. As described above, if the fluctuation of the electromagnetic field detected by the magnetic sensor 130 is small, it is possible to input the electric signal from the magnetic sensor 120 to the phase sensitive detector 129 without performing the subtraction process by the adder 125. It is done. For example, if the magnetic level detected by the magnetic sensor 120 is several tens of nT and the level of the peripheral magnetic field detected by the magnetic sensor 130 is 45 μT, the level of the peripheral magnetic field is sufficiently small. There is no need to consider the effects of.

The phase sensitive detector 129 and the low-pass filter 131 constitute a lock-in amplifier 127, and the lock-in amplifier 127 outputs a detection signal for detecting a feature pattern of a stimulus signal to be stimulated by the magnetic stimulation probe 110. This makes it possible to distinguish between a signal that is randomly transmitted from the brain or the like to the nerve 200 and a signal that corresponds to the artificially applied stimulus. For example, if the stimulus artificially applied to the nerve 200 is 2.0 kHz, the lock-in amplifier 127 outputs a detection signal for determining whether or not a 2.0 kHz signal component is included in the measurement signal. To do. If the measurement signal includes a signal component of 2.0 kHz, which is an artificially added frequency band, the nerve 200 stimulated by the magnetic stimulation probe 110 travels in the vicinity of the magnetic sensor 120. You can see that

The phase-sensitive detector 129 that constitutes a part of the lock-in amplifier 127 multiplies the stimulation signal that is the reference signal input from the burst signal generator 103 and the measurement signal output from the adder 125. When the stimulation pulse signal included in the stimulation signal is 2.0 kHz, the 2.0 kHz stimulation pulse signal is input to the phase sensitive detector 129 as a reference signal. Furthermore, the phase sensitive detector 129 specifies the phase to which the multiplication result reacts most sensitively by shifting the phase of the reference signal.

If the measurement signal obtained from the adder 125 is sin (ωt + α) and the stimulus signal is sin (ωt + β), the signal output by the phase sensitive detector 129 is as follows.

In this equation, α and β are phase offsets. The phase sensitive detector 129 specifies the values of α and β that maximize the value of cos (α−β), which is the DC component in the equation, by sequentially adjusting at least one of α and β. In this case, ideally, α = β + 2π × n (n is an integer).

The low-pass filter 131 constituting the lock-in amplifier 127 has a sufficiently large time constant so that a frequency component (2.0 kHz in this case) to be detected is sufficiently detected. As a result, the low-pass filter 131 removes cos (2ωt + α + β), which is a high-frequency component, from the signal output from the phase sensitive detector 129. For example, the low-pass filter 131 is set to decrease by 6 dB at a cutoff frequency of 3.0 kHz. Thereby, the low-pass filter 131 can take out only the detection signal according to the feature pattern of the stimulus signal used in the nerve stimulation. A specific example of the waveform of the detection signal is shown in FIG.

The determination unit 133 determines whether or not the neural stimulation has been detected based on the detection signal output from the lock-in amplifier 127. There are various methods for determining whether or not the determination unit 133 can detect the neural stimulation. For example, the determination can be made based on whether or not the detection signal exceeds a threshold value. If the output level of the detection signal is higher than the threshold value, it indicates that the correlation between the measurement signal detected by the magnetic sensor 120 and the stimulation pulse signal that is the reference signal is high, which is in the vicinity of the magnetic sensor 120. Means there is. On the other hand, if the output level of the detection signal is lower than the threshold value, it indicates that the correlation between the measurement signal and the stimulation pulse signal is low. When the correlation is low, it can be interpreted that the distance between the magnetic sensor 120 and the recurrent nerve 19 is long.

Alternatively, when the output level of the detection signal is low, it can be interpreted that a part of the vagus nerve 17 is damaged. This is because, for example, when all of the bundled nerves 200 are stimulated as a unit, such as the vagus nerve 17, if there is damage to some of them, the damaged nerve 200 transmits the stimulation, That is, no jump conduction occurs. This is because if the number of nerves 200 that perform jump conduction decreases, the intensity of the electromagnetic field generated by jump conduction also decreases, and the output level of the detection signal that detects this also decreases.

The threshold value used when the determination unit 133 determines the level of the output level of the detection signal can be set as follows, for example.

Here, A is the output level of the detection signal during application of the stimulation pulse, and B is the output level of the detection signal during a period in which no stimulation pulse is applied. If the level of B is low, the threshold value may be A / 2.

Moreover, since jump conduction is non-attenuating transmission as described above, the electromagnetic field intensity generated around the nerve 200 is constant regardless of the site of the nerve 200, and the electromagnetic field intensity is inversely proportional to the distance from the nerve 200. To do. Therefore, if the output level of the detected signal to be detected is large, the distance between the magnetic sensor 120 and the nerve 200 is short, and if the output level is low, it means that the distance between them is long. That is, the relative and spatial distance between the nerve 200 and the magnetic sensor 120 can be obtained by measuring the level of the detection signal at each position after moving or arranging a plurality of magnetic sensors 120. Is possible. The determination unit 133 may obtain the relative distance according to the level of the detection signal.

Furthermore, the determination unit 133 can also measure the relative distance on the path of the nerve 200 from the position where the nerve 200 is stimulated to the position where the stimulation is detected. More specifically, by measuring the time T1 when the stimulation of the nerve 200 is started and the time T2 when the detection signal exceeds the detection threshold, the time T2-T1 required for the transmission of the stimulus can be obtained. Therefore, after moving or arranging a plurality of magnetic sensors 120, it is possible to determine that a detection position with a small value of time T2-T1 is close to the stimulation position and a detection position with a large value is far from the stimulation position.

3. Effects According to the Present Embodiment As described above, the nerve detection device 100 according to the present embodiment applies artificial stimulation to the nerve 200 by the magnetic stimulation probe 110 and performs jump conduction for transmitting the stimulation. In response, an electromagnetic field generated around the nerve 200 is detected by the magnetic sensor 120. When a predetermined detection signal is detected as a result of signal processing on the signal measured by the magnetic sensor 120, it can be determined that the nerve 200 is running in the vicinity of the magnetic sensor 120. The nerve detection device 100 can also determine whether or not the nerve 200 is damaged, the relative and spatial distance between the magnetic sensor 120 and the nerve 200, the relative distance between the stimulation position and the detection position, and the like. That is, if the nerve detection device 100 is used, the position and state of the nerve 200 can be confirmed only by signal processing without the operator observing reflexes of related organs related to the nerve 200.

Further, in the nerve detection device 100 according to the present embodiment, a magnetic stimulation is given to the nerve 200 and an electromagnetic field generated around the nerve 200 is detected. That is, since there is no need to expose the nerve 200 or contact the nerve 200, the risk of damaging the nerve 200 can be avoided.

Furthermore, since the stimulation signal given to the nerve 200 is an intermittent burst signal and the signal level and pulse width are adjusted, the influence on the function of the related organs can be reduced.

4). Modifications Note that the configurations of the above-described embodiments may be combined or some components may be replaced. The configuration of the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the invention.

More specifically, for example, in the nerve detection apparatus 100 described above, magnetic stimulation is applied to the nerve 200, but an electrode probe that replaces the magnetic stimulation probe 110 is provided after the nerve 200 is exposed through incision. Electrical stimulation may be applied by contacting the nerve 200.

In the above embodiment, the conduction of the stimulus in the nerve 200 is detected as an electromagnetic field. However, the present invention is not limited to this, and an electric signal flowing through the nerve 200 may be detected. In this case, when an electrical signal based on a stimulus artificially applied to the nerve 200 is detected by the electrical sensor in contact with the nerve 200, it is determined that the nerve 200 in contact with the electrical sensor is the target nerve. Can do. In this case, an electrical sensor that is an alternative to the magnetic sensor 130 may detect electrical noise on the living body. Signal processing for the electrical sensor in contact with the nerve 200 and the electrical sensor that detects biological noise can be the same as in the above embodiment. Even in the method of detecting a stimulus by an electrical signal, the presence or absence of the stimulus can be detected only by signal processing without observing the reflection of the target organ as in the above embodiment. Further, by adjusting the stimulation level and the stimulation pulse width, the influence on the target organ can be suppressed to a low level.

In the above embodiment, the case has been described in which the characteristic pattern of the stimulation signal for applying stimulation to the nerve 200 is a single-frequency pulse, but the present invention is not limited to this. For example, it may be possible to vary the stimulation frequency and stimulation intensity. In this way, since the pattern of the stimulus signal can be made more characteristic, it can be easily distinguished from other electric / magnetic noise, and the detection accuracy by the detection signal can be improved.

Further, in the example shown in FIG. 1, stimulation is applied by the magnetic stimulation probe 110 from the vagus nerve 17 traveling in the neck, and an electromagnetic field signal corresponding to the stimulation is detected by the magnetic sensor 120 near the recurrent nerve 19. However, it is not limited to this. For example, stimulation is performed by the magnetic stimulation probe 110 in the vicinity of the recurrent nerve 19 in the thoracic cavity, and an electromagnetic field corresponding to the stimulation is generated by the magnetic sensor 120 disposed in the vicinity of the vagus nerve 17 running around the neck or around the thyroid cartilage 23. Detection is also conceivable.

10: human body 11: skin 13A: left common carotid artery 13B: right common carotid artery 15: aortic arch 17A: left vagus nerve 17B: right vagus nerve 19A: left recurrent nerve 19B: right recurrent nerve 21: trachea 23: thyroid cartilage 25: Vocal cord muscle 100: Neural detector 101: Periodic signal generator 103: Burst signal generator 105: Stimulation pulse generator 107: Driver 109: Stimulation amount adjustment unit 110: Magnetic stimulation probe 111: Stimulation pulse width adjustment unit 120: Magnetic sensor 121: Driver 123: Driver 125: Adder 127: Lock-in amplifier 129: Phase sensitive detector 130: Magnetic sensor 131: Low pass filter 133: Determination unit 200: Nerve 203: Axon 205: Myelin sheath 207: Lambier's Diaphragm

Claims

Means for generating a stimulus signal having a feature pattern;
A stimulation means for giving a nerve a stimulus based on the stimulation signal;
First detection means for detecting an electromagnetic field generated around the nerve in accordance with transmission of a stimulus in the nerve;
A nerve detection apparatus comprising: a second detection unit configured to detect a detection signal corresponding to the feature pattern based on a measurement signal corresponding to the electromagnetic field.
The stimulation signal includes a pulse signal having a constant frequency which is the characteristic pattern.
The nerve detection device according to claim 1.
The stimulation signal has the characteristic pattern including intermittently a pulse signal having a constant frequency at a constant period.
The nerve detection device according to claim 2.
The frequency of the fixed period is 0.1 Hz or more and 100 Hz or less,
The nerve detection device according to claim 3.
The nerve detection device according to any one of claims 2 to 4, further comprising first adjusting means for adjusting a signal level of the pulse signal.
The nerve detection device according to any one of claims 2 to 4, further comprising second adjustment means for adjusting a pulse width of the pulse signal.
The frequency of the pulse signal is 1 Hz to 10 kHz,
The nerve detection device according to any one of claims 2 to 6.
The nerve detection apparatus according to claim 1, further comprising means for changing at least one of a frequency or a stimulation intensity of the stimulation signal which is the characteristic pattern.
The second detection means detects the detection signal based on the stimulation signal and the measurement signal;
The nerve detection device according to any one of claims 1 to 8.
Further comprising third detection means for detecting a peripheral electromagnetic field;
The measurement signal is obtained by subtracting a signal corresponding to the peripheral electromagnetic field from a signal corresponding to the electromagnetic field.
The nerve detection device according to claim 9.
The detection signal is generated by filtering a high-frequency component with respect to a signal obtained by multiplying the stimulation signal and the measurement signal.
The nerve detection device according to claim 9 or 10.
The stimulation means applies a magnetic stimulation based on the stimulation signal to the nerve;
The nerve detection device according to any one of claims 1 to 11.
The stimulation means gives a stimulation based on the stimulation signal to the nerve as an electrical signal.
The nerve detection device according to any one of claims 1 to 11.
Based on the detection signal, a relative distance on a nerve path between a position where the stimulation is applied to the nerve and a position where the electromagnetic field is detected is determined.
The nerve detection device according to any one of claims 1 to 13.
Determining a relative and spatial distance from the nerve to the first detection means based on the detection signal;
The nerve detection device according to any one of claims 1 to 14.
Means for generating a stimulus signal having a feature pattern;
A stimulation means for giving a nerve a stimulus based on the stimulation signal;
First detection means for detecting an electrical signal associated with transmission of a stimulus in the nerve;
A nerve detection apparatus comprising: a second detection unit configured to detect a detection signal corresponding to the feature pattern based on a measurement signal corresponding to the electrical signal.
The second detection means detects the detection signal based on the stimulation signal and the measurement signal;
The nerve detection device according to claim 15.
A third detecting means for detecting biological noise;
The measurement signal is obtained by subtracting the biological noise from the electrical signal.
The nerve detection device according to claim 17.
Generating a stimulus signal having a feature pattern;
Providing a nerve with a stimulus based on the stimulus signal;
Detecting an electromagnetic field generated around the nerve accompanying transmission of a stimulus in the nerve;
A nerve detection method in which the apparatus performs a step of detecting a detection signal corresponding to the feature pattern based on a measurement signal corresponding to the electromagnetic field.
Generating a stimulus signal having a feature pattern;
Providing a nerve with a stimulus based on the stimulus signal;
Detecting an electrical signal associated with transmission of a stimulus in the nerve;
A nerve detection method in which the apparatus performs a step of detecting a detection signal corresponding to the feature pattern based on a measurement signal corresponding to the electrical signal.