Method and device for determining physiological parameters - Patents.com

Abstract

An apparatus (100) for determining a physiological parameter is disclosed, the apparatus comprising an elongated magnetic probe (102, 610, 702), a drive coil (104) surrounding the magnetic probe, a measurement coil (106, 602, 708, 1004) having at least a first section and a second section, and a controller (108). The controller is configured to energize the drive coil to generate a magnetic force to initiate movement of the magnetic probe towards an end (102A) of the magnetic probe, measure a first induced voltage value and a common induced voltage value, determine locator values ​​as a function of time, map the locator values ​​from the time domain to a spatial domain, calculate a velocity profile of the magnetic probe from the locator values ​​in the spatial domain, and determine the physiological parameter using the calculated velocity profile.

Description

[Technical field]

[0001] The subject matter disclosed herein (hereinafter the disclosure) relates generally to ophthalmic treatment devices, and more specifically, to methods and systems for determining physiological parameters.

[0002] Aqueous humor is a clear, watery liquid produced within the eye to protect the lens and maintain fluid pressure within the eye. Fluid pressure within the eye is known as intraocular pressure. Intraocular pressure is a physiological parameter that determines the strength of the eyeball and detects signs of optic nerve damage that may affect vision. Normal intraocular pressure has diurnal variations and is also different for each individual. However, if intraocular pressure is consistently too high or too low, it can cause problems with vision.

[0003] Traditionally, tonometry involves measuring intraocular pressure. In this test, a tonometer is used to measure the firmness of the eye. Traditionally, the Goldman Applanation Tonometer (GAT) anesthetizes the eye with a numbing drug and places a small amount of non-toxic dye into the eye. A small probe is then gently touched to the surface of the eye and the intraocular pressure is measured. Intraocular pressure is measured based on the force required to gently flatten a certain area of ​​the ocular surface. However, the thickness of the eye, the elasticity of the eye, and the amount of non-toxic dye used are sources of error that affect the accuracy of the measurements obtained. Perkins Applanation Tonometer (PAT) is also used to measure intraocular pressure. PAT is an ergonomic, easy-to-use handheld tonometer. However, PAT requires high skill to operate. As it is a handheld tonometer, it is less stable and requires topical application of fluorescein and anesthetic, which may cause scratches on the ocular surface.

[0004] The Tonopen is a type of Rebound Tonometry that measures intraocular pressure. The Tonopen requires a numbing drug to anesthetize the eye. The Tonopen has a probe that bounces off the surface of the eye to measure intraocular pressure. The probe used has a cone-shaped structure. The cone-shaped structure can accidentally cause small scratches on the ocular surface.

[0005] In view of these circumstances, a need exists to overcome the above-mentioned shortcomings associated with conventional methods relating to the measurement of physiological parameters.

[0006] The present disclosure seeks to provide an apparatus for determining a physiological parameter. The present disclosure also seeks to provide a method for determining a physiological parameter. It is an object of the present disclosure to provide a solution that at least partially overcomes the problems encountered in the prior art.

[0007] According to one aspect, the present disclosure provides an apparatus for determining a physiological parameter, the apparatus comprising: an elongated magnetic probe having a first end, a second end opposite the first end, and an intermediate portion between the first end and the second end; a drive coil disposed to partially surround the magnetic probe; a measurement coil having at least a first section and a second section, the measurement coil being positioned to partially surround the magnetic probe; With the controller; The controller comprises: selectively energizing the drive coil to generate a magnetic force to initiate movement of the magnetic probe toward the first end; measuring a first induced voltage value and a common induced voltage value as a function of time during movement of the magnetic probe, the first induced voltage value being a voltage across the first section and the common induced voltage value being a voltage value across the first section to the second section or across at least one of the second sections; determining a locator value as a function of time by dividing the first induced voltage value by the common induced voltage value; mapping the locator values ​​from a time domain to a spatial domain as a function of time; calculating a first velocity profile of the magnetic probe from spatial domain locator values ​​and determining a physiological parameter using the calculated first velocity profile; The present invention is configured to perform the following steps:

[0008] In another aspect, the present disclosure provides a method for determining a physiological parameter, the method comprising: energizing a drive coil to move an elongated magnetic probe toward a first end of the magnetic probe; measuring a first induced voltage as a function of time for a first section of the measuring coil; measuring an induced common voltage as a function of time, the voltage across the first section of the measurement coil and the second section of the measurement coil or across the second section; determining a first locator value as a function of time by dividing the measured induced voltage value by the measured induced common voltage value; mapping the first locator values ​​from a time domain to a spatial domain; calculating a first velocity profile of the magnetic probe from first locator values ​​in a spatial domain; determining a physiological parameter using the first velocity profile; Includes.

[0009] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure substantially eliminate or at least partially address the aforementioned problems in the prior art and allow for accurate determination of the position of a magnetic probe by calculating an induced voltage.

[0010] Further aspects, advantages, features and objects of the present disclosure will become apparent from the accompanying drawings and detailed description of illustrative embodiments, taken in conjunction with the appended claims.

[0011] It will also be appreciated that features of the present disclosure can be combined in various combinations without departing from the scope defined by the appended claims. [Brief description of the drawings]

[0012] The foregoing summary, as well as the following detailed description of exemplary embodiments, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the disclosure, example configurations of the disclosure are shown in the drawings. However, the disclosure is not limited to the specific methods and apparatus disclosed herein. Also, the drawings are not drawn to scale. Similar elements are designated by the same numerals wherever possible. Embodiments of the present disclosure will now be described, by way of example only, with reference to the following drawings, in which: [Figure 1] FIG. 1 is a block diagram of a system of an apparatus for determining physiological parameters according to an embodiment of the present disclosure. [Diagram 2] 1 is a graph of the force induced on a magnetic probe per ampere of current in the signal or drive coil versus position in millimeters. [Diagram 3] 13 is a graph showing a common induced voltage of a measuring coil. [Figure 4] FIG. 13 shows three locator signals measured using four differential amplifiers to measure the voltage across each signal coil segment. [Diagram 5] 1 is a graph for determining a position of an elongated magnetic probe according to an implementation of the present disclosure. [Figure 6] 1 is a measurement coil assembly according to an implementation of the present disclosure. [Figure 7] FIG. 1 is a schematic diagram of a robotic system for determining the velocity and position of an elongated magnetic probe according to an implementation of the present disclosure. [Figure 8] 1 is an electrical circuit for summing induced voltages according to one implementation of the present disclosure. [Figure 9] 1 is an induced signal voltage of a measurement coil according to one implementation of the present disclosure. [Figure 10] FIG. 2 is a block diagram of a system for a basic implementation of an apparatus according to an embodiment of the present disclosure. [Figure 11A] 1 is a graph for achieving optimal connection of a first amplifier and a second amplifier according to an implementation of the present disclosure. [Figure 11B] 1 is a graph for achieving optimal connection of a first amplifier and a second amplifier according to an implementation of the present disclosure. [Figure 12A] 1 is a graph showing signal voltage and common induced voltage values ​​according to certain implementations of the present disclosure. [Figure 12B] 1 is a graph showing signal voltage and common induced voltage values ​​according to certain implementations of the present disclosure. [Figure 13A] 11 is a graph for measuring a locator value by summing multiple signal amplifiers according to certain implementations of the present disclosure. [Figure 13B] 11 is a graph for measuring a locator value by summing multiple signal amplifiers according to certain implementations of the present disclosure. [Figure 13C] 11 is a graph for measuring a locator value by summing multiple signal amplifiers according to certain implementations of the present disclosure. [Figure 13D] 11 is a graph for measuring a locator value by summing multiple signal amplifiers according to certain implementations of the present disclosure. [Figure 14A] 1 shows a flowchart illustrating steps of a method for determining a physiological parameter according to an embodiment of the present disclosure. [Figure 14B]1 shows a flowchart illustrating steps of a method for determining a physiological parameter according to an embodiment of the present disclosure. [Figure 15] 1 is an explanatory diagram of speed profile determination. In the accompanying drawings, underlined numbers are used to represent the item where the number is located or adjacent to the number. Numbers without underlines are associated with the item identified by the line extending from the number. When a number is not underlined and is accompanied by an arrow, the number is used to identify the generic item to which the arrow points. Detailed Description of the Embodiments

[0013] The following detailed description illustrates embodiments of the present disclosure and how they may be practiced. Although several forms for carrying out the present disclosure have been disclosed, those skilled in the art will recognize that other forms for carrying out the present disclosure are also possible.

[0014] According to one aspect, certain embodiments of the present disclosure provide an apparatus for determining a physiological parameter, the apparatus comprising: an elongated magnetic probe having a first end, a second end opposite the first end, and an intermediate portion between the first end and the second end; a drive coil disposed to partially surround the magnetic probe; a measurement coil having at least a first section and a second section, the measurement coil being positioned to partially surround the magnetic probe; With the controller; The controller comprises: selectively energizing the drive coil to generate a magnetic force to initiate movement of the magnetic probe toward the first end; measuring a first induced voltage value and a common induced voltage value as a function of time during movement of the magnetic probe, the first induced voltage value being a voltage across the first section and the common induced voltage value being a voltage value across the first section to the second section or across at least one of the second sections; determining a locator value as a function of time by dividing the first induced voltage value by the common induced voltage value; mapping the locator values ​​from a time domain to a spatial domain as a function of time; calculating a first velocity profile of the magnetic probe from spatial domain locator values ​​and determining a physiological parameter using the calculated first velocity profile; The present invention is configured to perform the following steps:

[0015] Preferably, the measurement of the voltage value from the first section is performed simultaneously during the measurement of the common induced voltage. The common induced voltage can be measured across the first and second sections, i.e., it can be measured as the sum of the voltage of the first section and the voltage of the second section. Or the common induced voltage can be measured as the voltage of the second section. The second section can overlap the first section. Using multiple sections of the measuring coil, these signal voltages can be combined in various ways before calculating the probe speed independent locator signal. In some embodiments, the measurement of the first section is performed first, and the measurement of the common induced voltage is performed in another measurement cycle. A common start time (t0) based on relative time is defined as the measurement start time for both.

[0016] According to another aspect of the present disclosure, there is provided a method for determining a physiological parameter, the method comprising: energizing a drive coil to move an elongated magnetic probe toward a first end of the magnetic probe; measuring a first induced voltage as a function of time for a first section of the measuring coil; measuring an induced common voltage as a function of time, the voltage across the first section of the measurement coil and the second section of the measurement coil or across the second section; determining a first locator value as a function of time by dividing the measured first induced voltage value by the measured induced common voltage value; mapping the first locator values ​​from a time domain to a spatial domain; calculating a first velocity profile of the magnetic probe from first locator values ​​in a spatial domain; determining a physiological parameter using the first velocity profile; Includes.

[0017] The velocity and magnetization of the elongated magnetic probe are determined, thereby allowing for more accurate measurements.

[0018] The present disclosure provides an apparatus for determining a physiological parameter. The apparatus may refer to an instrument that may be used to measure an ocular physiological parameter, such as the pressure inside the eye or the tactile sensitivity of the eye. In some embodiments, the apparatus is a tonometer. The tonometer is used to measure intraocular pressure from ophthalmic measurements. The intraocular pressure is calculated from a voltage signal that represents the velocity (as a function of time) of an elongated magnetic probe that is bounced off the ocular surface. The magnitude of the signal depends on the magnetic force and the velocity of the elongated magnetic probe.

[0019] The device comprises an elongated magnetic probe having a first end, a second end opposite the first end, and an intermediate portion between the first end and the second end. The first end of the elongated magnetic probe is made of a biocompatible material and impinges on the surface of the eye during use. The first portion being made of a biocompatible material advantageously allows the probe to function in direct contact with the living tissue of the eye, minimizing discomfort and pain. It is noteworthy that biocompatible materials are non-carcinogenic, non-toxic, and resistant to corrosion. The elongated magnetic probe may be made of a thin wire of a magnetic material. The elongated magnetic probe may be, for example, 20 millimeters long and 0.5 millimeters wide. The magnetic material of the elongated magnetic probe may be a ferromagnetic material. When the elongated magnetic probe moves in the measuring coil, an induced voltage is generated. However, the magnetic force of the elongated magnetic probe is very small. The elongated magnetic probe is pushed back only by the surface of the eye, and there is no other force to push it back.

[0020] The device includes a drive coil disposed to partially surround an elongated magnetic probe. The drive coil is disposed as a loop along which the elongated magnetic probe can move. The drive coil has a finite number of loops. The drive coil can be disposed along any point between a first end and a second end of the magnetic probe. For example, the drive coil can be disposed near the first end. When a current is applied to the drive coil, the drive coil moves the elongated magnetic probe. The drive coil pulls the elongated magnetic probe toward the eye surface at a velocity equal to the product of the current supplied through the drive coil and the magnetization of the elongated magnetic probe.

[0021] The device comprises a measuring coil having at least a first section and a second section. The measuring coil is arranged to partially surround the magnetic probe. The measuring coil has a finite number of loops. The total number of loops of the measuring coil is divided between the first section and the second section. The first section and the second section may each have at least one loop along which the elongated magnetic probe is movable. The elongated magnetic probe may be capable of moving along an intermediate section between the first section and the second section. As the measuring coil has two or more sections, it is possible to simultaneously measure different voltage profiles induced by the movement of the elongated magnetic probe. The technical effect of this is to eliminate the uncertainty of the magnetization constant of the probe. Indeed, as will be explained below, by performing measurements with at least two different measuring coils, the speed of the probe can be determined without any knowledge of the value of the magnetization.

[0022] In some embodiments, the measurement coil is used as a drive coil during a first period of time and as a second section of the measurement coil during a second period of time after the first period. Here, the measurement coil is used to pass a current, thereby inducing a motion in the elongated magnetic probe. Then, immediately after the elongated magnetic probe is accelerated to its operating speed, the measurement coil is used to measure the induced voltage in the measurement coil. Advantageously, this reduces the number of coils in the device. The measurement coil can have multiple functions, depending on how the controller controls the measurement coil, e.g., whether to pass a current or to measure the induced voltage.

[0023] In some embodiments, the first and second sections of the measurement coil are connected in series. Here, series connection means an electrical coupling between the last loop of the first section and the first loop of the second section. Typically, the measurement of the voltage induced in the series connected measurement coil can be achieved by connecting a voltmeter to the first section of the measurement coil and the second section of the measurement coil. Alternatively, the voltage induced in the first section is measured. Then, both the voltages induced in the first and second sections may be measured together to derive a total induced voltage value. The voltage induced in the second section can be calculated by subtracting the voltage induced in the first section from the total induced voltage.

[0024] In some embodiments, the measurement coil has a third section connected in series with the first and second sections of the measurement coil and arranged to surround the third section of the elongated magnetic probe. The third section may have at least one loop around which the elongated magnetic probe can move. Additional sections may be added to the measurement coil to generate more data points.

[0025] In one example, the measurement coil is divided into a first section, a second section, a third section, and a fourth section. The drive coil has one section. Coupling leads are wired to the points where the first section, the second section, the third section, and the fourth section of the measurement coil are connected to each other. A first coupling lead is connected to the left end of the first section, a second coupling lead is connected to the connection between the first section and the second section, a third coupling lead is connected to the connection between the second section and the third section, a fourth coupling lead is connected to the connection between the third section and the fourth section, and a fifth coupling lead is connected to the right end of the fourth section. An exemplary implementation of such a measurement coil is described in more detail in FIG. 6.

[0026] The apparatus includes a controller. The controller is a computing device operable to respond to and process information. By way of example, the controller may be an embedded microcontroller, a microprocessor, a computer, or a portable computing device. The controller is communicatively coupled to the measurement coil and the drive coil. The controller energizes the drive coil to move the elongated magnetic probe toward the ocular surface.

[0027] The controller is configured to selectively energize the drive coil to generate a magnetic force that initiates movement of the elongated magnetic probe toward the first end. Here, selective energization refers to switching on and off a power supply voltage of the drive coil. When the power supply voltage of the drive coil is switched on, an electric field is generated. Typically, the higher the power supply voltage of the drive coil, the stronger the magnetic force. As a result, the acceleration of the elongated magnetic probe increases. The magnetic force is a function of the magnetization of the elongated magnetic probe. The magnetization here refers to the strength of the magnetization of the elongated magnetic probe. The higher the magnetization, the stronger the magnetic force. By selectively energizing the drive coil, the elongated magnetic probe can be moved toward the eye surface. When the polarity of the drive coil by selective energization is reversed, the elongated magnetic probe moves in the opposite direction. The elongated magnetic probe moves in a direction that can be controlled by the controller whenever necessary. Here, the voltage is a function of the speed and magnetization of the elongated magnetic probe. The velocity of the elongated magnetic probe is continuously monitored by the measuring coil as a function of time. Such information regarding the velocity of the elongated magnetic probe can be used to determine the eye pressure, which can be used for diagnostic purposes. When a current is supplied to the drive coil, a magnetic field is induced in the drive coil. The magnetic field is proportional to the current and the finite number of loops of the drive coil. The magnetic field can be controlled by controlling the current supplied to the drive coil. The magnetic field generates a magnetic force that is applied to the elongated magnetic probe. This magnetic force is a function of the magnetization of the elongated magnetic probe. The acceleration of the elongated magnetic probe can be calculated by dividing the mass of the elongated magnetic probe by the force applied to the elongated magnetic probe. Thus, the elongated magnetic probe is accelerated by the current pulse of the drive coil. That is, the magnetic field generated by the current pulse of the drive coil acts on the magnetic probe, accelerating the effect on the magnetic probe. The elongated magnetic probe travels through the measuring coil towards the eye surface and bounces off the eye surface. One of the technical problems in performing the above measurements is the uncertainty of the magnetization value. In fact, when comparing two probes with different manufacturing patches (e.g. different manufacturing dates or times), there can be a large difference in the magnetization value and magnetization capacity of the probes. This leads to an uncertainty in measuring the induced voltage. Since the speed of the probe is a function of the magnetization value of the probe, for example, even with the same driving voltage (current), the probe movement can be faster.

[0028] In some embodiments, the present disclosure may incorporate a magnetization cycle for magnetizing the elongated magnetic probe, where the magnetization cycle is accomplished by current pulses in the drive coil and the measurement coil, respectively. These current pulses pull the elongated magnetic probe back and forth within the device. The magnetization cycle may be completed with a calibration cycle, which collects information necessary to set the degree of acceleration by the drive coil to a value for optimal speed of the elongated magnetic probe. The calibration cycle checks both the device and the elongated magnetic probe before determining the physiological parameters. In some embodiments, the calibration cycle may be used to collect lookup table values ​​for mapping the locator value(s) as a function of time from the time domain to the spatial domain.

[0029] In an embodiment, in use, a first section of the measurement coil surrounds a first section of the elongated magnetic probe and a second section of the measurement coil surrounds a second section of the elongated magnetic probe. When the elongated magnetic probe is in a first spatial position, the first section of the elongated magnetic probe is different from the second section of the elongated magnetic probe. In a geometric setup of the device, the first spatial position is an initial position before the elongated magnetic probe is selectively energized. In the first position, the elongated magnetic probe is fully housed within the device.

[0030] In some embodiments, in use, when the elongated magnetic probe is in its second spatial position, the first section of the measurement coil does not surround the first section of the elongated magnetic probe, and the second section of the measurement coil surrounds the second section of the elongated magnetic probe, where the second spatial position is different from the first spatial position. The second spatial position may be, for example, when the elongated magnetic probe is moved to an extreme position, e.g., a position substantially removed from the measurement coil. Since the first section of the measurement coil does not surround the elongated magnetic probe at all, the change in magnetic flux on the measurement coil is larger compared to a measurement coil that partially surrounds the elongated magnetic probe. In a uniformly magnetized elongated magnetic probe, the magnetic flux is constant throughout. The magnetic flux lines leave one end and re-enter at the opposite end. Some of the magnetic flux lines pass through the wall of the measurement coil and re-enter at the opposite end. Furthermore, since the elongated magnetic probe is long and located very close to the measurement coil, the magnetic flux of the measurement coil changes over time for each turn.

[0031] The current in the measurement coil acts on the elongated magnetic probe with a controlled magnetic field pulse, sending the elongated magnetic probe to the eye surface at a desired speed. The speed of the elongated magnetic probe is determined by the amplitude of the current pulse, the length and magnetization of the elongated magnetic probe, and the friction between the elongated magnetic probe and the measurement coil and drive coil. When the elongated magnetic probe hits the eye surface, it bounces back. By measuring the speed profile of the elongated magnetic probe during its approach, bounce and / or return, the intraocular pressure can be determined.

[0032] The controller is configured to measure the first induced voltage values ​​from the first section and the common induced voltage values ​​as a function of time during the movement of the elongated magnetic probe. When the elongated magnetic probe moves through the loop of the first and second sections, a voltage is induced according to Faraday's law of induction. The controller is configured to measure the first induced voltage values ​​as a function of time while the elongated magnetic probe moves through the first section. Furthermore, a common induced voltage of the measuring coil is measured as a function of time. In case there are two sections (first section and second section), the common induced voltage is the induced voltage across both sections. In case there are, for example, three or four sections, the common induced voltage is the induced voltage across the first, second, third and fourth sections.

[0033] In some embodiments, a robotic system is used to precisely control the position of the elongated magnetic probe, thereby controlling the sampling interval of the induced voltage and the geometry of the measurement coil. As the elongated magnetic probe passes through the first section, the second section, the third section and the fourth section towards the eye surface, the induced voltage changes as a function of time. The amplitude of the induced voltage is proportional to the position and the velocity of the elongated magnetic probe. If the magnetization of the elongated magnetic probe is known, a common induced voltage is suitable for measuring the velocity. This has been explained in detail in relation to FIG. 4. As explained, one of the technical problems is that the magnetization of the elongated magnetic probe can have various values, making a simple calculation of the velocity difficult.

[0034] Initially, the common induced voltage (and the first induced voltage) rises while the drive coil accelerates the elongated magnetic probe. Then the elongated magnetic probe hits the eye surface and decelerates to zero in about 1 millisecond (ms), which is between 20 ms and 35 ms. Then the magnetic probe bounces back. This depends on the speed of the magnetic probe and its distance from the eye surface. The deceleration of the elongated magnetic probe occurs for example between 20, 24, 28 or 32 ms and 21, 25, 30 or 35 ms. Here, the manner in which the speed of the magnetic probe changes during contact with the eye surface depends mainly on the speed of the magnetic probe and also on the intraocular pressure through the pushing back force. The main parameter that depends on the intraocular pressure is given by the slope of the deceleration of the speed of the magnetic probe. The deceleration of the speed of the magnetic probe is equal to the magnetic force between the magnetic probe and the eye surface. Additionally, the disclosed device provides a compensated output signal from the elongated magnetic probe from which intraocular pressure is derived. The output signal is validated with patient data using other types of measurements to generate a curve that is converted to reveal true intraocular pressure. As a result, except when intraocular pressure is low, intraocular pressure is equal to the input signal multiplied by a factor of approximately 1.5 minus a constant. The lower the intraocular pressure, the higher the coefficient and the lower the constant. This has been described in more detail in connection with FIG. 3. The first and second signal amplifiers used are operational amplifiers. The operational amplifier applies voltages to the negative and positive terminals of the first and second signal amplifiers through resistors at the input of the amplification stage. Furthermore, multiple induced voltage signals can be easily added or subtracted to a common output with weights set by resistors. Specifically, a differential amplifier can be used to easily implement the present disclosure. Here, a first input of the differential amplifier is connected to the negative terminal and a second input of the differential amplifier is connected to the positive terminal. A basic implementation may be made using a first amplifier and a second amplifier. The first amplifier has multiple inputs for summing selected induced voltages from the first section or the second section, or in some embodiments, from the third section or the fourth section. The second amplifier is a differential amplifier for calculating a common induced voltage. In one example, the first amplifier is electrically coupled to the second section and the third section to determine a difference between the induced voltages of the second section and the third section, and the second amplifier is electrically coupled to the first section and the fourth section to generate the common induced voltage. In one example, the first induced voltage in the first section is called "V1", the second induced voltage in the second section is called "V2", and the third induced voltage in the third section is called "V3". Furthermore, four resistors "R1", "R2", "R3", and "R4" are connected to the differential amplifier. In such an example, the output voltage V out is calculated as follows:

[0035] V out =(V1·R1 / (R1+R2)+V2·R1 / (R1+R2))(1+R4 / R3)-V3·R4 / R3

[0036] To detect very small signals, a V resistor proportional to V1-V3 is required. out It has been found that using a differential amplifier to provide:

[0037] Such an example will be described in more detail with reference to FIG. 8. Furthermore, any combination of induced voltages in the measurement coils can be obtained by using an operational amplifier with four or less inputs and adjusting the sign and amplification factor with the value of the sum resistor. Furthermore, an optimized signal can be obtained by combining the output of the first amplifier and the output of the second amplifier. Here, the optimized signal may be made sensitive to requirements such as the position of the elongated magnetic probe, and may be made insensitive to another parameter such as the magnetization degree.

[0038] The controller is configured to determine the locator values ​​as a function of time by dividing the first induced voltage values ​​by the common induced voltage value. The technical effect of dividing the first voltage values ​​(for each pair) by the respective common induced voltage value is to eliminate the unknown magnetization constant of the elongated magnetic probes. The induced voltage is a function of the change in the magnetic flux Φ of the measuring coil. The magnetic flux is a function of the magnetic field B, i.e. the magnetization of the elongated magnetic probes. Since B is constant, it can be eliminated by dividing the first induced voltage by the common induced voltage value. The locator values ​​represent values ​​that are correlated with the actual position of the elongated magnetic probe. Considering that measurements are made as a function of time, the locator values ​​are initially a function of time. Hence, the locator values ​​are in the time domain. The first induced voltage values ​​are divided by the common induced voltage obtained in the corresponding measurements. Experimentally, it was found that a similar shape is obtained when dividing the first induced voltage coil value by the common induced voltage value. Hence, the locator values ​​are independent of the velocity of the elongated magnetic probe, which is a function of the magnetization. This eliminates the variation of the current in the drive coil with respect to the magnetization of the probe. Typically, a first induced voltage value and a common induced voltage value are measured to resolve the uncertainty of the magnetization of the elongated magnetic probe. The first induced voltage value and the common induced voltage value are functions of the speed and magnetization of the elongated magnetic probe. As an example, a first signal amplifier measures a common induced voltage across the measurement coils for a drive coil of 0.2 volts (V) and a drive coil of 0.3 V. Here, the common induced voltage is referred to as "U15". A second signal amplifier is electrically coupled to the second coupling lead of the second section and the fourth coupling lead of the junction of the third and fourth sections. The voltage measured from here is referred to as "U24". Dividing "U24" by "U15" results in exactly the same results for 0.2V and 0.3V drive coils, since the dependence on the drive coil amplitude has been removed. The speed of the elongated magnetic probe has a direct effect on the induced voltage. Here, the second induced voltage value increases by 1.6, and the locator value in the middle area is the same within the measurement accuracy. Also, the voltage signals below Z=5 millimeters (mm) and above Z=10 mm are not taken into account. This is because the induced voltage value does not change rapidly as a function of Z, and the locator value is constant. This point is explained in more detail in relation to Figure 11.

[0039] Continuing with the previous example, the useful range is mostly to the left and narrow. Thus, the present disclosure can be implemented as required. The useful range can be increased by using a fourth signal amplifier, a fifth signal amplifier, etc. This will be explained in more detail in conjunction with FIG. 12. FIG. 13 shows the signals collected to cover a wide range centered on the region of interest (ROI) when two amplifiers are used. The signal U15 is measured by taking the sum of the output signal from the first signal amplifier and the output signal from the second signal amplifier. Here, the sum of the output signal from the first signal amplifier and the output signal from the second signal amplifier is called "U+". Also, the difference between the output signal from the first signal amplifier and the output signal from the second signal amplifier is called "U-". Usually, the locator value can be calculated by the ratio between the difference between the output signal from the first signal amplifier and the output signal from the second signal amplifier and the sum of the output signal from the first signal amplifier and the output signal from the second signal amplifier. That is, L=(U-) / (U+) It is.

[0040] The controller is configured to map the voltages U13 and U35 as a function of time. Here, the time domain refers to the locator values ​​as a function of the sampling time. The mapping can be performed, for example, by using a look-up table. The locator values ​​are determined experimentally for each measurement coil geometry. This can be done, for example, by moving the elongated magnetic probe back and forth with an actuator and measuring the induced voltage values ​​at the same time. From the movement with the drive coil, the relationship between the spatial position of the elongated magnetic probe and the induced voltage values ​​can be determined.

[0041] In some embodiments, the mapping from the time domain to the spatial domain is done by at least one of a pre-determined transfer function or a look-up table. The mapping of the time domain signal is done by placing the probe at a precise position and vibrating it with a very small displacement at a suitable frequency, for example on the order of 1 kilohertz. The time domain signal at this position is proportional to the induced voltage at 1 kHz. This is done to calibrate the position curve. The mapping from the time domain to the spatial domain is a necessary step to determine the velocity of the probe. The creation of the pre-determined transfer function is disclosed below in Example 1, and an example of how to determine the look-up table is disclosed in Example 2.

[0042] The controller is configured to calculate a first velocity profile of the elongated magnetic probe from the spatial domain locator values ​​and to determine a physiological parameter using the calculated first velocity profile. The first velocity profile is calculated from the time domain locator values ​​relative to the spatial domain locator values. Depending on the intended application, the velocity as a function of time is used to determine a physiological parameter, such as intraocular pressure. As an example, the velocity of the elongated magnetic probe and the response of the ocular surface to stop the elongated magnetic probe after it is projected towards the ocular surface can be determined by calculating the first derivative of the velocity. Also, the velocity at which the elongated magnetic probe bounces off the ocular surface can be determined. If the elongated magnetic probe bounces at a high velocity, the intraocular pressure is high, and if the elongated magnetic probe bounces at a low velocity, the intraocular pressure is low. Measurements of time and velocity of the elongated magnetic probe may be collected in conjunction with a medical test (e.g., a clinical trial). A function of velocity of the elongated magnetic probe geometry may then be compared to the clinical trial measurements to determine a physiological parameter as discussed in this disclosure. The velocity of the elongated magnetic probe may be determined from dividing the first induced voltage value by the second induced voltage value to obtain a relative value that is used to determine the velocity of the elongated magnetic probe. In some embodiments, the first velocity profile includes at least one of a velocity in the spatial domain and a velocity in the time domain. In some embodiments, the second velocity profile includes at least one of a velocity in the spatial domain and a velocity in the time domain.

[0043] This disclosure is not intended to limit the scope of the device to measuring physiological parameters of the eye, as the device can be used to measure physiological parameters on any part of the body in a manner similar to that described for the ocular surface.

[0044] In some embodiments, the controller of the device is further configured to: A second induced voltage value from a section other than the first section is measured as a function of time during a travel time of the elongated magnetic probe. Determine a second locator value as a function of time by dividing the second induced voltage value by the common induced voltage value. Mapping the second locator function from the time domain to the spatial domain. Calculating a second velocity profile of the elongated magnetic probe from the second locator values ​​in the spatial domain. Using the calculated second velocity profile to update the physiological parameter, which may be done, for example, by calculating an average of the first velocity profile and the second velocity profile and using the average as the velocity profile to determine the physiological parameter.

[0045] The present disclosure also relates to the above-mentioned method, the various embodiments and variants disclosed above apply mutatis mutandis to this method.

[0046] In some embodiments, the elongated magnetic probe is directed towards the patient and bounces off a surface of the patient's body. The surface may refer to the surface of the patient's eye. By directing the probe at the surface and measuring the velocity profile, the intraocular pressure of the patient can be determined, for example. For example, if the velocity profile shows a low acceleration when the probe strikes the eye, this indicates low intraocular pressure. A high acceleration (i.e., a large change in the velocity profile) indicates high intraocular pressure.

[0047] In some embodiments, measurements are taken during movement of an elongated magnetic probe to obtain induced voltage value(s) as a function of time.

[0048] In some embodiments, the physiological parameter is determined by analyzing at least one of the acceleration during impact of the elongated magnetic probe on the patient's body surface, the change in velocity before and after impact, and the penetration of the elongated magnetic probe into the body surface. Acceleration can be determined from the velocity profile, since it is the derivative of velocity with respect to time.

[0049] In some embodiments, the physiological parameter value is updated in the following manner. Measuring a second induced voltage as a function of time in a section of the measuring coil different from the first section. Determine a second locator value as a function of time by dividing the second induced voltage value by the common induced voltage value. Mapping the second locator function from the time domain to the spatial domain. · Calculating a second velocity profile of the elongated magnetic probe as a function of position from the second locator values ​​in the spatial domain. · Updating the physiological parameters using the calculated second velocity profile.

[0050] In some embodiments, the first velocity profile includes at least one of a velocity in the spatial domain and a velocity in the time domain.

[0051] In some embodiments, the second velocity profile includes at least one of a velocity in the spatial domain and a velocity in the time domain.

[0052] Example 1: Predetermining the transfer function by experiment

[0053] A mapping of locator values ​​is performed to obtain the localization, where the localization is the value of Z and the velocity of the probe dZ / dt. Mathematically, the elongated magnetic probe is mapped into a linear space with Z as the position. A robotic system is then used to set and map the values ​​of Z to measure a first function L with respect to Z, where the first function L with respect to Z is denoted as "L(Z)". Further, a second function with respect to Z is determined, where the second function is a function that depends on the position of the elongated magnetic probe but is independent of the signal coil induced voltage signal, the degree of magnetization of the elongated magnetic probe, and the probe velocity. The time derivative of Z is used to calculate the velocity (v) of the elongated magnetic probe.

[0054] v = dZ / dt = (dL / dt) / dL / dZ)

[0055] For example, for a fast moving, elongated magnetic probe, the locator values ​​are sampled at short time intervals. This short time interval is given by the formula T n -T n-1 where n is a finite time interval. The locator value is given by L n -L n-1 and increases correspondingly. The velocity of the magnetic probe for the nth sample is given by

[0056] v n =K(L n -L n-1 ) / (T n -T n-1 )

[0057] Multiple data points can be collected, making a long sweep of Z values ​​starting from Z=0, thereby creating multiple steps spaced 1 mm apart. Here, the voltage signal is the root mean square value of the measured voltage in millivolts (mVrms) at the output of a digital oscilloscope. The range of Z that gives useful locator values ​​is 1 to 7, limited by the maximum distance allowed for the examined eye to obtain reliable results. Although multiple points of data are used to fit the localization curve, the first 10 points of data are collected for each U+ and U- voltage. From the given data, the first five Z values ​​are calculated. This is explained in more detail in relation to FIG. 13C. The values ​​shown in the table of FIG. 13D are then observed. The position of the elongated magnetic probe is obtained by removing the dependence of the velocity, magnetization, and elongated magnetic probe for the first induced voltage value, the second induced voltage value, the third induced voltage value, and the fourth induced voltage value, and dividing each point by the common induced voltage. Furthermore, with the help of the measurements, suitable linear combinations can also be created, as explained in detail in connection with FIG.

[0058] Example 2: How to determine the above lookup table by moving a long thin magnetic probe back and forth

[0059] In the present disclosure, a first induced voltage, used to indicate the speed of an elongated magnetic probe, is induced in a measurement coil by vibrating the elongated magnetic probe using a vibrator. The vibrator uses a commercially available piezoelectric element to vibrate the elongated magnetic probe at its mechanical resonant frequency of 875 Hertz (Hz). Typically, the amplitude of the vibration of the vibrator is small. The vibrator is driven by setting a signal generator to 0.2 Volts (V) and 0.3 V, respectively. The common induced voltage is the sum of the induced voltages of the measurement coils. The sum of the voltages of the first and second sections may be measured by measuring the induced voltages of the first and second sections separately.

[0060] In some embodiments, the common induced voltage is measured across all sections of the measurement coil, where at least the first and second sections of the measurement coil are connected to a first signal amplifier and a second signal amplifier. The first and second signal amplifiers also form a differential input that can be changed as required. In an exemplary implementation, the first signal amplifier is connected between the first and third sections, and the second signal amplifier is connected between the third and fourth sections. The vibrator also generates a signal from the first and second signal amplifiers that is less than 1 volt (V). This voltage magnitude is low enough to avoid saturation. Typically, the output of the drive coil is the root mean square of the measured voltage, expressed in millivolts (mVrms). A drive coil with a typical voltage of 0.2V has an output of 500mVrms. A drive coil with a typical voltage of 0.3V has an output of 800mVrms. The inputs of the first and second signal amplifiers are connected to the coupling leads of the measurement coil, which correspond to approximately 1 millivolt (mV) and 1.6mV, respectively. The outputs of the first and second signal amplifiers are also connected to the inputs of a digital oscilloscope for measuring the velocity of the elongated magnetic probe. Induced voltages are obtained from the four sections of the measuring coil. Here, the induced voltage obtained between the first and second coupling leads is called "U12", the voltage obtained between the second and third coupling leads is called "U23", the voltage obtained between the third and fourth coupling leads is called "U34" and the voltage obtained between the fourth and fifth coupling leads is called "U45". Measurements are taken over 30 magnetization cycles by manually operating the signal generator with a drive coil of 875 Hertz (Hz), 0.2V or 0.3V. A signal amplifier is connected to the drive coil through the third signal amplifier. A digital oscilloscope measures the root mean square value of the output from the first signal amplifier and the second signal amplifier and digitally stores it in a spreadsheet. The spreadsheet has Visual Basic code for receiving and displaying the measurements as a function of the position of the elongated magnetic probe. The position of the elongated magnetic probe is determined by integrating the velocity over time. In some embodiments, the position of the elongated magnetic probe is controlled by a robotic system. The robotic system has a linear screw driven by a stepper motor, allowing the elongated magnetic probe to move linearly with high precision. Moving the measurement coil at a slow speed does not induce a voltage in the signal coil. The robotic system changes position in a step-like manner between measurements. Here, the position of the elongated magnetic probe is referred to as "Z". The mechanical end position is the start position Z=0. The robotic system is actuated to change position by 1 millimeter (mm) for the next measurement point. This is explained in more detail in relation to FIG. 7.

[0061] In one implementation of the present disclosure, the locator values ​​were observed to be linear in the range of Z=1-5 millimeters (mm). (Z is the distance the probe moves relative to the coil). An approximation is obtained by fitting a trend line using a spreadsheet to the points in the range of Z=1 mm to 5 mm. The resulting locator value trend line has the general linear equation form of y=mx+c. This trend line represents the position of the elongated magnetic probe in the range of Z=1 mm to 5 mm for making measurements in the device. Here, the variables "x" and "y" are selected for further calculations. Then, to fit the coordinates of the present disclosure, the variable x is made equivalent to Z and the variable y is made equivalent to 1000 times a function of L(Z). The equation of the trend line is thus given by:

[0062] 1000L=-mZ+c

[0063] Therefore, Z can be expressed as follows:

[0064] Z=-(1000 / m)L+c / m

[0065] Here, the constant K = (-1000) / m. Also, c / m is the value of Z when L = 0. In other words, c / m = Z o Therefore, V = K(dL / dt), where V is a variable. As a result, we obtain the following equation.

[0066] Z=-Vt+Z o

[0067] Thus, based on the embodiment and test example, a velocity profile of the elongated magnetic probe can be determined from the locator values. The velocity profile can be used to determine a physiological parameter. That is, the velocity of the elongated magnetic probe can be used to determine the physiological parameter. In particular, the first induced voltage is proportional to the velocity of the elongated magnetic probe. [Detailed description of the drawing]

[0068] Referring to FIG. 1, a block diagram of a device 100 for determining a physiological parameter is shown, according to an embodiment of the present disclosure. The device 100 includes an elongated magnetic probe 102, a driving coil 104, a measuring coil 106, and a controller 108. The elongated magnetic probe 102 has a first end 102A, a second end 102B opposite the first end 102A, and an intermediate section 102C between the first end 102A and the second end 102B. The driving coil 104 is disposed to partially surround the elongated magnetic probe 102. The measuring coil 106 has at least a first section 106A and a second section 106B. The measuring coil 106 is disposed to partially surround the elongated magnetic probe 102. In the figure, the measuring coil has four sections, namely a first section 106A, a second section 106B, a third section 106C, and a fourth section 106D. The sections are connected in series with each other. A controller 108 is communicatively coupled to the drive coil 104 and the measurement coil 106. The controller 108 selectively energizes the drive coil 104 to generate a magnetic force and initiate movement of the elongated magnetic probe 102 towards the eye 110. Figure 1 shows the probe at position Z = 0. As an example, a first induced voltage can be measured for the first section 106A. Also, a common induced voltage across the first section 106A and the second section 106B can be measured. As another example, a first induced voltage may be measured for the second section 106B, and a common induced voltage may be measured, for example, as a voltage across all four sections. Indeed, the term "first section" may refer to any section. The common induced voltage may be measured from one or more sections different from at least the first section.

[0069] Referring to FIG. 2, a graph is shown depicting the relationship between position (in millimeters) of the magnetic probe 102 and the force (induced per ampere of current in the signal or drive coil) acting on the magnetic probe 102 in accordance with an embodiment of the present disclosure. The horizontal axis represents the magnetic force acting on the magnetic probe 102 induced for one ampere (A) of current through the measurement coil 106 and the drive coil 104. The vertical axis represents the position of the magnetic probe 102 in millimeters. Line 202 shows the magnetic force acting on the magnetic probe 102 due to the current through the measurement coil 106. Line 204 shows the magnetic force acting on the magnetic probe 102 due to the current through the drive coil 104. The upper curve 202 corresponds to a single signal coil used in the meter, and the lower curve 204 corresponds to the drive coil. The curves for the signal voltage induced by the probe moving at a constant speed through the coils appear similar.

[0070] Referring to FIG. 3, a graph 302 for determining the common induced voltage of the measurement coil 106 is shown according to an embodiment of the present disclosure. The common induced voltage is a function of time. At point 304, the common induced voltage increases when the drive coil 104 starts accelerating the elongated magnetic probe 102 (the acceleration of the magnetic probe 102 starts from position Z=0 mm). The magnetic probe 102 hits the surface of the eye 110 at point 306 (position Z=4 mm to 8 mm). The magnetic probe 102 then decelerates and becomes zero in about 1 ms, which is 20 milliseconds (ms) to 30 ms later. The magnetic probe 102 then bounces back. These depend on the velocity of the magnetic probe 102 and its distance from the surface of the eye 110. Here, the manner in which the velocity of the magnetic probe 102 changes during contact with the surface of the eye 110 depends mainly on the velocity of the magnetic probe 102 and also on the intraocular pressure through the pushing back force. The main parameter that depends on the intraocular pressure is given by the slope of the deceleration of the velocity of the magnetic probe 102. The deceleration of the velocity of the magnetic probe 102 is equal to the magnetic force between the magnetic probe 102 and the surface of the eye 110. The figure shows a measurement over a single section of the measurement coil. The drive coil is active for Z<1. The probe hits the eye with Z of about 5-7 mm. The drive force is then close to zero.

[0071] Figure 4 shows three locator signals, using four differential amplifiers to measure the voltage between each signal coil section. The curves in the figure are made by taking the signals from adjacent coils, i.e. first and second sections, second and third sections, third and fourth sections, subtracting them pairwise and dividing by the total U+ (common induced voltage) of all. All curves calculated in this way are independent of the speed and magnetization of the probe. By selecting from these curves, the probe can be localized over a large area. It is also possible to form appropriate linear combinations to optimize the sensitivity of the selected area. In this setup, four amplifiers / instruments must be synchronized to simultaneously sample each point on all four channels. The advantage of measuring multiple first induced voltage values ​​is increased accuracy.

[0072] Referring to FIG. 5, a graph for determining the position of the elongated magnetic probe 102 is shown according to an embodiment of the present disclosure. Here, the dependence of the velocity and magnetization of the magnetic probe 102 is removed by measuring the induced voltage U13 in one half section of the measurement coil (=U12+U23 in FIG. 9) and the induced voltage U35 in the other half section (=U34+U45). The signal ratio S is calculated as the difference U13-U34 divided by the common voltage Ucom of the whole coil. This signal ratio S represents the position of the elongated magnetic probe 102 and does not depend on the magnetization or the velocity of the probe. In FIG. 5, the horizontal axis represents the position of the elongated magnetic probe 102 in millimeters. The vertical axis represents the signal ratio S, which is a function of the probe position. Using two signal points S1 and S2 at times t1 and t2, the curve gives the corresponding z1 and z2. Using these signal points, the average velocity of the probe is calculated as vcal = (z1-z2) / (t1-t2). In this way, the position of the probe can be determined directly, and the velocity of the probe can be determined indirectly, independent of the magnetization of the probe.

[0073] In fact, without knowing the magnetization coefficient of the probe, it is possible to calibrate the magnetization effect and use it to derive the position and velocity of the probe.

[0074] Referring to FIG. 6, a measurement coil assembly 602 according to an embodiment of the present disclosure is shown. The measurement coil 602 is divided into a first section indicated by 602A, a second section indicated by 602B, a third section indicated by 602C, and a fourth section indicated by 602D. Further, a first coupling lead 604A is connected to the left end J1 of the first section 602A, and a second coupling lead 604B is connected to the connection J2 between the first section 602A and the second section 602B. A third coupling lead 604C is connected to the connection J3 between the second section 602B and the third section 602C, a fourth coupling lead 604D is connected to the connection J4 between the third section 602C and the fourth section 602D, and a fifth coupling lead 604E is connected to the right end J5 of the fourth section 602D. The length of the measurement coil 602 may be 20 millimeters (mm). The elongated magnetic probe 610 moves linearly with an accuracy 612 of 1 mm, where Z=0 is the starting position of the elongated magnetic probe 610. In this document, the following notations are generally used: U12 represents the induced voltage between connections J1 and J2; U16 represents the induced voltage between connections J1 and J5 (i.e. the voltage across all sections 602A, 602B, 602C and 602D); U34 represents the induced voltage between connections J3 and J4; U24 represents the induced voltage between connections J2 and J4, i.e. the induced voltage across the second section 602B and the third section 603 and C.

[0075] Referring to FIG. 7, a schematic diagram of a robotic system 700 for determining the velocity and position of an elongated magnetic probe 702 is shown according to one embodiment of the present disclosure. The robotic system comprises a linear screw 704 driven by a step motor 706. The linear screw 704 allows the elongated magnetic probe 702 to move linearly with high precision within a measurement coil 708. Furthermore, a first signal amplifier 710A and a second signal amplifier 710B are used to amplify the induced voltage of the measurement coil 708. The first signal amplifier 710A and the second signal amplifier 710B are electrically coupled to an oscilloscope 712. The elongated magnetic probe 702 is vibrated by a vibrator 714 at a frequency of 875 Hertz (Hz) to determine the velocity of the magnetic probe 702. The vibrator 714 is driven by a signal generator 716 via a third amplifier 718.

[0076] Referring to FIG. 8, an electric circuit 800 for summing induced voltages according to an implementation of the present disclosure is shown. A number of resistors R1, R2, R3, and R4 are shown. A first voltage input connected between the first and second sections of the measurement coil 708 is denoted as V1, a second voltage input connected to the end of the fourth section of the measurement coil 708 is denoted as V2, and a third voltage input connected between the third and fourth sections of the measurement coil 708 is denoted as V3. First, the first voltage input is the negative of the second induced voltage value, i.e., V1=-U2. Second, the second voltage input is the third induced voltage value plus the second induced voltage value, i.e., V2=U3+U4. Third, the third input corresponds to the third induced voltage, V3=U3. Finally, an output voltage is obtained, denoted as Vout. The output voltage is the sum of the first input, the second input, and the third input.

[0077] V out = V1+V2+V3 = -U2+U3+U4-U3 = U4-U2

[0078] The output voltage may be calculated for multiple resistors.

[0079] V1=(V1·R1 / (R1+R2)+V2·R1 / (R1+R2))(1+R4 / R3)-V3·R4 / R3

[0080] Referring to FIG. 9, the induced signal voltage in the measurement coil 602 is shown according to an implementation of the present disclosure. The vertical axis is twice the approximate root mean square value in millivolts. U12 shows the induced voltage obtained between the first coupling lead 604A and the second coupling lead 604B, U23 shows the voltage obtained between the second coupling lead 604B and the third coupling lead 604C, U34 shows the voltage obtained between the third coupling lead 604C and the fourth coupling lead 604D, and U45 shows the voltage obtained between the fourth coupling lead 604D and the fifth coupling lead 604E.

[0081] Referring to FIG. 10, a block diagram of a system 1000 for implementing an apparatus according to an exemplary implementation of the present disclosure is shown. A first amplifier 1002 is electrically coupled to the second section 1004B and the third section 1004C of the measurement coil 1004 to measure the induced voltages of the second section and the third section. The induced voltages of the second section and the third section are used as a first induced voltage value. A second amplifier 1006 is electrically coupled to the first section 1004A and the fourth section 1004D of the measurement coil 1004 to determine a common induced voltage. The probe is shown at a position Z=0. The probe can be moved by a driving coil 1040.

[0082] 11A and 11B, a graph is shown for achieving the optimal connection of the first amplifier 1002 of FIG. 10 and the second amplifier 1006 of FIG. 10 according to an implementation of the present disclosure. As shown in FIG. 10, the first amplifier 1002 is electrically coupled to the second and third sections of the measurement coil 1004. The second amplifier 1006 is electrically coupled to the first and fourth sections of the measurement coil 1004. In FIG. 11A, the common induced voltage, indicated by U15, is plotted alongside the induced voltages from the second and fourth sections, indicated by U24, for a vibrator voltage of 0.2 volts (V). Also shown is the division of U24 by U15 to find the optimal connection of the first amplifier 1002 and the second amplifier 1006. 11B plots the common induced voltage, designated U15, alongside the induced voltages from the second and fourth sections, designated U24, for a vibrator voltage of 0.3 volts. Also shown is U24 divided by U15 to find the optimum connection of the first amplifier 1002 and the second amplifier 1006.

[0083] FIG. 12A shows the first voltage values ​​U13 and U35 measured. FIG. 12B shows the signal voltages added together to represent the sum (U+) of the signal coil sections, and the difference (U-) of these signal voltages. Note that U+ is equal to U15. The different notation is to indicate that two or more measurement signals are added together to make the measurement. This is convenient for some purposes, such as to form the difference U. A minimal system would work like this. The signal coil has two sections, each with a differential amplifier, which produces the signals shown in FIG. 12A. Instead of forming the U- and U+ signals and their quotient (locator) (as in FIG. 12B), the zero crossing point of 4 mm can be used. If the time of this occurrence is measured, the average speed from 0 to 4 mm can be calculated.

[0084] 13A-13D, graphs are shown for measuring locator values ​​by adding multiple signal amplifiers according to an embodiment of the present disclosure. In FIG. 13A, line "Series 1" shows U13, which is the induced voltage in the measurement coil 602 between the first coupling lead 604A and the third coupling lead 604C. Line "Series 2" shows U35, which is the induced voltage in the measurement coil 602 between the third coupling lead 604C and the fifth coupling lead 604E. Line "Series 3" shows U+, the sum of the output signal from the first signal amplifier and the output signal from the second signal amplifier. U- is the difference between the output from the first signal amplifier and the output from the second signal amplifier. FIG. 13B provides locator values ​​for U+ and U-. The locator signal is generated by dividing U- by U+. FIG. 13A and FIG. 13B also provide data with a long sweep of Z values. Similarly, Figure 13C provides data from a range of induced voltage values ​​that are used to fit the trend line, and Figure 13D shows the locator values ​​for U+ and U-.

[0085] 14A and 14B, a flow chart showing steps of a method for determining a physiological parameter according to an embodiment of the present disclosure is shown. In step 1402, a drive coil is energized to move the elongated magnetic probe in the direction of a first end of the elongated magnetic probe. In step 1404, an induced first voltage is measured as a function of time using a first section of the measurement coil. In step 1406, an induced common voltage is measured as a function of time across the measurement coil. In step 1408, a first locator value is determined as a function of time by dividing the measured induced first voltage value by the respective measured induced common voltage value. In step 1410, the first locator value is mapped from the time domain to the spatial domain. In step 1412, the first locator value in the spatial domain is used to calculate a first velocity profile of the elongated magnetic probe. In step 1414, the first velocity profile is used to determine a physiological parameter.

[0086] FIG. 15 is an illustration of measured and calculated values ​​as a function of probe travel (Z-axis from 0 to 10 mm). Locator 1500 is formed by taking the ratio of the U- and U+ signals shown in FIG. 12B. The derivative curve 1510 of locator 1500 is the point increment divided by the step length (1 mm). (Derivative curve 1510 is multiplied by -4 to make FIG. 15 easier to read). The inverse of derivative curve 1520 is the first velocity profile as a function of distance, in mm.

[0087] The embodiments of the present disclosure described above can be modified without departing from the scope defined by the appended claims. The terms "including," "comprising," "incorporating," "having," "being," and the like used to describe and claim the present disclosure are intended to be interpreted in a non-exclusive manner, i.e., to allow for the presence of items, parts, or components not expressly described. The absence of a plurality of elements does not preclude the presence of a plurality of the elements.

Claims

1. 1. An apparatus for determining a physiological parameter, the apparatus comprising: an elongated magnetic probe having a first end, a second end opposite the first end, and an intermediate portion between the first end and the second end; a drive coil disposed to partially surround the magnetic probe; a measurement coil having at least a first section and a second section, the measurement coil being positioned to partially surround the magnetic probe; A controller; The controller comprises: selectively energizing the drive coil to generate a magnetic force to initiate movement of the magnetic probe toward the first end; measuring a first induced voltage value and a common induced voltage value as a function of time during movement of the magnetic probe, the first induced voltage value being a voltage across the first section and the common induced voltage value being a voltage value across the first section to the second section or across at least one of the second sections; determining a locator value as a function of time by dividing the first induced voltage value by the common induced voltage value; mapping the locator values ​​from the time domain to the spatial domain as a function of time; calculating a first velocity profile of the magnetic probe from spatial domain locator values ​​and determining a physiological parameter using the calculated first velocity profile; configured to carry out Device.

2. 2. The apparatus of claim 1, wherein the measurement coil is used as a drive coil for a first period of time and is used as a second section of the measurement coil for a second period of time after the first period of time.

3. In use, a first section of the measurement coil surrounds a first section of the magnetic probe and a second section of the measurement coil surrounds a second section of the magnetic probe; The apparatus of claim 1 , wherein the first section of the magnetic probe is different from the second section of the magnetic probe when the magnetic probe is in its first spatial position.

4. 4. The apparatus of claim 3, wherein, in use, when the magnetic probe is in its second spatial position, the first section of the measurement coil does not surround the first section of the magnetic probe and the second section of the measurement coil surrounds the second section of the magnetic probe, but the second spatial position is different from the first spatial position.

5. The apparatus of claim 1 , wherein the mapping from the time domain to the spatial domain is performed by at least one of a pre-determined transfer function or a look-up table.

6. The apparatus of claim 1 , wherein the first section of the measurement coil and the second section of the measurement coil are connected in series.

7. 2. The apparatus of claim 1, wherein the measurement coil has a third section, the third section being connected in series with the first and second sections of the measurement coil and disposed to surround the third section of the magnetic probe.

8. The apparatus of claim 1, wherein the common induced voltage value is measured across all sections of the measuring coil.

9. The controller: measuring a second induced voltage value from a section other than the first section as a function of time during the travel time of the magnetic probe; determining a second locator value as a function of time by dividing the second induced voltage value by the common induced voltage value; Mapping the second locator function from the time domain to the spatial domain; calculating a second velocity profile of the magnetic probe from second locator values ​​in the spatial domain; updating a physiological parameter using the calculated second velocity profile; The apparatus of claim 1 configured to:

10. The apparatus of claim 1 , wherein the first velocity profile includes at least one of a velocity in the spatial domain and a velocity in the time domain.

11. The apparatus of claim 9 , wherein the second velocity profile includes at least one of a velocity in the spatial domain and a velocity in the time domain.

12. 12. The device according to any one of claims 1 to 11, which is a tonometer.

13. 1. A method for determining a physiological parameter, comprising: energizing a drive coil to move an elongated magnetic probe toward a first end of the magnetic probe; measuring a first induced voltage as a function of time for a first section of the measurement coil; measuring an induced common voltage as a function of time, the voltage across the first section of the measurement coil and the second section of the measurement coil or across the second section; determining a first locator value as a function of time by dividing the measured first induced voltage value by the measured common induced voltage value; mapping the first locator value from the time domain to the spatial domain; calculating a first velocity profile of the magnetic probe from first locator values ​​in a spatial domain; determining a physiological parameter using the first velocity profile; A method comprising:

14. The method of claim 13 , wherein the magnetic probe is urged to move towards the patient and bounce off a surface of the patient's body.

15. The method of claim 13, wherein measurements are taken during movement of the magnetic probe to obtain induced voltage values ​​as a function of time.

16. 14. The method of claim 13, wherein the physiological parameter is determined by at least one of analysis of acceleration during impact of the magnetic probe on the patient's body surface, change in velocity before and after impact, and penetration of an elongated magnetic probe into the body surface.

17. 17. The method according to any one of claims 13 to 16, wherein the physiological parameter is: measuring a second induced voltage value as a function of time in a section of the measuring coil different from the first section; determining a second locator value as a function of time by dividing the second induced voltage value by the common induced voltage value; Mapping a second locator function from the time domain to the spatial domain; calculating a second velocity profile of the elongated magnetic probe as a function of position from the second locator values ​​in the spatial domain; updating the physiological parameter using the calculated second velocity profile; Updated by,method.

18. The method of claim 13 , wherein the first velocity profile includes at least one of a velocity in the spatial domain and a velocity in the time domain.

19. The method of claim 17 , wherein the second velocity profile includes at least one of a velocity in the spatial domain and a velocity in the time domain.

Images