Patent Description:
Tissue sensors having a plurality of ultrasonic transducers operable to emit and receive ultrasonic signals may be used to provide information regarding the tissue being sensed. In some applications, the information produced is sensitive to the relative positions and/or orientations of the ultrasonic transducers. A sensor that is pliable to conform to a subject's tissue can be bent from an initial/default orientation when attached to the subject, and the relative positions and/or orientations of the ultrasonic transducers changed from the initial/default orientation. Since the information derived from the sensor may be a function of the relative positions and/or orientations of the ultrasonic transducers, unknown deviations from the planar orientation can introduce undesirable error into the information.

What is needed is a system and method that is capable of determining the actual relative positions and/or orientations of the ultrasonic transducers, and that can account for the same as necessary.

<CIT> describes an ultrasound apparatus comprising a plurality of ultrasound transducers for emitting and receiving ultrasound waves and for providing different ultrasound signals on the basis of the ultrasound waves. A connection layer is provided, which is attachable to the subject, wherein the ultrasound transducers are coupled to the connection layer. A processing unit is adapted to determine at least one parameter indicative of a relative position of the ultrasound transducers to each other and/or a shape of the connection layer.

According to an aspect of the present disclosure useful for understanding the presently claimed invention, a biomedical sensor is provided that includes a deformable body panel, at least one first ultrasonic transducer, at least one second ultrasonic transducer, and at least one displacement sensor. The at least one first ultrasonic transducer and the at least one second ultrasonic transducer are attached to the deformable body panel. The at least one displacement sensor is in communication with the deformable body panel. The biomedical sensor is disposable in at least one default configuration wherein the at least one first ultrasonic transducer and the at least one second ultrasonic transducer are disposed relative to one another in a known first spatial transducer configuration. The biomedical sensor is disposable in one or more deformed configurations wherein the at least one first ultrasonic transducer and the at least one second ultrasonic transducer are disposed relative to one another in a second spatial transducer configuration different than the known first spatial transducer configuration. The at least one displacement sensor is configured to produce signal information indicative of a difference between the known first spatial transducer configuration and the second spatial transducer configuration.

In any of the aspects or embodiments described above and herein, the at least one displacement sensor may include a plurality of displacement sensors configured to sense a difference between relative positions of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the known first spatial transducer configuration, and the relative positions of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the one or more deformed configurations.

In any of the aspects or embodiments described above and herein, the plurality of displacement sensors may be configured to sense a difference between relative orientations of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the known first spatial transducer configuration, and relative orientations of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the one or more deformed configurations.

In any of the aspects or embodiments described above and herein, the biomedical sensor may further include a processor chip in communication with the plurality of displacement sensors.

In any of the aspects or embodiments described above and herein, the at least one displacement sensor may include a plurality of displacement sensor cells, each having a plurality of displacement sensors, the plurality of displacement sensor cells spaced apart from one another and attached to the deformable body panel.

In any of the aspects or embodiments described above and herein, the at least one displacement sensor may include interdigital elements configured to sense bending of the sensor, or buckling of the sensor, or both.

In any of the aspects or embodiments described above and herein, the biomedical sensor may be configured to assume the at least one default configuration in the absence of external forces acting on the sensor.

In any of the aspects or embodiments described above and herein, the deformable body panel may be a solid body.

According to another aspect of the present disclosure, a biomedical system is provided that includes at least one biomedical sensor as described above and herein, and a controller. The controller in communication with the at least one biomedical sensor and a memory storing instructions, which instructions when executed cause the controller to: a) determine the difference between the known first spatial transducer configuration and the second spatial transducer configuration using the signal information from the at least one displacement sensor; and b) produce information representative of the relative positions of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the one or more deformed configurations using the determined difference.

In any of the aspects or embodiments described above and herein, the instructions when executed may cause the controller to produce information representative of the relative orientations of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the one or more deformed configurations using the determined difference.

In any of the aspects or embodiments described above and herein, the instructions when executed cause the controller to produce information relating to blood vessel diameter, or pulse wave velocity, or both, using the information representative of the relative positions of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the one or more deformed configurations.

According to another aspect of the present disclosure useful for understanding the presently claimed invention, a method of using a deformable biomedical sensor is provided. The method includes: a) providing a biomedical sensor having a deformable body panel, at least one first ultrasonic transducer attached to the deformable body panel, at least one second transducer attached to the deformable body panel, and at least one displacement sensor in communication with the deformable body panel, wherein the at least one biomedical sensor is disposable in at least one default configuration wherein the at least one first ultrasonic transducer and the at least one second ultrasonic transducer are disposed relative to one another in a known first spatial transducer configuration; b) attaching the biomedical sensor to a subject's skin in an applied configuration, wherein in the applied configuration the at least one first ultrasonic transducer and the at least one second ultrasonic transducer are disposed relative to one another in a second spatial transducer configuration; c) using the at least one displacement sensor to determine any difference between the first spatial transducer configuration and the second spatial transducer configuration; and d) producing information representative of the relative positions of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the one or more deformed configurations using the determined difference.

In any of the aspects or embodiments described above and herein, the step of producing information representative of the relative positions of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer may include producing information representative of the relative orientations of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the second spatial transducer configuration, or the relative positions of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the known first spatial transducer configuration, and relative positions of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the second spatial transducer configuration.

In any of the aspects or embodiments described above and herein, the method may further include producing information relating to blood vessel diameter, or pulse wave velocity, or both, using the information representative of the relative orientations of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the applied configuration, or the information representative of the relative positions of the at least one first ultrasonic transducer and the at least one second ultrasonic transducer within the applied configuration, or both.

Referring to <FIG>, aspects of the present disclosure include a biomedical sensor <NUM> that may be worn by a subject, a system <NUM> for non-invasively sensing tissue using one or more biomedical sensors <NUM>, and a method for non-invasively sensing tissue using one or more biomedical sensors <NUM>. As described herein, the biomedical sensor <NUM> includes a plurality of ultrasonic transducers <NUM> (e.g., see <FIG>) and is configured to sense the relative positions and/or orientations of the ultrasonic transducers <NUM>. The biomedical sensor <NUM> may be described as having a "default" configuration wherein the relative positions and/or orientations of the ultrasonic transducers <NUM> are known. A default configuration for a biomedical sensor <NUM> may be the configuration the sensor <NUM> assumes in the absence of any forces acting on the sensor <NUM>, but the present disclosure is not limited to a default configuration being the sensor "at rest" configuration. A biomedical sensor <NUM> may have one or more alternative default configurations wherein the relative positions and/or orientations of the ultrasonic transducers <NUM> are known. Alternatively, the present disclosure system may be configured to determine displacement sensor <NUM> values in a first configuration (which may then be considered to be the default configuration) and then sense deformation of the biomedical sensor <NUM> from that first configuration based on input from the deformation sensors <NUM>. If the biomedical sensor <NUM> is deformed into a configuration other than the default configuration (e.g., bent or stretched when applied to a tissue surface), the sensor <NUM> is configured to sense the relative positions and/or orientations of the ultrasonic transducers <NUM> in the deformed configuration (e.g., deviations from the default configuration) and provide information regarding the same. The system <NUM> includes the one or more biomedical sensors <NUM> and a controller <NUM>. <FIG> diagrammatically illustrates a present disclosure system <NUM> with a plurality of biomedical sensors <NUM> disposed on a subject, which sensors <NUM> are in communication with a controller <NUM>.

The controller <NUM> is in signal communication with the biomedical sensor(s) <NUM> to perform the functions described herein. The controller <NUM> may include any type of computing device, computational circuit, processor(s), CPU, computer, or the like capable of executing a series of instructions that are stored in memory. The instructions may include an operating system, and/or executable software modules such as program files, system data, buffers, drivers, utilities, and the like. The executable instructions may apply to any functionality described herein to enable the system <NUM> to accomplish the same algorithmically and/or coordination of system <NUM> components. The controller <NUM> may include a single memory device or a plurality of memory devices. The present disclosure is not limited to any particular type of non-transitory memory device, and may include read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. The controller <NUM> may include, or may be in communication with, an input device that enables a user to enter data and/or instructions, and may include, or be in communication with, an output device configured, for example to display information (e.g., a visual display or a printer), or to transfer data, etc. Communications between the controller <NUM> and other system components may be via a hardwire connection or via a wireless connection.

Each biomedical sensor <NUM> includes a plurality of ultrasonic transducers <NUM>, at least one displacement sensor <NUM>, and a body panel <NUM>. Each ultrasonic transducer <NUM> is configured to both transmit and receive ultrasonic signals; e.g., an ultrasonic transducer <NUM> may include one or more elements that both transmit and receive ultrasonic signals, or may include one or more elements dedicated to transmitting ultrasonic signals and one or more elements dedicated to receiving ultrasonic signals. In those instances wherein an ultrasonic transducer includes a plurality of elements, those elements may be arranged in an array. The ultrasonic transducers <NUM> may be configured for two-way signal communication with the controller <NUM> via hard wire or by wireless means. The term "ultrasonic signals" as used herein refers to the mechanical pressure waves produced and/or received by the ultrasonic transducer <NUM>, which pressure waves are sometimes referred to as pressure waves, sound waves, sound pulses, acoustic waves, or the like. The ultrasonic transducers <NUM> are configurable to produce the ultrasonic signals at one or more predetermined frequencies and wavelengths; e.g., typically within the range of <NUM>-<NUM>. Non-limiting examples of acceptable ultrasonic transducer <NUM> types include transducers having piezoelectric elements; e.g., PZT (lead zirconate titanate) based transducers, CMUT (capacitive micromachine) transducers, PMUT (piezoelectric micromachine) transducers, and like devices operable to transform mechanical energy into electrical energy and vice versa.

When the biomedical sensor <NUM> is disposed in a default configuration, the plurality of ultrasonic transducers <NUM> are disposed in a geometric configuration wherein the relative positions and/or orientations of the transducers <NUM> are known. For example, in some embodiments the ultrasonic transducers <NUM> may be disposed in a two-dimensional (2D) array. An example of such an array is shown in <FIG>; e.g., a transducer <NUM> array having one column (C<NUM>) and two rows (R<NUM>, R<NUM>), wherein the distance between the rows is known. In the default configuration, the distance between rows may be uniform. Another example of a two dimensional transducer <NUM> array configuration is shown in <FIG>, which array includes a plurality of columns and a plurality of rows; e.g., "N" number of columns (C<NUM>, C<NUM>, C<NUM>. CN), with each column having "M" number of rows (R<NUM>. RM), where "N" and "M" are integers. Here again, the intercolumn distances and the interrow distances are known. In the default configuration, the distances between transducers in a column may be uniform, and the distance between transducers in a row may be uniform. <CIT>, entitled "System and Method for Non-Invasively Sensing a Blood Vessel", assigned to the present applicant, discloses biomedical sensor <NUM> configurations like those described above. As indicated above, the above-described ultrasonic transducer <NUM> array configurations are examples of 2D transducer <NUM> configurations wherein the relative positions and/or orientations are known when the biomedical sensor <NUM> is disposed in its default configuration; e.g., the position of the ultrasonic transducers <NUM> may be described in terms of "X" and "Y" coordinates, where X and Y are orthogonal axes defining an X-Y plane. The present disclosure is not limited to these examples. For example, a biomedical sensor <NUM> may have a three-dimensional (3D) default configuration; e.g., the relative positions and/or orientations of the ultrasonic transducers <NUM> are known and describable in terms of X, Y, and Z orthogonal axes. To be clear, the geometric configuration of ultrasonic transducers <NUM>, where the relative positions and/or orientations of the transducers <NUM> is known refers to ultrasonic transducers that may include a plurality of elements as described above. However, if an individual ultrasonic transducer <NUM> does include an array of elements and the relative positions and/or orientations of the elements within the transducer <NUM> are known, then the present disclosure may be utilized to determine position and/or orientation changes between elements within a transducer <NUM>.

Each ultrasonic transducer <NUM> may be described as having an active area. The active area is the surface of the transducer <NUM> from which ultrasonic signals emanate and/or are accepted or received. The ultrasonic transducers <NUM> that are used within the present disclosure are not limited to any particular active area configuration; e.g., circular, oblong, etc..

The ultrasonic transducers <NUM> may be configured to project ultrasonic signals in a variety of different configurations, and the present disclosure is not limited to any particular configuration. For description purposes herein, the ultrasonic signals projected by each ultrasonic transducer <NUM> will be described as being projected in the form of an incident beam having an intensity profile that is a function of the angle between the direction of interest and the central axis that extends out normal to the active surface of the transducer <NUM> and is centered on the latter. This intensity profile can take a plurality of shapes determined by the size and excitation of the active surface. Preferably, ultrasonic transducers used with the present disclosure have a profile that maximizes the detection of the features of interest. Examples of such profiles may include plane wave approximations, pencil beams, raised cosines and the like. In some applications, the ultrasound transducers <NUM> may be operated to produce an incident beam of ultrasonic signal configured to permit the features of a blood vessel (e.g., the posterior and anterior walls of an artery) to be identified and located relative to one another. The ultrasonic transducers <NUM> may be operated to produce the aforesaid ultrasonic signals a plurality of times during a cardiac cycle. The ultrasonic signals that form the incident beam reflect off of elements within the tissue, including the anterior and posterior walls of the artery being investigated. The reflected ultrasonic signals reflect back towards and are sensed by the ultrasonic transducers <NUM>. The ultrasonic transducers <NUM>, in turn, produce electronic signals that are communicated to the controller <NUM>. The features within the reflected signals that correspond to the anterior and posterior walls of the artery may be extracted from all of the reflected signals by the controller <NUM> using stored instructions. The reflected ultrasonic signals that correspond to the anterior and posterior walls of the artery permit the determination of useful physiologic information; e.g., arterial diameter, pulse wave velocity, etc..

The body panel <NUM> is configured to maintain the ultrasonic transducers <NUM> in a default configuration when no forces are applied to the body panel <NUM>. For example, the body panel <NUM> may be configured to maintain the ultrasonic transducers in a 2D planar default configuration wherein the positions of the ultrasonic transducers <NUM> (e.g., X<NUM>,Y<NUM>; X<NUM>, Y<NUM>, etc.) are known and the orientation of each transducer <NUM> is known (e.g., the orientation of the beam projected by the transducer <NUM> is known). The body panel <NUM> is sufficiently deformable (e.g., flexible and/or stretchable) to permit the biomedical sensor <NUM> to sufficiently deform from its default configuration to conform to the subject's skin surface. The body panel <NUM> may be elastically or plastically deformable. In some embodiments, the body panel <NUM> may be a solid body, and may have cavities or apertures for receiving components (e.g., ultrasonic transducers <NUM>, displacement sensors <NUM>, circuitry, etc.) The present disclosure is not, however, limited to a body panel <NUM> having a solid body. The term "solid body" is used herein to describe a body without substantial cavities or apertures, other than those that may be used for components. A solid body may be formed from a sponge or foam material that inherently includes some voids. A solid body may be formed with a homogeneous material, or a non-homogeneous material; e.g., a laminate structure. As an alternative to a solid body, the body panel <NUM> may include a deformable frame <NUM> (e.g., See <FIG>) operable to maintain the ultrasonic transducers <NUM> in the default configuration. An example of a solid body base panel material is one comprising a silicone elastomeric material. The present disclosure is not, however, limited to any particular base panel <NUM> material or configuration. In some embodiments, the biomedical sensor <NUM> may be described as having rigid regions <NUM> where the ultrasonic transducers <NUM> reside, and one or more deformable regions <NUM> disposed between the rigid regions <NUM>. <FIG> illustrates an example of a biomedical sensor <NUM> that has a first ultrasonic transducer 26A (or array of ultrasonic transducers <NUM>) disposed in a first rigid region 32A, a second ultrasonic transducer 26B (or array of ultrasonic transducers <NUM>) disposed in a second rigid region 32B, and a deformable region <NUM> disposed between and connecting the first and second rigid regions 32A, 32B. In some embodiments, an adhesive is disposed on at least portions of the body panel <NUM>. The adhesive can be any medical grade adhesive that is safe for skin surfaces, and adequate to maintain the ultrasonic transducers <NUM> in contact with the subject's skin. In those embodiments where the biomedical sensor <NUM> has rigid regions <NUM> with ultrasonic transducers <NUM>, the rigid regions <NUM> may include an adhesive to maintain the ultrasonic transducers <NUM> in contact with the subject's skin. The present disclosure is not limited to using an adhesive to attach the biomedical sensor <NUM> to a skin surface; e.g., mechanical fastening systems, or the like may be used. For example, the body panel may be sufficiently stretchable so as to produce a self-adherent effect to the subject's skin.

The displacement sensors <NUM> are configured to sense and produce information regarding the magnitude and/or orientation of displacement of ultrasonic transducers <NUM> from their default positions within the biomedical sensor <NUM>. The term "displacement" as used herein refers to any change in position and/or orientation of one or more ultrasonic transducers <NUM> from at least one other transducer <NUM>. For example, and as described herein, a first transducer may be longitudinally separated from a second transducer by a distance "L" when the biomedical sensor <NUM> is in a default position, and may be displaced by the distance "L+D" when the biomedical sensor <NUM> is subjected to longitudinal stress. In this example, and assuming the displacement is purely longitudinal, the magnitude of the displacement is the distance "D". As another example, assume a biomedical sensor <NUM> has a planar default configuration (e.g., the body panel resides in an X-Y plane) and each transducer <NUM> projects a signal profile that is centered along an axis perpendicular to the planar body panel <NUM> (e.g., along a Z axis). If the biomedical sensor <NUM> is subjected to torsional strain, the separation distance between the first and second transducers <NUM> may remain substantial equal to the default separation distance "L", but the orientation of the transducer signal profile of the first transducer may be angularly skewed from that of the second transducer or vice versa; e.g., the signal profile of one or both the first and second transducers may no longer be centered along the Z axis. In this instance, the displacements sensors are operable to sense any change in the angular orientation of a transducer that would result in the signal profile from that respective ultrasonic transducer <NUM> deviating from its orientation in the default configuration. These simplistic displacement examples are provided for illustrative purposes. In many applications, a biomedical sensor <NUM> may be deformed in such a manner that displacement occurs in three dimensions, and/or may include orientation changes of pitch, roll, or yaw, or any combination thereof - and the displacement sensors <NUM> are configured to detect such displacement. The aforesaid information may be provided to the controller <NUM> in the form of electronic signals representative of the displacement, or a determinable change in a property (e.g., a change in capacitance, resistance, conductivity, or the like) that is representative of the displacement. The present disclosure may utilize a variety of different displacement sensor <NUM> types such as, but not limited to, strain sensors, capacitive sensors, conductive/resistive sensors, etc. A biomedical sensor <NUM> may include a plurality of the same type of displacement sensor <NUM>, or may include different types of displacement sensors <NUM>. To be clear, the displacement sensor(s) <NUM> are configured to sense and produce information regarding the displacement of ultrasonic transducers <NUM> (or in some instances elements within a transducer) from their default positions within the biomedical sensor <NUM>, and the term "displacement" refers to any change in position and/or orientation between at least two transducers <NUM> (or elements). The aforesaid transducers <NUM> may be individual transducers <NUM>, or a first transducer <NUM> within a first array and a second transducer <NUM> in a second array, or first and second transducers <NUM> within an array, or elements within a transducer <NUM>, at least one of which is displaced from its default position, and therefore displaced relative to the aforesaid second transducer (or element).

<FIG> diagrammatically illustrate a biomedical sensor <NUM> embodiment in its default location (<FIG>), and the same biomedical sensor <NUM> subjected to a number of different deformation types to illustrate how displacement sensors <NUM> may be utilized to sense and produce information regarding the magnitude and/or orientation of ultrasonic transducer <NUM> displacement from their default positions. The biomedical sensor <NUM> shown in <FIG> includes a first strain sensor 28A disposed between points A and B (e.g., extending in a lengthwise direction), a second strain sensor 28B disposed between points C and D (e.g., extending in a lengthwise direction), a third strain sensor 28C disposed between points A and D (e.g., extending in a widthwise direction), a fourth strain sensor 28D disposed between points B and C (e.g., extending in a widthwise direction), a fifth strain sensor 28E extending between points A and C, diagonal to the lengthwise and widthwise directions, and a sixth strain sensor 28F extending between points B and D, diagonal to the lengthwise and widthwise directions. <FIG> diagrammatically illustrates the biomedical sensor <NUM> subjected to longitudinal strain. <FIG> diagrammatically illustrates the biomedical sensor <NUM> subjected to shear strain. <FIG> diagrammatically illustrates the biomedical sensor <NUM> subjected to torsional strain. <FIG> diagrammatically illustrates the biomedical sensor <NUM> subjected to bending and/or buckling. The configuration of displacement sensors 28A-28F shown in <FIG> is provided to facilitate the description herein, and the present disclosure is not limited to this particular configuration of displacement sensors <NUM>.

<FIG> illustrate some, but not all, fundamental deformation types that a biomedical sensor <NUM> may be subjected to during application to and/or use on a subject. The displacement sensors <NUM> are preferably configured so that the collective signal information from the respective displacement sensors <NUM> permits both the type of the deformation to be identified, and the magnitude of the deformation to be measured. This information in turn, permits substantially any change in the position and/or orientation of the ultrasonic transducers <NUM> from the default position to be determined. In the longitudinal deformation shown in <FIG>, for example, the longitudinally disposed displacement sensors (i.e., the first strain sensor 28A, A-B and the second strain sensor 28B, C-D) will sense longitudinal stretching. Because of the orthogonal-like configuration of the displacement sensors 28A-28F, however, the longitudinally disposed displacement sensors 28A, 28B are not the only displacement sensors to sense strain; e.g., the diagonally oriented displacement sensors (fifth strain sensor 28E, A-C, sixth strain sensor 28F, B-D) also sense strain, albeit at a different rate than the longitudinal displacement sensors 28A, 28B. The controller <NUM> is adapted to receive the displacement sensor signals collectively and determine the type and magnitude of the biomedical sensor <NUM> deformation, and consequent displacement of the ultrasonic transducers <NUM>. <FIG> diagrammatically illustrate the sensed strain contributions from the various displacement sensors <NUM> for a biomedical sensor <NUM> in its default configuration (<FIG>), a biomedical sensor <NUM> subjected to longitudinal strain (<FIG>), and a biomedical sensor <NUM> subjected to shear strain (<FIG>). The strain versus time graph shown in <FIG> depicts the sensed strain contributions of all of the displacement sensors <NUM> at a baseline value in the absence of deformation. The strain versus time graph shown in <FIG> depicts the sensed strain contributions of the longitudinally disposed displacement sensors (i.e., the first strain sensor 28A, A-B and the second strain sensor 28B, C-D) as sensing a greater amount of strain than the diagonally oriented displacement sensors (fifth strain sensor 28E, A-C, sixth strain sensor 28F, B-D) and the widthwise disposed displacement sensors (third strain sensor 28C, A-D, fourth strain sensor 28D, B-C). The strain versus time graph shown in <FIG> depicts the sensed strain contribution of a diagonally oriented displacement sensors (sixth strain sensor 28F, B-D) as sensing a greater amount of strain than the longitudinally disposed displacement sensors (first strain sensor 28A, A-B, second strain sensor 28B, C-D), and the widthwise disposed displacement sensors (third strain sensor 28C, A-D, fourth strain sensor 28D, B-C), and the other diagonally oriented displacement sensor (fifth strain sensor 28E, A-C). In each of these instances, the collective signals from all of the displacement sensors <NUM> are communicated to the controller <NUM>, and the controller <NUM> in turn uses the aforesaid signals to determine the type and magnitude of the biomedical sensor <NUM> deformation, and consequent displacement of the ultrasonic transducers <NUM>.

As stated above, the displacement sensor <NUM> configuration shown in <FIG> is a non-limiting example provided to facilitate the description herein. The description above makes clear that all of the displacement sensors <NUM> are likely to sense some amount of strain (e.g., caused by elongation or contraction) in most deformations of the biomedical sensor <NUM> and that the collective strain signals from the respective displacement sensors <NUM> can be used to determine the type and magnitude of the biomedical sensor <NUM> deformation, and consequent displacement of the ultrasonic transducers <NUM>. Other types of deformation (e.g., certain buckling and/or bending modes), however, may not cause displacement sensor <NUM> elongation or contraction. As will be described herein, some displacement sensor <NUM> configurations include one or more deformation sensors <NUM> that are sensitive to bending or buckling deformation.

<FIG> illustrate non-limiting examples of displacement sensor <NUM> types that may be used with the present disclosure. The displacement sensor <NUM> types may be classified as symmetric (insensitive to bending and/or buckling convexity - e.g., <FIG>) and asymmetric (sensitive to bending and/or buckling convexity - e.g., <FIG>).

<FIG> diagrammatically illustrates a capacitive displacement strain sensor <NUM> embodiment. The horizontal surfaces 36A, 36B of the sensor <NUM> are electrically conductive. Under sufficient longitudinal stress, the displacement strain sensor <NUM> stretches horizontally, and typically shrinks vertically due to the Poisson effect. As a result, the distance between the horizontal surfaces 36A, 36B is reduced and that alters the capacitance of the displacement sensor <NUM>. Displacement information may be produced by a direct measurement of the capacitance of the displacement sensor <NUM> via current and voltage values associated with the sensor <NUM>. Alternatively, displacement information may be produced by measuring the resonance frequency of a circuit that includes the capacitive displacement sensor <NUM>.

<FIG> diagrammatically illustrates a displacement strain sensor <NUM> embodiment having a pair of interwoven isolated conductors 38A, 38B that may offer a substantially greater strain dynamic range. The pair of conductors 38A, 38B have a characteristic impedance. Longitudinal stress alters the pattern of the conductors 38A, 38B and therefore its characteristic impedance. The aforesaid changes in impedance can be used to produce displacement information.

<FIG> diagrammatically illustrate a displacement strain sensor <NUM> embodiment that includes interdigital elements <NUM>. The capacitance of the sensor <NUM> is related to the distance between adjacent interdigital elements <NUM>. Hence, the capacitance of the sensor <NUM> can be altered by changing the interdigital element <NUM> spacing. This type of displacement sensor <NUM> is substantially sensitive to shear strain, but also to longitudinal stress in both the vertical and horizontal dimensions of the plane of the displacement sensor <NUM>. <FIG> illustrates the displacement strain sensor <NUM> in a normal state (no forces applied). <FIG> illustrate the displacement strain sensor <NUM> with a shear stress load applied (e.g., longitudinal force - shown horizontally). <FIG> illustrates the displacement strain sensor <NUM> with a shear stress load applied (e.g., lateral force - shown vertically).

<FIG> diagrammatically illustrates an electrically conductive/resistive displacement strain sensor <NUM>. An applied longitudinal force of sufficient magnitude will alter the cross-sectional area and length of the sensor <NUM>, which results in a change of the intrinsic electrical resistance/conductivity of the displacement strain sensor <NUM>.

<FIG> diagrammatically illustrate a capacitive strain sensor <NUM> with interdigital elements <NUM> affixed at one common side. As indicated above, this type of displacement strain sensor <NUM> may be described as being asymmetric and is substantially sensitive to bending and/or buckling and can discriminate between convex and concave bending and/or buckling. <FIG> illustrates a first mode of bending where adjacent interdigital elements <NUM> are angled toward one another at an angle α<NUM> due to the bending mode. <FIG> illustrates a second mode of bending where the adjacent interdigital elements <NUM> are angled away from one another at an angle α<NUM> due to the bending mode, where α<NUM> is greater than α<NUM>. The aforesaid changes in interdigital element <NUM> orientation between adjacent interdigital elements <NUM> changes the capacitance of the sensor, which in turn can be used to produce displacement information.

In some embodiments, a displacement sensor <NUM> may include a plurality of rigid, non-stretchable strain sensors <NUM> operable to provide information regarding convex and concave bending of the biomedical sensor <NUM>. For example, <FIG> diagrammatically illustrate a displacement sensor <NUM> embodiment having rigid islands of non-stretchable strain sensors <NUM> in communication with one another. <FIG> diagrammatically illustrates the displacement sensor <NUM> with no load applied, and <FIG> diagrammatically illustrates the displacement sensor <NUM> with a longitudinal load applied.

Present disclosure biomedical sensors <NUM> may be attached to a variety of locations on a subject, such as but not limited to, a leg (proximal to the femoral artery), the abdomen (proximal to the descending aorta artery), and others. To illustrate the utility of the displacement sensors <NUM> in a particular biomedical sensor <NUM> application, <FIG> diagrammatically illustrate a biomedical sensor <NUM> (e.g., like that diagrammatically shown in <FIG>) attached to a subject's arm; e.g., to sense a brachial artery. When attached to the subject's arm and the arm is in a first position (e.g., extended as shown in <FIG>), the biomedical sensor <NUM> will initially be in its default configuration; e.g., as shown in <FIG>. When the subject changes arm position (e.g., as shown in <FIG>), the biomedical sensor <NUM> can be subject to longitudinal stress that causes the biomedical sensor <NUM> to stretch lengthwise / longitudinally; e.g., subjecting the biomedical sensor <NUM> to longitudinal strain as shown in <FIG>. This deformation of the biomedical sensor <NUM> can cause a positional displacement between ultrasonic transducers <NUM>; e.g., first transducer 26A and second transducer 26B displaced by distance "L" in a default position, and in a deformed configuration are displaced by "L+D", where L+D is greater than L. The change in separation distance between the first and second transducer 26A, 26B (i.e., L vs. L+D) - if unaccounted for - can lead to an error in some physiologic parameters based on the ultrasonic transducer <NUM> signals. Using the present disclosure, however, displacement sensors <NUM> disposed in the biomedical sensor <NUM> provide signal information regarding the amount of transducer <NUM> displacement from L to L+D to the controller <NUM>.

An example of the importance being able to determine a change in the relative positions of the ultrasonic transducers <NUM> is evident when the biomedical sensor <NUM> is used to determine a physiologic parameter such as pulse wave velocity (PWV). PWV measurements are a function of the distance traversed by the pulse wave within the blood vessel. The distance between the ultrasonic transducers <NUM> within a biomedical sensor <NUM> is therefore critical in determining the PWV value accurately. Using the example depicted in <FIG>, the difference in longitudinal distance (L vs. L+D) between transducers <NUM> can affect a PWV determination. <FIG> diagrammatically shows a pair of pulse waves closer together than the pair of pulse waves shown in <FIG>, reflecting the difference in distances L and L+D. Hence, using the present disclosure the distance (or any deviation therefrom) can be determined and an error in the PWV measurement can be avoided.

<FIG> diagrammatically illustrates a biomedical sensor <NUM> attached to a subject's neck (e.g., to sense a carotid artery). When a biomedical sensor <NUM> is placed on a subject's neck (e.g., to sense a carotid artery), the deformation of the biomedical sensor <NUM> may be substantially more complex that the longitudinal deformation described above; e.g., the deformation may include longitudinal, torsional, or shear stress, and combinations thereof, diagrammatically shown as yaw, roll, and pitch.

<FIG> provide another example of the significance of the present disclosure, and its ability to measure deformations of the biomedical sensor <NUM> for the purpose of correcting aberrations of ultrasound measurements. <FIG> illustrates an array of ultrasound transducers <NUM> disposed within a biomedical sensor <NUM> shown in a planar, default orientation. The signals from the ultrasound transducers <NUM> are combined following geometrical laws to find focal points corresponding to ultrasound reflectors (e.g., walls within an artery cross-section). <FIG> diagrammatically illustrates the biomedical sensor <NUM> in a configuration deformed from the default configuration. In the deformed configuration, absent the present disclosure, the focal point determined from the ultrasonic transducers <NUM> will likely be aberrant; e.g., because in the deformed configuration, the relative positions and/or orientations of the ultrasonic transducers <NUM> are changed from those of the default configuration. Using the teachings of the present disclosure (e.g., using the displacement sensors <NUM>), the type and magnitude of the deformation(s) can be determined, the position and orientation of the ultrasonic transducers <NUM> can be determined and the accounted for, and a corrected focal point determined; e.g., <FIG>.

Referring to <FIG>, in some embodiments a biomedical sensor <NUM> may be configured to perform signal processing (e.g., signal multiplexing, conditioning, etc.) locally at the biomedical sensor <NUM>. In those instances where the biomedical sensor <NUM> is connected by hardwire to the controller <NUM>, a biomedical sensor <NUM> configured to locally perform signal processing can advantageously limit the number of wires required for communications between the biomedical sensor <NUM> and the controller <NUM>, and/or simplify the displacement sensor <NUM> wiring within the biomedical sensor <NUM>. For example, a single processor chip <NUM> may be in communication with a displacement sensor <NUM> to measure one or more characteristics (e.g., impedance, capacitance, resistance, etc.) of that particular displacement sensor <NUM>. In some embodiments, one or more processor chips <NUM> may be included that are operable to perform multiplexing tasks; e.g., a processor chip <NUM> may be in communication with a plurality of displacement sensors <NUM> simultaneously, and multiplex computation tasks associated with each displacement sensor <NUM>. These embodiments can advantageously limit the number of wires required for communication between the biomedical sensor <NUM> and the controller <NUM>, and/or simplify the displacement sensor <NUM> wiring within the biomedical sensor <NUM>. The power required to operate the processor chips <NUM> may be provided by the controller <NUM>, or a battery, or other source.

In some embodiments, a biomedical sensor <NUM> may include a plurality of displacement sensor cells <NUM>. Each cell <NUM> may be configured as described above with a plurality of displacement sensors <NUM> configured to sense a variety of different deformations of the biomedical sensor <NUM>, and provide signal information indicative thereof to permit the type and magnitude of the deformation to be identified. In some embodiments, each cell <NUM> may include one or more processor chips <NUM>. The displacement sensor cells <NUM> may have a modular configuration; i.e., a pattern that repeats itself, periodic and or symmetric. The present disclosure is not limited to any particular number of displacement sensor cells <NUM> or relative positions of the same. In fact, present disclosure biomedical sensors <NUM> can be configured with particular applications (e.g., neck), wherein the number and position of the displacement sensor cells <NUM> within the biomedical sensor <NUM> is optimum for that particular application. <FIG> diagrammatically illustrates a biomedical sensor <NUM> with a plurality of displacement sensor cells <NUM> disposed in an exemplary arrangement.

During operation of at least some present disclosure systems <NUM>, at least one biomedical sensor <NUM> is attached to the subject. In some instances, the biomedical sensor <NUM> may be positioned in alignment with a blood vessel of the subject. Non-limiting examples of blood vessels that may be sensed include the descending aortic artery, a carotid artery, a femoral artery, and a brachial artery. When initially attached to the subject, the biomedical sensor <NUM> may be disposed in its default configuration (e.g., See <FIG>) or it may be disposed in a deformed configuration (e.g., See <FIG>). In some instances, the configuration of the biomedical sensor <NUM> may change after attachment to the subject (e.g., See <FIG>).

Once the biomedical sensor <NUM> is attached to the subject, the present disclosure permits a determination regarding whether the biomedical sensor <NUM> is in its default configuration. If the biomedical sensor <NUM> is determined to be in a deformed configuration, the present disclosure permits a determination of the type and magnitude of the deformation. This determination may be performed once, periodically, or with a frequency so as to be essentially continuous. The determination of the type and magnitude of the deformation may then be used to directly or indirectly determine the position and/or orientation of the ultrasonic transducers <NUM> and a corresponding correction(s) created so that the information produced by the ultrasonic interrogation is produced more accurately than would be without the correction(s) and one or more physiological parameters (e.g., blood vessel diameter, pulse wave velocity, etc.) are determined more accurately. Hence, the present disclosure discloses an apparatus and method for accounting for three-dimensional (3D) deformations of a biomedical sensor <NUM> that substantially has a two-dimensional (2D) geometry. Present disclosure biomedical sensors are also not limited for use in determining physiological parameters such as blood vessel diameter, pulse wave velocity, and the like. The ability of the present disclosure to account for three-dimensional (3D) deformations of a biomedical sensor <NUM> makes it well suited for use in blood flow measurements. A person of skill in the art will recognize that parameters (e.g., blood flow velocity profile, etc.) utilized in determining blood flow measurements may be affected by blood vessel geometry. The ability of the present disclosure to ascertain sensor deformation and account for that deformation, so that the information produced by the ultrasonic interrogation is produced more accurately, can be used to facilitate blood flow measurements.

While various inventive aspects, concepts and features of the disclosures may be described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects, concepts, and features may be used in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present application. Still further, while various alternative embodiments as to the various aspects, concepts, and features of the disclosures--such as alternative materials, structures, configurations, methods, devices, and components, alternatives as to form, fit, and function, and so on--may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the inventive aspects, concepts, or features into additional embodiments and uses within the scope of the present application even if such embodiments are not expressly disclosed herein. For example, in the exemplary embodiments described above within the Detailed Description portion of the present specification, elements are described as individual units and shown as independent of one another to facilitate the description. In alternative embodiments, such elements may be configured as combined elements.

Additionally, even though some features, concepts, or aspects of the disclosures may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present application, however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated.

Claim 1:
A biomedical sensor (<NUM>), comprising:
a deformable body panel (<NUM>);
at least one first ultrasonic transducer (26A) attached to the deformable body panel;
at least one second ultrasonic transducer (26B) attached to the deformable body panel; and
at least one displacement sensor (<NUM>) in communication with the deformable body panel;
wherein the biomedical sensor is disposable in at least one default configuration wherein the at least one first ultrasonic transducer and the at least one second ultrasonic transducer are disposed relative to one another in a known first spatial transducer configuration;
wherein the biomedical sensor is disposable in one or more deformed configurations wherein the at least one first ultrasonic transducer and the at least one second ultrasonic transducer are disposed relative to one another in a second spatial transducer configuration different than the known first spatial transducer configuration;
wherein the at least one displacement sensor is configured to produce signal information indicative of a difference between the known first spatial transducer configuration and the second spatial transducer configuration; and
wherein the at least one displacement sensor comprises a plurality of strain sensors comprising a first strain sensor (28A) extending in a lengthwise direction between a first point (A) and a second point (B), a second strain sensor (28B) extending in a lengthwise direction between a third point (C) and a fourth point (D), a third strain sensor (28C) extending in a widthwise direction between the first point (A) and the fourth point (D), a fourth strain sensor (28D) extending in a widthwise direction between the second point (B) and the third point (C), a fifth strain sensor (28E) extending between the first point (A) and the third point (C), diagonal to the lengthwise and widthwise directions, and a sixth strain sensor (28F) extending between the second point (B) and the fourth point (D), diagonal to the lengthwise and widthwise directions.