METERS FOR IN-VIVO MONITORING

Abstract

Systems and methods for use in monitoring treatment of pressure-related conditions, such as hydrocephalus, include an implantable vessel, and a meter including one or more microfluidic channels connected to the vessel. The microfluidic channels may be configured to detect at least one of pressure and fluid flow rate through the vessel and to be read out remotely by a wirelessly coupled external device. The meter may include a passive resonant (LC) circuit. A dynamic flap may be included in the microfluidic channel that may act as part of the LC circuit. An external device may also be configured to inductively couple remotely to the LC circuit, with-out physical connections to the implantable vessel or pressure meter, and to display a pressure acting on the pressure meter and/or a fluid flow through the meter.

Claims

1-10. (canceled)

11. An apparatus for use in monitoring fluid pressure within a body, comprising: an implantable vessel; and a pressure meter including one or more microfluidic channels connected to the vessel and configured to detect a pressure at the vessel and to be read out remotely by a wirelessly coupled external device.

12. The apparatus of claim 11, wherein the vessel and the pressure meter are included in an implantable unit, the apparatus further comprising: a control circuit included in the implantable unit and configured to process data from the pressure meter; and a memory device included in the implantable unit and configured to store and retrieve the processed data from the control circuit.

13. The apparatus of claim 13, further comprising: a rechargeable power source included in the implantable unit and configured to recharge electrical battery power via inductive coupling with a wirelessly coupled external device.

14. The apparatus of claim 11, wherein the pressure meter includes a passive resonant tank (LC) circuit.

15. The apparatus of claim 14, wherein the microfluidic channel includes at least one volumetric reservoir.

16. The apparatus of claim 15, wherein the pressure meter further includes a dynamic layer in communication with the at least one reservoir and a static layer opposite the dynamic layer, the static layer including an inductor coil configured to react to displacement of the dynamic layer.

17. The apparatus of claim 15, comprising a plurality of reservoirs, each of the plurality of reservoirs having different dimensions and configured as separate LC circuits.

18. The apparatus of claim 14, wherein the microfluidic channel includes at least one dynamic flap at least partially obstructing the microfluidic channel, the pressure meter configured such that a displacement of the flap changes or modulates a capacitance of a capacitor of the LC circuit.

19. The apparatus of claim 14, further comprising an external device configured to inductively couple remotely to the LC circuit, without physical connections to the implantable vessel or pressure meter, and to display a pressure acting on the pressure meter.

20-24. (canceled)

25. A method of manufacturing a meter, the method comprising: patterning a microfluidic channel into a substrate; and providing an LC circuit proximate to the microfluidic channel that is configured to detect at least one of a pressure within and a fluid flow through the microfluidic channel.

26. The method of claim 25, further comprising: providing at least one volumetric reservoir in communication with the microfluidic channel; at least partially covering the at least one reservoir with a dynamic layer; and providing a static layer opposite the dynamic layer, the static layer including an inductor coil configured to react to displacement of the dynamic layer.

27. The method of claim 26, wherein the inductor coil is micro-patterned onto the static layer.

28. The method of claim 25, further comprising: forming a plurality of volumetric reservoirs, each of the plurality of reservoirs having different dimensions and configured as separately readable LC circuits.

29. The method of claim 25, further comprising: providing at least one dynamic flap at least partially obstructing the microfluidic channel, wherein, the meter is configured such that a displacement of the flap changes a capacitance of a capacitor of the LC circuit.

30. The method of claim 29, the at least one flap comprising a low-dielectric material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings, which are included to provide a further understanding of the invention, are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the detailed description serve to explain the principles of the invention. No attempt is made to show structural details of the invention in more detail than may be necessary for a fundamental understanding of the invention and various ways in which it may be practiced. In the drawings:

[0040] FIG. 1 is a block schematic illustration of a first embodiment of an exemplary implantable device according to aspects of the invention.

[0041] FIG. 2 is a cutaway top view of an exemplary implantable meter including a plurality of reservoirs according to aspects of the invention.

[0042] FIG. 3 is a cutaway side view showing additional details of an exemplary implantable meter according to aspects of the invention,

[0043] FIG. 4 is an illustration showing additional details of an exemplary LC circuit according to aspects of the invention.

[0044] FIG. 5 is a cutaway side view of an exemplary implanted meter and an external reading device according to aspects of the invention.

[0045] FIG. 6 is a block schematic illustration of an exemplary external reading device according to aspects of the invention.

[0046] FIG. 7 is a cutaway side view showing details of an exemplary implantable pressure meter according to further aspects of the invention.

[0047] FIGS. 8A-8B are schematic illustrations of an exemplary meter including a dynamic flap according to yet further aspects of the invention.

[0048] FIG. 9 is a top view of showing additional details of an exemplary interdigitated capacitor which may be used with the dynamic flap shown in FIGS. 8A-8B.

DETAILED DESCRIPTION OF THE INVENTION

[0049] It is understood that the invention is not limited to the particular methodology, protocols, and reagents, etc., described herein, as these may vary as the skilled artisan will recognize. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only, and is not intended to limit the scope of the invention. It also is be noted that as used herein and in the appended claims, the singular forms a, an, and the include the plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to a reservoir is a reference to one or more reservoirs and equivalents thereof known to those skilled in the art.

[0050] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the invention pertains. The embodiments of the invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and examples that are described and/or illustrated in the accompanying drawings and detailed in the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale, and features of one embodiment may be employed with other embodiments as the skilled artisan would recognize, even if not explicitly stated herein. Descriptions of well-known components and processing techniques may be omitted so as to not unnecessarily obscure the embodiments of the invention. The examples used herein are intended merely to facilitate an understanding of ways in which the invention may be practiced and to further enable those of skill in the art to practice the embodiments of the invention. Accordingly, the examples and embodiments herein should not be construed as limiting the scope of the invention, which is defined solely by the appended claims and applicable law. Moreover, it is noted that like reference numerals reference similar parts throughout the several views of the drawings.

[0051] Moreover, provided immediately below is a Definition section, where certain terms relating to the invention are defined specifically. Particular methods, devices, and materials are described, although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the invention. All references referred to herein are incorporated by reference herein in their entirety.

[0052] The terms treating and treatment as used herein refer to reduction in severity and/or frequency of symptoms, elimination of symptoms and/or underlying cause, prevention of the occurrence of symptoms and/or their underlying cause, and improvement or remediation of damage.

[0053] The term patient as in treatment of a patient refers to a mammalian individual afflicted with or prone to a condition, disease or disorder as specified herein, and includes both humans and animals.

[0054] The term dynamic as used herein refers to walls, covers, layers, flaps, and other structural components of devices described herein that are intended to be moveable with respect to other device components, pliable and/or deformable under normal operating conditions.

[0055] The term vessel as used herein refers to various structural components of devices described herein in which a fluid can flow or be contained, such as catheters, shunts, reservoirs, etc.

[0056] The term fully implantable as used herein refers to devices that are configured to be implanted in a patient's body without components, attachments or physical leads, such as wires, tubes or other connections, extending outside of the body.

[0057] The following preferred embodiments may be described in the context of exemplary CSF shunt procedures for ease of description and understanding. However, the invention is not limited to the specifically described devices and methods, and may be adapted to various clinical applications without departing from the overall scope of the invention. For example, devices and related methods including concepts described herein may be used for various treatment and monitoring methods involving pressure and/or flow-related conditions.

[0058] As shown in FIG. 1, a first embodiment of the invention may include an implantable device 100 with one or more of a meter 120, a processor 130, a memory 140, a power source 150, and/or communication device 160. Implantable device 100 may include one or more connections, ports, etc., for joining the device to, and providing fluid communication with, vessels such as shunts, catheters, or other reservoirs that are fully or partially implanted in a patient's body. The connections may include one or more input and/or output ports. The meter 120 may take various forms, such as those described further herein, and may include, for example, one or more remotely or otherwise controllable valves, one or more microchannels and a pressure and/or flow sensor that is remotely readable by wirelessly coupling the device 100 with an external device.

[0059] The processor 130 may be configured to process various data detected by the meter 120 and/or to store raw and/or processed data in memory 140, or communicate raw, processed and/or stored data to an external device via communication device 160. Memory 140 may include various electronic storage means, and may be configured to store various programming instructions to be used by the processor 103, for example, to interpret detected data, calibrate the device 100, force an inductance to push on a capacitor sensor, configure the device to report intermittent readings, respond to remote interrogation, etc. Power source 150 may include various electrical power sources, such as rechargeable batteries and associated circuitry configured to be remotely chargeable by, for example, wirelessly coupling the device 100 with an external charger.

[0060] In embodiments, an implantable device, such as device 100, may be remotely controllable and/or programmable via an external device. For example, communication device 160 may be configured to receive commands, e.g. to adjust flow metering, to stop or start a fluid flow, etc., and/or programming updates from an external device and to apply them to instructions in memory 140. The device 100 may also be configured to perform predetermined actions at scheduled intervals, in response to detected pressure and/or flow conditions, etc. For example, valves in meter 120 may be controlled on a predetermined schedule to regulate flow through the meter, throttle, open and/or shut the meter according to detected pressure, etc.

[0061] FIG. 2 provides additional details of an exemplary meter according to aspects of the invention including a plurality of reservoirs. As shown in FIG. 2, meter 200 may include ports 210 for connection with a vessel. Ports 210 may include remotely or otherwise controllable valves, and may be in communication with a microchannel 212 with an interior diameter of, for example, approximately 1 mm. Microchannel 212 may be fabricated, for example, on a substrate using micromachining techniques.

[0062] A plurality of reservoirs 220, 222 and 224 may be in communication with the microchannel 212. It should also be noted that, embodiments of the invention may also include only one reservoir, or other numbers of reservoirs than shown in FIG. 2. In the embodiment shown in FIG. 2, the reservoirs 220, 222 and 224 include different interior dimensions, and volumes, which may be used in processing techniques that determine a pressure, and fluid flow, through the meter. In embodiments, the interior diameters of the reservoirs may vary, for example, between approximately 1 mm to approximately 5 mm. For example, reservoir 220 may have an interior diameter 214 of between approximately 1 mm to 2 mm, reservoir 224 may have an interior diameter 216 of approximately 5 mm, and reservoir 222 may have an interior diameter between approximately 2 mm to 4 mm.

[0063] Meter 200 may have, for example, a length 232 of approximately 10 mm to 15 mm and a width 234 of approximately 3 mm to 4 mm. Additional details of a cutaway side view of exemplary meter 200 are shown in FIG. 3.

[0064] As shown in FIG. 3, the meter 200 may have a height 236 of approximately 2 mm to 4 mm and may include a dynamic layer 310 that is locally deformable subject to fluid pressure within the microchannel 212. A plurality of LC circuits 320. 322 and 324 may be disposed with respect to each of the reservoirs 220, 222, and 224 shown in FIG. 2. Dynamic capacitor plates 330, 332, and 334, corresponding to each of the LC circuits, may be disposed on the dynamic layer 310. Static capacitor plates 340, 342, 344 may be disposed, e.g. by depositing metal into recessions in a patterned top substrate 312, above each of dynamic capacitor plates 330, 332, and 334, respectively. Inductor coils 350, 352 and 354 may be disposed above each set of dynamic and static capacitor plates, with electrical connections to the respective capacitor plates fabricated through the substrate 312. Thus, each group of dynamic capacitor plate, static capacitor plate and inductor coil may form an LC circuit responsive to pressure in corresponding reservoirs and/or regions of the microchannel 212. A isometric view of an exemplary LC circuit is shown in FIG. 4.

[0065] As shown in FIG. 4, exemplary LC circuit 320 may include dynamic capacitor plate 330, static capacitor plate 340 and inductor coil 350, interconnects 410.

[0066] As mentioned above, the meter 200 may be fabricated using micro-machining techniques to achieve small feature sizes. A microfluidic channel, such as microchannel 212, may be patterned into a substrate (e.g. PMMA or glass) via photolithography, etching etc., and capped with a deformable elastomer layer, such as dynamic layer 310. A metal may then patterned on the elastomer over the channel, and/or reservoirs of the channel. This creates a bottom (dynamic) capacitor plate whose vertical position is a function of internal fluid pressure. The top (static) capacitor plate may be created by depositing metal into recessions in a patterned top substrate. Finally, the inductor may be micro patterned onto the very top of the top substrate. Connections between the inductor and capacitor plates may be made by drilling small vias through the top substrate and electroplating interconnects.

[0067] Thus, according to aspects of the invention, a fluid may be introduced to, and/or flow through, a microfluidic channel, such as which has several reservoirs that are capped by a deformable film The deformable film may include one-half of a capacitor, such that the capacitance changes with pressure in the reservoir. By measuring pressure at sequential locations along the microchannel, flow rates can be extracted using conventional flow mechanics, e.g. by considering pressure differentials and resistance between the reservoirs. The dynamic range of the flow meter can be extended by using multiple reservoirs (i.e. capacitors), each with dimensions tailored to specific pressure ranges and flow rates.

[0068] According to further aspects of the invention, exemplary systems and methods may be used to quantify relatively small flow rates and low back pressures, using an implanted (in-vivo) device that provides flow information without outside physical tethers. Embodiments of the invention may detect pressures in a range of, for example, cm H.sub.2O to 20 cm H.sub.2O (roughly 2 to 14 mm Hg), at a flow rate resolution of approximately 1 l/s.

[0069] In embodiments, each reservoir may be configured as an independently functioning and readable LC circuit. Multiple reservoirs may also facilitate remote read-out of the device. That is, for example, a proper positioning of the remote detector over the flow meter may be determined by maximizing the signals from a plurality of LC circuits.

[0070] Deformation of dynamic layers, flaps and the like, in exemplary implanted meters may affect the capacitance of an integrated radio frequency resonator, shifting its resonance frequency. The pressure values can then be interrogated non-invasively by an external measurement device that couples to the resonators inductively across the skin. Flow may be quantified from a pressure drop across the meter or across a shunt valve or other vessel. The measurement device may be used, for example, by a clinician or nurse during check-up visits, or by the patient such as in an extended home-use environment. The use of an implanted meter and an external remote reading device is shown in FIG. 5.

[0071] As shown in FIG. 5, a meter, such as meter 200 show in FIGS. 2 and 3, may he connected with a shunt 510, and fully implanted under the skin 520 of a patient. The combination of the meter 200 and shunt 510 may be configured as a fully implantable unit, for use in-vivo without physical connection to an external device. The meter 200 may be, for example, tunneled surgically under the scalp of a patient, together with a CSF drainage shunt. As described further herein, the meter 200 may have embedded inductor coils, which connected to a capacitor whose properties depend on internal pressure and/or flow conditions.

[0072] An external remote reader 530 may be placed in proximity to the meter 200 and inductively couple to the meter through the skin 520 of the patient. For example, individual resonator circuits 540, 542 and 544 may detect changes in inductance of LC circuits of the meter 200. The reader may be configured, for example, to measure shifts in the resonance of the meter's LC circuits, which can then be related to internal pressures and flow rate. Reader 530 may include control circuits and processing logic configured to process the data read into pressure and/or flow information that may be, for example, stored, transmitted via wired or wireless connection and/or displayed for a user on display 550. In embodiments, a reader such as reader 550 may be attached to or included in a garment or other support that allow for the reader to be worn for a prolonged period by a patient, e.g. to allow sustained or periodic remote reading of the pressure and/or flow through meter 200. Further details regarding an exemplary remote reader are shown in FIG. 6.

[0073] As shown in FIG. 6 a further embodiment of the invention may include remote reading device 600 with one or more of a coupling device 610, a processor 620, a memory 630, a power source 640, a communication device 650, and/or a display 660. Reading device 600 may be configured to detect changes in capacitance of one or more LC circuits included in an implanted meter as described herein, and may further be configured to communicate with an implanted unit, e.g. by radio transmission and reception, etc. The processor 620 may be configured to process various data detected or received from an implanted meter and/or to store raw and/or processed data in memory 630, or communicate raw, processed and/or stored data to another remote system, e.g. a LAN, smartphone or other handheld device, via communication device 650. Communication device 650 may operate in various modes known in the art, e.g. Bluetooth, IR, etc. Memory 630 may include various electronic storage means known in the art. Power source 640 may include various electrical power sources, and may include associated circuitry configured to remotely charge a power source included in an implanted device, e.g. by inductive charging.

[0074] In embodiments, an external device, such as remote reading device 600, or other microprocessor-drive device with a communication capability, may be configured to remotely control and/or program an implanted device such as device 100 shown in FIG. 1. For example, communication device 650 may be configured to transmit commands, e.g. to adjust flow metering, to stop or start a fluid flow, etc., and/or programming updates to an implanted device.

[0075] According to further aspects of the invention, a meter, similar to meter 200, may be configured to act as a pressure meter, without a flow through the meter. For example, as shown in FIG. 7, a pressure meter 700 may have a microchannel with inlet 710 that is in communication with a vessel. One or more LC circuits such as described above with reference to FIGS. 2 and 3, may be included to detect a pressure within the microchannel. It should be appreciated that a flow meter, such as meter 200, may be configured for use as a pressure meter by blocking an outlet port of the meter, e.g. by closing a valve in the outlet port, and can be transitioned hack to use as a flow meter by opening the outlet port. Thus, according to aspects of the invention a single meter may be used, for example, to monitor a non-flow internal pressure, allow flow in response to sensed or other predetermined conditions, monitor a flow rate through the meter, and stop or adjust a flow through the meter.

[0076] FIGS. 8A and 8B show an alternative approach, which may be used, for example, to measure extremely small flow rates. As shown in FIG. 8A, a flap 810 of a low-dielectric, highly compliant material (e.g., PDMS) may be fabricated into a mircofluidic channel 820 in such a way that it forms part of the dielectric of a capacitor at rest. Interdigitated finger capacitor 830 may be disposed on an opposite side of the mircofluidic channel 820. As shown in FIG. 8B, flow of the liquid in the channel (shown by the arrow) may push the flap 810 outside of the capacitor's electric field, replacing it with aqueous medium in the channel. Due to the much higher dielectric constant of water (about 80), this leads to a pronounced drop in capacitance. This drop may be measured using a similar approach to that described above, by integrating the capacitor into a resonant LC circuit, whose resonance frequency can be measured remotely by cross-inductance. A top view of an exemplary interdigitated finger capacitor 830 is shown in FIG. 9, with electrodes 831 and 832 disposed on the bottom of channel 820.

[0077] In embodiments, the ultimate performance of exemplary devices may be dictated by the shift in resonance of an LC circuit. Small changes in pressure must lead to detectable changes in frequency. For typical capacitor dimensions in the millimeter-size range, the baseline capacitance at zero pressure may be approximately 10 pF. It has been found that even slight line pressures may push the deformable film upwards, increasing the capacitance quickly. When the pressure is sufficient to close the gap, the capacitance is dictated by the minimum gap size, taken here to be 100 nm (corresponding to a 100 nm thick dielectric layer coating the upper electrode. Assuming an inductor of approximately 50 nH, the resonant frequencies at zero pressure are in the range of 50-200 MHz. This drops as the internal pressure increases, as the capacitance increases due to decreasing the gap size.

[0078] According to aspects of the invention, the inventors have produced LC resonators with frequencies in the range of 10-800 MHz range and quality factors (Q) of approximately 50. A reasonable threshold for detection is a frequency shift that is 10% of the resonance bandwidth, corresponding to relative frequency changes of approximately 0.5% of the resonant frequency at Q=20. As such, resolving pressure changes in the 10-300 Pa range may be achieved. In embodiments, to determine flow rate, the pressure change between two sensors at different points along the flow channel may be measured, and the pressure change can be related to flow rate using viscous-toss models for flow in the channel using conventional techniques. The use of different upstream and downstream sensors also presents opportunities for redundant (cross-check) measurements.

[0079] As described herein, an aspect of an embodiment of the present invention comprises, but not limited thereto, the integration of microfabricated features into CSF shunt catheter implants both upstream and downstream to the shunt valve that deform in response to CSF pressure.

[0080] The description given above is merely illustrative and is not meant to be an exhaustive list of all possible embodiments, applications or modifications of the invention. Thus, various modifications and variations of the described methods and systems of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments.