Patent Application
20250032027
This application relates to ultrasound beam guidance and deals with ultrasound beam guidance for transcranial focused ultrasound (tFUS) using electroencephalogram (EEG) measurements, more specifically shielding techniques for an apparatus with physiological measurement systems and ultrasound beam guidance.
Transcranial focused ultrasound (tFUS) is a non-invasive neurostimulation technology utilizing low-intensity ultrasound. Compared to other techniques like magnetic or electric non-invasive brain stimulation, tFUS has better spatial resolution and safety and can reach deeper areas of the brain.
One embodiment of the present disclosure sets forth a system comprising: one or more ultrasound transducers; one or more electroencephalogram (EEG) electrodes; and a holder unit that holds a particular EEG electrode of the one of the one or more EEG electrodes in a predetermined position relative to an ultrasound pressure field of a particular ultrasound transducer of the one of the one or more ultrasound transducers to reduce noise in EEG data.
At least one technical advantage of the disclosed techniques relative to the prior art is that, with the disclosed techniques, a tFUS and EEG system can include an individual holder unit that includes ultrasound and EEG operation concurrently, unlike existing devices. With the disclosed tFUS and EEG techniques, an EEG electrode can be located, for example, to avoid a direct ultrasound pressure field generated by the ultrasound transducers. This can shield the EEG electrode from vibrations and thereby reduce EEG noise relative to other systems. The disclosed systems can also shield the EEG electrode from vibrations and electrically induced noise using additional developments disclosed herein. These technical advantages provide one or more technological advancements over prior art approaches.
One embodiment of the present disclosure sets forth a method comprising: providing a holder unit; and holding, using the holder unit, a particular EEG electrode of one of the one or more EEG electrodes in a predetermined position relative to an ultrasound pressure field of a particular ultrasound transducer of one of the one or more ultrasound transducers to reduce noise in EEG data.
At least one technical advantage of the disclosed techniques relative to the prior art is that, with the disclosed techniques, a tFUS and EEG system can include an individual holder unit that includes ultrasound and EEG operation concurrently, unlike existing devices. With the disclosed tFUS and EEG techniques, an EEG electrode can be located, for example, to avoid a direct ultrasound pressure field generated by the ultrasound transducers. This can shield the EEG electrode from vibrations and thereby reduce EEG noise relative to other systems. The disclosed systems can also shield the EEG electrode from vibrations and electrically induced noise using additional developments disclosed herein. These technical advantages provide one or more technological advancements over prior art approaches.
One embodiment of the present disclosure sets forth an apparatus comprising: one or more ultrasound transducers; one or more electroencephalogram (EEG) electrodes; and a holder unit that holds a particular EEG electrode of the one of the one or more EEG electrodes in a predetermined position relative to an ultrasound pressure field of a particular ultrasound transducer of the one of the one or more ultrasound transducers to reduce noise in EEG data.
At least one technical advantage of the disclosed techniques relative to the prior art is that, with the disclosed techniques, a tFUS and EEG system can include an individual holder unit that includes ultrasound and EEG operation concurrently, unlike existing devices. With the disclosed tFUS and EEG techniques, an EEG electrode can be located, for example, to avoid a direct ultrasound pressure field generated by the ultrasound transducers. This can shield the EEG electrode from vibrations and thereby reduce EEG noise relative to other systems. The disclosed systems can also shield the EEG electrode from vibrations and electrically induced noise using additional developments disclosed herein. These technical advantages provide one or more technological advancements over prior art approaches.
So that the manner in which the above recited features of the various embodiments can be understood in detail, a more particular description of the inventive concepts, briefly summarized above, can be had by reference to various embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the inventive concepts and are therefore not to be considered limiting of scope in any way, and that there are other equally effective embodiments.
In the following description, numerous specific details are set forth to provide a more thorough understanding of the various embodiments. However, it will be apparent to one of skilled in the art that the inventive concepts can be practiced without one or more of these specific details.
A transcranial focused ultrasound (tFUS) system and EEG (Electroencephalogram) is capable of integrating ultrasound (US) and EEG systems along with neuro-navigational aids to improve ultrasound beam guidance. Construction techniques with mechanical and electrical shielding materials can minimize mutual interference between ultrasound and EEG operation. To improve coupling, mess-free and user-friendly head interfacing patches, gels, and solutions are used. The head can refer to any surface of a head including without limitation the forehead, the scalp, the temples, and so on. The surface of the head or “head” can include or exclude hair, oils, and other items. A post-based tFUS system can be constructed from an array of one or more ultrasound and EEG posts to improve contact with the head. It is noted that when an ultrasound transducer is referred to, it can also be understood to be a transducer array.
The tFUS and EEG system can make solid contact with the head for both US and EEG. In addition, to stimulate specific targeted brain regions, the relative location, and orientation of the tFUS system to these brain regions can be known. For this, a holder that includes tFUS and EEG components can be placed correctly on the head. To acquire high-quality EEG data, the EEG electrodes can similarly be placed in the correct locations and achieve good coupling. The complete system can include multiple independently adjustable tFUS and/or EEG units. To aid with neuro-navigation (correct placement), the tFUS and EEG systems described here use visual, audio, and haptic aids, as well as systems that work in concert to orient and register the tFUS and EEG system with the subject's head. To this end, two parts of the tFUS and EEG system include 1) navigational aids that help register the location of the tFUS and EEG systems relative to the subject's brain and 2) visual aids that help indicate to the subject or another person how to adjust the location of the systems according to the navigational info.
Neuro-navigational aids can include markers and indicators of various types. For example, neuro-navigational aids can include reflective beads or strips, as well as Light Emitting Diodes (LEDs) and other special markers that the overall system can detect using Light Detection and Ranging (LIDAR) and cameras. The neuro-navigational aids can be used with cameras or similar imaging systems to register the spatial location and orientation of the tFUS and EEG system on the subject's head. The special location and orientation can be associated with coupling of ultrasound and/or EEG. As a result, the imaging systems can be used to guide placement of the holder unit to increase ultrasound coupling and EEG coupling. A client device (such as a mobile device or a computer device), or the holder device can receive neuro-navigational detection data from a LIDAR device or a camera device. The neuro-navigational detection data can indicate a detection of the neuro-navigational aids relative to a head of a subject. The device can include an application that identifies a spatial location and orientation of the tFUS and EEG system relative to the head of the subject based on the neuro-navigational detection data. The device can also use the neuro-navigational detection data to identify characteristics of the head of the subject such as size and shape of the head. This head shape can include one or more three dimensional shapes corresponding to the subject's overall head shape. In one implementation, a smartphone-based app with an embedded camera is used to guide the placement of the tFUS and EEG system. As a visual aid, the tFUS and EEG system can activate multi-colored LEDs as feedback to indicate the correct and incorrect placement of both ultrasound and EEG components. A display device (e.g., a screen on the holder device or a client device) and/or LEDs on the holder device or another device can provide visual neuro-navigational indicators that indicate holder positioning information including which direction and orientation to move the tFUS and EEG holder. LEDs can be shaped like arrows and show how to move the system(s). In one implementation, two different sets of LEDs (spatially separated) are used to indicate the correct placement of the ultrasound and EEG, such as a left-right or up-down pair. A different set of LEDs (or other visual indicators such as user interface elements on a display device) can also indicate the coupling quality of the ultrasound and EEG. Similarly, LEDs can indicate the system's electrical or ultrasonic recording noise levels. A LIDAR system (can be internal or external to the tFUS and EEG systems) can be used to guide the placement. An internal LIDAR system with an external mirror, a camera, or a smartphone can guide the subject to place the tFUS and EEG systems. In another implementation, the tFUS and EEG system includes magnetic sensors or magnets that can be turned on and off to help alignment or spatial-registration.
Audio clues or cues can also be used as audio-based neuro-navigational indicators and aids to guide the placement. The tFUS and EEG system can include multiple speakers, which can be used for guidance. For instance, to move the tFUS and EEG system to the right, a tone can be sounded on the right speaker (with the other speakers turned off). The pitch, duration, and type of the tone can be encoded to guide correct placement or to indicate incorrect operation. Similarly, vibrations can be used for guidance. Special care is needed to ensure that neuro-navigation aids don't interfere with the system's operation.
The previous sections describe ways to register the tFUS and EEG system relative to the head and to guide the user to adjust targeting. However, there are the additional considerations of “What is the shape of the head?”, “Where in the head are the targeted brain regions?” and “How can we refine the aiming of the tFUS to the targeted brain region, especially using simultaneous EEG?” Head and brain region information can be obtained from CT (Computed tomography), fMRI (functional magnetic resonance imaging) studies, individualized MRI (magnetic resonance imaging) & fMRI subject data, individualized head-shape measurements (using calipers or similar mechanical stereotactic equipment), and individualized measurements using optical technologies such as LIDAR.
Once the tFUS and EEG system is placed on the head, it can be further adjusted for targeting using one or both ultrasound imaging and biomarkers in the EEG. In an embodiment, individualized US-based imaging from the transducers on the head includes echo time, echo strength (as well as scattering and absorption loss estimates), blood flow speed and volume measurement, tissue strain, and pulsatility, and these data and images can be used. Ultrasound-based imaging has the added advantage that head-aberration correction leads to cleaner or clearer data and images. This aberration correction can involve adjusting the timing corrections of elements of a transducer array (phase correction) and it can be done iteratively or by feeding raw data through a neural net or similar algorithm. This same head-aberration correction information can then be applied to tFUS when targeting specific brain areas. In another embodiment, one can detect a biomarker signal in the EEG from an area of interest, a nearby area, or a known area used for triangulation. The tFUS portion of the device can then be used and parameters for aiming (phasing with arrays or slight mechanical adjustments with standard transducers) fine-tuned until there is expected modulation of said biomarker. Alternatively, a tFUS waveform and target known to elicit specific EEG biomarkers, such as an evoked potential can be used to fine-tune aiming. Finally, elicited percepts, conscious or subconscious, can also be used similarly to fine-tune aiming.
The operation of the tFUS and EEG system can be described using the primary visual cortex (V1) as an example and assuming that the system has been placed in the approximately correct location using neuro-navigation and head shape information. When using ultrasound imaging of blood flow, pulsatility, and similar markers of brain activity, the system can present repeated visual stimuli at known times and in known locations of a subject's visual field and hence expect brain activity changes in specific subregions of V1 at specific times. The tFUS and EEG system can use an approximate phase correction with the transducer array to image the subregion of V1 that is expected to be activated. The tFUS and EEG system can detect a measurable, but still suboptimal, signal in response to these visual stimuli. This process can be used to generate neuro navigation indications to improve ultrasound efficacy. For example, the process can involve applying a predetermined ultrasound signal to a predetermined area, using the EEG to detect EEG biomarkers in association with a predetermined stimulus, performing a comparison of the detected EEG biomarkers to predetermined expected EEG biomarkers for the predetermined stimulus, and activating neuro-navigational indicators to indicate a direction to move the system to improve efficacy.
The tFUS and EEG system can adjust the raw data in each channel of the array such that the signals seen give a clearer image. Such algorithms for image enhancement can be simple, similar to auto-focusing by maximizing local contrast gradients in motorized lens and camera systems, or more complex, similar to having a micro-lens-fitted sensor correcting for aberrations in images using a neural net. Alternatively, or in addition, the tFUS and EEG system can use EEG biomarkers to optimize targeting feedback provided using LEDs. As before, the tFUS and EEG system can present the subject with known visual stimuli but record evoked potentials, in this case, visual evoked potentials (VEP), via EEG. Again, the tFUS and EEG system can start with an approximate starting phase correction to target this part of V1.
The tFUS and EEG system can detect a slight enhancement or suppression of the VEP depending on the tFUS targeting, waveform, and intensity. The tFUS and EEG system can also refine targeting by adjusting the ultrasound phasing parameters to see modulatory effects increase or decrease in strength, thereby determining whether phase correction is improving or worsening as it is adjusted. Alternatively, the tFUS and EEG system can omit a visual stimulus for the subject. The tFUS and EEG system can instead apply a tFUS waveform that is known to elicit a VEP reliably but is close to the threshold for intensity, focal size, or pressure gradient to do so. With the starting phase correction, the tFUS and EEG system can decline to elicit VEPs or do so only occasionally. The tFUS and EEG system can adjust the phase correction based on the improvement or worsening of the VEP reliability. Finally, beyond using an EEG biomarker like VEP, the tFUS and EEG system can use a sensory percept to adjust targeting and aiming of tFUS, in this case, a perception of a visual stimulus when none was given. With sufficiently good phase correction and aiming with tFUS, the subject can report a visual percept. However, said percept need not be consciously reportable. One can use sensitive psychophysical tasks such as asking a subject to guess in which of two time periods or locations a visual stimulus was in. Such two-alternative forced choice tasks can reliably detect biases even without a conscious percept. Improved reliability of these percepts can be utilized to adjust phase correction and targeting with tFUS.
The tFUS and EEG systems described here include holders that includes a housing or frame structure that holds ultrasound transducers and EEG electrodes in a particular arrangement. The holders can include mechanical structures and necessary circuitry that allows mounting to headbands, headsets, stereotactic arms, or other similar devices. Holders include neuro-navigation components, including time-synched or strobing LEDs, LIDAR contrast-enhancing markers, uniquely colored or patterned markers, and beads reflective of (including but not limited to) infrared light. Such markers need not be on the top of the holder, and it can be beneficial to have them on the sides of the holder.
The key to obtaining spatial information from EEG is to have many locations of electrical recording from the head across the head. Each EEG electrode can record from a somewhat spatially-limited region of the head. An EEG electrode with low electrical-resistance contact to a large swath of the head can record a spatially-blurred and averaged signal and thus not contain much spatial information. A traditional EEG electrode is often made from materials such as silver chloride that have a poor acoustic match with soft tissue and gels. They are also often 3 mm or greater in one or more dimensions. This combination of traits makes them such that if they are in an ultrasound field, they can absorb and reflect some of that mechanical energy. The result is that the EEG electrode can “rattle” and mechanical artifact signals can appear in the EEG data. In addition, EEG electrodes can also aberrate the ultrasound field and distort the focal point or make the focal point unknown, thus leading to the modulation of unintended brain regions while missing the intended target. Due to the size of some components and the anatomy of the human brain and head, it will also not always be possible to place an EEG electrode outside the ultrasound field.
Thus, one aspect of the device is to provide new implementations of electrodes and wires relative to their traditional form. This can solve the problem of bringing multiple single (single as in independent electrically) channels of spatially-limited, local recordings of the head electrical potential signals away from the ultrasound field without affecting the ultrasound field or being affected by the ultrasound field, to the electronics used for EEG signal acquisition such as amplifiers and analog-to-digital converters. More specifically, “electrodes” can be thought of as a cohesive ensemble or assembly of components such that 1) they are in the proximity of the head area that they are recording from, 2) this electrical coupling can be aided by additional conductive gels or patches that contact the head well 3) this area of good electrical contact is spatially-limited and locations known, 4) and this single area can be seen as a single channel of signal which is then conducted by a “wire” to appropriate electronics. Said “wire” can also include several components as needed, and 1) carry the single channel of EEG information from the “electrode” to distal locations via electrical continuity, 2) insulated from surrounding areas such that other electrical signals do not leak in, and 3) bring the signals to standard wires, amplifiers, analog-to-digital converters, or other such components. As described below, these “electrodes” and “wires” can include multiple layers, sections, or materials to achieve the desired properties.
EEG voltages can be of a very small magnitude (e.g., 10 to 100 μV) and are very susceptible to other forms of noise. Besides the interaction with mechanical forces leading to artifacts and noise in the EEG, electrical noise can arise from EMI or the ultrasound transducer's operation. Electrical shielding requirements for artifact-free EEG are often more stringent than those for safety. EEG operation can be insulated from the ultrasound transducer array; the insulation can often protect from both EMI (air-transmitted, without any direct conductive pathway) and direct conductive connection. Each EEG electrode operates independently, in one example embodiment, to capture the EEG signals, so the operation of each EEG electrode is insulated from each other. An EEG control system (not shown in the figures) combines EEG signals captured by individual EEG electrodes. EMI and capacitive shielding can be used to protect EEG operation. Wire mesh cages or similar conductive structures shield EEG channels, pathways, and patches to act as Faraday cages or shields. A Faraday cage's conducting material cancels any external electrical field's effect on EEG channels, paths, etc. These cages can be electrically isolated from the EEG electrode. In an embodiment, a reference EEG patch generates a reference differential signal. The reference differential signal can be used as a ground reference for the rest of the cages. An appropriate ground is used in a different embodiment, such as a battery or a capacitor. Care is taken to ensure that this grounding layer does not contact the head. In an alternate embodiment, proper shielding and isolation can be implemented on the ultrasound transducer or transducer array. Such an approach can be more efficient if multiple EEG electrodes are near a single transducer or transducer array. Particular care can be taken so that these shielding and isolation methods do not interfere with the ultrasound field or the EEG's operation.
The size and shape of ultrasound transducers or transducer arrays 620 and EEG electrodes 630 can be different. In one embodiment, the location, size, shape, and number of ultrasound transducer or transducer arrays 620 and EEG electrodes 630 depend on the local geometry of the head. Head geometry is obtained from existing CT and MRI studies. In an embodiment, individualized MRI data is obtained from the subject. Individualized head-shape measurements are obtained in a different embodiment using calipers or similar mechanically-based stereotactic equipment. Head-shape measurements are obtained using LIDAR and related optical technologies in another embodiment. In an embodiment, holder unit 310 includes an outer shell that can be mounted to headbands, headsets, stereotactic arms, etc. Holder unit 310 includes aids for neuro-navigation. In one implementation, multiple units within a system or multiple holders or systems can use each other (via strain gauges between units; electrical or US transmission between pairs) for additional orientation information. For example, a US transducer can be able to image EEG electrodes on the opposite side of the head via echo characteristics, mainly if an EEG electrode is surrounded by acoustically transparent, absorbing, or reflecting materials significantly different in acoustic properties. (Say the center area for the EEG electrode is acoustically matched to soft tissue but surrounded by a ring of highly acoustically-reflecting material). In an implementation, system 700 can include multiple holder units 310, with each holder unit 310 having one or more ultrasound transducers or transducer arrays 620 and electrodes 630. For example, referring to the figure, transducer or transducer array 620-2 can be in a different holder, electrode 630-2 in a second one, and transducer 620-1 & electrode 630-1 in a third holder. Holder unit 310 or holder units 310 include mounting mechanisms.
In one implementation, the patches (e.g., made of cold gum, hair pomade, or Play-Doh-like pliable substances that can be reshaped without crumbling) can have a gel with a transition temperature close to the body temperature. At room temperature, the gel can remain solid and not drip during storage and handling for application. On the head, gentle heating (from body temperature or external heating—hair dryer or built-in heating mechanisms in the holder unit 310) can liquefy the gel and make good contact with the head. In one implementation, the patches are kept at a lower temperature (e.g., in a refrigerator) until ready to use. In an implementation, holder unit 310 holds small reservoirs of gels, saline solution, etc. A small hole or perforation allows the gel/saline solution to drip into the patch unit and spread onto the head.
In one implementation, holder unit 310 includes a puncturing method to create the small hole or perforations to allow the gel/saline to drip to the head. The flow from the reservoir can be activated by gravity, mechanical, or pressure. The gel can be composed of easier-to-clean chemicals such as alcohol that evaporates like Purell® or can blend in like hair products and skin lotions after the EEG or tFUS session. In one implementation, the patch is water activated. A user dips the patch in water and applies it to the head. In one implementation, holder unit 310 can increase or reduce the pressure on the patches to improve contact with the head using turnscrews, etc. In an embodiment, patches are made of polyacrylate gel or similar super-absorbent gels that can be pressed to release some liquid for better coupling to the head or head. They can absorb much of the liquid upon release of pressure. Said replaceable patches can be used one-time or multi-times and can be obtained via one-time purchasing or subscription. An app that controls the tFUS and EEG system can also be set up to place an order after a set number of uses.
Once outside the pressure field 670, traditional electrical wires can be used. The wire channel 650, like the electrode 630, can be constructed to minimize vibrations and can be composed of multiple materials or sections. A simple example is that the electrode and wire channel can be made of a channel of saline or electrically-conductive gel for the portion in the ultrasound path. In another implementation, the electrode and wire channel are constructed of conductive material such as doped plastic or silicone. Such doped materials can have acoustic properties well-matched to tissue. In a simple example, if doping is known to cause an increase in density and speed of sound of the mixture, a base plastic or silicone with slightly less density and speed of sound than soft tissue can be used such that the resulting doped material can have similar density and speed of sound to soft tissue. In one implementation, electrode 630 is made by embedding one or more conductive channels in a non-conductive base such as plastic or silicone.
The conductive channels contain a saline solution or other conductive gels, etc. In
In
EEG voltages are of a very small magnitude (10 to 100 μV) and are very susceptible to noise. Electrical noise can arise from EMI or the ultrasound transducer's operation (for example, via capacitive coupling or direct current leakage). EEG operation can be insulated from the ultrasound transducer array; the insulation can protect from both EMI (air-transmitted, without any direct conductive pathway) and direct conductive connection.
Gel layer 632-3 separates electrode 630 and an electrically insulating layer 665. Insulating layer 665 provides electrical isolation between EEG electrical system (electrode 630, wire channel 650, etc.) and the ultrasound transducer or array 620. Gel layer 632-2 separates insulating layer 665 and an electrically conductive shielding layer 645. Shielding layer 645 is connected to a grounding wire 655. Shielding layer 645 can act as Faraday cage or shield, for example, using a wire mesh cage or similar conductive structure to provide electrical isolation from electrical noise caused by ultrasound vibrations incident and/or reflected. Grounding wire 655 is electrically isolated from the head and EEG electrical system and is connected to an appropriate electrical ground. Shielding layer 645 shunts EMI and currents from transducer 620. The combination of shielding layer 645 and insulating layer 665 provides the best reduction in electrical artifacts for both EMI and direct conductive connection. However, in some implementations, using only one shielding layer 645 or insulating layer 665 can suffice. Ultrasound array 620 is separated from the shielding layer 645 by a gel layer 632-1. Other arrangements using conductive shielding 645 and insulating layer 665 are possible. The ultrasound-transmitting, electrically-conducting layers (630, 645) can be implemented using techniques described in
The head introduces a number of complexities to both transcranial ultrasound methods (both for imaging and modulation of brain activity) and for EEG recordings. The head is highly aberrating to ultrasound fields and can be corrected for. The head and head also smear EEG signals, making them significantly lower in signal-to-noise ratio, temporal resolution, and spatial resolution compared to ECoG recordings from on top or just below the dura mater. These difficulties, unfortunately, can be handled using better hardware (ultrasound arrays and electrode arrays) and algorithms (to correct for the head and head). However, in addition to those issues, the rigidity and various local curvatures of the head, combined with the relative thinness of the head, makes solid coupling of systems to the head difficult. Small dimples and protrusions can be particularly problematic. Furthermore, the presence of hair can be a significant barrier to good ultrasound and electrical coupling. To better address these issues for both ultrasound and EEG, we describe a system using posts, in post holders, to transmit ultrasound and electrical signals for use in combined tFUS and EEG.
The posts are designed to be capable of getting between hair or individually conform to and contact better the skin and any small dimples or roughness on the skin. In one example the posts can include a semi-stiff brush (a 2D array of bristles/posts) where the individual bristles are utilized for good coupling acoustically and electrically. This approach is compatible with various types of transducer and transducer array geometries. While each post can have some give and adjustability in the direction orthogonal to the head (up and down), for the ultrasound-transmitting posts, their lateral location contacting the head can remain rigid, constant and known. This is because changing their location along the head can change where they effectively are transmitting ultrasound to and recording ultrasound from. This information can be utilized for accurate head aberration correction algorithms. While modern technology can detect such deflections in the posts, the cost and complexity of doing so in the tight confines of the system can be difficult. However, it is acceptable for the holders of these posts to be mounted on a flexible backing. This is because if the holders and posts are sufficiently rigid, the backing's curvature can be measured in any number of methods including via a network of built-in strain gauges or optical methods, and hence the post tip locations are known. The 2D curvature of the backing is relatively easy to measure. This is simpler than attempting to determine the precise 3D location of the tips of each and every post, especially in the hair, if the posts or holders had slack or were pliable. EEG posts and ultrasound transmitting posts can be electrically conductive based on at least one of: patches of conductive gel, patches of conductive film, doping, metal coating, or metal strands embedded in the one or more EEG posts. EEG posts and ultrasound transmitting posts can be electrically conductive based on metal strands that have a diameter less than the ultrasound wavelength, and a distance between the strands that is greater than the ultrasound wavelength. EEG posts and ultrasound transmitting posts can have conductive gel coatings bonded to the one or more EEG posts. In some examples, EEG posts and ultrasound transmitting posts can be constructed to be acoustically similar so that the same post or same post construction can be used for EEG and/or ultrasound operation.
Holder unit 1305 can be made of one or more materials or layers to provide the necessary properties. For example, holder 1305 can have an outer silicone layer to provide electrical and ultrasound isolation and an inner layer made of metal or ceramic to provide rigid mechanical support to the post 1340. Post 1340 can be of single construction or contain internal channels or structures such as 1350. Spring layer 1330 allows for a degree of movement of the post along its length, orthogonal to the head, allowing for better contact even with local dimples or bumps on the head. The structure of holder 1305 prevents the lateral displacement of the post 1340. Spring layer 1330 can be compliant and have acoustic properties matched to the post and soft tissue. Additional details regarding spring layer 1330 are discussed below. An additional optional assembly unit 1310, described later, can be placed below post 1340. Note that spring layer 1330 can also extend in between post 1340 and assembly unit 1310 or below assembly unit 1310. Alternatively, assembly unit 1310 can simply be a continuation of the spring layer 1330. The bottom of holder 1305 can be enclosed or opened such that the bottom surface of spring layer 1330 or assembly unit 1310 can be exposed instead. The figure depicts a single specific configuration for illustrative purposes only and is not meant to be a limitation of the aforementioned minor configuration details and differences.
Additional considerations for EEG-supporting post components 1345/1355 make it electrically conductive. Strands of metal (or metal wires) fully embedded within post 1345 are unlikely to vibrate and pick up mechanical vibration artifacts. Films and gel coatings are unlikely to pick up mechanical vibrations when strongly bonded to the bulk of post 1345. Similarly, saline and ionic gels in channel area 1355 are unlikely to pick up mechanical vibrations as their acoustic properties are similar to Post 1345. Similarly, EEG operation is shielded from EMI (electromagnetic interference) and other electrical interference. Shielding techniques employed will be described in more detail. For EEG-compatible post 1345, spring layer 1330 can also be conductive electrically, i.e., doped silicone that is conductive electrically. In one example embodiment, for a matrix array with a 1 mm pitch, post 1340/1345 outer diameter is 0.7 mm, while holder 1305 is of a square shape with later dimensions of 1.0 mm with a wall thickness of 0.15 mm at the top where the post 1340 slides through, with a slightly less wall thickness below where the spring layer 1330 is placed to allow for its expansion or compression as needed.
In one embodiment, an array of holder units 1305 are placed on a transducer or transducer array. When placed on a matrix array, aligning each holder unit 1305 and each post to a single array element is particularly suitable. In another embodiment, embedded within Holder unit 1305 is assembly unit 1310 (1315 in
Alternatively, in one embodiment, included at the tip of each post 1340 is a couplant assembly unit 1350. Couplant assembly unit 1350 can include gel tips, rubber, or silicone and make contact with the head. Couplant assembly 1350 can be flat or convex shaped to allow for good contact with the head. Couplant assembly 1350 can contain a channel connecting to a gel or saline reservoir outside holder 1305. The diameter of Couplant assembly 1350 is the same as that of the inner diameter of Post 1340. In one example embodiment, posts are hollow and concentric with channels for liquids or gels. In a different embodiment, couplant assembly unit 1350 includes nubs (not shown explicitly) with small refillable reservoirs for liquids or gels. When post 1340 is pressed against the head (pressure or spring activated) or due to gravity, a small amount of fluid can ooze out to form a couplant on the head. This reduces the acoustic impedance mismatch caused by any air pockets between post 1340 and head 110. Materials used for post 1340, couplant assembly unit 1350, and spring layer 1330 are acoustically matched. Assembly unit 1310, spring layer 1330, post 1340, and couplant assembly unit 1350 are collectively referred to as an ultrasound post module or ultrasound post. As mentioned, multiple such modules can be used in a single tFUS and EEG system.
The EEG post can be made electrically conductive by either making the surface conductive or by embedding conductive channels (channels not shown in the figures) within the non-conductive material of the EEG post. EEG posts can be made conductive using a combination of the above; for instance, it can be made conductive using a combination of conductive gels or films and metal wires or strands. Special care is taken to ensure no mutual interference in the operation of the ultrasound and EEG posts. In an implementation, couplant unit 1355 comprises a conductive gel or conductive solution in electrical contact with the conductive portion of post 1345.
The use of posts, combined with independent holders, between which further electrical shielding or ultrasound isolation (via reflection or absorption) can be done, allows for a unique method to reduce the effects of known aberrations and artifacts in 1) ultrasound transmission and imaging and 2) EEG recording, while solving the complexity of achieving 3) good acoustic and 4) low electrical impedance coupling on the 5) head and even through 6) hair.
In addition to the previous considerations of eliminating US aberrations and EEG artifacts applied to the general electrode and transducer configurations, the post-based implementation allows for further discussion of specific implementations.
The figure illustrates System 1500 to be flat and rectangular shaped. System 400 can be constructed to be curved and concaved (an elongated U-shaped like a headband) to make better contact with the head. In an implementation, the headband-shaped System 1500 has one or more extensions perpendicular (or angled) to the headband. In an embodiment, System 1500 is constructed like a helmet to cover most of the head and can extend over the forehead and temple regions of the head 110. System 1500 can be constructed using other structures like visors, half-helmet, half-headband, etc.
In an embodiment, ultrasound and EEG posts are constructed to support both ultrasound and EEG functionality. In one implementation, the functionality can be supported simultaneously. In another implementation, the functionality of the post can be configured at run time, for example, using an electrical switch. In one embodiment, all post 1340 are of the same length. In another embodiment, posts 1340 are different lengths and can be used as delay lines (effectively a lens or to adjust ultrasound focusing). System 1500 can include islands of EEG and ultrasound posts in one embodiment. In addition, System 1500 can be constructed on a flexible substrate. In one implementation, multiple flexible patches of System 1500 are mounted on a stiffer substrate to allow further conformity to the individual shape of the head. In these cases, the ultrasound coupling can be maintained between the ultrasound transducer or transducer array element, the ultrasound posts, and the head. With ultrasound arrays, the arrays themselves can be mounted on a flexible substrate and coupled to a System 1500 on a flexible substrate. Alternatively, each holder unit and post can be mounted individually to each array element. In another implementation, smaller patches of stiffer arrays and stiffer System 1500 are coupled to each other, with these smaller patches on a flexible backing. In another implementation, an ultrasound transducer or array with a stiff emitting surface can have a softer coupling interface (e.g., silicone or hydrogel or a conforming water bag in plastic) and allows for the interfacing with a System 1500 built on a flexible substrate.
At least one technical advantage of the disclosed techniques relative to the prior art is that, with the disclosed techniques, a tFUS and EEG system can include an individual holder unit that includes ultrasound and EEG operation concurrently, unlike existing devices. With the disclosed tFUS and EEG techniques, an EEG electrode can be located, for example, to avoid a direct ultrasound pressure field generated by the ultrasound transducers. This can shield the EEG electrode from vibrations and thereby reduce EEG noise relative to other systems. The disclosed systems can also shield the EEG electrode from vibrations and electrically induced noise using additional developments disclosed herein. These technical advantages provide one or more technological advancements over prior art approaches.
Aspects of the subject matter described herein are set out in the following numbered clauses.
1. In some embodiments, a system comprises one or more ultrasound transducers, one or more electroencephalogram (EEG) electrodes, and a holder unit that holds a particular EEG electrode of the one or more EEG electrodes in a predetermined position relative to an ultrasound pressure field of a particular ultrasound transducer of the one or more ultrasound transducers to reduce noise in EEG data.
2. The system of clause 1, further comprising a plurality of electrically isolated areas at a bottom surface of the holder unit configured to make contact with a head.
3. The system of clauses 1 or 2, wherein the plurality of electrically isolated areas are electrically non-conductive, wherein a first subset of the plurality of electrically isolated areas correspond to the operation of one or more ultrasound transducers, and a second subset of the plurality of electrically isolated areas correspond to the operation of one or more EEG electrodes.
4. The system of any of clauses 1-3, wherein at least a subset of the plurality of electrically isolated areas are electrically non-conductive.
5. The system of any of clauses 1-4, wherein at least one of the one or more EEG electrodes is connected to an electrically conductive channel comprising acoustic properties matched to soft tissue.
6. The system of any of clauses 1-5, wherein at least one of the one or more EEG electrodes is connected to an electrically conductive channel that passes through non-conductive embedding material within the holder unit.
7. The system of any of clauses 1-6, wherein the electrically conductive channel is made electrically conducive by using an electrically conductive gel or a saline solution.
8. The system of any of clauses 1-7, wherein the electrically conductive channel is made electrically conductive by electrically doping a portion of the non-electrically conductive embedding material.
9. The system of any of clauses 1-8, wherein at least one of the one or more EEG electrodes is made electrically conducive by using electrically conductive gel or saline solution
10. The system of any of clauses 1-9, wherein at least one of the one or more EEG electrodes is made electrically conducive by electrically doping a portion of the non-electrically conductive embedding material.
11. The system of any of clauses 1-10, wherein at least one of the one or more EEG electrodes comprises a narrow conductive strand with a cross-sectional dimension that is less than a wavelength (A) of ultrasound waves generated by the one or more ultrasound transducers to reduce noise in the EEG data.
12. The system of any of clauses 1-11, further comprising one or more electrically conductive wire channels for the one or more EEG electrodes, wherein the one or more electrically conductive wire channels comprise a narrow conductive strand with a cross-sectional dimension that is less than a wavelength (A) of ultrasound waves generated by the one or more ultrasound transducers to reduce noise in the EEG data.
13. The system of any of clauses 1-12, wherein at least one of the one or more EEG electrodes comprises a conductive mesh of strands with a cross-sectional dimension that is less than a wavelength (A) of ultrasound waves generated by the one or more ultrasound transducers to reduce noise in the EEG data.
14. The system of any of clauses 1-13, further comprising one or more electrically conductive wire channels for the one or more EEG electrodes, wherein the one or more electrically conductive wire channels comprise a conductive mesh of strands with a cross-sectional dimension that is less than a wavelength (A) of ultrasound waves generated by the one or more ultrasound transducers to reduce noise in the EEG data.
15. The system of any of clauses 1-14, wherein at least one of the one or more EEG electrodes is connected to a stack of one or more layers, wherein the stack of one or more layers comprises an electrically conductive and at least one of ultrasound absorbing couplant, an ultrasound reflecting material, or any combination thereof.
16. The system of any of clauses 1-15, wherein electromagnetic interference (EMI) is reduced using a stack of a plurality of ultrasound transmissive layers, wherein the plurality of ultrasound transmissive layers comprises at least one electrically insulating layer and at least one electrically conductive shielding layer.
17. The system of any of clauses 1-16, wherein embedding material within the holder unit is ultrasound transmissive.
18. The system of any of clauses 1-17, further comprising a ground shielding layer connected to a grounding wire, wherein the ground shielding layer provides electrical isolation from electrical noise.
19. In some embodiments, a method comprises providing a holder unit, and holding, using the holder unit, a particular EEG electrode from one or more EEG electrodes in a predetermined position relative to an ultrasound pressure field of a particular ultrasound transducer of the one or more ultrasound transducers to reduce noise in EEG data.
20. The method of clause 19, further comprising providing a plurality of electrically isolated areas at a bottom surface of the holder unit.
21. The method of clauses 19 or 20, wherein the plurality of electrically isolated areas are electrically non-conductive wherein a first subset of the plurality of electrically isolated areas correspond to the one or more ultrasound transducers, and a second subset of the plurality of electrically isolated areas correspond to the one or more EEG electrodes.
22. The method of any of clauses 19-21, wherein at least a subset of the plurality of electrically isolated areas are electrically non-conductive.
23. The method of any of clauses 19-22, wherein at least one of the one of the one or more EEG electrodes is connected to an electrically conductive channel comprising acoustic properties matched to soft tissue of the head.
24. The method of any of clauses 19-23, wherein at least one of the one of the one or more EEG electrodes is connected to an electrically conductive channel that passes through non-conductive embedding material within the holder unit.
25. The method of any of clauses 19-24, wherein at least one of the one of the one or more EEG electrodes comprises a narrow conductive strand with a cross-sectional dimension that is less than a wavelength (A) of ultrasound waves generated by the one or more ultrasound transducers to reduce noise in the EEG data.
26. The method of any of clauses 19-25, wherein at least one of the one of the one or more EEG electrodes comprises a conductive mesh of strands with a cross-sectional dimension that is less than a wavelength (A) of ultrasound waves generated by the one or more ultrasound transducers to reduce noise in the EEG data.
27. The method of any of clauses 19-26, wherein at least one of the one of the one or more EEG electrodes is connected to a stack of one or more layers, wherein the stack of one or more layers comprise an electrically conductive and at least one of ultrasound absorbing couplant, an ultrasound reflecting material, or any combination thereof.
28. In some embodiments, an apparatus comprises one or more ultrasound transducers, one or more electroencephalogram (EEG) electrodes, and a holder unit that holds a particular EEG electrode of the one or more EEG electrodes in a predetermined position relative to an ultrasound pressure field of a particular ultrasound transducer of the one or more ultrasound transducers to reduce noise in EEG data.
Any and all combinations of any of the claim elements recited in any of the claims and/or any elements described in this application, in any fashion, fall within the contemplated scope of the present invention and protection.
The descriptions of the various embodiments have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Aspects of the present embodiments can be embodied as a system, method or computer program product. Accordingly, aspects of the present disclosure can take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that can all generally be referred to herein as a “module,” a “system,” or a “computer.” In addition, any hardware and/or software technique, process, function, component, engine, module, or system described in the present disclosure can be implemented as a circuit or set of circuits. Furthermore, aspects of the present disclosure can take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.
Any combination of one or more computer readable medium(s) can be utilized. The computer readable medium can be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium can be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.
Aspects of the present disclosure are described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine. The instructions, when executed via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions/acts specified in the flowchart and/or block diagram block or blocks. Such processors can be, without limitation, general purpose processors, special-purpose processors, application-specific processors, or field-programmable gate arrays.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams can represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block can occur out of the order noted in the figures. For example, two blocks shown in succession can, in fact, be executed substantially concurrently, or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
While the preceding is directed to embodiments of the present disclosure, other and further embodiments of the disclosure can be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims priority to and the benefit of U.S. Provisional patent application titled, “APPARATUS COMPATIBLE WITH PHYSIOLOGICAL MEASUREMENT SYSTEMS AND ULTRASOUND BEAM GUIDANCE FOR NEURO NAVIGATION,” filed on Jul. 28, 2023, and having Ser. No. 63/516,463, U.S. Provisional patent application titled, “SHIELDING TECHNIQUES FOR APPARATUS COMPATIBLE WITH PHYSIOLOGICAL MEASUREMENT SYSTEMS AND ULTRASOUND BEAM GUIDANCE,” filed on Jul. 28, 2023, and having Ser. No. 63/516,465, U.S. Provisional patent application titled, “APPARATUS COMPATIBLE WITH PHYSIOLOGICAL MEASUREMENT SYSTEMS AND ULTRASOUND BEAM GUIDANCE CONFIGURED WITH ULTRASOUND AND EEG POSTS,” filed on Jul. 28, 2023, and having Ser. No. 63/516,469, and U.S. Provisional patent application titled, “CRANIAL ACOUSTIC COUPLING APPARATUS AND METHODS,” filed on Dec. 6, 2023, and having Ser. No. 63/607,032. The subject matter of these related application are hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63516463 | Jul 2023 | US | |
| 63516465 | Jul 2023 | US | |
| 63516469 | Jul 2023 | US | |
| 63607032 | Dec 2023 | US |
