Patent Application: US-60246908-A

Abstract:
a method comprising generating a mechanical signal in a mammal , the mechanical signal having a frequency no more than 50 , 000 hz , transmitting the mechanical signal through the musculoskeletal system in the mammal , and sensing the mechanical signal from the musculoskeletal system . a method of triggering an internal event comprising generating a mechanical signal internal or external to a mammal , transmitting the signal through the musculoskeletal system of the mammal , detecting the mechanical signal , and triggering an event in response to the mechanical signal . a method of drug delivery comprising generating a mechanical signal internal or external to a mammal , transmitting the signal through the musculoskeletal system of the mammal , detecting the mechanical signal , and delivering the drug in response to the mechanical signal .

Description:
as fig1 illustrates , embodiments of an intra - body communication system 100 may comprise a stimulator 101 that produces mechanical excitations yielding vibrations or a signal , a portion 103 of the mammalian musculoskeletal system that conduct the vibrations or signals , and a receiver / sensor 105 that detects the vibration . in another embodiment , the direction of communication is reversed . in another embodiment , only one of the components is external to the individual while the other is internal in the body . in another embodiment , both receiver and transmitter are internal . in another embodiment , the method may be extended across more then one individual . as used herein , a mechanical vibration or signal may refer to any vibration or signal that is transmitted non - electrically . in other words , the vibration or signal does not rely on electromagnetic or electrostatic signals such as radio waves for transmittal . in embodiments , bone conduction may be excited externally . for example , vibrators on mobile phones can be used to generate frequency patterns in the lower audible range . in an embodiment , the stimulator may be an electro - mechanical stimulator , electro - magnetic stimulator or a piezoelectric stimulator . low - frequency vibration patterns are commonly generated by either vibration motors or electromagnetic shakers . in vibration motors , the amplitude and frequency may be coupled through a mechanical link to an eccentric weight . increasing the motor speed may also increase the excitation . electromagnetic stimulators or shakers and piezo - electric stimulators allow for a separation between amplitude and frequency . through power limiting components a flat power spectrum of the shaker can be achieved , allowing robust data communication between different devices at alternate frequency ranges . in other embodiments , the user 103 may be the stimulation or vibration source . a user can easily produce bone vibrations , e . g ., through teeth clicks and finger snaps . such user initiated excitation can be readily used for interfacing with the embodiments of the system . furthermore , a user may tap the skin or make a motion with a limb to generate a mechanical vibration . the stimulator 101 may be placed in any location in or on the body . thus , embodiments of the system 100 enable wireless body - area communication based on mechanically excited bone conduction inside the human musculoskeletal system . example of locations for placing stimulator 101 include without limitation , wrist , throat , head , heart , lungs , skull , ankle , leg , etc . embodiments of the system 100 are intended as a secure , reliable , low - power , low cost , and low - data rate alternative to existing rf technologies . measurements and theoretical analysis have shown that ultra low - power ( i . e . & lt ; 1 mw ) excitation is enough for fairly reliable communication (& lt ; 10 % bit error rate ), without being noticeable to the user . adding error compensation methods may reduce that error . the receiver or sensor 105 may comprise any suitable sensor , which is sensitive enough to detect vibrations or signals from the body . alternatively , one or more sensors 105 may be used . examples of sensors that may be used include without limitation , a microphone , an accelerometer , or combinations thereof . in a specific embodiment , the sensor 105 is a mems based three - axis accelerometer . the sensors are preferably are low - power sensors , thus making the system extremely power efficient . in embodiments , the sensors may use power in the range of between about 1 mw and about 100 mw , alternatively between about 2 mw and 50 mw , alternatively between about 0 . 1 mw and about 2 mw . receiver or sensor may be located or disposed within the body or external to the body . in one embodiment shown in fig5 , the sensor may be worn on the wrist much like a wristwatch . in some embodiments , system 100 may further comprise charge converters and amplifiers coupled to the sensor 105 and / or the stimulator 101 . any charge converters and amplifiers known to those of skill in the art may be used . initial investigation and experimental results have shown that embodiments of the system have the potential to interconnect body - worn or implanted devices and provide users with alternative ways to interact with them . in particular , system 100 may be free of radiation and require extremely low power to maintain a connection and transfer data . another advantage of the disclosed systems and methods is the two - way exchange of information between implanted devices and / or receivers . in an embodiment , system 100 may interact with body - worn devices in a hand - free fashion , e . g ., to answer a phone call through the bluetooth headset by a teeth click . furthermore , the system 100 may manage a power - hungry rf wireless body - area connection as a secondary ultra - low power channel , or wake - on - vibration . for example , a bluetooth connection between a headset and a cell phone can be shutdown between calls and be reestablished upon a request from the cell phone through embodiments of the system . an additional advantage of system 100 is that body - area data communication may be maintained in a hostile environment , where radio frequencies are likely to be jammed or insecure . in embodiment of a method of intra - body communication , a stimulator 101 initiates or generates a mechanical vibration in a user 103 . as discussed above , the stimulator may be placed at any location in or on the body of the user . the mechanical signal is transmitted through the musculoskeletal system of the user . in embodiments , the mechanical signal is encoded using frequency and / or amplitude modulation . in this way , the mechanical signal may carry data such as blood pressure , heart rate , or other body parameters to receiver 105 . it is emphasized that the disclosed methods and systems are different than ultrasound techniques , which rely on the reflection of ultrasonic high frequency sound waves for imaging purposes . in an embodiment , the mechanical signal or vibration is generated at a frequency from about 5 hz to about 50 , 000 hz , alternatively from about 10 hz to about 10 , 000 hz , alternatively from about 50 hz to about 5 , 000 hz . preferably , the mechanical signal is a signal having a frequency no more than about 20 khz . that is , the mechanical signal is generally below frequencies considered to be in the ultrasound range . the mechanical signal may be transmitted through the bones and cartilage of the patient 103 or mammal . a sensor or receiver 105 then detects the mechanical signal . in addition , receiver 105 may decode or demodulate the mechanical signal to receive the data encoded within the mechanical signal . in response to the detected signal , sensor 105 may initiate an action ( i . e . drug delivery ), output data received from stimulator 101 , activate an alarm , send information back to origin using the same technique in reverse , etc . accordingly , it is envisioned that the disclosed systems and methods may be used in numerous applications . in one embodiment , the method and system may be used for drug release applications . for example , an internal drug dispensing device may be implanted within a patient . sensor 105 may be coupled to the drug dispensing device . in response to a mechanical signal ( e . g . teeth click or a signal generated from a stimulator 101 ) sensor may detect signal and instruct drug dispensing device to release drugs into the body . sensors may detect the effectiveness of the drug and allow the user to trigger another dose release after communication with the stimulator . such systems may allow for patient targeted treatment . this may be particularly useful in chronically ill patients , diabetic patients or patients undergoing cancer treatment . in another application , the disclosed systems and methods may be used in health monitoring . for example , a biosensor may measure a body parameter such as without limitation , blood sugar , body temperature , oxygen saturation , heart rate , and the like . the biosensor may send this data to stimulator 101 to transmit the data through the musculoskeletal system of the patient 103 . receiver 105 may detect and decode signal and output the data received to an output display ( e . g . lcd screen ) or may store data on storage medium such as without limitation , a flash card , hard drive , or other devices known to those of skill in the art . the information , raw or processed , may then be forwarded to a base station ( e . g . computer ), a smart phone , or cell phone . depending on the complexity of the system setup the information may be forwarded directly to a physician &# 39 ; s office or nurses station , first responders , or other qualified personnel . embodiments of the systems and methods may also be used for identification purposes . without being limited by theory , it is believed that each individual will have different transmission or conduction rates of mechanical signals through the musculoskeletal system . furthermore , as a mechanical signal pass through each person &# 39 ; s musculoskeletal system , the signal may be distorted in a unique way or pattern which may be used to identify an individual . as such , in an embodiment , a stimulator may be placed on the skin of a suspect or person to be identified . a mechanical signal may be generated by the stimulator and the receiver , placed on a different or the same area of the body , may detect the generated mechanical signal after passing through the person &# 39 ; s musculoskeletal system . using pattern recognition , the receiver may positively or negatively identify the tested individual according to the signal detected . alternatively , an individual may be already implanted with one of the components . in a further application , embodiments of the systems and methods could be used in medical diagnosis . specifically , a medical emergency professional may be able to diagnose conditions in the field such as without limitations , ligament tears , cartilage damage or hairline fractures and bone damage . normally , a patient may have to wait until a full x - ray , computed tomography or magnetic resonance imaging dataset has been taken in order to for a proper diagnosis to be made . without being limited to theory , it is believed that an injury to a healthy bone or ligament may have distorted a mechanical signal in one way . or a healthy bone or ligament may transmit a mechanical signal differently than injured tissue . using an embodiment of the disclosed system , differences in the signal or rate of transmission may alert a professional of a possible fracture , tissue damage or tissue injury . in other embodiments , damage to organs or other tissue types may also be diagnosed besides musculoskeletal injuries . in other embodiments , damage or loosening of implants , functional parameters of implants or the quality of the implant tissue interface may also be diagnosed . in yet another application , embodiments of the disclosed methods and systems may be used for assisting handicapped individuals . for example without limitation , a handicapped person could click his or her teeth to activate a cell phone or other device strapped to his or her body ( e . g . wrist , ankle , etc ). in such applications , the receiver may also be a wireless transmitter enabling the user person to operate external devices through teeth clicks or other rudimentary motions . to further illustrate various illustrative embodiments of the present invention , the following examples are provided . a reaction - type low - power electromagnetic shaker was built to generate mechanical signals through dynamic forces . this type of shaker offers a lightweight and compact configuration , ideal for miniaturization . in addition , such shakers are designed for operation over a very wide range of frequencies . bone - conduction was detected using accelerometers with coupled amplifiers . an ultra low - power mems based three - axis accelerometer from kionix was held against the receiving body location as the receiver . a labview program controlled the entire system . binary input sequences were modulated into different frequencies to drive the electromagnetic shaker . the same program received the signal from the accelerometers and demodulated the signal . the received bit sequence was then compared to the input sequence to calculate accuracy . in a first testing series , human subjects were exposed to a localized low - frequency excitation signal pattern at the wrist and receivers were placed at the lower back or the skull . at a second series , the excitation source was at the lower back and receivers measured the response at the wrists and the skull . human subjects were recruited and consented to this study . for the first testing series , subjects placed their forearm in the custom built testing jig . the exciter was placed against the distal ulna with a constant pre - load of 20 n . multiple tri - axial mems accelerometers were placed along the elbow , shoulder , skull and lower back and attached to the skin through adhesive . reliable signal transmission was monitored after varying power consumption of the system . subsequently , the anatomic site at which the excitation is applied was altered and the test repeated . bit error rate ( ber ) based on the 2048 random bit combinations were calculated and reported . ask ( amplitude shift - keying ) and fsk ( frequency shift - keying ) for data communication was examined , primarily due to their simplicity . a labview program was developed to encode the raw bits into modulated signals to control the input voltage of the electromagnetic shaker , as described above . in fsk modulation , on and off frequencies are chosen for constant amplitude . the range of on frequencies used was between the lower shaker bound of 10 hz and a selected upper bound of 2000 hz , with the off frequency being defined in terms of the on frequency interval . the receiver determined the frequency using labview &# 39 ; s built - in buneman frequency estimator . for ask modulation , the input signal frequency was held constant , while different amplitude values were assigned to a chosen bit pattern . a 0 - 0 . 001 g off amplitude of the acceleration signal and 0 . 1 - 1 . 0 g on amplitude of the acceleration signal was applied . the unit g represented the earth gravitational acceleration of 9 . 81 m / s ̂ 2 . fsk consistently outperformed ask in accuracy when similar vibration forces were employed . ask suffered more from the muscle attenuation and changes in muscular contraction . the demodulator of fsk was much simpler and more robust than that of ask . therefore , we focused on the properties and performance of fsk in the follows . secondly , 300 - 350 hz was best for fsk for the arm bone examined . frequency sweeps were performed over the range of 10 - 2000 hz . the frequency range between 300 - 350 hz demonstrated the least amplitude attenuation , as showed in fig3 . our later experiments showed this frequency range also works well for other part of the skeleton system and for other subjects . fig4 summarizes the measurement results . the experimental system achieved & lt ; 10 % bit error rate without any error correction . this result was quite exciting because all four links involve multiple bones and several joints . second , the performance was asymmetric . for example , the female subject had much lower ber from the wrist to the lower back than from the lower back to the wrist . thirdly , the difference between subjects was considerable . on average the male subject accumulated a much lower ber . causes of that discrepancy will need to be further investigated . an ultra - low power receiver was built in the form factor of a wrist - watch , which is shown in fig5 . it employed the same ultra - low power three - axis accelerometer used in example 1 and an ultra - low power microcontroller ( msp 430 ) from texas instruments . the active power consumption during receiving was below 5 mw . the device is capable of activating sequences and programs after minimal wrist flicking . in addition , the current version allows bluetooth communication with cell phones for data communication outside the proposed system . in embodiments , the wristwatch functions as base station and communication link to other body worn devices and external mobile systems . the bone - conduction signal of teeth clicks is characterized by high energy in spectrum above 2000 hz , but low energy below it . fig6 shows the time - spectrum of the bone conduction signal of several teeth clicks . the spectrum of the bone - conduction signal of speech , as shown in fig7 , is almost the opposite . it is characterized by high energy in spectrum below 2000 hz , but low energy above it . this dramatic difference is introduced because the skin and skull inherently are a much lower low - pass filters to acoustic signals than the bone tissue due to vibration incurred by teeth clicks . this forms the basis for our algorithm to detect teeth clicks . for low - power and real - time implementation , an algorithm was designed based on the property of the bone - conduction signal . the algorithm examined the energy densities in the lower and higher spectral ranges of the bone - conduction signal . high energy density in the lower spectral range indicated the existence of speech , while a sudden increase in the energy density in the higher spectral range indicated the occurrence of a teeth click . a deliberate teeth click was detected if a teeth click occurred without the presence of speech . the experimental implementation was based on standard speech signal processing . the bone - conduction signal was sampled and divided into overlapping frames . in the implementation , each frame was about 23 . 3 ms and adjacent frames are about 22 ms apart . for each frame , the fast fourier transformed signal ( fft ) was calculated to obtain the frequency spectrum . the “ low ” spectral range was between 0 and 2750 hz , while the “ high ” spectral range was between 1875 and 5500 hz . for the nth frame , the energy densities were calculated in the low and high spectral ranges , denoted as a n and b n , respectively . records were kept of the average energy density of silence , u . if b n was considerably larger than b n − 1 and b n + 1 , the algorithm declared that a teeth click was detected . for accidental teeth clicks , a n − 1 and a n + 1 were large due to the presence of speech . therefore , the algorithm declared that a deliberate teeth click was detected if and only if bn is considerably larger than b n − 1 and b n + 1 and a n − 1 and a n + 1 is on the same level as the u . let be the boolean logic that evaluates whether a deliberate teeth click is detected for the nth frame . it can be formulated as c n =[( b n − 1 + offset & lt ; b n )] and [( b n + 1 + offset & lt ; b n )] and [ a n − 1 ≦( u + offset ] and [ a n + 1 ≦( u + offset )] where offset is empirically set to 5 db . it is important to note that while the algorithm is based on the generic property of the bone - conduction signal , its implementation is highly dependent on the property of the transducer ( e . g . throat microphone ). in this implementation , the low and high spectral ranges as well as the offset were empirically determined by examining the bone - conduction spectrum . while the preferred embodiments of the invention have been shown and described , modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention . the embodiments described and the examples provided herein are exemplary only , and are not intended to be limiting . many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention . accordingly , the scope of protection is not limited by the description set out above , but is only limited by the claims which follow , that scope including all equivalents of the subject matter of the claims . the discussion of a reference in the description of the related art is not an admission that it is prior art to the present invention , especially any reference that may have a publication date after the priority date of this application . the disclosures of all patents , patent applications , and publications cited herein are hereby incorporated herein by reference in their entirety , to the extent that they provide exemplary , procedural , or other details supplementary to those set forth herein . 1 . nicholson , p . h . f ., moilanen , p ., karkkainen , t ., timonen , j . and cheng , s . guided ultrasonic waves in long bones : modelling , experiment and in vivo application . physiol . meas , 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: an event driven energy saving strategy for battery operated devices . proceedings of acm mobicom . 12 . zicheng liu et al , “ leakage model and teeth clack re - moval for air - and - bone conductive integrated micro - phones ”, proc . ieee int . conf . acoustics , speech & amp ; signal processing ( icassp ), philadelphia , 2005 .