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JP2017530627

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DESCRIPTION JP2017530627
Abstract Broadband intracorporeal communication systems use ultrasound to transmit data
through the body. MEMS devices, such as CMUT transducers, are configured to transmit and / or
receive ultrasound data signals within a wide band of operating frequencies. The transducer
transmits ultrasound data signals through the body to a similarly configured ultrasound receiver
and / or is transported through the body from a similarly configured ultrasound transmitter for
decoding and processing. Receive a sound wave data signal. In a preferred implementation, the
CMUT transducer operates in the collapse mode.
Broadband intracorporeal ultrasound communication system
[0001]
The present invention relates to a communication system using a liquid medium as a
communication medium, and more particularly to a miniaturized broadband intracorporeal
ultrasound communication system.
[0002]
It is often desirable to communicate with devices located within the human body.
For example, it may be desirable to receive information from an implanted device, such as a
pacemaker, or an implanted cardiac defibrillator. The physician will want to know the status of
the device, such as battery charging or pulse delivery information. It may also be desirable to
04-05-2019
1
send information from outside the body to the implanted device, such as to reprogram or change
the settings of the device. It may also be desirable to communicate with a catheter while the
catheter is in the patient's vasculature, such as during deployment of a stent by the catheter. For
example, during a procedure, images or measurements need to be provided to the attending
physician. It may be desirable to receive information from the tip of the needle during a biopsy or
ablation procedure. The information communicated to the physician can include data on the
placement of the needle or on the condition of the surrounding material.
[0003]
In ablation procedures, it is important to receive temperature and tissue density information to
determine the progress of the procedure. This information may be transmitted through the
catheter, the biopsy needle, or the wire in the ablation device, but because the catheter, needle, or
ablation device is small, wiring is also required for the device's own functionality In particular,
often only limited space can be provided for the communication line. In such situations, wireless
communication will eliminate the need for communication conductors through the device.
However, common wireless techniques, such as high frequency communications, are often
constrained by the environment in which they need to communicate. Electrical or
electromagnetic transmissions can be highly attenuated by the body and are subject to
interference from other medical devices such as magnetic resonance systems and pacemakers
that create a noisy environment for intracorporeal radio frequency communication there is a
possibility. Furthermore, radio frequency and electromagnetic communication can be
bandlimited when operating through tissue. An implantable device using an ultrasound
transducer in the frequency range of kHz for wireless communication is known from WO
2008/011570. The data transfer rate of such devices is limited. Therefore, it would be desirable
to provide a wireless intra-body communication system that can operate effectively from inside
the body and is not band limited.
[0004]
In accordance with the principles of the present invention, a broadband intracorporeal
communication system is described that uses ultrasound to transmit data through the body.
Ultrasound within a useful frequency band can pass through liquid media such as tissue without
the limitations and limitations encountered in radio frequency and electromagnetic
communication through the body. Preferred ultrasound transducers for such communication are
MEMS or electrostatic ultrasound micro transducers (CMUTs), which are controlled during
manufacture and implementation to provide a wide bandwidth of operating frequencies (e.g. 80)
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2
%) Can be shown. Most preferably, the CMUT device operates in a collapsed mode, the sensitivity
and operating band of which are set by selecting the appropriate bias voltage for the device.
When transmitting, the microelectronics CMUT device is operated by a microelectronic
transmission circuit comprising an amplifier / drive circuit and an optional data encoder. When
receiving, a microelectronic circuit is coupled to the CMUT to provide amplification and optional
decoding of the received signal. Preferably, one or more CMUT devices are fabricated on the
same die as the microelectronic communication circuit. The assembly can be a dedicated
transmitter or receiver, or a transceiver. In constructed embodiments, such an assembly
communicated up to 80 cm through a liquid medium such as that exhibited by human tissue.
[0005]
The present invention provides a unique combination of CMUT transducer characteristics, such
as wide bandwidth and various operating frequencies, with microelectronic circuit coding
functions. The data transfer rate for the broadband intra-body communication system according
to the invention can reach as high as Mb / sec.
[0006]
FIG. 5 illustrates several ways in which the ultrasound communication system of the present
invention can communicate through a liquid body, such as a human body. FIG. 1 illustrates a
intracorporeal ultrasound transmission system configured in accordance with the principles of
the present invention. FIG. 1 illustrates a through-the-body ultrasound system configured in
accordance with the principles of the present invention. FIG. 1 is a cross-sectional view of a
typical CMUT transducer cell. FIG. 2 is a schematic diagram of the electrical connections of a
typical CMUT cell including an applied bias voltage. FIG. 6 is a cross-sectional view of a CMUT
cell configured for collapse mode operation in accordance with the principles of the present
invention. FIG. 7 shows the CMUT cell of FIG. 6 when biased to the collapsed state. FIG. 7 shows
the CMUT cell of FIG. 6 when the cell's membrane is held in a collapsed state by a lens made on
top of the cell. FIG. 5 is a diagram showing typical broadband response characteristics of the
ultrasonic CMUT communication system of the present invention. FIG. 2 is a block diagram of a
microelectronic transceiver suitable for use in the ultrasound CMUT communication system of
the present invention.
[0007]
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With the increase in the number and capabilities of implantable medical devices, the need for
reliable, high-throughput, secure intra-body communication systems has emerged. There are
several technical options that can serve this need, such as radio frequency, magnetic or
ultrasonic communication. The suitability of this approach is determined by the characteristics of
the communication channel (human body) for each type of signal, the required size of the
implementation, and the achievable power / performance ratio. Furthermore, for each type of
signal, there are safety limits on the signal amplitude and duty cycle that can be used in the body.
When these considerations are made, ultrasound communication provides the best signal
propagation despite small form factors and energy consumption.
[0008]
Ultrasonic communication is of mechanical nature. An electrical signal driving an acoustic
transducer known as a CMUT causes mechanical motion of the membrane, which in turn
propagates pressure waves through the surrounding medium. The propagation characteristics
depend on the characteristics of the acoustic wave in terms of pressure, frequency and also on
the characteristics of the propagation medium. In the case of passage through the body, different
tissues propagate, reflect and absorb ultrasound differently. The efficient transmission principles
described below are necessary to ensure proper reception. The ultrasound transducer can
generate and receive modulated ultrasound data signals. Ultrasonic transducers usually have a
constant resonant frequency depending on their physical dimensions and implementation. The
desired CMUT implementation may be transmitted using a center frequency of 4 to 8 MHz,
which exceeds the 80% or 100% bandwidth, at a ratio of the operating frequency range of
operation to the center frequency. This is in contrast to conventional piezoelectric transducers
which have a typical bandwidth of 10% to 50%. The wide bandwidth achievable with CMUT
transducers enables the transmission of wideband digital signals.
[0009]
The ultrasound transmission characteristics of the body are in the frequency range of about 100
kHz up to about 40 MHz. Communication using low ultrasound frequencies, such as less than
100 kHz, results in poor spatial resolution (due to ultrasound diffraction) and also increases the
size of CMUT transducers. At higher frequencies, signal attenuation is increased, thus reducing
the maximum communication distance achievable with low power devices. In ultrasound
intracorporeal communication as described herein, signals are transmitted through ultrasound
transducers placed in the body or in good acoustic contact with the body surface. As shown in
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FIG. 1, several modes of use can be defined in terms of the physical location of the transceiver
relative to the communication medium. In FIG. 1a) the ultrasonic intracorporeal communication
device 52 in the liquid body 50 is through its medium to another ultrasonic intracorporeal
communication device 54 which is outside the body 50 and is in acoustic contact with the body.
Communicate. In FIG. 1 b) the ultrasonic intracorporeal communication device 52 outside the
liquid body 50 is in acoustic contact with the body medium and through the body medium
outside the body 50 and in acoustic contact with the body It is transmitted to another ultrasound
intracorporeal communication device 54. In FIG. 1 c), the ultrasonic intracorporeal
communication device 52 in the liquid body 50 is transmitting through its medium to another
ultrasonic intracorporeal communication device 54 which is also inside the liquid body 50. The
ultrasound intracorporeal communication device shown in FIG. 1 only shows active transmitters
/ receivers / transceivers comprising an ultrasound transducer as an antenna. In practice, the
communication device may be a stand-alone, battery powered device or may be attached to
catheters and other instruments that connect the communication device to external devices. In
general, with the device of the present invention, data can be transferred from one
extracorporeal device to another intracorporeal device, from one inside the body to another, from
one extracorporeal device through the body, and / or one another from another intracorporeal
device. Data communication is not limited to sending from a single transducer to a single
receiver, data can be sent from multiple transducers and received by multiple receivers. The type
of data depends on the particular application. In most implementations, the data includes digital
information.
[0010]
2 and 3 show block diagrams illustrating the main components of a CMUT-based ultrasound
communication channel, with the transmit channel shown in FIG. 2 and the receive channel
shown in FIG. The preferred operating frequency range of the channel is between 100 kHz and
40 MHz. FIG. 10 below illustrates these concepts combined into a transceiver configuration. As
shown in FIG. 2, the data generated by transmitter 62 is first encoded by data encoder 64, which
enables DC-free encoding. Manchester encoding is preferred to address the capacitive nature of
the CMUT used for transmission, but other types of DC free encoding can also be used. In non-DC
free coding schemes, the DC value of the coded signal depends on the data to be transmitted.
Thus, DC-free coding addresses the capacitive nature of the CMUT transducer, as any additional
DC signal may be added to the bias voltage applied to the CMUT, resulting in an undesirable
change in its operating frequency. In this implementation, the encoded signal can not be applied
directly to the CMUT device 60. Since the CMUT 60 requires a large voltage excitation to
generate a sufficiently large acoustic signal, the encoded signal needs to be amplified first. In the
configured embodiment, the 200 mV (peak to peak) signal generated by the transmitter 62 is
amplified by a 50 dB high frequency amplifier (drive circuit). Furthermore, in order to operate
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the CMUT device in the preferred collapse mode, a bias voltage also needs to be applied.
Communication can also occur when the CMUT device does not operate in the collapse mode, ie,
in the non-collapse mode or in the stop mode. However, the resonant frequency in the noncollapsing mode is generally lower than that in the collapsing mode, and the low generated
acoustic power can interfere with the effective operation of the communication link over the
desired distance through the body. In the configured embodiment, a bias voltage of about 100 V
is provided to the CMUT device to bias and operate in the collapse mode. A bias T circuit was
implemented to simultaneously provide the bias voltage and the AC drive voltage from the
transceiver drive circuit to the CMUT device 60. Finally, the impedance matching output
impedance, bias, and drive circuit / amplifier block 66 need to be properly selected to enable the
desired operation of the CMUT 60.
[0011]
On the receiving side shown in FIG. 3, the CMUT device 60 converts the received acoustic signal
into an electrical signal. Similar to the transmit side, an impedance matching circuit and a bias
voltage 72 are applied to the receiving CMUT device 60. In the configured embodiment, a bias T
circuit applied a bias voltage of about 100 V to the CMUT device to set its sensitivity to the
desired frequency range. The ultrasound waves acquired by the CMUT device 60 are thus
converted into electrical signals. Because this signal is typically tens of mV peak-to-peak and
small, low noise amplifier (LNA) 74 first amplifies this signal before being decoded. Impedance
matching is performed by selecting an LNA with a suitably large input impedance. The amplified
signal is then provided to a receiver 70 which in this embodiment comprises the following
elements: Clock recovery circuit 78 and data correlation circuit 80 are coupled to receive the
received communication signal and are responsive to timing generator 76. The detailed operation
of this circuit is described in FIG. 10 below. The output of the data correlation circuit is then
provided to the decoder 82, and the received data is then passed to a utilization device, such as a
processor (not shown).
[0012]
Referring to FIG. 4, a typical non-collapsing CMUT transducer cell 10 is shown in cross section.
The CMUT transducer cell 10 is fabricated with a plurality of similar adjacent cells on a substrate
12 such as silicon. The diaphragm or membrane 14 which may be made of silicon nitride is
supported above the substrate by an insulating support 16 which may be made of silicon oxide
or silicon nitride. The cavity 18 between the membrane and the substrate can be filled with air or
gas, or be totally or partially evacuated. A conductive film or layer 20 such as gold forms an
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6
electrode on the diaphragm, and a similar film or layer 22 forms an electrode on the substrate.
These two electrodes separated by the dielectric cavity 18 form a capacitance. When the acoustic
signal causes the membrane 14 to vibrate, variations in capacitance can be detected, thereby
converting the acoustic wave into a corresponding electrical signal. Conversely, an AC signal
applied to the electrodes 20, 22 modulates the capacitance to move the membrane, thereby
causing the acoustic signal to be transmitted.
[0013]
FIG. 5 is an electrical schematic of the operation of CMUT 10 of FIG. A DC bias voltage VB is
applied to the bias terminal 24 and coupled to the membrane electrode 20 by a path that exhibits
a high impedance Z to AC signals, such as inductive impedance. The AC signal is capacitively
coupled from the signal terminal 26 to the membrane electrode. The positive charge on the
membrane 14 causes the membrane to swell as it is attracted to the negative charge on the
substrate 12. The CMUT was found to be most sensitive when the membrane was inflated such
that the two oppositely charged plates of the capacitive device were as close together as possible.
Bringing the two plates closer results in a greater coupling between the acoustic signal energy
and the electrical signal energy by the CMUT. Therefore, it is desirable to increase the bias
voltage VB until the dielectric spacing 32 between the membrane 14 and the substrate 12 is
small enough to be maintained under the conditions of the operating signal. In configured
embodiments, this spacing was generally on the order of 1 micron or less.
[0014]
Referring to FIG. 6, a schematic cross-section of a CMUT element 5 suitable for operating in the
collapse mode is shown. The CMUT element 5 includes a substrate layer 12, an electrode 22, a
membrane layer 14, and a membrane electrode ring 28. In this example, the electrodes 22 are
configured circular and embedded in the substrate layer 12. Further, the membrane layer 14 is
fixed to the top surface of the substrate layer 12 and is configured / dimensioned to define a
spherical or cylindrical cavity 18 between the membrane layer 14 and the substrate layer 12.
The cell and its cavity 18 can also define alternative geometries. For example, the cavity 18 may
also define a rectangular and / or square cross section, a hexagonal cross section, an elliptical
cross section, or an irregular cross section.
[0015]
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7
The bottom electrode 22 is usually insulated on the side facing the cavity using a further layer
(not shown). A preferred insulating layer is an ONO (Oxide-Nitride-Oxide) dielectric layer formed
on the substrate electrode and below the membrane electrode. The ONO dielectric layer is
advantageous as it reduces device instability and charge build up on the electrode that causes the
acoustic output pressure to drift and drop. The fabrication of the ONO dielectric layer on CMUT
is discussed in detail in European Patent Application No. 08305553.3 by Klootwijk et al., Entitled
"Capacitive micromachined ultrasound transducer," filed September 16, 2008. The use of an ONO
dielectric layer is desirable when using a CMUT in the collapse mode, which is more capable of
charge retention than non-collapse devices. The disclosed components are fabricated from
materials compatible with CMOS, such as, for example, Al, Ti, nitrides (eg, silicon nitride), oxides
(various grades), tetraethyl orthosilicate (TEOS), polysilicon, etc. can do. In CMOS fabs, for
example, oxide and nitride layers can be formed by chemical vapor deposition, and metallization
(electrode) layers are produced by a sputtering process. Suitable CMOS processes are LPCVD and
PECVD, the latter having relatively low operating temperatures below 400.degree.
[0016]
An exemplary technique for creating the disclosed cavity 18 includes defining the cavity in the
first portion of the membrane layer 14 prior to applying the top surface of the membrane layer
14. Other fabrication details can be found in US Pat. No. 6,328,697 (Fraser). In the exemplary
embodiment shown in FIG. 6, the diameter of the cylindrical cavity 18 is larger than the diameter
of the circularly configured electrode plate 22. The electrode ring 28 can also have the same
outer diameter as the circularly configured electrode plate 22, but such a match is not necessary.
Thus, in the exemplary embodiment of the present invention, the electrode ring 28 is fixed
relative to the top surface of the membrane layer 14 so as to be aligned with the underlying
electrode plate 22.
[0017]
FIG. 7 shows the CMUT cell of FIG. 6 when the membrane 14 is biased into the pre-collapsed
state in contact with the floor of the cavity 18. This is accomplished by applying a DC bias
voltage to the two electrodes, as indicated by the voltage V B applied to the electrode ring 28 and
the reference potential (ground) applied to the substrate electrode 22. The electrode ring 28 can
also be formed as a continuous disc without a hole in the center, but FIG. 7 shows why this is not
necessary. As shown in this figure, when the membrane 14 is biased into its pre-collapsed state,
the center of the membrane is in contact with the floor of the cavity 18. Thus, the center of
04-05-2019
8
membrane 14 does not move during operation of the CMUT. Instead, it is the peripheral area of
the membrane 14 that is over the remaining open cavity of the cavity 18 and under the disc or
ring electrode that moves. By forming the membrane electrode 28 as a ring, the charge on the
upper plate of the device's capacitance is located over the area of the CMUT that exhibits motion
and capacitive variations when the CMUT is operating as a transducer. Thus, the coupling factor
of the CMUT transducer is improved. In the collapse mode, the resonant frequency of the CMUT
cell increases with the increase of the bias voltage provided by the bias circuit.
[0018]
Membrane 14 can be brought into its pre-collapsed state in contact with the floor of cavity 18, as
shown at 36, by applying the necessary bias voltage, which is typically in the range of 50-100
volts. . As the voltage is increased, the capacitance of the CMUT cell is monitored with a
capacitance meter. A sudden change in capacitance indicates that the membrane has collapsed to
the floor of the cavity. The membrane can be biased downward until it just touches the floor of
the cavity, as shown at 36, or biased further downward to an increased collapse state beyond
minimal contact It can be done. An advantage of the collapse mode of operation is that the
operating frequency of the CMUT cell (transducer) can be varied with the bias voltage.
[0019]
FIG. 8 illustrates another technique for biasing the membrane 14 to the pre-collapsed state,
which is due to the retention member 40. The membrane 14 is electrically biased to its precollapsed state, as shown in FIG. 7, but a retaining member 40 physically maintains the
membrane in its pre-collapsed state over the membrane. Arranged or formed. In a preferred
embodiment for an ultrasound transducer to perform imaging, the structure forms a lens of the
transducer. Transducer lenses typically meet three requirements. One is to provide a structure in
which the lens resists abrasion resistance due to frictional contact created during use of the
transducer probe. In practice, the lens provides a physical cover that protects the underlying
transducer array comprising the ultrasound transducers from physical wear. Second, the lens is
non-conductive, thereby providing electrical isolation between the electrical elements of the
transducer and the patient. This is an important characteristic for human body communication
devices such as the device of the present invention. Third, the lens is able to provide focus
characteristics for the probe. In the example of FIG. 8, the retaining member 40 provides a fourth
benefit of physically retaining the membrane 14 in its pre-collapsed state.
04-05-2019
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[0020]
Various materials can be used for the holding member. The only requirement for the CMUT is
that the material be of sufficient rigidity to keep the membrane in its collapsed state after the
bias voltage is removed. One suitable material is polydimethylsiloxane (PDMS or RTV rubber).
The RTV material is cast over the CMUT while the bias voltage V B holds the membrane in its
desired collapsed state. After the RTV has been polymerized and rigid enough to physically
maintain the membrane in its pre-collapsed state, the bias voltage can be removed, which biases
the device for operation. It does not need to be applied again until it is applied. Preferably, the
retaining members are adhered to the area around each membrane of the CMUT array. Other
materials that may be suitable for the retaining member 40 include urethane rubbers, vinyl
plastisols, and thermoplastic elastomers.
[0021]
By physically holding the membrane in its pre-collapsed state, no bias is required to maintain the
pre-collapsed state until an operational bias is applied during use of the device. This means that
the CMUT can operate at low voltage, which is advantageous for miniaturized devices such as
human body communication devices. Furthermore, adverse effects due to variability in
manufacturing and material properties such as variations in membrane dimensions, stiffness or
cavity depth between lots can be eliminated. These variability means that more or less bias
voltage is required to bring the CMUT into its pre-collapsed state. The bias voltage is adjusted
according to the degree of collapse desired, and then the holding member holds the membrane in
this state. Thus, each CMUT array can be set to the same performance characteristic or its
coupling customized, even in the presence of these tolerance variations. Greater uniformity of the
probe can be achieved with respect to properties such as operating voltage range, acoustic
impedance, capacitance, and coupling factor.
[0022]
FIG. 9 is a plot of a typical wide band performance of a CMUT transducer in collapse mode, such
as those shown in FIGS. 7 and 8. For an added or received impulse 92, a typical collapse mode
CMUT transducer will exhibit the frequency response shown by curve 90. As the 3 dB point on
this curve shows, for frequencies in the 4 to 8 MHz range, the bandwidth of CMUT transducers in
collapse mode approaches or exceeds 100%, making it ideal for broadband communication
systems It is a thing.
04-05-2019
10
[0023]
FIG. 10 shows a transceiver system for the intracorporeal ultrasound communication system of
the present invention. TX bits transmitted in other digital bit streams according to the selected
spreading code and according to the requirement that the transmitter subsystem TX of the
transceiver has at least one signal transmission for each transmission bit (transmission period)
The encoder or encoding circuit (C) 120 that encodes the bit stream BS of This bit stream is then
coupled to the body via digital buffer 110, which can also raise the signal to the level required by
the subsequent CMUT drive circuit. If desired, digital buffer 110 can also provide bandwidth
limitation.
[0024]
In the receiver subsystem, an input amplifier (e.g., a low noise amplifier (LNA)) 214 is DC
decoupled to the CMUT electrodes 22, 28. The amplified signal of the CMUT (or CMUTs) is then
sent to two correlator circuits used for data detection and synchronization. In the example
shown, both correlators are connected to each data or input signal at the synchronization
multipliers 216, 218 and to a digital template (e.g. a 1 bit template "synchronization template" as
a synchronization pattern for synchronization). And as a reference signal for data detection,
implemented by analog multiplication of a 1-bit template ("data template"). If the synchronization
template is "1", then the amplified signal is multiplied by "1" (ie, by a positive constant
multiplication factor) by the synchronization multiplier 218. If the synchronization template is
'0', the amplified signal is multiplied by '-1' (ie, by a negative constant multiplication factor) by
the synchronization multiplier 218. The result of the multiplication is then integrated in each
data or synchronization integrator 220, 222 over the reception period (eg, chip period) to
actually calculate each data or synchronization correlation. The integral output corresponds to
the desired data and synchronization information.
[0025]
The correlation between the synchronization template and the input signal is made by the
sampling and pulse amplitude modulation (PAM) circuit (S / PAM) 224 in order to close the chip
level synchronization loop indicated by the dashed box. It is sampled at the end. The integrated
output of the correlator is a measure of the difference between the input signal frequency and
04-05-2019
11
the local template. The smaller the output (the better the correlation), the less the
synchronization error. After the error goes below the sensitivity threshold, reception is
considered synchronized and a second data correlation starts. The sampled PAM values may then
be further multiplied by a further multiplier 246 by "+1" or "-1" according to the polarity of the
detected data ("chip") to ensure correct polarity according to the input data. Can. During the
synchronization sequence, polarity selection can be performed by use of a fixed synchronization
pattern that conforms to the synchronization sequence generated by the transmitter subsystem.
Thus, the further multiplier 246 acts as a polarity control element to control the polarity of the
output value of the second correlator according to the polarity of the detected data (ie the
decoded signal). The signal from multiplier 246 is filtered by loop filter 234 and sent to voltage
control oscillator (VCO) 236, which generates a control and template signal by digital controller
238. An internal clock (int.clock) used as a time base or time reference is generated based on its
input. The filtering of the synchronization information is thus implemented by generating a pulse
(PAM signal) that is proportional to the sampled signal that is then filtered by the loop filter 234.
[0026]
In the data detection branch, the correlation in the data correlator is performed at the chip level
and is first converted to a digital bit stream ("chip") by using the comparator or threshold circuit
226 and sent to the digital correlator 232 Digital correlator 232 performs symbol level
synchronization and provides the correct synchronized code sequence ("spreading code") for
template generation by digital controller 238. The analog output of the chip level correlator can
be further integrated over the symbol length by the analog accumulator 228 if, for reliability
reasons, also analog correlation at the symbol level is required, and the digital correlator 232 By
generating the correlator reset signal and supplying it to the analog accumulator 228, the
accumulation time over the symbols can be controlled. The symbol level correlation is then
converted to digital by using a comparator or threshold circuit 230 to provide the desired bit
stream RX bits. If reliability is not an issue, analog accumulators can be eliminated and digital
correlators can be used for symbol level correlation.
[0027]
As a further option, it is also possible to use the comparison between the output bit stream RX
bits from the analog symbol level correlator and the expected bit stream generated by the digital
correlator as a measure of the quality of the input signal. , It can also be presented as a chip error
rate signal CER (Chip-Error-Rate).
[0028]
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12
The transceiver of FIG. 10 also includes an ultra-low power wakeup detector that can sense the
channel in idle mode.
This makes it possible to switch off the main receiver block that consumes power. When
communication is detected on the channel, the main receiver block is switched on to start
receiving data. The wakeup detector consists of a (low noise) amplifier input stage 250 followed
by a narrow band pass filter 252 set in the communication band, an energy storage 254 and a
comparator or threshold circuit 256. When the wakeup detector detects the received signal, it
operates the transceiver and uses the wakeup interrupt coupled to a processor ("CONTROL") to
process the information it generates, the main receiver Activate.
[0029]
It is worthwhile to note that several additions can be made to this structure. As an example, a
phase rotation detector can be added that applies 1-bit analog-to-digital conversion to the chiplevel analog correlator output (for the data branch and for the synchronization branch). The
obtained 2-bit information can be used to detect the sign of the frequency difference between the
receiver and the transmitter by monitoring its evolution over time. This information can be used
to increase the synchronization range of the synchronization system, thus enabling
synchronization even in the absence of an accurate time reference, such as a crystal oscillator or
the like. .
[0030]
The intracorporeal ultrasound communication device of the present invention can exhibit the
following advantages: 1) The ultrasound communication link of the present invention uses a
broadband transducer (such as CMUT) in combination with a broadband transceiver architecture
Thus, high data throughput can be achieved. 2) A small transmitting and receiving element can
be used. If a MEMS device such as a CMUT is used, the CMUT transceiver elements can be
integrated on the same die as the microelectronic transceiver circuit. Thus, a form factor of
several square millimeters can be achieved. 3) Weak acoustic scattering in soft tissue enables
robust signal propagation that can be used for data communication. As with water, ultrasound
propagates through the body much better than high frequency or electromagnetic waves. Thus,
the communication link of the present invention can achieve a data transfer rate of Mb / sec with
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13
very low energy consumption and low energy induction in the body. 4) The ultrasound
intracorporeal communication device of the present invention avoids interference with electrical
medical systems (eg magnetic resonance imaging, pacemakers etc) and its high immunity to
acoustic noise and interference (eg imaging Provide robustness in the presence of other medical
devices used simultaneously. Mitigation of interference within or close to the operating
frequency band is generally not required. 5) Implementations of the invention provide high
immunity to noise and interference, thus enabling communication at very low signal levels. The
ultrasound can be transmitted in a specific direction towards the receiver. In that case, the
ultrasound intracorporeal communication device comprises several CMUT transducers in an
array. The aperture can be designed to produce an acoustic beam, with a specific width and angle
(similar to ultrasound imaging). This can be used to transmit data towards a particular receiver
(out of a few). Additionally, the receiver can be tuned to listen to a particular or multiple
transmitters. Another option is to transmit / receive ultrasound at multiple angles. This enhances
energy efficiency and the robustness of the communication link. 6) Compared to prior art
devices, the implementation of the present invention enables communication between two or
more intracorporeal communication devices, and further bi-directional communication between
two ultrasound transducers of such devices Make it possible.
7) Energy consumption is minimized by using wake up circuitry for the receiver.
[0031]
The above-described, configured embodiments show that intracorporeal ultrasound
communication is possible over a distance of at least 30 cm.
[0032]
The intracorporeal communication device according to the invention can in particular be used in
the following applications:
[0033]
A.
Pacemaker An ultrasound transceiver that typically uses a CMUT device connected to a
broadband communication transceiver, such as that shown in FIG. 10, can be implemented at the
pacemaker.
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Thus, several features can be enabled, such as configuring a pacemaker after being implanted in
a patient. Another function is to allow the pacemaker to provide information regarding its
current status (eg, the status of its internal battery, and the pulse rate delivered). Thus, an easy
way to verify correct operation of the pacemaker is provided.
[0034]
Furthermore, as mentioned earlier, the communication link between the ultrasound transmitter /
receiver integrated into the pacemaker and the ultrasound transmitter / receiver on the external
surface of the body can be used for other electrical medical systems (eg magnetic resonance) It is
not affected by the interference from the imaging system etc.). Thus, robust communication links
can also be achieved in a hospital environment.
[0035]
Pacemaker implemented ultrasound communication devices can be designed to operate at low
bias voltages. Lithium ion batteries are usually used in implants such as pacemakers. Batteries of
this type typically provide a supply voltage in the range of 1 to 5 volts. Therefore, the CMUT
device integrated into the implant needs to be able to operate correctly at such low AC voltage, ie
it has sufficient acoustic energy at the appropriate frequency bandwidth (ie the frequency
bandwidth of the transceiver) Need to be able to generate These characteristics (frequency
bandwidth, bias voltage, etc.) can be set when designing a CMUT device as described in
International Patent Publication WO 2010097729 A1. Alternatively, local boosting of bias
voltage up to several tens of volts can be realized electronically with a voltage booster.
[0036]
An embodiment of the pacemaker is comprised of an ultrasound intracorporeal communication
system, the ultrasound intracorporeal communication system comprising a pacemaker implanted
in the body and an ultrasound intracorporeal communication device incorporated in the
pacemaker, It is also coupled to an ultrasound transducer that transmits or receives encoded data
with ultrasound passing through the body, a transducer drive circuit and amplifier coupled to the
ultrasound transducer, a transducer drive circuit, an amplifier, and a pacemaker. And an
ultrasound trans-corporeal communication device that transmits and receives data through the
body surrounding the pacemaker.
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[0037]
In this embodiment, the ultrasound transducer can further include a CMUT transducer.
The ultrasound intracorporeal communication system further comprises a battery that provides a
voltage in the range of 1 to 5 volts to power the ultrasound intracorporeal communication
device. Further, the data further includes one of pacemaker configuration data or battery status
data.
[0038]
B. Intravascular catheters Another application of the device according to the invention is in the
field of intraluminal ultrasound imaging, in particular in the field of intravascular ultrasound
(IVUS), in which case a catheter with a miniaturized ultrasound transducer array Are used to
image the inner wall of the blood vessel. The ultrasound imaging system comprises an array of
ultrasound transducers coupled to an integrated circuit to enable ultrasound beam forming
functionality. IVUS catheters are commonly used in stenting procedures. IVUS catheters need to
be as thin as possible so that they can reach narrow veins, and thinner catheters create a wider
range of applications and treatments.
[0039]
In IVUS catheters, imaging data acquired by an ultrasound transducer is electronically
transported by means of wires through the catheter to an imaging system where the imaging
data is processed and displayed. The more elements the transducer has, the better the ultrasound
image. Because the data of any ultrasound element needs to be processed and sent through the
catheter, the amount of wire passing through the catheter and the amount of data multiplexing at
the catheter tip before sending the data through the catheter A compromise between is made.
However, multiplexing in the catheter is limited by heat generation and size limitations. Using
ultrasound communication links to transmit imaging data to a receiver external to the body
provides an attractive way to limit the amount of wire in the catheter while still providing good
image quality . Ultrasound imaging is generally performed in the ultrasound frequency range
from 1 MHz up to 40 MHz. Thus, the present invention enables the communication device to be
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implemented in an ultrasound imaging system, enabling the same arrayed CMUT elements used
for ultrasound imaging to also be used as data communication transducers. In this embodiment,
imaging and communication may be performed in a time interleaved manner. Other
implementations include using several elements simultaneously for imaging and others for
communication, and using different frequencies for imaging and communication. An advantage
of such an ultrasound system is that the present invention uses ultrasound to enable the dual
CMUT element functionality of ultrasound imaging and wireless data exchange. The operating (or
resonant) frequency of the element can be adjusted by the applied bias voltage to expand the
bandwidth and sensitivity of the transducer.
[0040]
An embodiment of the intravascular catheter comprises an ultrasound intracorporeal
communication system, the ultrasound intracorporeal communication system comprising a
catheter guided into the body by the body's vasculature, and an ultrasound intracorporeal
communication device incorporated within the catheter. A CMUT transducer that transmits or
receives encoded data with ultrasound passing through the body, a transducer drive circuit
coupled to the ultrasound transducer, a transmitter coupled to the transducer drive circuit and
the catheter, and The ultrasound intracorporeal communication device transmits data through
the body surrounding the catheter.
[0041]
In yet another embodiment, the catheter further comprises an ultrasound imaging transducer,
and the ultrasound transducer of the ultrasound intracorporeal communication device further
comprises an ultrasound imaging transducer of the catheter.
[0042]
Additionally, the data can further include ultrasound image data acquired by an ultrasound
imaging transducer of a catheter.
[0043]
C.
Intervention treatment Another use of the device of the invention is to extract biomaterials (e.g.
biopsy procedures), to administer medical substances such as anesthesia or drug delivery, or to
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perform thermal ablation. In an interventional procedure using a device that is temporarily
inserted into the
These devices should be extremely small (eg, needles) and require very high positioning accuracy
so that substances can be extracted and administered from very small target sites in the body.
These processes can be facilitated by techniques that determine the position of the needle tip or
ablation device within the body and the nature of the immediate environment, such as its
temperature or tissue density. Furthermore, these devices can benefit from control signals that
can adjust their functions. Because the needle may be too small to incorporate a cable, these
systems can benefit from wireless communication suitable for internal operation, such as that
provided by the ultrasound communication device of the present invention. Because ultrasound
communication using CMUTs can be realized with very small form factors, such communication
devices can be integrated into needles or other devices that are temporarily inserted into the
body. Communication can be used as location beacons, setup transport, or to transmit local
parameters of the environment.
[0044]
The interventional embodiment includes an ultrasound intracorporeal communication system,
the ultrasound intracorporeal communication system comprising an interventional device guided
into the body, an ultrasound intracorporeal communication device incorporated in the
interventional device, and passing through the body An ultrasound transducer for transmitting
encoded data with ultrasound, a transducer drive circuit coupled to the ultrasound transducer,
and a transmitter coupled to the ultrasound drive circuit and the interventional device; A transit
communication device transmits and receives data through the body surrounding the
interventional device.
[0045]
In this embodiment, the interventional device can further include a biopsy needle and / or an
ablation device, and the ultrasound transducer can further include a CMUT transducer.
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