U.S. patent application number 13/681638 was filed with the patent office on 2013-03-28 for time-reversed mirroring electro-magnetic acoustic treatment system.
This patent application is currently assigned to MAGNETUS, LLC. The applicant listed for this patent is Magnetus, LLC. Invention is credited to Stephen Anthony Cerwin, David B. Chang, Jane F. Emerson.
Application Number | 20130079685 13/681638 |
Document ID | / |
Family ID | 44973056 |
Filed Date | 2013-03-28 |
United States Patent
Application |
20130079685 |
Kind Code |
A1 |
Cerwin; Stephen Anthony ; et
al. |
March 28, 2013 |
Time-Reversed Mirroring Electro-Magnetic Acoustic Treatment
System
Abstract
A time-reversal mirroring electromagnetic acoustic treatment
system is disclosed where electro-magnetic signals are directed to
a region of interest in or on a patient. The EM signals induce an
internally sourced acoustic signal due to variations in
conductivity of the target tissue. Acoustic data representative of
the induced acoustic signal are collected and analyzed to develop a
model of a measured conductivity topology representing the
conductivity topology of the target tissue. Measured parameters
associated with the measured conductivity topology and derived from
the acoustic data can be used to generate a time-reversed mirror
acoustic treatment signal that can be used to apply a therapeutic
treatment to a target tissue within the region of interest.
Inventors: |
Cerwin; Stephen Anthony;
(Mico, TX) ; Chang; David B.; (Tustin, CA)
; Emerson; Jane F.; (Irvine, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Magnetus, LLC; |
Irvine |
CA |
US |
|
|
Assignee: |
MAGNETUS, LLC
Irvine
CA
|
Family ID: |
44973056 |
Appl. No.: |
13/681638 |
Filed: |
November 20, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12786232 |
May 24, 2010 |
8337433 |
|
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13681638 |
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Current U.S.
Class: |
601/15 |
Current CPC
Class: |
A61N 2007/0078 20130101;
A61N 2007/0073 20130101; A61N 2007/0052 20130101; A61B 8/13
20130101; A61N 2007/0095 20130101; A61B 8/00 20130101; A61N 7/00
20130101 |
Class at
Publication: |
601/15 |
International
Class: |
A61B 8/00 20060101
A61B008/00 |
Claims
1. A time-reversal mirroring electromagnetic acoustic treatment
system, the system, comprising: an electromagnetic signal source
configured to emit electromagnetic radiation toward a subject
tissue area having a conductivity gradient; an array of acoustic
transducers configured to collect acoustic signals generated in
response to the electromagnetic radiation inducing an induced
acoustic signal from the subject tissue area; a TRM controller
communicatively coupled to the array of acoustic transducers and
that (a) collects acoustic data representative of the induced
acoustic signal received by the array of acoustic transducers, (b)
derives a measured electromagnetic topology of the subject tissue
area based on input properties of the electromagnetic radiation
emitted from the electromagnetic signal source and resulting output
properties of the acoustic data, and (c) generates emitter
instructions for a time-reversed acoustic signal from the acoustic
data as a function of the measured electromagnetic topology, the
time-reversed acoustic signal targeting a target tissue within the
subject tissue area; and an array of acoustic emitters coupled to
the TRM controller and configured to emit the time-reversed
acoustic signal according to the emitter instructions toward the
target tissue.
2. The system of claim 1, wherein the target tissue lacks a
substantial contribution to the measured electromagnetic
topology.
3. The system of claim 1, wherein the time-reversed acoustic signal
comprises sufficient gain to ablate a portion of the target
tissue.
4. The system of claim 1, wherein the TRM controller is configured
to generate the emitter instructions representative of the
time-reversed acoustic signal for the target tissue as a function
of measured parameters of the subject tissue area.
5. The system of claim 4, wherein the TRM controller is further
configured to measure the subject tissue area measured parameters
based on the acoustic data.
6. The system of claim 5, wherein the subject tissue area measured
parameters comprises a signal-to-noise ratio measured from the
acoustic data.
7. The system of claim 6, wherein the TRM controller is configured
to identify the target tissue based on a threshold of the
signal-to-noise ratio.
8. The system of claim 4, wherein the TRM controller is configured
to measure the subject tissue area measured parameters based on
reflections of emitted electromagnetic signals from the subject
tissue area.
9. The system of claim 4, wherein the subject tissue area measured
parameters are derived from at least one of the following: a sum of
input transmitted RF frequencies, frequency chirp, and a difference
of input transmitted RF frequencies.
10. The system of claim 1, further comprising a dual-mode imaging
apparatus capable of simultaneously displaying an acoustic image
derived from the acoustic data and an electromagnetic image derived
from reflections of the emitted electromagnetic signals from the
subject tissue area.
11. The system of claim 1, wherein the electromagnetic signal
source comprises a magnetic resonance imaging system.
12. The system of claim 1, wherein the TRM controller if further
configured to apply an ablative therapy to the target tissue in
response to feedback received via the array of acoustic
transducers.
13. The system of claim 1, wherein the induced acoustic signal
comprises an induced ultrasound signal.
14. The system of claim 1, wherein the electromagnetic radiation
comprises at least two EM signals having distinct frequency
peaks.
15. The system of claim 1, wherein the measured electromagnetic
topology comprises at least a three dimensional volume.
16. The system of claim 1, wherein the time-reversed acoustic
signal comprises conductivity weighted treatment signal directed
toward the target tissue.
17. A time-reversal mirroring electromagnetic acoustic treatment
system, the system, comprising: an electromagnetic signal source
configured to emit electromagnetic radiation toward a subject
tissue area having a conductivity gradient; an array of acoustic
transducers configured to collect acoustic signals generated in
response to the electromagnetic radiation inducing an induced
acoustic signal from the subject tissue area; a TRM passive
controller communicatively coupled to the array of acoustic
transducers and that (a) collects acoustic data representative of
the induced acoustic signal received by the array of acoustic
transducers from a electromagnetic topology of the subject tissue
area, and (b) generates emitter instructions for a time-reversed
acoustic signal from the acoustic data based on the electromagnetic
topology, the time-reversed acoustic signal targeting a target
tissue within the subject tissue area; and an array of acoustic
emitters coupled to the TRM controller and configured to emit the
time-reversed acoustic signal according to the emitter instructions
toward the target tissue.
Description
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/786,232 filed on May 24, 2010. This and all other
extrinsic materials discussed herein are incorporated by reference
in their entirety. Where a definition or use of a term in an
incorporated reference is inconsistent or contrary to the
definition of that term provided herein, the definition of that
term provided herein applies and the definition of that term in the
reference does not apply.
FIELD OF THE INVENTION
[0002] The field of the invention is acoustic imaging
technologies.
BACKGROUND
[0003] Electro-Magnetic Acoustic Imaging (EMAI) technologies have
developed significantly over the last several decades; in a large
part to the Applicants' own seminal works. For example, EMAI
technologies are described in great detail in co-owned U.S. Pat.
No. 6,535,625 to Chang et al. titled "Magneto-Acoustic Imagining"
filed on Sep. 24, 1999 and co-owned U.S. Pat. No. 6,974,415 to
Cerwin et al. titled "Electromagnetic-Acoustic Imagining" filed on
May 22, 2003.
[0004] It was appreciated early on that one could use Time-Reversed
Mirroring (TRM) of ultrasonic signals to treat target tissues. For
example, the papers titled "Time Reversal of Ultrasonic
Fields--Part I: Basic Principles" and "Time Reversal of Ultrasonic
Fields--Part II: Experimental Results" by Fink et al., published in
September 1992, describe in great detail time reversing ultrasonic
acoustic signals. Further effort toward developing TRM ultrasound
technologies is described in U.S. Pat. No. 5,428,999 to Fink titled
"Method and Apparatus for Acoustic Examination Using Time Reversal"
filed on Sep. 24, 1993, and U.S. Pat. No. 6,755,083 to Berryman
titled "Method for Distinguishing Multiple Targets Using
Time-Reversal Acoustics" filed Apr. 22, 2002.
[0005] The Applicants also provided pioneering insight into
combining the two technologies where electro-magnetically induced
acoustic ultrasounds could be time-reversed and mirrored back
toward an originating internal target tissue as described in U.S.
patent application publication U.S. 2007/0038060 to Cerwin et al.
titled "Identifying and Treating Bodily Tissues Using
Electromagnetically Induced, Time-Reversed, Acoustic Signals" filed
on Jun. 9, 2006. At the time, the Applicants focused on applying an
amplified TRM ultrasound signal back toward a detected conductivity
gradient, possibly to ablate a target tissue.
[0006] These and all other extrinsic materials discussed herein are
incorporated by reference in their entirety. Where a definition or
use of a term in an incorporated reference is inconsistent or
contrary to the definition of that term provided herein, the
definition of that term provided herein applies and the definition
of that term in the reference does not apply.
[0007] The Applicants have come to further appreciate that a wealth
of information is available regarding a subject area of interest
that can be brought to bear when constructing a TRM ultrasound
signal to target a specific tissue. Previously, induced ultrasound
signals were filtered to enhance reception of only signals having a
frequency twice the frequency of an input RF signal. Additionally,
the received ultrasound signals were only mirrored back toward a
conductivity gradient. Applicants have now appreciated received
acoustic data of an induced acoustic signal represents a
measurement of a conductive topology, as opposed to just an
indicator that a conductivity gradient is present. The acoustic
data reflects properties of a full conductivity topology and by
extension properties of the tissues within the subject area under
consideration. One can collect and use the acoustic data to derive
parameters associated with the conductivity topology to deduce or
derive various properties of the subject tissue area. The measured
parameters can then be used to tailor a TRM acoustic treatment
signal to apply therapy to a target tissue within the subject area.
One should appreciate that conductivity topologies can be combined
with other topologies (e.g., mechanical, acoustic, density, etc.)
to create a hybrid topology that can be brought to bear for
clinically useful results (e.g., diagnosis, treatment, etc.)
[0008] Unless the context dictates the contrary, all ranges set
forth herein should be interpreted as being inclusive of their
endpoints, and open-ended ranges should be interpreted to include
commercially practical values. Similarly, all lists of values
should be considered as inclusive of intermediate values unless the
context indicates the contrary.
[0009] Thus, there is still a need for time-reversed mirroring of
electro-magnetically induced acoustic signals.
SUMMARY OF THE INVENTION
[0010] The inventive subject matter provides apparatus, systems and
methods in which one can utilize a system for identifying a target
tissue for therapy based on detected properties of a conductivity
topology of a subject tissue area. One aspect of the inventive
subject includes a Time-Reversed Mirroring (TRM) Electro-Magnetic
Acoustic (EMA) treatment system. Contemplated systems comprise an
Electro-Magnetic (EM) signal source configured to emit EM
radiation, preferably in the radio frequency range, toward a
subject area having one or more tissues. Tissues in a subject area
typically have different mechanical, chemical, or electrical
proprieties. Due to variations in such properties, the tissues can
exhibit a conductivity gradient that reacts in response to being
bathed by the EM radiation. The reaction can be generating induced
acoustic signals, typically UltraSound (US). TRM EMA treatment
systems can also include an array of acoustics transducers
configured to receive the induced acoustic signals generated from
within the subject area. The transducer array can provide to a TRM
controller acoustic data representative of the received induced
acoustic signal. Preferably the TRM controller collects and
analyzes the acoustic data from the transducer array. Through
analysis of the acoustic data, the TRM controller can derive a
measured conductivity topology of at least a portion of the subject
area based on the properties of the acoustic data (e.g., frequency,
signal strength, noise level, signal-to-noise ratio, phase, time of
flight, etc.). The TRM controller can also generate a set of
instructions for acoustic emitters. The instructions represent
control signals to the array of acoustic emitters, preferably the
array of transducers, to emit a time reversed acoustic signal back
toward the subject area, preferably directed to a target tissue
selected based on the measured parameters as determined from the
measured conductivity topology.
[0011] One should appreciate that the time reversed acoustic
signals can be controlled through the TRM controller. In some
embodiments, the time reversed acoustic signal represents a time
reversed mirrored version of the received electromagnetically
induced acoustic signal. The time reversed acoustic signal can also
be constructed based one or more properties of the measured
conductivity topology as derived from the received acoustic data.
Constructing the time reversed acoustic signal provides for
tailoring a specific acoustic treatment or targeting specific
tissues exhibiting interesting properties. The properties of the
measured conductivity topology can include geometry,
signal-to-noise ratio, conductivity, location, or other parameters
measured from the acoustic data. It is also contemplated that the
time reversed acoustic signal can be constructed based on other
information as well, possibly including EM reflections, mechanical
properties, input from a healthcare provider, programmatic data, or
other information. Furthermore, the time reversed acoustic signal
can be constructed so that it targets a specific tissue within the
subject area based on the target tissue's contribution to the
conductivity topology or even if it lacks a substantial
contribution to the measured topology. As an example, the
contemplated system can construct the time reversed acoustic
signal, possibly a conductivity weighted treatment signal, so that
it has sufficient gain to ablate at least a portion of a target
tissue.
[0012] Various objects, features, aspects and advantages of the
inventive subject matter will become more apparent from the
following detailed description of preferred embodiments, along with
the accompanying drawing figures in which like numerals represent
like components.
BRIEF DESCRIPTION OF THE DRAWING
[0013] FIG. 1 is an overview of a time-reversal mirroring
electro-magnetic acoustic treatment system.
[0014] FIG. 2 is a schematic of a possible time-reversal mirroring
controller.
[0015] FIG. 3A illustrates targeting a tissue based on a measured
conductivity topology of a target tissue.
[0016] FIG. 3B illustrates targeting a tissue based on a measured
conductivity topology where a target tissue lacks a significant
contribution to the measured conductivity topology.
[0017] FIG. 4A presents an example pair of transmitted input RF
signals.
[0018] FIG. 4B presents received acoustic signals from the pair RF
signal of FIG. 4A.
DETAILED DESCRIPTION
[0019] Throughout the following discussion, numerous references
will be made regarding sources, controllers, apparatus, systems, or
other forms of computing devices. It should be appreciated that the
use of such terms is deemed to represent one or more computing
devices having at least one processor configured to execute
software instructions stored on a computer readable medium. For
example, a controller can include one or more computers operating
as a management device controlling other devices in a manner to
fulfill described roles, responsibilities, or functions. One should
appreciate that the disclosed techniques provide many advantageous
technical effects including generation and application of
therapeutic acoustic signals to be applied to target tissues.
[0020] In FIG. 1, Time-Reversed Mirroring (TRM) Electro-Magnetic
Acoustic (EMA) treatment system 100 can comprise several
components. In some embodiments, at least some of the components
can be combined to form single integral devices, even a portable
device. In other embodiments the components can be physically
distributed where the components exchange data over a
communications network, wired or wireless. In more preferred
embodiments, the components communicate over a wired network to
reduce possible EM interference. It is also contemplated the
components could communicate over an optic fiber network to reduce
metal components. Such an approach is considered an advantage when
the components are used within conjunction of a strong magnetic
field generator.
[0021] A brief theoretical overview will aid the reader in
understanding the disclosed concepts. System 100 can comprise EM
source 140 that emits RF EM radiation signal 145 toward tissue
subject area 161 within patient 160. In the example shown, tissues
163A or 163B within subject area 161 can comprise one or more of
conductivity gradient 170, typically located at a boundary between
tissues. As EM radiation signal 145 impinges on gradient 170,
radiation signal 145 induces gradient 170 to generate an acoustic
signal 135 (e.g., ultrasound). Induced acoustic signal 135 can be
detected, time-reversed, and amplified to generated treatment
signal 155 that is directed back toward gradient 170. The
Applicant's own work provides a detailed discussion regarding
induced acoustic signals and using a TRM treatment signal as
discussed in co-owned U.S. Pat. No. 6,535,625 to Chang et al.
titled "Magneto-Acoustic Imagining" filed on Sep. 24, 1999 and
co-owned U.S. Pat. No. 6,974,415 to Cerwin et al. titled
"Electromagnetic-Acoustic Imagining" filed on May 22, 2003, and in
U.S. patent application publication U.S. 2007/0038060 to Cerwin et
al. titled "Identifying and Treating Bodily Tissues Using
Electromagnetically Induced, Time-Reversed, Acoustic Signals" filed
on Jun. 9, 2006. The Applicants' previous approaches failed to
appreciate that a TRM acoustic treatment signal 155 can be
constructed or otherwise generated to have desired properties based
on the full conductivity topology of the region rather than merely
mirroring an induced acoustic signal back toward conductivity
gradient 170. The Applicants' previous approaches also failed to
appreciate interactively monitoring various measured parameters
associated with a conductivity topology or adjusting therapeutic
treatment signals accordingly (e.g., real-time ablation, focus,
shape, etc.).
[0022] EM source 140 is configured to emit Radio Frequency (RF)
signals toward subject area 161. Preferred RF signals comprise a
frequency in the range from 1 MHz to 500 MHz, more preferably from
1.0 MHz to 400 MHz, and yet more preferably from 1 MHz to 20 MHz.
EM source 140 can also take on many different forms including a
Helmholtz coil, a magnetic resonance imaging system, or other
apparatus capable of generating the desirable RF signals.
Furthermore, EM source 140 can be configured to emit two or more
distinct signals (e.g., RF signals having distinct peaks) or a
spectrum of signals, which can be used for diagnostic or
therapeutic purposes as discussed below. Transmitted signals are
discussed further with respect to FIGS. 4A and 4B.
[0023] Input signal 145 can be generated according to any desired
function. In some embodiments, signal 145 could include a single,
persistent dominate frequency peak. In other embodiments, signal
145 could include multiple, distinct frequency peaks (See FIGS. 4A
and 4B). In yet other embodiments signal 145 can be chirped (e.g.,
has a specified rate of frequency change, up or down). Regardless
of the form of signal 145, the inventive subject matter is
considered to include identification, diagnosis, or treatment of
target tissues based on the various input properties of signal 145
(e.g., frequency, chirp, phase, amplitude, spectrum, etc.)
[0024] System 100 also preferably includes transducer array 130
comprising a plurality of individual transducers adapted to collect
acoustic signals 135 originating from patient 160. Acceptable
transducers can be based on piezoelectric crystals adapted to
convert acoustic signals 135 into acoustic data 115. Acoustic data
115 can include electrical signals representative of induced
acoustic signal 135. The transducers of array 130 can also function
as acoustic emitters that can direct acoustic signals back toward
patient 160 as governed by acoustic emitter instructions 125. The
emitted acoustic signals can take the form of treatment signal 155
generated to target a target tissue, tissues 163A or 163B for
example.
[0025] Array 130 can be arranged according to various geometries to
best suit a target patient or therapy. Contemplated geometries
include one or more linear arrays, annular arrays, rectangular
arrays, combinations arrays, flexible sheet of arrays, three
dimensional arrays, or other configurations. A preferred array
comprises an area covering capability to ensure suitable
acquisition of acoustic data 115 originating from patient 160.
Additionally, preferred arrays provide for directing treatment
signal 155 toward a target tissue.
[0026] Although array 130 is illustrated as both a receiver and
emitter, it is also contemplated that two or more arrays could be
used to serve various functional roles. For example, a first array
130 could be placed on an upper surface of patient 160 to collect
induce acoustic signal 135 while a second array could be place
under patient 160 to emit treatment signal 155. In embodiments
having multiple arrays 130, each array can be individually
configured to receive induced acoustic signal 135, to emit
treatment signals 155, to provide constructive or destructive
interface with other arrays, to shape treatment signal 155, or to
operate as desired under control of TRM controller 120. In some
embodiments, one array 130 could emit a TRM signal while another
array emits a constructed treatment signal lacking a TRM component
of induced acoustic signal 135.
[0027] Array 130 can be placed directly on patient 160 or placed
adjacent to an intermediary material that is in direct physical
contact with patient 160. For example, patient 160 could be covered
with an acoustic gel through which array 130 transmits or receives
acoustic signals.
[0028] Preferred embodiments of system 100 also include TRM
controller 120 capable of receiving acoustic data 115, analyzing
acoustic data 115, and generating acoustic emitter instructions
125. Preferably TRM controller 120 generates acoustic emitter
instructions 125 based on properties of subject area 161 as
determined from a measured conductivity topology as discussed
below. Acoustic emitter instructions 125 represent control signals
sent to array 130 that instruct array 130 to emit treatment signal
155. One should appreciate that treatment signal 155 comprises an
aggregation of acoustic signals individually emitted by each
transducer of array 130. Treatment signal 155 can be constructed
based on calculations performed by TRM controller 120, or could
minimally be a TRM version of induced acoustic signal 135.
[0029] TRM controller 120 can also be coupled to imaging apparatus
180, which visually displays image data related to subject area 161
as derived from acoustic data 115. In the example shown, imaging
apparatus 180 receives input from both TRM controller 120 and EM
source 140 to display an image. For example, where EM source 140
includes an MRI apparatus, output from the MRI apparatus can be
overlaid with the TRM controller's acoustic imaging data to
generate a composite image for at least a portion of subject area
161. Imaging data from TRM controller 120 can include digital
models constructed from acoustic data 115 where the digital models
can provide details about tissue subject area 161, possibly
including tissues 163A or 163B.
[0030] FIG. 2 provides a schematic overview of a possible TRM
controller 220. In a preferred embodiment, controller 220 comprises
a computing device having processor 227 capable of executing one or
more software instructions stored in memory 222. In some
embodiments, TRM controller 220 can be a desktop computer while in
other embodiments controller 220 can be a handled or portable
device. Regardless of the physical form of controller 220,
controller 220 operates to receive acoustic data from a transducer
array, analyze the acoustic data, or generate instructions for the
transducer array to emit a treatment signal.
[0031] Memory 222 can include any suitable computer readable media
including flash, RAM, SRAM, DRAM, hard disk drive, solid state
disks, optical media, magnetic media, or other types of memory.
[0032] Controller 220 can also include TRM database 223, possibly
implemented within a portion of memory 222, where additional
information or data can be stored. In some embodiments, TRM
database 223 stores information relating to a treatment including
patient data, known types of tissues and their properties,
treatment parameters, therapy regimes, programmed therapies, or
other type information that can be used to construct an acoustic
treatment signal. It is also contemplated that TRM database 223 can
be used to record treatment sessions, image data derived from
inbound acoustic data, transducer array data, management
information relating to each transducer, or any other additional
information.
[0033] Acoustic data input 215 represents an I/O interface to a
transducer array, though which controller 220 receives acoustic
data collected by the transducer array. Data input 215 could
comprise a wired or wireless interface as desired, while a physical
wired interface would be more preferable. In some embodiments, data
input 215 could comprise a network connection to a remote array.
Contemplated interfaces that could be utilized for data input 215
include analog interfaces, digital interface, serial interfaces,
Ethernet interfaces, or other types of interfaces for receiving
data.
[0034] Collected acoustic data can be analyzed according to any
desired algorithm. Preferably, the acoustic data is analyzed to
derive a conductivity topology a subject area, where the properties
of the topology can be used to generate a treatment signal.
Furthermore, information stored within TRM database 223 can also be
used in conjunction with the collected acoustic data to determine
an appropriate treatment signal. For example, acoustic data could
be collected from a subject area having a tumor. Controller 220
uses the acoustic data to develop a three dimensional model of the
tumor and surrounding areas based on the measured conductivity
topology. Controller 220 can consult TRM database 223 to determine
a type of tissue, preferably based on stored known acoustic,
conductivity, or other characteristics of tissues. The controller
can then modify a treatment signal appropriately to target the
specific tissue.
[0035] Controller 220 can use information from TRM database 223 to
provide additional information to a technician. For example,
controller 220 can annotate regions of interest on a display,
highlight specific area, provide auditory indicators, or other
information to help guide a technician operating controller
220.
[0036] Controller 220 can also include user interface 280 through
which a technician or other user can supply input to or receive
output from controller 220. Controller 220 could use interface 280
to provide image data over interface 280. Interface 280 could also
allow a technician guide a specific treatment via keyboard, pointer
devices, or other inputs. The user input can also be used to modify
a treatment signal, possibly through selecting a treatment area,
increasing or decreasing amplitude, exposure time, or other
treatment parameters. Furthermore, controller 220 can also include
I/O interface 240 configured to exchange data with an EM source.
Such an embodiment provides for cooperation between devices when
gathering data regarding a target tissue.
[0037] Controller 220 can generate an acoustic treatment signal
based on the information derived from the collected acoustic data,
in TRM database 223, from user input gathered through interface
280, imaging information, or other available information.
Preferably the acoustic treatment signal can be constructed as a
time-reversed mirrored (TRM) signal, where controller 220 instructs
the emitter array to generate the TRM treatment signal and to
target a target tissue.
[0038] Although TRM controller 220, thus far, has been presented in
view of a fairly complex computing device capable of constructing a
desired TRM treatment signal, one should appreciate that TRM
controller 220 can also be passive controller. As passive
controller can optionally lack the computational complexity of TRM
controller 220, while still operating to control a transducer
array, preferably through dedicated (e.g., non-field programmable)
hardware. In such an embodiment, the passive controller simply
collects acoustic data from the transducer array, and then directly
instructs the array, or other emitters, to generate a time reversed
mirrored signal, possibly with increased gain for treatment
purposes. It should be appreciated that the collected acoustic data
or collected induced acoustic signal represents the conductivity
topology of the tissue subject area as opposed to a mere
conductivity gradient.
[0039] It is also contemplated that transducer array can function
as a passive controller where each array element merely provides a
TRM signal in response to a portion of the induced acoustic signal
incident on each element. A preferred passive controller, even in
the form of a transducer array, is configured to provide a TRM
treatment signal back toward the tissue subject area based on the
subject area's conductivity topology. For example, a technician
could manually adjust the parameters of the in real-time array as
necessary for a desired treatment, even when the passive controller
lacks processor 227, database 223, or even memory 222. As the
technician observers the conductivity topology via output from the
passive controller, the technician can instruct the array to alter
the parameters of the returning TRM signal (e.g., gain, focus,
phase, chirp, etc.).
[0040] As briefly discussed above, one should note that the
treatment signal can be a pure time reversed mirrored signal of a
received induced acoustic signal, possibly where the gain of the
TRM signal is increased to apply a specific treatment to a target
tissue. In such an embodiment, the time reversed treatment signal
represents a TRM acoustic signal of the original induced acoustic
signal. In more preferred embodiments, the time reversed treatment
signal represents a constructed or calculated treatment signal
where the calculated treatment signal is generated as a function of
a measured conductivity topology of a subject tissue area.
Contemplated TRM acoustic treatment signals could include TRM
components from the original induced acoustic signal or even lack
such a component. One should appreciate that controller 220 can
construct, shape, focus, or otherwise generate an acoustic
treatment signal, which can be applied as an acoustic therapy to a
target tissue.
[0041] FIG. 3A provides a more detailed example of how an acoustic
treatment signal 355A targets one or more target tissues 363A or
363B based on a measured conductivity topology 370. As discussed
previously, RF EM radiation bathes tissue subject area 361, which
induces conductivity topology 370 to generate internally sourced
acoustic signals (e.g., ultrasound). Previous efforts merely
generated an amplified TRM signal that is mirrored back toward a
source conductivity gradient. The disclosed approach fully
recognizes the acoustic data received from a subject area 361
represents a measure of a full conductivity topology 370, which in
turn reflects properties of subject area 361 and its internal
tissues 363A or 363B. The measured parameters associated with
conductivity topology can then be leveraged for generating
treatment signal 355A. In the example shown, conductivity topology
370 comprises a topology associated with two tissues 363A and 363B
for illustrative purposes. Naturally, the number and complexity of
tissues within a subject tissue area can vary substantially while
still falling with in the scope of the inventive subject
matter.
[0042] A measured conductivity topology represents a model of the
conductive structure associated with subject area 361. One should
appreciate that measured conductivity topology can be substantially
different than other known methods of modeling internal tissues.
For example, conventional ultrasound imaging essentially models
internal tissues based on differences in the physical density of
the tissues. The present inventive subject matter models tissues
based on their electrical parameters as derived from acoustic data.
The two different models are quite distinct.
[0043] Conductivity topology 370 can be defined by a TRM controller
according to many different measured parameters derivable from
received acoustic data. A measured conductivity topology comprises
information relating to the geometric parameters of the
conductivity topology 370, including a three dimensional structure.
Geometric parameters can include location, size, dimensions,
orientation, or other parameters relating to the geometry of
topology 370. The geometric parameters of topology 370 can be
measured from the collected acoustic data using suitable techniques
including those employed for imaging from pulse echo. Imaging based
on pulse echo is described more fully in "Fundamentals of Digital
Ultrasound Imaging" by C. F. Schuller et al. (IEEE Trans. On Sonics
and Ultrasonics, SU-31, 195-217 (1985)), and in "Medical Ultrasound
Imaging" by Stephen Hughes (Physics Education, Volume 36, No. 6,
468-475 (2001)). Interestingly, the paper titled "Imaging Tissue
Conductivity via Contactless Measurements: A Feasibility Study", by
Gencer et al., published in Electrik, Vol. 6, No. 3, 1998,
discusses measuring a tissue's conductivity by detecting induced
currents, but fails to recognize the measurement of conductivity
can be achieved via collection of induced acoustic signal data.
[0044] Another contemplated type of parameter by which conductivity
topology 370 can be measured includes acoustically measured
conductivity parameters. Conductivity parameters represent an
actual measure of conductivity from the tissues via analysis of the
collected acoustic data. Conductivity can be measured based on the
acoustic signal strength resulting from conductivity of the tissue.
Some regions of topology 370 can have a high acoustic signal
strength representing high conductivity while low conductivity
regions will have low acoustic signal strength.
[0045] Deriving a measured conductivity from the acoustic data can
comprise incorporation of additional data beyond the collected
acoustic data. Example additional data that can be used to measure
the conductivity can include parameters relating to the transmitted
RF radiation (e.g., frequency, spectrum shape, phase, time of
flight, direction etc.), characterization data of similar tissues
having known conductivity properties, or other data accessible for
analysis.
[0046] Measured conductivity parameters represent just one class of
a broader class of electro-magnetic properties. Electro-magnetic
properties of tissues within a tissue subject area are considered
to include conductance, resistance or impedance, inductance,
capacitance, permittivity, electric susceptibility, dielectric
dispersion, dielectric relaxation, or other measurable
electro-magnetic parameters that can be derived from the collected
acoustic data.
[0047] Measured electro-magnetic properties of tissues, including a
conductivity gradient, are consider to dependent on one or more
properties of an input EM signal. Example input EM signal
properties can that can be folded into measuring the
electro-magnetic properties of the tissues, or other type of
measured parameters, including input frequency, spectrum, phase,
amplitude, chirp, or other input properties.
[0048] Another type of tissue property that can be measured from a
conductivity topology can include mechanical properties. Example
mechanical properties can include density, elasticity, Young's
modulus, bulk modulus, shear modulus, bending strength,
hardness/softness, or other physical properties of tissues.
[0049] Yet another type of measurable parameters that can be
associated with a measured conductivity topology can include
dynamic parameters. Thus far, the above referenced measured
parameters have been mainly presented as if they have single static
values with respect to time or distance. It should be appreciated
that many of the measured parameters can change dynamically with
respect to time or geometry. Example dynamic parameters that change
in time can include a rate of change, a flow, Doppler shifts, or
other temporal based parameters. Example dynamic parameters that
change with location or distance include density variations, volume
fluctuations, or other changes in values associated with variation
in geometry. One should note that a tissue's various
electro-magnetic parameters could vary over a volume within the
tissue subject area 361. The measurement of such variations from
acoustic data is considered to fall within the scope of the
inventive subject matter.
[0050] The reader should bear in mind a TRM controller providing
instructions to array 330 can adjust treatment signal 355A in
real-time. As dynamic parameters change in time or geometry, likely
due to treatment or movement, the TRM controller can change the
treatment signal accordingly. For example, a surface geometry of
target tissue 363A or 363B could change, causing measured
parameters of their corresponding conductivity topologies to
change. Such changes can be used a triggers to adjust a treatment
accordingly. Furthermore, a technician can interactively monitor
the effects of a treatment via observing changes in the measured
parameters. Treatment signal could be adjusted automatically
according to a protocol, according to instructions from the
technician, or other input.
[0051] Still another type of measured parameter includes signal
parameters associated with the induced acoustic signal as
represented by collected acoustic data. In some embodiments, the
signal parameters can be associated with the raw data collected by
or derived from transducer array 330, or even each individual
transducer of array 330. Signal parameters can include frequency,
frequency spectrum, time-of-flight, phase, noise level, signal
level, Fourier components, or other measured values derived from
the signal of the collected acoustic data.
[0052] Of particular note, acoustic data representing induced
acoustic signals can include a signal parameter comprising a
signal-to-noise ratio (S/N). As acoustic data is collected, the S/N
can be calculated for various portions of the measured conductivity
topology. In some embodiments, tissues or their properties are
characterized by expected S/N as a function of input frequency or
spectra. Measured S/N can be compared to expected S/N to properly
construct treatment signal 355A. For example, the comparison can be
used to identify tissues, selected tissues for treatment, shape
treatment signal 355A, focus treatment signal 355A, or other
purposes. Additionally, treatment signal 355A could be formed from
acoustic data components of the induced acoustic signal that have
an S/N greater than a threshold, less than a threshold, or even
within an bounded region of S/N values.
[0053] Although only a few types of measured parameters of a
measured conductivity topology are discussed, all possible measured
parameters are contemplated. Furthermore, the measured parameters
contribute to building the measured conductivity topology, even
where the measured topology includes a three dimensional model of
the properties of tissue subject area 361 as derived at least
partially from the acoustic data.
[0054] As discussed previously, measured parameters of conductivity
topology 370 can be considered functions of the properties of an
input EM signal. For example, a conductive portion of a tissue
might be responsive to varying frequencies because of the tissues
electrical properties. At a low frequency, the tissue might not
contribute significantly to conductivity topology 370. While the
tissue might have a significant contribution at a high frequency.
One should also appreciate that tissue properties affect one
another; a high conductivity tissue might contribute poorly to a
measured conductivity topology if it has a high density. Some
measured parameters vary with frequency, even if the frequency
variation is within a few MHz of an input signal. Contemplated
input EM signal properties that can contribute to the measured
parameters include frequency, spectrum, sweep, chirp, phase, or
even EM source location.
[0055] The above discussed measured parameters contribute to
various degrees to the measured conductivity topology of topology
370. In some cases, the contribution of a measured parameter can be
significant. For example, a prepared boundary of a tumor, an
encapsulated tumor for example, might have a significant
conductivity gradient, which would provide a strong induced
acoustic signal. Neighboring or surrounding tissues might have a
reduced or a low contribution to the measure conductivity topology
by having a low conductivity gradient, yielding a low induced
acoustic signal. In either case of (a) a measured parameter having
a significant contribution or (b) lacking a significant contribute
to a measured topology; information derived from the collected
acoustic data can be applied toward generating an acoustic
treatment signal.
[0056] Measured conductivity topologies as discussed above provide
a great deal of insight into properties of tissues within tissue
subject area 361. One should also appreciate that topological
information can be available beyond a measured conductivity
topology. Other topologies can include physical topologies,
acoustic topologies, or other types of measured topologies that can
be derived from other sources (e.g., CT scans, MRI scans,
Ultrasounds, etc.). One or more other topologies can be combined
with the measured conductivity topology to form a hybrid topology.
The values of measured parameters can also depend on information
gain from other measured topologies, which can in turn be used to
adjust treatment signal 355A.
[0057] Treatment signal 355A can be constructed as a function of
the measured conductivity topology (e.g., the various measured
parameters). In the example shown, treatment signal 355A is
generated by transducer array 330 as instructed by a TRM
controller. The TRM controller generates instructions so treatment
signal 355A would include a TRM component representative of an
induced acoustic signal as discussed above. In more preferred
embodiments, treatment signal 355A is further constructed as a
function of one or more of the measured parameters associated with
the measured conductivity topology.
[0058] Treatment signal 355A can be constructed by instructing
array 330 to create an acoustic signal having various desired
acoustic signal properties. Preferably treatment signal 355A has a
TRM component as discussed above. In the example shown in FIG. 3A,
treatment signal 355A is directed to target tissue 363A, which is
considered to have a high conductivity 371 and a significant
contribution to the measured conductivity topology as represented
by the heavy dashed line associated with the conductivity topology
370. As illustrated, treatment signal 355A is contemplated to
include a TRM component of an induced acoustic signal originating
from topology 370 (e.g., tissue 363A). In addition, it is
specifically contemplated that treatment signal 355A comprises a
time-reserved acoustic signal having increased gain over that of
the induced acoustic signal, where the high gain TRM acoustic
treatment signal 355A can be used for therapeutic purposes as
discussed further below. In yet more preferred embodiments,
treatment signal 355A can also have other constructed properties.
For example, treatment signal 355A can be generated to target
specific portions of tissues 363A, or can be pulsed or altered with
time as desired for a therapy regime.
[0059] Of particular note, treatment signal 355A can be constructed
to have significant therapeutic value by modifying its properties.
By increasing the gain of treatment signal 355A relative to an EM
induced acoustic signal, treatment signal 355A can supply a
significant amount of sonic energy to target tissue 363A to heat
the tissue. In some embodiments, treatment signal 355A has
sufficient gain to apply a hyperthermia treatment to target tissue
363A. In addition, the gain could be increased to ablate (e.g.,
vaporize) target tissue 363A. Such an approach is advantageous for
treating tumors or cancerous tissues. The applied hyperthermia
treatment could be continuously applied, or applied over multiple
treatment sessions separated by minutes, hours, days, weeks, or
other time period to allow the patient to recover or heal between
treatments.
[0060] Given that the disclosed system provides a volumetric
approach to measuring conductivity topology, the system preferably
comprises sufficient resolution to target a volume within an error
ellipsoid having a maximum dimension of no more than 5 mm, more
preferably no more than 1 mm, and yet more preferably no more than
0.3 mm. These resolutions can be achieved through higher input
frequencies of RF radiation, through increasing resolution of array
330, or positioning transducers. Resolution of array 330 can be
increased by increasing transducer density of the array. It is also
contemplated that the more detailed resolutions (e.g., less than
0.3 mm) could be achieved through the use of phonon lasers,
possibly TRM-based phonon lasers. For example, the phonon laser
described in U.S. Pat. No. 7,411,445 to Kurcherov et al. titled
"Phonon Laser", filed Apr. 27, 2006, could be adapted for use with
the disclosed techniques to achieve resolutions less than 100
.mu.m.
[0061] One should appreciate the disclosed techniques can be
applied in conjunction with other forms of therapy. It is also
contemplated that use of the disclosed techniques is expected to
reduce the need for more invasive forms of treatment, surgery,
radiation, or chemotherapy for example. It is also contemplated the
disclosed techniques could be used to internally tag target tissue
363A by sonically branding tissue 363A so a surgeon can easily
identify a target tissue during surgery.
[0062] FIG. 3A illustrates using treatment signal 355A to target a
high conductivity tissue, tissue 363A. An astute reader will
appreciate that conductivity topology 370 will likely have
contours, shapes, or other variations in measured parametric
values. These can also be used to construct an acoustic treatment
signal.
[0063] FIG. 3B provides another exemplary approach based on the
same tissues of FIG. 3A. In this example, treatment signal 355B is
constructed to target tissue 363B as opposed to tissue 363A. The
measured low conductivity 373 of tissue 363B is considered lower
than that of the measured conductivity 371 of tissue 363A. Rather
than merely returning a high gain TRM acoustic signal back toward
subject area 361, a TRM controller has constructed treatment signal
355A targeting a low signal area. Such an approach can be achieved
by analyzing the measured conductivity topology of subject area 361
to derive values for various measured parameters. The measured
parameters can be folded into one or more functions or algorithms
used to generate treatment signal 355B, even if the selecting of
parameters includes targeting areas lacking a significant
contribution to the measured conductivity topology. For example,
acoustic data from tissue 363A could be removed or filtered from
the data set used to construct treatment signal 355A, possibly by
filtering based on S/N.
[0064] The approach of selecting tissues based on the measured
conductivity topology parameters can be used to target tissues that
lack a significant contribution to the conductivity topology. For
example, a feeder vessel to a tumor could be targeted as opposed to
a tumor itself. Additionally, tissue surrounding a tumor could be
targeted to isolate the tumor or isolate other tissues of
interest.
[0065] Treatment signal 355A could also comprise a completely
constructed TRM acoustic treatment signal. A TRM controller has a
wealth of information regarding a measured conductivity topology
based on the various measured parameters of the corresponding
conductivity topology 370. The TRM controller can use the
information, including other externally obtained information, to
construct a calculated TRM acoustic treatment signal lacking a TRM
component of an induced acoustic signal. For example, the TRM
controller can use the measured geometry of the measured topology,
electrical parameters, or other information to target tissues that
lack a significant contribution to the measured parameters. One can
consider this approach as targeting background regions (e.g.,
regions lacking significant signals), tissue 363B for example, as
opposed to foreground regions (e.g., regions contributing
significant signals). Alternatively one can consider the above
approach as "inverting" the data similar to working with a
photographic negative. Such an approach can be achieved by the TRM
controller modeling a virtual acoustic signal based on the measured
parameters where the virtual acoustic signal is model as if it
originated from the background regions, tissue 363B for example.
The virtual acoustic signal can then be used as foundation for
generating the calculated TRM acoustic treatment signal as
described above.
[0066] One should keep in mind that treatment signals 355A or 355B
are emitted from array 330 comprising many individual, discrete
transducers or other acoustic emitters. Each transducer is
instructed individually to emit individual acoustic signals, which
aggregate to form treatment signals 355A or 355B. The individual
acoustic signals can be generated so that they constructively, or
destructively, interfere properly at their respective target
tissue. The constructed acoustic treatment signals can be formed by
taking into account materials intermediary between array 330 and
target tissues 363A or 363B. Intermediary materials could include
other tissues having various acoustic transmission properties,
density for example. A TRM controller can provide instructions to
the individual transducers of array 330 to emit individual acoustic
signal according to desired properties: frequency, amplitude,
relative phase, location, timing, or other properties.
[0067] One should appreciate that a treatment can have temporal
aspects where the treatment signals can vary with time under a
controlled regime, possibly based on a programmed treatment. The
TRM controller can adjust the treatment signal according the
programmed treatment as desired, including in response to feedback
from newly acquired acoustic data or from other external input
(e.g., user input, MRI machine, etc.). As treatment is applied, the
TRM controller can change the treatment signal(s) frequency, phase,
chirping, amplitude, target location, or other properties.
[0068] One should appreciate that applying a treatment to a target
tissue as discussed above is considered to include weighting an
acoustic treatment signal based on measured parameters. For
example, when applying a TRM acoustic treatment signal constructed
based on the weighting of the S/N resulting from the conductivity
topology, the resulting treatment is a conductivity weighted
acoustic treatment. Still further, when the treatment signal has
sufficient gain to ablate a target tissue, the TRM acoustic
treatment signal represents a conductivity-weighted acoustic
ablation signal. It is contemplated that any measured parameter
could be used to weight the acoustic treatment signal.
[0069] Typically an input RF radiation comprises a single dominate
frequency (f). When the radiation induces an acoustic signal, the
acoustic signal has a dominate frequency component of 2f. It should
be further appreciated that an input signal can include more than
one component, possibly having more than one frequency peak, or
even a spectrum.
[0070] Consider FIG. 4A where a pair of transmitted RF signals are
generated at f1=3.875 MHz and f2=6.125 MHz and are directed to a
target tissue. The graph is presented in the frequency domain to
clearly illustrate there can be more than one frequency peak, or a
spectrum. An expected acoustic signal (e.g., ultrasound) would have
2f components at 7.75 MHz and 12.25 MHz, two times the transmitted
frequencies. Indeed that does occur. Interestingly, other acoustic
peaks are also present that are distinct from the 2f
components.
[0071] FIG. 4B illustrates received acoustic signals induced by the
transmit pair of FIG. 4A. In this example, two main peaks are
identified representing a difference between the pair's frequencies
at f2-f1=2.25 MHz, and sum of the pair's frequency f2+f1=10 MHz.
Note the 2f components are removed for clarity. Rather than
filtering for just the 2f components as was previously done, the
Applicants have recognized that other peaks, or parts of the
frequency spectrum, carry additional information. For example, a
first tissue might provide a strong difference component while a
second tissue might provide a strong sum component. Therefore
diagnostic or treatment information can be gained based on the
recorded acoustic spectrum. Additional, TRM acoustic treatment
signal can be constructed based on the other signals beyond the
just the expect 2f components to selectively target the first or
second tissue. Such information would have been lost using
previously known techniques.
[0072] To generalize, a transmitted input RF signal can comprise
multiple parts. When the input frequencies, or even spectra, are
known, then the resulting induced acoustic signal can be used to
characterize different tissues based on the inputs and the measured
conductivity topologies. Once characterized, possibly based on S/N
of the frequency peaks as illustrated, the properties of known
tissues can be folded into construction of an appropriate TRM
acoustic treatment.
[0073] Thus far the disclosed techniques have been presented within
the context of providing a treatment, especially with respect to
treating tumors through ablation or heating. Other types of
treatments are also contemplated. One possible treatment includes
targeting vein or artery maladies, possibly for cosmetic purposes,
where varicose veins could be collapsed or spider veins could be
eliminated. Another possible treatment could include lipoblasty
where fatty tissues are targeted to reduce or eliminate fat. Yet
another treatment can include reshaping corneas, correcting lens,
or other ocular treatments.
[0074] It is further contemplated that a target tissue could be on
the surface of a patient as opposed to being internal to a patient.
A patient could be placed in an acoustic transmission medium (e.g.,
water, gel, etc.) and a TRM acoustic treatment signal can be
constructed to pass through the medium to the surface tissue.
[0075] It should be apparent to those skilled in the art that many
more modifications besides those already described are possible
without departing from the inventive concepts herein. The inventive
subject matter, therefore, is not to be restricted except in the
spirit of the appended claims. Moreover, in interpreting both the
specification and the claims, all terms should be interpreted in
the broadest possible manner consistent with the context. In
particular, the terms "comprises" and "comprising" should be
interpreted as referring to elements, components, or steps in a
non-exclusive manner, indicating that the referenced elements,
components, or steps may be present, or utilized, or combined with
other elements, components, or steps that are not expressly
referenced. Where the specification claims refers to at least one
of something selected from the group consisting of A, B, C . . .
and N, the text should be interpreted as requiring only one element
from the group, not A plus N, or B plus N, etc.
* * * * *