U.S. patent application number 10/041494 was filed with the patent office on 2003-07-10 for method and system for analyzing respiratory tract sounds.
Invention is credited to Botbol, Meir, Kushnir, Igal.
Application Number | 20030130588 10/041494 |
Document ID | / |
Family ID | 21916805 |
Filed Date | 2003-07-10 |
United States Patent
Application |
20030130588 |
Kind Code |
A1 |
Kushnir, Igal ; et
al. |
July 10, 2003 |
Method and system for analyzing respiratory tract sounds
Abstract
A system and method for analyzing the respiratory tract sounds.
The system comprises a plurality of transducers that are placed on
the individual's skin over the thorax. A signal analysis module
analyzes sound signals recorded by the transducers and produces a
first analysis product. A display device displays an image based
upon the first analysis product. The image includes a pattern with
an overall shape corresponding to that of the respiratory system.
Regions in the image that are suspected of having a pathological
condition may be indicated.
Inventors: |
Kushnir, Igal; (Pardes
Hanna, IL) ; Botbol, Meir; (Pardes Hana, IL) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
21916805 |
Appl. No.: |
10/041494 |
Filed: |
January 10, 2002 |
Current U.S.
Class: |
600/529 |
Current CPC
Class: |
A61B 5/08 20130101; A61B
7/003 20130101; A61B 7/026 20130101 |
Class at
Publication: |
600/529 |
International
Class: |
A61B 005/08 |
Claims
1. A system for analyzing the respiratory tract of an individual,
comprising: (a) a plurality of transducers for placing in a
plurality of a pre-defined locations on the individual's skin over
the thorax; (b) a signal analysis module for analyzing sound
signals recorded by each of said transducers to produce a first
analysis product; and (c) a display, said display displaying an
image based upon the first analysis product, which image includes a
pattern with an overall shape corresponding to that of the
respiratory system and an indication on said pattern of regions in
the image which are suspected of having a pathological
condition.
2. A system for analyzing sounds in at least a portion of an
individual's respiratory tract comprising: (a) a plurality of N
transducers, each transducer configured to be fixed on a surface of
the individual over the thorax, the ith transducer being fixed at a
location x.sub.i and generating a signal P(xi,t) indicative of
pressure waves at the location x.sub.i; for i=1 to N; and (b) a
processor configured to receive the signals P(x.sub.i,t) and
determine an average acoustic energy {tilde over
(P)}(x,t.sub.1,t.sub.2) at at least one position x over a time
interval from a first time t.sub.1 to a second time t.sub.2, {tilde
over (P)} being determined in an algorithm involving at least one
of the signals P(xi,t).
3. The system according to claim 2 further comprising a
two-dimensional display device.
4. The system according to claim 3 wherein the processor is further
configured to display a representation of the function {tilde over
(P)}.
5. The system according to claim 2 wherein the processor is further
configured to compare the average acoustic energy {tilde over (P)}
to one or more predetermined functions {tilde over (F)} and
determine a function {tilde over (F)}.sub.0 from among the
functions {tilde over (F)} most similar to {tilde over (P)}.
6. The system according to claim 5 wherein the processor is further
configured to make a diagnosis based upon the determined
function.
7. The system according to claim 2 wherein the average acoustic
energy {tilde over (P)} over a time interval from t.sub.1 to
t.sub.2 is determined at a location x.sub.i of a transducer using
the algebraic expression: 5 P ~ ( x i , t 1 , t 2 ) = t 1 t 2 P 2 (
x i , t ) t .
8. The system according to claim 2 wherein the function {tilde over
(P)} is determined at one or more locations x in an algorithm
comprising: (a) determining an average acoustic energy {tilde over
(P)}(x.sub.i,t.sub.1,t.sub.2) over a time interval from t.sub.1 to
t.sub.2 at a plurality of locations x.sub.i of transducers; and (b)
determining an average acoustic energy {tilde over
(P)}(x,t.sub.1,t.sub.2) at at least one location x by interpolation
of the determined {tilde over (P)}(x.sub.i,t.sub.1,t.sub.2).
9. The system according to claim 8 wherein an average acoustic
energy {tilde over (P)}(x.sub.i,t.sub.1,t.sub.2) is determined over
a time interval from t.sub.1 to t.sub.2 at a plurality of locations
x.sub.i of transducers using the algebraic expression: 6 P ~ ( x i
, t 1 , t 2 ) = t 2 t 2 P 2 ( x i , t ) t .
10. The system according to claim 8 wherein an average acoustic
energy is determined at at least one location x by interpolation of
the determined {tilde over (P)}(x.sub.i,t.sub.1,t.sub.2) using the
algebraic expression: 7 P ~ ( x , t 1 , t 2 ) = i = 1 N P ~ ( x i ,
t 1 , t 2 ) g ( x , x i , ) ( 2 ) where g(x,x.sub.i,.sigma.) is a
kernal satisfying 8 2 g = g ( 3 ) i = 1 N g ( x , x i , ) is
approximately equal to 1. ( 4 )
11. The system according to claim 10 wherein g(x,v.sub.i.sigma.) is
the kernal 9 g ( x , x i , ) = Exp - ( ( x 1 - x i 1 ) 2 2 ) Exp -
( ( x 2 - x i 2 ) 2 2 ) . ( 5 )
12. The system according to claim 2 wherein the processor is
configured to determine an average acoustic energy over a plurality
of time intervals, each average acoustic energy being determined
using an algorithm involving at least one of the signals
P(x.sub.i,t).
13. The system according to claim 2 wherein the processor is
configured to sequentially display on a display device a
representation of each determined average acoustic energy.
14. The system according to claim 2 wherein the processor is
configured to: (a) for each of one or more frequency bands, (aa)
subject the signals (P,x.sub.i,t) to band pass filtering in the
frequency band; and (ab) determine an average acoustic energy
function for the frequency band based upon at least one of the
filtered signals.
15. The system according to claim 14 wherein the processor is
configured to display one or more of the average acoustic energy
functions determined for a frequency band on a display device.
16. A method for analyzing the condition of a respiratory tract of
an individual, comprising: (a) placing a plurality of sound
transducers in pre-defined locations over one or both of an
individual's thorax; (b) recording sound by each of said
transducers over a period of time including at least one
respiratory cycle; (c) analyzing the sound recorded at each
location to obtain a first analysis product; and (d) combining the
plurality of first analysis products into a display, said display
comprising a pattern with an overall shape corresponding to that of
the respiratory system and an indication of regions thereof that
are suspected of having a pathological condition
17. A method for analyzing sounds in at least a portion of an
individual's thorax, comprising: (a) obtaining N signals P(xi,t)
for i=1 to N, the signal P(xi,t) being indicative of pressure waves
at the location x.sub.i; on a surface of the body over the thorax;
(b) determining an average acoustic energy {tilde over
(P)}(x,t.sub.1,t.sub.2) at at least one position x over a time
interval from a first time t.sub.1 to a second time t.sub.2, {tilde
over (P)} determined in an algorithm involving at least one of the
signals.
18. The method according to claim 17 further comprising displaying
a representation of {tilde over (P)} on a two-dimensional
surface.
19. The method according to claim 17 further comprising comparing
the average acoustic energy {tilde over (P)} to one or more
predetermined functions {tilde over (F)}and determining a function
{tilde over (F)}.sub.0 from among the functions {tilde over (F)}
most similar to {tilde over (P)}.
20. The method according to claim 17 wherein further comprising
making a diagnosis based upon the determined function.
21. The method according to claim 17 wherein the average acoustic
energy over a time interval from t.sub.1 to t.sub.2 is determined
at a location x.sub.i of a transducer using the algebraic
expression: 10 P ~ ( x i , t 1 t 2 ) = t 1 t 2 P 2 ( x i , t ) t
.
22. The method according to claim 17 wherein the function {tilde
over (P)} is determined at one or more locations x in an algorithm
comprising; (a) determining an average acoustic energy {tilde over
(P)}(x.sub.i,t.sub.1,t.sub.2) over a time interval from t.sub.1 to
t.sub.2 at a plurality of locations x.sub.i of transducers; and (b)
determining an average acoustic energy {tilde over
(P)}(x,t.sub.1,t.sub.2) at at least one location x by interpolation
of the determined {tilde over (P)}(x,t.sub.1,t.sub.2).
23. The method according to claim 22 wherein an average acoustic
energy {tilde over (P)}(x,t.sub.1,t.sub.2) is determined over a
time interval from t.sub.1 to t.sub.2 a at a plurality of locations
of transducers using the algebraic expression: 11 P ~ ( xi , t 1 ,
t 2 ) = t 1 t 2 P 2 ( x i , t ) t
24. The method according to claim 22 wherein an average acoustic
energy is determined at at least one location x by interpolation of
the determined {tilde over (P)}(x,t.sub.1,t.sub.2) using the
algebraic expression: 12 P ~ ( x , t 1 , t 2 ) = i = 1 N P ~ ( x i
, t 1 , t 2 ) g ( x , x i , ) ( 2 ) where g(x,x.sub.i,.sigma.) is a
kernal satisfying 13 2 g = g ( 3 ) i = 1 N g ( x , x 1 , ) is
approximately equal to 1. ( 4 )
25. The method according to claim 24 wherein g(x,x.sub.i,.sigma.)
is the kernal 14 g ( x , x i , ) = Exp - ( ( x 1 - x i 1 ) 2 2 )
Exp - ( ( x 2 - x i 2 ) 2 2 )
26. An image of a two-dimensional representation of {tilde over
(P)} produced by the method of claim 18.
27. The method according to claim 17 comprising determine an
average acoustic energy over a plurality of time intervals, each
average acoustic energy being determined using an algorithm
involving at least one of the signals P(x.sub.i,t) further
comprising sequentially displaying on a display device a
representation of each determined average acoustic energy.
28. The method according to claim 17 further comprising, for each
of one or more frequency bands: (a) subjecting the signals
P(x.sub.i,t) to band pass filtering in the frequency band; and (b)
determining an average acoustic energy function for the frequency
band based upon at least one of the filtered signals.
29. The method according to claim 28 further comprising displaying
on a display device one or more of the acoustic energy functions
determined for a frequency band.
30. A program storage device readable by machine, tangibly
embodying a program of instructions executable by the machine to
perform method steps for determining for at least one time
interval, an average acoustic energy function {tilde over (P)}
using an algorithm involving at least one signal P(x.sub.i,t)
indicative of pressure waves at a location x.sub.i on a body
surface.
31. A computer program product comprising a computer useable median
having computer readable program code embodied therein analyzing
sounds in at least a portion of an individual's body, the computer
program product comprising: computer readable program code for
causing the computer to determine for at least one time interval,
an acoustic energy function {tilde over (P)}, {tilde over (P)}
being determined in algorithm involving at least one signal
P(x.sub.i,t) indicative of pressure waves at a location x.sub.i on
a body surface.
Description
FIELD OF THE INVENTION
[0001] This invention relates to medical devices and methods, and
more particularly to such devices and methods for analyzing body
sounds.
BACKGROUND OF THE INVENTION
[0002] Body sounds are routinely used by physicians in the
diagnosis of various disorders. A physician may place a stethoscope
on a person's chest or back and monitor the patient's breathing in
order to detect adventitious (i.e. abnormal or unexpected) lung
sounds. The identification and classification of adventitious lung
sounds often provides important information about pulmonary
abnormalities.
[0003] It is also known to fix one or more microphones onto a
subject's chest or back and to record lung sounds. U.S. Pat. No.
6,139,505 discloses a system in which a plurality of microphones
are placed around a patient's chest. The recordings of the
microphones during inhalation and expiration are displayed on a
screen, or printed on paper. The recordings are then visually
examined by a physician in order to detect a pulmonary disorder in
the patent. Kompis et al (Chest, 120(4), 2001) disclose a system in
which M microphones are placed on a patient's chest, and lung
sounds are recorded. The recordings generate M linear equations
that are solved using a least-squares fit. The solution of the
system is used to determine the location in the lungs of the source
of a sound detected in the recordings.
SUMMARY OF THE INVENTION
[0004] In the following description and set of claims, two
explicitly described, calculable, or measurable variables are
considered equivalent to each other when the two variables are
proportional to one another.
[0005] The present invention provides a system and method for
recording and analyzing sounds produced by the respiratory tract in
order to produce an image that permits easy analysis of
pathological conditions of the respiratory tract. In accordance
with the invention, sounds are recorded in a plurality of locations
over an individual's thorax (including locations in one or both of
the individual's chest or back surfaces). The sounds are recorded
over a period of time, for example, over at least one respiratory
cycle and preferably over several respiratory cycles, and the
sounds recorded at each location are analyzed to produce a first
analysis product. The plurality of first analysis products are then
combined in a manner so as to produce the desired image. The first
analysis product may be a function of a signal analysis in one or
more of a variety of different parameters of the recorded signal,
such as an analysis in the frequency domain, in the time domain, in
the power domain or a combination of one or more of these domains.
In accordance with the preferred embodiment of the invention, the
sounds are analyzed in the tine and frequency domains to produce
said first analysis product said image therefrom.
[0006] In accordance with one embodiment of the invention, there is
provided a system for analyzing the respiratory tract of an
individual, comprising:
[0007] a plurality of transducers for placing in a plurality of a
pre-defined locations over the individual's thorax;
[0008] a signal analysis module for analyzing sound signals
recorded by each of said transducers to produce a first analysis
product; and
[0009] a display, said display displaying an image produced by the
analyzed sound recordings, which image includes a pattern with an
overall shape corresponding to that of the respiratory system and
an indication on said pattern of regions thereof that are suspected
of having a pathological condition.
[0010] The present invention also provides a method for analyzing
the condition of a respiratory tract of an individual,
comprising:
[0011] (i) placing a plurality of sound transducers in pre-defined
locations on one or both of an individual's chest or back over the
thorax;
[0012] (ii) recording sound by each of said transducers over a
period of time including at least one respiratory cycle;
[0013] (iii) analyzing the sound recorded at each location to
obtain a first analysis product; and
[0014] (iv) Combining the plurality of first analysis products into
a display, said display comprising a pattern with an overall shape
corresponding to that of the respiratory system and an indication
of regions thereof that are suspected of having a pathological
condition.
[0015] The term "pathological condition" refers to any deviation
from the normal, healthy condition of the respiratory tract. This
includes infection, inflammation, tumor, narrowing of the airways,
existence of a space occupying lesions in the respiratory tract,
etc.
[0016] The first analysis product may be a function of one or more
parameters of the recorded signal. The first analysis product may
be a function of an analysis made in a variety of different domains
of the recorded signal, as pointed out above.
[0017] The transducers are typically embedded in a matrix that
permits to affix them easily on the individual's skin. Such a
matrix may typically be in the form of a vest or garment for easily
placing over the individual's thorax. As may be appreciated,
different matrices may be used for differently sized individual's;
for different ages, sexes, etc.
[0018] The respiratory tract is displayed in a manner such as to
resemble the general shape of the lung, typically shaped similar to
that which can be viewed in an x-ray of the lung. The term
"similar" in this regard should be understood as meaning that a
physician can generally recognize the shape of the lung from such a
display although it is clear to any man of the art that the actual
display of said image is different than that of an x-ray
picture.
[0019] In said display, regions that are suspected to include a
pathological condition, each region is identified as such by the
existence of wheezes and crackles identified by an allowances of
the recorded sound signal in the frequency domain, are identified
and this may be in a number of ways, for example, by different
colors, by different patterns, by way of a written text, and many
other ways.
[0020] The present invention provides, by another embodiment, a
system and method for recording and analyzing respiratory tract
sounds produced in the respiratory tract. The system includes a
plurality of N transducers (microphones) configured to be attached
to an essentially planar region R of the individual's back or chest
over the individual's thorax. Positions in the region R are
indicated by two-dimensional position vectors x=(x.sup.1,x.sup.2)
in a two-dimensional coordinate system defined in the planar region
R. The ith transducer, for i=1 to N, is fixed at a position x.sub.i
in the region R and generates a signal, denoted herein by
P(x.sub.i,t), indicative of pressure waves in the body arriving at
x.sub.i.
[0021] The N signals P(x.sub.i, t) are processed by signal
processing circuit. In accordance with the invention, the
processing involves determining from the N signals an average
acoustic energy, denoted herein by {tilde over
(P)}(x,t.sub.1,t.sub.2), at least one position x in the region R
over a time interval from t.sub.1 to t.sub.2. The term "acoustic
energy" at a location is used herein to refer to a parameter
indicative of or approximating the product of the pressure and the
mass propagation velocity at that location.
[0022] In one embodiment, an average acoustic energy over a time
interval from t.sub.1 to t.sub.2 is obtained at a position of one
of the microphones using the algebraic expression 1 P ~ ( x i , t 1
, t 2 ) = t 1 t 2 P 2 ( x i , t ) t ( 1 )
[0023] where x.sub.i is the position of the microphone.
[0024] In a more preferred embodiment, an average acoustic energy
{tilde over (P)}(x.sub.i,t.sub.1,t.sub.2) over a time interval from
t.sub.1, to t.sub.2 is obtained at a plurality of positions x.sub.i
of the microphones, for example using Equation (1), and then
calculating {tilde over (P)}(x,t.sub.1,t.sub.2) at other locations
x by interpolation of the {tilde over (P)}(x.sub.i,t.sub.1,t.sub.2)
using any known interpolation method.
[0025] In a most preferred embodiment, the interpolation is
performed to obtain an average acoustic energy {tilde over
(P)}(x,t.sub.1,t.sub.2) at a position x=(x.sup.1,x.sup.2) in the
surface R using the algebraic expression: 2 P ~ ( x , t 1 , t 2 ) =
i = 1 N P ~ ( x i , t 1 , t 2 ) g ( x , x i , ) ( 2 )
[0026] where g(x,x.sub.i,.sigma.) is a kernal satisfying 3 2 g = g
( 3 ) i = 1 N g ( x , x i , ) is approximately equal to 1 ( 4 )
[0027] and where x.sub.i=(x.sub.i.sup.1,x.sub.i.sup.2) is the
position of the ith microphone and .sigma. is a selectable
parameter.
[0028] For example, the kernal 4 g ( x , x i , ) = Exp - ( ( x 1 -
x i 1 ) 2 2 ) Exp - ( ( x 2 - x i 2 ) 2 2 ) ( 5 )
[0029] may be used.
[0030] The system may optionally contain a display device for
displaying the function {tilde over (P)}. The function {tilde over
(P)} may be displayed on the display, for example using a gray
level scale, as demonstrated in the examples below. A two
dimensional graphical representation of the function {tilde over
(P)} produces an image of the body region that may be analyzed for
the detection of a disorder in the body region similar to the
analysis of images obtained by other imaging methods such as X-ray
or ultrasound imaging.
[0031] Additionally, a time interval can be divided into a
plurality of sub intervals, and an average acoustic energy {tilde
over (P)} determined over the region R for two or more of the sub
intervals. An image of {tilde over (P)} for each of these sub
intervals may then be determined and displayed sequentially on the
display device. This generates a movie showing dynamic changes
occurring in the acoustic energy in the body region, over the time
interval. For example, transducers may be placed on a person's
chest and an average acoustic energy {tilde over (P)} determined in
accordance with the invention for a plurality of sub intervals over
a breathing cycle. An image can be obtained for each of these sub
intervals and displayed sequentially so as to generate a movie
showing changes in the acoustic energy of the lungs over the
breathing cycle.
[0032] The signals P(x.sub.i,t) may also be subjected to band pass
filtering before being analyzed by the method of the invention, so
that an average acoustic energy is produced for one or more
frequency bands of interest. The functions may be superimposed on
the display device by representing each average acoustic energy
function with a different color.
[0033] The present invention provides a system for analyzing sounds
in at least a portion of an individual's respiratory tract
comprising:
[0034] (a) a plurality of N transducers, each transducer configured
to be fixed on a surface of the individual over the thorax, the ith
transducer being fixed at a location x.sub.i and generating a
signal P(xi,t) indicative of pressure waves at the location
x.sub.i; for i=l to N; and
[0035] (b) a processor configured to receive the signals
P(x.sub.i,t) and determine an average acoustic energy {tilde over
(P)}(x,t.sub.1,t.sub.2) at at least one position x over a time
interval from a first time t.sub.1 to a second time t.sub.2, {tilde
over (P)} being determined in an algorithm involving at least one
of the signals P(xi, t).
[0036] The present invention further provides a method for
analyzing sounds in at least a portion of an individual's thorax,
comprising:
[0037] (a) obtaining N signals P(xi,t) for i=1 to N, the signal
P(xi,t) being indicative of pressure waves at the location x.sub.i;
on a surface of the body over the thorax;
[0038] (b) determining an average acoustic energy {tilde over
(P)}(x,t.sub.1,t.sub.2) at at least one position x over a time
interval from a first time t.sub.1 to a second time t.sub.2, {tilde
over (P)} determined in an algorithm involving at least one of the
signals.
[0039] The present invention also provides a program storage device
readable by machine, tangibly embodying a program of instructions
executable by the machine to perform method steps for determining
for at least one time interval, an average acoustic energy function
{tilde over (P)} using an algorithm involving at least one signal
P(xi,t) indicative of pressure waves at a location x.sub.i on a
body surface.
[0040] The present invention still further provides a computer
program product comprising a computer useable medium having
computer readable program code embodied therein analyzing sounds in
at least a portion of an individual's body, the computer program
product comprising:
[0041] computer readable program code for causing the computer to
determine, for at least one time interval, an acoustic energy
function {tilde over (P)}, {tilde over (P)} being determined in
algorithm involving at least one signal P(xi,t)indicative of
pressure waves at a location x.sub.i on a body surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] In order to understand the invention and to see how it may
be carried out in practice, a preferred embodiment will now be
described, by way of non-limiting example only, with reference to
the accompanying drawings, in which:
[0043] FIG. 1 shows a system for obtaining an analyzing body sound
in accordance with one embodiment of the invention;
[0044] FIG. 2 shows a flow chart for carrying out a method of
obtaining analyzing body sounds in accordance with one embodiment
of the invention;
[0045] FIG. 3 shows recording and analysis of signals over an
inspiratory phase of a respiratory cycle; and
[0046] FIG. 4 shows recording and analysis of signals over an
expiratory phase of a respiratory cycle.
DETAILED DESCRIPTION OF THE INVENTION
[0047] FIG. 1 shows a system generally indicated by 100 for
analyzing body sounds in a three-dimensional region of an
individual's body in accordance with one embodiment of the
invention. A plurality of N sound transducers 105, of which four
are shown, are applied to a planar region of the chest or back skin
of individual 110. The transducers 105 may be applied to the
subject by any means is known in the art, for example using an
adhesive, suction, or fastening straps. Each transducer 105
produces an analog voltage signal 115 indicative of pressure waves
arriving to the transducer. The analog signals 115 are digitized by
a multichannel analog to digital converter 120. The digital data
signals P(x.sub.i,t) 125, represent the pressure wave at the
location x.sub.i of the ith transducer (i=1 to N) at time t. The
data signals 125 are input to a memory 130. Data input to the
memory 130 are accessed by a processor 135 configured to process
the data signals 125. The signals 125 may be denoised by filtering
components such having frequencies outside of the range of body
sounds in the body region, for example, vibrations due to movement
of the individual. Each signal 125 may also be subject to band pass
filtering so that only components in the signal within a range of
interest are analyzed.
[0048] An input device such as a computer keyboard 140 or mouse 145
is used to input relevant information relating to the examination
such as personal details of the individual 110. The input device
140 may also be used to input values of the times t.sub.1 and
t.sub.2. Alternatively, the times t.sub.1 and t.sub.2 may be
determined automatically times t.sub.1 and t.sub.2. Alternatively,
the times t.sub.1 and t.sub.2 may be determined automatically in a
respiratory phase analysis of the signals P(x.sub.i,t) performed by
the processor 135. The processor 135 determines an average acoustic
energy {tilde over (P)}(x,t.sub.1,t.sub.2) over the time interval
from t.sub.1 to t.sub.2 at least one location x in the region R in
a calculation involving at least one of the signals
P(x.sub.i,t).
[0049] The average acoustic energies are stored in the memory 130
and may be displayed on a display device 150 such as a CRT screen
for diagnosis by a physician.
[0050] The processor 135 may also perform an automatic differential
diagnosis by comparing the function {tilde over (P)} to functions
stored in the memory and known to be indicative of various
disorders in the body region.
[0051] FIG. 2 shows a flow chart diagram for carrying out the
method of the invention in accordance with one embodiment. In step
200 the signals P(xi,t) are obtained from N transducers placed at
predetermined locations x.sub.i for i from 1 to N in a region R on
the body surface. In step 205 values of t.sub.1 and t.sub.2 are
either input to the processor 135 using the input devices 140 or
145, or are detrmined by the processor. In step 210, an average
acoustic energy {tilde over (P)}(x,t.sub.1,t.sub.2) is determined
at least one location x in the region R over the time interval
t.sub.1 to t.sub.2. In step 220 the average acoustic energy is
displayed on the display 150 for at least one value of x. In step
230, it is determined whether a function {tilde over (P)} is to be
determined over another time interval. If yes, the process returns
to step 205. If not, the process terminates.
[0052] It will also be understood that the system according to the
invention may be a suitably programmed computer. Likewise, the
invention contemplates a computer program being readable by a
computer for executing the method of the invention. The invention
further contemplates a machine-readable memory tangibly embodying a
program of instructions executable by the machine for executing the
method of the invention.
EXAMPLES
[0053] The system and method of the invention were used to analyze
lower respiratory tract sounds in an individual.
[0054] FIG. 3 shows recording and analysis of signals over an
inspiratory phase of a respiratory cycle in an individual. A
two-dimensional coordinate system was defined on the individual's
back. As shown in FIG. 3a, 48 transducers were placed on the
individual's back over the lungs at the locations indicated by the
circles 300. The curves 305 show the presumed contours of the
lungs. As can be seen, the transducers were arranged in a regular
orthogonal lattice with a spacing between the transducers in the
horizontal and vertical directions of 5 cm. The signals P(xi,t)
were then recorded over one inspiratory phase of a breathing cycle
(t.sub.1 and t.sub.2 are the beginning and end respectively of the
inspiratory phase). Each signal was filtered using a low-pass
filter having a cut-off of 150 Hz. The average value of each
filtered function P(xi,t) over the inspiratory phase is indicated
in FIG. 3a by means of gray level shading of each circle 300 with
reference to the gray level scale 310. {tilde over
(P)}(x,t.sub.1,t.sub.2) was obtained using Equations (1) and (2)
above with the kernal g of Equation (5) with .sigma.=36 pixels.
FIG. 3b shows a 512 pixel.times.512 pixel graphical representation
of the function {tilde over (P)}(x,t.sub.1,t.sub.2) over the
inspiratory phase also in reference to the gray level scale 310. In
the graphical representation of the function {tilde over
(P)}(x,t.sub.1,t.sub.2) shown in FIG. 3b, the contours of the lungs
and heart are easily perceived.
[0055] FIG. 4 shows recording and analysis of signals over an
expiratory phase of a respiratory cycle. As shown in FIG. 4a, 48
transducers were placed on an individual's back at the same
locations x.sub.i used in FIG. 3, as indicated by the circles 400.
The curves 405 show the presumed contours of the individual's
lungs. The signals P(xi,t) were then recorded over one expiratory
phase of a breathing cycle (t.sub.1 and t.sub.2 are the beginning
and end respectively of the expiratory phase). Each signal was
filtered using a low-pass filter having a cut-off of 150 Hz. The
average value of each function P(xi,t) over the expiratory phase is
indicated in FIG. 4a by means of gray level shading of each circle
400 with reference to the gray level scale 410. {tilde over
(P)}(x,t.sub.1,t.sub.2) was obtained using Equations (1) and (2)
above. FIG. 3b shows the function {tilde over
(P)}(x,t.sub.1,t.sub.2) over the expiratory phase also in reference
to the gray level scale 410. Comparison of FIGS. 3b and 4b shows
the volume change in acoustic energy between the inspiratory and
expiratory phase of the respiratory cycle.
* * * * *