U.S. patent application number 12/714020 was filed with the patent office on 2011-09-01 for method and apparatus for determining a heart period from an ecg waveform using image representation of ecg.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to TANVEER SYEDA MAHMOOD, FEI WANG.
Application Number | 20110213257 12/714020 |
Document ID | / |
Family ID | 44505652 |
Filed Date | 2011-09-01 |
United States Patent
Application |
20110213257 |
Kind Code |
A1 |
MAHMOOD; TANVEER SYEDA ; et
al. |
September 1, 2011 |
METHOD AND APPARATUS FOR DETERMINING A HEART PERIOD FROM AN ECG
WAVEFORM USING IMAGE REPRESENTATION OF ECG
Abstract
A method and system and computer program product for estimating
a heart period is disclosed. The heart period is detected from an
ECG recording. ECG data is acquired, and converted into electronic
ECG images. The data is processed to prepare for estimation of a
heart period. The heart period is estimated based upon an average
of intervals between a plurality of detected peaks of electronic
electrocardiogram waveforms. The peaks are determined by taking a
product of a filtered electronic ECG signal with a wandering
baseline removed, a difference between the upper and lower ECG
envelopes of the electronic ECG images, and a first order
derivative of a derived ECG waveform.
Inventors: |
MAHMOOD; TANVEER SYEDA;
(Cupertino, CA) ; WANG; FEI; (San Jose,
CA) |
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
Armonk
NY
|
Family ID: |
44505652 |
Appl. No.: |
12/714020 |
Filed: |
February 26, 2010 |
Current U.S.
Class: |
600/509 |
Current CPC
Class: |
A61B 5/0245 20130101;
A61B 5/72 20130101; A61B 5/02 20130101; A61B 5/7239 20130101 |
Class at
Publication: |
600/509 |
International
Class: |
A61B 5/0402 20060101
A61B005/0402 |
Claims
1. A method for estimating a heart period using at least one of a
plurality of electrocardiogram recordings, comprising: utilizing a
computer processor to convert a plurality of the electrocardiogram
recordings into a plurality of corresponding electronic
electrocardiogram images; deriving an electrocardiogram waveform
from one of the electronic electrocardiogram images by extracting
an upper envelope and a lower envelope of the electrocardiogram
waveform from the corresponding electronic electrocardiogram image
using a curve tracing algorithm; determining an electrocardiogram
signal peak from increased thickness at the electrocardiogram
signal peak due to pixel dithering; determining a difference
between the upper envelope and the lower envelope at the
electrocardiogram signal peak and at an electrocardiogram low
point, which are a local maximum and a local minimum of one of the
corresponding electronic electrocardiogram images; and estimating
the heart period.
2. The method of claim 1, wherein the algorithm for extracting the
upper envelope and lower envelope comprises: tracing upper and
lower edges of a curve of the electrocardiogram waveform from one
of the electronic electrocardiogram images; defining two search
ranges centered around the upper and lower edges of the curve of
the electrocardiogram waveform; using at least one of: a
morphological open algorithm to fill in holes inside the curve of
the electrocardiogram waveform and a morphological close algorithm
to eliminate noise pixels near the curve of the electrocardiogram
waveform; closing small gaps by closing the electrocardiogram
waveform between inserted seed points along an expected location of
the derived electrocardiogram waveform; and closing large gaps by
inserting a segment tangent to the curve of the electrocardiogram
waveform.
3. The method of claim 2, wherein estimating the heart period
comprises: computing a first order derivative of the derived
electrocardiogram waveform for amplifying high frequencies of the
derived electrocardiogram waveform; determining a peak of the
derived electrocardiogram waveform by taking a product of a
filtered electrocardiogram signal from one of the corresponding
electronic electrocardiogram images, with a wandering baseline
removed, a difference between the upper envelope and the lower
envelope of the derived electrocardiogram waveform from each of the
at least one of the corresponding electronic electrocardiogram
images and the first order derivative of the derived
electrocardiogram waveform; and determining an average of intervals
between a plurality of detected peaks of the electrocardiogram
waveform from at least one region selected from the electronic
electrocardiogram image.
4. The method of claim 3, further comprising obtaining the
plurality of electrocardiogram recordings generated from a
plurality of electrocardiogram sources.
5. The method of claim 4, further comprising removing noise from
the corresponding electronic electrocardiogram images.
6. The method of claim 5, further comprising outputting the
determined heart period on a display.
7. The method of claim 6, wherein at least one of the
electrocardiogram sources comprises a paper form electrocardiogram
source.
8. The method of claim 7, further comprising scanning the paper
form of said electrocardiogram source into at least one electronic
electrocardiogram image.
9. The method of claim 6, wherein at least one of the
electrocardiogram sources comprises a digital form
electrocardiogram source.
10. The method of claim 6, wherein at least one of the
electrocardiogram sources comprises an echocardiogram from an
echocardiogram source.
11. A system for estimating a heart period using at least one of a
plurality of electrocardiogram recordings, comprising: a conversion
machine for converting an at least one electrocardiogram recording
into a corresponding electronic electrocardiogram image; a
derivation machine for: deriving an electrocardiogram waveform from
the corresponding electronic electrocardiogram image, by extracting
an upper envelope and a lower envelope of the derived
electrocardiogram waveform from the electronic electrocardiogram
image using a curve tracing algorithm; determining an
electrocardiogram signal peak from increased thickness at the
electrocardiogram signal peak due to pixel dithering; and
determining the difference between the upper envelope and the lower
envelope at the electrocardiogram signal peak and at an
electrocardiogram low point, which are a local maximum and a local
minimum of the derived electrocardiogram waveform from the
corresponding electronic electrocardiogram image; and an estimation
machine for: computing a first order derivative of the derived
electrocardiogram waveform for amplifying high frequencies of the
derived electrocardiogram waveform; determining a peak of the
derived electrocardiogram waveform by taking a product of a
filtered electrocardiogram signal from the corresponding electronic
electrocardiogram image in which a wandering baseline has been
removed, a difference between the upper envelope and the lower
envelope of the derived electrocardiogram waveform in the
corresponding electronic electrocardiogram image and the first
order derivative of the derived electrocardiogram waveform; and
estimating the heart period as an average of intervals between a
plurality of detected peaks from the at least one simultaneously
selected region from each of the plurality of electronic
electrocardiogram images and from the derived electrocardiogram
waveform.
12. The system of claim 11, wherein the algorithm for extracting
the upper envelope and lower envelope comprises: tracing upper and
lower edges of a curve of the electrocardiogram waveform from one
of the electronic electrocardiogram images; defining two search
ranges centered around the upper and lower edges of the curve of
the electrocardiogram waveform; using at least one of: a
morphological open algorithm to fill in holes inside the curve of
the electrocardiogram waveform and a morphological close algorithm
to eliminate noise pixels near the curve of the electrocardiogram
waveform; closing small gaps by closing the electrocardiogram
waveform between inserted seed points along an expected location of
the derived electrocardiogram waveform; and closing large gaps by
inserting a segment tangent to the curve of the electrocardiogram
waveform.
13. The system of claim 12, further comprising an electrocardiogram
machine coupled to the conversion machine and utilizing a computer
processor to obtain at least one of the plurality of
electrocardiogram recordings generated from at least one of a
plurality electrocardiogram sources.
14. The system of claim 13, further comprising a de-noising machine
coupled to the conversion machine and for removing noise from the
corresponding electronic electrocardiogram image.
15. The system of claim 14, further comprising a display coupled to
the estimation machine and for outputting the estimated heart
period.
16. The system of claim 15, wherein at least one of the
electrocardiogram sources comprises a paper form electrocardiogram
source.
17. The system of claim 15, wherein at least one of the
electrocardiogram sources comprises a digital form
electrocardiogram source.
18. The system of claim 15, wherein at least one of the
electrocardiogram sources comprises an echocardiogram from an
echocardiogram source.
19. The system of claim 16, wherein the conversion machine scans
the paper form electrocardiogram source into at least one
electronic electrocardiogram image.
20. A processor implemented computer program product for estimating
a heart period using at least one of a plurality of
electrocardiogram recordings, comprising: computer program code
performing on a computer processor in an electrocardiogram machine
measuring electrical activity of a heart for: obtaining at least
one of a plurality of electrocardiogram recordings generated from
at least one of a plurality of electrocardiogram sources;
converting at least one electrocardiogram recording into a
corresponding electronic electrocardiogram image; removing noise
from the corresponding electronic electrocardiogram image; deriving
an electrocardiogram waveform from the corresponding electronic
electrocardiogram image, by extracting an upper envelope and a
lower envelope of the derived electrocardiogram waveform from the
electronic electrocardiogram image using a curve tracing algorithm,
the algorithm for extracting the upper envelope and lower envelope
comprising: tracing upper and lower edges of a curve of the
electrocardiogram waveform from the corresponding electronic
electrocardiogram image; defining two search ranges centered around
the upper and lower edges of the curve of the electrocardiogram
waveform; using a morphological open algorithm to fill in holes
inside the curve of the electrocardiogram waveform; using a
morphological close algorithm to eliminate noise pixels near the
curve of the electrocardiogram waveform; closing small gaps by
closing the derived electrocardiogram waveform between inserted
seed points along an expected location of the electrocardiogram
waveform; and closing large gaps by inserting a segment tangent to
the curve of the electrocardiogram waveform; and determining an
electrocardiogram signal peak from increased thickness at the
electrocardiogram signal peak due to pixel dithering; determining a
difference between the upper envelope and the lower envelope at the
electrocardiogram signal peak and at an electrocardiogram low point
which are a local maximum and a local minimum of the derived
electrocardiogram waveform from the corresponding electronic
electrocardiogram image; estimating the heart period, by computing
a first order derivative of the derived electrocardiogram waveform
for amplifying high frequencies of the derived electrocardiogram
waveform; determining a peak of the derived electrocardiogram
waveform by taking a product of a filtered electrocardiogram signal
from the corresponding electronic electrocardiogram image with a
wandering baseline removed, the difference between the upper
envelope and the lower envelope of the derived electrocardiogram
waveform in the corresponding electronic electrocardiogram image,
and the first order derivative of the derived electrocardiogram
waveform; and estimating the heart period, as an average of
intervals between a plurality of detected peaks from the derived
electrocardiogram waveform; and outputting the estimated heart
period on a user interface display.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to the field of
electrocardiograms (ECG), and more specifically, automatic
processing of electrocardiograms.
[0002] There has been an increased need for automatic processing of
the electrocardiogram (ECG). Many systems have been developed to
perform signal processing tasks such as 12-lead off-line ECG
analysis, and real-time patient monitoring. These applications
require an accurate detection of the heart rate by the ECG.
[0003] Although many hospitals now have digital ECG records, much
of the ECG data is in paper form. Unlocking these ECG records
printed on paper and exposing them to digital analysis would be
useful.
[0004] Digital ECG recordings are sampled finely, and contain noisy
data with baseline wandering problems. The heart beats that
illustrate a disease may be carefully screened by technicians
before taking the recording, so that the paper version may show
only a few seconds of data needed for diagnosis.
[0005] While it is difficult to estimate the heart cycle directly
from a depicted heart region in a video, it is relatively easy to
estimate the heart rate from a synchronizing ECG.
[0006] Hence, there is a need for a method and apparatus for
determining a heart period using image representation obtained from
an ECG.
SUMMARY OF THE INVENTION
[0007] In one aspect of the invention, a method for estimating a
heart period using at least one of a plurality of electrocardiogram
recordings is disclosed. The method comprises utilizing a computer
processor to obtain the plurality of electrocardiogram recordings
generated from a plurality of electrocardiogram sources; converting
the plurality of the electrocardiogram recordings into a plurality
of corresponding electronic electrocardiogram images; removing
noise from the corresponding electronic electrocardiogram images;
deriving an electrocardiogram waveform from one of the electronic
electrocardiogram images by extracting an upper envelope and a
lower envelope of the electrocardiogram waveform from the
corresponding electronic electrocardiogram image using a curve
tracing algorithm, the algorithm for extracting the upper envelope
and lower envelope comprising: tracing upper and lower edges of a
curve of the electrocardiogram waveform from one of the electronic
electrocardiogram images; defining two search ranges centered
around the upper and lower edges of the curve of the
electrocardiogram waveform; using at least one of: a morphological
open algorithm to fill in holes inside the curve of the
electrocardiogram waveform and a morphological close algorithm to
eliminate noise pixels near the curve of the electrocardiogram
waveform; closing small gaps by closing the electrocardiogram
waveform between inserted seed points along an expected location of
the electrocardiogram waveform; and closing large gaps by inserting
a segment tangent to the curve of the electrocardiogram waveform;
determining an electrocardiogram signal peak from increased
thickness at the electrocardiogram signal peak due to pixel
dithering; determining a difference between the upper envelope and
the lower envelope at the electrocardiogram signal peak and at an
electrocardiogram low point, which represent a local maximum and a
local minimum of one of the corresponding electronic
electrocardiogram images; estimating the heart period by: computing
a first order derivative of the derived electrocardiogram waveform
for amplifying high frequencies of the derived electrocardiogram
waveform; determining a peak of the derived electrocardiogram
waveform by taking a product of a filtered electrocardiogram signal
from one of the corresponding electronic electrocardiogram images,
with a wandering baseline removed, a difference between the upper
envelope and the lower envelope of the derived electrocardiogram
waveform from each of the at least one of the corresponding
electronic electrocardiogram images and the first order derivative
of the derived electrocardiogram waveform; and determining an
average of intervals between a plurality of detected peaks from at
least one region selected from the derived electrocardiogram
waveform; and outputting the determined heart period on a user
interface display.
[0008] In another aspect, a system for estimating a heart period
using at least one of a plurality of electrocardiogram recordings
is disclosed. The system comprises an electrocardiogram machine
utilizing a computer processor to obtain at least one of the
plurality of electrocardiogram recordings generated from at least
one of a plurality electrocardiogram sources; a conversion machine
for converting said at least one electrocardiogram recording into a
corresponding electronic electrocardiogram image; a de-noising
machine for removing noise from the corresponding electronic
electrocardiogram image; a derivation machine for deriving an
electrocardiogram waveform from the corresponding electronic
electrocardiogram image, by extracting an upper envelope and a
lower envelope of the derived electrocardiogram waveform from the
electronic electrocardiogram image using a curve tracing algorithm,
the algorithm for extracting the upper envelope and lower envelope
comprising: tracing upper and lower edges of a curve of the
electrocardiogram waveform from the corresponding electronic
electrocardiogram image; defining two search ranges centered around
the upper and lower edges of the curve of the electrocardiogram
waveform; using a morphological open algorithm to fill in holes
inside the curve of the electrocardiogram waveform; using a
morphological close algorithm to eliminate noise pixels near the
curve of the electrocardiogram waveform; closing small gaps by
closing the electrocardiogram waveform between inserted seed points
along an expected location of the electrocardiogram waveform; and
closing large gaps by inserting a segment tangent to the curve of
the electrocardiogram waveform; the derivation machine further
determining an electrocardiogram signal peak from increased
thickness at the electrocardiogram signal peak due to pixel
dithering; the derivation machine further determining the
difference between the upper envelope and the lower envelope at the
electrocardiogram signal peak and at an electrocardiogram low
point, which are a local maximum and a local minimum of the derived
electrocardiogram waveform from the corresponding electronic
electrocardiogram image; an estimation machine for: computing a
first order derivative of the derived electrocardiogram waveform
for amplifying high frequencies of the derived electrocardiogram
waveform; determining a peak of the derived electrocardiogram
waveform by taking a product of a filtered electrocardiogram signal
from the corresponding electronic electrocardiogram image in which
a wandering baseline has been removed, a difference between the
upper envelope and the lower envelope of the derived
electrocardiogram waveform in the corresponding electronic
electrocardiogram image and the first order derivative of the
derived electrocardiogram waveform; and estimating the heart period
as an average of intervals between a plurality of detected peaks
from the at least one simultaneously selected region from each of
the plurality of electronic electrocardiogram images and from the
derived electrocardiogram waveform; and a user interface display
for outputting the estimated heart period.
[0009] In a further aspect, a processor implemented computer
program product for estimating a heart period using at least one of
a plurality of electrocardiogram recordings is disclosed. The
computer program product comprises: computer program code
performing on a computer processor in an electrocardiogram machine
measuring electrical activity of a heart for: obtaining at least
one of a plurality of electrocardiogram recordings generated from
at least one of a plurality of electrocardiogram sources;
converting at least one electrocardiogram recording into a
corresponding electronic electrocardiogram image; removing noise
from the corresponding electronic electrocardiogram image; deriving
an electrocardiogram waveform from the corresponding electronic
electrocardiogram image, by extracting an upper envelope and a
lower envelope of the derived electrocardiogram waveform from the
electronic electrocardiogram image using a curve tracing algorithm,
the algorithm for extracting the upper envelope and lower envelope
comprising: tracing upper and lower edges of a curve of the
electrocardiogram waveform from the corresponding electronic
electrocardiogram image; defining two search ranges centered around
the upper and lower edges of the curve of the electrocardiogram
waveform; using a morphological open algorithm to fill in holes
inside the curve of the electrocardiogram waveform; using a
morphological close algorithm to eliminate noise pixels near the
curve of the electrocardiogram waveform; closing small gaps by
closing the electrocardiogram waveform between inserted seed points
along an expected location of the electrocardiogram waveform; and
closing large gaps by inserting a segment tangent to the curve of
the electrocardiogram waveform; and determining an
electrocardiogram signal peak from increased thickness at the
electrocardiogram signal peak due to pixel dithering; determining a
difference between the upper envelope and the lower envelope at the
electrocardiogram signal peak and at an electrocardiogram low point
which are a local maximum and a local minimum of the derived
electrocardiogram waveform from the corresponding electronic
electrocardiogram image; estimating the heart period, by: computing
a first order derivative of the derived electrocardiogram waveform
for amplifying high frequencies of the derived electrocardiogram
waveform; determining a peak of the derived electrocardiogram
waveform by taking a product of a filtered electrocardiogram signal
from the corresponding electronic electrocardiogram image with a
wandering baseline removed, the difference between the upper
envelope and the lower envelope of the derived electrocardiogram
waveform in the corresponding electronic electrocardiogram image,
and the first order derivative of the derived electrocardiogram
waveform; and estimating the heart period, as an average of
intervals between a plurality of detected peaks from the derived
electrocardiogram waveform; and outputting the estimated heart
period on a user interface display.
[0010] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following drawings, description and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a block diagram of a system according to one
exemplary embodiment of the invention;
[0012] FIG. 2 is a flowchart of an exemplary embodiment of the
invention.
[0013] FIG. 3 is a flowchart of an algorithm for extracting upper
and lower envelopes of ECG waveforms from electronic ECG images
according to an exemplary embodiment of the invention.
[0014] FIG. 4 is a synthetic ECG image generated from a 12-channel
digital ECG waveform according to an exemplary embodiment of the
invention; and
[0015] FIG. 5 shows ECG waveforms according to an exemplary
embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The following detailed description is of the best currently
contemplated modes of carrying out the invention. The description
is not to be taken in a limiting sense, but is made merely for the
purpose of illustrating the general principles of the invention,
since the scope of the invention is best defined by the appended
claims.
[0017] The present invention may estimate a heart period based on
an image representation of an ECG waveform. It may be used, for
example, in diagnosing arrhythmia patients.
[0018] The present invention differs from the prior art in using
images for detecting periodicity in ECG waveforms. The invention
transforms all ECG information into images, and uses the waveform
images to determine heartbeat periodicity.
[0019] Various inventive features are described below that can each
be used independently of one another or in combination with other
features. However, any single inventive feature may not address any
of the problems discussed above or may only address one of the
problems discussed above. Further, one or more of the problems
discussed above may not be fully addressed by any of the features
described below.
[0020] As will be appreciated by one skilled in the art, exemplary
embodiments of the present invention may be embodied as a system,
method or computer program product. Accordingly, exemplary
embodiments of the present invention may take the form of an
entirely hardware embodiment, an entirely software embodiment
(including firmware, resident software, micro-code, etc.) or an
embodiment combining software and hardware aspects that may all
generally be referred to herein as a "circuit," "module" or
"system." Furthermore, the present invention may take the form of a
computer program product embodied in any tangible medium of
expression having computer-usable program code embodied in the
medium.
[0021] Any combination of one or more computer usable or computer
readable medium(s) may be utilized. The computer-usable or
computer-readable medium may be, for example but not limited to, an
electronic, magnetic, optical, electromagnetic, infrared, or
semiconductor system, apparatus, device, or propagation medium.
More specific examples (a non-exhaustive list) of the
computer-readable medium would include the following: an electrical
connection having one or more wires, a portable computer diskette,
a hard disk, a random access memory (RAM), a read-only memory
(ROM), an erasable programmable read-only memory (EPROM or Flash
memory), an optical fiber, a portable compact disc read-only memory
(CDROM), an optical storage device, a transmission media such as
those supporting the Internet or an intranet, or a magnetic storage
device. Note that the computer-usable or computer-readable medium
could even be paper or another suitable medium upon which the
program is printed, as the program can be electronically captured,
via, for instance, optical scanning of the paper or other medium,
then compiled, interpreted, or otherwise processed in a suitable
manner, if necessary, and then stored in a computer memory. In the
context of this document, a computer-usable or computer-readable
medium may be any medium that can contain, store, communicate,
propagate, or transport the program for use by or in connection
with the instruction performing system, apparatus, or device. The
computer-usable medium may include a propagated data signal with
the computer-usable program code embodied therewith, either in
baseband or as part of a carrier wave. The computer usable program
code may be transmitted using any appropriate medium, including but
not limited to wireless, wireline, optical fiber cable, RF,
etc.
[0022] Computer program code for carrying out operations of the
present invention may be written in any combination of one or more
programming languages, including an object oriented programming
language such as JAVA (JAVA is a registered trademark of Sun
Microsystems), Smalltalk.TM., C++ or the like and conventional
procedural programming languages, such as the "C" programming
language or similar programming languages. The program code may
perform entirely on the user's computer, partly on the user's
computer, as a stand-alone software package, partly on the user's
computer and partly on a remote computer or entirely on the remote
computer or server. In the latter scenario, the remote computer may
be connected to the user's computer through any type of network,
including a local area network (LAN) or a wide area network (WAN),
or the connection may be made to an external computer (for example,
through the Internet using an Internet Service Provider).
[0023] Exemplary embodiments of the present invention is described
below with reference to flowchart illustrations and/or block
diagrams of methods, apparatus (systems) and computer program
products according to embodiments of the invention. It will be
understood that each block of the flowchart illustrations and/or
block diagrams, and combinations of blocks in the flowchart
illustrations and/or block diagrams, can be implemented by computer
program instructions. These computer program instructions may be
provided to a processor of a general purpose computer, special
purpose computer, or other programmable data processing apparatus
to produce a machine, such that the instructions, which perform via
the processor of the computer or other programmable data processing
apparatus, create means for implementing the functions/acts
specified in the flowchart and/or block diagram block or
blocks.
[0024] These computer program instructions may also be stored in a
computer-readable medium that can direct a computer or other
programmable data processing apparatus to function in a particular
manner, such that the instructions stored in the computer-readable
medium produce an article of manufacture including instruction
means which implement the function/act specified in the flowchart
and/or block diagram block or blocks.
[0025] The computer program instructions may also be loaded onto a
computer or other programmable data processing apparatus to cause a
series of operational steps to be performed on the computer or
other programmable apparatus to produce a computer implemented
process such that the instructions which perform on the computer or
other programmable apparatus provide processes for implementing the
functions/acts specified in the flowchart and/or block diagram
block or blocks.
[0026] Exemplary embodiments of the present invention are related
to techniques for a method and apparatus for determining a heart
period using image representation obtained from an ECG.
[0027] FIG. 1 is a block diagram of a system 100 for estimating a
heart period using a plurality of electrocardiogram recordings
according to an exemplary embodiment of the invention. The system
100 may include an Electrocardiogram Machine 110, a Conversion
Machine 120, a De-noising Machine 130, a Derivation Machine 140, an
Estimator Machine 150, a memory 160, a keyboard and a mouse input
170, and a user interface display, such as a computer monitor
180.
[0028] An electrocardiogram machine 110 may utilize a computer
processor to obtain a plurality of electrocardiogram recordings
generated from a plurality of electrocardiogram sources. In one
case, the user may utilize the invention by receiving
electrocardiogram recordings 115 from an electrocardiogram machine
110 and inputting them into a conversion machine 120. The
conversion machine 120 may be a scanner for converting paper
electrocardiogram recordings into electronic electrocardiogram
image form. The conversion machine 120 may also be an electronic
converter for converting the paper electrocardiogram from the
electrocardiogram machine 110 into an electronic image for display
on a computer monitor 180. The conversion machine 120 may further
convert the digital electrocardiogram waveforms into corresponding
electronic electrocardiogram images. The conversion machine 120 may
further remove a wandering baseline from these digital ECG
waveforms. A wandering baseline, as is known in the art is a signal
pattern that wanders across a screen, which may be caused by
unsatisfactory electrode connections. The conversion machine 120
may further comprise a converter for converting an echocardiogram
into an electronic electrocardiogram using electrocardiogram
regions of interest detection.
[0029] The De-noising machine 130 may remove noise from the
electronic electrocardiogram images.
[0030] The Derivation machine 140 may derive an electrocardiogram
waveform by extracting an upper envelope and a lower envelope of
the electrocardiogram waveform from the electronic
electrocardiogram images using a curve tracing algorithm described
in more detail below. A difference between the upper envelope and
the lower envelope of an electrocardiogram waveform from a selected
region of an electronic ECG image may signify a local maximum and a
local minimum of the electrocardiogram waveform from one of the
corresponding electronic electrocardiogram images.
[0031] The Derivation machine may further determine an
electrocardiogram signal peak from increased thickness at the
electrocardiogram signal peak due to pixel dithering. The
difference between the upper envelope and the lower envelope may
increase at an electrocardiogram signal peak, and at an
electrocardiogram low point.
[0032] The estimation machine 150 may estimate the heart period,
and a user may use a keyboard or a mouse 170 to output the
estimated heart period on a computer monitor 180. The estimated
heart period may be stored in memory 160.
[0033] FIG. 2 shows a flowchart 200 of an exemplary embodiment of
the invention. As shown in FIG. 2, when an ECG is entered in paper
form 205, the paper form may be scanned using processing contained
in box 220 into a recording which is converted into a digital
(electronic) ECG image. For already existing ECG recordings 210, a
wandering baseline may be removed from these digital ECG waveforms
(as shown at block 225) before they are synthetically converted
into an electronic ECG image by processing contained in box 232.
FIG. 4 shows a synthetic ECG image that may be generated from a
12-channel ECG recording. Each channel may be 300 pixels wide in
the recording.
[0034] For echocardiographic (ECHO ECG) frames 215, they are
already in suitable electronic ECG image form and no conversion is
necessary.
[0035] From the electronic ECG, at least one region of interest
(ROI) of an electronic ECG image may be selected. Then, the
selected region of interest may be extracted as shown at block
230.
[0036] At block 235, a step of extracting upper and lower envelopes
of an ECG waveform from the selected region of interest of the
electronic ECG image may occur.
[0037] As shown at block 242, determining an electrocardiogram
signal peak from increased thickness at the electrocardiogram
signal peak due to pixel dithering may occur. As shown at block
245, the difference of the upper envelope and the lower envelope of
the ECG waveform from the electronic ECG image can signify the
local maximum and minimum of the ECG waveform in the electronic ECG
image. The gap between the two envelopes may increase significantly
when the signal reaches a peak or valley.
[0038] Determination of the upper and lower envelopes may be
performed, for example, via curve tracing algorithm as shown in
FIG. 3. The curve tracing algorithm may initially trace the upper
and lower edges of a curve of the ECG waveform in a ECG recording
as shown at block 310. The upper edge of the curve may be denoted
by y.sub.u(x), and the lower edge of the curve may be denoted by
y.sub.l(x).
[0039] As shown at block 320, two search ranges may be defined,
centered around the upper and lower edges of the electrocardiogram
waveform. These values may be designated by:
R.sub.u=[y.sub.u(x-1)+W, y.sub.u(x-1)+W];
R.sub.l=[y.sub.l(x-1)+W, y.sub.l(x-1)+W];
where R.sub.u may represent a search range for the upper edge and
R.sub.l may represent a search range of the lower edge of the
electrocardiogram waveform; and W may represent a search
window.
[0040] As shown at block 330, a morphological open (erode+dilate)
algorithm may be used to fill in holes inside the curve of the ECG
waveform. In the morphological open algorithm, the image of the
electronic ECG is first shrunk, then the image region is enlarged.
As shown at block 340, a morphological close algorithm may be used
to eliminate noise pixels near the curve of the ECG waveform. In
the morphological close algorithm, the image of the electronic ECG
is first enlarged, then shrunk. As shown at block 350, small gaps
may be closed in the ECG waveform between inserted seed points
along an expected location of the electrocardiogram waveform. As
shown at block 360, large gaps in the ECG waveform may be closed by
inserting a segment tangent to the curve of the electrocardiogram
waveform;
[0041] The upper and lower envelopes may be denoted as f.sub.u and
f.sub.l respectively, and ECG waveforms can be derived as the
average between the two, i.e., f=(f.sub.u+f.sub.l)/2. The
difference between the two envelopes may be
f.sub.diff=f.sub.u-f.sub.l.
[0042] As shown in FIG. 2 at block 255, in order to determine a
peak of an ECG waveform, a signal product may be determined as a
product of the filtered electronic ECG image in which a wandering
baseline is removed 240, a difference between the upper envelope
and the lower envelope 245, and a first derivative of a an ECG
waveform signal 250. Then, as shown at block 265, a heart period
may be estimated from an average of several intervals between
peaks.
[0043] FIG. 5 shows ECG waveform signals from electronic ECG images
according to an exemplary embodiment of the invention. Block 510
may depict a conventional ECG recording, whether on paper or in
digital form. After conversion to electronic form and extraction of
upper and lower envelopes of the ECG waveform from the electronic
ECG image, an exemplary embodiment of the invention may take the
product 560 of three factors to estimate a heart period. The first
factor may be a normalized, filtered electronic ECG image in which
a wandering baseline has been removed, as shown at block 520. The
second factor may be the difference between upper and lower
envelopes of the ECG waveform, as shown at block 530. Block 540
shows signals for upper and lower envelopes. An exemplary upper
envelope is indicated as graph 542, and an exemplary lower envelope
is indicated as graph 544 in block 540. The third factor may be a
first order derivative of the ECG waveform, as shown at block 550.
A peak of an ECG waveform from an electronic ECG image may be
determined from the product 560 of the three factors. The use of a
first order derivative of the ECG waveform is advantageous as it
may amplify the higher frequencies while attenuating the lower
product of the three waveforms.
[0044] The signal product may be shown at block 560, and may be
expressed as: S=f*f'*f.sub.diff, where f may be a normalized ECG
waveform in which a wandering baseline has been removed, f' may be
the first order ECG derivative of the curve of the ECG waveform,
which has been derived from the electronic ECG image, and
f.sub.diff may denote the envelope difference between the upper and
lower envelopes of the ECG waveform extracted from the electronic
ECG image. Intervals between peaks may next be determined from a
plurality of selected regions of electrocardiogram waveforms in
electronic ECG images and the period of the ECG waveform in the
electronic ECG image can be estimated as an average of intervals
between these peaks.
[0045] The flowchart and block diagrams in the Figures illustrate
the architecture, functionality, and operation of possible
implementations of systems, methods and computer program products
according to various embodiments of the present invention. In this
regard, each block in the flowchart or block diagrams may represent
a module, segment, or portion of code, which comprises one or more
performable instructions for implementing the specified logical
function(s). It should also be noted that, in some alternative
implementations, the functions noted in the block may occur out of
the order noted in the figures. For example, two blocks shown in
succession may, in fact, be performed substantially concurrently,
or the blocks may sometimes be performed in the reverse order,
depending upon the functionality involved. It will also be noted
that each block of the block diagrams and/or flowchart
illustration, and combinations of blocks in the block diagrams
and/or flowchart illustration, may be implemented by special
purpose hardware-based systems that perform the specified functions
or acts, or combinations of special purpose hardware and computer
instructions.
[0046] It should be understood, of course, that the foregoing
relates to exemplary embodiments of the invention and that
modifications may be made without departing from the spirit and
scope of the invention as set forth in the following claims.
* * * * *