111111
`
`1111111111111111111111111111111111111111111111111111111111111111111111111111
`US 20030236647Al
`
`(19) United States
`(12) Patent Application Publication
`Yoon ct aJ.
`
`(10) J>ub. No.: US 2003/0236647 Al
`Dec. 25, 2003
`(43) J>ub. Date:
`
`(54) DIAGNOSTIC M ETHOD ANO APPARATUS
`USl NC LICHT
`
`(76)
`
`Inventors: G il-woo Yooo, Seoul (KR); Hoog-sig
`Kim, Seongnam-city (KR); Kye-jin
`Jco n, Suwoo-city (KR); Joog-youn
`Lee, Yongin-city (KR); Kun-kook
`Park, Yongio-city (KR); Su-jin Kim,
`Daejeon (KR); Hoon-jong Jwa, Seoul
`(KR)
`
`Correspondence Address:
`LEE & STERBA, t>.c.
`1101 Wilson Boulevard, Suite 2000
`Arlington, VA 22209 (US)
`
`(2J) Appl. No.:
`
`10/387,552
`
`(22) Filed:
`
`Mllr. 14, 2003
`
`(30)
`
`Foreign Application Priority Datil
`
`Mar. 16, 2002
`
`(KR) ....................................... 2002-14277
`
`Publication C lassification
`
`Int. C l.7
`..................................................... G06F 15/ 00
`(51)
`(52) U.S. C l. . ............................................. 702/183; 702/19
`
`(57)
`
`ABSTRACT
`
`A diagnosis method and apparatus for measuring blood
`hemoglobin concentration, oxygen saturation, pulse rate,
`respiration rate, or degree of aging of blood vessels using
`light includes an inpul/output un it for receiving a command
`for measurement from a user and for providing information
`on the resu lt o r a measuremen t to the user; a control unit for
`receiving the command for measurement from the input/
`output uni t and for generating a control signal; a light
`generating un it lor generating at least two light beams lor
`measurement accordi ng to the comrol signal; a light receiv(cid:173)
`ing un it for receiving the light beams transmitted through an
`object that is subject to measurement and for converting the
`received light beams into electrical signals; and a data
`processing unit for processing the electrical signals received
`from the light receiving unit and for outputting information
`on the result of a predetermined measurement.
`
`./ 101
`INPUT
`/OUTPUT
`UNIT
`
`./ 10/
`
`CONTROL
`UNIT
`
`L_ 105
`
`DATA
`PROCESSING
`UNIT
`
`./ 103
`LIGHT
`GENERATING
`UNIT
`.JJ,.
`~ ----
`
`.JJ,. 104
`./
`LIGHT
`RECEIVING
`UNIT
`
`OBJECT TO
`BE MEASURED
`
`Apple Inc.
`APL1015
`U.S. Patent No. 8,942,776
`
`001
`
`

`

`Patent Application Publication Dec. 25, 2003 Sheet 1 of 9
`
`US 2003/0236647 Al
`
`FIG. 1
`
`/ 101
`INPUT
`/OUTPUT
`UNIT
`
`/ 102 -
`
`CONTROL
`UNIT
`
`/105
`DATA
`PROCESSING
`UNIT
`
`FIG. 2
`
`/ 103
`LIGHT
`GENERATING
`UNIT
`.JJ,
`~ -- - -
`
`.JJ, 104
`/
`LIGHT
`RECEIVING
`UNIT
`
`OBJECT TO
`BE MEASURED
`
`103
`r----- -- - - ----- - - --- - -~ -- ---- - ---- - --- -- -- -,
`202
`201
`203
`:
`I
`L
`L
`/
`I
`I
`I
`LIGHT
`LED
`I
`I
`I
`DRIVER
`RADIATOR
`I
`I
`I
`I
`I
`I
`Jl
`I
`I
`L - - - -- --- -- ---- - - --- ------------ - - - -- {Y-- - --~
`
`DAC
`
`LIGHT
`
`FIG. 3
`
`LIGHT
`104
`- ---- ,
`--- -·-- - -- - - --- - ______ L ___ --------- -
`~
`301 I
`302
`303
`I
`I
`:
`I
`I
`I
`I
`I
`I
`L --- - -- -------- - -- -- ----- -- --- - - - - ------- - --~
`
`PHOTO
`DETECTOR
`
`I
`I
`I
`
`ADC
`
`LPF
`
`002
`
`

`

`Patent Application Publication Dec. 25, 2003 Sheet 2 of 9
`
`US 2003/0236647 Al
`
`FIG. 4
`
`105
`r--- ------- ------ ---- ----~---- ----~-- - - --- -------1
`402
`I
`I
`L401
`/
`I
`HEMOGLOBIN
`I
`RATIO
`I
`CONCENTRATION AND
`I
`CALCULATION
`I
`OXYGEN SATURATION
`I
`PORTION
`I
`CALCU LATION PORTION
`I
`I
`I
`I
`I
`I
`I
`
`/406
`
`I
`I
`
`r---
`
`/403
`PULSE RATE
`CALCULATION
`PORTION
`
`'
`
`DATA STORAGE
`PORTION
`
`.,...___
`
`L40t1
`RESPIRATION RATE
`CALCULATION
`PORTION
`
`/405
`OOA
`~ CALCULATION
`PORTION
`I L------------------------------------------------
`
`003
`
`

`

`Patent Application Publication Dec. 25, 2003 Sheet 3 of 9
`
`US 2003/0236647 Al
`
`FIG. 5
`
`PTG
`
`SOPTG
`
`b
`
`004
`
`

`

`Patent Application Publication Dec. 25, 2003 Sheet 4 of 9
`
`US 2003/0236647 At
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`

`

`Patent Application Publication Dec. 25, 2003 Sheet 5 of 9
`
`US 2003/0236647 Al
`
`FIG. 7
`
`( START
`
`RECEIVE COMMAND
`TO MEASURE FROM USER
`
`1- 701
`
`GENERATE AT LEAST TWO
`LIGHT BEAMS HAVING
`DIFFERENT WAVELENGTHS
`BY DRIVING LED
`
`t- 702
`
`RADIATE GENERATED LIGHT
`BEAMS INTO OBJECT
`SUBJECT TO MEASURE MENT
`
`f- 703
`
`RECEIVE LIGHT BEAMS
`TRANSMITTED THROUGH OBJECT
`
`1- 704
`
`/706
`CALCULATE PULSE RATE AND
`RESPIRATION RATE
`
`1 /707
`CALCULATE
`DEGREE OF
`AGING OF BLOOD
`VESSELS
`I
`
`t- 708
`
`- S
`
`TORE CALCULATED RESU LT
`AND PROVIDE IT TO USER
`
`( END
`
`705--....
`
`I
`CALCULATE
`HEMOGLOBIN
`CONCENTRATION
`AND OXYGEN
`SATURATION
`I
`
`006
`
`

`

`Patent Application Publication Dec. 25, 2003 Sheet 6 of 9
`
`US 2003/0236647 Al
`
`FIG. 8
`
`START
`
`'
`
`SELECT AT LEAST TWO ISOBESTIC
`WAVELENGTHS FROM A RANGE OF
`WAVELENGTHS IN WHICH THE EXTINCTION
`COEFFICIENT FOR WATER IS SMALLER
`THAN THAT FOR HEMOGLOBIN
`
`SEQUENTIALLY RADIATE LIGHT BEAMS
`HAVJNG SELECTED WAVELENGTHS
`INTO A SITE OF THE BODY
`
`RECEIVE TRANSMITTED LIGHT BEAMS AND
`CONVERT THEM INTO ELECTRICAL SIGNALS
`
`CALCULATE LIGHT ATIENUATION
`VARIATION FOR EACH WAVELENGTH
`
`f-- 801
`
`- 802
`
`f--
`
`803
`
`f--
`
`804
`
`'
`'
`'
`'
`'
`'
`' END
`
`CALCULATE AT LEAST ONE RATIO
`BETWEEN LIGHT ATTENUATION VARIATIONS 1-- 805
`
`CALCULATE HEMOGLOBIN CONCENTRATION -
`USING LIGHT ATTENUATION VARIATION RATIO
`
`806
`
`CALCULATE OXYGEN SATURATION USING
`HEMOGLOBIN CONCENTRATION
`
`-
`
`807
`
`007
`
`

`

`Patent Application Publication Dec. 25, 2003 Sheet 7 of 9
`
`US 2003/0236647 Al
`
`FIG. 9
`
`START
`
`'
`
`FILTER PULSE WAVEFORM, COLLECTED
`FOR A PREDETERMINED PERIOD,
`THROUGH A BANDPASS FILTER TO
`OBTAIN PULSE WAVE SIGNAL
`~
`DIFFERENTIATE FILTERED
`PULSE WAVE SIGNAL
`
`DETECT POINTS OF INFLECTION AT
`WHICH THE SLOPE CHANGES FROM
`POSITIVE TO NEGATIVE
`
`'
`'
`
`f.-
`
`901
`
`I--
`
`902
`
`f...- 903
`
`- 904
`
`905
`
`906
`
`STORE THE POINT OF INFLECTION
`HAVING A VALUE GREATER THAN A
`PREDETERMINED THRESHOLD
`VALUE AS A PEAK
`~
`CALCULATE AVERAGE TIME INTERVAL 1--
`BETWEEN DETECTED PEAKS
`j
`CALCU LATE THE NUMBER OF PEAKS
`IN A 60 SECOND INTERVAL, BASED -
`ON THE AVERAGE TIME INTERVAL
`BETWEEN PEAKS. AS A PULSE RATE
`
`' END
`
`008
`
`

`

`Patent Application l'ublication Dec. 25, 2003 Sheet 8 of 9
`
`US 2003/0236647 Al
`
`FIG. 10
`
`START
`I
`FILTER PULSE WAVEFORM, COLLECTED
`FOR A PREDETERMINED PERIOD,
`THROUGH A BANDPASS FILTER TO
`OBTAIN RESPIRATION SIGNAL
`I
`DIFFERENTIATE FILTERED
`RESPIRATION RESPIRATION SIGNAL
`j
`DETECT POINTS OF INFLECTION AT
`WHICH THE SLOPE CHANGES FROM
`POSITIVE TO NEGATIVE
`
`'
`
`STORE THE POINT OF INFLECTION
`HAVING A VALUE GREATER THAN A
`PREDETERMINED THRESHOLD
`VALUE AS A PEAK
`I
`CALCULATE AVERAGE TIME INTERVAL
`BETWEEN DETECTED PEAKS
`I
`CALCULATE THE NUMBER OF PEAKS
`IN A 60 SECOND INTERVAL, BASED
`ON THE AVERAGE TIME INTERVAL
`BETWEEN PEAKS, AS A RESPIRATION RATE
`
`' END
`
`f--
`
`1001
`
`f-- 1002
`
`f-- 1003
`
`1--
`
`1004
`
`f-- 1005
`
`f--
`
`1006
`
`009
`
`

`

`Patent Application I>ublication Dec. 25, 2003 Sheet 9 of 9
`
`US 2003/0236647 Al
`
`FIG. 11
`
`. ( START
`
`FILTER PULSE WAVEFORM, COLLECTED
`FOR A PREDETERMINED PERIOD, . ~ 11 01
`TO OBTAIN PULSE WAVE SIGNAL
`
`DIFFERENTIATE FIL TEREO
`PULSE SIGNAL TWICE
`
`1--
`
`1102
`
`'
`'
`'
`
`DETECT POINTS OF INFLECTION AT
`WHICH THE SLOPE CHANGES FROM 1-- 1103
`POSITIVE TO NEGATIVE
`~
`· CALCULATE DEGREE OF AGING OF
`BLOOD VESSELS BASED ON THE
`VALUES OF .INFLECTION POINTS
`
`1-- 1104
`
`' END
`
`010
`
`

`

`US 2003/0236647 Al
`
`Dec. 25, 2003
`
`1
`
`DIAGNOSTIC METHOD AND APPA RATUS USI NG
`LIGHT
`
`putting information on the result of a predetermined mea(cid:173)
`surement to the input/output unit.
`
`BACKGROUND OF THE INVENTION
`
`[0001) 1. Field of the lnvemion
`
`[0002) The present invention relates to a diagnostic
`method and appara tus using light. Mo re particularly, the
`present invention relates to a method and apparatus for
`measuring blood hemoglobin concentration, oxygen satura(cid:173)
`tion, pulse rate, respiration rate, and degree of aging of blood
`vessels using light.
`
`[0003) 2. Description of the Related Art
`
`[0004) Hemoglobin in red blood cells is responsible for
`supplying oxygen throughout the human body and is essen(cid:173)
`tial for the normal function of every cell in the body. A
`reduced supply of oxygen to the body restricts the intercel(cid:173)
`lular energy me tabolism in tissues, and a lack of oxygen for
`a prolonged period of time results in death. Hemoglobin
`content is used as a measure of anemia and is measured to
`qualify a blood donor and to determine the volume of blood
`th at may safely be taken from a blood donor.
`
`[0005) There is a need for real-time monitoring of a
`patient's condition by measuring hemoglobin concentration,
`oxygen saturation, pulse rate, respiration ra te, and degree of
`aging of blood vessels, especially in patients that are bleed(cid:173)
`ing as the result of a traffic accident and io patients io need
`of a surgical operation. Jn addition, there is a oeed for
`introducing a convenient method that enables a health care
`provider to check frequently biological conditions of chil(cid:173)
`dren and pregnant females, in particular, by measuring these
`parameters.
`
`[0006) Conventionally, hemoglobin concentration is mea(cid:173)
`sured in a medical institute for therapeutic or prophylactic
`purposes through chemical analysis of blood drawn from the
`body. The measurements of pulse rate, respiration rate, or
`degree of aging of blood vessels arc typically conducted
`only by health care providers. Therefore, a convenient
`method enabling the general public to personally measure
`each of these parameters at home is required.
`
`SUMMARY OF THE 1NVENTION
`
`[0007) The present invention provides a method and appa(cid:173)
`ratus for measuring blood hemoglobin concentration, oxy(cid:173)
`gen saturation, pulse rate, respirarion rate, and degree of
`aging of blood vessels using light.
`
`[0008) According to an aspect of the present invention,
`there is provided a diagnosis apparatus using light, including
`an input/output unit for receiving a command for measure(cid:173)
`ment from a user and for providing information oo the result
`of a mea<;urement to the user; a control unit for receiving the
`command for mea<;urement from the input/output unit and
`for generating a control signal; a light generating uni t for
`generating at least two light beams, each light beam having
`ao initial intensity, for measurement according to the control
`signal; a light receiving unit for detecting the intensity of
`each of the at least two light beams after transmission
`through ao object that is subject to measurement and for
`converting tbe received light beams into electrical signals;
`and a data processing uni t fo r processing the electrical
`signals received from the ligbt receiving unit and for out-
`
`[0009) Preferably, the light generating unit includes a
`digital-to-analog converter for receiving the control signal
`from the control unit and for converting the received control
`signal into an analog signal; a light emitting diode driver for
`driving a light emilling diode to generate the at least two
`ligbt beams according to tbe analog signal; and a ligh t
`rad iator for radiating the generated light beams onto tbe
`object.
`
`[0010) Preferably, the light receiving unit includes a pho(cid:173)
`todetector for detecting the intensities of the at least two
`light beams after transmission through the object and for
`converting the detected light beam intensities into analog
`electrical signals; a low-pass {iller for fi ltering out a high
`frequency component of the analog e lectrical signals (rep(cid:173)
`rescaling the intensity of the at least two light beams
`received from the photodetector); and an ana log-to-digital
`converter for converting the analog electrical signals (rep(cid:173)
`resenting the intensity of the light beams, from which the
`high-frequency component has been removed) into digital
`electrical s ignals.
`
`In one embodiment of the present invention, the
`[0011)
`data processing unit may include a rat io calculation portion
`for receiving the electrical signals (representing the intensity
`of the at least two light beams received by the light receiving
`unit) from the light receiv ing uni t and fo r calculating, for
`each wavelength of the at least two ligh t beams, a ratio of the
`intensity of the light received by the light receiving unit with
`respect to the initial intensity of the light radiated from the
`light generating unit; and a hemoglobin concentration and
`oxygen saturation calculation portion for calculating a
`hemoglobin concentration value using the ratio calculated
`by the ratio calculation ponioo based oo a correlation
`between light intensity variations and hemoglobin concen(cid:173)
`tra tions and for ca lculating an oxygen satura tion value using
`the calculated hemoglobin concentration value.
`
`ln another embodiment of the present invention,
`[0012)
`tbe data processing unit may include a pu lse ra te calculation
`portion for receiving the electrical signals (representing the
`intensity of the at least two light beams output from the light
`receiving uni t) from the light receiving uni t, for extracting a
`pulse wave signal havi ng a frequency corresponding to an
`average pulse rate per minute for humans from the received
`e lectrical signals, and tor calculating a pulse rate based on
`an average time interval between peaks detected fTom the
`extracted pulse wave signal.
`
`Ia yet another embodiment of the present inven(cid:173)
`[0013)
`tion, the data processing uni t may include a respiration rate
`calculation portion for receiving tbe electrical signal<; (rep(cid:173)
`resenting the intensity of the at least two light beams output
`from the ligh t receiving unit) from the light receiving unit,
`for extracting a respiration signal having a frequency cor(cid:173)
`responding to an average respiration rate per minute for
`humans from the received electrical signals, and for calcu(cid:173)
`lating a respiration rate based oo ao average time interval
`between peaks detected from the extracted respiration sig(cid:173)
`nal.
`
`In stiiJ another embodiment of the present inven(cid:173)
`[0014)
`tion, the data processing uni t may incl ude a degree of aging
`of blood vessels calculation portion for receiving the elec-
`
`011
`
`

`

`US 2003/0236647 Al
`
`Dec. 25, 2003
`
`2
`
`trical signals (representing the intensity of the at least two
`light beams output [rom the light receiving unit) from the
`light receiving unit, for extracting a first pulse wave signal
`having a frequency corresponding to an average pulse rate
`per minute for humans from the received electrical signals,
`for di1Ierentiating tbe extracted first pulse wave signal into
`a second pulse wave signal to detect inflection points
`therein, tor calcu lating a diagnostic index for the degree of
`aging of blood ves.5els using the values of the inflection
`points, and for calculating a degree of aging of blood vessels
`using tbe calcu lated diagnostic index, based on a correlation
`between the degrees of aging of blood vessels and diagnostic
`indices therefor.
`[0015)
`In addition, the data processing unit may (urlher
`inc lude a data storage portion for storing measured results
`and for outpulling to the input/output un it a calculated resul t
`according to a control signal of the control unit.
`(0016) Accordi ng to another aspect of the present inven(cid:173)
`tion, there is provided a diagnosis method using light,
`including (a) receiving a command for measurement from a
`user; (b) generating a control signal according to lbe
`received command for measurement; (c) generating at least
`two light beams, each light beam having an initial intensity,
`for measurement accordi ng to the control signal; (d) radi(cid:173)
`ating the at least two light beams onto an object that is
`subject to measurement, detecting the intensities of tbe at
`least two light beams after tra nsmission through the object,
`and converting the detected intensities of tbe at least two
`light beams into electrical signals; and (e) processing the
`electrical signals to obtain information on tbe result of a
`predetermined measurement.
`(0017) Preferably, generating tbe at least two ligbt beams
`includes (cl) receiving tbe control signal and converting tbe
`received control signal into an analog signal; (c2) generating
`tbe at least two ligbt beams according to tbe analog signal;
`and (c3) racliatiog the generated light beams onto the object.
`[0018] Preferably, radia ting the light beams onto an object
`includes (dl) detecting the intensities of tbe at least two ligbt
`beams after transmis.5io n through the object aod converti ng
`tbe detected ligbt beam intensities into aoalog electrical
`signals; (d2) filtering out a higb frequency component of tbe
`analog electrical signals (representing the intensity of the
`transmilled ligbt beams); and (d3) converting tbe analog
`electrical signals (representing the intensity of the light
`beams, [rom which the high-frequency component has been
`removed) into digi tal electrical signals.
`(0019)
`In one embodimen t of the present inventio n, pro(cid:173)
`cessing tbe electrical signals may include (el) calculating,
`for each wavelength of the at least two light beams, a ratio
`of the intensity of the ligbt beam detected in (d) with respect
`to tbe initial intensity of the light generated in (c); (e2)
`calculating a hemoglobin concentration value using the ratio
`calculated in (e1) based on a correlation between light
`intensity variations and hemoglobin concentrations and cal(cid:173)
`culating an oxygen satura tion value using the calculated
`hemoglobin concent ration value.
`(0020)
`In another embodiment of the present invention,
`proces.<;ing the electrical signals may include extracting a
`pulse wave signal baving a frequency corresponding to an
`average pulse rate per minute for humans from the electrical
`signals obtained in (d); and calculating a pulse ra te based on
`an average time interval between peaks detected from the
`extracted pu L5e wave signal.
`
`In yet another embodiment of the present inven(cid:173)
`[0021)
`tion, processing the electrica l signals may include extracting
`a respiration signal having a frequency corresponding to an
`average respira tion rate per minute for humans from tbe
`electrical signals obtained in (d); and calculating a respi ra(cid:173)
`tion rate based on an average time interval between peaks
`detected from the extracted respiration signal.
`
`In still another embodiment of the present inven(cid:173)
`(0022)
`tion, processing the electrical signals may include extractiog
`a first pulse wave signal having a frequency corresponding
`to an average pulse rate per minute for humans from tbe
`in (d); dif[erentiating
`the
`electrical signals obtained
`extracted first pulse wave signal into a second pulse wave
`signal to detect inflection points therein; calculating a diag(cid:173)
`nostic index for lbe degree of aging of blood vessels using
`the values of the inf:le.ction points; and calculating a degree
`of aging of blood ves.<;els using the calculated diagnostic
`index, based on a correlation between the degrees of aging
`of blood vessels and diagnostic indices therefor.
`
`[0023) The diagnosis method may furlber include provid(cid:173)
`ing the result of the predetermined measurement to the user,
`wherein lbe user may be remotely located from tbe object
`subject to measurement. The diagnosis me thod may also
`further include storing the infomlation on the resu lt or the
`predetermined measurement.
`
`In any of the aspects and embodiments of tbe
`[0024)
`present invention, preferably, the at least two light beams
`have different wavelengths. Also preferably, tbe at least two
`ligbt beams are selected from a range of wavelengths in
`which the extinction coefficient for water is smaller than that
`of hemoglobin and have a wavelength no longer tbao 1300
`om. Preferably, the at least two light beams are isobestic and
`each bas a wavelength selected from the group consisting of
`422 om, 453 om, 499 om, 529 om, 546 om, 569 om, 584 om,
`805 om, and 1300 om.
`
`(0025) Ano ther feature of an embodiment of the present
`invention is to provide a computer readable medium having
`embodied tbercon a computer program for any of tbe
`above-described diagnosis methods.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`(0026) The above features and advantages of the present
`invention will become more apparent to those of orclioary
`skill in the art by describing in detail preferred embodiments
`thereof with reference to the attached drawings in which:
`(0027) FIG. 1 is a block diagram illustrating the overall
`configuration of a diagnosis apparatus using ligbt, according
`to an embodiment of tbe present invention;
`
`(0028) FlG. 2 is a detailed block diagram of the light
`generating unit of FIG. 1;
`(0029) FIG. 3 is a detailed block diagram or tbe light
`receiving unit of FIG. 1;
`(0030) FIG. 4 is a detailed block diagram of the data
`processing unit of FIG. 1;
`(0031) FIG. 5 is an exemplary pulse wave measured ill
`accordance witb an embodiment of the present invention;
`
`(0032) FLG . 6 are graphs of quantitative diagnostic indices
`for the degree of aging of blood vessels, which are applied
`in the present invention;
`
`012
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`

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`
`Dec. 25, 2003
`
`3
`
`[0033) FIG . 7 is a flowchart illustrating a diagnosis
`method using light, according to ao embodiment of the
`present invention;
`
`[0034) FIG. 8 is a flowchart illustrating a method for
`measuring hemoglobin concentration and oxygen saturation
`in step 705 of FIG. 7 ;
`
`[0035] FIG. 9 is a flowchart illustrating a method for
`calculating pulse rate in step 706 of FrG . 7;
`
`[0036] FIG. 10 is a flowchart illustrating a method for
`calculating respiration rate in step 706 of FlG. 7; and
`
`[0037] F lG. 11 is a flowcha rt illustrating a method for
`calculating degree of aging of blood vessels in step 707 of
`FIG. 7.
`
`DETAILED DESCRIPTION OF THE.
`INVENTION
`
`[0038] Korean Patent Application No. 2002-14277, filed
`on Mar. 16, 2002, and entitled: "Diagnostic Method and
`Apparatus Using Light," is incorporated by reference herein
`in its entirety.
`
`[0039) Several embodiments of a diagnosis method and
`apparatus for measuring blood hemoglobin concentration,
`oxygen saturation, pulse rate, respiration ra te, and degree of
`aging of blood vessels using light, according to the present
`invention, will now be described with reference to the
`appended drawings.
`
`[0040] F IG. 1 shows the overall configuration of a diag(cid:173)
`nosis appa ratus using light, according to an embodiment of
`the present invention. The diagnosis apparatus of FIG. 1
`includes an input/output uni t 101, a control unit 102, a light
`generating unit 103, a light receiving unit 104, and a data
`processing unit lOS.
`
`In operation, a user provides the input/output un it
`[0041]
`101 a parameter to be measured, such as blood hemoglobin
`concentration, oxygen saturation, pu lse rate, respiration rate,
`degree of aging of blood vessel'> (hereinafter "DOA''). The
`input/output unit 101 informs the user of the result of a
`measurement of the input parameter. The inpul/output unit
`101 may use a bullon, a mouse, a keyboard, or the like as an
`input device and may use a computer monitor, a liquid
`crystal display (LCD), or other display as an out put device
`for providing the information rega rding the result of the
`measurement to the user. Alternatively, information on the
`result of a measurement may be transmitted via, for
`example, an RS232 port to an external personal computer
`(PC), a personal digital assist<tot (PDA), or the like. Accord(cid:173)
`ingly, tbe user may be remotely located from the patient and
`the object subject to the measurement.
`
`[0042] The control unit 102 receives a command to mea(cid:173)
`sure a predetermined parameter from tbe input/output uni t
`101 and transmits information on the parameter to the light
`generating unit 103, the light receiving unit 104, and the data
`processing unit 105. The control unit 102 also verifies the
`operation of each unit of the diagnosis apparatus.
`
`[0043) The light generating unit 103 generates at least two
`light beams having predetermined wavelengths fo r measure(cid:173)
`ment according to the information on tbe parameter received
`from the control uoit 102. A detailed configu.ration of the
`Light generating unit 103 is shown in H G. 2. Referring oow
`
`to FIG. 2, the light generating unit 103 may include a
`digital-to-analog converter (DAC) 201 for converting a
`digital control signal received from the control unit 102 into
`an analog signal, a light emitting diode (LED) driver 202 for
`receiving the analog control signal and for driving an LED
`thai generates the at least two light beams having predeter(cid:173)
`mi ned wavelengths, and a light radiator 203 for externally
`radiating the at least two light beams onto an object to be
`measured.
`
`[0044) Referring back to Fl G . 1, the light receiving uni t
`104 measures the intensities of the ligbt beams transmitted
`through the object, among the light beams emitted from the
`light generating unit 103, and converts the light beams to
`electrical signals. The configuration of the light receiving
`unit 104 is shown in detail in FIG. 3. Referring now to FIG.
`3, the light receiving unit 104 may include a photodetector
`301 for detecting tbe intensities of the light beams trans(cid:173)
`mitted through the object aod for converting the light beams
`to electrical signals, a low-pass filter (LPF) 302 for filtering
`out a high frequency component of the electrical signals
`representing the intensity of the light beams received from
`the photodetector 301, and an analog-to-digital converter
`(ADC) 303 for convert ing the analog electrical signals, from
`which the high-frequency component has been removed by
`the LPF 302, into digital electrical signals.
`
`[0045) Referring back to FIG. 1, the data processing uni t
`105 receives the electrical signals representing the intensity
`of the received light beams from the light receiving unit 104
`and processes the received electricaE signal'> to provide
`information on the resul t of a measurement of the inp ut
`parameter, such as blood hemoglobin concentration, oxygen
`saturation, pulse rate, respiration rate, and DOA of blood
`vessels. The configuration of the data processing tmit 105 is
`shown in detail in FIG . 4.
`
`[0046) Referring to FIG. 4, tbe data processing unit 105
`may include a data storage portion 406, a ratio calcu lation
`portion 401, a hemoglobin concentration and oxygen satu(cid:173)
`ration calculation portion 402, a pulse rate calculation por(cid:173)
`tion 403, a respiration rate calculation portion 404, and a
`DOA calculation portion 405. The f11nction of each of these
`elements will now be explained.
`
`[0047) The ratio calculation portion 401 receives the digi(cid:173)
`tal intensity signals fo r the received ligbt beams output from
`the light receiving uo it 104 and, for each of the light beams,
`calcu lates a ratio of the intensity of the light received by the
`light receiving unit 104 wi th respect to the initial intensity of
`the light radiated from the light generating unit 103 onto the
`object that was subjected to the measurement.
`
`[0048] The hemoglobin concentration and oxygen satura(cid:173)
`tion calcu lation port ion 402 calculates a hemoglobin con(cid:173)
`centration value using the ratio calculated by the ra tio
`calculation portion 401 based on a correlation between light
`intensity varia tions and hemoglobin concentrations, and
`calculates an oxygen saturation value using the calculated
`hemoglobin concentration value. A method for calculating
`oxygen saturation following the calculation of hemoglobin
`concentration is briefly described below. Oxygen saturation,
`which is expressed as a percentage of the concentration of
`oxyhemoglobin bound to oxygen with respect to total hemo(cid:173)
`globin concentration, is measured to q11antify tbe amount of
`oxygen saturated in blood for the nor1111al f11nction of body
`cells. To measure oxygen saturation, red ligbt and infrared
`
`013
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`

`

`US 2003/0236647 Al
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`Dec. 25, 2003
`
`4
`
`light are transmitted through biological tissues, the absor(cid:173)
`bance for each wavelength of the radiated lights is measured
`using pulses of arterial blood, and a ratio of the measured
`absorbances is calculated as the oxygen saturation. Most of
`the light radiated on the human body is absorbed by bones,
`tissues, etc., which <tre not involved in pulsing, via prede(cid:173)
`termined travelling paths, and only 1-2% of the light radi(cid:173)
`ated is absorbed by arterial blood, whicb induces pulses. By
`measuring the intensity of the light transm itted th rough the
`body, the light absorbencies of the pulsing components and
`tbc non-pulsing components for each wavelength of the
`radiated light beams can be calculated, which will give the
`light absorbance of hemoglobin present in the arterial blood.
`As a result, the oxygen saturation of hemoglobin can be
`determ ined from the abso rbance ratio between the two
`wavelengths of light.
`
`[0049) The pulse rate calculation portion 403 receives the
`digital signa ls corresponding to the intensities of the
`received light beams from the light receiving unit 104,
`extracts a pulse wave signal having a frequency correspond(cid:173)
`ing to an average pulse rate per minu te for humans from the
`received digital signal , and calculates a pulse ra te per minute
`based on an average time interval between peaks detected
`from the extracted pulse wave signal.
`
`[0050] More specifica lly, the pulse rate calculation portion
`403 receives the digital signals corresponding to the inten(cid:173)
`sities of the ligbt beams sequentially transmitted through a
`predetermined body site to be measured, e.g., a finger, and
`extracts only a pulse wave signal having a frequency in
`accordance with an average pulse rate for humans from the
`received signals using, for example, softwa re such as a
`filtering program. Differentiation is performed on the pulse
`wave signal passed through a filter, and inflection points, at
`which the slope changes from positive to negative, are
`detected from the differentia ted pulse wave signal. When an
`inflection point has a value greater than a predetermined
`th resho ld value, ibe inflection point is stored as a peak. An
`average time interval between detected peaks is calculated,
`and the number of peaks in a 60 second interval is calculated
`based on the average time interval as a pulse rate.
`
`[0051) A received signal, as described above, may be
`classified into pulse waves, velocity pulse waves, or accel(cid:173)
`eration pulse waves according to the signal processing
`technique applied to the received signal. In general, pulse
`waves refer to the original wavefo rm of body pulses and are
`used to characterize the original body pulses. However, the
`original body puLc;es have too smooth a waveform for
`variations to be detected. To compensate for Ibis smooth(cid:173)
`ness, the original body waves are differen tiated fo r clinical
`applications. These differen tial body waves are called
`"velocity pulse waves." Veloci ty pulse waves are used to
`analyze variations in tbe waveform of the original body
`waves. Velocity pulse waves, i.e., differential pulse waves,
`arc used in currently available pulse wave detectors. How(cid:173)
`ever, variations in the origina l body waves cannot be fully
`analyzed with velocity pulse waves. For this reason, velocity
`pulse waves are further dil:Ierentiatcd into .. acceleration
`pulse waves" for clinical uses. Recent advances in the
`medical engineering field, especially in the diagnosis of
`circulatory system disorders, have