NIRS instrument basics and a
new multiple NIRS systemwith the CDMA technique
Mitsuo Ohashi(1) , *Hideo Eda(2)(1)Spectratech Inc. Yokohama, Japan,(2)Grad. School of GPI, Hamamatsu, Japan

Near Infrared Spectroscopy (NIRS)
calculates hemoglobin parameters,such as changes in oxyHb and deoxyHb.

http://209.73.52.252/ass
ets/pdf/hpspdf/C8686.pdf
Natural posture example.

Brain activation can be measured
in the natural posture.
http://www.nict.go.jp

There have been many NIRS systems
in Japan.
http://www.hitachimedical.co.jp/opt-e/index.htmlhttp://www.hpk.co.jp/eng/pro
ducts/SYSE/Niro300E.htm

These pictures were several years ago.
The companies released the new products.

http://www.med.shimadzu.co.jp/products/om/index.html( in Japanese)NIRS History in Japan
1980
1977
Jobsis （Duke Univ.）
Science 198:1264
International Patents(Unpatented in Japan)

1990

2000
Topography

Spectroscopy
HitachiTomography
Hamamatsu
Shimadzu
Omron

NEDO Project（1992 - 1999）
Tamura, Yamada (AIST)
Shimadzu, Hamamatsu

Hitachi
Delpy (UCL)
Arridge (UCL)
Chance (U. Penn.)
Tamura (Hokkaido Univ.)US patent 4281645,Jobsis, (Filed 1977)

6

US patent 4223680,Jobsis, (Filed 1977)

7

We must know that NIRS is not young
1980
1977

1990

2000
Topography

Spectroscopy
NEED Breakthrough!
Jobsis （Duke Univ.）
Tomography
Science 198:1264

X ray CT
Hounsfield (1973)
MRI
Lauterbur (1973)
8Nobel Prize

Project on the Decade of the Brain (1990)

fMRI
SPM99
Ogawa(1992) UCL (2000)

For NIRS breakthrough,think about ‘NIRS Innovation’CDMA
Other fields
marketing

Wireless NIRSNew users
Portable NIRS
Spectra analysis
engineering approach

9Channel separation is needed
for NIRS imagingDetector has to know signal from A or from B.
CSource A

http://www.spectratech.co.jp/

AB

Source B

Channel separation
ＴＤＭＡ（Time Division Multiple Access）
ＦＤＭＡ（Frequency Division Multiple Access）
ＣＤＭＡ（Code Division Multiple Access）

ＴＤＭＡ
Time Division Multiple Access
SourceDetector

time
Only one source is ON at the time.

http://www.spectratech.co.jp/

ＦＤＭＡFrequency Division Multiple Access
ON123
45timeSource
ｆ１

f2

f3

f4

f5

Amplitude

Detectorfrequency
http://www.spectratech.co.jp/

Brief history of CDMA
１９５９J.P.Costas, “Poisson Shannon and the Radio Amateur”１９８０
EU: Mobile Phone

１９９３
Qualcom(USA); Standard of Digital mobile phone

１９９３
WaveLAN by NCR(USA) came to Japan.

http://www.spectratech.co.jp/

CＤＭＡ
Code Division Multiple Access
12
Modulate using Random number

3＝Spread Spectrum

4
5

time

SourceDetector
Amplitude

1
2
3
4
5

Frequency
http://www.spectratech.co.jp/

Measure tissue information; b(t)x(t)=a1(t)x(t)=a1(t)b(t)830+a2(t)b(t)780

CW laserSensor(ex 830nm)(APD or PMT)b(t)830

random numbera1(t)Y(t)=x(t)a1(t)=a1(t)b(t)830 a1(t)=a12(t)b(t)830=b(t) 830
random numbera1(t)b(t)780

CW laser

Y(t)=x(t)a2(t)=a2(t)b(t)780 a2(t)=a22(t)b(t)780=b(t) 780

(ex 780nm)

random numbera2(t)x(t)=a2(t)Random number is called as PIN code.
M-series, Hadamard code, Gold series, etc
http://www.spectratech.co.jp/

randomnumber a2(t)CDMA mechanism
time

1
Source2
3+１
ｰ１+１ｰ１+１ｰ１

Bit rate＝ Equivalent bandwidthＸ

Demodulate bych1 waveform+１ｰ１＝+１

1
Detectorｰ１

Chip rate= n+１2ｰ１= 0+１3ｰ１= 0

Summation of these signal
http://www.spectratech.co.jp/

Diffusivity=bit rate / chip rate
２８～２１６

Comparison
ＴＤＭＡＦＤＭＡＣＤＭＡ

Theoryeasy

complicateddifficult

Increase number ofChannels△○◎

Simultaneous
measurement△◎◎

High SNR

Zone restrictions

Zone restrictions

Some ways

Influence of
external noise

Big

Low

LowestHardwareEasy/Small

Complicated/Large

Easy/Small

ExamplesInternet packet

Digital broadcasting（13 segment ＯＦＤＭ）

Mobile Phone
GPS(Car navigation)

http://www.spectratech.co.jp/

Experimental setup
Laser 12CH ( 4 ｘ ３wavelength ）PhantomUSB
３x３

FDMA modulator １２CH
FDMA demodulator ５CH
CDMA modulator １２CH
CDMA demodulator ６０CH３ｍｍ
Sensor 5
APD zone 1００KHｚ
PMT zone １MHｚ

http://www.spectratech.co.jp/

Polyplopilem

Channel separation
FDMA １０Hz LPF

λ＝830nmCDMA-２12Bit

λ＝830nm

λ＝690nm

λ＝690nmFDMA ２Hz LPF

CDMA-２16Bit
λ＝830nm

λ＝830nm

λ＝690nm
λ＝690nmtime（ｔ）

time（ｔ）

http://www.spectratech.co.jp/

２ｍW laser output ｘ １０－７

Optical intensity

Brain measurement at rest
λ=690nm

λ=830nmHb parameter

OxyHb

Laser
Chip rate
PMT gainMeasure time
Areabit
Equivalent bandwidth
sampling
SNRDeoxyHb
bandwidthLow

http://www.spectratech.co.jp/

time （120sec）

High2mW/830nm +690nm
１MHｚ５ｘ１０６20 sec
Temporal lobe
２１５Bit15 Hz33 ｍＳ
49.3 ｄB

Brain measurement
Nintendo DS Kanji training
Task：NintendoDS
脳を鍛える大人のＤＳトレーニング漢字問題
FrontalLow ：⊿oxyHb,⊿deoxyHb

Rest (150sec)

Task (150sec)

Middle: SO2?

High：Heart Rate
http://www.spectratech.co.jp/

Multiple point detection is easily
possible with CDMA

http://www.spectratech.co.jp/

Spectratech OEG-16
http://www.spectratech.co.jp/

８ｍｍΦ

PIN photo diode and Ampliphier

http://www.spectratech.co.jp/

Spectrum of FDMA and CDMAf

ＦＤＭＡ

http://www.spectratech.co.jp/

fＣＤＭＡ

Conclusion
NIRS basic and history were described.
 For imaging, Channel separation isimportant.
 TDMA, FDMA, CDMA can be used for
NIRS imaging.
 NIRS using CDMA in now on themarket. (http://www.spectratech.co.jp/)