Principi della spettroscopia nel

(1)

Department of Biomedical Engineering

Tufts University, Medford, Massachusetts, USA

Principi della spettroscopia nel

vicino infrarosso e applicazioni per studi diagnostici e funzionali

Sergio Fantini

(2)

Spettroscopia nel vicino infrarosso

o Breve introduzione storica

o Principi della tecnica per lo studio di tessuti biologici

o Ossimetria

o Mammografia ottica

o Studio funzionale del cervello

(3)

1930 1940 1950 1960 1970 1980 1990 2000 2010

Breast transillumination, M. Cutler, Surg. Gynecol. Obstet. 48, 721 (1929).

Diaphanography, C.M.Gros, J.

Radiol. Electrol. 53, 297 (1972).

Lightscanning, E.Carlsen,

Diagn. Imaging 4, 28 (1982). Multicenter study, A. Alveryd et al., Cancer 65, 1671 (1990).

1990’s-2000’s:

•Time-resolved methods;

•Broadband spectroscopy;

•Optical tomography;

•Co-registration with US, MRI, CT;

•Photo-acoustics, acousto-optics;

•Fluorescence contrast agents.

Optical Mammography

1930 1940 1950 1960 1970 1980 1990 2000 2010

Optical Oximetry

Calibrated oximetry, G.A.Millikan, Rev. Sci. Instr. 13, 434 (1942).

Non-pulsatile oximeter,

K.Matthes, Arch. Exp. Pathol.

Pharmacol. 176, 683 (1934).

HP Oximeter, E.B.Merrick et al., Hewlett-Packard J. 28, 2 (1976).

Pulse oximetry, I. Yoshiya et al., Med.

Biol. Eng. Comput. 18, 27 (1980).

1990’s:

Time-resolved, quantitative, absolute tissue oximetry

1930 1940 1950 1960 1970 1980 1990 2000 2010

Functional Brain Imaging Non-Invasive brain study, F.

Jöbsis, Science 198, 1264 (1977). Functional studies:

•B.Chance et al., PNAS 90, 3770 (1993);

•Y.Hoshi and M.Tamura, J.

Appl. Physiol. 75, 1842 (1993);

•T.Kato et al., J. Cereb. Blood Flow Metab. 13, 516 (1993);

•A.Villringer et al., Neurosci.

Lett. 154, 101 (1993).

2000’s:

•Co-registration with fMRI, ERP;

•Modeling of NIRS signals;

Fast optical signal, G. Gratton et al., Psychophysiology 32, 505 (1995).

(4)

Epithelial tissue

Stratified squamous

epithelium

(5)

Connective tissue

Loose (areolar) connective tissue Bone

Adipose tissue Blood

10mm

(6)

10mm

Muscle tissue

Skeletal muscle Smooth muscle

Cardiac muscle

10mm

(a)

(b)

(c)

(7)

Generalized animal cell

Cell size ~10mm

Mitochondrion size ~0.5mm

(8)

Scattering spectra in various tissues

(9)

Glucose effect on the scattering coefficient in vitro

(10)

Glucose effect on the scattering coefficient in vivo

(11)

Hemoglobin

(12)

Hemoglobin absorption spectra

(13)

0.01 0.1 1 10 100

300 400 500 600 700 800 900 1000 1100 1200 1300

Dominant tissue chromophores in the near infrared

ultraviolet near infrared

410 nm 600 770 nm 1300

wavelength (nm)

HbO₂ Hb H₂O

Hb, HbO₂ from: Cheong et al., IEEE J. Quantum Electron. 26, 2166 (1990) H₂O from: Hale and Querry, Appl. Opt. 12, 555 (1973)

absorp ti on coeffic ien t (cm

-1

)

(14)

Diffusion of near-infrared light inside tissues

low power laser

biological tissue

optical detector optical fiber

(15)

high scattering problem

is there a car in front

of me?

is there a cookie in the milk?

(16)

Experimental approach to tissue spectroscopy

Continuous wave (CW)

Time domain (TD)

L m_a=1/L ln(I₀/I_t)

I₀ I_t

I₀

I_t

t=0 ~ns

intensity

(17)

Frequency-domain spectroscopy (FD)

0 0.5 1 1.5 2

0 5 10 15 20

0 0.5 1 1.5 2

0 5 10 15 20

phase shift

tissue

t (ns)

intens it y (a.u. ) intens it y (a.u. )

dc ac

(18)

Diffusion equation for the photon density U(r, t )

D = 1/[3(m_a+m_s’)] = diffusion coefficient m_a = absorption coefficient

m_s’ = reduced scattering coefficient v = speed of light in tissue

q = source term (power per unit volume)

frequency-domain Green’s function G(r, w ) for an infinite geometry:

2 / 1

 

 



 -

 v vD i k m

^a

w e r

r vD

G ^

^-^kr

w 

4 ) 1

, (

) , ( )

, ( )

, ) (

,

( vD

₂

U t v U t q t

t t

U r -  r +

a

r  r



 m

with

(19)

Straight lines as a function of r (distance from the source)

from the following definitions:

Abs[G( r ,0)]  dc intensity (or average intensity I

_dc

) Abs[G( r , w )]  ac amplitude

Arg[G( r , w )]  phase

it follows that (for the Green’s function):

ln( r I

_dc

) = - r Re[ k ] – ln[4  vD ] phase = r Im[ k ]

ln(r, I dc)

r intercept (m_s’)

slope (m_a, m_s’)

phase

intercept = 0 r

slope (m_a, m_s’)

(20)

Measurement of absorption and

reduced scattering coefficients with frequency-domain spectroscopy

where: m

_a

: absorption coefficient

m

_s

’ : reduced scattering coefficient w : angular modulation frequency v : speed of light in tissue

S

_F

: phase slope

S

_ac

: ln( r | U

_w

|) slope

(21)

Translating the absorption coefficient into hemoglobin-related parameters

] HbO [

] Hb

[ +

₂

 THC

O]

H )[

( Hb]

)[

( ]

HbO )[

( )

(

_HbO ₂ _Hb _H _O ₂

2

2 i i i

i

a

      

m  + +

2 Hb

HbO2 2

Hb 2

HbO2

Hb HbO2

Hb 2

Hb HbO2

2

) ( ) ( )

( )

(

) ( ) ( )

( ) ( )

( )

( ]

HbO [



 

 -



 







 







 







 

 -



 







 









i

i i

i

i i

i

i i

i

i i

a i

i i

a





























 m









 m

2 Hb

HbO2 2

Hb 2

HbO2

Hb HbO2

HbO2 2

HbO2 Hb

) ( ) ( )

( )

(

) ( ) ( )

( )

( ) ( ]

Hb [



 

 -



 







 







 







 

 -



 







 









i

i i

i

i i

i

i i

i

i i

a i

i i

a





























 m









 m

] HbO [

] Hb [

] HbO StO [

2 2

2

 +

Total hemoglobin concentration Hemoglobin saturation (Y)

Oxy-hemoglobin

concentration Deoxy-hemoglobin

concentration

(22)

TISSUE OXIMETRY

(23)

Configuration for tissue oximetry

measuring probe

main box

laser diodes source optical fibers

detector optical fiber

laser driver detector

RF electronics

multiplexing circuit

OxiplexTS, ISS, Inc., Champaign, Illinois

(24)

HbO

2

and Hb ( m M)

20 30 40 50 60 70 80 90

0 2 4 6 8 10 12 14 16 18

Frequency-domain oximetry

750nm

time (min) m a (1/cm)

830nm 750nm

0.17 0.18 0.19 0.2 0.21 0.22 0.23 0.24 0.25

0 2 4 6 8 10 12 14 16 18

830nm

3.8 4 4.2 4.4 4.6 4.8 5

0 2 4 6 8 10 12 14 16 18

ischemia time (min) ischemia

m s’ (1/cm) time (min)

saturation (%)

time (min)

20 30 40 50 60 70 80 90 100

0 2 4 6 8 10 12 14 16 18

ischemia ischemia

(25)

Arterial occlusion  oxygen consumption

(measurement on the forearm of subject 1)

ischemia

Hb_tot

Hb

hemoglobin concentration (mM) hemoglobin saturation (%)

time (min)

oxygen consumption = 3.2 mmol/100mL/min HbO₂

ischemia

20 40 60 80 100

0 2 4 6 8 10 12 14 16 18

20 30 40 50 60 70 80 90 100 110

0 2 4 6 8 10 12 14 16 18

(26)

10 20 30 40 50 60 70 80 90 100

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

hemoglobin concentration (mM)

Venous occlusion  blood flow

(measurement on the forearm of subject 2)

hemoglobin saturation (%)

time (min)

time (min) venous occlusion

(50 mmHg) Hb_tot

Hb

HbO₂

blood flow = 2.5 mL/100mL/min

venous occlusion (50 mmHg)

20 40 60 80 100

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

(27)

3 cm 4 cm

source 1 source 2

det.a det.b

probe geometry

Measurement on the forehead at different percentages of inspired oxygen

3 cm 4 cm

(28)

m

a

(cm

-1

)

wavelength (nm) 21%O

₂

(air)

10%O

₂

21%

O₂

10%

O₂

HbO₂ 30.2 29.5 mM Hb 10.1 11.6 mM T HC 40.3 41.2 mM Y 74.9 71.8 % SaO₂ 97 93 %

pulse 85 86 ^{beat/ min}

Absorption spectra of the forehead at different inspired oxygen concentrations

after 1 min of

0.06 0.08 0.1 0.12 0.14 0.16 0.18

600 650 700 750 800 850

(29)

0 0.001 0.002 0.003 0.004

0 0.5 1 1.5 2 2.5

m

a

(cm

-1

)

^{830 nm}

time (min) frequency (Hz)

powe r sp ect ra

fft on 256 points

21%O₂ 10% O₂

Arterial pulse and absorption coefficient

0.108 0.11 0.112 0.114 0.116 0.118 0.12

0 0.05 0.1 0.15 0.2 0.25

85 beats/min

(30)

1.5E-05 2E-05 2.5E-05 3E-05 3.5E-05 4E-05 4.5E-05

600 650 700 750 800 850

norma liz ed pulsa ti le Dm

a

(a .u .)

wavelength (nm)

21%O

₂

10%O

₂

SaO

₂

with tissue spectrometer 98 94 % SaO

₂

with pulse oximeter 97 93 %

Arterial saturation from pulsatile Dm _a absorption

21%O

₂

10% O

₂

(31)

Tissue and arterial saturation

0 50 100 150 200

70 71 72 73 74 75 90 92 94 96 98 100

21% O₂ 10% O₂

21% O₂

tissue saturation (%) arterial saturation (%)

time (sec) SaO₂

Y

pulse oximeter

frequency-domain tissue spectrometer

(32)

OPTICAL

MAMMOGRAPHY

(33)

M. Cutler, “Transillumination of the Breast,” Surg. Gynecol. Obstet. 48, 721-727 (1929). (now J. Am. Coll. Surg.)

The first optical study of the breast: 1929

(34)

instrument for frequency-

domain optical mammography

PMT

690 nm

856 nm 788 nm 750 nm

laser diodes

69.50 MHz 69.80 MHz 70.20 MHz 70.45 MHz

data processing fiber coupler

(35)

(36)

x-ray vs. optical mammography

N @830 nm LML N @830 nm LCC

P2-C30L

X-ray lml X-ray lcc

invasive ductal cancer 3cm of diameter

Optical lcc

Optical lml

Franceschini et al., Proc. Natl. Acad. Sci. USA 94, 6468-6473 (1997)

(37)

Oxygenation Index images from multi-wavelength optical mammograms

low high

N’’ images at four wavelengths Oxygenation Index image

2 Hb HbO2

2 Hb 2

HbO2

Hb HbO2

Hb 2

HbO2 Hb 2

) ( ) ( )

( )

(

) ( ) ( )

( ) ( )

( )

( ]

HbO [











    

-











  











  











    











    

-











  











    

 D



 

i

i i

i

i i

i

i i

i

i i

i

i i

i

i N

N

2 Hb HbO2

2 Hb 2

HbO2

Hb HbO2

HbO2 2

Hb HbO2

) ( ) ( )

( )

(

) ( ) ( )

( )

( ) ( ]

Hb [











    

-











  











  











    











    

-











  











    

 D



 

i

i i

i

i i

i

i i

i

i i

i

i i

i

i N

N



D + D

 D

] Hb [ ] HbO [

] HbO Index [

n Oxygenatio

2 2

For pixels with a negative N’’:

[S. Fantini et al., Proc. SPIE 4955, 183 (2003).]

690 nm _rcc

750 nm _rcc

788 nm _rcc

0.0 2.5 5.0 7.5

856 nm rcc

0 2 4 6 8 10 12 14 16 18 0.0

2.5

5.0 7.5 10.0 12.5

x (cm)

y (cm)

rcc

(38)

Patient Number 215, 53 y.o.

3.0 cm invasive ductal carcinoma, left breast

0 2 4 6 8 10 12 14 16 18 20 0

2 4 6 8 10

x (cm)

y (cm)

0 2 4 6 8 10 12 14 16 18 20 0

2 4 6 8 10

x (cm)

y (cm)

0 2 4 6 8 10 12 14 16 18 20 0

2 4 6 8 10

x (cm)

y (cm)

N at 690 nm N’’ at 690 nm Oxygenation Index

Cancer Cancer

Cancer

0 2 4 6 8 10

20 18 16 14 12 10 8 6 4 2 0

y (cm)

x (cm)

Cancer

low high

0 2 4 6 8 10

20 18 16 14 12 10 8 6 4 2 0

y (cm)

x (cm)

Cancer

0 2 4 6 8 10

20 18 16 14 12 10 8 6 4 2 0

y (cm)

x (cm)

Cancer

lcc lcc lcc

lob lob

lob

(39)

A more challenging case:

Cancer size < 0.5 cm

(a) N-image (b) N ″-image (c) Oxygenation image

Low High

Oxygenation Index

rob rob rob

(40)

OPTICAL IMAGING

OF THE BRAIN

(41)

The basic approach to optical imaging of the brain

From the light source To the optical detector

(42)

Bilateral optical imaging of the brain

(43)

NIRS-fMRI compatible helmet

Elastic bands

Source fiber

Detecting fiber

3 2

D C

B A

1 4

5

6 7 8

9 11 10

12 13

14 15 16

detector source

L R

3.5 cm

C

(44)

“Minority report,” year: 2054

(45)

D deoxy-hemoglobing conc.( m M)

-.4 -.2 0 .2 .4 -.15 -1 -.05 0 .05 1 .15

Right hand tapping

(46)

D deoxy-hemoglobing conc.( m M)

-.4 -.2 0 .2 .4 -.15 -1 -.05 0 .05 1 .15

Right hand tapping

(47)

-.4 -.2 0 .2 .4 -.15 -1 -.05 0 .05 1 .15

D deoxy-hemoglobing conc.( m M)

left hand tapping

(48)

-.4 -.2 0 .2 .4 -.15 -1 -.05 0 .05 1 .15

D deoxy-hemoglobing conc.( m M)

left hand tapping

(49)

Time (s)

-1 -0.5 0 0.5

0 10 20 30 40 50 60 70 80

D[Hb],D[HbO 2] (mM)

D[Hb]

D[HbO₂]

Hand tapping

Hemodynamic response to brain activation

, 1

1 HbT]

[ SO

SO 1 SO

HbT]

[ SO

HbT]

[

HbT]

1 [ SO

1 HbT]

[ Hb]

[

(blood) (blood)

O O (blood)

O bv O

bv (blood) (blood)

) blood ( 2 0

) blood ( 2 0 O

bv (blood) (blood)

) blood ( 2 0

bv bv (blood)

(blood)

O bv (blood) )

blood ( 2 0 (blood) bv

(tissue)

2 2 (blood) 2

2 bv O

2

(blood) 2 bv O

2

(blood) 2 bv O

2











 - D



 D



























 +

 - + 











 D-

















 - + 











 + D D

































 - -

 D

- -

-

c c c

L V e

c

V e c

L e c V

V

c L c

L c

L



[S. Fantini, Phys. Med. Biol. 47, N249 (2002)]

(50)

Concurrent fMRI and fNIRS

(51)

Comparison of BOLD and NIRS mapping

-0.14 mM 0.06 mM

15

11

C D

(a) fMRI-BOLD

D[Hb]

Optical detector Light source

Right hand tapping

3 2

D C

B A

1 4

5

6 7 8

9 11 10

12 13

14 15 16

detector source

L R

(52)

Weighted average of BOLD signal according to photon-hitting density function

k = 0.3 mm^-1

(m_a=0.020 mm^-1, m_s'=1.5 mm^-1)

Fig.5 11

C

BOLD Activation

Photon-hitting density function

(53)

NIRS:

-0.2

Left hand tapping

-0.08

D[Hb]

D[HbO]

fMRI: BOLD

_PMA

-D[HbO] (mM) -0.09

-BOLD_PMA (%)

-1.7 -0.17

D[Hb] (mM) -0.002

BOLD

_PMA

and NIRS maps (Right side): Comparison at t = 6 s

(54)

Comparison of BOLD _PMA and NIRS Signals: Temporal correlation

-1.0E-01 0.0E+00 1.0E-01 2.0E-01 3.0E-01 4.0E-01 5.0E-01 6.0E-01

0 10 20 30 40

time (sec)

AU

Hb-B3 HbO-B3 BOLD-B3

-1.0E-01 0.0E+00 1.0E-01 2.0E-01 3.0E-01 4.0E-01 5.0E-01 6.0E-01

0 5 10 15 20 25 30 35 40

tim e (sec)

-1.0E-01 0.0E+00 1.0E-01 2.0E-01 3.0E-01 4.0E-01 5.0E-01 6.0E-01

0 10 20 30 40

time (sec)

AU

-1.0E-01 0.0E+00 1.0E-01 2.0E-01 3.0E-01 4.0E-01 5.0E-01 6.0E-01

0 10 20 30 40

time (sec)

Left hand tapping

(55)

Principi della spettroscopia nel

Department of Biomedical Engineering

Tufts University, Medford, Massachusetts, USA