Progress Report for NIR Spectroscopy Studies

November 7, 2000

Tania KhanMohammed Asif, M.D.Silvio Litovsky, M.D.

Morteza Naghavi, M.D.

Progress• New probe design being worked out with Multimode to

improve NIR signal 10/31- current– Data analysis of all prior spectra required in progress– Characterize new light source in same manner (configurations,

reference standards, sampling methods)– Must send out on order before AHA next week

• Ongoing difficulties in working on a depth penetration study

• Tissue phantom study needed for pH • Experimental setup issues: time, temperature,

physiological maintenance, digital camera, etc.

Plaque 10/31

1

2

3

4

5

2.5 cm

1 cm

Data

1

2

3

4

50.1 mm thickpH 7.6334.6°C0.3 mm thick

pH 8.0832.9°C

0.4 mm thickpH 7.4132.5°C

0.6 mm thickpH 8.0834.2°CThrombosed/Calicified area? 0.6 x 0.5 cm

0.7 mm thickpH 8.2532.1°CCalcified hard area

4x

10x40x

HA-2-1

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

400 600 800 1000

wavelength

abso

rban

ce

HA-2-2

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

400 500 600 700 800 900 1000 1100

wavelength

abso

rban

ce

4x

10x40x

HA-2-3

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

400 500 600 700 800 900 1000 1100

wavelength

abso

rban

ce

4x

10x40x

HA-2-4

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

400 500 600 700 800 900 1000 1100

wavelength

abso

rban

ce

4x

40x

Very calcified,Should have put in De-CalSolution more than 1 hr.

HA-2-5

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

400 500 600 700 800 900 1000 1100

wavelength

abso

rban

ce

4x

40x10x

All Areas

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

400 500 600 700 800 900 1000 1100

wavelength

abso

rban

ce

VIS HA-2-5 I-M VIS HA-2-4 HA-2-3 VIS HA-2-2 HA-2-1

Fibrosis, necrosis, calcifications are all qualitativeOnly 5 points, no pH correlation can be made

Environmental condition stabilization needs to be improvedQuantify degree of surface roughness for spectra collection

CONCLUSIONS• New light source changes relative absorbance

– Light source must be characterized (configurations, reference standards, etc.)

• Tissue penetration unresolved with histology– Penetration study must be completed with new light source

• Histology and other experimental setup issues unresolved; temperature, other physiological, morphological variables

• Need quantitative measurements of histology– Cap thickness, size of necrotic core, cell density, etc.

• New probe needed to reach wavelengths above 1900 nm (lactate region) ; spectrometer OK– Currently being designed with help from Mulitmode Inc.

PRIORITIES1. Analyze data to see what would be best to

incorporate in a new probe design to get better spectra out past 1900 nm (water bands, lactate bands, cholesterol bands)

2. Characterize light source3. Conduct depth penetration study4. Conduct tissue phantom study (pH, lactate,

thrombus?)5. Fix experimental setup issues6. Start tissue pH spectroscopy of human carotid

plaques study