SHAPE Society

1. Progress Report for NIR
Spectroscopy Studies
November 7, 2000
Tania Khan
Mohammed Asif, M.D.
Silvio Litovsky, M.D.
Morteza Naghavi, M.D.

2. 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.

3. Plaque 10/31
1
2
3
4
5
2.5 cm
1 cm

4. Data
1
2
3
4
5
0.1 mm thick
pH 7.63
34.6°C0.3 mm thick
pH 8.08
32.9°C
0.4 mm thick
pH 7.41
32.5°C
0.6 mm thick
pH 8.08
34.2°C
Thrombosed/Calicified
area? 0.6 x 0.5 cm
0.7 mm thick
pH 8.25
32.1°C
Calcified hard area

5. 4x
10x
40x
HA-2-1
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
400 600 800 1000
wavelength
absorbance

6. 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
absorbance
4x
10x
40x

7. 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
absorbance
4x
10x
40x

8. 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
absorbance
4x
40x
Very calcified,
Should have put in De-Cal
Solution more than 1 hr.

9. 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
absorbance
4x
40x
10x

10. 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
absorbance
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 qualitative
Only 5 points, no pH correlation can be made
Environmental condition stabilization needs to be improved
Quantify degree of surface roughness for spectra collection

11. 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.

12. PRIORITIES
1. 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 source
3. Conduct depth penetration study
4. Conduct tissue phantom study (pH, lactate,
thrombus?)
5. Fix experimental setup issues
6. Start tissue pH spectroscopy of human carotid
plaques study