VP.Org November 16, 2002

Mitchell W. Krucoff, MD, FACCAssociate Professor Medicine/Cardiology

Duke University Medical CenterDirector, Interventional Devices Clincal Trials

Duke Clinical Research Institute

Discrimination of Ex Vivo Discrimination of Ex Vivo Lipid-Rich Plaques in Lipid-Rich Plaques in

Human Aorta Specimens Human Aorta Specimens with NIR Spectroscopy with NIR Spectroscopy through Whole Bloodthrough Whole Blood

B.Marshik, H.Tan, J.Tang, A. Zuluaga, B.Marshik, H.Tan, J.Tang, A. Zuluaga, A. Lindquist, P.R.Moreno, A. Lindquist, P.R.Moreno,

K.R.Purushothaman, K.R.Purushothaman, W.O’Connor, G.TearneyW.O’Connor, G.Tearney

First results on First results on fresh human tissue fresh human tissue samples through samples through variable depths of variable depths of

bloodblood(updated from TCT 2002 (updated from TCT 2002

poster)poster)

Tissue Evaluation by NIR Tissue Evaluation by NIR SpectroscopySpectroscopy

Absorbance of NIR light varies by wavelengthAbsorbance of NIR light varies by wavelength Absorbance patterns (spectra) unique for different Absorbance patterns (spectra) unique for different chemicalschemicals

Reflection patterns (spectra) unique for different chemicalsReflection patterns (spectra) unique for different chemicals

NIR Spectra of Human Aorta NIR Spectra of Human Aorta SamplesSamples

Source: Infraredx, 2002

Normal 1

Normal 2

Plaque 1

Plaque2

Cholesterol

Collagen

Wavelength

(Int

ensi

ty)

NIR Spectra of Human Aorta NIR Spectra of Human Aorta SamplesSamples

Source: Infraredx, 2002

Normal 1

Normal 2

Plaque 1

Plaque2

Cholesterol

Collagen

ChemometricsChemometrics Set of methods to predict chemical properties of unknown Set of methods to predict chemical properties of unknown samples using spectroscopy and linear algebrasamples using spectroscopy and linear algebra

Commonly used in pharmaceutical, chemical and food Commonly used in pharmaceutical, chemical and food processing; also being applied to glucose monitoringprocessing; also being applied to glucose monitoring

Spectra fromknown

samples

Histology fromknown

samples

Correlation betweenspectral features and

histology

Prediction Model

Calibration Method

Prediction Method

Spectra fromunknownsamples

Prediction ModelPredictedHistology(Sens/Spec)

Advantages of NIR Spectroscopy + Advantages of NIR Spectroscopy + Chemometrics for Coronary TCFA Chemometrics for Coronary TCFA

DetectionDetection Identifies chemical Identifies chemical composition of vessel wall composition of vessel wall specificity and sensitivity > 85%specificity and sensitivity > 85% potential to guide therapiespotential to guide therapies

3.2Fr coronary catheter 3.2Fr coronary catheter compatiblecompatible

Works fast – insensitive to Works fast – insensitive to motionmotion

Chemometrics discriminates Chemometrics discriminates chemical composition chemical composition independent of blood depth independent of blood depth no flushing neededno flushing needed no tissue contactno tissue contact

Near Infrared (NIR) SpectroscopyNear Infrared (NIR) SpectroscopyPrevious ReportsPrevious Reports

1.1. Cassis, Lodder (1993)Cassis, Lodder (1993) Discrimination of lipid-filled and normal rat aorta tissue Discrimination of lipid-filled and normal rat aorta tissue

specimensspecimens2.2. Jaross (1999)Jaross (1999)

Determined cholesterol content in human aorta tissue Determined cholesterol content in human aorta tissue specimensspecimens

3.3. Moreno (2002)Moreno (2002) Identified lipid pool, thin cap, and inflammatory cells in Identified lipid pool, thin cap, and inflammatory cells in

human aorta tissue specimenshuman aorta tissue specimens4.4. Wang (2002)Wang (2002)

Analyzed lipid and protein content in carotid Analyzed lipid and protein content in carotid endarterectomy specimensendarterectomy specimens

5.5. Neumeister, Jaross (2002)Neumeister, Jaross (2002) Determined cholesterol and collagen content in human Determined cholesterol and collagen content in human

aorta tissue with NIR spectroscopyaorta tissue with NIR spectroscopy

LimitationsLimitations: Not through blood, room temperature, : Not through blood, room temperature, fixed probe-target distance, tissue fixed or fixed probe-target distance, tissue fixed or frozen/thawed (except Wang)frozen/thawed (except Wang)

Study PurposeStudy Purpose

NIR spectroscopy and NIR spectroscopy and chemometrics:chemometrics: discriminate large lipid pool discriminate large lipid pool

specimens from other tissue specimens from other tissue typestypes

using fresh human arterial tissueusing fresh human arterial tissue through variable amounts of through variable amounts of

bloodblood

InstrumentationInstrumentation

FOSS NIRSystems Model 6500FOSS NIRSystems Model 6500 ½” diameter fiber optic ½” diameter fiber optic

SmartProbe™ SmartProbe™ Central fiber delivery bundle Central fiber delivery bundle Outer fiber collection bundleOuter fiber collection bundle

Broad spectral range: 400 to Broad spectral range: 400 to 2500 nm.2500 nm.

Sixty seconds for spectral Sixty seconds for spectral acquisitionacquisition

TissueTissue

Human Aorta TissueHuman Aorta Tissue Aorta from 72 human subjects (avg age 69.6 Aorta from 72 human subjects (avg age 69.6

±12.8)±12.8) 751 tissue specimens cut to 2x2 cm from 751 tissue specimens cut to 2x2 cm from

diseased and non-diseased sites diseased and non-diseased sites Stored in phosphate buffered saline solutionStored in phosphate buffered saline solution Shipped on wet ice less then 24 hours after Shipped on wet ice less then 24 hours after

autopsyautopsy

NIR MethodNIR Method Tissue placed on Tissue placed on rubber mat in glass rubber mat in glass dishdish

Blood and tissue at Blood and tissue at 38°C38°C

NIR spectra NIR spectra acquired at probe-to-acquired at probe-to-tissue separations tissue separations 0.0, 0.25, 0.5, 1.0, 1.5, 0.0, 0.25, 0.5, 1.0, 1.5,

2.0, 2.5 and 3.0 mm2.0, 2.5 and 3.0 mm Probe on z-stage Probe on z-stage

micrometermicrometer

FOSS Probe

Plaque TissueSampleRubber Mat

Blood Depth

Bovine Blood

Tissue Pins

Broadband Light SourceDetector

Data Acquisition Computer

Four Tissue ClassificationsFour Tissue Classifications1 mmNormal

Fibrotic

Lipid Calcific

HistologyHistology Fixed tissueFixed tissue Analyze probe Analyze probe illumination areaillumination area

Stained sub-sections Stained sub-sections with H&E and elastic with H&E and elastic trichrometrichrome

Microscopic Microscopic planimetry and planimetry and morphology to morphology to characterize tissue characterize tissue contentcontent Methods of AFIPMethods of AFIP

A3

B1

B2

B3

C1

Plaque CriteriaPlaque Criteria High LipidHigh Lipid

LP / PL ≥ 40%LP / PL ≥ 40% FIB / PL ≤ 35%FIB / PL ≤ 35% CAL / PL ≤ 5%CAL / PL ≤ 5%

High FibroticHigh Fibrotic FIB / PL ≥ 35%FIB / PL ≥ 35% LP / PL ≤ 35%LP / PL ≤ 35% CAL / PL ≤ 5%CAL / PL ≤ 5%

High CalcificHigh Calcific CAL / PL ≥ 20%CAL / PL ≥ 20% LP / PL ≤ 35% LP / PL ≤ 35% ≤ ≤ 35%35%

Plaque SelectionPlaque Selection

DiseaseDiseaseTypeType

SPECIMENSPECIMENSS

in Modelin ModelAORTASAORTASin Modelin Model

Lipid Lipid 3636 1919

FibroticFibrotic 2525 1515

CalcificCalcific 4444 2020

Normal Normal TissueTissue 4141 4141

Example Spectra – 0 and 3 Example Spectra – 0 and 3 mmmm

.5

1

1.5

2

2.5

3

400 600 800 1000 1200 1400 1600 1800 2000 2200 2400

0.0 mm Normal3.0 mm0.0 mm Fibrotic3.0 mm0.0 mm Lipid Pool3.0 mm0.0 mm Calcific3.0 mm

Wavelength (nm)

ABS.

Chemometric ModelChemometric Model

-1-0.8-0.6-0.4-0.200.20.40.60.81

Chemometric Prediction Score

SPECIFICITYSENSITIVITY

-1-0.8-0.6-0.4-0.200.20.40.60.81

Distribution of Lipid-Rich Atheromas at all

blood depths

Threshold / Criterion

Distribution of other tissue types at all

blood depths

Classification DistributionsClassification Distributions

-1.5-1-0.500.51

Lipid Pool CalcificFibrotic Normal

Threshold

SENS SPEC

Summary Prediction Summary Prediction ResultsResults

NIR (+) NIR (-) Results

(a)

Lipid Pool Lipid Pool (+)(+) 164164 1616 SensitiviSensitivi

ty: 91%ty: 91%No Lipid Pool No Lipid Pool

(-)(-) 6666 484484 SpecificitSpecificity: 88%y: 88%

0 mm 0.25 mm

0.5 mm

1.0 mm

1.5 mm

2.0 mm

3.0 mm

SENSENSS

8686%% 92%92% 92%92% 94%94% 92%92% 83%83% 86%86%

SPESPECC

8888%% 87%87% 87%87% 90%90% 87%87% 85%85% 72%72%

Sample-to-Probe Depth Sample-to-Probe Depth PredictionsPredictions

0.0 mm 0.25 mm 0.5 mm 1.0 mm 1.5 mm

2.0 mm 3.0 mmSENSSENS SPECSPEC

ConclusionsConclusions NIR can discriminate atherosclerotic NIR can discriminate atherosclerotic plaque lipid poolsplaque lipid pools through variable blood depthsthrough variable blood depths with high sensitivity and high specificitywith high sensitivity and high specificity

Study illustrates the potential Study illustrates the potential clinical feasibility of near-infrared clinical feasibility of near-infrared spectroscopy to detect vulnerable spectroscopy to detect vulnerable plaque in perfused coronary arteries.plaque in perfused coronary arteries.

Ongoing workOngoing work Reproduce results with ex vivo Reproduce results with ex vivo

coronary tissue through bloodcoronary tissue through blood Complete prototype console with 5 Complete prototype console with 5

msec spectral acquisitionmsec spectral acquisition Overcomes motionOvercomes motion

Complete prototype human use Complete prototype human use catheter with 2.5 mm optical catheter with 2.5 mm optical penetration depthpenetration depth

Begin human studies – To Begin human studies – To discriminate disrupted plaques from discriminate disrupted plaques from normal tissues through bloodnormal tissues through blood

VP.Org VP.Org November 16, November 16,

20022002Mitchell W. Krucoff, MD, Mitchell W. Krucoff, MD,

FACCFACCAssociate Professor Associate Professor Medicine/CardiologyMedicine/Cardiology

Duke University Medical CenterDuke University Medical CenterDirector, Interventional Devices Director, Interventional Devices

Clincal TrialsClincal TrialsDuke Clinical Research InstituteDuke Clinical Research Institute