plaque characterization and perfusion
TRANSCRIPT
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Plaque Characterization: Non-Calcified, Calcified, Partially Calcified
Is that all CT can do?
Suhny Abbara, MD
Associate Professor, Harvard Medical School
Director Cardiac Imaging Fellowship, Massachusetts General Hospital
Disclosures
• Medical Advisory Board Member – Partners Imaging
– Perceptive Informatics
– Magellan Healthcare
• Consultant / Editing / Authoring (honoraria/options):– Amirsys, Inc.
• Research Agreement/Funding– BD Medical
– Bracco Diagnostics
• Member, Board of Directors (unpaid)– Certification Board of Cardiovascular CT (CBCCT)
– Society of Cardiovascular Computed Tomography (SCCT)
Iodinated Contrast not FDA approved for cardiac CT
Life History of Atheromas
Peter Libby. Nature 2002 (420): 868-874
Acute MI
Remodeling index:
Dp
Dn
“Vulnerable Plaque”
Narula et al. Nature clinical practice cardiovascular medicine. 2008 (5)S2.
Ruptured Plaque
Vulnerable Plaque
Characteristics of Vulnerable Plaques
• Plaque area
• Necrotic Core
• Inflammation
• Spotty Calcification
• Positive Remodelling
• Vasa Vasorum
• Hemorrhage
• Ulceration / Intraplaque Dye Penetation
Plaque Detection&
Area / Volume Quantification
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83 segments in 22 patients Sensitivity plaque per segment: 94% (all)
16-slice CT 53% (non-calcified)
Achenbach et al, Circulation 2003
58 vessels in 37 patients Sensitivity plaque detection: 85% (all)
16-slice CT 82% (non-calcified)
Leber et al, JACC 2004
36 vessels in 19 patients Sensitivity plaque detection: 90% (all)
64-slice CT 83% (non-calcified)
Leber et al, JACC 2006
685 segments in 45 patients Interobserver agreement: 93% (κ = 0.85)
16-slice CT (375 ms rotation)
Ferencik et al, JACC 2006
Coronary Plaque Detection: CT vs. IVUS
Courtesy Maros Ferencik
Partially Calcified
Plaque Calcification Types
Spotty calcificationNon calcified plaque
Calcified plaque Coarse calcification
Ex vivo
Coronary Arteries16 slice CT
Wall area
Ferencik et al. Radiology 2006
Measurements of Plaque Size
R = 0.67
Luminal area R = 0.92 Plaque area R = 0.55
* Moselewski et al. AJC 2004
In vivo:Plaque area
CT vs. IVUS“2D”
* Bamberg
Achenbach et al, Circulation 2004 Schepis et al, Heart 2010
Plaque volume
24 ± 35 mm3 vs. 43 ± 60 mm3
Plaque volume
89 ± 66 mm3 vs. 90 ± 73 mm3
In vivo: Plaque volume CT vs. IVUS “3D”
Courtesy Maros Ferencik
r=0.8, P<0.001
Remodeling Index
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Achenbach et al, JACC 2004
Remodeling Index
Coronary plaque characteristics in ACS and stable AP patients (n = 27)
Hoffmann et al, JACC 2006 Courtesy M. Ferencik, MGH
Culprit Lesions
in ACS (n=14)
Lesions in
SAP (n=13)p-value
Outer vessel area at
stenosis (mm2)21.2±7.0 15.6±10.5 0.01
Luminal area at
stenosis (mm2)3.7±1.6 2.1±1.4 0.18*
Plaque area (mm2) 17.5±5.9 13.5±10.7 0.02*
Degree of stenosis (%) 79.8±7.2 82.7±9.7 0.79*
RI 1.4±0.3 1.2±0.3 0.04
Plaque Volume / Remodeling Index
Prognostic Value?
Motoyama et al. JACC Vol. 54, No. 1, 2009 :49–57
Semi-quantitative Plaque Burden - Prognosis
0-5 vs. >5 of segments with plaque present
Min JK et al. JACC, 2007
N= 1127
All causemortality
<=5 SegmentsN=949
>5 SegmentsN=178
Low Attenuation Plaque
Napkin Ring Sign
Plaque Attenuation vs. IVUS
Motoyama. Circulation Journal Vol.71, 2007
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19 DEPARTMENT OF RADIOLOGY
Napkin-ring Sign: CT signature of high-risk coronary plaques?
Maurovich-Horvat P et al. JACCimg 2010 . Courtesy of CL Schlett, U Hoffmann
Cross Sections of a Coronary Plaque (Late Fibroatheroma)
Non-calcified plaque with a napkin-ring sign:
Low CT attenuation core (22.0 to 31.0 HU) &
Outer rim of high CT attenuation (35.0 to 76.0 HU).
Non-contrast enhanced CTA Contrast enhanced CTA Histopathology
Semiautomatic 3D Plaque Volume / Attenuation
Quantification
Voros S, et al. JACC-Intv 2011;4:198–208
Low Attenuation Plaque (LAP) Metrics
Prognostic Value?
Motoyama et al. JACC Vol. 54, No. 1, 2009 :49–57
ACS within
12 monthsNo ACS
Plaque Disruption
Ulceration and Intraplaque Dye Penetration
“Disrupted Plaques “
Madder, et al. Circ Cardiovasc Imaging. 2011; 4(2):105-13. Features of disrupted plaques by cCTA: correlates with invasively proven complex lesions.
ACP, CAC=0
CAC=0 Intraplaque Dye Penetration
Plaque Inflammation
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Potential Targets for Plaque Imaging
Libby et al. J Nucl Med May 2010; 51 (S1):33S-37
Molecular Imaging of Plaque Inflammation
Narula et al. Nature clinical practice cardiovascular medicine. 2008; (5)S2.
18F-FDG uptake indicates high cellular metabolic activity
� plaque inflammation
Stent for ACS. Inflammation
suggests culprit lesion was inflamed.Ahmed Tawakol, MGH
Indirect Plaque Inflammation Marker
Burdo, Lo, Abbara, Wei, Dorn, Preffer, Rosenberg, Subramanian, Tawakol, Williams, Grinspoon. The Journal of Infectious Diseases 2011. In Press.
Soluble CD163 (Monocyte/Macrophage Activation Marker)
is Associated with Noncalcified Coronary Plaque in HIV Patients
sCD163 levels correlated with # coronary segments with noncalcified plaque (r=0.23, p=0.02),
but not with # segments with calcified plaque nor Agatston calcium score.
Hyafil, Cornily, Rudd, Machac, Feldman, Fayad. JNuclMed June 2009;50(6): 959-65
Molecular Imaging of Inflammation -MDCT
• N1177 = iodinated nanoparticles dispersed with surfactant
• accumulate in macrophages
• atherosclerotic rabbit modelNative 2h post N1177
18F-FDG PET
3h post injection
Aortic enhancement N1177 + CT
Native 2h post N1177
Hyafil, Cornily, Rudd, Machac, Feldman, Fayad. JNuclMed June 2009;50(6): 959-65
Molecular Imaging of Inflammation - N1177
Immunohistochemistry
Axial slice corresponding to intense enhancement at N1177 CT
Strong macrophage infiltration
Axial slice corresponding to low enhancement at N1177 CT
Weak macrophage infiltration
Non-Calcified, Calcified, Partially Calcified
Is That All CT Can Do?
No CT can do much more:
• Positive Remodeling
• Area and Volume
• Low Attenuation
• Napkin Ring Sign
• Spotty calcification
• Ulceration and Intraplaque Dye Penetration
• Inflammation
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Non-Calcified, Calcified, Partially Calcified
Is That All CT Can Do?
But there are a few things CT cannot do:
• Identify “Thin Cap” in TCFA
• Intraplaque hemorrhage
• Vasa Vasorum
• Plaque Erosion
• Predict MACE vs. Asymptomatic Ruptures
Cardiac Function
Background
• Every retrospectively gated Coronary MDCT raw
dataset contains information about ventricular &
valvular function and myocardial perfusion
• Functional analysis requires additional
reconstruction of multiphasic datasets
• Perfusion analysis may be performed via post-
processing of the coronary CTA dataset (average weighted 5-10mm MPR)
Ventricular
Function
Multiple cardiac phases in one spatial location � cine images
Volumetric Ejection Fraction Calculation
• 4D workstation
• Threshold volumetric lumen detection
• Manual reference of mitral valve plane
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Wall ThickeningEF by 64-slice MDCT vs. SPECT
Bland-Altman Plot
Abbara S, Chow BJ, Pena A, et al. Assessment of left ventricular function with 16- and 64-slice multi-detector computed tomography. Eur J Radiol. 2008 Sep;67(3):481-6.
4D CT Ventriculogram Dyskinesia in LAD Territory � acute MI
Abbara S, Soni AV, Cury RC. Evaluation of cardiac function and valves by multidetector row computed tomography. Semin Roentgenol. 2008 Apr;43(2):145-53
Akinesia in RCA Territory - acute MI Regional Wall Motion Assessment
17 segment AHA classification – Cirquera et al. Circulation
apical
mid
base
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Regional Wall Motion Assessment
17 segment AHA classification
Navigating 4D Datasets
Navigating 4D Datasets
Comprehensive cCT analysis for ACS
• 102 patients, 34 AMI
• analyzed for myocardial perfusion defect (vs. SPECT & biomarkers), regional wallmotion defects (vs. TTE), and global LV function (vs TTE)
Cury RC, et al. Comprehensive assessment of myocardial perfusion defects, regional wall motion, and left ventricular function by using 64-section multidetector CT. Radiology. 2008 Aug;248(2):466-75.
Regional Wall Motion (RWM) - MDCT vs. TTE
Agreement between RWM by MDCT and:
• Clinical assessment of
AMI territory �K=0.82
• TTE (4-point scale, 17 myocardial
segments) � K=0.79Perfect agreement in 96% of segments (1664 out of 1734)
Cury RC, et al. Comprehensive assessment of myocardial perfusion defects, regional wall motion, and left ventricular function by using 64-section multidetector CT. Radiology. 2008 Aug;248(2):466-75.
54♂ 3 h substernal pain, pain relief after nitronegative 1st Troponin / CK-MB - non-diagnostic EKG
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54♂ 3 h substernal pain, pain relief after nitro
negative 1st Troponin / CK-MB - non-diagnostic EKG
RCALAD Occlusion
Functional Information from Cardiac CT
Perfusion Defect
RV
LV
54♂ 3 h substernal pain, pain relief after nitro
negative 1st Troponin / CK-MB - non-diagnostic EKG
Myocardial Akinesis
± LV thrombus
Culprit Lesion in LAD
Perfusion
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Hoffmann, U. et al. Radiology 2004;231:697-701
Porcine Infarct ModelLAD surgically ligated � non reperfusion infarct
Hoffmann, U. et al. Radiology 2004;231:697-701
Single phase
MDCT
TTC stained
gross pathology
Attenuation in infarcted area significantly lower than in normally perfused myocardium. p<0.01
Hoffmann, U. et al. Radiology 2004;231:697-701
Perfusion Imaging MRI vs. MDCT vs. Pathology
Mahnken Europ Rad 2005
MDCTMulti Phase
MRI
TTC stained
gross pathology
Single Perfusion Phase May Suffice
George et al. Investigative radiology (2007)
Acute MI
Nieman, Abbara, Cury et al, AHA 2005
Infarct size r = 0.73
MDCT DE-MRI
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Acute LAD Infarct Acute LCX Infarct
Delayed EnhancementMRI - DE CT perfusionCT - DE
Mahnken, JACC 2005
CT MRI
FIRST PASS
DELAYED
ENHANCEMENT
Microvascular Obstruction
Nieman et al.
N=21, 18male, 60 +/- 13 years
STEMI within 5days
MRI � FP, DE and CT � FP, DE
FP Perfusion
Defect Size
DE Microvascular
Obstruction Size
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Ruzsics, Lee, Powers, Flohr, Costello, Schoepf. Circulation 2008;117:1244-1245
Dual-energy CTIodine maps
80kV 140kV Dual Energy
Acute vs. chronic MI
Chronic MIChronic Infarct with Aneurysm
CT MRI
Contrast bolus60-80 cc
@ 4 cc/sec
AdenosinePerfusion
CT Scan
~5 minuteRecovery period
Contrast bolus60-80 cc
@ 4 cc/sec
Resting CTA
~10 minuteDelay
Delayed
CT
Stress/Rest Perfusion CT
Scan protocol, order, gating variations
Courtesy Brian Ghoshharjha, MGH
Stress Rest Delayed
Coregistered short-axis image sets
Stress Agent
Contrast
CT Procotol
Image Analysis
Courtesy Brian Ghoshharjha, MGH
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Blankstein, Okada, Ghoshhajra et al. In: Abbara, Walker. CardioVascular Images of the MGH
MGH Stress Perfusion CT ExperienceN=34; BMI 30.4+/-5
Stress perfusion CT, radionuclide imaging (MPI), conventional angiography
sens spec (cath >=50%)
pCT 79 80
MPI 67 83
sens spec (cath >=50% AND MPI defect)
pCT 79 80
12.7mSv average dose (stress,rest, AND delayed enhancement)
Blankstein et al.JACC, September 2009 15;54(12):1072-84
Mochizuki T, Radiology, Ehime Univ School of Med
ST (%)
Systolic Thickening
Systolic Thickening
hypohypo
StenosisStenosis
Tl SPECT
hypohypo
StenosisStenosis
MDCT
Courtesy Dr.
Thank you!
Thank you!