Perfusion PET • Metabolic PET (Viability) • Hybrid Imaging ... PET Coronary CTA... · Why PET Perfusion? • Better spatial & temporal resolution: Small hearts, large patients.

Agenda

• Perfusion PET• Metabolic PET (Viability)• Hybrid Imaging (PET/CTA)

Progression of Atherosclerosis

Adapted from Abrams J. N Engl J Med. 2005;352:2524-2533.

SPECT

Why PET Perfusion?

• Better spatial & temporal resolution: Small hearts, large patients.

• Improved diagnostic accuracy, lower false positive.

• Identification of multivessel ischemia.• Accurate depth-independent attenuation

correction.• Faster protocols.• Lower radiation burden.• Quantification capabilities.

SPECT vs PET Perfusion

• Energy: 78-140 KeV• Attenuation correction:

sometimes• Stress: exercise,

pharmacologic• Protocol, start to finish:

2–2/12 hours• Ventricular function: post-

stress, rest

• 511 KeV• Attenuation correction:

always• Stress: pharmacologic,

exercise in future (F-18)• Protocol, start to

finish:30–45 minutes• Ventricular function:

stress, rest

SPECT PET

Radiation Exposure (mSv) PET vs SPECT

Myocardial Blood Flow and Radiotracer Uptake

PET Cardiac Radiotracers

PET Perfusion for Detecting CAD

Author Sensitivity Specificity # Patients

Gould 95% 100% 50Demer 94% 95% 193Go 93% 78% 202Schelbert 97% 100% 45Yonekura 93% 100% 49Williams 98% 93% 146Stewart 84% 88% 319Weighted Avg.

93% +/- 8 92% +/- 5 766

Freedom From Any Cardiac Events Following Rb-82 Myocardial Perfusion PET

Yoshinaga K et al. J Am Coll Cardiol. 2006;48:1029.

Characteristics of a NormalMyocardial Perfusion PET Study

• Uniform distribution of tracer, independent of gender

• LV cavity at peak stress equal to/smaller than at rest

• Uniform and normal wall thickness and thickening

• Uniform and normal regional wall motion

• Peak stress LVEF > rest LVEF

N13-Ammonia PET Images

Characteristics of an AbnormalMyocardial Perfusion PET Study

• Decrease in regional tracer uptake at peak stress

• LV cavity at peak stress larger than at rest • Frequent regional contraction abnormality

(stunning) at peak stress• Peak stress LVEF < rest LVEF

Abn

orm

al N

-13

perfu

sion

stu

dy

72 year old man with peripheral vascular disease.

Coronary arteriography:•LAD: 60% ostial and 80% mid vessel stenoses•LCX: 90% proximal stenosis and occluded OM•RCA: 90% ostial stenosis

Abn

orm

al N

-13

perfu

sion

stu

dy

Multivessel DiseaseIschemia + Transient Dilatation

PET Perfusion/Metabolic Imaging Protocols

Transm. Rest ExercisePharm.

Stress

DipyridamoleAdenosineDobutamine

13N-ammonia82Rb

13N-ammonia82Rb 18F-FDG

MetabolicImaging



SPECT

PETEndothelial dysfunction

Severe ischemia

PET PerfusionQuantification of Myocardial Blood Flow

Rest

Stress

LAO

RAO

Control of Coronary Blood Flow

ConductanceVessel

ConductanceVessel

Resistance Vessels

Resistance Vessels

FF

Vascular Smooth Muscle Cell


Shear StressShear Stress

Endothelial CellEndothelial Cell

Hyperemic FlowHyperemic Flow

Normal Responseabout 10-20% diameter increase

Normal Responseabout 10-20% diameter increase

• Length of Vessel (L)

• Flow Velocity (V)

• Diameter of Vessel (D; 4th power)




Resistance to FlowResistance to Flow

Conductance VesselConductance Vessel

Hyperemic FlowHyperemic Flow







Resistance to FlowResistance to Flow

Abnormal Responseno change or decrease in diameter

Abnormal Responseno change or decrease in diameter

Conductance VesselConductance Vessel

Control of Coronary Blood FlowResistance Vessels

< 400µm< 400µm

CoronaryBloodFlow

CoronaryBloodFlow

AdenosineDipyridamolePapaverine

Shear StressShear Stress

Endothelial CellEndothelial Cell



Glagov et al, N Engl J Med 1987; 316:1371Glagov et al, N Engl J Med 1987; 316:1371

Compensatory Expansion Maintains Constant LumenCompensatory Expansion Maintains Constant Lumen

As Atherosclerosis Progresses,the Artery Usually Compensates by Dilating

As Atherosclerosis Progresses,the Artery Usually Compensates by Dilating

Expansion Overcome:Lumen Narrows

Expansion Overcome:Lumen Narrows

Conductance and Resistance Vessel InteractionConductance and Resistance Vessel Interaction

00

% Flow Index Change% Flow Index Change

% Luminal Area

Change

% Luminal Area

Change

3030

4040

00 200200

n = 11r = 0.79p < 0. 01

n = 11r = 0.79p < 0. 01

1010

2020

300300 400400 500500 600600 700700 800800

Zeiher et al., Circulation 1991; 84:1984-92Zeiher et al., Circulation 1991; 84:1984-92

Arterial Tracer Input Function and Changes inMyocardial Tracer Concentration

ActivityConcentration

(cts / pixel / sec)

ActivityConcentration

(cts / pixel / sec)MyocardiumMyocardium

Time (sec)Time (sec)120120100100808060604040202000

00

11

22

33

44

55

Arterial BloodArterial Blood

Clinical Value Long Term KnownMBF in Kawasaki Disease

Muzik et al, J ACC Vol 28; 3:757-62, 1996

Rest

0

100

Myo

card

ial B

lood

Flo

w(m

l/100

g/m

in)

Adenosine

Controln = 10

Kawasakin = 10

200

300

400

500

Rest Adenosine

p = 0.01

0

10

20

30

40

50

0

10

20

30

40

50

SDSD

NSNS P <0.05P <0.05

Perc

ent I

ncre

ase

Perc

ent I

ncre

ase

RPPRPP

BaselineBaseline On TreatOn Treat Off TreatOff Treat

MBFMBFP <0.05P <0.05

BaselineBaseline On TreatOn Treat Off TreatOff Treat

Clinical Value Long Term KnownTherapy MBF Changes in Insulin Resistance

Clinical Value Long Term KnownTherapy MBF Changes in Insulin Resistance

Quinones et al, Ann Int Med 2004:140:700-708

Herzog et al. JACC 2009;54:150-156.Herzog et al. JACC 2009;54:150-156.

Long Term Prognostic Value PET PerfusionAdded Value of Coronary Flow Reserve

Quantitative PET

• Serial PET imaging is validated, reproducible approachto quantify non-invasively myocardial blood flow at restand during stress in healthy individuals and patientswith heart disease

• The effects of pharmacological interventions, drugeffects, noxious stimuli or life style modificationprograms on myocardial blood flow and flow reservecan be measured

• The effects of physiologic processes such as agingcan be evaluated in humans

• The hemodynamic significance of coronary arterydisease can be estimated

Why Is PET More Suitable to Follow Pro/Regression of CAD

• Coronary blood flow is a function of the arterial radius raised to the fourth power

• Small changes in diameter not measurable by anatomic imaging are magnified into much larger changes in blood flow readily quantifiable by PET

• Changes in PET perfusion can be seen in 40–90 days after intense risk factor treatment is begun

Gould KL. J Nucl Cardiol. 2005;12:625-638.

Agenda


Duke DatabaseMedical therapy vs. CABG

0

100

75

50

2510 y

ear s

urvi

val,

%

Circulation 1992

Medical MedicalMedical SurgicalSurgicalSurgicalEF >50% EF <35%EF 35-50%

65%74%

56%

62%

27%

50%

Viability PET StudyChronic LVEF Dysfunction

• Traditionally the gold standard

• Two sets of resting images to detect viable and hibernating myocardium:

• Perfusion image (usually with N-13 ammonia or rubidium-82)

• Glucose metabolic image (with F-18 fluorodeoxyglucose = FDG)

OH

HO

HO

HO

18F

Myocyte FDG UptakeNormal Myocyte Ischemic Myocyte

Glucose 6-phosphatase

Hexokinase


G6PD-

Glucose

GlycolyticPathway

D-Glucose

X

FFA


Hexokinase


FDG-6-P

G6P

GlycolyticPathway

D-Glucose

XFDGFDG

D-Glucose

FDG-6-P

FDG

FDGFDG

FDGFDG

FDGFDG

FDG

FDG

FDG

FDG

FDGFDG

FDG

FFA FFA

FFA

FFA

FFA

FFA

FFA

FFA

FFA

FFA

FFA FFA

FFA FFA

FixedFixed

FixedFixed

Partially ReversiblePartially Reversible

Partially ReversiblePartially Reversible

MatchMatch

MismatchMismatch

StressStress RestRest

FDGFDGNH3NH3

MatchMatch

MismatchMismatch

PET Myocardial Viability

PET viability protocolsTraditional semi-quantitativeflow/metabolism match-mismatchfollowing oral glucose load

Quantitative measurement (HH) of FDGuptake during glucose clamp

Circulation 1996; 93: 737-744J Clin Invest 1996; 98: 2094-2099

Impr

ovem

ent

(%)

Di Carli M et al, Circulation 1995;92:3436-44.

0

100

200

0 20 40 60 80Extent mismatch (%LV)

r=0.87,SEE=10.8P<0.001

PET ViabilityImproved symptoms of CHF

18%

Multivessel CADMean LVEF = 28±6%

Beanlands R et al: JACC 50:2002, 2007Beanlands R et al: JACC 50:2002, 2007

0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250 300 350 400DaysDays

ADHERE armADHERE arm

Standard armStandard arm

PARR-2PET-guided Therapy vs Standard Care

Event-free

survival

Event-free

survival

p = 0.019

Agenda


Hybrid PET/CTA: Myocardial Perfusion and Function

Cardiac Perfusion

Concurrent Rest & Peak Stress

FunctionCTA

Coronary Calcium

Assessment



SPECT

PETEndothelial dysfunction

Severe ischemia

CT Coronary angiography

SPECT Underestimates Disease Burden: Stable CAD

Calcium score: 890

Relationship of Stress-Induced Ischemia and Atherosclerosis (CAC)

Berman DS et al. J Am Coll Cardiol. 2004;44:923-930.

Distribution of the normal MPS studies (N=1,119)

0

1-9

10-99

100-399

400-999

1000

Distribution of the ischemic MPS studies (N=76)CAC score

5%

0 %

7 %

20 %

29 %

39 %

22%

4 %

18 %

25 %

20 %

11 %

Why use PET/CTA ?• Non invasive.• Offer high diagnostic accuracy.• Monitor the course of disease.• Allow quantification of myocardial blood flow and

coronary reserve.• Detect early functional abnormalities.• Monitor consequences of lifestyle modifications.

Rest-Stress PET Rubidium-82 and CTA Protocol

0:00 min 0:30 min

Study Effective Radiation (mSv)

PET

F-18 FDG (370 MBq) 7.0

N-13 NH3 rest/stress (2X 550 MBq) 2.2

Rb82 rest/stress (2 x 740 MBq) 3.6

H2O-15 rest/stress (2 x 740 MBq) 1.4

Transmission Ge-68 rod source 0.08-0.13

MSCT

Calcium Scoring 0.7-6.2

CT angiography 3.7-13.0

CT based PET attenuation correction 0.23-5.66

Effective Radiation Dose for Cardiac PET/CT Studies

Schenker, M. P. et al. Circulation 2008;117:1693-1700

Prognosis of Cardiac Events by PET-CTAdded Value of CAC

Kajander, S. et al. Circulation 2010;122:603-613

Hybrid PET/CTA: Myocardial Perfusion and Function

PET and CTA Complement Each Other

• Calcium (blooming)• Stents• Limited spatial resolution, <1.5-mm vessels• Overestimation of stenosis• Positive predictive value MDCT ~50%• Clinical outcomes data• Preclinical disease

Abnormal CT Angiography: Limited Positive Predictive Value

Discordance Between Noninvasively Determined Anatomic and Functional Measures of Atherosclerosis

• Percent stenosis a moderate descriptor of coronary resistance– Stenosis difficult to estimate with soft plaque

• Coronary vasodilator reserve integrates coronary epicardial and microvascular function

• Noncoronary causes of myocardial damage

PET CTA Diagnosis Potential Strategy

Normal Normal No CAD Discharge

Normal Abnormal Non-significant CAD

Medical Tx & Follow-up

Abnormal Abnormal Significant CAD

Medical Tx & Consider Cath

Abnormal Normal Coronary microvasculardysfunction

Risk ProfileModification & Consider Antianginal Tx

Scenarios in Cardiac PET/CT imaging for (suspected) Coronary Artery Disease

Lautamaki, R. et al. Circ Cardiovasc Imaging 2009;2:299-305

Infarct size measurement

Beeres, S. L.M.A. et al. J Am Coll Cardiol 2007;49:1137-1148

The Next Thing is….Tracking of Genetically Labeled Progenitor Cells by PET

Changes Coming With Hybrid ImagingNuclear Cardiology Evolution

• PET-CT:Comprehensive evaluation of CADPerfusionFunctionViabilityVulnerable Plaque Assessment (FDG ?)

Take Home Message

• Excellent sensitivity and prognosticator,CAD, severe LV dysfunction.

• Integrates function and morphology, PET/CTA.

• Unsurpassed ability to calculate MBF in preclinical and during therapy.

• Unlimited molecular imaging capabilities to target specific pathophysiology questions.

Perfusion PET • Metabolic PET (Viability) • Hybrid Imaging ... PET Coronary CTA... · Why PET Perfusion? • Better spatial & temporal resolution: Small hearts, large patients.

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