Advances in Nuclear Cardiology

Matthew Schumaecker, MD, FACC, FASNC

Medical Director, Nuclear Cardiology

Carilion Clinic Cardiology

Assistant Professor of MedicineVirginia Tech Carilion School of Medicine

Educational Objectives

• Review advances in nuclear cardiology in:• Novel radiopharmaceuticals• Advances in camera software and hardware• Molecular imaging

Very Brief History of Nuclear Cardiology

• 1958 Scintillation Camera: Hal Anger

• 1972 Thallium 201

• 1976 SPECT camera: Keys, Jaszczak

• 1984 Cardiac PET Rb-82

• 1996 Cardiolite® (sestamibi) approved

Current State

• Most nuclear cameras in use are the same technology from 1970’s

• Sestamibi has been on the market for over 17 years

• Thallium mostly gone • MRI has replaced MUGA as gold standard

for LVEF assessment• PET imaging only in large academic centers

PET

• Advantages of PET over SPECT• Higher energy resolution • Mandatory attenuation correction• Quantification of coronary blood flow

• Disadvantages of PET over SPECT• Camera is MUCH more expensive• Radioisotopes are very short-lived

SPECT vs PET

Tc99m

140 keVɣray

F18

E=mc2

511keVphoton

511keVphoton

e-

β+

18F-Flurpiridaz PET

• Half life of currently utilized cardiac PET perfusion agents:

Agent T1/2

N-13 132 seconds

O-15 148 seconds

Rb-82 75 seconds

18F-Flurpiridaz PET

• 18F Fludeoxyglucose has t1/2 of 110 minutes

BUT

• This is a viability agent, not a perfusion agent

18F-Flurpiridaz PET

Jamshid Maddahi, M.D., FACC, FASNC, and René R. S. Packard, M.D.

123I-BMIPP

• 99mTc can be used to evalulate chest pain at rest but only if patient is having pain at the time.

Cardiac Memory

• Myocytes preferentially metabolize FFA

• In ischemia millieu, switch to glycolysis

Cardiac Memory

• Substrate switch can last up to 24 hours

• If injected with 123I-BMIPP, SPECT images will show defect if patient has been ischemic within 24 hours

Dilsizian et al, Circ 2005;112:2169-2174

BMIPP Trial

J Am Coll Cardiol. 2010 Jul 20;56(4):290-9

123I-MIBG

• MIBG is a sympathetic neurotransmitter radionuclide analog

• Cardiac uptake of MIBG is assessed by heart/mediastinal ratio.

• Correlates to heart failure severity, pre-disposition to cardiac arrhythmias, and poor prognosis

123I-MIBG

• As CHF progresses, there is a reduction in the number of presynaptic neurons and the function of the norepinephrine terminal resulting in decreased uptake of mIBG.

• Therefore, lower H/M ratios confer a more negative prognosis

123I-MIBG

Yazaki et al. Cardiomyopathies Chap 11

123I-MIBG ADMIRE-HF Trial

Jacobson et al J Am Coll Cardiol. 2010;55(20):2212-2221

 ”Two-year event rate was 15% for H/M ≥1.60 and 37% for H/M <1.60”

123I-MIBG ADMIRE-HF Trial

Jacobson et al J Am Coll Cardiol. 2010;55(20):2212-2221

123I-MIBG

> $1000 per dose No reimbursement in US

SPECT/CT

Gaemperli et al, Journal Nuc Med May 2007; 5:696

FBP vs OSEM

• Filtered backprojection suppresses high-frequency image data thereby decreasing noise. This causes image blurring and subjects the image to ramp filter artifact

• Iterative reconstruction provides an estimated reconstruction volume and compares it to image. This occurs until images converge

Depth DependentResolution Loss

Depth DependentResolution Recovery

• Wide beam reconstruction suppresses noise and enhances signal-to-noise ratio by modeling the statistical characteristics the collimator detector response.

• Statistical filters using Gaussian and Poisson Fourier transforms allow the deeper voxels to appear as they were closer, thereby eliminating DDRL

Depth DependentResolution Recovery

Depth DependentResolution Recovery

Hardware: Optimized Detector Geometry

Hardware: Optimized Detector Geometry

Solid State Detectors

Attenutation Correction

Two ways to do AC:

Attenutation Correction

Prone Imaging

• Shifts the heart off the diaphragm and places breasts in different position.

• Not as valuable as attenuation correction

• BUT – added counts in prone imaging are always real

Molecular Imaging

• Two major targets:• Vulnerable Plaque• Cardiac remodeling

Potential Targets

• IL-6

• VCAM – 1

• LT B4

• Matrix metalloproteases

• Cathepsins

• Anti-myosin antibodies

• Beta receptors

• ACE receptors

Apoptosis

Nahrendorf M et al. Circ Cardiovasc Imaging 2009;2:56-70

Copyright © American Heart Association

Atherosclerosis imaging

Nahrendorf M et al. Circ Cardiovasc Imaging 2009;2:56-70

Copyright © American Heart Association