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