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Principles of Nuclear Cardiology
Thomas H. Hauser MD, MMSc, MPH, FACC
Director of Nuclear CardiologyBeth Israel Deaconess Medical Center
Assistant Professor of MedicineHarvard Medical School
Boston, MA
A major teaching hospital of Harvard Medical School
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Lecture Schedule9/8/2008 Introduction, Basic Physics Thomas Hauser, BIDMC
9/15/2008 Image Reconstruction Tony Parker, BIDMC
9/22/2008Tracers and Protocols Thomas Hauser, BIDMC
9/29/2008CAD Diagnosis and Prognosis Sharmila Dorbala, BWH
10/6/2008Assessment of Myocardial Viability Marcelo Di Carli, BWH
10/13/2008Columbus Day No Lecture
10/20/2008Attenuation Artifacts Thomas Hauser, BIDMC
10/27/2008Technical Aspects of Cardiac CT Suhny Abbara, MGH
11/3/2008Clinical Application of Cardiac CT Thomas Hauser, BIDMC
11/10/2008AHA No Lecture
11/17/2008Evaluation of Chest Pain with Cardiac CT Udo Hoffmann, MGH
11/24/2008Coronary Artery Plaque Mel Clouse, BIDMC
12/1/2008RSNA No Lecture
12/8/2008PET/CT Marcelo Di Carli, BWH
12/15/2008 "Triple Rule Out" CT Vassilios Raptopoulos, BIDMC
12/22/2008Radiation Dosimetry and Safety Thomas Hauser, BIDMC
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Advances in Nuclear Cardiology
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Advances in Nuclear Cardiology
Hachamovich et al, Circulation 2002;105:823-9
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Our Goal
• Image the heart
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Our Tools
• Tracers• Camera
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Outline• Tracers - Nuclear Physics
– Atomic structure
– Radioactive decay
– Specific radionuclides
• Camera - Gamma Camera – Collimators
– Energy selection
• Radiation Safety
Harvard Medical School
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Outline• Tracers - Nuclear Physics
– Atomic structure
– Radioactive decay
– Specific radionuclides
• Camera - Gamma Camera – Collimators
– Energy Selection
• Radiation Safety
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Atom
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Nucleus
• Proton– Charge +1
– Mass 1.00728 amu = 938 MeV
• Neutron– No charge
– Mass 1.00866 amu = 939 MeV
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E = m0c2
Energy can be converted to mass and vice versa
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Notation
Element SymbolAtomic Weight
{Atomic Number}
Oxygen = 16O = 15O
Carbon = 12C = 13C = 11C
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Definitions
• Nuclide– Specific combination of protons and neutrons (12C)
• Radionuclide– Nuclide that undergoes radioactive decay (11C)
• Isotopes– Nuclides that share the same number of protons
• Same element (identical chemical properties) but different mass
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Stable Nuclei
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Radioactive Decay
• Radioactive decay is the process by which unstable nuclei move towards the line of stability by emitting particles and/or photons and releasing nuclear energy
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Radioactive Decay
• Mother nucleus• Daughter nucleus• Emission
Emission
Mother Daughter
AM BD + Emission
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Modes of Decay
• α: Emission of a helium nucleus
• β-: Emission of an electron
• β+: Emission of a positron
• γ: Emission of a photon– Isomeric transition
– Competes with internal conversion
• Electron Capture: Absorption of an electron with emission of photons
• Fission– Formation of two daughter nuclei
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What is the difference between a γ-ray and
an x-ray?
There all just photons!
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α Decay
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β- Decay
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β+ Decay
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β+ Annihilation
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β+ Annihilation
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Electron Capture
Releases characteristic x-raysCompetes with β+ decay
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γ Decay
Can occur in conjunction with all other modes of decay•Isomeric transition
Competes with internal conversion•Emission of a conversion electron
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What is the emission that we care about as Nuclear
Cardiologists?
Photons!
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Radioactive Decay
α
β-
β +EC
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Decay: Half Life
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Transient Equilibrium
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Technetium Generator
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Outline• Tracers - Nuclear Physics
– Atomic structure
– Radioactive decay
– Specific radionuclides
• Camera - Gamma Camera – Collimators
– Energy Selection
• Radiation Safety
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Photons Interact with Matter
• No interaction• Photoelectric absorption• Compton scattering• {Pair production}• {Coherent scattering}
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Photoelectric Absorption
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Compton Scattering
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Attenuation
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Energy Spectrum
137Cs
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Gamma Camera
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Gamma Camera Goals
• Absorb photons• Coming from directly in front of the camera• But not the scattered photons
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Gamma Camera
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Collimator
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Why Use a Collimator
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NaI(Tl) Crystal
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NaI(Tl) Crystal
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The Back End
• Determines position of absorbed photon
• Accepts only those photons that were not scattered toward the camera
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Energy Window: Tc-99m
141keV
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Patient Positioning
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Raw Data
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Outline• Tracers - Nuclear Physics
– Atomic structure
– Radioactive decay
– Specific radionuclides
• Camera - Gamma Camera – Collimators
– Energy Selection
• Radiation Safety
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Radiation Safety
• Time• Distance • Shielding
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Radiation Safety
• Activity: Becquerel (= 2.7*10-11 Curie)• Absorbed dose: Gray (= 100 rad)• Biologically effective dose: Sievert (= 100 rem)
Absorbed dose is a function of activity and time
Biologically effective dose is the absorbed dose multiplied by a quality factor (for photons, =1)
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Example Radiation Exposures
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You Exposure Increases by 1 mREM from…
• Three days of living in Atlanta • Two days of living in Denver • About seven hours in some spots in the Espirito
Santo State of Brazil. • An average year of TV watching • A year of wearing a luminous dial watch • A coast-to-coast airline flight
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Time
• Spend as little time as possible near radiation– Delivered dose is a function of time
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Distance
• The dose of radiation decreases as the square of the distance between you and the source– Increases as the square of the distance as you get closer
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Shielding
• If you must spend a significant amount of time near a radiation source, use as much shielding as possible– Lead
– Plastic
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Lead Shielding
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Plastic Shielding
• Best for β emitters– Prevents bremsstrahlung
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Summary• Tracers - Nuclear Physics
– Atomic structure
– Radioactive decay
– Specific radionuclides
• Camera - Gamma Camera – Collimators
– Energy Selection
• Radiation Safety
