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MIRD Pamphlet No. 21: A Generalized Schema for Radiopharmaceutical Dosimetry—Standardization of Nomenclature PowerPoint Presentation
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MIRD Pamphlet No. 21: A Generalized Schema for Radiopharmaceutical Dosimetry—Standardization of Nomenclature. 5/15/2009. MIRD. Medical Internal Radiation Dose Committee of the Society of Nuclear Medicine Original schema first issued in 1968

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MIRD Pamphlet No. 21: A GeneralizedSchema for RadiopharmaceuticalDosimetry—Standardization of Nomenclature

5/15/2009

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MIRD
  • Medical Internal Radiation Dose
    • Committee of the Society of Nuclear Medicine
    • Original schema first issued in 1968
  • Provides a framework for the assessment of absorbed dose to organs, tissue subregions, etc. from internally deposited radionuclides
  • Update to:
    • Standardize nomenclature
    • Adopts effective and equivalent dose
    • Highlights need to address deterministic effects
mean absorbed dose rate
Mean Absorbed Dose Rate
  • rT, rS: target tissue and source tissue
  • D(rT,t): dose rate at time t in target tissue

rS

S

S

rT

rS

mean absorbed dose
Mean Absorbed Dose
  • Equation describes the dose to target tissue rT for integration time TD after administration of radionuclide
  • Time-dependent activity can be measured (e.g. w/ imaging, sampling) or modeled
s r t r s t
S(rT←rS,t)
  • Relates dose in target organ to activity in source organ
  • Function of emission spectrum, relative position of organs, shape, and size of organs
  • Tabulated for “standard” geometries and radionuclides
s r t r s t1
S(rT←rS,t)
  • Ei = energy of ith nuclear transition
  • Yi = number of ith transition / nuclear transformation
  • Δi=EiYi
  • Фi = fraction of emitted energy absorbed in target
  • M(rT,t) is the mass of the target tissue
equivalent dose
Equivalent Dose
  • “The equivalent dose is a radiation protection quantity defined by the ICRP (7,8) and used to relate absorbed dose to the probability of stochastic health effects in a population exposed to radionuclides or radiation fields…”
  • Stochastic effects include cancer and heritable disease
  • Is not applicable to deterministic effects
  • Unit = Sievert (Sv)
equivalent dose1
Equivalent Dose
  • H(rT,TD): equivalent dose
  • wR: Radiation weighting factor for radiation type R (1 for photons & electron, 20 for -particles)
effective dose
Effective Dose
  • “The effective dose E is a radiation protection quantity defined … for establishing annual limits of exposure to workers and members of the general public.”
  • Accounts for internal and external radiation sources
  • Unit = Sievert (Sv)
quantities related to deterministic effects
Quantities Related to Deterministic Effects
  • RBE-weighted dose
  • BED
  • EUD
  • Isoeffective Dose
rbe weighted dose
RBE-weighted dose
  • RBE: Relative Biological Effectiveness
  • RBE is analogous to wR (from equivalent dose equation)
  • RBE depends on tissue and biologic endpoint
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BED
  • BED: Biologically Effective Dose
  • Usually used to compare different fractionation schemes
  • Accounts for dose rate variation in radionuclide therapy
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EUD
  • EUD: Equivalent Uniform Dose
  • Dose delivered to an organ is generally not uniform
  • EUD is the dose value that when uniformly delivered to an organ would yield the same response as the actual dose
  • Unit: Gray (Gy)
isoeffective dose
Isoeffective Dose
  • Recently proposed to allow comparison of high LET and low LET radiation.
summary
Summary
  • MIRD schema is used to calculate dose from internal radionuclides
  • Stochastic effects
    • Equivalent dose: accounts for radiation type
    • Effective dose: accounts for radiation type and organs irradiated