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Radiation Protection and Medical Internal Dosimetry 輻輻輻輻輻輻輻 輻輻輻 輻輻 輻輻輻輻輻輻輻輻輻輻輻輻輻輻 輻輻輻輻輻 輻 輻 輻 輻輻

Архитектура брендов: описание типов Описание архитектур

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Page 1: Архитектура брендов: описание типов Описание архитектур

Radiation Protection and Medical Internal Dosimetry 輻射防護及醫用體內輻射劑量

高雄醫學大學附設中和紀念醫院 核子醫學科 陳 毓 雯 主任

Page 2: Архитектура брендов: описание типов Описание архитектур

Pattern of Radiation Effect

ExposureContamination

Page 3: Архитектура брендов: описание типов Описание архитектур

Units of Radiation DoseActivity (A) Bq Radiation exposure C/kgAir keramaAbsorbed dose (D) grayEquivalent dose (H)

sievert LET (linear energy transfer)

Effective dose (E)

Page 4: Архитектура брендов: описание типов Описание архитектур

Conversions of Units

Page 5: Архитектура брендов: описание типов Описание архитектур

Threshold Doses for Determininstic Effects in The More Radiosensitive Tissues and Organs

Page 6: Архитектура брендов: описание типов Описание архитектур

Biological Effects of Exposure

Nonstochastic effectsStochastic effects

Page 7: Архитектура брендов: описание типов Описание архитектур

Probability of Risk of Fatal Cancer between Age and Sex

Page 8: Архитектура брендов: описание типов Описание архитектур

Dose in Medical Imaging

Page 9: Архитектура брендов: описание типов Описание архитектур

Annual Effective Dose Distribution in The World

Page 10: Архитектура брендов: описание типов Описание архитектур

Internal Dosimetry The method of calculating absorbed

dose delivered internally has been developed over many years by the Medical Internal Radiation Dose (MIRD) committee of the American Society of Nuclear Medicine.

The aim of committee was to develop a dosimetry system (MIRD schema) for diagnostic nuclear medicine. However, the methods have also been applied in radionuclide therapy and in internal contamination.

Page 11: Архитектура брендов: описание типов Описание архитектур

MIRD SchemaSource Organs vs Target

Organs Dt s = A s St s

Cumulated activity, As the total number of radioactive disintegrations which occur in the sourve organ, and depends on: the activity administered; the uptake of , retention by, and excretion from the organ; and thte physical decay of the radionuclide.

S-factors have been tabulated for a variety of radionuclides and for different source/target configurations in both standard man and children.

Page 12: Архитектура брендов: описание типов Описание архитектур

Cumulated Activity

Page 13: Архитектура брендов: описание типов Описание архитектур

Flow Chart of MIRD Methology

Page 14: Архитектура брендов: описание типов Описание архитектур

S- Factors

St s = 1/ mi Δi i

Δi equilibrium absorbed dose

constant

i absorbed fraction

specific absorbed fraction

(Monte Carlo calculations)

Page 15: Архитектура брендов: описание типов Описание архитектур

Example Calculated the absorbed dose to the liver of an

adult patient who receives 3mCi (111MBq) Tc99m-sulfur colloid for a liver scan, assuming 85% liver uptake with no excretion.

Answer Weight of liver = 1700 g (for a standard man) A0 in the liver = 3000 x 0.85 = 2550 u Ci (86.7 MBq) T e = 6 hr

Δi i = 0.0806

D = 1.44 x (2550/1700) x 6 x 0.0806 = 1.04 rad

Page 16: Архитектура брендов: описание типов Описание архитектур

The limitations of the MIRD Methods

Tabulated doses do not apply to all patients In the MIRD schema it is assumed that the shape, size and

position of the organs are s prepresented by the standard, 70kg, hermaphrodite human phantom. Disease organs can result in both increased or decreased uptake of activiity and changes in the residence time compared with standard values so these factors sholud also be considered when assessing the dose to patients.

The MIRD schema claculates each dose to the target organs as an average, without permitting the determination of a maximumor minimum dose.