Introduction to Radiation Radiation Units Health Physics Society

Introduction to Radiation: Radiation Units ©Health Physics Society

Introduction to Radiation • Objectives • To provide useful information about • • radiation for interested individuals To introduce basic concepts of radiation and radioactivity To improve understanding of radiation – what it is and how it interacts

Radioactivity Units • International Unit • becquerel (Bq) • U. S. Unit • curie (Ci) • 1 Ci = 37 GBq • 1 m. Ci = 37 MBq • 1 µCi = 37 k. Bq

Radiation Exposure Units • International Unit • coulomb per kilogram (C/kg) • U. S. Unit • roentgen (R) • defined only for measurement in air • applies only to x and gamma rays up to energies of about 3 Me. V • 1 R = 2. 58 x 10 -4 C/kg • 1 m. R = 0. 258 C/kg • 1 µR = 258 C/kg

Radiation Exposure Units • Roentgen • Historically used to measure the amount of energy in a photon beam just prior to entering the skin of a patient • Often still used when discussing the entrance skin exposure for medical x-ray exams

Radiation Absorbed Dose Units • International Unit • gray (Gy) • U. S. Unit • rad • 1 rad = 0. 01 Gy • 1 mrad = 0. 01 m. Gy • 1 µrad = 0. 01 µGy

Radiation Absorbed Dose Units • Radiation absorbed dose is the amount of energy deposited per unit of tissue. • It is usually measured in ergs per gram or joules per kilogram.

Radiation Effective Dose Units • International Unit • sievert (Sv) • U. S. Unit • rem • 1 rem = 0. 01 Sv • 1 mrem = 0. 01 m. Sv • 1 µrem = 0. 01 µSv

Radiation Effective Dose Units • Effective dose is used to represent “how good” the absorbed dose of radiation might be at producing an effect – so it accounts for the effectiveness or quality of the radiation. • Effective dose also includes a factor representing the sensitivity of the tissue to the radiation – so it also accounts for how the tissue might react.