Review of Basic Radiation Concepts PDF

Review of Basic Radiation Concepts Brian Kenneth N. Dela Cruz, RRT Radiation transfer of energy. Types of radiation (2) Non-ionizing and ionizing radiation Ionizing radiation - capable of removing an orbital electron from the atom with which it interacts...

Review of Basic Radiation Concepts Brian Kenneth N. Dela Cruz, RRT Radiation transfer of energy. Types of radiation (2) Non-ionizing and ionizing radiation Ionizing radiation - capable of removing an orbital electron from the atom with which it interacts PRESENTATION TITLE 2 Radiation Creates ion pair electron - negative ion remaining atom - positive ion. Categories (2) Particulate radiation (alpha and beta) Electromagnetic radiation (Ultraviolet, x-ray, gamma) PRESENTATION TITLE 3 Radiation Sources of Ionizing Radiation Natural environmental and Man-made radiation Natural environmental (3 mSv) Consists of: Cosmic (sun and stars) Terrestrial (Deposits of uranium and thorium) Internally deposited radionuclide (potassium 40) Radon (largest source of natural environmental, radioactive gas came from decay of uranium, emits alpha particle) PRESENTATION TITLE 4 Radiation Man-made Radiation (3.2 mSv) Diagnostic X-ray (largest man-made source) Other sources of man-made radiation Nuclear power generation Research applications, Industrial sources Consumer items PRESENTATION TITLE 5 Radiation Quantities and Units Alpha particle Originated from radioactive nuclei of heavy elements contains two protons and two neutrons Equal to a helium nucleus Atomic mass unit (amu) = 4 Carry 2 units of positive electric charge Has 4 to 7 MeV of kinetic energy Travels approximately 5 cm in air, ≤0.1 mm in soft tissue Harmless in superficial skin, harmful if internally deposited (e.g radon irradiating lung tissue) PRESENTATION TITLE 6 Radiation Quantities and Units Beta particle Originated from radioactive nucleus Atomic mass number = 0 Carry one unit of positive or negative charge Negatively charged (Negatron) positively charged (Positron) Also called anti-matter PRESENTATION TITLE 7 Radiation Quantities and Units Beta particle Difference between negative beta particles (negatron) and electron is its origin Can traverse 10 to 100 cm of air 1 to 2 cm of soft tissue PRESENTATION TITLE 8 Radiation Quantities and Units PRESENTATION TITLE 9  Radiation Quantities and Units Exposure used to describe the quantity of ionization produced when x-rays or gamma rays interact in air because it can be conveniently measured directly by collecting the electric charge, whereas that which occurs in a person cannot be. PRESENTATION TITLE 10  Radiation Quantities and Units The roentgen (R) is the unit of radiation exposure; it is defined only for air and applies only to x-rays and gamma rays up to energies of about 3 MeV. Exposure rates are often expressed as roentgens per unit time, e.g., R/s, mR/h, etc. Since the roentgen is determined in air, it is not a radiation dose but with appropriate adjustment it can be converted to dose. PRESENTATION TITLE 11 Radiation Quantities and Units PRESENTATION TITLE 12 Radiation Quantities and Units PRESENTATION TITLE 13  Radiation Quantities and Units Radiation Absorbed Dose is defined as the amount of energy deposited per unit mass. Biologic effects usually are also related to the radiation absorbed dose. The conventional unit for absorbed dose is the rad (radiation absorbed dose) and is equal to the absorption of 100 erg of energy in 1 g of absorbing medium, typically tissue. 1 rad = 100 erg/g of medium PRESENTATION TITLE 14 Radiation Quantities and Units PRESENTATION TITLE 15 Radiation Quantities and Units Kerma “Kinetic energy released in air,” “kinetic energy released in material,” and “kinetic energy released per unit mass” all use the word kerma as an acronym. In simple terms, air kerma is the total kinetic energy released in a unit mass (kilogram) of air and is expressed in metric units of joule per kilogram (J/kg).In a similar way one can define tissue kerma as the total kinetic energy released in a unit mass of tissue. Tissue kerma is also given in units of joules per kilogram. PRESENTATION TITLE 16 Radiation Quantities and Units This unit for kerma is in fact the same radiation unit, the gray (Gy), which was previously defined as the SI unit for the radiation quantity, absorbed dose. With respect to radiographic and fluoroscopic units, however, “air” kerma, not “tissue” kerma, is the primary concept because in these situations we are concerned with exposure and the patient's resulting entrance dose. PRESENTATION TITLE 17  Radiation Quantities and Units Radiation dose equivalent describe the radiation dose equivalent (or rate) received by workers and the public. The definition of dose equivalent is necessary because different radiations produce different amounts of biological damage even though the deposited energy may be the same. PRESENTATION TITLE 18  Radiation Quantities and Units If the biological effects of radiation were directly proportional to the energy deposited by radiation in an organism, the radiation absorbed dose would be a suitable measure of biological injury, but this is not the case. Biological effects depends not only on the total energy deposited, but also on the way in which it is distributed along the path of the radiation. PRESENTATION TITLE 19  Radiation Quantities and Units In the conventional system of units, the unit of dose equivalent is the rem The SI unit of dose equivalent is the Sievert (Sv) PRESENTATION TITLE 20  Radiation units Radioactivity Activity, or intensity of radioactive emission, is the number of atoms that undergo transformation to new atoms per unit time. For many years the standard unit of radioactivity has been the curie (Ci), first defined as the emission rate of 1 g of radium Radiation Quantities and Units PRESENTATION TITLE 22  Radiation Quantities and Units SI unit of radioactivity is becquerel (Bq) as that quantity of any radioactive material that produces one transformation per second: 1 Bq = 1 t/s PRESENTATION TITLE 23 Radiation Quantities and Units PRESENTATION TITLE 24