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Welcome to the field of medical imaging • Objectives: • Matter, energy, the electromagnetic spectrum – ionizing radiation • Relative intensity of ionizing radiation • Discovery of x-radiation • Basic concepts of radiation protection
Matter and Energy • Matter = anything that has mass and occupies space. • Energy = the ability to do work
Matter • A primary characteristic of matter is “mass”. • Mass = the quantity of matter contained in any physical object.
Mass vs Weight • For our purposes mass and weight can be considered the same. • In the strictest sense they are not the same. • Mass = energy equivalence • Weight = the force exerted on a body under the influence of gravity
Mass • Mass is measured in kilograms (kg). • How many grams are in a kilogram? • Kilogram is the scientific unit of mass and is unrelated to gravitational effects.
kilo • Kilo stands for 1000 • Kilogram = 1000 grams
Atom Molecules Elements Compounds Building blocks of matter
Energy • Define Energy? • Energy can exist in several forms • Energy can be measured in varied units of measurement. The International System (SI) = joules (J). In Radiology = electron volt (eV) (ex: e- energy vs. kVp)
Potential energy • Ability to do work by virtue of position. • Ex: roller coaster or stretch spring.
Kinetic energy • Energy of Motion • Work because of motion • Ex: moving car, moving river
Chemical energy • Energy released by chemical reaction • Ex: energy from the food we eat.
Electrical energy • Electrons moving through an electrical potential difference • Ex: household electricity – 110 volts
Thermal energy (heat) • Energy of motion at the atomic and molecular level. The kinetic energy of molecules vibrating • Ex: Heat from an X-ray tube
Nuclear energy • Energy contained in the nucleus of an atom • Ex: nuclear electric power plants
Electromagnetic energy • Not as familiar to us as other forms of energy … but very important to radiographers • Results from electric and magnetic disturbances in space • This energy is produced by the acceleration of a charge
Radio waves, microwaves, ultraviolet, infrared, visible light… what else?
Electromagnetic energy • Is often referred to Electromagnetic radiation when it is traveling through space. • Radiation is the transfer of energy (usually through space) • When a guitar string vibrates it is said to radiate sound.
Exposed or Irradiated • Matter that intercepts radiation and absorbs part or all of it is exposed or irradiated
X-rays • You will learn to expose or irradiate patients for medical treatments or diagnosis
X-Rays are Ionizing radiation X-rays are a special type of radiation. X-rays are capable of removing an orbital electron from the atom with which it interacts.
Ionization • Ionization occurs when an x-ray passes close to an orbital electron of an atom and transfers sufficient energy to the electron to remove it from the atom.
Ion pair • The orbital electron and the atom from which it was separated are called an ion pair. • The electron is a negative ion and the atom is a positive ion.
Examples of Ionizing Radiation • X-rays, gamma rays, and ultraviolet light
Ionization • Some particles with high kinetic energy can cause ionization • Ex: Alpha & Beta particles
Sources of Ionizing Radiation • Natural Environmental Radiation • Man – made Radiation
Natural radiation • Natural radiation accounts for approximately 300 millirem (mrem) • 3 sources of environmental radiation: cosmic rays, terrestrial radiation and internally deposited radionuclides. The largest source of natural radiation is radon.
MEDICAL IMAGING • Diagnostic Imaging • Medical xrays • Dental xrays • GREATEST SOURCE OF MAN-MADE RADIATION
Diagnostic x-rays • 1990 the National Council on Radiation Protection and Measurements (NCRP) • 39 mrem/yr OR 0.39 mSv/yr • More recent NCRP estimates indicate nearly 320 mrem/yr OR 3.2 mSv/yr. Due to increasing use of multslice spiral CT and high-level fluoroscopy
Is this a safe profession ? • Natural radiation = 300 mrem/yr • Average medical exposure = 50 mrem/yr 39 – 320 mrem/yr • Technologists?
Crookes Tubes • Were the beginning of the modern fluorescent lamps and x-ray tubes.
“Willie Rontgen” • Honored in 1901 with the first Nobel prize in physics for his efforts.
X-Ray Properties: Roentgen’s discovery • Are highly penetrating, invisible rays which are a form of electromagnetic radiation. • Are electrically neutral and therefore not affected by either electric or magnetic fields
X-Ray Properties • Can be produced over a wide variety of energies and wavelengths (polyenergetic & heterogeneous). • Release very small amounts of heat upon passing through matter.
X-Ray Properties • Travel in straight lines. • Travel at the speed of light, 3 X 108 meters per second in a vacuum or 299,792,458 m/s. or 29,979,245,800 cm/s • Can ionize matter.
X-Ray Properties • Cause fluorescence of certain crystals. • Cannot be focused by a lens. • Affects photographic film.