radiation protection

Matter

• Matter makes up everything in the universe, has mass, and takes up space
• Matter is composed of atoms and molecules
• States of matter include solids, liquids, gases, and plasma

Ionization

• An atom becomes positive or negative, through gaining or losing an electron
• An ionized atom is called an ion
• Ions can activate radiation detectors and produce biological effects in the body

Radiation

• Radiation is a form of energy that can be transferred through space

Low Energy Radiation

• Radio waves have radio bands
• Radiofrequency waves are used in MRI
• Microwaves are used in cooking
• Radar has radar detectors for speed monitoring

Medium Energy Radiation

• Infrared ray is emitted by skin and used in toaster ovens
• Visible light includes red, orange, yellow, green, blue & violet
• UV waves destroy bacteria but also cause skin cancer

High Energy Radiation

• X-rays are photons from the electron shell, and used to image bone & body parts
• Gamma rays are photons that come from the nucleus and are used to destroy cancer cells with radioactive material

Electromagnetic Energy

• Energy is emitted and transferred through space

Electromagnetic Radiation

• X-rays are electromagnetic radiation
• All electromagnetic radiation travels at the same velocity in a vacuum
• Energy is determined by wavelength
• The greater the energy, the shorter the wavelength
• Low energy electromagnetic waves include radio, infrared, and visible light, and have a long wavelength
• High energy electromagnetic waves are X-rays & Gamma rays
• These high energy waves can cause ionization, and have a short wavelength
• Ionizing rays can break apart atoms and cause biologic/somatic/genetic damage
• They are produced by machines (man made)

Ionizing Radiation

• High energy radiation has sufficient energy to eject electrons from atoms
• A loss of electrons results in ionization of atoms
• Free electrons become positively charged
• Ionization radiation can have biologic effects on the body, thus radiation benefits must outweigh the risks of any x-ray diagnostic study

Non- Ionizing Radiation

• Low energy radiation includes long wavelength and low frequency
• They do not cause ionization

Sources of Ionizing Radiation

• There are natural environmental sources
• There are man-made sources
• Natural sources include internal sources from the human body
• Terrestrial sources from earth like Radon
• Extraterrestrial sources from space
• Medical procedures account for nearly all (96%) human exposure to man-made radiation

Man-Made Radiation

• Medical radiation includes: CT imaging, Nuclear medicine, Fluoroscopy, Interventional procedures, X-rays (Mobile Imaging, General Radiography and Dental Imaging), and Radiation Therapy

Medical Imaging

• Medical imaging includes Radiography, Fluoroscopy, and Computed tomography (CT)
• Providing an x-ray beam that is satisfactory for imaging requires supplying the x-ray tube with a high voltage and an electric current
• Radiology emerged as a medical specialty with invention of the Snook transformer and the Coolidge x-ray tube

X-Ray Discovery

• Wilhelm Roentgen accidentally discovered x-rays, in his laboratory in Wursburg, Germany
• He made this discovery in 1895, while working with cathode rays, and a Crookes tube

Brief History of X-Rays

• Radiography was born after seeing his own hand bones on a fluorescent screen
• There was a 4-minute exposure of a photographic film to the light of the screen with his wife's hand placed in front of it

X-Rays

• X-rays are electromagnetic radiation with wave and particular properties
• They have a dualistic nature and behave both as waves and particles/photons
• Wave properties include: Wavelength, frequency and amplitude
• Particular properties include: Can collide with other electrons or particles, have energy and momentum, can be destroyed, absorbed and emitted, have zero mass at rest, and move with a constant velocity

Radiation Dangers

• X-rays lose energy as they interact with atoms in human tissue
• X-ray energy is deposited in the tissue
• High energy radiation (X-rays & Gamma rays) can remove an orbital electron from an atom
• Atoms & molecules of tissue may become ionized after exposure
• Exposure can result in breakage of the molecule
• Exposure can result in relocation of the atom within the molecule
• The most important molecule affected is DNA
• DNA damage equals chromosome aberrations

X-Ray Beam

• X-ray beam leaving the x-ray tube toward the patient is the primary beam
• It can undergo three possible actions as it travels through tissue: -Total absorption -Pass through with no loss of energy -Undergo scattering and secondary interactions with some loss of energy

X-ray Interaction with Matter

• Low-energy x-rays interact with atoms
• Moderate energy x-rays interact with electrons
• High-energy x-rays interact with the nuclei of atoms

Five Possible Interactions of X-Rays

• Coherent scattering is an interaction with an atom
• Pair production is an interaction with the nucleus
• Photodisintegration is an interaction with the nucleus
• Compton scattering is an interaction with outer-shell electrons
• Photoelectric effect is an interaction with an inner-shell electron
• Only 2 interactions are relevant in diagnostic imaging: Compton Scattering and Photoelectric effects

Fundamental Units

• Exposure unit is gray (Gya)
• Absorbed dose unit is gray (Gy₁)
• Effective dose unit is Sievert (Sv)
• Activity unit is Becquerel (Bq)

Dose Assessment

• Calculating radiation dose involves considering the nature and strength of the ionizing radiation, biological sensitivity of the area/tissue exposed, and exposure factors
• Exposure factors include time, distance, and shielding from the source

Exposure Standards

• Standards are regulated by the FDA and its Center for Devices and Radiological Health (CDRH)
• Effective dose limit recommendations have been set to minimize the biologic risk to exposed persons
• Dose should be kept as low as reasonably achievable (ALARA)
• The annual whole-body effective dose limit for the occupational worker is 50 mSv (5 rem)

Dose-Risks Relationship

• Physicians use a “risk vs. benefit" rationale when ordering ionizing radiation studies.
• Benefits of exam must outweigh the potential risks from radiation exposure.
• Radiation doses should always be kept as low as possible

Radiation Biologic Effects

• Cells have two major parts: Nucleus and Cytoplasm
• Genetic material of cell is contained in the nucleus

Cell Radiation

• Two theories of cellular irradiation damage exist
• Cells have different degrees of radiosensitivity
• Certain organs and tissue of the body are more radiosensitive than others
• Cellular radiosensitivity is principally a result of the rate and duration of cellular mitosis
• Cells undergoing mitosis are more radiosensitive

Tissue Sensitivity

• Most radiosensitive cells are: -Stem cells -Younger tissue and organs (Infants & Children) -Developing embryo -Fetus (8-15 weeks gestation) -Reproductive cells -Cells in Thyroid -Bone marrow cells -Cells in mucosal lining of intestinal tract
• Least radiosensitive cells/organs are: Mature cells, Muscle, Heart, and Nerve cells
• These undergo less cell renewal

Acute Radiation Syndrome

• Describes the sequence of events following high-level radiation exposure leading to death with days or weeks
• Symptoms include: Anorexia, Nausea, Vomiting, and Diarrhea

Radiation Syndromes

• These doses are far greater than those received by the occupational worker or patient
• Initial symptoms: Nausea, vomiting, and diarrhea
• Latent period: No symptoms
• Manifest Illness: Vomiting, mild diarrhea, malaise, lethargy and fever, Disorientation, difficulty breathing, convulsive seizures, loss of equilibrium, and coma Death can be due to infections electrolyte imbalance, and dehydration

Acute Radiation Syndromes

• There are three syndromes:

• Hematologic (1-6 Gyt or 100 - 600 rad): -Damage to blood cells -Recovery possible -Death due to infections electrolyte imbalance, and dehydration

• Gastrointestinal (GI) (6 - 50 Gy₁ or 600 – 5000 rad): -Death in 4-10 days -Recovery can be possible

• Central Nervous System (CNS) (Over 50 Gy₁ or 5000 rad) -Death within hours or days

Effects of Radiation on the Body

• Somatic effects are Effects to Effects in an individual
• Genetic effects are Effects in future generations as a result of damage to the reproductive cells

Patient Radiation Protection

• The cardinal rules of protection are: -Time (Minimize the amount of time around radiation), -Distance (Maximize your distance from radiation whenever it is practical), and -Shielding (Use lead aprons and gloves when in the x-ray room during an exposure)
• There should be X-ray beam restriction using Collimation
• Always utilize Optimum exposure technique selection

Monitoring of Personnel

• Personnel require Dosimeters and Dosimetry Reports that list any radiation dose received
• There for is usually a designated Radiation Safety Officer (RSO)

Radiation Monitoring

• Any occupational worker, regularly exposed to ionizing radiation, must be monitored to determine exposure
• Any worker, likely to receive more, than one tenth of the recommended dose-equivalent limit, should be monitored

Occupational Personnel Monitoring

• Dosimeters measure the quantity of radiation received based on the conditions in which the radiographer was placed
• Exposure data are collected for a specified period of time
• A common dosimeter is the Optically Stimulated Luminescence (OSL) Dosimeter

Dosimeter Placement

• Dosimeters should be Worn at the collar level
• Worn outside of lead apron
• Device should face forward
• Pregnant radiographers may have a second device worn at waist level and under the lead apron

Protective Radiation Garments

• Utilize all protective radiation garments

Basic Radiation Protection

• Practice ALARA (As Low As Reasonably Achievable): Minimize radiation exposures
• Always Utilize Protective Apparel
• Always Utilize Gonadal Shielding
• Always utilize Protective Barriers (lead walls, and lead glass windows)
• Always utilize Filtration (usually aluminum or copper), which is Inserted in tube housing to absorb low energy x-rays
• Always utilize Collimation to restrict the useful x-ray beam only to the part being imaged

Primary Versus Secondary Barrier

• The Beam should be directed at the patient only
• Primary Barrier protects from the primary beam, and usually points in direct of the x-ray beam during patient imaging
• Location Examples: Walls, Floor and Door
• Secondary Barrier protects from scatter radiation from the tube, beam, and patient
• Location Examples: Ceiling and Control booth
• Never point the x-ray beam towards a secondary barrier

Rule for Holding Patients

• The technologist and student never hold the patient during an exposure

Important Radiation Protection Facts

• Clarence Dally was the first person to die from radiation overdose in the United States
• He died in 1904 after suffering from severe radiation burns and the amputation of both arms
• He was an assistant for Thomas Edison in the development of the fluoroscope and fluorescent screen
• Edison stopped all x-ray work and suggested controls but pleas for radiation control were ignored Becquerel is cited as the first individual to notice that ionizing radiation had certain biologic effects
• He noted skin reaction – erythema – 2 weeks after carrying a tube of radium in his pocket