RT121 Ch1-4 Notes PDF - Radiation Safety

Chapter 1 Identify the consequences of ionization in human cells. -​ Ionizing radiation has strong enough radiation to remove or add an electron, which makes it into an Ion -​ Releases electrons from atoms & molecules, generating ions that break covalent bonds. -​ Affects...

Chapter 1 Identify the consequences of ionization in human cells. -​ Ionizing radiation has strong enough radiation to remove or add an electron, which makes it into an Ion -​ Releases electrons from atoms & molecules, generating ions that break covalent bonds. -​ Affects DNA by inducing DNA breaks -​ Creates unstable atoms -​ Creates highly reactive free molecules (free radicals) capable of producing substances poisonous to the cell -​ Causes the creation of new biologic molecules detrimental to the living cell -​ Injury to the cell that may manifest itself as abnormal function or loss of function -​ Most atoms will return to the original combination with no damage List the properties, or characteristics of x-rays. -​ INVISIBLE -​ HAVE A VARYING DEGREE OF PENETRATION IN NORMAL SKIN -​ ARE NOT DEFLECTED FROM THEIR PATHS BY EITHER ELECTRIC OR MAGNETIC FIELDS -​ CANNOT BE FOCUSED WITH A LENS -​ TRAVEL IN STRAIGHT LINES & AT THE SPEED OF LIGHT UNTIL THEY INTERACT WITH ATOMS -​ WHEN PASSING THROUGH MATTER, X-RAYS PRODUCE CHARGED PARTICLES BY INTERACTING WITH ATOMS -​ FLUORESCENCE IN CERTAIN CRYSTALS -​ WILL DARKEN AN EXPOSURE, WHERE THE DEGREE OF DARKENING IS ASSOCIATED WITH THE INTENSITY (AMOUNT OF) THE X-RAYS -​ HETEROGENOUS State the goals & discuss the concept of radiation protection. -​ To protect persons from both short and long term effects of radiation -​ Can occur in specific organs and organ systems -​ Can also affect whole body & future generations (cancer,genetic changes) -​ ALARA 1  List the three main types of radiation quantities & identify the unit(s) of measure. -​ Exposure (C/kg) -​ The amount of ionization produced in air when ionizing radiation is present -​ Ionization chambers measure this quantity directly & used to determine the amount of radiation produced by x-ray equipment -​ Measured in COULOMB PER KILOGRAM (MetricSI) or MILLIROENTGEN (subunit of roentgen) -​ Absorbed dose (mGy) -​ The amount of energy that is deposited in a material per unit mass of the material -​ More energy deposited = More biomolecule disruption -​ Measured in MILLIGRAY -​ Effective dose (mSv) -​ Best overall measure of biologic effects of ionizing radiation -​ Attempt to provide a quantity that is a measure of general harm in humans -​ Takes into account amount of absorbed dose, type of radiation, & organ/organ system that was irradiated -​ Measured in MILLISIEVERT Explain the justification & responsibility for imaging procedures. -​ Benefit vs. Risk -​ The realized benefits of exposure to radiant energy, regarding medical information obtained, far outweigh any slight chance of possible biologic damage or genetic effects Explain how diagnostic efficacy of an imaging procedure can be maximized. -​ Minimal radiation exposure for production of optimal images -​ Diagnostic efficacy is the degree to which the diagnostic study reveals the presence or absence of a disease List the three basic principles of radiation protection. -​ Less time, More Distance, More Shielding List employer requirements for implementing & maintaining an effective radiation safety program. -​ Radiation Safety Officer (RSO) is directly responsible for the execution, enforcement and maintenance of ALARA program in hospital setting -​ ALARA is also known as Optimization for Radiation Protection (ORP) -​ EMPLOYER’S RESPONSIBILITIES -​ Implement & maintain an effective radiation safety program to execute ALARA by PROVIDING -​ NECESSARY RESOURCES 2  -​ APPROPRIATE ENVIRONMENT -​ Make a written policy of ALARA program and make it available to all employees -​ Perform periodic exposure audits to determine how to lower radiation exposure in workplace -​ Radiation Worker’s responsibilities -​ Be aware of rules & perform duties consistent with ALARA Compare radiation sensitivity of children with that of adults. -​ Children are more radiosensitive, risk 3x greater -​ Children are more sensitive to radiation exposure because of the presence of many still reproducing cells -​ Early life radiation exposure leads to increase in cancer as they age into 50s & 60s -​ Embryos exposed to radiation from atomic bombs in Hiroshima were associated with significant increase in fatal adulthood cancer Explain how techs should answer patient questions about radiation risk & exposure. -​ Using the BERT method (Background Equivalent Radiation Time) -​ BERT method allows for a means of comparison and emphasizes that radiation is an innate part of the environment -​ Easy for pt to comprehend Explain the difference between Image Gently & Image Wisely campaigns: -​ Alliance for Radiation Safety in Pediatric Imaging -​ A partnership of medical societies whose overall common purpose is to reduce the radiation dose for pediatric patients -​ Image Gently -​ CT dose should be lowered to child size techniques (lower kV,mAs) -​ Pediatric dose should be reduced as much as 50% with no reduction in image quality -​ Image Gently Campaign PLEDGE states to -​ Make its message a priority in staff communications each year -​ Review protocol recommendations, implement adjustments where necessary to practice processes -​ Communicate openly with parents 3  -​ Image Wisely -​ Joint task force formed to address concerns about the increase in public exposure to ionizing radiation -​ Objectives of lowering amt of radiation used in medically necessary studies & eliminating unnecessary procedures Discuss the Pause & Pulse: Image Gently in Fluoroscopy Campaign. -​ Provides a full understanding of the safe operation of fluoro devices on PED. patients -​ To image kids with care, PAUSE and adjust the technique -​ For child fluoro procedures use PULSE radiation & the lowest pulse rate possible Discuss the reasons for monitoring & reporting radiation dose. -​ Required to log maximum skin dose as part of the pt record -​ Protocols for alert levels - When pt. Dose is predicted to or has exceeded preset dose levels -​ In some cases, a medical physicist may be called upon to estimate pt. Doses such as effective dose, peak skin dose, or fetal dose (prolonged fluoroscopy) -​ Joint Commission -​ Requires monitoring of patient dose in CT and IR Other things to note -​ 1900s Medical use of radiation for dx -​ 1895 Radiation implemented into the healing arts How can RT’s safely control the use of radiant energy? -​ By employing effective methods to limit or eliminate radiation-induced hazards -​ By using the knowledge of radiation-induced hazards that have been gained over the years -​ Using effective communication Chapter 2 Provide examples of different types of radiation. -​ Natural -​ Manmade -​ Includes Medical Draw a diagram to illustrate the electromagnetic spectrum and explain how the spectrum can be divided for the purpose of studying radiation protection. -​ Electric & magnetic fields fluctuate rapidly as they travel through space -​ EM waves = Characteristized by Wavelength 4  -​ ALL Electromag Radiation have 1 common characteristic = Velocity -​ Frequency - units of hertz (Hz) cycles/sec -​ Wavelength - meters -​ Energy - electron volts (eV) -​ A unit of energy equal to the quantity of kinetic energy an electron acquires as it moves through a potential difference of 1 V -​ IONIZING RADIATION VS NON-IONIZING RADIATION -​ IONIZING -​ Xrays -​ Gamma Rays -​ UV Radiation >10 eV -​ NON-IONIZING -​ Radio Waves -​ Microwaves -​ Visible Light -​ These DO NOT have sufficient kinetic energy to eject electrons from the atom List the particulate radiations (another ionizing radiation) -​ Radioactive Decay - a naturally occurring process when unstable nuclei relieve the instability by various types of spontaneous nuclear emissions -​ Radioactivity - emission of ionizing radiation from nuclear decay -​ Particulate Radiation = Product of radioactive decay -​ Subatomic particles are ejected from the nucleus of atoms at high speeds a.​ Alpha particles = two protons & two neutrons; occurs in heavy elements like Uranium & Plutonium b.​ Beta particles = (beta decay) identical to high speed electrons besides origin c.​ Neutrons = uncharged particles that collide with nuclei and ko charged particles such as protons 5  d.​ Protons = charged particles -​ Possess enough kinetic energy to be capable of causing ionization by direct atomic collision, however no ionization occurs when at rest 1 Alpha Decay(a-decay) -​ A type of radioactive decay where an atomic nucleus emits an alpha particle (two protons, two neutrons) -​ Typically occurs in heavier elements such as Uranium & Plutonium -​ Nucleus changes into a new, smaller nucleus, the Daughter Nucleus -​ Alpha decay is a way for unstable atoms to become more stable and the result of the strong nuclear force not being able to hold the nucleus together -​ Hazardous when emitted in the body, causes significant localized damage due to their short range therefore dangerous internally -​ Alpha particle carries away most of the energy lost by the nucleus during decay -​ LEAST PENETRATING -​ Alpha particles possess low penetrating power, could be stopped by a piece of paper, therefore mostly harmless externally 1 6 Beta Decay -​ Occurs when a nucleus relieves instability by one of the neutrons transforming itself into a combination of a proton and an energetic electron (Beta Particle) -​ Beta Electrons or Positrons (positively charged electron) are ejected from the nucleus during decay of a neutron into a proton -​ NEUTRINOS are also emitted, tiny subatomic particles, 6 mil miles of lead would only stop half of them, carries away excess energy during beta decay and has almost no mass, nearly impossible to detect -​ NEUTRINOS ARE THE MOST PENETRATING -​ Beta particles are 8000x lighter than Alpha particles, do not interact as strongly with their surroundings as alpha particles, penetrating more with less ionization along their path -​ Beta radiation has moderate penetration ability, more than Alpha -​ Used in Nuc Med 7 Protons -​ Due to positive charge, strongly interact with negatively charged electrons in atoms -​ Less penetrating than high energy electrons -​ Used in proton therapy Neutrons -​ Although they have no charge when collide with atomic nuclei, they can knock out charged particles (protons) which can go on to ionize atoms in the surrounding material -​ INDIRECT ionizing radiation -​ Penetrate more than Beta & Alpha -​ Used in astrophysics and nuclear physics Identify the unit of measure in which radiation absorbed dose, Equivalent dose and effective dose is most commonly specified -​ Absorbed Dose (D , radiation quantity) = the amount of energy per unit mass that has been absorbed in a material due to its interaction with ionizing radiation -​ Measured in mGy or Gy -​ Equivalent Dose (EqD) = provides an overall dose value that includes the different degree of tissue interaction and takes into account the type of ionizing radiation absorbed, for ex proton, xray, etc -​ Measured in mSv -​ EqD is used to calculate EfD -​ Effective Dose (EfD) = the best estimate of overall harm that might be produced by a given absorbed dose of radiation in human tissue/organs. Takes into account body part irradiated & type of radiation. -​ Measured in mSv 8 Explain how ionizing radiation can cause biologic damage in body tissue. -​ Ionizing radiation primarily causes biologic damage by ejecting electrons from the atoms -​ Atomic level destructive radiation interaction results in molecular change and can cause cellular damage -​ This leads to ABNORMAL/COMPLETE LOSS OF CELL FUNCTION -​ Organic includes tissue or changes in blood count -​ If excessive multicellular damage occurs, there is chance of exhibiting genetic or somatic (body) changes -​ Mutations (genetic) -​ Cataracts (somatic) -​ Leukemia (somatic) -​ 250mSv will cause a decrease in lymphocytes List and describe three sources of natural background ionizing radiation and six sources of human-made ionizing radiation. Natural Background Radiation 3.1mSv 1.​ Terrestrial radiation 0.21mSv – radioactive material in the crust of the earth. a.​ Uranium, Radium & Thorium b.​ 2.3mSv of Natural Background Radiation comes from Gaseous RADON & THORON that emit alpha particle radiation i.​ Thoron is a radioactive decay product of an isotope of Radon 9  2.​ Cosmic radiation 0.3mSv – extraterrestrial origin; radiation from the sun (solar) and beyond the solar system (galactic). a.​ Greatest intensity at higher altitudes, bc there is less attenuation due to low atmospheric density b.​ Moderate intensity at sea level c.​ Consists of primarily high energy protons 3.​ Internal radiation 0.3 mSv (per textbook) 0.5 per slides- naturally existing radioactive atoms (radionuclides) which make up a small percentage of the body’s tissue. a.​ Potassium, Carbon, Hydrogen, Strontium are radioactive nuclides in the body b.​ These radioactive nuclides create alpha particle, beta particle, and gamma ray radiation Human-Made Radiation (0.1mSv) 1.​ Consumer products containing radioactive materials a.​ Smoke detectors, Airport surveillance systems, Electron microscopes, Industrial static eliminators 2.​ Nuclear fuel for the generation of power 3.​ Atmospheric fallout from nuclear weapons testing 4.​ Nuclear power plant accidents including ones as a consequence of natural disasters 5.​ Air travel a.​ Commercial airline flights bring humans to higher elevations and closer in contact with high energy extraterrestrial radiation (cosmic rays) b.​ A flight on a typical commercial airliner results in an EqD rate of 0.005 – 0.01 mSv/hr c.​ Sunspots (dark spots on the sun) = increased electromagnetic field activity & may eject particulate radiation into space. d.​ 10-hour flight during reg. sunspot activity = EqD to one CXR exam. 6.​ Medical Radiation 2.33 a.​ X-ray 0.2 mSv b.​ Nuc Med 0.4 mSv c.​ CT 1.5 mSv d.​ IR 0.2 mSv Subtotal of ALL HUMAN MADE (human+medical) is 2.4mSv 10 Discuss the modalities used in medical imaging that have caused an increase in radiation dose for patients from 1980 until the present -​ CT 63% -​ Nuc Med 15% -​ Radiography and Fluoro -​ IR The amount of radiation received by a pt. from a diagnostic x-ray procedure may be indicated by: Entrance skin exposure (ESE) – including skin & glandular dose Bone marrow dose Gonadal dose In pregnant women – fetal dose Nuclear Power Plant Accidents Three Mile Island 1979 ○​ Overheating of the highly radioactive reactor core due to loss of coolant. Resulted in a partial meltdown & radiation leak. ○​ Predicted that no more than one additional case of fatal cancer may occur as a result of radiation exposure from this accident. Chernobyl 1998 ○​ Steam explosion 11  ○​ Approx 5k cases of Thyroid cancer were attributed to the accident ○​ The most highly exposed Chernobyl liquidators who works after the accident demonstrated a significant increase in Leukemia ○​ Breast Ca also increased ○​ Released over 1 million times more radioactive material than Three Mile Island Fukushima Daiichi 2011 ○​ Nuclear power plant severely damaged as a consequence of a 9.0-magnitude earthquake that triggered a tsunami ○​ World’s 2nd most devastating Nuclear Power plant explosion Chapter #3 Explain the meaning and significance of peak kilovoltage (kVp) & milliampere-seconds (mAs) as technical exposure factors. kVp; peak kilovoltage -​ The highest energy level of photons in the x-ray beam -​ Quality/Penetrating Power -​ Potential Difference = Energy of electrons inside the x-ray tube aka highest Electrical Voltage from cathode to anode -​ 100kVp = 100,000 eV -​ Mean Photon Energy in the beam is ⅓ the energy of the MOST energetic photon -​ 100 kVp beam contains photons having energies of 100 keV or less, with an average or effective energy of approximately 33 keV. -​ keV refers to the energy of specific x-rays mAs -​ Milliamperage (electron tube current) x time in seconds that the x-ray tube is activated. -​ Quantity/Amount of radiation during exposure -​ Main determinant of how much radiation is directed toward a patient during a selected exposure Process of absorption and why absorbed dose in atoms of biologic matter should be kept at minimum Absorption in Biologic Tissue (3 ways) 1.​ Interact with the atoms of the biologic material in the patient and be absorbed PHOTOELECTRIC ABSORPTION 2.​ Interact with the atoms in the biologic material and be scattered, causing some INDIRECT TRANSMISSION 3.​ Pass through without any interaction at all DIRECT TRANSMISSION 12 Absorption = If an interaction occurs, electromagnetic energy is transferred from the x-rays to the atoms of the patient’s biologic tissue -​ The amount of energy absorbed per unit mass = absorbed dose (D) -​ More electromagnetic energy received by the atoms of the patient’s body = the greater the possibility of biologic damage -​ We need absorption differences of various body structures to produce diagnostically useful images. Scatter -​ Photons interact with atoms of the patient but only surrender part of their energy -​ The photon continues to exist but will emerge from the interaction at a different angle Differentiate among the following: primary radiation, exit, or image-formation radiation, scattered Radiation, and attenuated radiation. Primary Radiation = the filtered (inherent) x-ray photon beam; the most energetic photons in this beam can have no more energy than the electrons that bombarded the target -​ Primary Photons = Photons produced by x-ray source before they enter human tissue Exit/Image formation Radiation =Photons that emerge from tissue and strike IR (this can include small angle scatter that hits IR which still degrades image quality) Attenuated Radiation = A reduction in the intensity of photons in the primary beam which can occur through either absorption or scatter and DO NOT strike the image receptor. -​ Absorbed photons + scattered photons that do not strike IR = total number of photons attenuated -​ Attenuation is a broad term that may be used to refer to any process decreasing the intensity of the primary photon beam 13 Effects of Attenuation on Radiographic Images ​ The less a given structure attenuates, brighter appearance on RAW DIGITAL DETECTOR IMAGE ​ The more a given structure absorbs radiation, the less radiation received by receptor and will appear darker shade of gray List two types of x-ray photon transmission and explain the difference between them. Transmitted Photons -​ Photons that strike the IR Indirect Transmission -​ Photons INTERACT with pt’s atoms but still strike the IR -​ Always the result of scatter but all scatter does not result in indirect transmission. (not all scatter hits IR) -​ Must eliminate as much indirect transmission as possible because it degrades image quality -​ Will always be present Direct Transmission -​ Photons pass through WITHOUT INTERACTING with pt’s atoms and strike the IR -​ Goal of radiographic imaging is to use the directly transmitted photons to construct the final image while eliminating indirect transmission as much as possible Explain what determines the probability of photon interaction with matter. 1.​ Photon energy density 2.​ Atomic Number Dependence 3.​ Electron Density 4.​ Physical Density PROBABILITY OF PHOTOELECTRIC ABSORPTION ​ depends on Energy of the incident x-ray photon and the Atomic # of the atoms ​ Compact bone undergoes more photoelectric absorption than an equal mass of soft tissue and air ​ Soft tissue (7.4) and air (7.6) the occurrence of photoelectric absorption is identical ​ Air permits more radiation to reach the IR – greater receptor exposure = more adequate image contrast. ​ Increased photoelectric absorption in bone (13.8) appears denser and whiter in final image than surrounding soft tissue = greater the contrast. Probability ↑ Atomic # ↑ Probability ↑ Energy of Incident Photon↓ 14 Processes of Interactions: lowest to highest energy COHERENT SCATTERING (