UNIT 4: Management of Imaging Personnel Dose and Radioisotopes Flashcards
Primary radiation
emerges directly from the x-ray tube collimator and moves without deflection toward a wall, door, viewing window, and so on. Because of this property, primary radiation, also is known as direct radiation. (Unattenuated beam)
Secondary radiation
radiation that has been deflected from the primary beam. Leakage from the tube housing (photons that pass through the housing) and scatter (primarily from the patient) make up the secondary radiation
Workload (W)
the radiation output weighted time that the unit is delivering radiation during the week
Attenuation
the reduction of the intensity of an x-ray beam as it goes through matter
Controlled area
a region adjacent to a wall of an x-ray room is to be used only by occupationally exposed personnel (e.g., radiographers)
Uncontrolled area
a nearby hall or corridor that is open to and frequented by the general public
Radiation area
an area in which radiation exposures may exceed 0.05 mSv (5 mrem) in 1 hour at 30 cm from a source
Isotopes
Atoms with the same number of protons but different numbers of neutrons
Radioisotopes
• Isotopes that spontaneously balance their arrangement to achieve a lower energy state.
• Unstable nuclear configuration (too many protons or neutrons)
A few have too many protons for stability, whereas others have too many neutrons, and some are just formed in higher energy states. Because of this, such isotopes spontaneously undergo processes or transformations either to rectify their unbalanced arrangement or to achieve a lower state of energy, or both. All atoms whose nuclei behave in this manner are referred to as radioisotopes.
Brachytherapy
radiation that can be delivered more advantageously by infusion or implantation of certain radioisotopes
What is the recommended annual occupational effective dose limit from the NCRP? (provide answer using traditional and SI units)
What is/ is not included in this measurement?
-50 millisievert (mSv) or 5 Rem
-does not include personal medical exposure that an employee may receive or the background exposure that all people receive
Differentiate between the lifetime effective dose and the cumulative effective dose limit
-Cumulative effective dose (CumEfD): A radiation worker’s lifetime EfD must be limited to their age in years times 10 mSv. This limit pertains to the whole body.
-Lifetime effective dose: Dose in millisieverts that does not exceed 10 times the occupationally exposed person’s age in years, or for the dose in rem, the age of the person
What is the rationale that supports radiation workers to receive a larger equivalent dose than the general public?
The workforce in radiation-related jobs is small when compared with the population as a whole. Therefore, the expectation of any measurable increase in disease in the population, in individuals, or impact upon the gene pool is negligible.
What practices can radiographers employ to support the ALARA principle?
• The principles of time, distance, and shielding
• Adequately collimating the radiographic beam
Describe how the patient may be a source of scattered radiation?
The patient becomes a source of scattered radiation as a consequence of the Compton interaction process. The radiation deflects off of the patient, causing scatter that can hit the x-ray tech or anyone nearby.
What poses the greatest occupational hazard in diagnostic imaging? What can the radiographer do to lessen their risk?
-Scattered radiation
-Beam constraint devices, such as automatic collimation, or positive beam limitation, restrict the dimensions of the radiographic beam so that its margins do not extend beyond the image receptor. This reduction in beam size decreases the number of x-ray photons available to undergo Compton scatter.
How does filtration of the x-ray beam benefit the radiographer?
Removes nonuseful low energy photons from the beam so in return this reduces scatter radiation to the radiographer
Identify two types of secondary radiation
scatter and leakage radiation
What is the minimum lead equivalent required for aprons?
0.25mm
What are the pros/cons when deciding which thickness of lead equivalent the radiographer should utilize for their aprons?
-Heavier aprons offer more protection but are heavier and cause strain on the back
-Lighter aprons offer less protection but are lighter
When should a wrap around apron be utilized?
If any personnel could have the posterior surface of their body turned toward the x ray source during a radiologic procedure
What thickness of lead equivalent for aprons is recommended?
0.5mm
The correct way to store lead aprons is to:
Lead aprons should be hung on racks or draped over a bar designed for storage
The incorrect way to store lead aprons is to _______________________________________. Why?
-be folded or crunched up in any fashion
-Because this will lead to cracks or breaks in the lead impregnated material, thereby compromising the device’s effectiveness for protection from radiation
Describe the requirements to ensure the integrity of the lead aprons
all aprons be inspected annually for cracks or other defects either by fluoroscopy or by imaging the apparel with a high kVp technique
Physical Attributes of Protective Lead Aprons: PERCENTAGE X-RAY ATTENUATION Table
(Table shows in percentages)
During which exams might the radiographer utilize the 0.5mm lead equivalent lead vs. 1 mm lead equivalent?
-With .5mm lead: low kvp exams
-With 1 mm: high kVp exams
Variations of Lead (Equivalent) Thickness of Aprons: Required Thickness
Minimum Lead Requirements of Accessory Devices: Neck & Thyroid Shield
0.5mm
Minimum Lead Requirements of Accessory Devices: Eye glasses
0.35-0.5 mm
How can technical exposure factors contribute to the radiographer’s cumulative effective dose?
For lower kVps, more mA is needed to secure a high-quality image, and therefore more significant amounts of low-energy photons are present. These characteristics of the x-ray beam lend themselves to the production of increased large-angle scatter radiation.
Conversely, higher kVp techniques:
• Increase the mean energy of the photons comprising the radiographic beam, leading to a decrease in large angle scatter
• Require lower incident photon beam intensity (i.e., lower milliampere-seconds [mAs])
Therefore, with higher selected kVp values, less side-scattered radiation is available to strike imaging personnel, and the potential EqD is reduced.
T or F: higher selected kVp values means less side scattered radiation is available to strike imaging personnel, and the potential EqD is reduced
True
What is the primary reason repeat images occur in digital imaging?
Mispositioning
How should immobilization be implemented for patients who need to be restrained?
Mechanical restraining devices should be used to immobilize the patient whenever possible. If mechanical means of restraint are not feasible, nonoccupationally exposed persons, wearing appropriate protective apparel, are to perform this function. These individuals should be positioned so that their lead-protected torsos are not struck by the primary, or direct, beam.
What absolute limitations must the radiographer be aware regarding patient immobilization?
Pregnant women should never assist in holding a patient during an exposure
What is the first thing a pregnant radiographer should consider doing?
This act is voluntary or mandatory?
-Inform her supervisor
-Voluntary
What is the facility’s responsibility when there is a pregnant radiographer?
The facility, through its radiation safety officer:
• Provides essential counseling
• Furnishes an appropriate additional radiation dosimeter for monitoring of any possible radiation exposure to the embryo-fetus
How should fetal monitoring be carried out during the pregnancy?
worn at the waist level during all radiation procedures. When a protective lead apron is used, the dosimeter should be worn at waist level beneath the apron
What type of shielding is available for pregnant radiographers?
Specially designed maternity protective aprons consist of 0.5 mm lead equivalent over their entire length and width. They have an extra 1 mm lead equivalent protective panel that runs transversely across the width of the apron to provide added safety for the embryo-fetus.
Identify and discuss how the work schedule should be implemented when a radiographer declares her pregnancy
the declared pregnant radiographer does not necessarily need to be reassigned to a lower radiation exposure position as a direct consequence of a declared pregnancy
What is the relationship between time and radiation dose to the radiographer?
The amount of radiation a worker receives at a particular location is directly proportional to the length of time the individual is in the path of ionizing radiation
How can the radiographer minimize their time of exposure during a fluoroscopic procedure?
be present in a fluoroscopy room only when needed to perform appropriate patient care and to fulfill the duties associated with the procedure
What is the relationship between distance and exposure to the radiographer? How can this relationship be mathematically expressed?
-Inversely proportional, with distance, imaging personnel will receive significantly less radiation exposure by standing farther away from a source of radiation
-Inverse square law
What materials may be used as structural protective barriers?
• Lead
• Concrete
What is the purpose of a primary protective barrier? Where are they located?
-To prevent direct, or unscattered, radiation from reaching personnel or members of the general public on the other side of the barrier
- located perpendicular to the undeflected line of travel of the x-ray beam
Describe the common design of a primary protective barrier when an x-ray beam reaches 120 kVp
• Contains of 1.6 mm (1/16 inch) lead
• Extends 2.1 m upward from the floor of the x-ray room, when the x-ray tube is 1.5 to 2.1 m from the wall in question
Identify sources of secondary radiation
Leakage from the tube housing (photons that pass through the housing) and scatter (primarily from the patient)
What is the purpose of a secondary protective barrier and where can they be found?
-Protects against leakage and scatter radiation
-Any wall or barrier that is never struck by the primary x-ray beam is classified as a
secondary barrier. This does not mean that secondary radiation cannot strike primary barriers as well. A secondary barrier should overlap the primary protective barrier by approximately 1.3 cm (1/2 inch).
Describe the common design of secondary protective barriers
the secondary barrier consists of 0.8 mm (1/32 inch) of lead
Types of Protective barriers
What is the maximum allowable exposure a radiographer can receive in the control booth in a week?
1 mSv (100 mrem)
In a well-designed facility, approximately how much exposure might the radiographer receive in the control booth?
0.02 mSv (2 mrem)
If you are assisting with a fluoroscopic procedure, what practices can you employ to reduce your occupational exposure during the exam?
• Adequate beam collimation
• Adequate filtration
• Control of technical exposure factors
• Appropriate source-to-skin distance
• Diagnostic-type protective x-ray tube housing
• Cumulative timing device (5 minute timer)
- Bucky slot cover (0.25mm lead)
- Curtain (0.25mm lead)
Table to help you understand how the following should be used to minimize occupational dose during fluoro exams
How long should the cord be to the exposure switch on a portable (mobile) x-ray machine?
Must be long enough to permit the radiographer to stand at least 2 m from the:
• Patient
• X-ray tube
• Useful beam
Where is the best place for the radiographer to stand in relation to the patient during mobile radiography? Why?
a right angle (90 degrees) to the x-ray beam–scattering object (the patient)
When working in the OR during fluoroscopic exams, what practices can the radiographer employ to minimize their dose?
Staying on the side of the patient that is away from the x ray tube (so by the image intensifier)
What type of protective shielding should the radiographer use in the OR?
0.5 mm lead apron. A neck and thyroid shield of 0.5 mm lead equivalent should also be worn.
Describe the practices a radiographer should implement to reduce patient & personnel dose during fluoro procedures in the OR
reverse the C-arm to place the x-ray tube under the table and the image intensifier over the table
What are the negative aspects of utilizing “mag mode” during fluoro procedures in the OR?
requires higher mA, which produces additional radiation exposure
How can last image hold reduce patient dose?
no need to expose the patient again to review patient position
How can changing the beam entry location reduce patient dose?
reduce the total dose to any one area of skin
How can continuous vs pulsed mode fluoroscopy reduce pt dose?
Reducing the use of continuous fluoroscopic mode relative to the pulsed mode of operation
How can utilizing 15 imaging frames/ second vs. 30 imaging frames/ second reduce pt dose?
15 frames/ sec reduces exposure
Which NCRP limit should interventional physicians be mindful of and how can they protect themselves from reaching this limit?
-An annual EqD limit to localized areas of the skin and hands of 500 mSv (50 rem)
-Protective gloves
Primary, Scatter, Leakage Radiation
What unit of measure is associated with workload?
workload (W)=mA-min/week
What technical exposure factor(s) is/ are associated with workload?
mA and S (Seconds)
Discuss the Inverse Square Law (ISL), how it relates to radiation protection of personnel and barrier shielding requirements.
The intensity of the x-ray lessens as the distance increases. More distance means less shielding requirements.
Inverse Square Law Equation
What protective barrier / shielding should be implemented if primary or secondary radiation is never directed at a particular wall or structure?
existing construction is sufficient
What parts of the x-ray room will not be exposed to radiation?
Most structures in a diagnostic x-ray suite are struck by radiation to some degree
What type of protective barrier/ shielding should be used if no one will ever be present on the other side of the wall of an x-ray room?
Existing construction
Identify and explain the rationale for the maximum allowable equivalent dose for the following areas:
● Controlled area:
● Uncontrolled area:
● Controlled area: used only by occupationally exposed personnel (e.g., radiographers). 1000 µSv or 1 mSv.
● Uncontrolled area: a nearby hall or corridor that is open to and frequented by the general public. 20 microsieverts (20 µSv or 2 mrem).
How does identification of a controlled or uncontrolled area affect the shielding design of an imaging department?
Controlled area requires more shielding
Briefly summarize how the protection planner determines how much lead/ shielding should be used on a primary barrier
Is the barrier primary or secondary?
Is the area beyond the barrier controlled or uncontrolled?
If a primary barrier is likely to receive secondary and/ or leakage radiation, how does the shielding design of the x-ray room need to be adjusted?
no additional shielding against secondary radiation is needed for areas already protected against primary radiation
What assumptions are made when designing shielding for an area that receives scatter radiation?
- The energy of the scatter radiation is conservatively considered to be equal to that of the primary radiation.
- The intensity of radiation scattered at 90 degrees at a distance of 1 m from its source is reduced by a factor of 1000 relative to the primary radiation for a field size of 400 cm2
What is the maximum limit allowed regarding leakage radiation?
cannot exceed 100 millitoentgens (mR) per hour or 0.88 milligray (mGy) air kerma per hour
What requirements do some states employ regarding “beam-on” signage?
Warning lights that are stand out near the door to the examination room from any corridor. The sign should read “x-ray beam on” or the equivalent and be self-illuminating whenever the x-ray equipment is energized.
Where might someone find radiation warning signs?
-On the door to CT and interventional x-ray rooms
-Linear accelerator treatment rooms
-Storage areas for radioactive materials
If radiation exposures exceed those in diagnostic radiology, give examples of “special” signage someone may come across and in which departments these might be located?
-High Radiation
-Very High Radiation
-Airborne Radioactivity
-Radioactive Materials
-Departments these might be located: Radiation Oncology and Nuclear Medicine
What happens if an isotope is “unstable”?
Undergoes changes and becomes radioactive (produces radiation)
Where can a radiographer reference the procedures to dispose of radioactive materials?
radiation safety program of the institution
Identify the practices personnel should use when handling & disposing of radioactive materials.
-Must wear gloves if the isotopes are in liquid form
-Be equipped with personnel dosimeters (whole body and extremity, the latter in the case of close handling)
-Follow the cardinal rules of radiation protection (time, distance, and shielding) where applicable
-No solid encapsulated radioactive source is ever to be touched directly by hand. Instead, long tongs, which add distance as a safety measure, should be used.
Where should leftover radioactive materials be placed and how should they be labeled?
-A residual isotope is to be returned to its shielded container
-That container should then be labeled with how much activity remains and the current date
How should radioactive contaminated items be handled, stored, and disposed of?
Any contaminated items are to be placed in a sealed plastic bag that is labeled with the name of the radioisotope and the current date. After this is done, all involved personnel are to be checked with the survey meter to ensure that they have not been contaminated. Then the remaining isotope (if it is not to be returned to its supplier) and the packaged contaminated items are to be placed into a secure, shielded, and posted storage area where they must be held for a period of 10 half-lives before being suitable for disposal in ordinary trash.
In what modalities might a radiographer most likely encounter radioisotopes/ radioactive materials?
Nuclear medicine, PET/CT, Radiation therapy
During an emergency situations, what is the dose limit for individuals engaged in:
● Nonlifesaving activities?
● Lifesaving activities?
● Nonlifesaving activities: 50 mSv (5 rem)
● Lifesaving activities: 250 mSv
Which organization has outlined dose limits for lifesaving and non-lifesaving events?
Environmental Protection Agency (EPA)
Contrast how patients suffering from surface contamination vs. internal contamination should/ might be managed by medical personnel
-For surface contamination, the clothing of individuals who have been contaminated should be placed in plastic containers and set aside for later evaluation. Removal of surface contamination involves removal of the patient’s clothing and the use of a shower to cleanse the skin. Personnel should wear gowns, masks, and gloves when working with the patient
-For internal contamination:
• Dilute contaminants with fluids
-IV and/ or Oral
• Administer medications to block absorption in the GI tract(emetics, charcoal, laxatives)
EfD limit allowed for individual members of the general population not occupationally exposed. That limit is:
• 1 mSv (100 mrem) for continuous or frequent exposures from artificial sources other than medical irradiation and natural background radiation
• 5 mSv (500 mrem) for infrequent annual exposure
CumEfD limits do not include:
• Radiation exposure from natural background radiation
• Exposure acquired as a consequence of a worker’s undergoing medical imaging procedures
CumEfD limits do include the possibility of
• Internal exposure
• External exposure
Is patient scatter greater at entrance or exit
Entrance
Diagnostic imaging personnel are potentially subjected to the highest occupational exposure during:
• Fluoroscopy: fixed and mobile
• Mobile radiography
• Special procedures
• Interventional surgery
Radioactive decay
• Unstable isotopes undergo changes to stabilize
• Half life
What unit of measure is used for Use Factor
U
What unit of measure is used for Occupancy Factor
T
Most common isotope used in nuclear medicine
TC-99
The _________ of a radioisotope is the amount of time needed for its radioactivity to be reduced to one-half its original value.
Half life
Which radioactive material is the most concerning for occupational exposure?
Fluorine - 18
