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 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
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).
Types of Protective barriers
Table to help you understand how the following should be used to minimize occupational dose during fluoro exams
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)
Primary, Scatter, Leakage Radiation
What unit of measure is associated with workload?
workload (W)=mA-min/week
Inverse Square Law Equation
