Term
| What types of radiation are primary barriers and secondary barriers designed protect against? |
|
Definition
Primary: primary or useful beam
Secondary: secondary (scatter + leakage) |
|
|
Term
| Control booth walls are always designed to be what type of barriers? |
|
Definition
|
|
Term
| How are primary barriers installed in relationship to the primary beam? |
|
Definition
|
|
Term
What are the 5 factors in determining the thickness of protective barriers? |
|
Definition
1) Distance from x-ray source 2) Occupancy factor (T) 3) Workload (W) 4) Use factor (U) 5) Maximum kVp used in room |
|
|
Term
| What is the relationship between distance from x-ray source and thickness of barrier? |
|
Definition
| inverse (shorter distance, greater thickness) |
|
|
Term
| The occupancy factor (T) is what? |
|
Definition
| The amount of time the area behind the barrier is occupied. |
|
|
Term
| What are the three types of occupancy factors? |
|
Definition
T=1 - 100% occupancy - any controlled area
T=1/4 - partial (25%) occupancy
T=1/16 - occasional occupancy |
|
|
Term
| What would the occupancy factor be for restrooms not routinely used by occupational workers, such as the bathroom attached to an x-ray room? |
|
Definition
| T=1/4 or partial occupancy |
|
|
Term
| What is the occupancy factor for restrooms NOT used by occupational workers? |
|
Definition
| T=1/16 or occasional occupancy |
|
|
Term
What does workload measure? What unit is used? |
|
Definition
The amount of exposures and radiation output per week. The unit used is mA-minutes/week. |
|
|
Term
A busy room will have a workload of about _____ and require more shielding. |
|
Definition
|
|
Term
Example problem for workload: A room is in operation 5 days a week, averaging 20 patients/day at 3 views per patient with average technique of 30 mAs/image. What is the workload? |
|
Definition
30 mAs/image x 5 days/week x 20 patients/day x 3 images/patient = 9,000 mAs/week divided by 60 seconds = 15 mA-minutes/week. |
|
|
Term
| What is the use factor (U)? |
|
Definition
| The percentage of time the x-ray beam is on and directed toward a particular barrier. |
|
|
Term
| Another term for use factor is: |
|
Definition
|
|
Term
| Which barriers are generally full use (U = 1)? |
|
Definition
| Those routinely exposed to the useful (primary) beam - floors of x-ray rooms, doors, ceilings, and walls can all be full use, depending on the use of the room. |
|
|
Term
| Which barriers are partial use (U = 1/4)? |
|
Definition
| Doors and walls not routinely exposed to the primary beam, floor of a dental unit. |
|
|
Term
| What type of barrier is occasional use (U = 1/16)? |
|
Definition
| Ceilings of rooms not routinely exposed to primary beam. |
|
|
Term
| What is the use factor for ALL secondary barriers? |
|
Definition
| U = 1 (because scatter is constant.) |
|
|
Term
| In a general purpose x-ray room, with the tube 5 to 7 feet from the barrier, how high should the primary barrier be? |
|
Definition
|
|
Term
| When must protective apparel be made available to be worn? |
|
Definition
| When exposure rate could exceed 5 mR/hour. |
|
|
Term
Lead aprons must: Have a lead equivalence of _____ and cover _____% of active bone marrow |
|
Definition
Lead equivalence of 0.5 mm, cover 75% to 80% of active bone marrow. |
|
|
Term
| Lead gloves must be what thickness? |
|
Definition
Required: 0.25 mm Pb equivalence. Preferred: 0.5 mm Pb equivalence |
|
|
Term
| What is the requirement for thyroid shields? |
|
Definition
Must have 0.5 mm Pb equivalence. They are available in 1.0 mm thicknesses. |
|
|
Term
How much can wearing a thyroid shield reduce exposure to this gland? |
|
Definition
|
|
Term
| What is the lead requirement for safety glasses? |
|
Definition
| Must have 0.35 mm Pb equivalence. |
|
|
