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Radiographic Protection and Radiobiology > Shielding guidelines for diagnostic x-ray installation > Flashcards

Shielding guidelines for diagnostic x-ray installation Flashcards

1
Q

What are the 2 main roles of a radiation safety officer (RSO or RPO) in the design of a new or renovation of an existing x ray facility?

A
  1. Act as an advisor on all radiation protection aspects during; initial stages of construction and installation of equipement
  2. Ensure that the installation complies with all applicable regulatory requirements
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2
Q

What type of radiation is scatter and leakage considered to be?

A

Secondary radiation

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3
Q

What types of radiation rquire a secondary barrier?

A
  1. Scatter
  2. Leakage
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4
Q

How much radiation can a controlled area recieve?

A

No more than 20mSv

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5
Q

How much radiation can an uncontrolled area recieve?

A

No more than 1mSv per year

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6
Q

What information must be included about an x ray room according to SC35; section B?

A
  1. A marker indicating north
  2. The location, use, occupancy level of adjacent rooms, as well as rooms above and below
  3. The designation of the adjacent rooms, whether to be designated as a controlled or uncontrolled area.
  4. The position of all windows, doors, ect. that may affect radiation protection requriements
  5. The planned and exisiting materials to construct the room and thier thickness
  6. The application of the protective barriers (i.e. primary or secondary)
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7
Q

How much radiation can an area that has radiation sensitive populations recieve?

A

No more than .30 mSv

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8
Q

What is the purpose of primary barriers?

A

The barrier will be required to attenuate the direct x-ray beam

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9
Q

What is the purpose of secondary barriers?

A

To attenuate stray/scatter radiation only

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10
Q

What are the 3 most common barrier materials?

A

Lead, concrete, gypsum wallboard

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11
Q

True or false?

It is requried to have lead up to the ceiling in all x-ray rooms

A

False, you dont need it all the way to the ceiling

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12
Q

What is the equation for figuring out exposure per workload at a distance?

A

K=Pd^2/WUT

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13
Q

What does P stand for in the primary barrier equation?

A

P=Maximum permissible weekly exposure expressed in R/week (need to know if the area is primary or secondary)

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14
Q

What does d stand for in the primary barrier equation?

A

Distance in meters from the target to the primary area

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15
Q

What does W stand for in the primary barrier equation?

A

Workload in mA-min/week
(x-ray equipement/exposures)

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16
Q

What does U stand for in the primary barrier equation?

A

The use factor
(during exposures, what fraction of time is the beam pointed at a specific barrier)

17
Q

What does T stand for in the primary barrier equation?

A

The occupancy factor
(The fraction of time that the area under consideration is occupied by an individual)

18
Q

What does K stand for in the primary barrier equation?

A

The exposure per unit workload at unit distance in R/mA-min at 1 meter

19
Q

What is the maximum permissible weekly exposure for controlled areas?

A

0.04R/week

20
Q

What is the maximum permissible weekly exposure for uncontrolled areas?

A

0.002 R/week

21
Q

True or False?

The attenuation of the radiation beam by the patient and other materials in the way other than the specified sheilding is neglected in sheilding calculations.

A

True

22
Q

True or false?

In sheilding calculations, we take into consideration that in cross table laterals, the beam is sometimes angled. This plays into our calculations.

A

False; we assume that the radiation beam is always perpendicular to the barrier being evaluated

23
Q

What is the assumed leakage radiation in sheilding calculations?

A

Air kerma=0.876

24
Q

How far is a person assumed to be from a shielded wall in sheilding calculations?

A

30 cm from the wall

25
Q

What is workload a measure of?

A

It is the measure of the operational time or the amount of use of the x-ray equipment (mA-minutes/week)

26
Q

How do we find the workload?

A
  1. Determine avg # of exams per week
  2. Determine avg # of exposures per exam
  3. Find avg mAs
  4. Multiply one and two, to get avg exposures per week
  5. Multiply 4 by 3
  6. Divide by 60

For specific barrier in question

27
Q

How do we find the average number of mAs of an x-ray machine per week?

A

Average exposures per week x average mAs per exposure=mAs per week

28
Q

If a chest faicility is open 5 days/week, the average number of chest patients per day is 20, the avg number of images/patient is 2, and the avg. technical exposure factors are 115 kVp and 3.25 mAs, what is the workload?

A
  1. Determine avg. # of exams per week
    20 x 5=100
  2. Determine wieghted avg, number of exposures per exam=2
  3. Calculate avg mAs per exposure (3.25 mAs)
  4. Calculate avg. # of exposures per week
    (avg exams/week x avg exposures per exam=200)
  5. Calculate avg. mAs per week (avg exposures per week x avg mAs per exposure=650 mAs/week)
  6. Calculate mA-min/week
    (650/60=10.83 mA-min/week)
29
Q

True or false?

The use factor for secondary protective barriers is always taken to be 1.

A

True

30
Q

Determine the thickness of a primary barrier requried to protect a controlled area 3 meters from the target of a 150 kVP diagnostic unit having a weekly workload of 2000 mA-min. The wall has a use factor of 1. On the other side of the wall is an adjacent x ray room.

A

K=1.8 x10^-4

31
Q

What is the occupancy factor for administrative offices and receptionist areas, labs, pharmacies and other areas fuly occupied by an individual, attended wating rooms, childrens indoor play areas, adjacent x ray rooms, image viewing areas, nurses stations, x ray control rooms, living quarters?

A

1

32
Q

What is the occupancy factor for rooms used for patient examinations and treatments?

A

1/2

33
Q

What is the occupancy factor for cooridoors, patient rooms, staff lounges, and staff rest rooms?

A

1/5

34
Q

What is the occupancy factor for cooridor doors?

A

1/8

35
Q

What is the occupancy factor for public toilets, unnattended vending areas, storage rooms, outfdoora reas with seating, unattended wating rooms and patient holding areas?

A

1/20

36
Q

What is the occupancy factor for outdoor areas with only transient pedestrian or vehicular traffic, unattended parking lots, vehicular dop of areas, attics, stairways, unattended elevators, janitors closets?

A

1/40

37
Q

What is the use factor for floors of radiation rooms, walls containg vertical image receptor and any other walls, doors or ceiling areas routinely exposed to the direct radiation beam?-and secondary barriers

A

1

38
Q

What is the use factor for doors and wall areas of radiation rooms not rountenly exposed to the direct radiation beam?

A

1/4

39
Q

What is the use factor for ceiling areas of radiation rooms not routinely exposed to the direct radiation beam?

A

1/16

Radiographic Protection and Radiobiology (11 decks)

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