Shielding guidelines for diagnostic x-ray installation

Question 1

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?

Answer 1

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

Question 2

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

Answer 2

Secondary radiation

Question 3

What types of radiation rquire a secondary barrier?

Answer 3

1. Scatter
2. Leakage

Question 4

How much radiation can a controlled area recieve?

Answer 4

No more than 20mSv

Question 5

How much radiation can an uncontrolled area recieve?

Answer 5

No more than 1mSv per year

Question 6

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

Answer 6

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)

Question 7

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

Answer 7

No more than .30 mSv

Question 8

What is the purpose of primary barriers?

Answer 8

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

Question 9

What is the purpose of secondary barriers?

Answer 9

To attenuate stray/scatter radiation only

Question 10

What are the 3 most common barrier materials?

Answer 10

Lead, concrete, gypsum wallboard

Question 11

True or false?

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

Answer 11

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

Question 12

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

Answer 12

K=Pd^2/WUT

Question 13

What does P stand for in the primary barrier equation?

Answer 13

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

Question 14

What does d stand for in the primary barrier equation?

Answer 14

Distance in meters from the target to the primary area

Question 15

What does W stand for in the primary barrier equation?

Answer 15

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

Question 16

What does U stand for in the primary barrier equation?

Answer 16

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

Question 17

What does T stand for in the primary barrier equation?

Answer 17

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

Question 18

What does K stand for in the primary barrier equation?

Answer 18

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

Question 19

What is the maximum permissible weekly exposure for controlled areas?

Answer 19

0.04R/week

Question 20

What is the maximum permissible weekly exposure for uncontrolled areas?

Answer 20

0.002 R/week

Question 21

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.

Answer 21

True

Question 22

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.

Answer 22

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

Question 23

What is the assumed leakage radiation in sheilding calculations?

Answer 23

Air kerma=0.876

Question 24

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

Answer 24

30 cm from the wall

Question 25

What is workload a measure of?

Answer 25

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

Question 26

How do we find the workload?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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?

Answer 28

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)**

Question 29

# True or false? The use factor for secondary protective barriers is always taken to be 1.

Answer 29

True

Question 30

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.

Answer 30

K=1.8 x10^-4

Question 31

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?

Answer 31

1

Question 32

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

Answer 32

1/2

Question 33

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

Answer 33

1/5

Question 34

What is the occupancy factor for cooridor doors?

Answer 34

1/8

Question 35

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

Answer 35

1/20

Question 36

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?

Answer 36

1/40

Question 37

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

Answer 37

1

Question 38

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

Answer 38

1/4

Question 39

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

Answer 39

1/16