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Dosimetry Physics 2 > Radiation Protection II > Flashcards

Radiation Protection II Flashcards

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1
Q

What are protective barriers put in place for?

A

ensure the dose equivalent receiving by any individuals does not exceed the maximum permissible value

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2
Q

What is a public/uncontrolled area?

A

area that is not under direct supervision of a radiation protection supervisor or there is no direct exposure

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3
Q

What is a controlled area?

A

An area that is under supervision of a radiation protection supervisor or there is direct exposure

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4
Q

What is the limit for a public/uncontrolled area?

A

0.02 mSv per week or 0.02 mSv in any one hour

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5
Q

What is the limit of a controlled area?

A

0.1 mSv per week

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6
Q

What does limitation of a public/uncontrolled area correspond with?

A

Limit of a public individual of 1 mSv/yr

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7
Q

What does limitation of a controlled area correspond with?

A

The limit of a pregnant radiation worker of 0.5 mSv/month

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8
Q

Shielding protection is based off what 3 types of radiation?

A

Primary, Scatter and Leakage

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9
Q

What is a primary barrier?

A

barrier sufficient to attenuate the useful beam to the required degree

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10
Q

What barrier is directly radiated by the primary beam?

A

Primary Barrier

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11
Q

What is the secondary barrier?

A

barrier for stray radiation (leakage and scatter)

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12
Q

What barrier received scatter from patient, surfaces of the treatment room, and radiation through linac shielding?

A

Secondary Barrier

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13
Q

what are some factors that are considered for barrier thickness?

A

neglects patient attenuation, perpendicular beam assumption for effective thickness, assuming head leakage to be max allowed, occupancy factors are high, and minimum distance is set at 0.3m

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14
Q

What is workload?

A

weekly dose delivered at 1m from the source, can be found be multiply # of patients per week times the dose delivered per patient

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15
Q

What is a use factor?

A

fraction of the operating time during which radiation under consideration is directed towards a particular barrier

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16
Q

What is the G0 factor from khan?

A

31%

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17
Q

What is the G90 factor from khan?

A

21.3%

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18
Q

What is the G270 factor from khan?

A

21.3%

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19
Q

What is the G180 factor from khan?

A

26.3%

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20
Q

What is the occupancy factor?

A

fraction of the operating time during which the area of interest if occupied by an individual

21
Q

What is the distance factor?

A

area in meters from the radiation source to the area to be protected

22
Q

What is the Maximum permissible dose equivalent (p)?

A

Max dose per week allowed in an area outside the treatment room.

23
Q

What is the maximum permissible dose for a controlled area?

A

0.1 mSv per week

24
Q

What is the maximum permissible dose for a uncontrolled area?

A

0.02 mSv per week

25
Q

What is the transmission factor for the primary barrier?

A

transmission factor for the barrier to reduce the primary dose to maximum permissible dose in the area of interest

26
Q

What is the maximum permissible dose equation?

A

P= WUT/d^2 x Bp

d= Distance equal from the xray target to a point of 0.3m point beyond the wall
P= dose per week required outside the barrier
27
Q

What is the transmission factor equation?

A

Bp= P x d^2/ WUT

d= Distance equal from the xray target to a point of 0.3m point beyond the wall
P= dose per week required outside the barrier
28
Q

Equation to find the barrier thickness for the primary barrier?

A

n= -log10(B)

B= transmission factor

29
Q

Due to what makes the thickness of the 2nd TVL greater than the first and so on?

A

Beam hardening?

30
Q

Equation to find the thickness for primary and leakage radiation?

A

T=TVL1 x (n-1)TVLe

31
Q

What is transmission factor for the secondary barrier for scattered radiation?

A

Bs= (P/(alpha) WT) x (400/F) x d^2 x d’2

32
Q

What is transmission factor for the secondary barrier for leakage radiation?

A

BL= P x d^2 / 0.001 WT

33
Q

What is to be said if the scattering angle is small?

A

The scattered beam has greater penetration/energy and also more of the incident beam is scattered

34
Q

What is the relation of the quality of leakage radiation in comparison to primary beam?

A

Same quality

35
Q

What is the purpose of a maze entranceway?

A

prevent direct incidence of radiation at door

36
Q

If no maze entranceway is present, what is a requirement for a the door?

A

Higher shielding, equivalent to the wall surrounding the door

37
Q

What is the inner maze walls task?

A

To be sufficiently shielded to be able to stop leakage radiation and significantly reduce intensity and energy of the scattered radiation going towards the door

38
Q

If designed appropriately, what is the required shielding in the door?

A

6mmm of lead

39
Q

What is required of maze and door shielding when utilizing 10 MV

A

Should provide adequate shielding against neutron contamination

40
Q

With a long maze, the door receives reduced neutron fluence. True or False?

A

True

41
Q

3 factors about mazes?

A

typically 8m long, reduced photon fluence at door, reduce neutron fluence at door

42
Q

What type of barriers are typically sufficient in protecting against neutrons? Whats different about the door?

A

Concrete is typically sufficient and the door must be shielded for the neutrons that diffuse into the maze and towards door

43
Q

What is used to shield against neutrons in doors, duct and has density of 1.0?

A

Borated Polyethylene (BPE)

44
Q

What is conducted after installing a new linac?

A

Survey

45
Q

How should shielding be evaluated?

A

Under the worse conditions (Open field, largest field, no attenuating structure for primary beam, large attenuating structures for scatter

46
Q

How is head leakage verified?

A

Wrapping the linac head with film

47
Q

How is room shielding verified?

A

Ion chambers and neutron detectors

48
Q

In the case of cyberknife, what can be said about the walls?

A

Most are primary due to it being non-isocentric

49
Q

What is the use factor for a cyberknife?

A

0.05 due to small beamlets used during treatment which point to different sections of the wall

Dosimetry Physics 2 (6 decks)

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