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Quality Assurance > Assignment 4 > Flashcards

Assignment 4 Flashcards

1
Q

a limited-access area in which the occupational exposure of personnel to radiation-producing equipment or radioactive materials is supervised by an individual in charge of radiation protection

A

controlled area

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2
Q

What is the Maximum Permissible Dose Equivalent for a Controlled Area?

A

0.1 mSv/wk (5 mSv/yr)

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3
Q

any other area in the environment; doses suitable for the general public would apply in these areas

A

Noncontrolled/Uncontrolled Area

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4
Q

What is the Maximum Permissible Dose Equivalent for a Noncontrolled / Uncontrolled Area?

A

0.02 mSv/wk (1 mSv/yr)

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5
Q

Protection through the source housing is required against what 3 types of radiation?

A
  • Primary
  • Scattered
  • Leakage
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6
Q

What is the definition of Primary Barrier?

A

a barrier sufficient to attenuate the useful beam to the required degree

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7
Q

What is the definition of Secondary Barrier?

A

the required barrier against stray radiation (leakage and scatter)

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8
Q

What is the definition of Workload? How is it expressed?

A
  • for megavoltage machines, W is usually stated in terms of weekly dose delivered at 1 m from the source. This can be estimated by multiplying the number of patients treated per week with the dose delivered per patient at 1m
  • W is expressed in dose / wk. at 1m
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9
Q

What is the definition of Use Factor?

A

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

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10
Q

What is the definition of Occupancy Factor?

A

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

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11
Q

What is the definition of Distance with regard to factors that enter into the calculation of barrier thicknesses?

A

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

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12
Q

What is the Occupancy Factor for areas occupied full-time by an individual?

A

1

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13
Q

What is the Occupancy Factor for outdoor areas with only transient pedestrian or vehicular traffic, unattended parking lots, unattended vehicular drop-off areas, stairways, and unattended elevators?

A

1/40

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14
Q

On a therapeutic source assembly over 500 kVp, what is the maximum absorbed dose rate due to leakage radiation (excluding neutrons) at any point outside the maximum field size, but within a circular plane of 2m radius that is perpendicular to and centered on the CAX at the normal treatment distance?

A

0.2% of the useful beam dose rate at the tx. Distance

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15
Q

The quality of leakage radiation is approximately the same as that of the ________.

A

primary beam.

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16
Q

Is leakage radiation more or less penetrating than scattered radiation?

A

More penetrating

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17
Q

Unless a maze entryway is provided, the door must provide shielding equivalent to the ______ surrounding the door.

A

wall

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18
Q

The _______ must be protected against neutrons that diffuse and reach it.

A

door

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19
Q

High energy x-ray beams over ___ MV are contaiminated with neutrons

A

10

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20
Q

What is better to reduce neutron contamination – designing a longer maze or adding more lead shielding to the door?

A

designing a longer maze

21
Q

Should brachytherapy sources be touched with your hands? If not, what should be used instead?

A

No, long forceps must be used

22
Q

What should be done with a leaking source?

A

A leaking source should be returned to an agency that is authorized for the disposal of radioactive materials.

23
Q

Can ionization chambers be used to measure exposure directly?

A

yes

24
Q

Is a Cutie Pie survey meter an ion chamber, G-M counter, or TLD?

A

ion chamber

25
Q

Is a Geiger-Muller Detector more or less sensitive than an ion chamber?

A

more sensitive

26
Q

Does a G-M Detector measure dose?

A

No

27
Q

Which of the following is best for finding contamination and other low levels of radiation – ion chamber, G-M detector, or TLD?

A

G-M detector

28
Q

Is a “Rascal” an ion chamber, G-M counter, TLD, or neutron detector?

A

neutron detector

29
Q

How should radiation transmitted through the primary barrier be measured?

A

Radiation transmitted through the primary barrier should be measured with the beam at max size pointed at the barrier

30
Q

How should measurements outside the secondary barrier be made?

A

• Measurements outside the secondary barriers should be made with a phantom in the treatment position

31
Q

Why would a film monitor be used instead of a TLD or OSLD?

A

Film is relatively inexpensive

32
Q

In a Thermoluminescent Dosimeter, what does the crystal substance typically comprised of?

A

typically lithium fluoride, or LiF

33
Q

What does OSLD stand for?

A

Optically Stimulated Luminescent Dosimeters

34
Q

An OSLD can be read for as long as ___ year after irradiation.

A

1

35
Q

What acceptance test is this (below)?

*box with plus sign through it **

A

Light Beam with X-Ray Beam Coincidence

36
Q

What is the tolerance for the light beam with x-ray beam coincidence test?

A

the alignment between the light beam and the x-ray beam should be within ± 2 mm or 1 % on a side

37
Q

Define mechanical isocenter.

A

the intersection point of the collimator axis rotation and the gantry axis rotation

38
Q

What may be caused by the heavy weight of the gantry frame?

A

the axis of the gantry rotation can miss the axis of the collimator rotation, thereby creating an uncertainty in the position of the isocenter

39
Q

Define wiggler.

A

an adjustable pointer device with a sharp point that may be attached to the distance-measuring rod that is attached to the accessory mount for the purpose of performing a mechanical isocenter check

40
Q

What is the tolerance for the collimator rotation mechanical isocenter check?

A

For an acceptable alignment, the isocenter should stay within a 2-mm-diameter circle when the collimator is rotated through its full range of rotation.

41
Q

What is the tolerance for the gantry rotation mechanical isocenter check?

A

The tolerance of the isocenter motion with full gantry rotation is ± 1mm.

42
Q

What do the 3 star pattern tests check?

A

Radiation isocenter

43
Q

With regard to the collimator radiation isocenter (star pattern) test, what is considered an acceptable result?

A

all the lines should intersect or pass within a 2-mm-diameter circle

44
Q

With regard to the treatment table radiation isocenter (star pattern) test, what is considered an acceptable result?

A

all the lines should intersect or pass within a 2-mm-diameter circle

45
Q

With regard to the gantry radiation isocenter (star pattern) test, what is considered an acceptable result?

A

should show the lines intersecting or passing within a 2-mm-diameter circle centered around the presumed radiation isocenter

46
Q

What does the split field test detect?

A
  • focal spot displacement,
  • asymmetry of collimator jaws, and
  • displacement in the collimator rotation axis or the gantry rotation axis.
47
Q

What is the tolerance for calibration of leaf positions?

A

Deviation of more than 20% would indicate positioning problems

48
Q

How can irregularly shaped fields using MLCs be tested?

A

Create a series of typical irregular field shapes using software, then compare that to MLC-generated fields by looking at them and radiographing them

49
Q

What is the tolerance for wedge angles?

A

Wedge angles should be within ±2 degrees

Quality Assurance (5 decks)

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