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RA1004 Science And Technology > Dosimetry > Flashcards

Dosimetry Flashcards

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1
Q

What is dosimetry?

A

The measurement and calculation of radiation doses

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2
Q

What are the key learning outcomes in dosimetry?

A
  • Understand radiation dose quantities
  • Practical use in clinical practice
  • Principles of Diagnostic Reference Levels
  • Automatic Exposure Controls and optimization
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3
Q

What are the radiation core safety principles?

A

Justification
-risk vs benefit

Optimisation
-ALARP

Limitation
-staff and public

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4
Q

What does ALARP stand for?

A

As Low As Reasonably Practicable

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5
Q

What is KERMA?

A

Kinetic Energy Released per Unit Mass
Kair
Included effects of bremsstrahlung

Unit-Gray

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6
Q

What is absorbed dose and its units?

A

Measured in Gray (Gy)
Amount of energy deposited in a material

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7
Q

What is and How is equivalent dose calculated?

A

Considers harmfulness of radiation
Equivalent dose = Absorbed dose * x weighting factor

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8
Q

What unit is used for equivalent dose?

A

Sievert (Sv)

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9
Q

What is Linear Energy Transfer (LET)?

A

LET is the energy deposited per unit distance
Defines how damaging radiation is and determines its biological consequence

Higher LET+ more irreparable DNA breaks

Alpha particles have a HIgh LET

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10
Q

True or False: Gamma rays, x rays, electrons have a high LET.

A

False

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11
Q

What does the effective dose account for?

A

The sensitivity of different organs to radiation.

Some organs in the body are more sensitive to radiation than others.

A tissue weighting factor is applied

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12
Q

What is the purpose of tissue weighting factors (WT)?

A

To account for the relative contribution of each organ to effective dose

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13
Q

What is the significance of the reference air kerma?

A

Used as a surrogate for Entrance Surface Dose (ESD)

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14
Q

What is the typical risk range for developing childhood cancer from radiation exposure?

A

1 in 1,000,000 to 1 in 200

Higher dose and exam location = higher risk

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15
Q

What is DAP in dosimetry?

A

Dose (exposure) Area Product
Product of the exposure and the area it covers

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16
Q

What does CTDI stand for?

A

CT Dose Index
Beam width is not the same as slice thickness

CTDIvol - CT dose index for a volume vacancy be used to measure absorbed dose with a rotational x ray beam

17
Q

Fill in the blank: The unit for exposure is _______.

A

coulombs per kilogram (C/kg)

18
Q

Occupational Exposures in dosimetry

A

Exposures to a risk in the workplace is covered by the Health and safety at work act (HASAWA)

19
Q

How are Diagnostic Reference Levels (DRLs) established?

A
  • National dose audits
  • Local Diagnostic Reference Levels
  • Clinical indications
20
Q

What is the role of Automatic Exposure Controls (AEC)?

A

Use of ionisation chambers to optimise exposure
To optimize exposure by monitoring dose received at the detector
Terminates x rays when the dose is what has been specified

21
Q

What does the acronym ICRP stand for?

A

International Commission on Radiological Protection

22
Q

What is the typical annual occupational dose for a radiographer?

A

< 0.5 mSv

23
Q

What is the back-scatter factor (BSF) typically used in dose measurements?

A

1.2 – 1.4

24
Q

What is the relationship between DAP and distance from the focus?

A

DAP is independent of the distance to the patient
Area of skin exposed is proportional to the square of the distance from the focus

25
Q

What are the components of the effective dose calculation?

A
  • Absorbed dose
  • Radiation weighting factor
  • Tissue weighting factors
26
Q

True or False: US and MRI have an effective dose of 0.

A

True

27
Q

What does the term ‘stochastic risk’ refer to in radiation exposure?

A

The likelihood of cancer or genetic effects from exposure

28
Q

What is the significance of the Health & Safety Work Act regarding radiation exposure?

A

Covers exposures to risk in the workplace

29
Q

Quantities of radiation dose can be categorised into…

A

Direct quantities
-exposure
-karma
-absorbed dose

Derived quantities
-equivalent dose
-effective dose
-DAP
DLP
Personal dose equipemt

30
Q

What determines the Relative Biological Effectiveness (REB)

A

The LET of the radiation
The dose rate
The particle type

31
Q

Entrance surface Dos (ESD)

A

Defined as the absorbed dose at entrance surface of patient
Includes back-scattered radiation
Typically measured with TLSs

RA1004 Science And Technology (9 decks)

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