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Intro to Radiography > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

What is Ionizing Radiation?

A

Capable of penetrating matter and possess sufficent energy to eject orbital electrons along its path

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2
Q

Two sources of Ionizing Radiation

A

Natural
Man-made

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3
Q

Types of Natural Radiation

A

Cosmic radiation from the sun

Uranium

Radium

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4
Q

Types of human made radiation

A

Nuclear industry - power plant accidents, weapons testing, disposal of by products

Radionuclides - smoke detectors

Medical and dental exposures - greatest source of human made radiation

Video monitors, suntan beds, microwave ovens

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5
Q

What is the smallest unit of radiation?

A

Photons

Quanta/Quantum when occuring in groups

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6
Q

What 3 things must exist for X-rays to be produced?

A

Electron source

Force to move them rapidly

Something to stop this movement abruptly

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7
Q

How are x-rays produced?

A
  1. Filament (electron source) is in cathode assembly - made of thoriated tungsten
  2. mA (electric current) is applied to the filament and it responds by boiling off electrons (thermionic emissions)

kV is applied to the tube terminals causing electrons to accelerate towards the anode end of the x-ray tube

  1. X-rays are produced when electrons strike anode

Both heat and energy are produced - 1% xrays and 99% heat

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8
Q

What can happen after X-rays strike matter?

A

Absorption
Scatter
Pass through unaffected - remnant radiation

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9
Q

What are the difference types of tissues by density?

A

Air
Soft Tissue
Fatty Tissue
Bone

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10
Q

Units of Measure

A

Gray - absorbed dose

Sievert - Equivalent dose or occupation dose

Coulomb/kg - Measures exposure in air

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11
Q

What is the heterogeneous beam?

A

Xray beam has many energies - measured in KeV

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12
Q

What is the primary beam?

A

Dirtected toward the patient through window

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13
Q

Most occupational exposure comes from:

A

Scatter

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14
Q

Who sets standards for radiation protection equipment?

A

Under the direction of the FDA, Center for Devices and Radiological Health (CDRH)

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15
Q

Who collects and distributes info on radiaiton awareness?

A

NCRP: National Council on Radiation Protection and Measurement

Enforced by the NRC: Nuclear Regulatory Commission

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16
Q

Two theories of effective dose limits:

A
  1. Non-threshold - no dose exist below which the risk of damage does not exist. No dose considered permissible
  2. The benefit to patient to perform exam must outweigh the risk of biological damage
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17
Q

Effective dose limit for occupational worker

A

50 mSv/year

18
Q

Effective dose limit for public

A

5 mSv/year

19
Q

Biological response to radiation (how radiation reacts with cells)

A

Ionizing radiation when absorbed by matter undergoes energy conversions that result in changes in atomic structure

In living tissue: major consequence on life of any organism

20
Q

How to minimize time for patient

A

Minimize time in path of xray beam, use technique charts to determine correct dose, minimize repeats

21
Q

When to shield gonadal area:

A

When gonadal area within 4-5 cm of primary beam

22
Q

3 types of lead shields

A

Flat Contact Shields - placed directly over gonadal area

Shaped Contact - cup shaped and fits male patient

Shadow shield - mounted to the side of the collimator of xray tube on flexible extension arm

23
Q

What is filtration?

A

In path of x-ray beam

Absorbs that lower energy xrays; reduces scatter and grays

24
Q

When does fluoroscopy time go off?

A

5 minutes

25
Q

Inverse Square Law

A

Int Inten (Fin Dis)^2
————– = —————
Final Inten (Int Dis)^2

26
Q

How much lead is in lead aprons and gloves?

A

.25 to 1.0mm

27
Q

How often does shielding need to be checked?

A

At least 1 time a year

28
Q

What is the dose limit for unborn child?

A

5 mSv for entire pregnancy
.5mSv per month

29
Q

What is dose limit if pregnancy not vocalized?

A

50 mSv/year

30
Q

Who should wear a personnel monitoring dosimeter?

A

Any worker regularly exposed to ionizing radiation who may likely receive 10% or more of effective dose limits

31
Q

What is OSL?

A

Optically Stimulated Luminescense Dosimeter

32
Q

Properties of OSL?

A

Most common

Usually worn for 2 months

Heat sealed

Strip of aluminum oxide inside is exposed to laser light, which causes luminescent in proportion to amount of radiation exposure

33
Q

Advatages/Disadvantages of OSL

A

Unaffected by heat, mosture and pressure

Inability to get immediate reading

34
Q

What is Coherent Scattering?

A

Photon strikes an atom

Atom absorbs electron and becomes excited

Atom releases excess energy in the form of another photon

Proceeds in different direction

35
Q

What is Photoelectric Absoprtion?

A

Photon strikes inner shell electron and ejects it

Travels until it combines with other matter

Outer shell electrons move to fill vacancies and they release energy in the form of xrays known as secondary radiation

36
Q

What is Compton scattering?

A

Photon strikes atom and uses a portion of energy to eject outer shell electron

Remainder of energy proceeds in different direction - can react with patient or exit

Ejected electron travels until combined with matter

37
Q

What is a primary protective barrier stuck by?

A

Primary beam

38
Q

What is secondary protective barrier struck by?

A

Scatter or leakage radiation

39
Q

What types of scattering occur within the diagnostic range of X-rays?

A

Coherent, photoelectric and Compton

40
Q

What type of scattering occurs in therapeutic range of energies?

A

Pair production
Photodisintegration

41
Q

What types of scattering directly influences patient and occupational work exposure?

A

Compton and photoelectric

Intro to Radiography (15 decks)

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