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Radiology > Protection > Flashcards

Protection Flashcards

1
Q

what is ALARA and ALADA?

A

as low as reasonably achievable / as low as diagnostically acceptable

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2
Q

What are the mandated dose reduction mechanisms for the xray tube head?

A

collimation & filtration

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3
Q

What does filtration do?

A

limits amount of low energy radiation
*which contributes to dose, but not dianostic quality

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4
Q

What is the “best” filter & what do we use / why?

A
  • Lead (blocks all rays)
  • aluminum bc blocks only low energy / increases mean energy of beam
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5
Q

What is the mandated aluminum filtration for 50-70kv?

A

1.5mm filtration

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6
Q

Maximum diameter of beam collimation on exit side? Preferred shape?

A

2.75” diameter // rectangular (not mandated tho)

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7
Q

What are optional dose reduction mechanisms for the xray tube head?

A
  • rectangular collimator
  • high kV generator/transformer
  • constant potential (DC) fully rectified
  • increased focal length
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8
Q

Why does rectangular collimation reduce dose?

A

less area exposed due to smaller area

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9
Q

What is the tru-align?

A

rectangular collimator with a magnet to help with beam alignment
– bulkier & snapping moves sensor/pt

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10
Q

What reduces the dose more rectangular vs round collimator or PSP vs CCD?

A

rectangular !!! 5x less dose

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11
Q

What are the drawback of high kV units?

A

larger, heavier, more expensive

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12
Q

T/F the higher the kV, the lower teh dose?

A

true

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13
Q

Benefits of long BID/cone length)?

A
  • 27% less head volume (exposed)
  • reduced effective dose
  • sharper image
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14
Q

What is a recessed xray tube?

A

within the tube head, the xray tube is farther back to increase the focal distance (sharper image & lower dose)

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15
Q

Practice options for dose reduction?

A
  • sensor speed (sensitivity)
  • Lead thyroid collar
  • film-holding devices with beam alignment capability
  • time-temperature or digital quality control processing
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16
Q

What type of sensor is the most sensitive to xrays? Lowers dose.

A

CCD

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17
Q

How should the operator stand during an exposure?

A
  • behind a barrier
  • 6 feet from pt & between 90-135* from beam
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18
Q

Annual occupational whole body exposure should not exceed? If pregnant?

A

50 mSv
5 mSv

19
Q

What statutes does the NOMAD machine violate?

A
  • distance from patient is NOT 6ft or behind barrier
20
Q

What is a must for hand held units?

A
  • backscatter shield must be permanently mounted to cone
  • operators wear monitor device & evaluated monthly
  • must have training
21
Q

How to maximize operator’s area of protection while using hand-held machine?

A
  • backscatter shield should be at end of PID & held close to pt
  • all body parts remain in shield’s protection
  • stand directly behind machine & parallel to floor (sensor, shield, operator)
22
Q

What should you explain to a patient who is fearful of dental radiography?

A
  • magnitude of risks is small
  • what we do to minimize risks (radiation protection)
  • benefits of radiographic examination
23
Q

What are the benefits of dental radiography?

A
  • interproximal caries dx
  • severity/depth of caries
  • PD bone loss & calculus
  • root configuration
  • periradicular pathosis
  • basal bone pathology in jaws
  • 3rd molar roots & IAC
  • anatomy assessment for implants
24
Q

What root abnormality is common in asian populations?

A

diverging lingual root of mandibular 1st molar

25
Q

Where is hyperdontia most common?

A

premolar region

26
Q

What is deterministic risk?

A
  • severity is proportional to dose
  • has a threshold
27
Q

Examples of deterministic risk

A
  • erythema
  • xerostomia
  • cataract
  • osteoradio-necrosis
  • fertility
  • alopecia
  • fetal-development
28
Q

What are stochastic effects?

A
  • no threshold
  • probability of occurrence is proportional to dose
  • severity of effects does NOT depend on dose
    **any dose there is a risk, but it is low // every time you apply it, probability rises
29
Q

What is the definition of maximum permissible dose?

A

the amount of radiation which in the light of present knowledge will not produce any serious, harmful, or deleterious effects on the individual receiving it

30
Q

What is the maximum permissible dose for operators vs non-operators?

A

50mSv (5 rem/year) // pregnant: 5mSv
5mSv (.5rem/year)

31
Q

What is the source of the majority of the average annual effective dose of ionizing radiation?

A

natural: cosmic, terrestrial, radon (2.0)
total = 3.00

32
Q

What fraction of radiation exposure comes from medical/dental xrays?

A

1/6 (.52 –> 3.2)
… BUT in 2007, white paper said it increased to about 1/2

6x increase

33
Q

How much ionizing radiation do we experience annually?

A

3.6mSv
**jumped to 6.3mSv if lots of CT/nuclear medicine

34
Q

To overcome this increased exposure, what must / did we do?

A
  • justify need for xray
  • trained and educated
35
Q

Why are pediatric patients at higher risk/radiosensitivity?

A
  • rate of cellular & organ growth
  • greater life expectancy –> greater risk of afflicted with radiation induced cancer
36
Q

Describe populations likelihoods of developing radiation cancer?

A

females <10, 5-6x more likely
males <10, 4-5x more likely
females 20-30, 3x more likely
@40 slow drop off from 2.8x more likely

37
Q

What is the average daily background radiation dose?

A

8.5 uSv

38
Q

What types of cancer have the highest risk for dental radiographic exposure?

A

leukemia & thryoid

39
Q

Studies show risk for congenital defects are negligible at ___?

A

50mSv or less

40
Q

Is fetal development a deterministic or stochastic risk?

A

deterministic

40
Q

What is the stochastic risk estimate for pregnancy?

A

absorbed dose ~25mGy doubles the natural childhood cancer rate from 1in 500 to 1 in 250

41
Q

Radiation induced cancer threshold dose?

A

none…always a risk
**risk from dental xrays not seen in doses <10mGy

42
Q

When to request dental radiographs in pregnant women?

A
  • if clinically indicated, justified
  • dose as low as diagnostically possible
  • if urgent tx required to benefit baby/mother
    –> abscessed tooth/fractured tooth, etc.
43
Q

When NOT to request dental xrays in pregnant women?

A
  • new patient/recall exams… wait until post-partum

Radiology (5 decks)

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