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Radiology > Protection > Flashcards

Protection Flashcards

(44 cards)

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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?

19
Q

What statutes does the NOMAD machine violate?

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

What is a must for hand held units?

Study These Flashcards
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?

Study These Flashcards
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?

Study These Flashcards
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?

Study These Flashcards
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?

Study These Flashcards
A

diverging lingual root of mandibular 1st molar

25
Where is hyperdontia most common?
premolar region
26
What is deterministic risk?
- severity is proportional to dose - has a threshold
27
Examples of deterministic risk
- erythema - xerostomia - cataract - osteoradio-necrosis - fertility - alopecia - fetal-development
28
What are stochastic effects?
- 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
What is the definition of maximum permissible dose?
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
What is the maximum permissible dose for operators vs non-operators?
50mSv (5 rem/year) // pregnant: 5mSv 5mSv (.5rem/year)
31
What is the source of the majority of the average annual effective dose of ionizing radiation?
natural: cosmic, terrestrial, radon (2.0) total = 3.00
32
What fraction of radiation exposure comes from medical/dental xrays?
1/6 (.52 --> 3.2) ... BUT in 2007, white paper said it increased to about 1/2 6x increase
33
How much ionizing radiation do we experience annually?
3.6mSv **jumped to 6.3mSv if lots of CT/nuclear medicine
34
To overcome this increased exposure, what must / did we do?
- justify need for xray - trained and educated
35
Why are pediatric patients at higher risk/radiosensitivity?
- rate of cellular & organ growth - greater life expectancy --> greater risk of afflicted with radiation induced cancer
36
Describe populations likelihoods of developing radiation cancer?
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
What is the average daily background radiation dose?
8.5 uSv
38
What types of cancer have the highest risk for dental radiographic exposure?
leukemia & thryoid
39
Studies show risk for congenital defects are negligible at ___?
50mSv or less
40
Is fetal development a deterministic or stochastic risk?
deterministic
40
What is the stochastic risk estimate for pregnancy?
absorbed dose ~25mGy doubles the natural childhood cancer rate from 1in 500 to 1 in 250
41
Radiation induced cancer threshold dose?
none...always a risk **risk from dental xrays not seen in doses <10mGy
42
When to request dental radiographs in pregnant women?
- if clinically indicated, justified - dose as low as diagnostically possible - if urgent tx required to benefit baby/mother --> abscessed tooth/fractured tooth, etc.
43
When NOT to request dental xrays in pregnant women?
- new patient/recall exams... wait until post-partum

Radiology (5 decks)

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