radiation safety

Natural background radiation contributes to ?

50% of the annual exposure (3.1 mSv)

Natural background radiation contributes to ?

what about the rest?

annual total dose?

• 50% of the annual exposure (3.1 mSv)

• medical and consumer productions contribute the other 50% (3.1 mSv)

• The average total annual dose is 6.2 mSv

• avergae backround radiation daily in USA?

• yearly?

• 73%

• 8.5 uSv

• 3.1 mSV

Most significant source of radiation?

• how much per year?

• where deposit?

• how many new cases?

• radon: 2 mSv per year

• deposit in lungs

• 10k new lung cancer

medical radiation exposure: what is half? how much is dental?

47 % of the 3.1 mSv

• 0.26%

the study of particulate and electromagnetic radiation, inlcluding ionizaing radiatio, on livng systems

radiation biology

name 5 of the examples of ionizing radiation in parriculate nad electromagnetic

• alpha, beta, neutrons

• x rays, gamma rays

Excitation vs ionization

• excitation involves raising electron to higher energy, without ejecting, ionization involves enjecting results in formation of ion

exposure: def and units

• amount of radiation producing ion pair

• Roetengen R

• SI: C/kg

Absorbed dose: definition and units

• energy imparted to matter

• Rad

• SI: gray

equilivalent dose: def and radiation

• accounts for the type of radiation (x QF or Wr)

• rem

• SI: sievert

effective dose; def and unit

• measure of radiation induced risk (* Wt)

  • to whole body

  • sum of equivalent dose to each tissue/organ * tissue weighting factor

• Rem

• SI: sievert

Event sequence in radiation injury

1. absorption of radiation

2. Excitation/ionization

3. chemical alteration

4. Enzymatic repair or development of radiation-induced effects

Enzymatic repair vs development of radiation induced effects (3x)

• Enzymatic repair: lose dose effects

  • cancer

  • heritable effects

  • effects on embryo/fetus (in-utero)

• Development of radiation induced: High effects

  • Cell killing

  • tissue/organ effects

  • Whole body effects

Direct effect of radiation

• energy of radiation is deposited directly into biologic material (more w high QF)

Indirect effect of radiation

• caused by radiolysis of water and production of free radicals

• the radiolysis of water forms ion pairs, the ejected electron adn molecule with an unpaired outer electron → free radical

• high LET radiation: (2): dominant process?

• low LET radiation (2): dominant process?

• __ is responsible for _ of the damage caused by X-rays

• high: direct action: alpha particles + neutrons

• low: x rays, gamma rays: indirect action

• Indirect action is responsible for 2/3

Indirect effect: what is most damaging? What other 3

• Worst: OH

• H2O2, HO2

Effects on cell kinetics (4): radiation

• cells most sensitive during mitosis

• spontaneous breaks in chromosome arms

• recovery: repair, low dose rates

• Cell death: failure to complete mitosis after irradiation

Stochastic effects: 4

(dose does not determine how bad of cancer)

• Main effect: cancer

• Risk is proportional to dose

• has no threshold dose

• severity is independent of dose

Determinastic effects (3)

• Includes: in utero birth defects, skin erythema, cataracts

• Has a threshold dose: above = effect happens

• Severity is proportional to dose

In stochastic: mutations increase with?

increasing with dose, increasing prob of cancer

• radiation causes more frequency of spontaenous mutations rather than new mutations

somatic cell mutations vs germ cell

• somatic:

  • main consequence: cancer induction

  • not passed

• Germ cell

  • passed on to next generation

  • potentially harmful to succeeding generations, but no evidence yet

Lw of Bergonie and Tribondeuau: most sensitive are cells that (4)

Most sensitive cells are:

• are undifferentiated

• high metabolic activity

• high mitotic rate/proflieration

• have a long dividing future (young tissues)

Sensitivity of cells: law of bergonie and tribondeu:

1. Very Highly sensitive

2. highly

3. intermediately

4. low

1. Lymphocytes, intenstinal epithelium, immature hematopoietic cells

2. mucous membranes, esophageal, bladder

3. growing bones + cartilage, fibroblasts, renal

4. Low: muscle, neurons, mature bone and cartiage

four main risk models: which is current?

1. linear no threshold

2. sub linear (lower risk at low doses)

3. supra linear (higher risk at low doses)

4. Hormesis (benefical effects at low doses)

LNT hypothesis

• doses higher than 100 mSv result in dose dependent increase in cancer risk

• Linear relationship between exposure and cancer risk

• no threshold: risk is present at any exposure level

Factors influencing radiation induced cancer (4)

• radiation dose and dose rate

• radiation quality (LET)

• Gender: females are more

• Age: younger are more

Heritable effects (3)

• when mutations occur in germ cells and are passed on

• Evidence has NOT been seen in human pop

• No statistically sig increase in genetically related disease in children of atomic bomb surviors

Effects on embryo/fetus: (4): which are deterministic, which are stochastic?

• Determinisc

  • intra-uterine death

  • growth retardation

  • developmental abnormalities

• Stochastic

  • Cancer in childhood

Effects on embryo: what dependent on?

• Preimplantation, organogenesis, fetal period

• effects are dependent on dose and stage of gestation at time of exposure

• preimplant:

  • 0-2 weeks

  • most sensitive; all or nothing

• organogenesis

  • 2-7 weeks post conception

  • Congenital anamolies

  • growth retardation

• Fetal period

  • 6-8 weeks post

  • primary: permenant growth retardation
    

What to produce x ray induced birth effects? Dental? (4)

• dose threshold: 100-250 (mSv)

• dental in range of micro (uSv)

• neither primary nor scatter dose can produce birth defects

  • only risk is childhood cancer with no threshold

Diagnostic exposure for patinets limit

NONE: consider risk vs benefits

Annual Dose limits: Occupational, pregnant, public exposure

• occupational workers: 50 msV

• pregnant: 0.5 / month

• publicL 1 msV

annual vs cumulative:

• DA at 22, starting at 18

• annual:

  • 50 Sv/year:

  • 50× 4 = 200 Sv

• Cumulative:

  • 10 mSv * age

  • 10 × 22 = 220 Sv

guiding prinicples (3)

justifcation (benefits > risk), optimization (reduce uncessary exposure), dose limitaiton (maintain limits)

Optimization

Alara/alada principle

• as

• low

• as

• resonably acheived

• diagnostically acceptble

Reducing patient exposure (5)

• use ?

• __ vs _

• __ source to skin distance

• Use _ collimation

• ?

• Use selection criteria

• film vs digital imaging

• long source to skin distance

• use rectangular collimation

• filtration

means of reducing patient exposure (4)

• use __ when possible

• ?

• Optimize? (2)

• Intrepreting?

• use sensor holders

• thyroid collars/aprons?

• Optimize exposure parameters (mill-seconds + kvP)

• interpretating the images

selection criteria:

• new patients

  • Child with primary:

  • Child with transitional

  • ADolescent with perm dentition (prior to 3rd)

  • Adult

  • Edentualous adult

• primary: selected PA or occlusal/ post BW if prox cannot be visualized (no evidence of disease - none)

• transitional: posterior BW + pano or BW + selected PA’s

• adolscent/adult: posterior BW + pano or BW + selected PA’s

  • full mouth preferred if evidence of disease/treatment

• Edentulous: based on clinical signs/symptoms

Selection criteria: recall patients: with increased risk/without: child, transition, aadolscent, adult

• with increased risk

  • Child, transitional, adolscent: posterior BW at 6-12 intervals if prox cannot be visualized

  • Adult: posterior bitewing at 6-18 intervals

• without risk

  • child, transitional: posterior BW at 12-24 if prox cannot be seen

  • adolscent: posterior bitewing at 18-36

  • Adult: posteiorr BW at 24-36

Image receptors of speeds slower than ANSI speed group __ may not be used for intraoral

• E/F (so not D either)

match and order:

• Intraoral detector

  • D

  • E

  • F

  • PSP

  • CCD, CMOS

• Dose%: 50, 30, 50, 100, 60

• D: 100 (most exposure, slowest)

• E: 60%

• F: 50%

• PSP: 50%

• CCD, CMOS: 30% (lowest exposure, fastest)

Use of long source to skin distances of __, rather than short at _, decerases exposure by?

• source to skin distance shall be at least ?

• 40 cm, 20, 10-25%

• 20 cm

Rectangular vs Round:

• _% in area reduction

• _% dose reduction (up to x dose reduction)

• Reduced ? improves contrast

• 60-70%

• 40-80% (up to 5x dose reduction)

• reduced scatter improves csontrast

Filtration: reduces patient dose by?:

X ray voltage:

• < 50

• 50-70

• >70

absorbing lower energy photons

• <50: 0.5

• 50-70: 1.5

• >70: 2.5

how do film and sensor holders decrease?

accuration positioning leads to less retakes

thryoid collars and lead aprons??

• lead aprons and collars are not neccessary to shield patients (regardless of age or pregnant)

use of proper exposure parameters

• KV: optimal for dental is between 60-70kVp

• MA:

  • PSP

    • Anterior PA: .25

    • BW + posterior PA: .32

  • Direct digital

    • Antierior PA: .10

    • posterior PA: .125

    • BW: .125

Personall Protection: awareness + avoidacne

• time: less time spent near

• distance: greater distance

• shielding

• Operator should stand at least __

• Degrees?

6 feet, 90-135 degrees

When are personal dosimeters used?

• workers are likely to receive an annual effective dose of excess of 1 mSv

• declared pregnant

X ray tubes should be inspected every?

Wisconsin state cycle is ?

1-2 years, 4 year cycle

• effective dose from:

  • Rectangular: BW psp or F speed;

  • Round: D speed film:

  • Pano

  • Multidector CT

• rectangular BW: 5 uSv

• round D speed: 400

• Pano: 20 uSv

• medical are high

the pt must be made aware of

benefits of radiographic and CBCT imaging and risks of NOT

PRegnant patients: (4)

• only when you believe it will contribute to diagnosis

• fetal wayyy below deterministic effect (42,000x lower)

• prinicple risk is post natal carcinogenesis:

  • indirect and dose is only a few (5 uSv from 2 rectangular collimated f speed)

• dose is equal to ½ day of natural background dose

Children are at higher risk: (3)

• 2-10 more sensitve than adults

• longer life expectancy

• improper setting

  • image gently