rad w6 (2. 3, 5)

indire

SKIPPED BASIC ATOM STUFF

Electron

• max 7 shells

• closest shell to nuc = highest E

Ion = atom that gained/lost an e- = electrically unbalanced

Ionization

• proc of converting atom > ion

• need sufficient E to remove an e-

• when e- removed from atom = ion pair results

Ion pair

• 1 pos ion (atom that e- was removed from

• 1 neg ion (ejected e-)

• they cont react w other unstable electrically charged ions until an electrically stable neutral atom is formed

Radiation

• emission & trasmission of E thru space/substance in form of wave/particle

Ionizing radiation

• radiation that can prod ions by remove/adding e- to an atom

• 2 groups = particulate radiation + electromag radiation

Particulate radiation (particles)

• pertain to mass, travel straight, high speed, KE

• electrons (beta particles or cathode rays)

Cathode rays = originate from xray tube

BE ABLE TO LABEL CATH/ANODE DIAGRAM

Electromagnetic radiation

• propagation of wavelike E (no mass) thru space/matter

• E spead accompanied by oscillating electric + mag fields that are at right angles to each other

• man made/occur natural

• diff E lvls (electromag spectrum)

• ionizing or non-ionizing (high E are ionizing

• travel as wave/particle

Wave concept

• velocity (wave speed)

• wavelength (crest>crest distance)**

• freq (# waves in certain amt of time)

freq (# waves in certain amt of time) & wavelength (crest>crest) INVERSELY RELATED

• when one go up other go down

• long wavelength = low freq

• short wavelength = high freq

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X-Radiation

• high E, ionizing electromagnetic radiation

• possess props of both WAVES + PARTICLES

vs

X-ray

• photons

• no mass

• speed of light

• no electrical charge

• travel in WAVES (short/high freq)

• penetrating powers

xrays are absorbed by matter

Tubehead has…

• metal housing

• insulating oil = (allow not overheat)

• tubehead seal = (alum/leaded glass) (filter xray beam)

• xray tube = (xray generating sys)

• transformer = (step up & step down) (control voltage)

• aluminum disks = (behind collimator) (filter xrays)

• lead collimator = (quality xray) (restrict beam size)

• PID = (aim & shape beam)

1. Step-down transformer

• Decreases voltage.

• Increases current to heat the cathode filament.

• Helps release electrons through thermionic emission.

2. Step-up transformer

• Increases voltage (kVp).

• Accelerates electrons from the cathode (−) to the anode (+).

• Gives electrons enough energy to produce X-rays.

SEE IMAGE FOR MACHINE BREAKDOWN

generally

• electricity is E used to make xrays

• electrical E = flow of electron thru conductor = electrical current

• need flow from cathode > anode

mA (milliamperage)

• measurement of # of e- moving thru a conductor

• SPEED, DENSITY

• total quant of xrays produced

• higher mA = darker image

kVp = kilovoltage peak

• highest voltage during exposure

• control SPEED of e- when travel from cathode > anode

• e- speed determine PENETRATING POWER & wavelength

inverse^^

timer

• regulate exposure time

• like mA control film blackening (DENSITY)

general/braking radiation

• sudden stopping of high speed e- after hit tungsten target

when e- hit nuc of tungsten atom = xray photon prod (gen rad)

• lower E bc e- slow down when get close to nuc

• 70% of xrays prod at anode

• the lost energy = xray photon (green line in image)

green line in image

types of xrays produced

1. Characteristic rad

• prod when high speed e- dislodges an inner shell (K) electron from tungsten atom (cause IONIZATION)

• remaining orbiting e- rearrange to fill vacancy

• only small % of xray prod

2. Primary rad

• xray beam prod at target of anode & exit tubehead

• primary/useful beam

• always interact w matter - mostly what we see in dent

3. Secondary rad

• x-radiation created when prim beam interact w/ matter (ex: head)

• less penetrating than prim

4. Scattered rad

• form of SECONDARY deflected from its path (by interact w matter)

• result of xray photon deflected in all directions travelling scattered

• DETRIMENTAL

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image is characteristic

• borrowed one ouer e- trying to get close to nucleus

• not clean xray bc scattered

4 possibilities of when xray photon arrive at patient

Rad biology

• study of effects of ionizing radiation on living tissue

Dr. William Rollins

• father of rad protection (not alara tho)

• some xrays dont reach film & are absorbed by patient tissue

• when absorb, chem changes occur > biologic damage

absorp/photoelectric effect (completely absorbed by patient)

compton (xray photon cause ionization w various atoms until all E gone

*refer to diagram i made*

2 mechs of rad injury

1. ionization (when xray strike tissue)

2. free radical formation (INVOLVE IN DEGENERATIVE DISEASE + CANCER)

• cell damage primarily occur thru formation of free radicals

• formed when photon ionize water (component of cells)

so what is it

• uncharged (neut) atom/molec that exist w/ single unpaired e- in its outermost shell

• highly reactive + unstable

• Free radicals are highly reactive and unstable because they have an unpaired electron.

• react with important cell structures, including DNA.

• can cause cell damage, mutations, or cell death.

Why are free radicals dangerous?

• DNA damage → Can lead to mutations.

• Cell death → Can damage tissues.

• Cancer risk → DNA mutations may increase the risk of cancer.

theories of rad injury

• most xray pass thru cell little/no damage

• but can result from…

1. direct hit & absorp of photon in cell

• DIRECT THEORY

• cell damage result when ionizing rad direct hit critical areas within cell

• ex: DNA

• occur infreq (most pass thru no damage)

2. indirect absorp of photon by WATER IN CELL + free rad formation

• photons absorbed in cell & cause formation of toxins (free rad) - damage cell

• damage not from hit

• occur FREQ bc cell is 70-80% water

Biological effects from rad (2)

1. Stochastic (CHANCE)

• no threshold (no completely safe rad dose)

• linear relationship (as dose inc, harm inc)

• severity of effect NOT dose related

• ex: genetic mutations like tumor/leukemia

2. Nonstochastic

• somatic (phys) effects that have a threshold (certain dose needed for effect)

• higher dose > more severe (but not nec linear)

• large dose need for serious issue

• ex: erythema, brun, hair loss, cataract form, infertility

Sequence of Rad Injury

1. Latent Period

• time between exposure to ionizing rad / observable clinical sign

• depend on total rad dose received & amt of receiving time

• more rad receive = faster dose rate = shorter the latent period

• ex: guy who radiated hand

2. Injury Period

• follow latent, variety of injury result in….

• cell death, cell fxn change, cessation of mitotic activity (or abnormality)

3. Recovery Period (if not then perm damage)

• not all cellular rad injuries perm

• most damage caused by low level rad repaired within body cells

• can have cumulative/additive effects if unrepaired

• ex: cancer, catarct formation, birth defects (if no recovery)

5 contrib factors to rad injury

1. total dose (type/amt/ energy lvl/ duration)

• more famage occur when large quant of rad absorbed

2. dose rate = rate at which rad occurs & absorp take place

• dose rate = dose/time

• more damage if high dose bc rapid delivery dont allow time for cellular damage repair

3. area exposed = larger = greater injury

• localized better than full body rad

4. cell sensitivity

• faster if cell rapid dividing type or young type

• radiosensitive = small lymphocte, bone marrow, reprod, young bone

• radioresistant = muscle, nerve, mature bone

5. age = child + old more suscept

• in old = thinner body tissue

Rad effects

1. Short- and long-term effects (not applic dentistry)

2. Somatic and genetic effects**** (focus on these left out rest)

3. Radiation effects on cells

4. Radiation effects on tissues and organs

Somatic & genetic effects

• biologic effect of rad classified into 2

1. somatic cells = all cells EXCEPT reprod

2. genetic cells = REPROD

these cells more sensitive to rad

• ones that div freq more sensitive to rad

• immature/not highly specialized

• ones w higher metabolism

MOST SENSITIVE = SMALL LYMPHOCYTE***

amt of exposure depend on 4 things

1. film speed = F speed film instead of D redue by 60%

2. collimation = rectangle better than round (60-70%)

3. technique = long cone paralleling

4. exposure = high KvP better

A new patient in your office is told that she is in need of a

full series of x-rays. She is concerned about the risks with

taking so many x-rays. The patient asks the dental radiographer

for more background information regarding radiation exposure.

What type of information can the dental radiographer

provide the patient?

led apron

thyroid collar

alara

dig xray

PID

led collimator

expose rate very low

A new patient presents in your office. The front desk have

looked into their insurance coverage and tells you to do

an FMS on that client and a Panoramic because their

insurance covers it.

no baseline on him (as dh) bone lvl & sus caries

age? med hist?

Voltage

KvP

• reg penetrating power of xray beam

• control e- speed from cathode>anode

• IF INC, OTHER FACTORS STAY CONSTANT

• for proper density + cpntrast = inc kvp/dec exposure time

• mainly control contrast

high kvp = more E = short wavelength

low kvp = less E = longer wavelength

kV

• control quality (wL & E of beam)

• control density (darkness)

• control contrast (grey shades)

time

• interval in which xrays produced

• measured in impulses (60/s)

• if we dec kvp, we can inc time FOR PROPER DENS/CONT

mA

• # e- or current flowing thru cathode fil

1) Distance from source of rad > patient’s skin

TARGET – SURFACE DISTANCE

2) Distance from source of radiation > tooth

TARGET – OBJECT DISTANCE

3) Distance from source of radiation to the film

TARGET – FILM DISTANCE

1. High kVp → LOW contrast

• X-rays have more penetrating power.

• Produces more shades of grey.

• Less difference between black and white.

• Called long-scale contrast.

2. Low kVp → HIGH contrast

• X-rays have less penetrating power.

• Produces fewer shades of grey.

• Greater difference between black and white.

• Called short-scale contrast.