TCDHA RAD THEORY MIDTERM EXAM|ACTUAL
QUESTIONS AND ANSWERS|GRADED A+
Define X radiation
a high-energy, ionizing electromagnetic radiation produced by the collision
of a beam of electrons with a metal target in xray tube
Describe Ionization
- atom loses or gains electron, becomes ion
- ejected electron = negative
- remaining atom = positive
- photoelectric effect or compton scatter
Primary radiation
xray beam produced at target of anode, exits tubehead. primary or "useful"
beam
Compton scatter
evidence of ionization
,xray photon collides with outer shell electron, gives up energy to eject electron
from orbit. photon loses energy and continues in different directions at lower
energy. new, weaker photos interacts until all energy gone.
ejected electron + Compton, or recoil and has negative charge
- 62% of radiation
Coherent scatter
unmodified scatter
low energy photon interacts with outer shell electron. no change in atom
and no ionization.
xray photon scattered but no loss of energy.
8% of radiation
Electromagnetic radiation
mandmade or natural. no mass, weight or charge. travels at speed of light in
both a particle and a wave.
2 measurable energies are frequency and wavelength.
What does xray tubehead consist of
where xrays are produced. sealed glass bulb with lead, all air pumped out to
create a vacuum. immersed in oil bath to insulate and dispense heat.
,Cathode and Anode.
what does the filter of xray tube do
aluminum, 1.5-2.5mm thick. Filters out long wavelengths with poor
penetrating power.
what is collimation?
limits the radiation dose to the patient by limiting the amount of tissue that
is exposed
what does collimator do
Restricts the size and shape of the x-ray beam to 7cm or 2.75 inches
Maximum Accumulated Dose (MAD)
occupationally exposed workers must not exceed
MAD. MAD determined by age.
MAD = (N-18) x 5 rem/year
MAD = (N-18) x 0.05 Sv/year
, N=age, min age 18 to work with rad
What is max permissible dose? what are the measurements?
max dose a body is permitted to receive in a specific amount of time with little to
no injury.
sv = unit of ionizing radiation
Rem = unit of radiation dosage
5-0 rem/year (0.05msv) for workers
0.1 rem(0.001msv) non workers or pregnant workers
5 rules to the paralleling technique
Film placement - cover prescribed area
Film Position: parallel to axis, toward middle of oral cavity
Vertical Angulation: central ray directed perpendicular to film
Horizontal Angulation: Central ray directed through contacts
Film Exposure: xray bean centered on film so all areas exposed
All size receptors - horizontally or vert placed?
QUESTIONS AND ANSWERS|GRADED A+
Define X radiation
a high-energy, ionizing electromagnetic radiation produced by the collision
of a beam of electrons with a metal target in xray tube
Describe Ionization
- atom loses or gains electron, becomes ion
- ejected electron = negative
- remaining atom = positive
- photoelectric effect or compton scatter
Primary radiation
xray beam produced at target of anode, exits tubehead. primary or "useful"
beam
Compton scatter
evidence of ionization
,xray photon collides with outer shell electron, gives up energy to eject electron
from orbit. photon loses energy and continues in different directions at lower
energy. new, weaker photos interacts until all energy gone.
ejected electron + Compton, or recoil and has negative charge
- 62% of radiation
Coherent scatter
unmodified scatter
low energy photon interacts with outer shell electron. no change in atom
and no ionization.
xray photon scattered but no loss of energy.
8% of radiation
Electromagnetic radiation
mandmade or natural. no mass, weight or charge. travels at speed of light in
both a particle and a wave.
2 measurable energies are frequency and wavelength.
What does xray tubehead consist of
where xrays are produced. sealed glass bulb with lead, all air pumped out to
create a vacuum. immersed in oil bath to insulate and dispense heat.
,Cathode and Anode.
what does the filter of xray tube do
aluminum, 1.5-2.5mm thick. Filters out long wavelengths with poor
penetrating power.
what is collimation?
limits the radiation dose to the patient by limiting the amount of tissue that
is exposed
what does collimator do
Restricts the size and shape of the x-ray beam to 7cm or 2.75 inches
Maximum Accumulated Dose (MAD)
occupationally exposed workers must not exceed
MAD. MAD determined by age.
MAD = (N-18) x 5 rem/year
MAD = (N-18) x 0.05 Sv/year
, N=age, min age 18 to work with rad
What is max permissible dose? what are the measurements?
max dose a body is permitted to receive in a specific amount of time with little to
no injury.
sv = unit of ionizing radiation
Rem = unit of radiation dosage
5-0 rem/year (0.05msv) for workers
0.1 rem(0.001msv) non workers or pregnant workers
5 rules to the paralleling technique
Film placement - cover prescribed area
Film Position: parallel to axis, toward middle of oral cavity
Vertical Angulation: central ray directed perpendicular to film
Horizontal Angulation: Central ray directed through contacts
Film Exposure: xray bean centered on film so all areas exposed
All size receptors - horizontally or vert placed?
