Quiz 7 Flashcards
Diff. Between 3phase 6pulse & 3phase 12pulse
- reduced ripple with 12 pulse generator 3-10% ripple
* 6pulse 13-25% ripple
Ripple factor constant potential?
•less than 2% ripple
3phase generators or high frequency is approximately __% increase in kVp or almost ___ mAs over single phase power
- 12%
* doubling mAs
Generator with least ripple
- constant potential
* less than 2%
Generator with greatest exposure to patient
•single phase 100% ripple
Dose response curve for X-rays
•linear non threshold curve /
Cell biology
- 85% water
- proteins
- carbohydrates
- lipids
- nucleus acids
Gonadal shielding
- must be used when gonads are w/in 5cm of beam
* lead must be 0.5mm Pb equivalent
Cardinal principles of radiation protection?
- TIME-keep time to a minimum (directly proportional)
- DISTANCE-inverse square law the further u r the less exposure
- SHIELDING-lead aprons, thyroid shields, gloves 0.25mm Pb equivalent
Primary barrier
•protects anything the primary beam hits (wall, structure)
Secondary barriers
- protects against scatter/leakage
* stationary fixed barriers, viewing window
Whole body dose limits (occupational)
•5rem (50msv)
Extremities dose limits
•50rem (500mSv)
Lens of eye dose limits
•15rem (150mSv)
Accumulated dose limits
•1rem X age (in years)
Whole body dose frequent (public)
•0.1rem (1mSv)
Fetus total dose limit/ per month
- total 0.5rem (5mSv)
* month 0.05rem (0.5mSv)
Law of Bergonoie & Tribondeau
- some tissues are more radiosensitive than others depends on:
- primitive or stem cells *
- rapidly dividing cells *
- mitotic rate *
- high metabolic rate
- high proliferation
(Linear energy transfer)LET
- energy transferred per unit of path length
* Measures the rate of energy transferred from ionizing radiation to tissue
Low LET
- sub lethal
- not highly ionizing
- travel far
High LET
- highly ionizing
* poorly penetrating
Direct damage
- results in damage of cell
* occurs only when direct interaction with essential molecule/DNA/target molecule
Indirect damage
- results in no damage
* ionization of water
Doubling dose
•amount of radiation required to double frequency of mutation
Mitosis
- cell division
- 4 phases
- prophase
- metaphase
- anaphase
- telophase
Interphase
- period between divisions
* mitosis-G1-(S)phase-G2
1rem = ?sV
•10Sv
1Gy = ?Rad
•100rads
Ionized water creates free radicals that combine to creat hydrogen peroxide, causes breakdown of membrane permeability
•Radioloysis of water(indirect effect)
The primary beam is made up of what photons
•photoelectric
LD 50/60
•50% of the population will die with in 60 days
Most radiosensitive cell cycle
- mitosis
- late G1
- early S-phase
What is more radiosensitive high or low mitotic
•high mitotic
Relationship increase in LET= increase in?
•RBE
Relationship OER increase =
•indirect effects of radiation
Prodromal syndrome
•initial stage of disease
Latent period
•symptom free
Most radiosensitive fetal stage
•the first trimester
Somatic cell? Mitosis or meiosis?
•mitoses
Germ cell mitosis or Meiosis?
•meiosis
Vest shielding
•0.25mm Pb
What kind of interaction is produced my characteristic radiation
•photoelectric
