Lecture 4 Flashcards
What organizations are over radiation?
International commission on radiation protection (ICRP) and national council on radiation protection and measurements (NCRP)
What do the ICRP and NCRp do?
Collect and analyze data regarding ionization radiation and put forth recommendations on radiation protection
What are the different federal regulatory groups over radiation
NRC, FDA, FEMA, OSHA, EPA
Which organization regulated radiation in AL?
Alabama Department of Public Health Office of Radiation
Radiation interaction with matter
Water is key to radiation damage producing free radicals
Indirect radiation damage
Inside cell HO- + HO- form hydrogen peroxide free radical (H2O2)
Migrates to nucleus and causes damage
Direct radiation damage
Damage to DNA subsequent to impact from a high energy photon
Deterministic effects of radiation exposure (non- stochastic)
Minimum threshold dose must be attained for the effect to occur (above causes deaths or degeneration of a large # of cells)
Ex: hair loss, cataract, skin, sterility
Stochastic effects of radiation exposure
May occur after any amount of exposure (no threshold)
Ex: leukemia and genetic defects
Early/ acute radiation injury reactions
In proliferating, renewing tissues (mm, skin, GI, BM) within days or weeks
Could be reversible
Acute radiation syndrome
BM: @ lowest radiation dose, whole body dose 3-8Gy)
GI: whole body exposure (>10Gy)
CNS: whole body >100Gy
Late effects of radiation injury
After months or years in slowly or non prolif. Tissues (CNS, kidney, liver, lung)
Improves but never repaired
Myelopathy and lung fibrosis
Shielding
PPE equipment
Lead apron (0.5mm), gloves (0.25mm), thyroid shield (0.5mm), eyewear (0.35mm)
Maximizing distance
Double the distance, 25% the exposure by a factor of 4
Exposure
Total electrical charge per unit mass of dry air generated by x or gamma rays (energy)
Unit: roentgen (R)
Absorbed dose
Amount of energy per unit mass, absorbed by the irradiated object
Unit: rad
SI unit: Gray (1gy = 100 rads)
Dose equivalent
A measure of radiation specific biological damage (in humans)
Unit: rem
SI unit: Sievert (1 Sv=100 REM)
Occupational dose limits for adults working radiation areas
NCRP guidelines state that 5rem per year is a maximum permissible dose
Occupational dose limits for General public
The dog should not exceed 1mSv/ year
Radiation exposure (in rem) for diagnostic exposures with small animal cases
Cervical spine: 0.002
Extremity : 0.001
Chest (2 views): 0.00007
Abdominal (multiple views): 0.245
Occupational dose limits for embryo or fetus declared in pregnant individuals
The dose should not exceed 5 mSv
Computed Tomography (CT) and Fluoroscopy (C-RAM)
Higher radiation doses
CT exams must be justified
Additional training required before use
How id kVp determined?
Measure patient @ thickest pt. to be radiographed
kVp= (2 x cm) + 50
add 2 kVp for each cm up to 80 and add 3 after
What happens if the image is overexposed?
↓ kVp by 10-15%
↓ mAs by 1/2
