keywords:
Bookmark and Share



Front Back
Patient Protective Devices
1. Filtration 2. Collimation 3. Gonad Sheilding 4. Intensifying Screens
How do filtration screens work
Made of aluminum and filter out low energy low wavelength waves from primary beam
how thick should the gonad shield be
no less than 0.5mm of lead equivalent
how do intensifying screens work
convert X-rays into visible light
what type of metals do intensifying screens use
Calcium Tungstate medium speed, Rare eArth metals high speed
What is the grid ratio
height:interspace distances  
higher ratios decrease scatter but increase patient dose
List the three types of grids and their function
Focus grid - angled to focus beam
Parrallel Grid
Bucky Grid: moving to prevent grid lines
Biological Effects of Radiation are influenced by
1. DOse Rate
Total Dose
Type of Cell 
what is the difference between a rad and a rem
rad=radiation absorbed dose - 100 ergs of energy per gram of tissue
rem= rad x biological coefficient - takes into consideration biological tissue
occupational exposure limits 
Whole Body, Extremities, Eyes
Whole Body = 5 rem
Extremities = 50 rem
Eye = 15 rem
what is a radiation area
recieve 0.005 rem at 30cm from source in one hour
what is a high radiation area
recieve 0.1rem at 30cm from source in one hour
radiation dose limits for the public
0.1 rem/year
0.002 rem in any one hour 
Primary Radiation
useful part of the beam focused on the patient
Remnant Radiation
beam that passes through patient onto film
Scatter Radiation
useful radiation that passes through tissue but gets deflected
Leakage Radiation
Radiation from tube that is NOT associated with useful radiation
Secondary Radiation
Leakage and Scatter - that does not serve a useful purpose
What does secondary radiation contribute to
Patient dose Film Fog 
Factors that determine quantity of scatter radiation
Higher VOltage  Thicker Body Parts Larger Field SIze Dense Tissue 
filtration requirements
<50kVp - 0.5mm aluminum 50-70kVp - 1.5mm >70kVp - 2.5mm
radiosensitivity of cells from most to least
Lympocytes > RBC> Epithelial > Endothelial > Bone > Muscle > Nerve
typical amount of radiation exposure in foot x-ray
4mrem
mean lethal dose of radiation
450-600 mrem
list the 6 radiographic densities
Air > Fat > water > Bone > Contrast > Heavy Metal
x of y cards