Radl 70 Protection of the patient
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what happens when too high of a kVp is chosen?
- will reduce dose
- may degrade image quality
what happens to the scatter as the kvp increases?
scatter also increases
true or false: kvp changes are not recommended for controlling density
true or false: fixed kvp techniques with variable mAs are best
true or false: mAs and intensity are inversely proportional
- they are directly proportional
what does filtration accomplish?
lessens skin dose = patient dose decreases
what does filtration absorb?
- low wavelength radiation
- does not contribute to image quality
for 50-70 kvp, the total filtration must be how much aluminum lead?
1.5 mm Al
for above 70 kvp the total filtration must be how much aluminum lead?
what is the difference between an inherent filtration and added filtration?
- inherent = tube housing (0.5 mm)
- added = outside of tube housing (2.0 mm)
- total filtration = inherent + added
What is a compensating filtration?
- used to compensate for differences in tissue density
- especially for scoliosis studies
what are two types of compensating filtration?
- wedge filters- feet
- trough filters- chest
what does a compensating filter accomplish?
- cuts exposure by half
- eliminates need for two films
what do grids accomplish?
- absorb scatter radiation
- improves film quality
when do you use a grid?
when part thickness is over 10cm
how much more do bucky grids absorb scatter radiation than stationary grids?
what is required with technique selection when using grids?
requires technique increase
how much reduction in radiation to the eyes when positioning the patient into a PA skull instead of an AP skull?
which projection will reduce the breast dose to 1% of its original value if used for a scoliosis film?
which projection of a chest x-ray reduces dose to the chest and sternum?
true or false: rotating the scapula out of the way on a chest xray reduces dose
- AEC will pick up the scapula if not out of the way
as film and screen increase, the amount of radiation necessary to expose film decreases or increases?
what do higher speed films do to the quality of an image?
what are two types of image receptors (for film)
What is beam limitation?
collimating from an 8x10 to a 6x6 field will reduce dose by how much?
collimation must be accurate to within how much of the SID to be within standards?
- or 0.8 inches for a 40 inch SID
what happens to the image quality when you use collimation?
gonadal shielding should be used when the gonads are within how many inches of the primary beam?
- 2 inches
- unless it will interfere with exam
where does a gonad shield go for males and females?
- sym pub for males
- ASIS for females
what are some types of shielding?
- flat contact shields
- shaped contact shields
- shadow shields
- figleaf shields - for female
- contact lens
- breast shields- scoliosis, humerus, and shoulder girdle
- shielding must always be placed accurately to be of value
shielding will result in a reduction of how much for males?
- for ex. male gonads can be shielded during hips, femur, etc but not for female gonads
shielding will result in a reduction of how much for females?
- female gonads are in the primary beam
what do immobilization divices accomplish?
used to battle voluntary motion
what can best handle involuntary motion?
cutting exposure time
what is the best method for immobilization?
communication and pt comfort
what is the average repeat rate for radiogrphers?
when an equipment is always malfunctioning and nothing is being done about it, where can you anonymously report the issue?
california health branch
based on quality assurance guidelines set by NCRP, the recommended amount for half value layer should be how much?
2.3-2.5 mm Aluminum at 80 kvp
based on quality assurance guidelines set by NCRP, the recommended variance limit of light/beam congruency is what?
+/- 2% of SID
based on quality assurance guidelines set by NCRP, the recommended variance limit of CR alignment is what?
+/- 2% of SID
based on quality assurance guidelines set by NCRP, the recommended variance limit of PBL/cassette congruency is what?
less than 3% of SID
based on quality assurance guidelines set by NCRP, the recommended variance limit of beam area indicator on collimator is what?
+/- 2% of SID
based on quality assurance guidelines set by NCRP, the recommended variance limit for SID indicators is what?
based on quality assurance guidelines set by NCRP, the recommended variance limit for mA linearity is what?
+/- 10% between adjacent mA stations and +/- 50% overall
based on quality assurance guidelines set by NCRP, the recommended variance limit for mA reproducibility is what?
based on quality assurance guidelines set by NCRP, the recommended variance limit for grid uniformity is what?
+/- 10% variation density anode to cathode
based on quality assurance guidelines set by NCRP, grid alignment should have the highest density where?
what are the indicators of patient dose?
- entrance skin exposure
- skin dose
- bone marrow dose
- gonadal dose
- fetal dose
NCRP consideres increase risk of malformation at how many rads to a pregnant patient?
when is a pregnant patient most vulnerable?
10th day to 10th week of gestation
true or false: if used properly, computed radiography can lessen dose
pediatrics are more at risk of developing harmful effects of radiation due to what?
increased life span
what are some things to consider when protecting the pediatric patient?
- faster speed screens should be used
- lower ratio or no grids should be used
- limit comparison views
- use optimum kvp
- make sure beam alignment is accurate
exposure rate in fluoroscopy should not exceed how much? it cannot exceed by how much?
- cannot exceed 10R/min
- should not exceed 5R/min
source to tabletop distance in fluoroscopy cannot exceed by how much for fixed and mobile units?
- 15 inches for fixed units
- 12 inches for mobile units
how much should filtration in fluoroscopy be?
- 3.0 is better due to higher kvp used
what is the regulated fluoroscopy timer?
what is the protective barrier?
- barrier that intercepts radiation that goes through the patient
- floor, ceiling, wall
what is the required primary protective barrier for fluoroscopy?
- 2 mm
- it is on the image receptor
what is the entrance skin exposure during cinefluorography?
if 60 frames/sec are used during cinefluorography, how much radiation is that?
what is the typical fluoro time in cinefluorography?
13 mins and 110 secs
during high level fluoroscopy, what is the table-top dose rate limit?
cannot exceed 5R/min
what is the maximal dose to the breast?
300 mrad/view when exposing 4.5cm compressed breast
what factors influence the patient's dose in CT?
- noise level
- pixel size
- slice thickness
- technical factors used
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