What is the conventional measurement unit for dose equivalent when measuring radiation?
rem
Which unit of measurement measures the ionization in the air?
roentgen
What unit of measurement is used in the Landau (sp?) Report?
rem
What are the three pillars of radiation protection?
time
distance
shielding
Which pillar of radiation protection is directly related to dose?
time
Is it better to use restraints or yourself to hold a patient in position for an x-ray?
restraints, when possible
When your patient is a baby, to hold a position for an image, you should use:
C. a family member of the patient
By law, a fluoroscopic unit must have an audible timer that goes off ________________.
every five minutes
A fluoroscopy pedal on the floor should be of what kind, and why?
a "dead-man" type of pedal because exposure stops when the pedal is not compressed.
Ideally, when assisting in a fluoro room, you should:
A. walk out and stand behind the wall
If you double your distance from your patient during a procedure, you decrease your radiation exposure by a factor of:
4
Most of the radiation exposure that a technologist receives is from:
scatter radiation from the patient
Leakage radiation, by law, cannot exceed:
100 mR per hour when measured at one meter from the tube.
When does the technologist stand in the primary beam?
never
As you increase your distance from the patient, your exposure will increase or decrease?
decrease
What is the thickness required in a primary barrier?
1/16-inch lead equivalency
At 100 kVp or higher, what lead equivalency does a lead apron need to be?
.5mm lead equivalency
Lead gloves must be made of _____ lead equivalency. This still allows_______________.
0.25mm lead equivalent
movement and flexibility
A protective curtain on the control tower of a fluoroscopic machine needs _________ lead equivalency.
0.25mm lead equivalency
Where should a dosimeter be worn?
between the chest and the waist in the same place every day. It should not be covered when a lead apron is worn.
Annual Effective Dose:
5 rem
Annual Effective Dose for a Co-Lin student:
1 rem
annual dose limit for the lens of the eye:
15 rem
annual dose limit for the hands:
50 rem
annual dose limit for the thyroid:
50 rem
annual dose limit for the feet:
50 rem
annual dose limit for the skin:
50 rem
What does ALARA mean?
"as low as reasonably achievable"
Can we ethically set dose limits for patients?
no
the minimum standard for source-to-skin distance for stationary equipment is:
15 inches
The minimum standard for source-to-skin distance for portable fluoroscopic equipment is:
12 inches
What does PBL stand for, and what is it?
"Positive Beam Limitation" is basically automatic collimation. It adjusts to limit the radiation field to the image receptor area.
What technical factors decrease the dose to the patient?
high kVp and low mAs
The optimal kVp range for the AP Spine:
75-95
The optimal kVp range for the Chest:
110-120
The optimal kVp range for the Lateral Spine:
85-100
The optimal kVp range for the Abdomen:
75-90
The optimal kVp range for the Skull:
75-85
The optimal kVp range for an Extremity Non-grid:
55-70
The optimal kVp range for a Extremity with Grid:
75-85
What does AEC control?
time (seconds)
The NCRP recommends adding filter material with a minimum of _____ aluminum equivalent to the x-ray tube to absorb the weaker x-rays.
2.5mm aluminum equivalent
When converting from analog to digital, kVp will generally _________.
increase by 10-15 kVp (not percent)
Grid Conversion Factor
No Grid = ?
No Grid = 1
Grid Conversion Factor
5:1 = ?
5:1 = 2
Grid Conversion Factor
6:1 = ?
6:1 = 3
Grid Conversion Factor
8:1 = ?
8:1 = 4
Grid Conversion Factor
10:1 = ?
5
Grid Conversion Factor
12:1 = ?
5
Grid Conversion Factor
16:1 = ?
16:1 = 6
Will changing from a 5:1 grid to a 10:1 grid increase or decrease technical factors?
increase
Because of the change from analog to digital, is there an increased worry about habitual overexposure or underexposure?
overexposure
Does the latitude range widen or narrow when changing from analog to digital imaging?
it widens
Are technical factors for density easier to see in analog or digital imaging?
analog
Does automatic rescaling increase or decrease chances to be able to see changes in technical factors?
decrease
What is the symbol for Roentgen?
What is its SI Unit equivalent?
R
Coulomb/Kilo
What is "rad" the symbol for?
What is its SI equivalent?
Radiation Absorbed Dose
gray (Gy)
What is "rem" the symbol for?
What is its SI Unit equivalent?
Radiation Equivalent in Man
sievert (Sv)
Increase time of exposure, the dose ___________.
increases
Increase distance to exposure site, your dose _________.
decreases
Increase shielding, the dose __________.
decreases
Leakage radiation is when:
x-rays escape from the tube housing
What are the two main forms of shielding?
structural shielding
individual lead shielding
What are the two main types of structural shielding?
primary barriers (1/16th inch of lead)
secondary barriers (1/32-1/64 inch of lead)
What is the range of thickness for a lead thyroid shield?
0.25-.5mm of lead equivalent
Where do your store individual shields?
What do you NOT do to them when storing them?
On wall hooks, if possible, or at least laid flat or rolled.
Never fold, as it can cause cracks (checked annually)
The bucky slot cover minimum is ______ lead equivalency.
0.25mm
If you increase kVp, you ___________ entrance skin exposure (ESE).
decrease
Where is a contact shield placed?
between the x-ray tube and the radiosensitive organs of the patient (usually the gonads). They come in contact with the patient.
Does collimation reduce or increase the patient's radiation dose?
reduce
Does collimation improve or hamper radiographic contrast?
improve
Three main reasons we use technique charts in both analog and digital imaging:
to maintain a consistent signal intensity
to maintain a consistent radiographic contrast
they balance image quality with patient dose
The three main types of technique charts:
fixed kVp
variable kVp
technique charts designed for use with automatic exposure control (AEC) systems
What is an optimal kVp?
the ability of the x-ray beam to penetrate the anatomical structures without causing additional scattered radiation
_________ is added to the area just beneath an x-ray tube to absorb weak x-rays created inside the device that add very little to the image and greatly increase patient dose.
Filtration
What is the use of using a grid?
it absorbs scattered radiation from the patient before it reaches the image receptor and degrades the image.
When using a grid, must you increase or decrease technique to compensate?
increase
Shadow Shields don't have to touch a patient when used properly. True or False?
True
PBL reduces patient dose by automatically ________ the radiation field size.
reducing
Digital imaging algorithms can make a digital image look acceptable no matter what technical factors we use. True or False?
False
Changing the visual appearance of a digital image to match the accepted appearance for a given anatomical structure is known as automatic resolution. True or False?
False
Using kVp levels that are too _______ can result in an image with too much _______ which degrades image quality.
high
noise
The primary controller of contrast in digital imaging is kVp. True or False?
False
Using kVp to adjust for grid ratio increases in digital imaging is a viable way to adjust technique without affecting image quality. True or False?
True.
As the speed class of operation increases, noise _______.
increases
The speed class of operation for an analog image receptor is fixed. True or False?
