Dose Optimization Techniques (CTBC 24) Flashcards
_______ _______ produces quality images with the lowest possible radiation dose
Optimal dose
Tube current (mA)
Tube Potential (kVp)
Pitch
Beam Width (Collimation)
Patient Positioning
5 aspects of a CT procedure affecting patient dose
kVp controls the energy and _______ of the x-ray beam as well as the total number of x-rays in the beam
Penetrability
As pitch increases, patient dose ______
Decreases
As beam width increases, patient dose _______
decreases
The inverse relationship of beam width and patient dose relates to the _______ outside the functional beam
penumbra (off-focus radiation)
Using more detector rows (and a wide beam) results in less…
Exposure to penumbra
Removing artifact-causing objects (e.g., arms) from the scan field is especially important when using…
Dose-modulating software (Auto mA: GE; CARE dose: Siemens; SURE exposure: Toshiba)
Incomplete projection artifact
Out of field artifact
For automatic dose-modulating scans, positioning too high in the scanner makes the patient look larger, and therefore leads to
increased technique (exposure)
A technology which changes the mA during the scan based on the density of tissues imaged
Automatic Dose Modulation
Automatic dose modulation technologies use the _______ to identify the densest portions of the patient
localizer
Automatic dose modulation technologies which adjust the dose from superior to inferior
z-axis modulation
Automatic dose modulation based on projection _______ will decrease mA in the _______ projections and increase mA in the _______ projections
(x- & y-axis)
AP
lateral
AEC
Automatic Exposure Control (automatic dose modulation)
ATCM
Automatic Tube Current Modulation
(automatic dose modulation)
Smart mA
GE nomenclature for automatic dose modulation
Auto mA
GE nomenclature for automatic dose modulation
SURE exposure
Toshiba nomenclature for automatic dose modulation
CARE dose
Siemens nomenclature for automatic dose modulation
Dose Right
Philips nomenclature for automatic dose modulation
Displayed when CTDI is set to exceed predetermined dose warning values
Dose notification
Dose Notification is useful since most technologists don’t automatically recognize the CTDI values which would lead to
over-exposure
The specific CTDI dose notification values are set by
each facility
Displayed when the cumulative CTDI for a series of scans is set to exceed _______ mGy for any specific location in the patient
1000
Dose Alert
When utilizing lead shielding, it is critically important the lead not enter the scan field d/t (2)
Unacceptable level of beam hardening artifact
Increased tube output–>patient dose (when using automatic exposure control)
Unlike lead shielding, bismuth shields attenuate only _______ photons
Low-energy
A relatively recent development for minimizing dose to vulnerable body tissues such as eyes, thyroid, breasts, gonads
Bismuth Shields
_______ _______ may be placed in the scan field after localizer images have been acquired
Bismuth Shields
A small amount of image artifact may result from use of
Bismuth Shield
