Angular Modulation
The angular-modulation technique
was introduced in 1994 for a single– detector
row helical CT scanner (Smart-
Scan; GE Medical Systems, Waukesha,
Wis) (13–15). This software-based technique
modulated tube current on the basis
of the measured density of regional
structures and the absorption values of
the object of interest. This information
was obtained by measuring local x-ray
beam absorption in 100 central channels
on two localizer radiographs (lateral and
anteroposterior views). Preprogrammed
sinusoidal modulation of tube current
was achieved during 360° rotation for
equalization of local differences in beam
absorption to obtain relatively constant
noise content and reduce radiation exposure.
A radiation dose reduction of up to
20%, depending on patient geometry
(asymmetry), has been reported (14). A
recent refinement of the angular-modulation
approach is an online, real-time,
anatomy-adapted, attenuation-based tube
current modulation technique (CARE
Dose; Siemens Medical Solutions, Forchheim,
Germany) that does not need the
information of radiographic localizer images
to achieve ATCM (1–3,16–20
Angular ModulationThe angular-modulation techniquewas introduced in 1994 for a single– detectorrow helical CT scanner (Smart-Scan; GE Medical Systems, Waukesha,Wis) (13–15). This software-based techniquemodulated tube current on the basisof the measured density of regionalstructures and the absorption values ofthe object of interest. This informationwas obtained by measuring local x-raybeam absorption in 100 central channelson two localizer radiographs (lateral andanteroposterior views). Preprogrammedsinusoidal modulation of tube currentwas achieved during 360° rotation forequalization of local differences in beamabsorption to obtain relatively constantnoise content and reduce radiation exposure.A radiation dose reduction of up to20%, depending on patient geometry(asymmetry), has been reported (14). Arecent refinement of the angular-modulationapproach is an online, real-time,anatomy-adapted, attenuation-based tubecurrent modulation technique (CAREDose; Siemens Medical Solutions, Forchheim,Germany) that does not need theinformation of radiographic localizer imagesto achieve ATCM (1–3,16–20
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Angular Modulation
The angular-modulation technique
was introduced in 1994 for a single– detector
row helical CT scanner (Smart-
Scan; GE Medical Systems, Waukesha,
Wis) (13–15). This software-based technique
modulated tube current on the basis
of the measured density of regional
structures and the absorption values of
the object of interest. This information
was obtained by measuring local x-ray
beam absorption in 100 central channels
on two localizer radiographs (lateral and
anteroposterior views). Preprogrammed
sinusoidal modulation of tube current
was achieved during 360° rotation for
equalization of local differences in beam
absorption to obtain relatively constant
noise content and reduce radiation exposure.
A radiation dose reduction of up to
20%, depending on patient geometry
(asymmetry), has been reported (14). A
recent refinement of the angular-modulation
approach is an online, real-time,
anatomy-adapted, attenuation-based tube
current modulation technique (CARE
Dose; Siemens Medical Solutions, Forchheim,
Germany) that does not need the
information of radiographic localizer images
to achieve ATCM (1–3,16–20
การแปล กรุณารอสักครู่..