Figure 1.
Dynamic bowtie in fan-beam geometry for a balanced flux distribution upon an equiangular detector array.
(a) No object in the field of view (FOV) corresponds to a liquid highly attenuating bowtie (HB); (b) an elliptical phantom in the FOV corresponds to the HB containing a weakly attenuating bowtie (WB) that compensates for the attenuation due to the phantom; and (c) the WB is synchronously rotated with the gantry for dynamic compensation (for example, ).
Figure 2.
Dynamic bowtie in a cone-beam geometry with a flat panel detector plate.
Figure 3.
Dynamic bowtie in a spiral multi-slice geometry with a multi-slice detector array.
Figure 4.
Exemplary designs of the dynamic bowtie without driving components.
(a) A dynamic bowtie for fan-beam CT, (b) and (c) for cone-beam CT and spiral multi-slice CT respectively. The attenuating liquid for HB is solution. The WB material is air. The containers for HB and WB are made of 0.5 mm thick aluminum and 0.2 mm thick plastic, respectively.
Table 1.
Parameters used for the design of a dynamic bowtie.
Figure 5.
Projections of an elliptical water phantom and the bowtie profile.
The projection angle is indexed by the projection number
,
,
. The ray angle
is indexed by the horizontal detector number,
. The ray angle
is indexed by the vertical detector number,
. (a)–(b) Surface displays of the sinogram from a water phantom for
and
respectively, and (c) the bowtie profile for
and
.
Figure 6.
Numbers of detected photons along x-rays through the water phantom without any bowtie (on a log scale).
(a) and (b) Surface displays for the numbers of detected photons for and
respectively.
Figure 7.
Numbers of detected photons along x-rays through the water phantom with the proposed dynamic bowtie (on a log scale).
(a) and (b) Surface displays for the numbers of detected photons for and
respectively.
Figure 8.
Head CT model approximated as an ellipse of semi-major axis mm and semi-minor axis
mm.
Figure 9.
Numbers of detected photons along x-rays through the head CT volume without and with the proposed dynamic bowtie (on a log scale).
(a) and (b) Numbers of detected photons assuming without a bowtie for
and
respectively. (c) and (d) Numbers of detected photons assuming
with a proposed bowtie for
and
respectively.
Figure 10.
Dynamic bowtie for full body helical CT, in which the WB is rapidly prototyped according to an individualized patient contour obtained from surface scanning.