Dynamic bowtie for full body helical CT, in which the WB is rapidly prototyped according to an individualized patient contour obtained from surface scanning.

<p>Dynamic bowtie for full body helical CT, in which the WB is rapidly prototyped according to an individualized patient contour obtained from surface scanning.</p

Projections of an elliptical water phantom and the bowtie profile.

<p>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 .</p

Dynamic bowtie in fan-beam geometry for a balanced flux distribution upon an equiangular detector array.

<p>(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, ).</p

Exemplary designs of the dynamic bowtie without driving components.

<p>(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.</p

Numbers of detected photons along x-rays through the head CT volume without and with the proposed dynamic bowtie (on a log scale).

<p>(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.</p

Numbers of detected photons along x-rays through the water phantom without any bowtie (on a log scale).

<p>(a) and (b) Surface displays for the numbers of detected photons for and respectively.</p

Catanionic Surfactant-Assisted Mineralization and Structural Properties of Single-Crystal-like Vaterite Hexagonal Bifrustums

Crystalline vaterite is the most thermodynamically unstable polymorph of anhydrous calcium carbonate (CaCO₃), and various morphologies can be controlled in the presence of organic additives. Constructing vaterite with minimal defects, determining its distinctive properties, and understanding the formation mechanism behind a biomimetic process are the main challenges in this field. In this paper, a unique single-crystal-like vaterite hexagonal bifrustum with two hexagonal and 12 trapezoidal faces has been fabricated through a catanionic surfactant-assisted mineralization approach for the first time. Compared with the polycrystalline vaterite aggregates, these bifrustums clearly present a doublet for Raman <i>v</i>₁ symmetric stretching mode, a low depolarizaiton ratio for carbonate molecular symmetry, and a high structural stability. These indicate a dominant position of hexagonal phase in each crystallite and confirm the Raman <i>v</i>₁ doublet characteristics of synthetic and biomineral-based vaterites. Our finding may provide evidence to distinguish vaterite with different structures and shed light on a possible formation mechanism of vaterite single crystals

Dynamic bowtie in a cone-beam geometry with a flat panel detector plate.

<p>Dynamic bowtie in a cone-beam geometry with a flat panel detector plate.</p

Dynamic bowtie in a spiral multi-slice geometry with a multi-slice detector array.

<p>Dynamic bowtie in a spiral multi-slice geometry with a multi-slice detector array.</p

X-ray spectral distributions of point-like micro-targets irradiated by some different materials.

<p>(A) electron beam energy 30keV, height of point-like micro-targets is 1.0μm; (B) electron beam energy 90keV, height of point-like micro-targets is 5.0μm.</p