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Purpose: Combined kV–MV cone‐beam tomography (CBCT) imaging has been proposed for two potentially important image‐guided radiotherapy applications: (a) scan time reduction (STR) and (b) metal artifact reduction (MAR). However, the feasibility of these techniques has been in question due to the low detective quantum efficiencies (DQEs) of commercially available electronic portal imagers (EPIDs). The goal of the work was to test whether a prototype high DQE MV detector can be used to generate acceptable quality pretreatment CBCT images at acceptable dose levels. Methods: 6MV and 100 kVp projection data were acquired on a Truebeam system (Varian, Palo Alto, CA). The MV data were acquired using a prototype EPID containing two scintillators (a) a standard copper‐gadolinium oxysulfide (Cu‐GOS) screen having a zero‐frequency DQE (DQE(0)) value of 1.4%, and (b) a prototype‐focused cadmium tungstate (CWO) pixelated "strip" with a DQE(0) = 22%. The kV data were acquired using the standard onboard imager (DQE(0) = 70%). The angular spacing of the MV projections was 0.81° and the source output was 0.03 MU/projection while the kV projections were acquired with an angular spacing of 0.4° at 0.3 mAs/projection. Image quality was evaluated using (a) an 18‐cm diameter electron density phantom (CIRS, Norfolk, VA) with nine contrast inserts and (b) the resolution section of the 20‐cm diameter Catphan phantom (The Phantom Laboratory, Greenwich, NY). For the MAR studies, two opposing CIRS phantom inserts were replaced by steel rods. The reconstruction methods were based on combining MV and kV data into one sinogram. The MAR reconstruction utilized mostly kV raw data with only those rays corrupted by metal requiring replacement with MV data (total absorbed dose = 0.7 cGy). For the STR study, projections from partially overlapping 105°kV and MV acquisitions were combined to create a complete dataset that could have been acquired in 18 sec (absorbed dose = 2.5 cGy). MV‐only (4.3 cGy) and kV‐only (0.3 cGy) images were also reconstructed. Results: The average signal‐to‐noise ratio (SNR) of the inserts in the MV‐only CWO and GOS CIRS phantom images were 0.62× and 0.12× the SNR of the inserts in kV‐only image, respectively. The limiting spatial resolutions in the MV‐only GOS, MV‐only CWO, and kV‐only Catphan images were 3, 6, and 8 lp/cm, respectively. In the combined kV/CWO STR reconstruction, all contrast inserts were visible while only two were detectable in the kV/Cu‐GOS image due to high levels of noise (average SNRs of kV/CWO and kV/GOS inserts were 0.97× and 0.18× the SNR of the kV‐only inserts, respectively). In the kV–MV MAR reconstructions, streaking artifacts were substantially reduced with all inserts becoming clearly visible in the kV/CWO image while only two were visible in the kV/Cu‐GOS image (average SNRs of the kV/CWO and kV/Cu‐GOS CIRS with metal inserts were 0.94× and 0.35× the SNRs of the kV‐only CIRS without metal inserts). Conclusions: We have demonstrated that a high‐DQE MV detector can be applied to generating high‐quality combined kV–MV images for SRT and MAR. Clinically acceptable doses were utilized. [ABSTRACT FROM AUTHOR]

The crystal structures of Sr2[WO5] [Pna21, a = 7.2457(3) Å, b = 10.8867(5) Å, c = 5.5391(3) Å, Z = 4, Rint = 0.0671, R1 = 0.0495, wR2 = 0.0462] and Ba2[WO5] [Pnma, a = 7.3828(2) Å, b = 5.71420(10) Å, c = 11.4701(3) Å, Z = 4, Rint = 0.0294, R1 = 0.0146, wR2 = 0.0284] are revised, based on single-crystal XRD data. Furthermore spectroscopic data (infrared, Raman and UV/Vis) assisted by DFT calculations are discussed and first results on the luminescence properties of Sr2[WO5]:Eu3+ are presented. [ABSTRACT FROM AUTHOR]

The crystal structures of Sr2[WO5] [Pna21, a = 7.2457(3) Å, b = 10.8867(5) Å, c = 5.5391(3) Å, Z = 4, Rint = 0.0671, R1 = 0.0495, wR2 = 0.0462] and Ba2[WO5] [Pnma, a = 7.3828(2) Å, b = 5.71420(10) Å, c = 11.4701(3) Å, Z = 4, Rint = 0.0294, R1 = 0.0146, wR2 = 0.0284] are revised, based on single-crystal XRD data. Furthermore spectroscopic data (infrared, Raman and UV/Vis) assisted by DFT calculations are discussed and first results on the luminescence properties of Sr2[WO5]:Eu3+ are presented. [ABSTRACT FROM AUTHOR]

This work demonstrates the possibility of synthesis of cadmium tungstate at low temperatures using oxide precursors. Cadmium tungstate (CdWO4) scintillator was produced via microwave-assisted hydrothermal reaction using the precursors CdO and WO3. The methodology was based on microwave radiation for heating, which is remarkably faster than the solid-state route or conventional hydrothermal procedure. CdWO4 monoclinic (wolframite) structure was successfully obtained at 120°C for synthesis times as short as 20 min. This route does not require the use of templates or surfactants and yields self-assembled nanorods with size of around 24 ± 9 nm width and 260 ± 47 nm length. The growth mechanism for the formation of CdWO4 involves microwave-induced dissociation of the reagents and solvation of Cd2+ and WO42- ions, which are free to move and start the nucleation process. The luminescence properties of the produced nanoparticles were investigated, presenting a broad emission band at around 500 nm, which is comparable to that observed for samples produced using other chemical routes. This result highlights the great potential of the proposed method as a low-cost and time saving process to fabricate luminescent oxide nanoparticles. [ABSTRACT FROM AUTHOR]

Sb3+-activated CdWO4 phosphors were designed according to sp energy levels regularities of Sb3+ ion in some inorganic compounds. The sp energy levels regularities of Sb3+ in dozens of compounds were established with the aid of the dielectric theory of the chemical bond for complex crystals: EA = 6.2187−1.7584 he, EB = 7.019−1.957 he, EC = 7.259−1.964 he. Environmental factor h e of Cd site was calculated to be 1.6583 with the refined crystal structure and refractive index of CdWO4:Sb3+. Sb3+-doped CdWO4 was synthesized through a precipitation method and its structure was refined with the General Structure Analysis System. The transition energy of A band of Sb3+ in CdWO4 can be predicted to be 3.312 eV (374 nm), according to the relationship equation between EA and environmental factor he. By monitoring the 521 nm emission band, the excitation spectrum gives a weak excitation band peaking at 355 nm, which was assigned to the 1S0-3P1 transition of Sb3+ according to our prediction. Thus, Sb3+-doped CdWO4 phosphor was designed and synthesized successfully based on sp energy levels regularities of Sb3+ ion. This work is a great help to understand the spectroscopy of Sb3+ ion and will be useful for the design and development of Sb3+-doped phosphors for applications. [ABSTRACT FROM AUTHOR]