Scatter-to-primary ratio in dentomaxillofacial cone-beam CT: effect of field of view and beam energy

Objective: The aim of this study was to evaluate the effect of field of view (FOV) and beam energy on the scatter-to-primary ratio (SPR) in dental cone-beam CT (CBCT). Methods: An anthropomorphic phantom representing an adult male (ATOM Max 711-HN, Norfolk, VA, USA) was scanned using the 3D Accuitomo 170 CBCT (J. Morita, Kyoto, Japan) using 11 FOVs. During each scan, half of the X-ray beam was blocked. Each scan was performed at three exposure settings with varying beam energy and equal radiation dose: 90 kV 5 mA, 77 kV 7.5 mA and 69 kV 10 mA. The SPR was estimated by measuring the grey values in the blocked and non-blocked regions of the RAW data. The effect of FOV on SPR was evaluated using Dunn’s multiple comparison test, and the effect of the exposure settings was compared using a Wilcoxon signed rank test. Results: Larger FOVs showed increased scatter. FOVs with a shorter isocenter-detector distance showed a particularly high SPR. Most intercomparisons between FOVs were statistically significant. The largest difference was found between 17 × 12 cm and 6 × 6 cm (lower jaw), with the former showing a 4.9-fold higher SPR. The effect of beam energy was relatively small and varied between FOV sizes and positions. Conclusion: While the choice of FOV size and position is determined by the diagnostic region of interest, the image quality deterioration for large FOVs due to scatter provides another incentive to limit the FOV size as much as possible.

Mid-UV Spectral Diagnostics

The mid-ultraviolet is an important diagnostic region due to its sensitivity to the hottest stars of a stellar population. Sources of mid-UV flux include main sequence turn-off stars, the basic clocks of stellar evolution, and also blue horizontal branch stars and blue stragglers. We describe some observed trends in mid-UV colors and spectral indices.

SDS-PAGE identification of raw and cooked clams of the Veneridae family

Clam species belonging to the family Veneridae (Mollusca: Bivalvia) represent very important marine products, especially in the European countries. The increasing economic interest in marine edible molluscs has strongly enhanced the need for a routine method of unambiguous recognition of species in fresh and preserved material, mainly intended to prevent mislabelling and commercial frauds. Here a procedure for identification of soft parts is proposed, by means of SDS-PAGE total protein patterning. In fresh material, this technique allowed recognition of four main regions of diagnostic bands, which have been named V1 (111–99 kDa), V2 (44 kDa), V3 (33–30 kDa) and V4 (19–13 kDa). The main diagnostic region appears to be the V3 band series. SDS-PAGE analysis allows the same technique to be used with denatured samples, such as cooked and preserved soft parts, giving reproducible results, very similar to those of fresh material.

Below the Lyman Edge: UV Polarimetry of Quasars

The Lyman edge at 912Å is an important diagnostic region for studying quasi-stellar objects (QSOs). In particular, it reveals a great deal about the physical conditions within the atmospheres of accretion disks, a ubiquitous component of QSO theories. Observations of the Lyman edge regions of QSOs have shown scant evidence for the predicted features – few QSOs show the broad, partial Lyman edges expected to be common according to most theories. The FOS in its polarimetry mode has been instrumental in studying the Lyman edge region in QSOs. One of the most exciting discoveries is that the polarization rises, not at wavelengths longward of the Lyman edge, but at wavelengths well below it! Here we present the status of polarimetry observations at the Lyman edge and discuss their implications to accretions disks