this study was a part of national project to establish and optimize local and national diagnostic guidance levels. this work intends to evaluate image quality and entrance surface air kerma (esak) for patients' radiographic examinations in two north western provinces of country. two hospitals got involved in the present study. the rate of the rejected images and image quality grades were determ...

background: in diagnostic radiology there are two reasons for measuring or estimating radiation doses to patients. firstly measurements provide a means for setting and checking standards of good practice as an aid to the optimization of patient protection. secondly estimates of the absorbed dose to tissue and organs in the patients. materials and methods: a total of 2382 patients were studied t...

We show that comparing geometrical algorithms, in general, is very hard to do in a fair way. Our focus here is on the existing ray-triangle intersection test routines. A set of rules are developed so that a fair comparison can be produced, and this is all implemented in an evaluation framework. If all algorithms are evaluated using different hit rates, on different machines, for different input...

We report results of the study of soft-x-ray amplification in a discharge-created plasma under an externally applied axial magnetic field. This technique is observed to improve the uniformity and divergence of the beam of a 46.9-nm discharge-pumped Ne-like Ar soft-x-ray amplifier by decreasing the plasma density gradients at the time of lasing. At the optimum strength of 0.15 T, the magnetic fi...

Phase-matched harmonic conversion of visible laser light into soft x-rays was demonstrated. The recently developed technique of guided-wave frequency conversion was used to upshift light from 800 nanometers to the range from 17 to 32 nanometers. This process increased the coherent x-ray output by factors of 10(2) to 10(3) compared to the non-phase-matched case. This source uses a small-scale (s...

We report on what are believed to be the first full-scale images obtained with the coded aperture concept, which uses conventional x-ray sources without the need to collimate/aperture their output. We discuss the differences in the underpinning physical principles with respect to other methods, and explain why these might lead to a more efficient use of the source. In particular, we discuss how...

The current state of the art in graphics rendering algorithms and hardware is surveyed, and it is shown that ray-tracing, despite larger computational requirements than conventional algorithms, is more amenable to massive parallelism. The TigerSHARK ray-tracing architecture is then presented as an extremely cost-effective means to exploit this fundamental parallelism. A competing approach is an...

Among other possible nonlinear optical effects in the x-ray domain, x-ray stimulated electronic Raman scattering (SERS) has a special significance since it provides an opportunity to attain coherent radiation with new frequencies by using (initially) neutral atoms instead of preionized p1asmas.i In this letter we present our first results on the SERS feasibility in nonionized gases.’ Any realis...

The RCSB Protein Data Bank (PDB) has a number of options for deposition of structural data and has developed software tools to facilitate the process. In addition to ADIT and the PDB Validation Suite, a new software application, pdb_extract, has been designed to promote automatic data deposition of structures solved by X-ray diffraction. The pdb_extract software can extract information about da...

We demonstrate the generation of a coherent water window x ray by extending the plateau region of high-order harmonics under a neutral-medium condition. The maximum harmonic photon energies attained are 300 and 450 eV in Ne and He, respectively. Our proposed generation scheme, combining a 1.6 microm laser driver and a neutral Ne gas medium, is efficient and scalable in output yields of the wate...