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The purpose of this work is to investigate the factors determining the magnitude and nature of the lag effect (residual signal) in the Varian PaxScan 4343CB flat-panel detector. Depending on the detector mode, typical value of residual signal is 1-2% after single exposed frame, increasing up to 3% after multiple exposures. The lag effect is the cause of up to 3.6% error of average flat-field signal measurement if used for averaging series of continuously exposed frames, which leads to incorrect assessment of X-ray attenuation coefficients. Spatial dependence of the lag effect is confirmed; the results of correction of projection images using spatially localized impulse response functions are demonstrated.

The shape and size of the projection of the focal spot of an x-ray tube largely depend on the direction of the beam, which results in a spatial difference of the point spread function (PSF) of the imaging system. A model developed for determining the PSF at an arbitrary point of the radiation field is presented in this article. The input data for the model are the geometric parameters of the system, the measured magnified projection of the effective focal spot, and the PSF in the internal structure of the detector. The difference in the width of the profiles of the PSF between the experimental and modeled data does not exceed 7.2%. The projection images are reconstructed by means of a deconvolution algorithm using the modeled PSF. The frequency–contrast characteristics of the images show improvement compared with the initial image.

In 1903, on the basis of Morozov Institute of the Moscow Imperial University (currently, P. Herzen Moscow Oncology Research Center, a branch of the National Medical Research Radiological Center, Ministry of Health of the Russian Federation), the first specialized unit in Russia was opened – department of radiation therapy of oncological diseases, in which scientific research in the field of medical radiology was officially launched in our country for the first time. The first studies in the field of radiation therapy can be attributed to this period.The article presents a brief summary of the historical development of radiotherapy in the world and in Russia; provides information on the achievements of global importance, fundamental for this scientific field. The activities of leading Russian organizations in the field of radiation therapy are reviewed; names of scientists, doctors and other specialists who have made a significant contribution to its development are provided. The main literature sources relevant to the field are given.The data in this article may be of interest and be useful for biomedical scientists, practicing radiologists and radiotherapists, oncologists, medical and graduate students, interns and other specialists.

A system currently under development for remote radiotherapy based on a 6 MeV linac and cone-beam computer tomograph is presented. Its distinguishing design features and solutions are described: compact 5-cm wavelength electron accelerator, solid-state modulator, visualization in the bremsstrahlung beam with low nominal energy 2.5 MeV, bremsstrahlung beam without a compensating filter, cone-beam computer tomography, multi-leaf collimator, adaptive radiotherapy, and a therapeutic table with six degrees of freedom. The system is compared with foreign analogs.

Data on the radiation loads of a radiotherapy system developed at NIITFA are presented. The main problems of the calculations are to establish the region in the mobile part of the system that is best suited for arrangement of blocks with electronics and to calculate the parameters of local radiation shielding that ensures fault-free operation of the electronics for the life of the system. The calculations were performed by the Monte Carlo method using the FLUKA software package.

Article describes the new type of multiphase flowmeter – “Ural-MR” developed by Corporation Uraltechnostroy LLC. Its operation is based on single physical principle: all flow parameters are evaluated with X-ray radiation analysis. Currently last steps of certification procedure are held, mass production procedure is been worked out. Design of the flowmeter, basic operation principles and demonstrative results are presented in the article.

Main parameters of digital flat panel detectors, to be taken into account in developing imaging systems are considered. Various factors affecting obtained images are presented. Experimental results presented confirm the necessity of image correction.

The online version of the original article can be found at https://doi.org/10.1007/s10512-019-00490-9

In Fig. 5 on page 341, the units for the X and Z axes should read cm. In Fig. 6 on page 341, the units for the X and Y axes should read cm.

Development of air-breathing pulse detonation engines is faced with a challenging problem of detonation initiation in fuel sprays at distances feasible for propulsion applications. Extensive experimental study on initiation of a confined n-hexane spray detonation in air by electric dis- charges is reported. It is found that for direct initiation of spray detonation with minimal energy requirements (1) it is worth to use one discharger located near the closed end of a detonation tube and at least one additional discharger down- stream from it to be triggered in-phase with primary shock wave arrival; (2) the discharge area should be properly insu- lated to avoid electric loss to metal tube walls; (3) discharge duration should be minimized to at least 50 µs; (4) discharge channel should preferably occupy a large portion of a tube cross-section; (5) test tube should be preferably of a diame- ter close to the limiting tube diameter; (6) gradual transition between the volume with electric discharger and the tube should be used; and (7) a powerful electric discharger uti- lized for generating a primary shock wave can be replaced by a primary shock wave generator comprising a relatively low-energy electric discharger, Shchelkin spiral, and tube coil. With all these principles implemented, the rated elec- tric energy of about 100 J was required to initiate n-hexane spray-air detonation in a 28-mm tube at a distance of about 1 m from the atomizer.

Experimental studies of single-pulse and multipulse confined detonations of liquid n-hexane spray in air initiated by successively triggered electric dischargers are presented. Similarly to a single-pulse mode, the multipulse operation mode shows the resonant dependence of the detonation initiation energy on the time delay between triggering the dischargers. There is a potential for considerable decrease in the detonation initiation energy with decreasing tube diameter and mounting of a turbulizing spiral between the dischargers. The technique is considered promising for pulse-detonation engine applications. Nomenclature C1, C2 = capacitances of the main discharge of the dischargers D1 and D2 E = discharge energy Ecr = critical energy of detonation initiation E p = energy of the primary (initiating) discharge J1, J2 = discharge currents for the dischargers D1 and D2 t1, t2, t3 = shock wave arrival times at pressure transducers PT1, PT2, and PT3, respectively U = discharge voltage Ui