Conspicuity of malignant pleural mesothelioma in contrast enhanced MDCT – arterial phase or late phase?

Background To determine if late phase is superior to arterial phase intraindividually regarding conspicuity of MPM in contrast enhanced chest MDCT. Methods 28 patients with MPM were included in this retrospective study. For all patients, chest CT in standard arterial phase (scan delay ca. 35 s) and abdominal CT in portal venous phase (scan delay ca. 70 s) was performed. First, subjective analysis of tumor conspicuity was done independently by two radiologists. Second, objective analysis was done by measuring Hounsfield units (HU) in tumor lesions and in the surrounding tissue in identical locations in both phases. Differences of absolute HUs in tumor lesions between phases and differences of contrast (HU in lesion – HU in surrounding tissue) between phases were determined. HU measurements were compared using paired t-test for related samples. Potential confounding effects by different technical and epidemiological parameters between phases were evaluated performing a multiple regression analysis. Results Subjective analysis: In all 28 patients and for both readers conspicuity of MPM was better on late phase compared to arterial phase. Objective analysis: MPM showed a significantly higher absolute HU in late phase (75.4 vs 56.7 HU, p < 0.001). Contrast to surrounding tissue was also significantly higher in late phase (difference of contrast between phases 18.5 HU, SD 10.6 HU, p < 0.001). Multiple regression analysis revealed contrast phase and tube voltage to be the only significant independent predictors for tumor contrast. Conclusions In contrast enhanced chest-MDCT for MPM late phase scanning seems to provide better conspicuity and higher contrast to surrounding tissue compared to standard arterial phase scans.

Conspicuity of Malignant Pleural Mesothelioma in Contrast Enhanced MDCT – Arterial Phase or Late Phase?

Background: To compare two different contrast phases intraindividually regarding conspicuity of MPM in chest MDCT. Methods: 28 patients with MPM were included in this retrospective study. For all patients, chest CT in standard arterial phase and abdominal CT in portal venous phase (scan delay ca. 70 s) was performed. First, subjective analysis of tumor conspicuity was done independently by two radiologists. Second, objective analysis was done by measuring Hounsfield units (HU) in tumor lesions and in the surrounding tissue in identical locations in both phases. Differences of absolute HUs in tumor lesions between phases and differences of contrast (HU in lesion – HU in surrounding tissue) between phases were determined. HU measurements were compared using paired t-test for related samples. Potential confounding effects by different technical and epidemiological parameters between phases were evaluated performing a multiple regression analysis.Results: Subjective analysis: In all 28 patients and for both readers conspicuity of MPM was better on late phase compared to arterial phase. Objective analysis: MPM showed a significantly higher absolute HU in late phase (75.4 vs 56.7 HU, p < 0.001). Contrast to surrounding tissue was also significantly higher in late phase (difference of contrast between phases 18.5 HU, SD 10.6 HU, p < 0.001). Multiple regression analysis revealed contrast phase and tube voltage to be the only significant independent predictors for tumor contrast.Conclusions: In contrast enhanced chest-MDCT for MPM late phase scanning seems to provide better conspicuity and higher contrast to surrounding tissue compared to standard arterial phase scans.

Planar slotted ridged waveguide antenna arrays with dielectric layer

The paper simulates the options available to move operating range of slotted waveguide antennas downward in frequency without changing the waveguide cross-section, and suggests the ways for designing linear waveguide-slotted elements based on rectangular and ridge waveguides with air and partial dielectric filling. The critical frequency of the fundamental mode of a 16x8 mm rectangular waveguide moves by ridging from 9.5 to 6.5 GHz. Partial dielectric filling of the cavity of the ridge waveguide makes it possible to additionally shift the operating range downward in frequency by 6-10% without making changes to antenna design. The antenna characteristics of linear arrays based on a dielectric-filled ridge slotted waveguide have been compared in terms of gain and voltage standing wave ratio to similar designs of arrays on rectangular and air-filled analogues. Based on the obtained structures of linear elements, simulation models of planar arrays have been constructed so that they have the similar area of total surface. Simulated frequency dependence of the realized gain for planar arrays has demonstrated a shift of the operating range downward in frequency. The analysis of the directivity characteristics of planar arrays for various phase shifts between the linear elements has been carried out. The simulation results have shown that the use of a dielectric-filled ridge waveguide gives an advantage in phase scan angle of the main beam of the radiation pattern. With the same phase shift, in planar arrays of dielectric-filled ridge waveguides, the main beam scans for a larger angle while keeping side lobes at low level. Thus, the use of a ridge slotted waveguide with a dielectric layer inside makes it possible to expand the phase scan angle.

ULTRA-WIDEBAND SCANNING ANTENNA ARRAY WIRE EMITTERS

The aim of the work is to determine the properties of the ultra-wideband scanning antenna array of wire emitters. A single element of the grid is a three-dimensional antenna Vivaldi. Numerical simulation of antenna arrays and single Vivaldi emitters was carried out by the method of integral equations in the thin-wire approximation using the original program and the MMANA program. The dimensions of all elements of a single emitter are determined by the criterion of matching and the shape of the radiation pattern for operation in the frequency range 2–18 GHz. The described variant of the antenna according to the matching criterion (SWR < 2) has a frequency overlap coefficient of 12. The narrowing of the frequency band of a single emitter in the composition of non-scanning and scanning gratings within the angle of 30 degrees is determined. The article deals with the range properties of antenna arrays depending on the parameters of the emitters and the possibility of phase scanning. It is shown that the greatest frequency band in agreement has a lattice with a minimum step of placement of emitters. In a flat antenna array, when scanning in the H-plane, the frequency band according to the matching criterion decreases by 2–3 times. It is shown that the linear lattice without scanning has a frequency overlap coefficient equal to 6 according to the criterion of matching emitters. This ratio decreases as the phase scan sector increases. In a flat lattice, the frequency overlap coefficient and the phase scan sector are smaller than in a linear lattice and decrease with the number of rows. The reduced antenna array has a number of design advantages and can be used in systems with ultra-wideband signals.

Synthesis-Controlled Polymorphism, Magnetic and Electrochemical Properties of Li3Co2SbO6

<div>Li3Co2SbO6 is found to adopt two highly distinct structural forms: a hexagonal layered O3- LiCoO2 type phase with “honeycomb” 2:1 ordering of Co and Sb; and an orthorhombic superstructure of rock-salt type, isostructural with Li3Co2TaO6 but with the addition of significant Li/Co ordering. Pure samples of both phase scan be obtained by conventional solid-state synthesis from the same precursors, Li3SbO4 and CoO, by controlling particle size and reaction time. Both phases show relatively poor performance as lithium-ion battery cathode materials in their as-made states, but complex and interesting low-temperature magnetic properties. The honeycomb phase orders antiferromagnetically below TN = 14 K, but a positive Weiss constant θw = 18.1 K points to strong ferromagnetic interactions in the paramagnetic regime above TN; and isothermal magnetisation below TN shows evidence for a field-induced “spin-flop” transition at H ~ 0.7 T. The rock-salt type superstructure phase orders antiferromagnetically below TN = 112 K, then undergoes two more transitions at 80 K and 60, suggesting close competition between at least three ground states. Consistent with such competition, the Weiss constant θw = -181 K indicates some frustration, there is a strong field-cooled / zero field-cooled divergence below TN, and isothermal magnetisation shows it to be magnetically soft with low coercivity.<br></div>

Synthesis-Controlled Polymorphism, Magnetic and Electrochemical Properties of Li3Co2SbO6

<div>Li3Co2SbO6 is found to adopt two highly distinct structural forms: a hexagonal layered O3- LiCoO2 type phase with “honeycomb” 2:1 ordering of Co and Sb; and an orthorhombic superstructure of rock-salt type, isostructural with Li3Co2TaO6 but with the addition of significant Li/Co ordering. Pure samples of both phase scan be obtained by conventional solid-state synthesis from the same precursors, Li3SbO4 and CoO, by controlling particle size and reaction time. Both phases show relatively poor performance as lithium-ion battery cathode materials in their as-made states, but complex and interesting low-temperature magnetic properties. The honeycomb phase orders antiferromagnetically below TN = 14 K, but a positive Weiss constant θw = 18.1 K points to strong ferromagnetic interactions in the paramagnetic regime above TN; and isothermal magnetisation below TN shows evidence for a field-induced “spin-flop” transition at H ~ 0.7 T. The rock-salt type superstructure phase orders antiferromagnetically below TN = 112 K, then undergoes two more transitions at 80 K and 60, suggesting close competition between at least three ground states. Consistent with such competition, the Weiss constant θw = -181 K indicates some frustration, there is a strong field-cooled / zero field-cooled divergence below TN, and isothermal magnetisation shows it to be magnetically soft with low coercivity.<br></div>

Synthesis-Controlled Polymorphism, Magnetic and Electrochemical Properties of Li3Co2SbO6

<div>Li3Co2SbO6 is found to adopt two highly distinct structural forms: a hexagonal layered O3- LiCoO2 type phase with “honeycomb” 2:1 ordering of Co and Sb; and an orthorhombic superstructure of rock-salt type, isostructural with Li3Co2TaO6 but with the addition of significant Li/Co ordering. Pure samples of both phase scan be obtained by conventional solid-state synthesis from the same precursors, Li3SbO4 and CoO, by controlling particle size and reaction time. Both phases show relatively poor performance as lithium-ion battery cathode materials in their as-made states, but complex and interesting low-temperature magnetic properties. The honeycomb phase orders antiferromagnetically below TN = 14 K, but a positive Weiss constant θw = 18.1 K points to strong ferromagnetic interactions in the paramagnetic regime above TN; and isothermal magnetisation below TN shows evidence for a field-induced “spin-flop” transition at H ~ 0.7 T. The rock-salt type superstructure phase orders antiferromagnetically below TN = 112 K, then undergoes two more transitions at 80 K and 60, suggesting close competition between at least three ground states. Consistent with such competition, the Weiss constant θw = -181 K indicates some frustration, there is a strong field-cooled / zero field-cooled divergence below TN, and isothermal magnetisation shows it to be magnetically soft with low coercivity.<br></div>

Universality of local weak interactions and its application for interferometric alignment

The modification of the effect of interactions of a particle as a function of its preselected and postselected states is analyzed theoretically and experimentally. The universality property of this modification in the case of local interactions of a spatially preselected and postselected particle has been found. It allowed us to define an operational approach for the characterization of the presence of a quantum particle in a particular place: the way it modifies the effect of local interactions. The experiment demonstrating this universality property provides an efficient interferometric alignment method, in which the position of the beam on a single detector throughout one phase scan yields all misalignment parameters.

Automated Interpretation of Myocardial Perfusion Images with Multilayer Perceptron Network as a Decision Support System

Aim: Bull's eye pattern recognition with artificial neural networks (ANNs) has the potential to assist interpretation of myocardial perfusion images (MPIs). We aimed to develop a model for interpretation of MPI based on the clinical variables and imaging data. Materials and Methods: The study included 208 patients referred to the department of nuclear medicine for 2-day stress-rest ECG-gated MPI. Several ANN models were designed with the following input variables: average count of 20 segments of the bull's eye images of stress and rest MPIs, gender, the constellation of coronary artery disease risk factors and scintigraphic cardiac ejection fraction. The procedure was repeated excluding the data of the rest phase scan. Data of 150 subjects were used for training, 21 subjects for cross-validation and 37 subjects for final operation testing. Several ANN models were examined with different hidden layers and processing elements and functions. The target output variable was the conclusion of the nuclear physician (i.e., normal vs. abnormal scan). Results: A multilayer perceptron (MLP) with two hidden layers trained with both stress and rest data demonstrated the best performance to classify the normal and abnormal MPIs. It showed an overall accuracy of 91.9%, sensitivity of 91.3% and specificity of 92.9%. The accuracy of the similar MLP trained using stress-only myocardial perfusion images reduced to 67.6%. Conclusion: The automated interpretation of MPIs with a 2 hidden layer MLP trained with stress and rest images could be an accurate support system either for the interpretation or quality assurance.

CT-Urography: Comparison of different methods for increasing the intra-abdominal pressure

Objective: Investigating the influence of increasing the intraabdominal pressure by Valsalva maneuvers and/or abdominal compression to reach best visualization of the entire urinary tract in computed tomography urography (CTU).Methods: After split-bolus technique, Valsalva maneuvers, compression or a combination of both were applied in 60 patients before late phase images were acquired. The degree of opacification and distension of three segments of the urinary tract were evaluated.Results: After split-bolus CT no significant difference among the groups regarding distention and opacification. A significant increase in distension and opacification was found during Valsalva and the combination of Valsalva and compression.Conclusions: A CTU protocol including a late phase scan with prior application of compression, Valsalva maneuvers or a combination of both showed beneficial effects for the distension and opacification, a significant difference was found by taking location as a covariate.