New Algorithm for Upgrading of Portal Radiation Monitors with Plastic Detectors. Part 3. Description of the Algorithm

New algorithm is described in the third part of the paper. It uses method of energy windows and is based on iterative scheme. Values of smoothing and thresholds are optimized in each energy window and time step during of movement of transport through control zone. Some parameters of monitor which are measured on the place of its installation or manufacturing are used as input information.

Impacts of acquisition and reconstruction parameters on the absolute technetium quantification of the cadmium–zinc–telluride-based SPECT/CT system: a phantom study

Background The digital cadmium–zinc–telluride (CZT)-based SPECT system has many advantages, including better spatial and energy resolution. However, the impacts of different acquisition and reconstruction parameters on CZT SPECT quantification might still need to be validated. This study aimed to evaluate the impacts of acquisition parameters (the main energy window and acquisition time per frame) and reconstruction parameters (the number of iterations, subsets in iterative reconstruction, post-filter, and image correction methods) on the technetium quantification of CZT SPECT/CT. Methods A phantom (PET NEMA/IEC image quality, USA) was filled with four target-to-background (T/B) ratios (32:1, 16:1, 8:1, and 4:1) of technetium. Mean uptake values (the calculated mean concentrations for spheres) were measured to evaluate the recovery coefficient (RC) changes under different acquisition and reconstruction parameters. The corresponding standard deviations of mean uptake values were also measured to evaluate the quantification error. Image quality was evaluated using the National Electrical Manufacturers Association (NEMA) NU 2–2012 standard. Results For all T/B ratios, significant correlations were found between iterations and RCs (r = 0.62–0.96 for 1–35 iterations, r = 0.94–0.99 for 35–90 iterations) as well as between the full width at half maximum (FWHM) of the Gaussian filter and RCs (r = − 0.86 to − 1.00, all P values < 0.05). The regression coefficients of 1–35 iterations were higher than those of 35–90 iterations (0.51–1.60 vs. 0.02–0.19). RCs calculated with AC (attenuation correction) + SC (scatter correction) + RR (resolution recovery correction) combination were more accurate (53.82–106.70%) than those calculated with other combinations (all P values < 0.05). No significant statistical differences (all P values > 0.05) were found between the 15% and 20% energy windows except for the 32:1 T/B ratio (P value = 0.023) or between the 10 s/frame and 120 s/frame acquisition times except for the 4:1 T/B ratio (P value = 0.015) in terms of RCs. Conclusions CZT-SPECT/CT of technetium resulted in good quantification accuracy. The favourable acquisition parameters might be a 15% energy window and 40 s/frame of acquisition time. The favourable reconstruction parameters might be 35 iterations, 20 subsets, the AC + SC + RR correction combination, and no filter.

Crystalline chirality and interlocked double hourglass Weyl fermion in polyhedra-intercalated transition metal dichalcogenides

Introducing crystalline chirality into transition metal dichalcogenides (TMDs) has attracted much attention due to its modulation effect on optical properties and the potential to reveal new forms of electronic states. Here, we predict a number of chiral materials by intercalating polyhedra into TMD lattices, finding a type of double hourglass Weyl fermion interlocked with crystalline chirality. The best candidate RhV3S6 (P6322) possesses the largest hourglass energy window of ~380 meV, as well as strong optical circular dichroism (CD) in the infrared regime, both of which are tunable by external strains. The chirality is originally induced by the configuration of intercalated polyhedra and then reduced by the rotational atomic displacements triggered by intercalation, as indicated by CD calculations. Our study opens the way of designing chiral materials with spin-split double hourglass Weyl fermions via structural unit intercalation in achiral crystals for future chiral-functionalized optoelectronic and spintronic devices.

ÁP DỤNG PHƯƠNG PHÁP FSA ĐỂ PHÂN TÍCH PHÓNG XẠ MÔI TRƯỜNG CHO MẪU HÌNH HỌC MARINELLI

Trong bài báo này, chúng tôi áp dụng phương pháp FSA (Full Spectrum Analysis) vào phân tích xác định hoạt độ các đồng vị phóng xạ tự nhiên 226Ra, 232Th, 40K trong các mẫu đất hình học Marinelli bằng hệ phổ kế gamma phòng thí nghiệm. Mẫu chuẩn IAEA-SL-2, KL-01 được sử dụng làm mẫu phân tích để kiểm tra độ tin cậy của phương pháp FSA. Kết quả phân tích các mẫu đất bằng phương pháp FSA được so sánh với EWA (Energy Window Analysis). Từ đó, chúng tôi đánh giá những ưu điểm của phương pháp FSA so với phương pháp phân tích truyền thống EWA.

Impacts of Acquisition and Reconstruction Parameters on the Absolute Technetium Quantification of the Cadmium-zinc-telluride Based SPECT/CT System: A Phantom Study

BackgroundVarious acquisition and reconstruction parameters may affect the accuracy of the absolute SPECT quantification. However, many of the impacts of these parameters have not well been studied. This study aimed to evaluate the impacts of acquisition parameters (main energy window and acquisition time per frame) and reconstruction parameters (the number of iterations and subsets in iterative reconstruction, post-filter, and image correction methods) on the technetium quantification of the cadmium-zinc-telluride based SPECT/CT system. MethodsA phantom (PET NEMA/IEC image quality, USA) was filled with a 16:1 sphere-to-background activity concentration ratio of technetium and all spheres had 132400.81Bq/ml of radioactivity. Mean uptake values (calculated mean concentrations for spheres) were measured to evaluate the recovery coefficient (RC) changes under different acquisition and reconstruction parameters. Corresponding standard deviations of mean uptake values were also measured to evaluate the quantification error. Image quality was evaluated using the National Electrical Manufacturers Association (NEMA) NU 2-2012 standard.ResultsFor six spheres of the phantom, significant correlations were found between iterations and RCs (r=0.60~0.98 for 1~35 iterations, r=0.96~0.99 for 35~90 iterations, all P-values <0.05) as well as between the full width at half maximum (FWHM) of the Gauss filter and RCs (r=-0.90～-1.00, all P-values <0.05). 1~35 iterations had higher regression coefficients compared with those of 35~90 iterations (0.67~1.16 vs. 0.02~0.17). The AC (attenuation correction)+SC (scatter correction) +RR (resolution recovery correction) combination had more close to 100% RCs (42.42%~98.04%) with better image quality (31.52%~83.57%) than those of other correction combinations (all P-values <0.05). No significant statistical difference was found between the 15% energy window and the 20% energy window (P-value=0.061), nor between the 5 seconds/frame and 120 seconds/frame of acquisition time (P-value=0.943) in terms of RCs. ConclusionsThe CZT-SPECT/CT showed a good quantification accuracy of technetium. The favorable acquisition parameters may be 15% energy window and 40 seconds/frame of acquisition time. The favorable reconstruction parameters could be 35 iterations, 20 subsets, the AC+SC+RR correction combination, and FWHM 0.7mm of Gauss filter.