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Objective:To study the impact of different scattering correction algorithms in the reconstruction of PET/CT images on image artifacts and the precision of quantitative parameters.Methods:The phantom as described in the National Electrical Manufacturers Association (NEMA) NU2 standard was filled with 18F. The background activity was fixed, and the activity of the solution in the spheres was adjusted to obtain several configurations, including the normal ratio group (4.08∶1) and the extreme ratio group (200∶1). The surface contamination group with the same ratio as the extreme ratio group contained a small radioactive source with different doses of 18F (74, 37, 3.7 and 0.37 MBq) placed at the surface of the phantom. PET/CT images of 30 patients (21 males, 9 females, age: (44.5±10.2) years) from Peking University Cancer Hospital & Institute between July 2012 and December 2021 were retrospectively analyzed, including 10 with normal images ( 18F-FDG) and 20 with abnormal images (10 with dislocation during acquisition, 10 with surface contamination). The images were reconstructed with relative and absolute scattering correction. The phantom was evaluated using the target to background ratio (TBR) and the artifact classification. CV as well as the artifact classification were used to compare the clinical image quality. Mann-Whitney U test and χ2 test were used to analyze data. Results:In the normal ratio group and the extreme ratio group, the TBRs of phantom images reconstructed with relative correction were significantly higher than those with absolute correction (normal ratio group: 3.30(1.94, 4.53) vs 2.72(1.56, 3.56); z=-2.20, P=0.028; extreme ratio group: 105.47(45.62, 162.82) vs 101.36(43.96, 155.57); z=-1.99, P=0.046). In the surface contamination group, with the increase of the activity of the small source, the artifact became more obvious, and the artifact classification score of absolute correction was significantly better than that of relative correction (1.5(1.0, 2.0) vs 2.5(2.0, 3.0); z=-2.00, P=0.046). In the 10 normal 18F-FDG PET/CT patients, the CVliver of the relative correction (9.67%(8.00%, 11.00%)) was significantly lower than that of absolute correction (11.00%(9.00%, 12.00%); z=-2.57, P=0.010), indicating the higher image quality of images with relative correction. In abnormal images, the image quality of absolute correction was significantly higher than that of relative correction with fewer and less severe artifacts (dislocation cases: 9/10 vs 4/10; χ2=5.50, P=0.019; surface contamination cases: 9/10 vs 4/10; χ2=5.50, P=0.019). Conclusions:The relative scattering correction is suitable for normal situations in clinical PET acquisition. However, with dislocation or surface contamination, the absolute scattering correction helps to reduce the artifacts and improve the image quality.
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RESUMO O potencial risco de exposição das populações aos agentes Químicos, Biológicos, Radioativos e Nucleares (QBRN), seja por causas intencionais ou não, configura-se como questão de segurança nacional e demanda um constante aprimoramento do seu gerenciamento. Os modelos de dispersão atmosférica vêm ganhando destaque como ferramenta de apoio à gestão dos riscos aos agentes QBRN. O objetivo desta pesquisa foi identificar e avaliar estudos que utilizaram o modelo Hysplit no contexto de eventos QBRN. Para tanto, foi realizada uma revisão integrativa de literatura de artigos publicados entre 2014 e 2018, nas bases de dados PubMed, Scopus, Web of Science e Lilacs. A análise dos artigos selecionados permitiu verificar o potencial do uso do modelo Hysplit, enquanto modelo matemático, para compreender o transporte, a dispersão e a deposição de ameaças QBRN liberadas na atmosfera. Os dados produzidos pelas simulações geradas por esse código podem revelar quais áreas serão potencialmente impactadas em um determinado evento ou a região de origem de elementos dispersos no ar. Ademais, o Hysplit pode ser agregado como uma ferramenta de suporte às decisões perante as distintas fases da gestão de eventos QBRN.
ABSTRACT The potential risk of exposure of populations to Chemical, Biological, Radioactive and Nuclear agents (CBRN), either by intentional causes or not, is a matter of national security and demands a constant improvement in its management. The models of atmospheric dispersion have been gaining prominence as a tool to support the management of risks to CBRN agents. The objective of this research was to identify and evaluate studies that used the Hysplit model in the context of CBRN events. For this purpose, an integrative literature review of published articles was conducted between 2014 and 2018, from the PubMed, Scopus, Web of Science and Lilacs databases. The analysis of the selected articles revealed the potential of the Hysplit model, as a mathematical model, to understand the transport, dispersion and deposition of CBRN threats released into the atmosphere. The data produced by the simulations generated by this code can reveal which areas will be potentially impacted in a given event or the region of origin of elements dispersed in the air. In addition, Hysplit can be aggregated as a decisions support tool in the different phases of CBRN event management.
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Abstract Objective: To measure the scattered radiation dose at different positions simulating hip surgery. Materials and Methods: We simulated fluoroscopy-assisted hip surgery in order to study the distribution of scattered radiation in the operating room. To simulate the patient, we used a anthropomorphic whole-body phantom, and we used an X-ray-specific detector to quantify the radiation. Radiographs were obtained with a mobile C-arm X-ray system in continuous scan mode, with the tube at 0º (configuration 1) or 90º (configuration 2). The operating parameters employed (voltage, current, and exposure time) were determined by a statistical analysis based on the observation of orthopedic surgical procedures involving the hip. Results: For all measurements, higher exposures were observed in configuration 2. In the measurements obtained as a function of height, the maximum dose rates observed were 1.167 (± 0.023) µSv/s and 2.278 (± 0.023) µSv/s in configurations 1 and 2, respectively, corresponding to the chest level of health care professionals within the operating room. Proximal to the patient, the maximum values were recorded in the position occupied by the surgeon. Conclusion: We can conclude that, in the scenario under study, health care professionals workers are exposed to low levels of radiation, and that those levels can be reduced through the use of personal protective equipment.
Resumo Objetivo: Medir a intensidade da dose de radiação espalhada em diferentes posições simulando uma intervenção cirúrgica no quadril. Materiais e Métodos: Simulou-se uma intervenção cirúrgica no quadril com apoio da fluoroscopia para estudar a distribuição da radiação espalhada no bloco operatório. Para simular o paciente foi utilizado um simulador antropomórfico de corpo inteiro e para medir a radiação utilizou-se um detector específico para medir raios X. Realizaram-se incidências com um equipamento de raios X tipo arco em C móvel, em modo de escopia contínua, com a ampola a 0º (configuração 1) e a 90º (configuração 2). Os parâmetros operacionais utilizados (voltagem, corrente, tempo de exposição) foram determinados por meio de um estudo estatístico resultante da observação de cirurgias ortopédicas de quadril. Resultados: Em todas as medições observaram-se exposições mais elevadas na configuração 2. Nas medições em função da altura, observaram-se os valores máximos da taxa de dose de 1,167 (± 0,023) µSv/s e 2,278 (± 0,023) µSv/s nas configurações 1 e 2, respectivamente, correspondendo à altura do tórax dos profissionais. No estudo em torno do paciente os valores máximos registraramse na posição ocupada pelo médico cirurgião. Conclusão: Concluiu-se que a exposição à radiação dos profissionais é baixa, podendo ainda ser reduzida mediante o uso de equipamentos de proteção individual.
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Background Phacoemulsification with IOL implantation can reduce the light scattering caused by cataract,but many patients with IOLs implantation complained of glare or blurred vision.IOLs from different materials will affect IOL refractive index (RI) and optical design,which affect the value of scattered light of IOLs implantation.Objective This study was to analyze the effect of IOL materials on optical quality in pseudophakic eyes with optical quality analysis system (OQAS).Methods The clinical data of 95 eyes from 65 patients with age-related cataract who received phacoemulcification with IOL implantation in Tianjin Eye Hospital from March to Octomber were retropectively analyzed.Three types of lOL,including AR40e,Acrysof SA60 AT and Rayner 620H,were implanted in 32 eyes,30 eyes and 33 eyes,respectively.The visual quality indexes were detected and evaluated using OQAS,including uncorrected distance visual acuity (UCDVA,LogMAR),objective scatter index (OSI),modulation transfer function cut off (MTF cut off),strehl ratio (SR),Profile width at 50％ point scatter function (PSF),Profile width at 10％ PSF and contrast visual acuity under the 100％,20％,9％ contrasts.Results The UCDVA was ≥ 0.3 in the eyes of AR40e group,SA60AT group and 620H group 1 month after surgery.No significant difference was found in the best corrected distance visual acuity (BCDVA,LogMAR) among three groups (F =1.362,P =0.246).The OSI was 1.72±1.11,1.89±1.07 and 2.13±1.13 in the AR40e group,SA60AT group and 620H group,with a significant difference among the groups (F =3.638,P =0.045),and the OSI was significantly lower in the AR40e group than that in the SA60AT group or 620H group (both at P＜0.05).No considerable difference in MTF cut off among the groups (F =2.401,P =0.192).The SR value was significantly elevated and the PSF at both 50％ and 10％ was declined in the AR40e group compared with the SA60AT group and 620H group (all at P＜0.05).A significant difference was found in 9％ contrast visual acuity among the three groups (F=3.866,P=0.038),and 9％ contrast visual acuity was better in the AR40e group than that in the SA60At group or the 620H group (both at P＜ 0.05).Negative correlations were found betwee OSI and BCDVA in the AR40e group,SA60AT group and 620H group (r=-0.275,P=0.041;r=-0.287,P=0.042;r=-0.233,P=0.037).Conclusions OQAS can evaluate optical quality of cataract patients after opeartion objectively.Material and RI of IOL have a great effect on visual quality after phacoemulcification with IOL implantation,especially under the low contrast environment.The operated eyes implanted hydrophobic acrylic IOLs with a lower RI can get better optical quality in comparison with the eyes implanted hydrophilic IOLs.
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Objective To study the radiation dose level and dose distribution of leakage and scattering radiation in a helical tomotherapy (TOMO) room,and to identify the dose distribution characteristic which is different from the conventional radiotherapy so as to provide scientific data for the radiation protection of TOMO.Methods A helical tomotherapy facility typed Tomotherapy Hi-Art was employed as the radiotherapy device.The air kerma from leakage radiation and scattering radiation distributed on the couch plane and in TOMO room were detected mainly by GR-200A TLDs of LiF(Mg,Cu,P),while 100 Gy were being accumulated under the condition of simulation radiation treatment.Then,the leakage radiation ratio and scattering-leakage radiation ratio (the ratio of site radiation dose to isocenter standard output dose) were calculated.Results The radiation level and dose distribution of leakage radiation and scattering radiation in the TOMO treatment room were in bilateral symmetry to the rotation isocenter and the treatment couch longitudinal axis,and the radiation level in front of the radiotherapy device was significantly higher than that of the rear of the TOMO equipment.In the plane of treatment couch,the maximum leakage radiation ratio at the position 100 cm away from the isocenter was only 1.3 × 10-4,and the mean value of the leakage radiation ratio at the position 300 cm away from the isocenter was lower than 2.0 × 10-5.The scattering radiation at 200-300 cm away from the isocenter was accounted for 25％-30％ of the leakage radiation from the responding sites,and the indoor scattering radiation decreased faster than leakage radiation with the distance from the isocenter.Conclusions The radiation level of leakage and scattering in a TOMO room is significantly lower than that in a conventional radiotherapy room.