Background Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography （CT） examination.This results from the concerns about radiation exposure from CT and t...Background Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography （CT） examination.This results from the concerns about radiation exposure from CT and the potential increase in the incidence of radiation induced carcinogenesis.This study aimed to investigate the lowest radiation dose for maintaining good image quality in adult chest scanning using GE CT equipment.Methods Seventy-two adult patients were examined by Gemstone Spectral CT.They were randomly divided into six groups.We set up a different value of noise index （NI） when evaluating each group every other number from 13.0 to 23.0.The original images were acquired with a slice of 5 mm thickness.For each group,several image series were reconstructed using different levels of adaptive statistical iterative reconstruction （ASIR） （30％,50％,and 70％）.We got a total of 18 image sequences of different combinations of NI and ASIR percentage.On one hand,quantitative indicators,such as CT value and standard deviation （SD）,were assessed at the region of interest.The signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） were calculated.The volume CT dose index （CTDI） and dose length product （DLP） were recorded.On the other hand,two radiologists with ＞5 years of experience blindly reviewed the subjective image quality using the standards we had previously set.Results The different combinations of noise index and ASIR were assessed.There was no significant difference in CT values among the 18 image sequences.The SD value was reduced with the noise index＇s reduction or ASIR＇s increase.There was a trend towards gradually lower SNR and CNR with an NI increase.The CTDI and DLP were diminishing as the NI increased.The scores from subjective image quality evaluation were reduced in all groups as the ASIR increased.Conclusions Increasing NI can reduce radiation dose.With the premise of maintaining the same image quality,using a suitable percentage of ASIR can inc展开更多
为探究不同级别噪声对矿工生理指标及行为能力影响的差异性,研究噪声引起的矿工生理指标的变化对行为能力的影响,构建了矿工生理指标与行为能力测量系统,同步采集45、65、85、95 d B等4个级别噪声影响下被试者呼吸频率、心率、皮电值等...为探究不同级别噪声对矿工生理指标及行为能力影响的差异性,研究噪声引起的矿工生理指标的变化对行为能力的影响,构建了矿工生理指标与行为能力测量系统,同步采集45、65、85、95 d B等4个级别噪声影响下被试者呼吸频率、心率、皮电值等生理指标,以及反应时间、出错次数等空间行为能力指标,运用SPSS20. 0对试验结果进行显著性检验,并运用AMOS8. 0构建结构方程模型。试验结果表明,85 d B及95 dB强噪声环境下矿工的行为能力显著低于低噪声环境下的行为能力;由45 d B升高到65 dB,噪声的升高并未对被试者的错误反应时间和呼吸频率产生显著的影响,但对反应时间、错误次数、心率和皮电值等指标产生了显著的影响;噪声引起的矿工生理指标的变化对行为能力的影响权重大小顺序依次为皮电值、呼吸频率、心率。展开更多
文摘Background Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography （CT） examination.This results from the concerns about radiation exposure from CT and the potential increase in the incidence of radiation induced carcinogenesis.This study aimed to investigate the lowest radiation dose for maintaining good image quality in adult chest scanning using GE CT equipment.Methods Seventy-two adult patients were examined by Gemstone Spectral CT.They were randomly divided into six groups.We set up a different value of noise index （NI） when evaluating each group every other number from 13.0 to 23.0.The original images were acquired with a slice of 5 mm thickness.For each group,several image series were reconstructed using different levels of adaptive statistical iterative reconstruction （ASIR） （30％,50％,and 70％）.We got a total of 18 image sequences of different combinations of NI and ASIR percentage.On one hand,quantitative indicators,such as CT value and standard deviation （SD）,were assessed at the region of interest.The signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） were calculated.The volume CT dose index （CTDI） and dose length product （DLP） were recorded.On the other hand,two radiologists with ＞5 years of experience blindly reviewed the subjective image quality using the standards we had previously set.Results The different combinations of noise index and ASIR were assessed.There was no significant difference in CT values among the 18 image sequences.The SD value was reduced with the noise index＇s reduction or ASIR＇s increase.There was a trend towards gradually lower SNR and CNR with an NI increase.The CTDI and DLP were diminishing as the NI increased.The scores from subjective image quality evaluation were reduced in all groups as the ASIR increased.Conclusions Increasing NI can reduce radiation dose.With the premise of maintaining the same image quality,using a suitable percentage of ASIR can inc
文摘为探究不同级别噪声对矿工生理指标及行为能力影响的差异性,研究噪声引起的矿工生理指标的变化对行为能力的影响,构建了矿工生理指标与行为能力测量系统,同步采集45、65、85、95 d B等4个级别噪声影响下被试者呼吸频率、心率、皮电值等生理指标,以及反应时间、出错次数等空间行为能力指标,运用SPSS20. 0对试验结果进行显著性检验,并运用AMOS8. 0构建结构方程模型。试验结果表明,85 d B及95 dB强噪声环境下矿工的行为能力显著低于低噪声环境下的行为能力;由45 d B升高到65 dB,噪声的升高并未对被试者的错误反应时间和呼吸频率产生显著的影响,但对反应时间、错误次数、心率和皮电值等指标产生了显著的影响;噪声引起的矿工生理指标的变化对行为能力的影响权重大小顺序依次为皮电值、呼吸频率、心率。
