Environmental assessment in an arid coal mining area requires an understanding of the influences of coal mining,the arid climate and ecological remediation.To that end,we selected vegetation as the key environmental f...Environmental assessment in an arid coal mining area requires an understanding of the influences of coal mining,the arid climate and ecological remediation.To that end,we selected vegetation as the key environmental factor to observe.Remote sensing approaches to monitoring the spatio-temporal variation of vegetation caused by mining activities,the arid climate and ecological remediation in the Shengdong coal mining area are described.Over a large regional scale it was found that the vegetation was improved as a result of ecological remediation activities.At the local scale,however,the vegetation coverage and soil moisture in the mined areas were slightly lower than those in un-mined areas due to mining subsidence.These differences are partly attributed to ground fissures that injure root systems and increase the depletion of soil moisture.It is recommended that fissures be reduced and filled to lessen their adverse effects on the environment.展开更多
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
基金国家863课题"全球森林生物量和碳储量遥感估测关键技术(编号:2012AA12A306)"亚太森林恢复与可持续管理网络项目"Forest Cover and Aboveground Biomass Mapping in the Greater Mekong Subregion and Malaysia(编号:2011PA004)"资助
基金supported by the Scientific Research Foundation of Jiangsu Key Laboratory of Resources and Environmental Information Engineering (No.JS200904)the Program of Education Ministry for Changjiang Scholars and Innovative Research Team(No.IRT0865).
文摘Environmental assessment in an arid coal mining area requires an understanding of the influences of coal mining,the arid climate and ecological remediation.To that end,we selected vegetation as the key environmental factor to observe.Remote sensing approaches to monitoring the spatio-temporal variation of vegetation caused by mining activities,the arid climate and ecological remediation in the Shengdong coal mining area are described.Over a large regional scale it was found that the vegetation was improved as a result of ecological remediation activities.At the local scale,however,the vegetation coverage and soil moisture in the mined areas were slightly lower than those in un-mined areas due to mining subsidence.These differences are partly attributed to ground fissures that injure root systems and increase the depletion of soil moisture.It is recommended that fissures be reduced and filled to lessen their adverse effects on the environment.
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
