一维核磁共振(nuclear magnetic resonance,NMR)测量方法无法分辨驱替过程中油水弛豫信号,因此采用T_(1)-T_(2)二维核磁共振测量方法分辨岩心中流体类型及分布。通过驱替实验研究聚合物BRH-325和表面活性剂GSS-A复合体系分别在65、70、7...一维核磁共振(nuclear magnetic resonance,NMR)测量方法无法分辨驱替过程中油水弛豫信号,因此采用T_(1)-T_(2)二维核磁共振测量方法分辨岩心中流体类型及分布。通过驱替实验研究聚合物BRH-325和表面活性剂GSS-A复合体系分别在65、70、75℃条件下的驱油效果,并利用纵向弛豫-横向弛豫(T_(1)-T_(2))二维NMR测量方法对岩心内部的油水两相驱替规律及分布特征进行可视化研究,并对比实验测量结果与NMR测量结果。结果表明:70℃下,复合驱提高采收率的效果最为明显。因此,T_(1)-T_(2)二维核磁共振能够直接、直观区分驱替过程中油水的弛豫信号。展开更多
Understanding the structure of tropical cyclone(TC)hydrometeors is crucial for detecting the changes in the distribution and intensity of precipitation.In this study,the GMI brightness temperature and cloud-dependent ...Understanding the structure of tropical cyclone(TC)hydrometeors is crucial for detecting the changes in the distribution and intensity of precipitation.In this study,the GMI brightness temperature and cloud-dependent 1DVAR algorithm were used to retrieve the hydrometeor profiles and surface rain rate of TC Nanmadol(2022).The Advanced Radiative Transfer Modeling System(ARMS)was used to calculate the Jacobian and degrees of freedom(△DOF)of cloud water,rainwater,and graupel for different channels of GMI in convective conditions.The retrieval results were compared with the Dual-frequency Precipitation Radar(DPR),GMI 2A,and IMERG products.It is shown that from all channels of GMI,rain water has the highest△DOF,at 1.72.According to the radiance Jacobian to atmospheric state variables,cloud water emission dominates its scattering.For rain water,the emission of channels 1–4 dominates scattering.Compared with the GMI 2A precipitation product,the 1DVAR precipitation rate has a higher correlation coefficient(0.713)with the IMERG product and can better reflect the location of TC precipitation.Near the TC eyewall,the highest radar echo top indicates strong convection.Near the melting layer where Ka-band attenuation is strong,the double frequency difference of DPR data reflects the location of the melting.The DPR drop size distribution(DSD)product shows that there is a significant increase in particle size below the melting layer in the spiral rain band.Thus,the particle size may be one of the main reasons for the smaller rain water below the melting layer retrieved from 1DVAR.展开更多
This work aims to develop fast T_(1)mapping methods for preclinical and clinical scanners based on subspace-constrained reconstructions.Two sequences are explored for rapid T_(1)characterizations:1)Interleaved spatiot...This work aims to develop fast T_(1)mapping methods for preclinical and clinical scanners based on subspace-constrained reconstructions.Two sequences are explored for rapid T_(1)characterizations:1)Interleaved spatiotemporal encoding incorporating variable repetition times.2)Inversion recovery gradient echo with random sampling of the phaseencoding(PE)dimension.For both sequences,the subspace reconstruction of the signal recovery was applied,to jointly reconstruct the down-sampled images while characterizing the T_(1)relaxation.In vivo scans on human brains and abdomens confirmed the efficiency of the proposed methods,including compatibility with breath-holding.In addition,Scans on animals with abdominal tumors and dynamic contrast-enhanced T_(1)mapping on kidneys support the applicability of the proposed methods also in preclinical settings.展开更多
目的:纵向弛豫时间定量成像(T_(1) mapping)可以无创性定量心肌初始纵向弛豫时间(T_(1)值),在钆延时强化灶(late gadolinium enhancement,LGE)基础上提供更多的心肌纤维化信息。但传统的测量T_(1)值的方法由于感兴趣区(regions of inter...目的:纵向弛豫时间定量成像(T_(1) mapping)可以无创性定量心肌初始纵向弛豫时间(T_(1)值),在钆延时强化灶(late gadolinium enhancement,LGE)基础上提供更多的心肌纤维化信息。但传统的测量T_(1)值的方法由于感兴趣区(regions of interest,ROI)需包括短轴全部心肌(the whole short axis,SAX),操作复杂且耗时,因而限制了其在临床上的应用。本研究拟对比中间层间隔壁(conservatively within the midventricular septum,ConSept)法和SAX法获得的初始T_(1)值诊断心肌弥漫性病变的能力。方法:回顾性收集中南大学湘雅医院采用3.0T心脏磁共振扫描的38例非缺血性扩张型心肌病(non-ischemic dilated cardiomyopathy,NIDCM)患者和27例健康对照者。根据NIDCM患者是否存在LGE分为LGE阳性组和LGE阴性组。将ROI分别放置在ConSept或SAX进行初始T_(1)值测量,比较两种方法区分病变心肌和健康心肌的能力以及两种方法测得的心肌初始T_(1)值的差别。结果:NIDCM组采用ConSept或SAX法测得的初始T_(1)值均明显高于对照组(均P<0.001),LGE阳性组的初始T_(1)值均大于LGE阴性组(均P<0.05)。ConSept法和SAX法测得的中间层T_(1)值与基底层、心尖层T_(1)值无明显差别(均P>0.05),具有非常好的一致性[(concordance correlation coefficient,CCC)=0.954]。结论:与SAX法相比,ConSept法是一种等效且更简便的测量心肌初始T_(1)值的方法,适合在临床工作中使用。展开更多
文摘一维核磁共振(nuclear magnetic resonance,NMR)测量方法无法分辨驱替过程中油水弛豫信号,因此采用T_(1)-T_(2)二维核磁共振测量方法分辨岩心中流体类型及分布。通过驱替实验研究聚合物BRH-325和表面活性剂GSS-A复合体系分别在65、70、75℃条件下的驱油效果,并利用纵向弛豫-横向弛豫(T_(1)-T_(2))二维NMR测量方法对岩心内部的油水两相驱替规律及分布特征进行可视化研究,并对比实验测量结果与NMR测量结果。结果表明:70℃下,复合驱提高采收率的效果最为明显。因此,T_(1)-T_(2)二维核磁共振能够直接、直观区分驱替过程中油水的弛豫信号。
基金funded by the National Key Research and Development Program of China(Grant No.2022YFC3004202)the National Natural Science Foundation of China(Grant Nos.U2142212 and 42105136)。
文摘Understanding the structure of tropical cyclone(TC)hydrometeors is crucial for detecting the changes in the distribution and intensity of precipitation.In this study,the GMI brightness temperature and cloud-dependent 1DVAR algorithm were used to retrieve the hydrometeor profiles and surface rain rate of TC Nanmadol(2022).The Advanced Radiative Transfer Modeling System(ARMS)was used to calculate the Jacobian and degrees of freedom(△DOF)of cloud water,rainwater,and graupel for different channels of GMI in convective conditions.The retrieval results were compared with the Dual-frequency Precipitation Radar(DPR),GMI 2A,and IMERG products.It is shown that from all channels of GMI,rain water has the highest△DOF,at 1.72.According to the radiance Jacobian to atmospheric state variables,cloud water emission dominates its scattering.For rain water,the emission of channels 1–4 dominates scattering.Compared with the GMI 2A precipitation product,the 1DVAR precipitation rate has a higher correlation coefficient(0.713)with the IMERG product and can better reflect the location of TC precipitation.Near the TC eyewall,the highest radar echo top indicates strong convection.Near the melting layer where Ka-band attenuation is strong,the double frequency difference of DPR data reflects the location of the melting.The DPR drop size distribution(DSD)product shows that there is a significant increase in particle size below the melting layer in the spiral rain band.Thus,the particle size may be one of the main reasons for the smaller rain water below the melting layer retrieved from 1DVAR.
基金funded by the Israel Science Foundation(grants 3594/21 and 1874/22)the Clore Institute for High Field Magnetic Resonance Imaging and Spectroscopy and by the Azrieli Institute for Brain Imaging(Weizmann Institute),by China Scholarship Council(CSC)grant 201806310085+2 种基金the National Key Research and Development Program grant 2023YFE0113300the Magnetic Resonance Technology Alliance of the Chinese Academy of Sciences Scientific Research Instrument and Equipment Development Project grant 2021GZL001the Israel Cancer Research Foundation and by Israel's Planning and Budget Committee(Lingceng Ma,international student fellowship).
文摘This work aims to develop fast T_(1)mapping methods for preclinical and clinical scanners based on subspace-constrained reconstructions.Two sequences are explored for rapid T_(1)characterizations:1)Interleaved spatiotemporal encoding incorporating variable repetition times.2)Inversion recovery gradient echo with random sampling of the phaseencoding(PE)dimension.For both sequences,the subspace reconstruction of the signal recovery was applied,to jointly reconstruct the down-sampled images while characterizing the T_(1)relaxation.In vivo scans on human brains and abdomens confirmed the efficiency of the proposed methods,including compatibility with breath-holding.In addition,Scans on animals with abdominal tumors and dynamic contrast-enhanced T_(1)mapping on kidneys support the applicability of the proposed methods also in preclinical settings.
文摘目的:纵向弛豫时间定量成像(T_(1) mapping)可以无创性定量心肌初始纵向弛豫时间(T_(1)值),在钆延时强化灶(late gadolinium enhancement,LGE)基础上提供更多的心肌纤维化信息。但传统的测量T_(1)值的方法由于感兴趣区(regions of interest,ROI)需包括短轴全部心肌(the whole short axis,SAX),操作复杂且耗时,因而限制了其在临床上的应用。本研究拟对比中间层间隔壁(conservatively within the midventricular septum,ConSept)法和SAX法获得的初始T_(1)值诊断心肌弥漫性病变的能力。方法:回顾性收集中南大学湘雅医院采用3.0T心脏磁共振扫描的38例非缺血性扩张型心肌病(non-ischemic dilated cardiomyopathy,NIDCM)患者和27例健康对照者。根据NIDCM患者是否存在LGE分为LGE阳性组和LGE阴性组。将ROI分别放置在ConSept或SAX进行初始T_(1)值测量,比较两种方法区分病变心肌和健康心肌的能力以及两种方法测得的心肌初始T_(1)值的差别。结果:NIDCM组采用ConSept或SAX法测得的初始T_(1)值均明显高于对照组(均P<0.001),LGE阳性组的初始T_(1)值均大于LGE阴性组(均P<0.05)。ConSept法和SAX法测得的中间层T_(1)值与基底层、心尖层T_(1)值无明显差别(均P>0.05),具有非常好的一致性[(concordance correlation coefficient,CCC)=0.954]。结论:与SAX法相比,ConSept法是一种等效且更简便的测量心肌初始T_(1)值的方法,适合在临床工作中使用。
