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最新的流體描述法采用擴(kuò)散編碼脈沖序列組成的數(shù)據(jù)系列。為了提供連續(xù)的流體(水、油和氣)飽和度和油黏度曲線，要對(duì)脈沖序列進(jìn)行同時(shí)反演。這些數(shù)據(jù)系列對(duì)擴(kuò)散系數(shù)(D)和流體弛豫時(shí)間都敏感。分子擴(kuò)散是流體中隨機(jī)的分子熱運(yùn)動(dòng)。擴(kuò)散編碼序列是CPMG序列的改進(jìn)，其中一個(gè)或兩個(gè)回波之間間隔增大。在磁場(chǎng)梯度中，分子擴(kuò)散縮短了T2弛豫時(shí)間，這種效應(yīng)在擴(kuò)散碼序列的回波間隔增大期間被放大。通過采集具有不同長(zhǎng)回波間隔的擴(kuò)散編碼數(shù)據(jù)便可直接測(cè)量分子擴(kuò)散率。
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