利用核磁共振定量肝中鐵濃度於地中海型貧血患者

Abstract

地中海型貧血的病人，需要終生的輸血，因而容易導致在身體器官的鐵質過度沉積。這些鐵質沉積主要發生於肝臟。利用原子吸收光譜儀去測定肝臟活體切片，是目前定量肝中鐵濃度最準的方法。在過去幾年中，核磁共振提供一種非侵入性的測量方法，有逐漸取代活體切片的趨勢。但是，傳統核磁共振序列(MEMPSE)的缺點為掃描時間過長。因此我們提出一種新的核磁共振序列(BHMEMPSE)，此序列在人體掃描只需要四分鐘，希望能取代傳統做法。 在本論文的第一部份，我們將不同濃度的FeCl3水溶液，用三種不同的核磁共振序列(MEMPSE，BHMEMPSE，gradient echo)掃描，發現掃描後計算出的R2/R2*數值，與FeCl3水溶液的鐵濃度呈現線性關係(在0.01 ~ 0.5 mg Fe/g的範圍內)。這個範圍相當於R2/R2*介於3 ~ 220 1/s中，適用於臨床病人的肝中鐵濃度測量。在曲線配適模型中，我們也發現mono-exponential curve fitting model是最好也最實用的方式。本論文第二部分為病人的核磁共振掃描，我們發現BHMEMPSE和MEMPSE呈現線性關係，雖然新的核磁共振序列(BHMEMPSE)的影像比較模糊，但是利用ROI圈選測量R2的方式依然可行。

In thalassemia patients, lifelong blood transfusion leads to iron overload in vital organs. Excess iron are mainly stored in the liver. The estimation of iron by atomic absorption spectroscopy in liver biopsy is the gold standard for the assessment of iron overload. In the last decade MR has been developed to replace liver biopsy and serve as an alternative non-invasive method for quantification of liver iron. However, traditional multiple spin-echo sequence has the disadvantage of long scanning time. Therefore, we proposed a new breath-hold multi-echo multi-planar spin echo (BHMEMPSE) sequence, which only takes 4 minutes in human study, to assess liver iron content. In the first part, we scanned the calibrated iron solution phantom with MEMPSE, BHMEMPSE and gradient-echo sequences. These three sequences demonstrated linear trend of R2/R2* against different concentrations of iron solution, in the range of 0.01 ~ 0.5 mg Fe/g FeCl3 solution. This range corresponds to R2/R2* range of 3 ~ 220 1/s, which is wide enough for routine clinical use. We also determined that mono-exponential curve fitting model was the best one, which was more practical for clinical use. In the second part, we demonstrated the excellent linear relationship of the BHMEMPSE sequence to the MEMPSE sequence in human study. Although the anatomic details of the BHMEMPSE images were vaguely seen, drawing a circular region of interest within the liver for R2 measurement was feasible.