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研究生:盧怡穎
研究生(外文):Yi-Ying Lu
論文名稱:利用假體測試在臨床上利用核磁共振Dixon方法來定量脂肪肝其穩定性
論文名稱(外文):An in vitro Study to Test the Consistency of the MR Dixon Method in Quantifying Fatty Liver under Conditions Encountered in Clinical Practice
指導教授:黃文濤黃文濤引用關係
指導教授(外文):Wen-Tao Huang
學位類別:碩士
校院名稱:元培科技大學
系所名稱:醫學影像暨放射技術研究所
學門:醫藥衛生學門
學類:醫學技術及檢驗學類
論文種類:學術論文
畢業學年度:101
語文別:英文
論文頁數:37
中文關鍵詞:核磁共振Dixon方法定量脂肪肝脂肪肝肝臟脂肪比率
外文關鍵詞:MRDixon methodQuantification of fatty liverFatty liverHepatosteatosis
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研究目的:近來己有研究證實核磁共振Dixon方法可以用在臨床上定量脂肪肝。這個研究的目的在於分析一些在臨床應用時可能會遭遇到的變數,包括:取樣位置、造影範圍大小和周圍的環境,是否會影響到核磁共振Dixon方法計讀出來的肝臟脂肪比率。

材料與方法:我們製作了五個脂肪重量百分比濃度分別為0%、10%、20%、30% 和40%的均勻假體。利用的核磁共振技術是三維平行加速同相位和反相位容積插入式閉氣檢查技術,可以在病人閉得住氣的短時間內完成掃描,同時產生同相位、反相位、脂肪和水四組影像。定量肝臟脂肪時必須計算脂肪指數。四個以往被提出來的脂肪指數計算公式被納入這個研究。這四個公式依序是:同相位信號強度-反相位信號強度、(同相位信號強度-反相位信號強度)/同相位信號強度、同相位信號強度/反相位信號強度、脂肪影像訊號強度/水影像訊號強度。我們測試取樣位置、造影範圍大小和周圍的環境是否會影響到影像上的信號強度和計算出來的脂肪指數。

結果:我們發現在四組影像中,反相位影像的信號強度和脂肪比率的關係呈現轉折的現象:信號強度在脂肪比率較低時會隨著脂肪比率增加而降低,到了約30%的比率時會出現反轉,在脂肪比率超過30%時信號強度會變成隨著脂肪比率增加而增加。而本研究中的前三個公式有利用反相位影像的信號強度來計算脂肪指數,其脂肪指數和脂肪比率的關係也會呈現轉折的現象。研究顯示取樣位置會輕微地影響到影像上的信號強度和計算出來的脂肪指數;造影範圍大小會影響影像上的信號強度但不影響計算出來的脂肪指數;周圍的環境會影響影像上的信號強度和前兩個公式計算出來的脂肪指數,但不影響後兩個公式計算出來的脂肪指數。

結論:我們建議當我們在臨床上利用核磁共振Dixon方法來定量脂肪肝時,利用本研究中的第四個公式來計算脂肪指數。因為它計算出來的脂肪指數和脂肪比率的關係是線性的,沒有轉折的現象;而且它不受造影範圍大小和周圍的環境的影響。因為在左右方向上的取樣位置會輕微地影響到脂肪指數,所以在左右方向上儘量固定取樣點,可以避免這個微小的誤差。

Purpose: The MR Dixon method has shown great potential for quantifying fatty liver. This study focuses on whether the sampling site, the field of view, and the surrounding material influence the fat-fraction reading by MR Dixon method.

Materials and Methods: Five phantoms of 0%, 10%, 20%, 30%, and 40% fat in weight percentage were prepared. A 3-dimensional parallel-accelerated in- and opposed-phase volumetric interpolated breath-hold examination sequence was used. Four sets of images, in-phase, opposite-phase, fat and water images, were obtained in one scanning. For quantifying fat fraction, fat indices calculated from signal intensities should be obtained. Four previously proposed formulas calculating fat indices were include in this study: signal intensity on in-phase image - signal intensity on opposite-phase image; (signal intensity on in-phase image - signal intensity on opposite-phase image) / signal intensity on in-phase image; signal intensity on in-phase image / signal intensity on opposite-phase image; signal intensity on fat image / signal intensity on water image. We tested whether the sampling site, the field of view, and the surrounding material influenced the signal intensities on the MR images and the fat indices calculated using the 4 formulas.

Results: The turning point phenomenon of SIopposite was noted. The sampling site on the left to right direction mildly influenced the SIs and fat indices. The FOV influenced the SIs, but not the fat indices. The surrounding material did not influence the fat indices of the last 2 formulas.

Conclusion: We suggest using the last formula, signal intensity on fat image / signal intensity on water image, for quantifying fatty liver because it has no turning point problem and it is not influenced by the FOV and the surrounding material. We also suggest a fixed sampling site on the left to right direction to avoid the trivial bias caused by sampling site.

Table of Contents
Abstract in Chinese………………………………………………………i
Abstract in English………………………………………………………iii
Acknowledgement……………………………………………………………v
Chapter 1 (Introduction)………………………………………………1
1.1 Definition of Fatty Liver……………………………………1
1.2 Clinical Significance of Fatty Liver………………………1
1.3 Diagnosis of Fatty Liver…………………………………………2
1.4 Imaging Studies of Fatty Liver………………………………2
1.5 Quantification of Fatty Liver with MR Dixon Method……2
1.6 Purpose of Our Study – Test the Consistency of MR Dixon Method under Different Conditions in Clinical Practice………………3
Chapter 2 (Materials and Methods)………………………………………4
2.1 Phantom Preparation……………………………………………4
2.2 MR Protocol……………………………………………………7
2.3 Conditions for Test……………………………………………7
2.3.1 Site of Sampling……………………………………………7
2.3.2 Field of View………………………………………………11
2.3.3 Surrounding Material………………………………………11
2.4 Reading of Fat Fraction…………………………………………11
2.5 Statistic Analysis………………………………………………12
Chapter 3 (Results)……………………………………………………14
3.1 The Relationship between Fat Fraction and the Four Sets of Signal Intensities on the MR Imaging……………………14
3.2 The Relationship between Fat Fraction and Four Fat Indexes Calculated by the Four Formulas……………………………19
3.3 Influences of the Tested Conditions………………………24
3.3.1 Site of Sampling……………………………………………24
3.3.2 Field of View………………………………………………28
3.3.3 Surrounding Material…………………………………….28
Chapter 4 (Discussion)…………………………………………………31
4.1 A Convenient and Economic Phantom-Making Method……….31
4.2 Phenomenon of Turning Point on Images Obtained with MR Dixon Method………………………………………………………31
4.3 Fix Site of Sampling to Avoid Bias……………………………32
4.4 Use Proper Formulas to Avoid Bias……………………………32
4.5 The Formula We Recommended………………………………32
4.6 Advanced Study………………………………………………33
Chapter 5 (Conclusion)…………………………………………………34
5.1 Consistency of MR Dixon Method in Quantifying Fatty Liver………………………………………………………………34
5.2 Suggesting the formula “Fat Index = SIfat / SIwater ” for Quantifying Fatty Liver ………………………………………………34
References………………………………………………………………35


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