臺灣博碩士論文加值系統

由於磁振造影技術的進步，胎兒的影像已經能由T2權重快速自旋回訊這類快速成像的方法所取得。而胎兒三維影像，根據文獻上所發表之結果是以29秒的時間所取得。然而，因為胎兒胎動以及母體呼吸所造成的震動，太長的掃瞄時間會因為移動使得影像品質大受影響。在此研究中，我們將提出一種三維影像的重建方法，擬三維影像(pseudo-3D imaging)，其目的是希望能應用在這類受掃瞄時間限制的影像，比如說胎兒影像。
本研究中，所提出的方法重點在於我們利用三組較厚之正交切面的二維影像，經由適當的數學演算推得完整的三維資料，並且能提高其空間解析度。而經由移除區塊的後處理，可進一步加強影像的對比，提高其可讀性。經由電腦模擬和實際的實驗結果，在對位無誤的前提下，證實此三維重建方法確實可行。因此，在受掃瞄時間限制而無法取得三維影像的情況下，我們所提出的這種影像重建方法不但可得到三維影像，且其解析度及影像品質亦為臨床人員所接受。

Due to recent advances in Magnetic Resonance (MR), fetal images could be acquired by using fast MR imaging sequences, such as T2-weighted fast spin echo (SE). Preliminary results on fetal MR imaging in three-dimension directly, which facilitates thin-slice acquisition, have been demonstrated with scan time on the order of 29 sec. However, the current scan time can be detrimental to image quality in terms of both maternal respiratory motion and fetal motion. Here, we propose to develop a mathematically based method, pseudo-3D imaging, that could potentially be applied to fetal MR imaging.
The main idea of pseudo-3D is that we use three sets of orthogonal 2D thick-slice images and by proper mathematically calculation the 3D volume data can be reconstructed with improving resolution. The post-processing of eliminating block effect is used to improve the quality of reconstructed images and makes images more readable. The results from both the mathematical phantom and experimental studies show that the proposed algorithm is theoretically feasible in the absence of image mis-registration. Therefore, in situations where true 3D acquisition is hampered by factors such as scan time rendering multi-slice 2D acquisition to be the only possible approach, pseudo-3D reconstruction using three orthogonal 2D slices seems to be a good alternative to achieve MR imaging with a pseudo isotropic spatial resolution.

Chinese Abstract
English Abstract
1.INTRODUCTION1-1
2.THEORY2-1
2-1.Image Acquisition and Reconstruction Procedure2-1
2-2.Pseudo-Inverse Matrix Solving2-5
2-3.Block Effect Elimination2-7
3.MATERIAL AND METHODS3-1
3-1.Simulation 1: Computer Modeling Simulation3-1
3-1.Simulation 2: Validation of pseudo-3D method on adult brain images
3-3
3-3.Simulation 3: 3D-rendering of human brain3-5
4. RESULTS4-1
4-1.Result on Simulation 14-1
4-2.Result on Simulation 24-2
4-3.Result on Simulation 34-5
5. DISCUSSION5-1
5-1.Inherent restriction of pseudo-3D imaging5-2
5-2.Choice of resolution for 2D image acquisition5-4
5-3.A preliminary evaluation on the feasibility of fetal MR imaging5-6
5-4.Conclusion5-8
APPENDIX: REFERENCESA-1

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