臺灣博碩士論文加值系統

由於科技的進步，電腦斷層血管攝影逐漸成為診斷腦血管疾病的一項利器，且其有「非侵入性」的優點。將骨頭構造從影像中去除、只保留腦血管的這項後處理技術，是電腦斷層血管攝影相當重要的一環。然而，傳統手動去骨方式耗時又常不盡理想，尤其是骨頭和血管緊密接觸的部位，如顱底部分，骨骼構造常無法完全地去除，而造成影像判讀上的困難或誤差。
近期新發展的後處理技術，如自動數位去骨技術(digital bone subtraction)和雙能影像去骨技術(dual-energy bone removal)，可增進電腦斷層血管攝影的後處理效率以及影像的品質。自動數位去骨技術是將顯影劑注射後的影像減去注射前的影像，以便將骨頭去除、留取腦部血管的影像。然而、這項技術的缺點在於輻射劑量的增加(因為必須有一組顯影劑注射前的影像)，而且患者如果在打顯影劑前和打顯影劑後的兩組影像之間有移動的話，骨頭就無法完全去除。
最新的雙能電腦斷層掃描儀是以雙球管同時發射出不同能量的X射線，由於能量吸收的區段不同藉此可區分骨頭與血管。利用這種技術，只需一組注射顯影劑後的影像，就可以做出去除骨頭的三維立體血管影像。
此研究的目的，是比較兩種不同的影像後處理技術: 雙能電腦斷層動脈攝影(Dual-Energy CTA) 和數位去骨電腦斷層動脈攝影 (NeuroDSA CTA)，兩者之間在輻射劑量、影像後處理時間、動脈瘤診斷時間、和血管影像品質等方面是否有差異。
研究結果顯示雙能和數位去骨兩種電腦斷層動脈攝影皆適用於頭頸部血管的影像判讀。數位去骨電腦斷層動脈攝影在顱底部位有較佳的血管影像，而雙能電腦斷層在頸部有較佳的血管影像。

With rapid improvement in computed tomography (CT) scanners, computed tomographic angiography (CTA) has become a useful and noninvasive imaging technique for evaluating cerebrovascular disease. Bone removal is an important technique in CTA of head and neck, in order to leave the images of arterial structures, to reformat and reconstruct vascular structures, and to evaluate intracranial vessels. However, conventional threshold-based manual bone removal is time-consuming and is often incomplete in regions of close vessel-bone contact, such as skull base.
Recently developed techniques in image post-processing, such as digital bone subtraction and dual-energy bone removal, have made CTA images more efficient and delicate. In digital bone subtraction method, two sets of CT data, non-enhanced and enhanced images, are obtained. The software automatically matches the bony structures on non-enhanced images to the enhanced images, and selectively removes bone. Vascular structures are remained visible. However, this method shows increased radiation dose due to one additional CT scan (non-enhanced image data), and the result of subtraction is suboptimal if the patient moves during these two sets of CT scans.
With the use of dual-energy dual-source CT, two sets of image data can be simultaneously acquired with different tube voltages, corresponding to different X-ray energies. Materials can be differentiated by analyzing their attenuation differences depending on tube voltage. The attenuation difference between two X-ray energies is especially large in materials with high atomic numbers such as iodine. Thus bones, which show a smaller attenuation difference, can be distinguished from iodine. As a result, dual-energy CT is able to eliminate bony structures using only a single CT data acquisition, and is useful in CTA of head and neck to evaluate cerebral vascular diseases.
The purpose of this study is to compare the radiation dose, image post-processing time, aneurysm detection time, and vascular image quality between two different bone-removal software: NeuroDSA (matched mask bone elimination) and Dual-Energy (dual-energy CTA).
The results showed that both Dual-Energy and NeuroDSA were feasible software for bone subtraction in cerebral CTA. NeuroDSA showed better vascular quality at skull base, while Dual-Energy was superior in vessels of neck.

摘要 I
Abstract II
誌謝 IV
Contents V
List of Figures VI
List of Tables VII
Chapter 1 1
1.1 Background 1
1.2 Basic principles of CT 1
1.3 Dual Source CT Scanner 3
1.4 Cerebral Aneurysm 5
1.4.1 Image detection of cerebral aneurysm 6
1.4.2 Bone removal methods in CTA 7
Chapter 2 10
2.1 Patients 10
2.2 Equipment and CT Examination10
2.3 Imaging Post-processing 11
2.4 Image Evaluation 12
2.5 Volume of Subtracted Bone 13
2.6 Statistical Analysis 15
Chapter 3 16
3.1 Radiation Dose 16
3.2 Post-processing Time 16
3.3 Volume of Subtracted Bone 17
3.4 Detection Time of Cerebral Aneurysm 17
3.5 Vascular Quality Analyses 18
Chapter 4 19
4.1 Discussion 19
4.2 Conclusion 21
References 23

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