臺灣博碩士論文加值系統

數位減贅血管攝影(digital subtraction angiography, DSA)，被視為診斷腦血管疾病的黃金標準，因其提供了良好的空間與時間解析度的二維投影影像。而隨後發展的三維螺旋血管攝影(three-dimensional rotational angiography, 3DRA)，提供了三維血管結構影像，解決DSA投影造成血管重疊的問題，卻喪失時間的資訊。四維數位減贅血管攝影(four-dimensional digital subtraction angiography, 4D-DSA)利用單次對比劑注射後掃描的影像，重建出具有時間性的三維血管影像，以解決DSA與3DRA的不足。本研究的目的為實現4D-DSA的演算法，評估其可行性與可能的問題，並將其實際應用於臨床影像的重建，以得到時間對比劑濃度曲線(time-concentration curve)。
本研究首先在電腦模擬中建立圓柱型、Y型與擬人結構，並模擬三種對比劑的血流模型，以測試重建演算法的可行性與準確性。假體實驗則使用水流假體，並與相同對比劑注射條件下的傳統DSA前後投影(anterior posterior view)比較。最後以回溯式的研究，分析一位正常病患的影像，在4D-DSA重建後得到時間對比劑濃度曲線，經曲線擬合後，計算TTP (time to peak)、Ta (arrival time)、Wash-in slope、AUC (area under curve)、FWHM (full width at half maximum)等五個腦血流動力學參數。
電腦模擬中4D-DSA重建結果的時間對比劑濃度曲線，與所模擬的血流模型的相關係數皆大於0.95。假體實驗與傳統DSA比較的結果，相關係數皆大於0.9。臨床影像則成功重建，並計算出腦血流動力學參數，結果顯示4D-DSA之重建是合理且可行的。我們發現三維重建之複合影像(composite image)的不準確與頭骨與高衰減物質所產生的散射和射束硬化假影，是導致4D-DSA重建的訊號不準確最主要的原因。
本研究成功的實現了4D-DSA的演算法，驗證了4D-DSA的可行性，並將之應用於臨床影像的重建，計算血液動力學參數。未來努力的方向是增進4D-DSA提供時間對比劑濃度曲線的準確性。

Conventional digital subtraction angiography (DSA) is a gold standard in diagnosing cerebral vascular diseases because of its great spatial and temporal resolution. Three-dimensional rotational angiography (3DRA) is developed to overcome the vascular overlapping in DSA, but time information is lost. Four-dimensional digital subtraction angiography (4D-DSA) uses multiplicative projections, which are acquired at fixed angular increment, in a single contrast medium injection to generate time resolved 3D images. The purpose of this study is to establish the 4D-DSA reconstruction algorithm. Furthermore, we evaluated the feasibility and problems of 4D-DSA and analyzed the clinical data.
At first, computer simulation was performed using three types of digital vascular structure including: cylinder; Y shape; and emulation of human vessels. Three flow patterns were simulated to verify the accuracy and feasibility of 4D-DSA reconstruction algorithm. Secondly, the projection data of phantom were reconstructed and compared with conventional DSA in the same injection condition which was used as standard. Thirdly, through the time-concentration curve generated by 4D-DSA reconstruction algorithm, we retrospectively analyzed a clinical case without any special finding. Five hemodynamic parameters including TTP (time to peak), Ta (arrival time), Wash-in slope, AUC (area under curve), FWHM (full width at half maximum) were calculated for evaluation.
The correlation coefficients between 4D-DSA time-concentration curve and standard curve were higher than 0.95 in computer simulations and 0.9 in phantom studies. It was reasonable and feasible to offer the time-concentration curve by 4D-DSA. The inaccuracy of time-concentration curve was mainly caused by inaccurate 3D reconstruction, scatter, and beam hardening artifacts produced by high attenuation material such as temporal bone or dental implants.
In conclusion, we successfully established the 4D-DSA reconstruction algorithm and verified the 4D-DSA algorithm was feasible and reasonable. Furthermore, we reconstructed the clinical data and estimated hemodynamic parameters. In the future, we will try to improve the accuracy of time-concentration curve provided by 4D-DSA.

摘要 i
Abstract ii
目錄 iii
圖表目錄 v
第一章 緒論 1
1.1研究背景 1
1.2論文架構 5
第二章 基本理論 6
2.1數位減贅血管攝影 6
2.2三維螺旋血管攝影 9
2.3四維數位減贅血管攝影 13
2.3.1影像擷取 15
2.3.2三維重建 18
2.3.3再投影(re-projection) 23
2.3.4插入時間訊號 25
第三章 實驗流程與方法 30
3.1實驗設備 31
3.2電腦模擬 32
3.3假體實驗 37
3.4臨床影像 41
3.5四維數位減贅血管攝影重建 42
3.6最大強度投影 44
3.7相關性評估 45
3.8曲線擬合與計算血液動力學參數 46
第四章 實驗結果 49
4.1電腦模擬結果 49
4.1.1影像結果 49
4.1.2 ROI圈選結果 54
4.2假體實驗結果 60
4.3臨床影像重建結果 66
第五章 討論與結論 71
5.1討論 71
5.2結論 78
參考文獻 79

圖2.1 數位減贅血管攝影示意圖 8
圖2.2 三維螺旋血管攝影所截取的影像 10
圖2.3 三維螺旋血管攝影所截取並經過減贅後的影像 11
圖2.4 血管三維結構經最大強度投影的結果 12
圖2.5 四維數位減贅血管攝影重建流程與示意圖 14
圖2.6 四維數位減贅血管攝影示意圖 16
圖2.7 四維數位減贅血管攝影所截取的影像 17
圖2.8 正弦圖示意圖 18
圖2.9 將投影影像Pβ(p', ζ')縮小至旋轉中心形成Rβ(p, ζ)的示意圖 20
圖2.10 將經過濾波後的投影影像Qβ(p, ζ)反投影的示意圖 21
圖2.11 複合影像之重建示意圖 22
圖2.12 錐形射束投影示意圖 24
圖2.13 再投影結果 24
圖2.14 插入時間訊號示意圖 28
圖2.15 四維數位減贅血管攝影時間濃度曲線示意圖 29
圖3.1 假體結構示意圖 33
圖3.2 時間對比劑濃度曲線示意圖 35
圖3.3 訊號隨時間變化擬人假體的前後投影 35
圖3.4 實際對比劑注射入假體所產生之時間對比劑濃度曲線 36
圖3.5 假體示意圖 39
圖3.6 重建假影示意圖 43
圖3.7 最大強度投影示意圖 44
圖3.8 特性參數示意圖 48
圖4.1 圓柱假體之四維數位減贅血管攝影重建，第25個切面影像結果 50
圖4.2 Y型假體之四維數位減贅血管攝影重建，第25個切面影像結果 51
圖4.3 擬人假體之四維數位減贅血管攝影重建，第25個切面影像結果 52
圖4.4 擬人假體之四維數位減贅血管攝影影像最大強度投影 53
圖4.5 電腦模擬之ROI圈選位置示意圖 55
圖4.6 擬人假體曲線一之四維減贅血管攝影重建，ROI圈選結果 56
圖4.7 擬人假體曲線二之四維減贅血管攝影重建，ROI圈選結果 57
圖4.8 擬人假體曲線三之四維減贅血管攝影重建，ROI圈選結果 58
表4.1 電腦模擬影像經四維數位減贅血管攝影之重建，ROI中時間對比劑濃度曲線之相關係數結果 59
圖4.9 假體實驗之四維數位減贅血管攝影影像之結果 61
圖4.10 假體實驗之二維數位減贅血管攝影 62
圖4.11 假體實驗ROI圈選位置示意圖 63
表4.2 假體實驗ROI圈選結果之相關係數 63
圖4.12 假體實驗之四維數位減贅血管攝影，ROI圈選結果 65
圖4.13 四維數位血管攝影，前後投影 67
圖4.14 四維數位血管攝影，側位投影 67
圖4.15 ROI位置選取，前後投影 68
圖4.16 ROI位置選取，側位投影 68
圖4.17 臨床影像之四維數位減贅血管攝影，ROI圈選結果 69
表4.3 ROI選取的時間對比劑濃度曲線第一次曲線擬合結果 70
表4.4 ROI選取的時間對比劑濃度曲線第二次曲線擬合結果 70
圖5.1 圓柱假體模型與三維重建之影像重疊示意圖 73
圖5.2 閾值處理前後的時間對比劑濃度曲線 73
圖5.3 高衰減物質造成血管訊號下降的示意圖 75

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