查詢結果分析
來源資料
頁籤選單縮合
題 名 | 利用疊代法重建影像以改善正子電腦斷層造影影像之研究=Iterative Image Reconstruction with Random Correction for PET Studies |
---|---|
作 者 | 杜高瑩; 陳泰賓; 盧鴻興; 劉仁賢; 周國樑; 陳志成; | 書刊名 | 核子醫學雜誌 |
卷 期 | 12:4 1999.12[民88.12] |
頁 次 | 頁195-200 |
分類號 | 414.93 |
關鍵詞 | 疊代演算法; Random coincidence; True coincidence; ML-EM algorithms; |
語 文 | 中文(Chinese) |
中文摘要 | 前言:正子電腦斷層攝影主要應用於功能性定量造影,如葡萄糖代謝研究等。精準的定量造影有賴於較佳的三維影像重建法。傳統利用濾波反投影來重建影像,在核子醫學診斷上佔有重要的地位,但其最大的缺點在於假影以及雜訊的處理效果較差。藉由目前電腦的快速運算能力,本研究肯嘗試以疊代法來取代傳統的濾波反投影法,進而改善核子醫學的影像品質。 材料與方法:本研究以正子攝影機掃描線射源以及均勻水假體,分別以濾波及投影法與疊代法來重建影像,比較其間的差異,並以兩條線射源以及原始資料來區分random coincidence事件的特性,藉由實驗的資料來驗證random coincidence rate的公式是否正確。 結果與討論:實驗結果發現濾波反投影法法所重建的影像雜訊比利用疊代法重建的影像來的大,其因為疊代法重建的影像較接近實際的結果。Randomcoincidence count/true coincidence count之比值約在0.13%~0.19%之間,以理論值估算的結果,約在0.08%-0.27%左右。對於均勻射源部份,計算值約為41.8%~49.1%,理論值約為45%~49%,結果十分接近,可推論其公式為正確無誤。 結論:PET影像是一種計數的統計量,因此利用統計來重建影像是較為準確的方法,尤其在影像定量的研究,更能提供精華的數據。對於一些物理現象的誤差如random coincidence及散射事件等,其發生的機率仍需後續的實驗來找出射源間距造成相互干擾的比例關係,進而推算出整侗照野各個位置的干擾機率,期望藉此機率的分佈作為影像重建時之修正來改善PET的影像品質。 |
英文摘要 | Background: Filtered back projection (FBP) used in PET led to sever artifacts. These artifacts can be overcome with iterative reconstruction algorithms. Recently the computational effects required for routine iterative reconstruction of PET studies have been reduced to make it practically appealing. We did experimental and methodological studies to improve image quality by fast iterative reconstruction techniques developed in our previous studies. Methods: We have made an implementation of the improved Maximum Likelihood-Expectation Maximization (ML-EM) reconstruction algorithms. The transition matrix is generated based on the geometry of physical instrument. Careful designs of line sources are performed in order to find out the spatial resolution limits as well as the correction of random coincidences. The improvement of resolution limits of line sources by the ML-EM method over the FBP method is investigated thoroughly by different experimental designs. A phantom with six line sources and with nineteen line sources, respectively, was used to test the accelerated ML-EM algorithms against FBP method. The single rays were used to calculate the random coincidence ratio (RAC= 2 τ Rl,Rj) and compared to the experimental result. Results: The streak artifacts near those line sources are completely eliminated with the ML-EM method. We also design experiments using two line sources to find out the rate of random coincidence events. A new model is pro- posed for this kind of experiments. With decay correction, the random coincidence events were uniformly distributed in the whole field after 10 iterations and thus an important factor that causes error in quantification. Based on the calculation from singles data, the random event ratio was 41.8% to 49.1% in each ring. These results are close to the ratios obtained from geometric calculation. Conclusion: ML-EM reconstruction images are superior to those obtained with FBR The patterns of random coincidence events provide insightful information for random coincidence event correction, which the hardware correction by the delay window can not provide. This information is particularly valuable when the delay window correction is not available as in the case of Taipei Veterans General Hospital PET system. |
本系統中英文摘要資訊取自各篇刊載內容。