簡化正子斷層掃描影像在疉代重建之機率矩陣

背景：利用maximum likelihood expectation maximization(MLEM)方法重建正子斷層掃描(PET)影像，其結果比常規所使用的濾波反投影法(filtered back projection;FBP)更爲精確。但在重建過程中，需要利用機率矩陣(probabilitymatrix)來計算期望值。由於它的矩陣非常大，增加儲存及運算的困難，而且它的建立需利用點射源對所有field of view(FOV)内各像素點逐一掃描，非常费時。本研究旨在發展一新的機率記綠方式，以大幅缩小機率矩陣的大小。方法：本研究提出新的機率矩陣，利用PET掃描儀的環式偵检器與像素之間的對稱關係，减少矩陣中冗餘的部分。以簡化之矩陣代入MLEM方法用於2D Hoffman數位假體的模擬資料與PC-4096-15WB PET的實際點射源資料之重建，評估用新機率矩陣重建後的影像品質。結果：機率矩陣大小缩减爲原本的1/n^(2)（n^(2)為影像像素數目），運用此機率矩陣重建的影像，其影像品質並未受影響。矩陣的產生僅需要兩次線射源的掃描。結論：新的機率矩陣能大量缩减其儲存空間及校正時間。

關鍵字

MLEM重建法；機率矩陣； PET掃描儀

並列摘要

Background: The maximum likelihood expectation maximization(MLEM)method for PET reconstruction is more accurate than the conventional filtered back projection(FBP)algorithm. However, the probability matrix is huge and its generation requires the scan of a point source moving through every location inside the FOV. The purpose of this study is to develop a method to reduce the size of the probability matrix for a ring system to improve the iterative speed of statistical reconstruction. Methods: We utilized the geometric relationship between the pixel and detector pairs in the ring to factorize the probability matrix into two smaller independent matrices and reduce the matrix size significantly. A simulated 2DHoffman digital phantom data and a real line source data from PC-4096-15WB PET scanning were used to assess the image quality of the MLEM reconstruction incorporating the new probability matrix. Results: The size of the simplified probability matrices are reduced by a factor of n^(2).The reconstructed images of this method do not show any deterioration in the quality. It is feasible to generate the probability matrix using only two scans of line sources. Conclusion: The new method reduces storage requirement without affecting image quality. The generation of prob-ability matrix is greatly simplified.

並列關鍵字

probability matrix ； MLEM ； PET

國際替代計量

簡化正子斷層掃描影像在疉代重建之機率矩陣

全文下載

主題瀏覽