整合傅立葉重分裝法與正弦圖頻域
去雜訊技術之三维正子斷層掃描
影像重建

正子斷層造影是近年來發展出的相對較新的醫學影像診斷技術，它為人體提供具備生化功能性變化之影像資訊，有助於疾病的早期發現。由於正子斷層掃瞄造影時，射源分散在體內，且能打入體內的總放射劑量有限，因此其訊噪比遠小於電腦斷層造影，因而影響重建影像的品質。另外因為光子的散射、衰減或系統的偵測效率等問題，使系統誤判放射源之投影角度與位置，造成正弦圖中的資料錯誤。本論文針對正子斷層造影資料，在未重分裝前的正弦圖，根據2004年Ramesh Neelamani、Hyeokho Choi 及Richar Baraniuk所提出之傅立葉小波正規反迴旋積分理論，利用結合a posteriori wiener filter與傅立葉頻域小波分析來將雜訊濾除，但儘量保留信號細節，然後再進行重分裝，將正確的斜向正弦圖重組到正向正弦圖上，然後得到品質較佳且正確的重建影像堆疊。在假體造影的實驗中，假體經正子斷層掃描產生正向與斜向的正弦圖，若僅經過a posteriori wiener filter處理的正弦圖，重建後影像上之ROI，平均變異係數降低最多約8.38%。若正弦圖只經過頻域小波處理，則重建影像上之ROI，平均變異係數降低最多約11.39%。若經過本文所提結合上述兩種方法處理正弦圖，則重建影像上之ROI，平均變異係數降低最多約15.43%，但對比C值並沒有對應地降低。本論文所提出之處理方法，除可獲得較佳之正子造影影像品質外，在影像處理及重建速度方面，亦能獲得臨床應用時可以被接受之效率。後續研究，應可將本法用於更真實的假體實驗及實際臨床上之分析與比較。此外，也可延伸本法至各種真正的三維正子造影影像重建。

關鍵字

a posteriori wiener filter ；重分裝；傅立葉頻域小波分析；正子斷層掃描

並列摘要

Positron emission tomography (PET) is a relatively new diagnostic technology in medical imaging. The technology provides biochemistry information of human body and assists in detecting disease in its early stage. However, because of the distributed nature of radioactive source inside human body and the limited amount of the source that is allowed to be injected into human body, the signal-noise-ratio (SNR) is much lower than that of computer assisted tomography. In addition, the inherent problems involved in PET such as scatter and attenuation of gamma ray further deteriorate the image quality of PET. In this study, we tried to improve SNR of PET image while preserving the image details at the same time. Based on the Fourier-Wavelet Regularized Deconvolution proposed by Neelamani, we combined a posteriori wiener filter (APWF) and wavelet analysis in Fourier domain (WAFD) to remove noise but not information in 3D PET sinograms. We then proceeded to put oblique sonograms correctly into the direct sonograms using Fourier rebinning. In the phantom experiment, APWF decreased the coefficient of variation (CV) of the image of hot spheres up to 8.38%. The CVs were 11.39% and 15.43% for WAFD and the combined method, respectively. We also found that the object-background contrasts of the hot spheres stayed about the same as those without filtering applied. In conclusion, we found that the proposed combination of APWF and WAFD reduced the CV most while keeping the same object-background contrast. Future researches could further validate the method on more realistic phantoms and real clinical studies, and extend the current method in various and true 3D PET reconstruction alogorithms.

並列關鍵字

positron emission tomography ； rebinning ； wavelet analysis in Fourier domain ； a posteriori Wiener filter

參考文獻

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國際替代計量

整合傅立葉重分裝法與正弦圖頻域去雜訊技術之三维正子斷層掃描影像重建

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