Estimation of Attenuation and Activity Images in Time-of-flight Flat-Panel Positron Emission Tomography System

• Main Authors: Yueh Hsu, 許悅
• Other Authors: Cheng-Ying Chou
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/20639731269786618935

碩士 === 國立臺灣大學 === 生物產業機電工程學研究所 === 104 === Positron emission tomography (PET) is a mature technique of medical diagnosis. If we want to develop the tracer for PET, we should do animal experiment first. It is the reason why we utilized the dual-head small-animal positron emission tomography (DHAPET) system. DHAPET has characteristics of high detection sensitivity and flexible system configurations. However, the system geometry may result in severe parallax errors and undetected events along the trans-axial direction, thus reducing the image quality. With the advancement of detector hardware, time-of-flight (TOF) of photons can be detected, which has been demonstrated to significantly improve image quality, and can greatly benefit its use in research studies and clinics. On the other hand, the conventional attenuation correction requires performing additional transmission scan, which represents more radiation dose. To reconstruct activity distribution and attenuation coefficient simultaneously, the maximum likelihood activity and attenuation estimation (MLAA) was proposed. In this work, we numerically computed the DHAPET system response matrix that includes TOF information and employed the alternating-direction method of multipliers estimation (ADMM) based on total variation (TV)-minimization. By applying the ADMM, the reconstructed images can be anticipated to have improved quality with better spatial resolution. On the other hand, we combined the MLAA with TV for improving the MLAA. Then we compared the ADMM with MLAA-TV, they are convergence after 15 iteration, and the normalized error of activity and attenuation in ADMM are 59% and 34%, and the normalized error of activity and attenuation in MLAA-TV are about 67% and 42%.