完整PETCT基本原理和应用.ppt

1. 外置棒源 68 Ge 的衰减校正 —— 正电子显像 的标准衰减校正方法 2. X-CT 衰减校正 Outline ? Overview 功能与解剖成像 ? PET 系统的发展历史 ? PET 物理学基础 符合探测 “混合”事件 分辨率和噪声 衰减校正 ? PET 主机的组成和工作原理 ? 计算机图象处理 ? 质量控制 ? 整套 PET 系统包括 PET 主机和回旋加速器及配套的化学 合成装置三大部分。 ? PET 主机配置有扫描机架、主机柜、检查床、主辅工 作站等几个部分。 ? 机架是最大部分，其中最主要的是探头部分，包括探 测器环和中隔、多晶体、光电倍增管、前置电子线路、 符合线路、分类器、电子准直线路、透射源及各种电 子学仪器线路等。 Detector Requirements Goal Requirement High Spatial Resolution Small Detector Elements High Sensitivity High Stopping Power Low Scatter Fraction Good Energy Resolution Low Randoms Good Timing Resolution Low Deadtime Fast Event Handling Small Channel Size Limited Multiplexing Low Cost None of the Above Detector Materials ? High Density – Overall detection efficiency is proportional to the product of the detection efficiencies ? High Effective Atomic Number – High photopeak fraction (photopeak vs Compton) allows high discriminator setting for scatter rejection ? Fast Decay Time – The primary speed of the detector has a big effect on count rate ? Others – light output, wavelength, and index of refraction are other properties that are important Detector Materials NaI(Tl) BGO GSO(Ce) LSO(Ce) m (cm -1 ) 0.37 0.95 0.67 0.89 Photonfraction ~15% ~40% ~35% ~30% Light Output 100 20-25 35 75 Decay Constant 230 300 65 50 Radioactive NO NO NO YES Melting Point 650 1050 2000 2000 Furnace Platinum Iridium Iridium Cost $5/cc $10/cc $20/cc $25/cc ?? Detector Assemblies 1-to-1 Coupling Excellent livetime characteristics, but expensive, and limited in size to smallest available PMT (~1cm 2 ). Block Detector Individual crystals “pipe” light to detectors. More complex, but required with low light output--BGO. An