Nuclear Medicine Imaging 核 醫 影 像 原 理 與 處 理 Imaging I 蕭 穎 聰 Ing-Tsung Hsiao Department of Medical Imaging and Radiological Sciences Chang-Gung University Tao-Yuan, Taiwan Imaging II Imaging III Imaging System I Imaging System II 1
核 子 醫 學 影 像 什 麼 是 核 子 醫 學 影 像?? 基 本 放 射 物 理 訊 號? Radiation, isotope, density 如 何 偵 測? detecting system (detector, scanner) 如 何 處 理 偵 測 資 料? physical effects correction, reconstruction 如 何 處 理 與 分 析 影 像? segmentation, registration, kinetic model,.. 如 何 利 用 影 像? diagnosis, planning, staging, new drug development 核 子 醫 學 影 像 Planar Imaging 基 本 放 射 物 理 藥 物 注 射 訊 號 偵 測 影 像 重 建 影 像 處 理 分 析 核 醫 藥 物 研 發 偵 測 硬 體 研 發 電 腦 軟 體 處 理 診 斷 治 療 PET Images Tomographic Images MRI SPECT PET 2
Nuclear Medicine Imaging Nuclear Medicine : Basic Physics Tomographic Imaging PET: Basic Physics Hardware detectors, Radiopharmaecuticals Software Image Formation Reconstruction Atomic structure Physics I The Nucleus of An Atom Proton and Neutron Binding energy: MeV Radioactivity ( 放 射 性 ) Radioactive decay 不 穩 定 原 子 核 放 射 出 輻 射 粒 子 或 能 量 (photons,, or gamma rays) 變 成 穩 定 狀 態 包 括 衰 變,, 衰 變,, 放 射 能 量 gamma ( ) ) emission ( 伽 瑪 射 線 or 光 子 ) Nuclear binding force Positron Decay( + 正 子 衰 變 ) Too many protons: P N+ P + + : positive beta particle or positive electron or anti-electron 正 子 與 電 子 發 生 互 毀, 產 生 180 度 相 反 方 向 的 兩 個 光 子 Gamma Emission ( 伽 瑪 射 線 ) Too much energy: energy ( ) gamma ray A A gamma ray is a photon ( 光 子 )(energy). A A gamma ray photon is different from the X-rayX photon only by its energy Excited nucleus 3
能 量 傳 輸 光 電 效 應, 康 普 敦 散 射, 與 成 對 效 應 輻 射 與 物 質 的 作 用 (Non-)Penetrating Radiation Penetrating or not energy Gamma ray and X-rayX are penetrating radiation History 1895: Rontgen X-rays 1896: Bequerel radiation from Uranium 1898: Curies radioactivity, Radium 1913: Georg de Hevesy tracer approach 1923: first study on biologic system 1927: Blumgart and Weiss first human study using tracer 1930s: Lawrence cyclotron 1951: Benedict Cassen: rectilinear scanner 1958: Hal Anger: Anger camera 1960s: major use 131 I 1964: Paul Harper: 99m Tc major turning point for NM 1963: Cormack CT math 1972: Hounsfield CT scanner 1970s: Phelps et al PET; Kuhl et al SPECT 核 醫 影 像 核 醫 影 像 核 醫 影 像 = 藥 物 分 佈 的 情 形 生 理 或 功 能 性 Physiology / Metabolism Planar vs. Tomography Two Modalities: SPECT (Single Photon Emission Computed Tomography) PET (Positron Emission Tomography) Function vs. Anatomy (MRI/CT) Inject Radioactive Tracer Localizes in ROI Emits gamma-rays (photons) Tracer Concentration physiological function 平 面 造 影 Planar Imaging 平 面 造 影 空 間 資 訊 重 疊 了 ==> 需 要 每 一 個 空 間 位 置 的 資 訊 4
核 醫 硬 體 偵 測 系 統 Standard Nuclear Medicine Imaging system Rectilinear Scanner First nuclear medicine images: thyroid 131 I scans (Back to History) 偵 測 系 統 - 伽 瑪 攝 影 機 First gamma camera (1958) 核 醫 硬 體 偵 測 系 統 Standard Nuclear Medicine Imaging system 電 腦 斷 層 掃 瞄 Computed Tomography Tomography cross-sectional imaging Emission Computed Tomography (ECT) Compute cross-sectional tracer distribution Collect data at all angles 1-D projection=>2d sinogram Sinogram -----> cross-sectional distribution where -----> reconstruction t sinogram 5
Sinogram Nuclear Medicine Imaging Two Modalities: 160 1. SPECT: (Single Photon Emission Computed Tomography) Physical Mechanism: 2. PET:(Positron Emission Tomography) Physical Mechanism: 90 45 0 Radio-isotopes 99m 123 201 Tc, I, Tl Radio-isotopes 15 O, 11 C, F 18 Emission Computed Tomography II Simple Illustrations of Cameras Emission Computed Tomography III Example of Real Detectors SPECT Detectors :Picker Irix PET Detectors :GE Advance Whole Body PET SPECT 單 光 子 電 腦 斷 層 掃 瞄 PET 6
Nuclear Medicine Imaging Nuclear Medicine : PET and SPECT Tomographic Imaging PET: Basic Physics Hardware detectors, Radiopharmaecuticals Software Image Formation Reconstruction Clinical Application New Development Positron Detection Coincidence Two Photons detected at the same time (timing circuit) i j Nuclear Medicine Imaging Nuclear Medicine : PET and SPECT Tomographic Imaging PET: Basic Physics Hardware detectors, Radiopharmaecuticals Software Image Formation Reconstruction Clinical Application New Development PET Scanner 正 子 掃 瞄 儀 Block Detectors In PET, block detectors are arranged in rings Nuclear Medicine Imaging Nuclear Medicine : PET and SPECT Tomographic Imaging PET: Basic Physics Hardware detectors, Radiopharmaecuticals Software Image Formation Reconstruction Clinical Application New Development 7
Sinogram Tomographic Reconstruction 2D object sinogram 影 像 重 建 解 Ax=b 的 問 題? Analytical Reconstruction Reconstruct object from projection data g A x b xˆ Tomographic System -1 A Reconstruction The Most popular reconstruction method: FBP: filtered backprojection algorithm Ax b ˆ 1 x A b Iterative algorithm: k ˆ g Statistical Reconstruction Optimization Algorithm System Model Η O Reconstruction Update Parameter ˆ 1 k ( g) log Pr( g ) Criteria? Satisfy Yes arg max ( g)? No *ˆ Done FBP FBP vs. Statistical Reconstruction *ˆ k ˆ 2ˆ 1ˆ Statistical 0ˆ 8
PET Processing Examples Nuclear Medicine Imaging Nuclear Medicine : PET and SPECT Tomographic Imaging PET: Basic Physics Hardware detectors, Radiopharmaecuticals Software Image Formation Reconstruction Clinical Application New Development New Development Dual Modality: PET/CT Function + Anatomy + = + = Function (PET) Anatomy (CT) Dual Modality: PET/CT Thanks Other Dual Modalities SPECT/CT, SPECT/MRI, PET/MRI, Optical Imaging/PET 9
分 子 影 像 :Molecular Imaging PET and SPECT for molecular imaging in living subjects: High sensitivity, full quantitative tomography Animal Imaging MicroPET, MicroSPECT for small animal imaging In Vivo Studies: 18 FDG Mouse Heart 核 醫 影 像 處 理 Weight: 32 g Injection: 0.58 mci Uptake: 120 minutes 核 醫 影 像 處 理 核 醫 影 像 處 理 影 像 融 合 Image processing: max the info from an image using computer Including: Basic processing: edge/contrast enhancement Pre-processing before reconstruction System artifact correction Kinetic analysis (time analysis) 3D visualization Image Fusion with other modalities PACS.. 10
核 醫 影 像 處 理 藥 物 動 力 學 FIG. 3. Distribution of FDG in cross section (OM + 8 cm ) of normal human brain at various times following intravenous injection of FDG bolus. Distributions were measured and reconstructed with ECAT. At early times, F-DOPA PETdistribution dynamic reflects image boththru LCRMGlc the same and slice cerebral blood flow (CBF), with effects of CBF gradually diminishing with time. After 20 min, distribution becomes stable. Photographic gray scales in these distributions of different times are not normalized to a common reference. Although, relative distribution in brain remains stable, absolute amount of FDG dose change slowly as shown in Fig. 4. Distributions shown are selected from a total of 14-30 distributions obtained for each study. 核 醫 影 像 處 理 其 他 影 像 分 割 影 像 參 數 最 佳 化 影 像 ( 系 統 ) 品 質 評 估 什 麼 是 核 子 醫 學 影 像?? 11