碘-131 SPECT平片成像伪影校正算法  

Artifacts correction algorithm for iodine-131 SPECT planar imaging

作　　者：程李 刘帆 高丽蕾 刘辉 刘亚强[1] CHENG Li;LIU Fan;GAO Lilei;LIU Hui;LIU Yaqiang(Department of Engineering Physics,Tsinghua University,Beijing 100084,China;Beijing Novel Medical Equipment Ltd.,Beijing 102206,China)

机构地区：[1]清华大学工程物理系,北京100084 [2]北京永新医疗设备有限公司,北京102206

出　　处：《清华大学学报（自然科学版）》2023年第5期802-810,共9页Journal of Tsinghua University(Science and Technology)

基　　金：核能开发科研项目([2019]1342号);国家重大科研仪器研制项目(81727807);国家重点研发计划项目(2016YFC0105405,2019YFF0302503);核退役科研项目([2018]1521号)。

摘　　要：碘-131单光子发射计算机断层扫描(single photon emission computed tomography,SPECT)平片成像已广泛应用于甲状腺癌的临床诊断和治疗评估中。由于碘-131发射的Gamma光子能量较高,穿透SPECT准直器隔壁的概率较大,易导致最终图像上出现放射状伪影。为解决该问题,该文提出了一种点扩展函数解卷积结合先验正则化的方法,并基于Monte Carlo模拟和临床数据对该方法进行了验证。模拟数据表明该算法具有很好的单调收敛性。当采用127×127的点扩展函数(像素大小2.2 mm×2.2mm),设置正则化参数为0.01时,模拟数据、临床点源数据和人体数据的放射状伪影区域计数值可分别降低至原始值的4%、35%和28%,同时还可以维持背景区域较低的噪声水平。研究结果表明:该文算法可以有效解决碘-131 SPECT平片成像中的放射状伪影问题,从而提高临床诊断精度。[Objective]Iodine-131 SPECT(single photon emission computed tomography)planar imaging has been widely used in the clinical diagnosis and treatment evaluation of thyroid cancer.Because of the high-energy emissions of iodine-131,the photons have a high probability of penetrating the collimator septa of SPECT,causing"spoke"artifacts in the final result.The"spoke"artifacts make it difficult to distinguish accurate concentration regions of iodine-131,and they may obscure lower uptake regions nearby,such as metastatic spread to lymph nodes.In this paper,a deconvolution method based on the point spread function was combined with a priori regularization to suppress the spoke artifacts and to improve the diagnostic accuracy in clinical studies.[Methods]This study is based on the NET632 SPECT system with the corresponding high-energy general purpose collimator.The collected data follow the Poisson distribution,and they consist of two parts,a forward projection of the true activity distribution and the scatter data.The forward projection progress can be well modeled using a shift-invariant PSF(point spread function).An objective function is built based on the aforementioned approximation,and a priori function is introduced to regularize the reconstruction.A monotonic and convergent algorithm is derived to iteratively solve the objective function.In contrast,the conventional deconvolution method regularizes the solution using a total variation term,and the objective function is optimized based on the"one-step-late"algorithm;thus,nonnegativity and convergence can not be guaranteed.The triple-energy window method is employed to estimate scattering data,and PSFs of different sizes are generated based on Monte Carlo simulations.Simulated NEMA torso phantom data are reconstructed with different parameters to validate the monotonicity and convergence of the proposed method.Moreover,the dataset is also used to evaluate the effects of PSF size and regularization strength on reconstruction images.Normalized spoke counts and backgroun

关 键 词：碘-131 单光子发射计算机断层扫描 放射状伪影 解卷积 先验正则化 

分 类 号：R445.6[医药卫生—影像医学与核医学]