肝单光子发射计算机断层若干物理因素的讨论

我们于1985年对我院1984年开展肝单光子发射计算机断层以来的52例肝病人进行了分析总结。结果表明,肝单光子发射断层在诊断肝内占位性病变方面比普通肝静态γ照相有许多优点。需要指出的是,肝单光予发射断层的若干优点及诊断的准确性是与物理条件的正确选择和应用密切相关的。本文根据至今积累的近100例断层经验,从技术方面介绍了影响单     

Parameter estimation in Bayesian reconstruction of SPECT images: An aid in nuclear medicine diagnosis

Despite the adequacy of Bayesian methods to reconstruct nuclear medicine SPECT (single‐photon emission computed tomography) images, they are rarely used in everyday medical practice. This is primarily because of their computational cost and the need to appropriately select the prior model hyperparameters. We propose a simple procedure for the estimation of these hyperparameters and the reconstruction of the original image and test the procedure on both synthetic and real SPECT images. The experimental results demonstrate that the proposed hyperparameter estimation method produces satisfactory reconstructions. Although we have used generalized Gaussian Markov random fields (GGMRF) as prior models, the proposed estimation method can be applied to any priors with convex potential and tractable partition function with respect to the scale hyperparameter. © 2004 Wiley Periodicals, Inc. Int J Imaging Syst Technol 14, 21–27, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20003     

A pilot study on ^99mTc-3PRGD2 scintigraphy in diagnosis of brain glioma

The ^99mTc-3PRGD₂ targeted SPECT/CT scanning was of significance in detecting differentiated glioma.In this work,the diagnostic value of ^99mTc-3PRGD₂ scintigraphy in brain glioma was evaluated by the ten clinically verified brain glioma patients after obtaining informed consent.The patients first accepted X-ray imaging to localize the detecting regions before administrating with ^99mTc-3PRGD₂ at a mean radioactivity of 849±115 MBq via single intravenous bolus injection 2 h prior to SPECT/CT imaging.Tumor samples for detectingαvβ3 were collected by surgical operations two weeks after the scintigraphy.The results of CT and SPECT scanning were merged and compared.The correlation between tumor occupation（T/N ratio） andαvβ3 expression level were analyzed.The T/N ratios in brain glioma were proportionally correlated to av(33 positive cell percentage（R²=0.9253,p<0.05）.This study primarily evaluated the clinical application of ^99mTc-3PRGD₂ SPECT scintigraphy on brain glioma.The more pathological types and detecting strategies covering a large amount of samples would aid to clarify the potentials.     

Antibody-Based Tracers for PET/SPECT Imaging of Chronic Inflammatory Diseases

Chronic inflammatory diseases are often progressive, resulting not only in physical damage to patients but also social and economic burdens, making early diagnosis of them critical. Nuclear medicine techniques can enhance the detection of inflammation by providing functional as well as anatomical information when combined with other modalities such as magnetic resonance imaging, computed tomography or ultrasonography. Although small molecules and peptides were mainly used for the treatment and imaging of chronic inflammatory diseases in the past, antibodies and their fragments have also been emerging for chronic inflammatory diseases as they show high specificity to their targets and can have various biological half-lives depending on how they are engineered. In addition, imaging with antibodies or their fragments can visualize the in vivo biodistribution of the probes or help monitor therapeutic responses, thereby providing physicians with a greater understanding of drug behavior in vivo and another means of monitoring their patients. In this review, we introduce various targets and radiolabeled antibody-based probes for the molecular imaging of chronic inflammatory diseases in preclinical and clinical studies. Targets can be classified into three different categories: 1) cell-adhesion molecules, 2) surface markers on immune cells, and 3) cytokines or enzymes. The limitations and future directions of using radiolabeled antibodies for imaging inflammatory diseases are also discussed.     

减小模板状NaI(Tl)探测器的边缘死区

用在环状ＳＰＥＣＴ系统中的ＮａＩ（Ｔｌ）探测器模板存在着严重的边缘死区。介绍了一些减少该死区的办法,包括：一个ＰＭＴ管跨接两个探测器模板,在边缘刻槽等等。实验结果证明通过这些处理,这个死区可以减小到５ｍｍ。     

断层屏蔽SPECT成像法探讨

本文以空间积分原理为基础,以逐渐逼近法为图像重建的核心,探讨了可实现断层屏蔽的SPECT成像的途径.与传统的SPECT成像方法比较,它具有高的灵敏度和数据获取速度快的特点.由于无须用机械装置将γ照相机旋转,消除了运动带来的误差,提高了成像的质量.本文用线性方程组的松弛解法对无散射和无噪音的二维空间的模拟数据进行了验算,证明逐渐逼近法能逐渐逼近到放射性分布区域,并能基本给出分布形式.     

基于改进U-Net的SPECT骨显像病灶分割研究北大核心CSCD

在核医学中,单光子发射计算机断层(single-photon emission computed tomograpy,SPECT)骨显像是辅助医师诊断癌症的重要手段。针对骨显像图像信噪比低、边界模糊、病灶小难以提取和人工勾画病灶耗时等问题,提出一种基于改进U-Net网络的骨显像病灶自动分割算法。该算法在U-Net的原卷积块基础上,采用了多尺度密集连接(multi-scale dense connection,MDC)的方式来提高对小病灶特征的提取能力,同时解决了网络加深后出现的梯度消失问题。其次,为提取病灶的细节特征,在密集连接和跳跃连接处引入了注意力机制结构。最后,针对使用小样本数据集,模型难以收敛的问题,采用迁移学习的方法,优化了模型的初始参数,提升模型的泛化能力和分割效率。此外,为了降低计算量、进一步提高分割效果,对数据集进行了裁剪和去噪。同时,将处理后的图像采用旋转、镜像等方法进行了数据扩充。实验结果表明,改进的U-Net的识别精确率(precision)、平均交并比(mean intersection-over-union,mIoU)分别能达到0.7352、0.4673,效果优于目前主流的分割算法,具有一定实际应用价值。     

基于改进CPD算法的SPECT-B超甲状腺图像配准

为了获得更多甲状腺肿瘤的诊断信息,文章提出了一种基于改进CPD算法的甲状腺肿瘤的SPECT图像和B超图像自动配准方法。首先,将参考图像(SPECT图像)和待配准图像(B超图像)分别通过阈值分割和图割的方法提取轮廓特征点;然后,用遗传算法和粒子群算法相结合的优化算法对CPD的权重参数进行自动寻优,利用改进的CPD算法对提取出的两组特征点进行匹配,得到两幅图像的空间变换参数;最后,将待配准图像按所求得的变换参数旋转、平移,从而获得配准后图像。实验结果表明,该方法能实现SPECT与B超甲状腺肿瘤图像的良好配准,具有参数少、精度高、鲁棒性好等特点。     

SPECT心肌灌注断层显像左心室的自动提取

通过分析ＳＰＥＣＴ心肌灌注断层图象的象素之几何分布,利用最小二乘法拟合心肌左心室的半球加圆柱模型,采用迭代算法去除非左心室组织显影,实现左心室的自动提取。该技术为进一步定量分析提供了基础。     

SPECT心血池显像评价阿霉素心肌毒性的价值

选择４９例非何杰金淋巴瘤和小细胞肺癌等患者，采用常规ＣＨＯＰ和ＣＡＶ方案进行的治疗，定期用ＳＰＥＣＴ检测患者左心功能，评价阿霉素（ＡＤＭ）对心肌的毒性作用，结果表明，化疗前后ＥＦ（射血分数）ＰＥＲ（高峰射血率）和ＰＦＲ（高峰充盈率）值比较，差别有显著性（Ｐ〈０．０５），体内的ＡＤＭ累积量愈大，ＥＦ，ＰＥＲ和ＰＦＲ值下降愈大，并以ＰＦＲ变化最敏感，提示ＳＰＥＣＴ心功能测定是评价患者ＡＤＭ心肌毒性的每