PET/CT在肿瘤学中的应用

PET/CT技术迅速发展,很快成为医学影像诊断,特别是肿瘤诊断和研究的热点。通过将PET与CT两种技术整合到同一检查设备上,将不同性质的图像进行同机融合和比较分析,PET/CT实现对病变的解剖形态显示与功能代谢显示的互补结合。PET与CT的结合,提高对肿瘤病灶的定位和定性诊断的准确性,往往因此而改变对患者的诊疗决策。这一技术的进步不仅使得核医学领域充满活力,也引起放射医学界的极大兴趣。本文概述PET和PET/CT在肿瘤学方面的应用现状,分析PET/CT的优势与不足,并对这一技术未来的发展趋势进行展望。     

多功能ECT/CT复合成像系统

随着多种医学影像技术的不断发展,需要直观、准确地综合各种影像技术所提供的信息,于是图像融合技术成了本世纪医学影像学的主题之一。多功能ECT/CT复合成像系统将单光子发射计算机断层显像(SPECT)、分子符合检测(MCD)和CT融于同一套设备,一机多能,同时解决了功能和解剖图像融合、匹配和对位等难题,在临床实践中必将有广泛的应用前景。     

PET采集处理方法对病灶检出能力和图像质量的影响

为明确采集模式、衰减校正方式及重建方法对正电子发射断层显像(PET)的病变检出能力和图像质量的影响,利用一桶状模型进行测试研究。模型内含9个阳性柱(直径4.3~37.8mm)、7个阴性柱(直径5.9~22.3mm)和7个阴性球(直径5.8~22.0mm)。研究发现,3D采集在轴向中心的检出能力相当于2~4倍时间的2D采集,但在轴向两端的图像质量明显降低,2D采集图像的对比度和清晰度更佳。带有约20MBq/L的放射性采集衰减校正图对相应区域的密度低估约3%。分割法处理可显著提高衰减校正图的均匀性,但会降低边界的清晰度。OSEM法和FBP法重建的图像对病灶的检出能力相当,前者条状噪音少、更均匀,而后者对比度更佳。PET检查时宜根据具体情况及实际需要权衡选择采集和处理方法。     

正电子发射断层显像

正电子发射断层显像(PET)是当代影像学的尖端技术。在医学影像诊断从形态向功能、从大体解剖向分子生化显示的发展趋势中起着越来越重要的作用。利用正负电子“湮没”所发出的成对光子的符合检测以及同位素示踪原理,PET能够在体外无创地“观察到”活体内的生理的和病理的生化过程,这对于研究生命现象的本质和各种疾病发生、发展的机理非常有用。在临床上,特别适用于在没有形态学改变之前,早期诊断疾病、发现亚临床病变以及早期、准确地评价治疗效果等。PET具有广阔的应用前景,其临床有效性将是这一技术发展的基础。在可预期的将来,PET的功能显像将和CT、核磁等形态学检查结合起来,为广大患者服务。     

PET/CT配置的可行性分析

目的 探讨PET/CT配置的可行性。方法 在分析PET/CT的技术先进性和配置必要性的基础上,参考《广东省乙类大型医用设备配置技术评估标准》《三级综合医院评审标准》有关要求,从配置PET/CT所需满足的准入条件、配套设施、人员要求、社会效益、经济效益进行具体分析。结果 从软硬件情况、效益情况及配置许可审批情况证明引进PET/CT的可行性。结论 PET/CT的引入必须充分论证可行性,同时要加强相关科室的协作,才能有效发挥PET/CT在临床、学科和科研上的作用。     

BIOGRAPH 64型PET/CT与ECAT EXACT HR+型PET的性能比较

通过模型研究和临床病例分析,比较Biograph 64型PET/CT和Ecat Exact HR+型PET仪,并从病灶检出能力、图像质量、患者检查的方便性和工作人员操作的友好性等多个角度,对新型的Biograph 64 PET/CT的主要性能进行评价。     

基于不同子集的OS-EM快速迭代重建算法研究

有序子集最大期望值方法(Ordered Subsets Expectation Maximization,OS-EM）具有较高的重建图像质量和较短的计算时间，正逐步应用在正电子发射断层扫描仪（Position Emission Tomography,PET）图像重建过程中。通过研究仿真Phantom模型在不同划分子集下的重建结果，分析比较了不同子集的选取对重建图像质量以及重建收敛速度的影响。     

正电子发射断层延迟显像在腹部和盆腔的应用

为明确正电子发射断层(PET)延迟显像对常规显像发现的腹部或盆腔可疑病灶的进一步诊断价值,对70例患者在注射18F-脱氧葡萄糖后约3h进行延迟显像,期间通过饮水、进食、排尿或排便等改变胃肠道及泌尿系统的生理状态。通过病理诊断或临床随访,33例诊为恶性肿瘤,37例为生理性摄取或良性病变。以延迟显像中病灶的标准摄取值降低或升高超过10%诊断良性或恶性,则灵敏度、特异性、准确性、阳性预测值和阴性预测值分别为51%(17/33)、62%(23/37)、57%(40/70)、81%(17/21)和85%(23/27)。故PET延迟显像对腹部和盆腔病变具有一定的鉴别诊断价值。但须注意子宫、卵巢生理性摄取可导致假阳性,而胃癌在进食撑开胃部后摄取可能会减低。     

全身肿瘤扫描:MRI弥散加权成像和PET技术的比较

继正电子放射断层(PET)技术之后,磁共振(MRI)全身弥散加权成像(WB-DWI)正逐渐成为临床上又一项重要的评估全身肿瘤的影像技术。本文将WB-DWI与较为成熟的PET全身扫描技术进行比较,综述WB-DWI在肿瘤学中的初步应用,特别是在肿瘤的诊断、鉴别诊断、分期、预后、疗效监测及筛查等方面的价值。     

一体式定位像和分段式定位像配合CARE Dose 4D技术控制PET检查者辐射剂量的比较

目的 :比较同一患者采用一体式定位像和分段式定位像采集方式结合自动管电流调节技术(combined application reduce exposure,CARE)Dose 4D检查所受到的辐射剂量,确定更优化的采集方式,指导临床进一步降低患者所受辐射剂量。方法 :选取2018年7月至2018年12月在我院PET/CT中心复查的患者20例。患者首次检查采用一体式定位像指导采集(双上肢上举贴近耳侧,采集前后位定位像,长度颅顶至股骨中段)。复查采用分段式定位像指导采集(双上肢上举贴近耳侧,采集前后位定位像,长度额窦至股骨中段+双上肢置于躯干两侧,采集前后位定位像,长度颅顶至下颌)。以CT容积剂量指数(volume CT dose index,CTDIvol)和剂量长度乘积(doselength product,DLP)作为辐射剂量评价指标,比较两种采集方式所受辐射剂量的差异。结果 :分段定位像法平均CT容积剂量指数为(54.09±5.82)mGy,平均剂量长度乘积为(1365.34±118.55)mGy·cm;一体式定位像法患者容积CT剂量指数为(91.52±9.65)mGy,剂量长度乘积为(2130.17±224.42)mGy·cm。CTDIvol和DLP指标差异均有统计学意义,P <0.01。结论 :分段式定位像配合CARE Dos4D技术能有效降低PET/CT全身检查者的CT辐射剂量。     

Positron emission tomography—a new technique for studies of the central nervous system

Positron emission tomography (PET) has become an important tool to study the central nervous system. Examples of such studies are cerebral blood flow and metabolism and determination of receptor characteristics of the brain. In the following the basic principles and the physics behind PET are given. Different aspects are discussed such as detector design, image reconstructions and data analyses. Since quantification is essential in PET, data have to be corrected for absorption, scatter and random coincidences. These corrections and their influence on image data are discussed. A review of state-of-the-art PET research of the brain is given.     

3-D reconstruction of the atomic positions in a simulated gold nanocrystal based on discrete tomography: prospects of atomic resolution electron tomography

A novel reconstruction procedure is proposed to achieve atomic resolution in electron tomography. The method exploits the fact that crystals are discrete assemblies of atoms (atomicity). This constraint enables us to obtain a three-dimensional (3-D) reconstruction of test structures from less than 10 projections even in the presence of noise and defects. Phase contrast transmission electron microscopy (TEM) images of a gold nanocrystal were simulated in six different zone axes. The discrete number of atoms in every column is determined by application of the channelling theory to reconstructed electron exit waves. The procedure is experimentally validated by experiments with gold samples. Our results show that discrete tomography recovers the shape of the particle as well as the position of its 309 atoms from only three projections.

Experiments on a nanocrystal that contains several missing atoms, both on the surface and in the core of the nanocrystal, while considering a high noise level in each simulated image were performed to prove the stability of the approach to reconstruct defects. The algorithm is well capable of handling structural defects in a highly noisy environment, even if this causes atom count “errors” in the projection data.     

Nonray‐tracing determination of the 3D refractive index profile of polymeric fibres using single‐frame computed tomography and digital holographic interferometric technique

In this paper, we present a nonray‐tracing technique for evaluating the three dimensional distribution of the refractive index values inside polymeric fibres. This technique, named ‘single‐frame computed‐tomography (SFCT)’, is applied to digital holography. A comparative study between the calculated optical phase values using ordinary tomography and SFCT is carried out, and a negligible deviation is detected. The proposed technique is used to determine the three‐dimensional refractive index profile of isotactic Polypropylene fibres, IPP. The variation of the optical properties is measured before, during and after the formation of the necking phenomenon. In addition, SFCT technique is applied to the online determination of the change of the optical properties of IPP fibres. Holograms are given for illustration.     

Infrared tomography: data distribution system and software development for real-time velocity measurement

The data distribution system of this project is divided into two types, which are a Two-PC Image Reconstruction System and a Two-PC Velocity Measurement System. Each data distribution system is investigated to see whether the results' refreshing rate of the corresponding measurement can be greater than the rate obtained by using a single computer in the same measurement system for each application. Each system has its own flow control protocol for controlling how data is distributed within the system in order to speed up the data processing time. This can be done if two PCs work in parallel. The challenge of this project is to define the data flow process and critical timing during data packaging, transferring and extracting in between PCs. If a single computer is used as a data processing unit, a longer time is needed to produce a measurement result. This insufficient real-time result will cause problems in a feedback control process when applying the system in industrial plants. To increase the refreshing rate of the measurement result, an investigation on a data distribution system is performed to replace the existing data processing unit.     

Comparative proteomics analysis of human pituitary adenomas: current status and future perspectives

This article will review the published research on the elucidation of the mechanisms of pituitary adenoma formation. Mass spectrometry (MS) plays a key role in those studies. Comparative proteomics has been used with the long-term goal to locate, detect, and characterize the differentially expressed proteins (DEPs) in human pituitary adenomas; to identify tumor-related and -specific biomarkers; and to clarify the basic molecular mechanisms of pituitary adenoma formation. The methodology used for comparative proteomics, the current status of human pituitary proteomics studies, and future perspectives are reviewed. The methodologies that are used in comparative proteomics studies of human pituitary adenomas are readily exportable to other different areas of cancer research.