PET—CT的显像原理及临床应用

目的：介绍PET—CT的显像原理及临床应用。方法：分析PET—CT的显像原理。结果：PET以解剖影像的形式及其相应的生理参数，显示靶器官或病变组织的状况，高档CT技术进行精确定位，精确提供靶器官的解剖和功能双重信息。结论：PET-CT实现了PET和CT的同机融合，形成两种技术的优势互补，具有较高的临床应用价值。     

Combined imaging modalities: PET/CT and SPECT/CT

The recent development of new radiopharmaceuticals now permits molecular imaging of biologic processes at the cellular level to improve both the diagnosis and treatment of disease. Fused PET/CT and SPECT/CT imaging systems now provide metabolic and functional information from PET or SPECT combined with the high spatial resolution and anatomic information of CT. Because the two sets of images are fused, areas of normal and abnormal metabolic activity can be mapped to recognizable anatomic structures. This fusion of function and anatomy has quickly demonstrated its clinical value, especially in the field of oncology. There are also growing clinical indications in the areas of cardiology, neurology, and imaging of infection. F-18 fluorodeoxyglucose (FDG) is the PET imaging agent currently in most common use. While FDG uptake is nonspecific, it has demonstrated important applications, especially for patients with cancer. Continued progress in fused anatomic and molecular imaging can be anticipated, both in the development of more advanced instrumentation (integrated CT or MRI with PET and SPECT camera technology) and with new radiopharmaceuticals that image more specific physiologic aspects of organ and cell biology.     

The place of positron-emission tomography in contemporary patient care

Positron emission tomography (PET) is a unique method offering physicians unrivaled access to in vivo quantitative measurements. The PET studies are useful in many areas of establishing primary diagnosis, differential diagnosis, planning and monitoring therapeutical efficacy. As a clinical tool it has been shown to increase diagnostic accuracy. Unlike anatomical imaging modalities, such as CT and MR, PET permits assessment of chemical and physiological changes related to any function. PET images demonstrate pathological change long before they would be revealed by other imaging modalities like CT and MR. It produces images of molecular level of physiological function which can be used to measure many vital processes, including glucose metabolism, blood flow and perfusion, receptorligand binding rates, and oxygen utilization. The PET studies provide useful diagnostic information which may alter patient management and reduce the total cost of patient care. PET studies have made critical contributions to more cost-effective patient management in four clinical disciplines: cardiology, neurology, psychiatry and oncology. Recently, the clinical indications for PET have increased dramatically. Since Hungary's first PET center has been established at the University Medical School in Debrecen many studies additionally demonstrate that PET reduces overall cost of medical care, because it increases the certainty of diagnosis and clinical stage of disease, and therefore eliminates the expense of unnecessary testing or treatment.     

Operational radiation safety for PET-CT, SPECT-CT, and cyclotron facilities

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are well- established and indispensable imaging modalities in modern medicine. State-of-the-art computed tomography (CT) scanners have now been integrated into multi-modality PET-CT and SPECT-CT devices, and these devices, particularly PET-CT scanners, are dramatically impacting clinical practice. 18F-fluorodeoxyglucose (FDG), by far the most widely used radiopharmaceutical for clinical PET imaging in general and oncologic PET imaging in particular, is highly accurate in detecting (approximately 90%) and staging many types of tumors, monitoring therapy response, and differentiating benign from malignant lesions. Several factors, including the relatively high administered activities [e.g., 370-740 MBq (10-20 mCi) of FDG], the high patient throughput (up to 30 patients per d), and in particular, the uniquely high energies (for a diagnostic setting) of the 511-keV positron-negatron annihilation photons, make shielding requirements, workflow, and other radiation protection issues important considerations in the design of a PET or PET-CT facility. The Report of Task Group 108 of the American Association of Physicists in Medicine (AAPM) provides a comprehensive summary of shielding design and related considerations, along with illustrative calculations. Whether in the form of a PET-CT or a SPECT-CT device, the introduction of CT scanners into a nuclear medicine setting has created new and complex radiation protection issues concerning the radiation burden and attendant risks accrued by patients undergoing such multi-modality procedures (especially in those instances in which higher-dose, diagnostic-quality CT studies are done as part of the PET-CT or SPECT-CT exam). In addition, because PET is dependent on the availability of short-lived 18F (Tp = 110 min) primarily in the form of FDG, and other short-lived positron emitters such as 11C (20 min), 13N (10 min), and 15O (2 min), cyclotrons for production of medically applied radionuclides and associated radiochemistry facilities are now widespread (well over 100 worldwide) and present their own radiation safety issues. In addition to the radioactive product, sources of exposure include neutrons and radioactive activation products in the various cyclotron components and surrounding shielding. Nonetheless, published studies have shown that the radiation doses to personnel working in cyclotron and associated radiochemistry facilities, as well as in PET or PET-CT and SPECT or SPECT-CT facilities, can be maintained below, and generally well below, the pertinent regulatory limits. This presentation will review the basic radiation safety aspects, including shielding and workflow, of these increasingly important and increasingly numerous facilities. The radiation burden accrued by the patients undergoing PET-CT or SPECT-CT exams will be considered as well.     

The value of PET-CT imaging in malignant tumours of the head and neck

Imaging with fluor-18-deoxyglucose(FDG)-positron-emission tomography (PET) and CT combined in a single machine is a recent development. Using this technique both molecular and anatomical information are acquired. This results in an increased sensitivity and specificity in comparison to PET and CT as a single modality. One of the main advantages is that interpretation of PET images can be related to the anatomical information which helps to delineate the size and extent of a tumour as well as its relationship with surrounding tissues. It is also useful in planning surgical treatment and irradiation. At restaging PET-CT delineates the site and extent of a recurrence in the complex anatomy of the head and neck region and helps to define the location of a biopsy. This is particularly valuable in the anatomically complex head and neck region. Whole-body imaging can detect distant metastases and second primary tumours. PET-CT has the potential to become a part of the staging procedure of the primary tumour and also the follow-up in patients who have been treated for head and neck cancer.     

Display of positron emission tomography with Cadplan

Recent clinical experience at Peter MacCallum Cancer Institute (PMCI) with the use of unregistered Positron Emission Tomography (PET) images for radiotherapy target marking in the lung suggests that co-registered PET images would be invaluable. PMCI has three radiotherapy treatment planning systems but none of them currently is able to display or co-register PET images with Computed Tomography (CT) images. This paper details the approach taken to display co-registered PET images with the CADPLAN treatment planning system. CT Image files are normally transferred to Cadplan by DICOM transfer, but the Cadplan DICOM server will not receive (has no presentation context for) PET images. The fundamental design of the CADPLAN system envisages display of only a single image dataset, which must be a CT scan for planning reasons. The problem of data transfer is crudely solved by File Transfer Protocol (FTP) over the network. Fortunately the multislice format of the PET image files makes individual transfer manageable. A menu based C program running at the same time as Cadplan is invoked to sample the DICOM PET Image and create multiple Cadplan CART image format files that are co-registered with each existing transverse CT slice. With the Cadplan in contour mode, the program allows the co-registered PET images to be swapped in and out of the image section of the CART files promptly, while keeping the contour information. This allows radiotherapy target volumes to be marked using transverse PET emission images, and effectively circumvents the design constraints prohibiting the display of more than one image set. Contours can be over-laid for review on reconstructed sagittal or coronal views of CT or PET images constructed using the standard Cadplan tools. Co-registration is facilitated by identical positioning with the aid of lasers and FDG loaded fiducial markers on the PET scanner and CT couch. A polyurethane cast fixed with EFFILOCK is used to ensure identical patient orientation on the CT and PET couches. Since both imaging modalities are without significant geometric distortion the co-registration is then simply a translation. PET transmission images can be used for co-registration verification. The practical implementation of display of PET images with CADPLAN has enabled us to begin a trial of 10 patients, the results of which will be reported separately.     

18F-FDGPET-CT显像在头颈部肿瘤的临床诊断中的效果研究

目的评价18F-FDGPET-CT对头颈部肿瘤患者的临床诊断价值。方法患者均行18F-FDGPET-CT显像,对图像进行分析。结果 PET/CT的总检出率高于PET和CT,PET/CT的定位准确率高于PET。结论 18F-FDGPET-CT能够有效地鉴别头颈部肿瘤治疗后瘢痕与肿瘤复发、淋巴结及远处脏器转移,可提高对其诊断的敏感性和准确性。     

Validating an image segmentation program devised for staging lymphoma

Hybrid positron emission tomography–computed tomography (PET–CT) imaging systems are an important tool for assessing the progression of lymphoma. PET–CT systems offer the ability to quantitatively assess lymphocytic bone involvement throughout the body. There is no standard methodology for staging lymphoma patients using PET–CT images. Automatic image segmentation algorithms could offer medical specialists a means to evaluate bone involvement from PET–CT images in a consistent manner. To devise and validate an image segmentation program that may assist staging lymphoma by determining the degree of bone involvement based from PET–CT studies. A custom-made program was developed to segment regions-of-interest from images by utilising an enhanced fuzzy clustering technique that incorporates spatial information. The program was subsequently tested on digital and physical phantoms using four different performance metrics before being employed to extract the bony regions of clinical PET–CT images acquired from 248 patients staged for lymphoma. The algorithm was satisfactorily able to delineate regions-of-interest within all phantoms. When applied to the clinical PET–CT images, the algorithm was capable of accurately segmenting bony regions in less than half of the subjects (n?=?103). The performance of the algorithm was adversely affected by the presence of oral contrast, metal implants and the poor image quality afforded by low dose CT images in general. Significant changes are necessary before the algorithm can be employed clinically in an unsupervised fashion. However, with further work performed, the algorithm could potentially prove useful for medical specialists staging lymphoma in the future.     

PET-CT工作原理及应用

目的:PET-CT实现了同机图像融合,是一种功能性医学影像学设备,通过了解其工作原理,掌握设备的日常维护方法,为医学研究和临床诊断提供便利。方法:分别介绍PET与CT两种设备同机组合的不同成像原理以及设备应用时对环境的要求。结果:了解PET-CT的工作原理,掌握一般维护保养项目和方法,使PET-CT融合影像为临床正确确定放疗的计划靶区、检测治疗过程中的疗效提供最佳方案。结论:PET-CT设备的工作状态是否良好与设备的维护保养密不可分。在设备的日常维护过程中要保持设备符合环境要求,工程技术人员必须熟悉设备的各个运行环节,保证设备的正常运转。     

PET/CT的技术性能及临床应用

目的：介PET／CT的性能特点及临床应用。方法：对PET／CT的技术性能进行了分析，并对其发展趋势进行了展望。结果：PET能从分子水平上反映人体组织的生理、病理、生化、代谢改变；多排螺旋CT则可显示机体精细的解剖结构。结论：PET／CT可实现PET图像和CT图像的同机融合，形成2种技术的优势互补，具有极高的诊断性能和临床应用价值。     

PET／CT在肿瘤放射治疗中的应用

本文简要介绍了PET/CT在临床放射治疗计划设计中的应用,PET/CT是临床放射治疗生物靶区的重要工具,为放射治疗从物理调强到生物调强奠定了基础,现将PET/CT在临床模拟定位的应用作一介绍.     

PET/MRI显像技术与其他分子影像技术的比较

目的：比较双模态PET/MRI显像技术与其他分子影像技术的优势和劣势。方法：随着分子医学及影像医学的飞速发展,将二者结合的分子影像技术促进了医学科学的发展。单模态及多模态分子影像技术主要包括了PET/MRI、光学成像、PET/CT、SPECT/CT、SPECT/MRI及超声分子成像。本文比较了以上各种分子影像技术在临床前及临床医学中的应用。结果：双模态PET/MRI优势主要集中在肿瘤学、心脏病学、神经科学中的研究,为研究者及临床医生提供更多的分子信息。结论：多模态分子医学影像设备的发展势必推动整个医学科学的发展,PET/MRI将解开更多的未解之谜。     

PET-CT在肺癌诊断与临床分期中的应用

目的：探讨^18F-脱氧葡萄糖正电子发射显像／电子计算机断层扫成像（^18F-FDG PET-CT）在肺癌诊断及其在临床分期方面的价值。方法：75例患者进行了PET-CT检查诊断为肺癌,分析其PET-CT代谢情况与影像学检查结果（薄层增强CT和HIKCT检查结果）进行对照分析。结果：75例患者通过^18F-FDGPET-CT检查,均诊断为肺癌,其中经纤维支气管检查或者穿刺检查有明确病理的49例,经术后病理证实的23例;^18F-FDGPET-CT75例均表现为放射性摄取异常增高,最大SUV值在1．5-18．8之间;30例CT增强扫描病例中,病灶边缘毛糙,明显强化,CT值升高在20-46Hu之间;45例HRCT检查中病灶有明显分叶、毛刺征、血管集束征、胸膜凹陷征及支气管截断现象等。结论：^18F-FDGPET-CT与诊断性CT联合应用,可以对肺癌进行明确诊断与分期。     

The clinical application of PET/CT: a contemporary review

The combination of positron emission tomography (PET) scanners and x-ray computed tomography (CT) scanners into a single PET/CT scanner has resulted in significant improvements in the diagnosis and staging of disease, particularly in the field of oncology. A decade on from the publication of the details of the first PET/CT scanner, we review the technology and applications of the modality. We examine the design aspects of combining two different imaging types into a single scanner, and the artefacts produced such as attenuation correction, motion and CT truncation artefacts. The article also provides a discussion and literature review of the applications of PET/CT to date, covering detection of tumours, radiotherapy treatment planning, patient management, and applications external to the field of oncology.     

Current developments in SPECT/CT systems using 99mTc-radiopharmaceuticals

The 3 foundations of nuclear medicine are radiation conscious personnel, specific radiopharmaceuticals and equipment. The trend in molecular radiopharmacy is to develop new radiopharmaceuticals targeting peptides and receptors. 99mTc-radiopharmaceuticals give important clinical and molecular information especially in endocrinology, oncology and cardiology. The basic equipment has relied on crystal scintillation detector gamma cameras and the obtained images represent organ function provided by the specific radiopharmaceutical. Gamma cameras for single emission computed tomography (SPECT) can be added to an X-ray computed tomography (CT) equipment to form a hybrid (SPECT/ CT). The system is coupled to computer algorithms and special software to acquire and process the separate studies and fuse the two images to give a 3-D image of organ function plus anatomy. The new semiconductor or solid state detectors are a big improvement in commercial hybrid scintillation cameras and micro-SPECT/CT. Fused images obtained with SPECT/CT have been very useful in almost all medical areas and play an important role in preclinical research. The aim of this work is to present the current status and future trends of SPECT/CT systems in the clinical practice of nuclear medicine using technetium-99m radiopharmaceuticals. The development of molecular, functional and genetic imaging tools aided by new technology and SPECT/CT image fusion will enhance accurate diagnoses, and understanding of molecular mechanisms of disease and their respective response to radiopharmaceutical therapy.     

18F-FDG和18F-FET PET-CT检查致受检者辐射剂量研究

目的 估算接受¹⁸F-FDG(¹⁸F-2-deoxy-D-glucose)和¹⁸F-FET(O-2-¹⁸F-fluoroethyl-L-tyrosine)PET-CT全身检查受检者的有效剂量和器官剂量。方法 使用两种PET-CT扫描协议进行全身显像。PET部分的有效剂量和器官剂量利用基于医学内照射剂量(Medical Internal Radiation Dose, MIRD)计算模式的计算程序IDAC 2.1进行计算,CT部分的有效剂量和器官剂量利用VirtualDose软件计算,PET和CT剂量之和为受检者总的有效剂量。结果 在常规PET-CT扫描中,男性受检者受¹⁸F-FDG辐射所致的有效剂量为(4.81 ±1.04) mSv,女性受检者为(6.09 ±0.73) mSv;男性受检者受¹⁸F-FET辐射所致的有效剂量为(2.67 ±0.38) mSv,女性受检者为(3.21 ±0.38) mSv;CT部分男性受检者的有效剂量为(5.63 ±0.32) mSv,女性受检者为(5.51 ±0.29) mSv。¹⁸F-FDG PET-CT检查男性和女性受检者所受总有效剂量分别为(10.44 ±1.09) mSv和(11.60 ±0.79) mSv。¹⁸F-FET PET-CT检查总有效剂量分别为(8.30 ±0.50) mSv和(8.72 ±0.49) mSv。在诊断性CT扫描中,CT扫描致男性受检者的有效剂量为(16.28 ±1.01) mSv,女性受检者为(13.49 ±0.72) mSv;¹⁸F-FDG PET-CT检查男性和女性受检者总有效剂量分别为(21.09 ±1.45) mSv和(19.58 ±1.03) mSv。¹⁸F-FET PET-CT检查总有效剂量分别为(18.95 ±1.08) mSv和(16.70 ±0.81) mSv。结论 不同的PET-CT扫描参数致受检者受到不同大小的辐射剂量,在日常工作中应根据受检者的实际情况,优化PET和CT的采集参数,降低受检者剂量,实践辐射防护最优化。     

Eine Übersicht über die ökonomische Evaluation der Positronen-Emissions-Tomographie

Since the nineties positron emission tomography (PET) has been increasingly used in clinical diagnostics in the area of oncology, cardiology, and neurology/psychiatry in Germany. As the use of PET requires a complex and expensive infrastructure, analysis of the cost-effectiveness of PET compared to common diagnostic methods is becoming increasingly important. This article summarizes and discusses the results of a report on cost-effectiveness studies on PET.     

Overview of economic evaluation of positron-emission tomography

Since the 1990s positron-emission tomography (PET) in Germany has been used increasingly in clinical diagnostics in the areas of oncology, cardiology, and neurology/ psychiatry. As the use of PET requires a complex and expensive infrastructure, analysis of the cost-effectiveness of PET compared to common diagnostic methods is becoming increasingly important. This contribution summarizes and discusses the results of a health technology assessment report on the cost-effectiveness of PET.     

重建技术对PET/CT图像空间分辨率影响的模型研究

目的:探讨重建技术对PET/CT中PET图像空间分辨率的影响。方法:采用PET/CT模拟临床条件进行图像数据采集,对分布于椭圆柱分辨率模体长轴方向上的5条线源及6层横断面行PET/CT扫描;选择滤波反投影(FBP)法和VUE Point HD迭代算法进行PET图像重建。迭代算法中增加点扩散函数(PSF)和飞行时间(TOF)两种新技术对图像进行重建,以线源半高宽(FWHM)表示重建图像的空间分辨率,计算5条线源6个层面上径向FWHM,求平均值。结果:在临床采集及重建条件下,使用PSF技术前、后中心位置图像空间分辨率分别为4.95 mm、4.28 mm;TOF技术使用前、后中心位置图像空间分辨率分别为4.95 mm、5.19 mm;FBP算法重建图像空间分辨率为4.63~7.45 mm;VUEPointHD算法空间分辨率为4.07~6.58 mm。结论:PSF技术能够有效提高PET图像空间分辨率,而TOF技术对图像空间分辨率无显著影响。重建算法对PET图像空间分辨率的影响较大,故需依据临床需求和经验选择来辅助决策。