Positron emission tomography in oncology

Summary. The particular advantages of positron emission tomography (PET) technique are that it has higher sensitivity, higher resolution, and a higher quality of image than that found in conventional nuclear medicine. The possibility of quantification and the wide range of useful tracers have raised expectations of this new method. To date, most of the human PET cancer studies have been performed with [¹⁸F]fluorodeoxyglucose (FDG) or [¹¹CJmethionine. These are good imaging agents for tumours. However, more specific radiopharmaceuticals are required if other features of tumour metabolism are to be observed, f¹¹Thymidine may prove to be a good tracer for quantitative measurements of tumour proliferation and [¹⁸F]misonidazole has been suggested for imaging of hypoxia.     

Positron emission tomography in oncology

Positron emission tomography (PET) scans use positrons, positively charged particles, to detect metabolic and chemical changes in the body. Although the clinical applications of this technology still are evolving, PET scans are being used to detect cancer and evaluate neurologic disorders, heart muscle function, and response to treatment. In oncology, PET scans may be used to determine biopsy location, stage disease, diagnose cancer recurrence, and discern malignant from benign conditions. PET scans also have led to the incidental diagnosis of cancer. This article reviews patient preparation and PET scan procedures and includes a patient information sheet on PET scanning. Oncology nurses need to be well informed about new technologies used in cancer care, such as PET scans, to better educate and prepare patients to undergo these tests.     

Positron emission tomography-computed tomography patient management and workflow

This article reviews the major considerations involved in optimizing positron emission tomography-computed tomographic (PET-CT) workflows including patient management and specific acquisition, processing, and archiving procedures. Due to the dual modality nature of PET-CT and the needs of the patients typically undergoing these examinations, there is a high level of patient contact and interaction with the technologists and ancillary personnel. Each PET-CT scan itself generates a considerable volume of raw image data which must be reconstructed, and the reconstructed images distributed and archived without impeding overall workflow. PET-CT facility design and layout, the procedures for sequencing patients through each phase of the exam, and adequate staffing are important considerations for an efficient and high-quality service.     

Positron emission tomography studies of brain receptors

Probing the regional distribution and affinity of receptors in the brain, in vivo, in human and non human primates has become possible with the use of selective ligands labelled with positron emitting radionuclides and positron emission tomography (PET). After describing the techniques used in positron emission tomography to characterize a ligand receptor binding and discussing the choice of the label and the limitations and complexities of the in vivo approach, the results obtained in the PET studies of various neurotransmission systems: dopaminergic, opiate, benzodiazepine, serotonin and cholinergic systems are reviewed.     

Positron emission tomography imaging as a cancer biomarker

The practice of oncology is changing, with novel biologic agents broadening our therapeutic armamentarium. Along with excitement and promise, multiple new challenges arise. The concept of 'individualized cancer care,' where therapies are selected based on the unique characteristics of a patient's tumor, is gaining favor as an approach to address the heterogeneity of cancer. As a result, we must strive to discover biomarkers with prognostic and predictive value to improve drug selection, alteration and development. Metabolic and molecular imaging with PET appears at the forefront of this critical field. In this review, we discuss cancer biomarker development, opportunities for PET to elucidate tumor biology and the potential role of PET in clinical research and practice.     

Positron emission tomography versus positron emission tomography/computed tomography: from "unclear" to "new-clear" medicine.

PET/CT is a new diagnostic imaging modality, which proves that adding PET and CT is not merely additive, but highly synergistic. While PET provides high sensitivity for lesion detection, CT provides the anatomic backdrop, which frequently is important in order to make a specific diagnosis. CT can, however, also add sensitivity to PET, as certain lesions such as small clearly pathological lung nodules may not at all be visualized on PET alone; and PET clearly adds specificity to CT because, e.g., indeterminate lymph nodes seen on CT can often be diagnosed unequivocally as benign or malignant, using PET information. Furthermore, attenuation correction of PET data, which is needed for best PET image quality, can also be obtained using the same CT data. Hence, PET/CT also provides a very fast solution for obtaining attenuation images. The major clinical applications of PET/CT are in tumor imaging of the body and the search for inflammatory foci, while for brain imaging, PET/CT is less relevant. In the brain, post acquisition fusion of PET and MRI data is relatively easy, while post acquisition fusion of PET and CT or MR data in the body is unreliable and cumbersome. We strongly feel that PET/CT is the oncological staging "one-stop-shop" examination of the future for many tumors. The key question in the next few years will be how much CT is needed in PET/CT for which clinical question? The advent of ever faster CT scanners suggests that PET/CT eventually may also provide a tool for a cardiac "one-stop-shop." So the future of PET/CT indeed looks bright.     

Positron emission tomography/computed tomography of a rare xanthogranulomatous process: Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a disseminated xanthogranulomatous infiltrative disease of unknown etiology due to infiltration of different organs and bones by foamy histiocytes. A 37-year-old male with cerebral and periorbital lesions was diagnosed with this rare disease and was evaluated with magnetic resonance imaging (MRI) and 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) with positron emission tomography/computed tomography (PET/CT) imaging at baseline and following therapy. FDG-PET imaging allowed accurate evaluation of the extent of the disease at baseline, as well as assessment of response to therapy.     

Positron emission tomography/computed tomography--imaging protocols, artifacts, and pitfalls.

There has been a longstanding interest in fused images of anatomical information, such as that provided by computed tomography (CT) or magnetic resonance imaging (MRI) systems, with biological information obtainable by positron emission tomography (PET). The near-simultaneous data acquisition in a fixed combination of a PET and a CT scanner in a combined PET/CT imaging system minimizes spatial and temporal mismatches between the modalities by eliminating the need to move the patient in between exams. In addition, using the fast CT scan for PET attenuation correction, the duration of the examination is significantly reduced compared to standalone PET imaging with standard rod-transmission sources. The main source of artifacts arises from the use of the CT-data for scatter and attenuation correction of the PET images. Today, CT reconstruction algorithms cannot account for the presence of metal implants, such as dental fillings or prostheses, properly, thus resulting in streak artifacts, which are propagated into the PET image by the attenuation correction. The transformation of attenuation coefficients at X-ray energies to those at 511 keV works well for soft tissues, bone, and air, but again is insufficient for dense CT contrast agents, such as iodine or barium. Finally, mismatches, for example, due to uncoordinated respiration result in incorrect attenuation-corrected PET images. These artifacts, however, can be minimized or avoided prospectively by careful acquisition protocol considerations. In doubt, the uncorrected images almost always allow discrimination between true and artificial finding. PET/CT has to be integrated into the diagnostic workflow for harvesting the full potential of the new modality. In particular, the diagnostic power of both, the CT and the PET within the combination must not be underestimated. By combining multiple diagnostic studies within a single examination, significant logistic advantages can be expected if the combined PET/CT examination is to replace separate state-of-the-art PET and CT exams, thus resulting in significantly accelerated diagnostics.     

Positron emission tomography as a tool for translational research in oncology.

Growing knowledge of the molecular mechanisms of oncological disease plays a key role in the improvement of prevention, diagnosis and treatment of malignant tumors. In this review, positron emission tomography (PET) is described as a mediator between molecular oncological research and clinical management of tumor patients. The most promising applications of PET in the near future include tumor imaging with newly developed tracers for diagnosis, staging and grading purposes, therapy monitoring with proliferation and apoptosis markers and definition of the tumor environment (e.g. hypoxia, neoangiogenesis) prior to therapy. Many of these applications will greatly benefit from the use of integrated PET/CT due to its precise spatial and morphological assignment of functional information. In conclusion, PET is both capable and necessary for the transference of new biological knowledge to clinical practice. Thus, PET constitutes a strong basis for an advanced and individually tailored approach to tumor patients.     

Positron emission tomography and central neurotransmitter systems in movement disorders

Summary— This article discusses the anatomical and neurochemical structure of the basal ganglia and reviews the Positron Emission Tomographic (PET) ligands available for investigating these pathways. We discuss how clinical PET studies have improved our understanding of the neurochemical changes underlying principal movement disorders.     

PET和脑磁图在术前评估MRI阴性癫痫中的作用

目的分析PET和脑磁图在术前评估MRI阴性癫痫中的作用。方法选取12例难治性癫痫(TLE)患者为研究对象,比较患者术前PET和脑磁图与手术结果。同时选取15名正常健康志愿者,通过病史、一般体格检查和常规实验室检测进行筛选。结果 1所有纳入本研究患者大脑MRI被视为没有MRI阴性癫痫的诊断价值。12例患者完全是正常的(1例在前叶显示极微小的异常)。218F-FCWAY的血浆游离分数(f1)在TLE患者高于健康对照(0.13±0.04 vs.0.09±0.07,P0.10)。3在局灶化MEG刺激区组8例,所有8例有局灶化癫痫发作。单侧性的MEG刺激区组7例,3例局灶化癫痫发作。非单侧MEG刺激区组2例没有局灶化癫痫发作。结论术前定位MRI阴性癫痫,PET/MEG结果一致时,手术结果判定比较准确。