Positron emission tomography

Summary One of the most exciting new techniques introduced in the last ten years is positron emission tomography (PET). PET provides quantitative, three-dimensional images for the study of specific biochemical and physiological processes in the human body. This approach is analogous to quantitativein vivo autoradiography but has the added advantage of permitting non-invasivein vivo studies. PET scanning requires a small cyclotron to produce short-lived positron emitting isotopes such as oxygen-15, carbon-11, nitrogen-13 and fluorine-18.Proper radiochemical facilities and advanced computer equipment are also needed. Most important, PET requires a multidisciplinary scientific team of physicists, radiochemists, mathematicians, biochemists and physicians. This review analyses the most recent trends in imaging technology, radiochemistry, methodology, and clinical applications of positron emission tomography.Reproduced with kind permission of Pergamon Press from the special issue of Radiation Physics and Chemistry on Radiation and Medicine (1984). Guest Editors: B. C. Lentle and H. Singh.     

Positron emission tomography in urological malignancy

Positron emission tomography is a unique imaging modality with the capability of studying regional metabolism. The major clinical applications of positron emission tomography have been in the detection of brain, breast, cardiac, lung and colorectal tumours, as well as the evaluation of coronary artery disease by imaging the metabolism of heart muscle. In the field of urology, positron emission tomography has been evaluated in the relevant malignancies with promising results in certain areas and disappointing results in others. This article attempts to summarize recent advances in positron emission tomography scanning with regards to urological malignancy. At this stage positron emission tomography scanning is capable of visualizing urological tumours and associated lymph nodes and distal metastatic sites. However, its use is severely limited by the excretion of the most commonly used radioisotope via the urinary tract, making pelvic imaging particularly unrewarding. It is, however, undoubtedly capable of diagnosing malignancy in soft tissue masses or lymph nodes before these changes become apparent on conventional cross-sectional imaging modalities (computerized tomography or magnetic resonance imaging). Larger studies are required before it can be advocated for clinical use in the field of urology.     

Positron emission tomography in lung cancer

Recent advances in positron emission tomography (PET) with 2-deoxy-2-fluoro [F-18]-d-glucose (FDG) has enabled not only the diagnosis and staging of lung cancer but also the prediction of its malignancy grade. However, FDG-PET has been known to have several pitfalls for imaging of lung cancer. For the effective clinical use of FDG-PET in lung cancer, we reviewed the pitfalls of using FDG-PET in the diagnosis of pulmonary nodules, semiquantitative analysis of FDG-uptake, N-staging, prediction of tumor aggressiveness, prognostic significance, and prediction of pathological response after chemoradiotherapy. __________ This review was submitted at the invitation of the editorial committee.     

Positron emission tomography and scintigraphy. Nuclear imaging in clinical orthopaedics

Nuclear medicine uses the function of organs or organ systems to diagnose and treat disease. The source of radiation is brought into the patient's body by means of a radioactive labelled pharmaceutical. Its way through the body is recorded by appropriate equipment on the outside. Of the many nuclear medical procedures, those primarily applicable to orthopaedic problems are explained here, such as bone scintigraphy, scintigraphy of inflammatory lesions, and tumour scintigraphy. Besides their use in diagnostics, therapeutic applications are covered as well. Using examples from clinical practice, "conventional" nuclear medicine and positron emission tomography are also covered.     

Positron emission tomography in non-medullary thyroid cancer

While iodine scanning is the mainstay of functional imaging in differentiated thyroid cancer, there is now a significant body of literature regarding positron emission tomography with 2-fluoro-2-deoxy glucose in thyroid cancer. This clinical review will examine the evidence supporting the use of 2-fluoro-2-deoxy glucose-positron emission tomography throughout the diagnosis and management of thyroid cancer, and provide suggestions for its clinical use and potential future roles.     

Positron emission tomography detected thyroid incidentaloma

We describe the case of a 48-year-old woman who presented with a thyroid lesion incidentally detected on positron emission tomography/computed tomography for a suspicious lung lesion. Subsequent clinical examination and investigations revealed a 3cm nodule in the left lower pole of the thyroid. Fine needle aspiration was indeterminate for malignancy. A left hemithyroidectomy was performed and histology confirmed a benign thyroid adenoma with an incidental micropapillary carcinoma. The literature regarding the best management for thyroid incidentalomas remains uncertain and, as such, each patient must be managed on an individual basis.     

Positron emission tomography and colorectal cancer

BACKGROUND: The oncological applications of positron emission tomography (PET) have gained widespread acceptance. This rapidly evolving technology has been applied successfully to colorectal cancer, but has not yet become part of routine clinical practice. This review considers (1) the biological basis for the use of PET in colorectal cancer, (2) the technical aspects of PET relevant to the referring clinician and (3) the application of PET to the management of primary and recurrent disease. METHODS: A Medline database search was performed for the period 1980-2000. Experience was also drawn from the first 40 patients with colorectal cancer investigated at this institution. RESULTS AND CONCLUSION: PET has a proven role, and is cost effective in the management of recurrent cancer and the monitoring of therapy. However, further evaluation is still required to justify its routine use for other indications in colorectal cancer. Development of new positron-labelled radio- pharmaceuticals, in parallel with advances in detector technology and innovative models for tracer production and distribution, means that the availability of PET and its applications in the management of colorectal cancer will expand over the coming years.     

Positron emission tomography for urological tumours

For urological tumours, positron emission tomography (PET) is currently most useful in testicular cancer. In patients with residual masses or raised marker levels after treatment, PET is both sensitive and specific for detecting recurrent disease, at suspected and unsuspected sites. Although fewer studies are available it also appears to be useful for staging at diagnosis, although this requires further investigation. Prostate cancer imaging has been more variable, with studies showing that PET cannot reliably differentiate between tumour and hypertrophy. It is not as good as a bone scan for defining bone metastases. In renal cancer, PET can be used to define the primary tumour, providing better staging of local recurrence than computed tomography (CT), and to define metastatic disease. There are few studies in bladder cancer, and despite excretion of the tracer via the bladder in early studies, it has better results than CT or magnetic resonance imaging for local staging; again it can detect metastases. Overall, the place of PET in urological tumours is developing, with the strongest areas undoubtedly being testicular and renal cancer. Tracers other than fluorodeoxyglucose are being examined and are providing further information.     

Positron emission tomography imaging-directed stereotactic neurosurgery.

The diagnostic yield of stereotactic biopsies depends upon safely sampling the most representative regions of masses. Potentially, localization information presently available from CT and MR scans might be improved by considering regional levels of cerebral metabolism by PET. In 10 selected stereotactic biopsies of intracranial mass lesions, PET scans were obtained using the Siemens CTI system; the Kelly-Goerss Compass system was used as the stereotactic development platform. PET-[18F]-fluorodeoxyglucose (FDG) images provided clinically significant information by appropriately directing biopsy efforts when CT and MRI was inconclusive or misleading. PET-FDG images can be successfully incorporated into routine image-directed stereotactic surgery.     

Positron emission tomography with 18F-FDG in osteoarthritic knee

OBJECTIVES: To evaluate osteoarthritis (OA) of the knee using positron emission tomography (PET) with 2-(18)F-fluoro-2-deoxy-D-glucose ((18)F-FDG) as a tracer. MATERIALS AND METHODS: Fifteen patients with medial-type knee OA and three healthy subjects were enrolled in the study. After clinical examination and conventional radiography, (18)F-FDG PET and magnetic resonance imaging (MRI) were performed. (18)F-FDG uptake was quantified as a standardized uptake value (SUV) and the localization of (18)F-FDG uptake was identified using fusion images created with MRI scans. RESULTS: (18)F-FDG generally accumulated in periarticular lesions and was absent in the articular cartilage. SUVs of the whole knee were higher in OA than in controls, and those in the medial condyle were higher than in the lateral condyle in OA. Prominent (18)F-FDG uptake was found in the intercondylar notch in OA and extended along the posterior cruciate ligament (PCL) in some cases. Periosteophytic accumulation was found in one-half of cases with definite osteophytes. Accumulation was also found in subchondral lesions and bone marrow, which corresponded with bone edema diagnosed by MRI. No significant correlation was found between SUV and clinical manifestations. CONCLUSIONS: (18)F-FDG uptake was upregulated in OA and generally accumulated in periarticular lesions. Increased uptake was found in the intercondylar notch extending along the PCL, periosteophytic lesions, and bone marrow. These results provide in vivo pathognomonic insights into OA.     

Positron emission tomography in the study of cerebral tumours

Summary Positron emission tomography (PET) uses the shortlived positron-emitting radioisotopes of elements such as oxygen, nitrogen, and carbon as tracers both to image and to measure, non-invasively, normal regional tissue physiology and pathophysiology in man. This technique has been used to study the pathophysiology of brain tumours at the time they present and after therapeutic intervention.     

Positron emission tomography in a patient with renal malacoplakia

Positron emission tomography is increasingly used for the diagnosis of occult infection or malignancy. The altered metabolic rate of cells in areas of malignancy or infection provides a sensitive method to identify pathology that is otherwise not identified by standard imaging methods. This case report describes a patient who presented with a pyrexia of unknown origin and renal impairment. She had a positron emission tomography scan that showed intense accumulation of fluoro-deoxy-glucose in both kidneys. Subsequent renal biopsy results showed a diagnosis of malacoplakia, the treatment of which resulted in a resolution of the fever and a stabilization of renal function. This is the first report of the positron emission tomographic appearance of renal malacoplakia.     

Role of positron emission tomography in urological oncology

??Positron emission tomography (PET) is a diagnostic tool using radiotracers to show changes in metabolic activities in tissues. We analysed the role of PET and PET/computed tomography (CT) in the diagnosis, staging, and follow-up of urological tumours. ??A critical, non-structured review of the literature of the role of PET and PET/CT in urological oncology was conducted. ??PET and PET/CT can play a role in the management of urological malignancies. For prostate cancer, the advances in radiotracers seems promising, with novel radiotracers yielding better diagnostic and staging results than 18F-fluorodeoxyglucose (18F-FDG). In kidney cancer, PET and PET/CT allow a proper diagnosis before the pathological examination of the surgical specimen. For testis cancer, PET and PET/CT have been shown to be useful in the management of seminoma tumours. In bladder cancer, these scans allow a better initial diagnosis for invasive cancer, while detecting occult metastases. ??PET and its combined modality PET/CT have shown their potential in the diagnosis of urological malignancies. However, further studies are needed to establish the role of PET in the management of these diseases. Future applications of PET may involve fusion techniques such as magnetic resonance imaging with PET.     

特殊示踪剂正电子发射体层显像在肺部病变诊断中的应用

目的 探讨胆碱、甲硫氨酸、脱氧胸腺嘧啶核苷、乙酸盐为示踪剂的正电子发射体层显像(PET)在肺部病变诊断中的应用价值.方法 2002年6月至2007年6月对100例肺部占位病变的患者行PET检查.其中~(11)C-胆碱(CH)-PET检查58例,~(11)C-甲硫氨酸(MET)-PET检查16例,~(18)F-脱氧胸腺嘧啶核苷(FLT)-PET检查22例,~(11)C-乙酸盐(AC)-PET检查4例.结果 采用目测法判读,半定量分析法测量病变标准摄取值,结果与病理诊断及随访结果对照.结果CH-PET定性诊断灵敏度、特异度、符合率分别为84.2%(32/38)、57.9%(11/19)、75.4%(43/57).MET-PET定性诊断灵敏度、特异度、符合率分别为6/7、6/9、75.0%(12/16).FLT-PET检查定性诊断灵敏度、特异度、符合率分别为85.7%(12/14)、2/8、63.6%(14/22).CH.PET、MET-PET及FLT-PET中肿瘤标准摄取值与肿瘤大小、患者年龄不相关.AC.PET检查仅1例透明细胞癌肺转移显影,2例鳞状细胞癌、1例腺癌没有显影.结论 这些示踪剂PET对肺部病变的定性诊断有帮助,但存在假阳性和假阴性结果.     

Positron emission tomography reveals a leiomyosarcoma causing proteinuria

Obstruction of the renal veins may result in proteinuria and is frequently caused by thrombosis or tumorous processes. Since thrombosis and malignancy may occur simultaneously in the venous outflow of the kidneys, search for an underlying intraluminal tumor may be impeded by extensive thrombosis in the lumen of renal and caval veins. We report the case of a 30-year-old man with moderate proteinuria which was caused by an obstructing process of the vena cava inferior and the renal veins. While the obstructive mass was initially misdiagnosed as thrombosis, positron emission tomography helped to reveal the tumorous character of the lesion and fine-needle biopsy allowed rapid diagnosis of a leiomyosarcoma originating from the caval or renal veins. We conclude that undelayed diagnosis of the cause of renal and caval vein obstruction is facilitated by early positron emission tomography and subsequent fine-needle biopsy to identify possible tumorous lesions.