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Tracer Uptake (tracer + uptake)
Selected AbstractsL -Amino acid load to enhance PET differentiation between tumor and inflammation: an in vitro study on 18F-FET uptakeCONTRAST MEDIA & MOLECULAR IMAGING, Issue 5 2006S. Laïque Abstract Labeled amino acids (AA) are tumor tracers for use in nuclear medecine. O -(2-[18F]fluoroethyl)- L -tyrosine (FET) is transported by the L -system, known to function as an exchanger. In vitro utilization of FET, after a preload or prior to an afterload of non radioactive L -amino acids, was evaluated in order to measure the potential effects of AA content on the distinction between tumor and inflammatory lesions. Cellular uptake of FET was studied on rat osteosarcoma cells (ROS 17/2.8) and human leukocytes, initially loaded with nonradioactive L -tyrosine or L -methionine. FET efflux was evaluated from cells loaded with nonradioactive L -phenylalanine after tracer uptake. ROS 17/2.8 showed a higher sensitivity to preload and afterload effects on cellular FET content as compared with the leukocytes. We conclude that preload with L -tyrosine, prior to the administration of FET, may be a potential procedure to improve PET differentiation between tumor and inflammatory lesions. Copyright © 2006 John Wiley & Sons, Ltd. [source] Selectivity and competitive interactions between two benthic invertebrate grazers (Asellus aquaticus and Potamopyrgus antipodarum): an experimental study using 13C- and 15N-labelled diatomsFRESHWATER BIOLOGY, Issue 2 2005N. ABERLE Summary 1. Tracer experiments with two diatoms labelled with 13C (Nitzschia palea) and 15N (Fragilaria crotonensis), were conducted to investigate feeding selectivity and interspecific competition between the grazers Asellus aquaticus (Isopoda, Crustacea) and Potamopyrgus antipodarum (Hydrobiidae, Gastropoda). Conventional methods, such as cell counts and estimated biovolume, were used first to detect feeding preferences within the different grazer treatments. 2. The results revealed a significant decline in algal biovolume in all grazer treatments and no indications of active selectivity were observed. In contrast to conventional methods, measurements based on isotope signatures showed strong differences in tracer uptake, thus indicating different degrees of assimilation and digestion by the two grazers. 3. The selectivity index Q, which provides information on the uptake ratio of 13C to 15N, showed a significant time effect for both grazer species and a significant difference between single- and mixed-grazer treatments for P. antipodarum. Thus, this technique enabled the direct quantification of the uptake by grazers and, therefore, served as an ideal tool for the detection of passive selectivity. 4. Our results indicate a shift in feeding preferences related to between-species competition and a potential divergence of trophic niches when species coexist. [source] Detection of cervical metastases with 11C-tyrosine pet in patients with squamous cell carcinoma of the oral cavity or oropharynx: A comparison with 18F-FDG PETHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 3 2010Christiaan A. Krabbe MD Abstract Background. A disadvantage of 2-[18F]fluoro-2-deoxy- D -glucose (18F-FDG) positron emission tomography (PET) in head and neck cancer is that 18F-FDG uptake is not specific to malignant tissue. To provide an alternative, radiolabeled amino acids such as L -1-[11C]-tyrosine (11C-TYR), were introduced because these are less avidly metabolized by inflammatory cells. Methods. In this prospective study, we compared both 11C-TYR PET and 18F-FDG PET performance in detecting cervical metastases in 27 patients with a squamous cell carcinoma (SCC) of oral cavity or oropharynx. Results. 11C-TYR PET sensitivity, specificity, and accuracy for detecting nodal metastases were 33%, 100%, and 81%, respectively. With respect to 18F-FDG PET, these figures were 67%, 97%, and 89%, respectively. Neck metastases not detected by 11C-TYR PET were camouflaged by high tracer uptake by salivary glands. Conclusions. Because of bilateral accumulation of 11C-TYR in salivary glands, 11C-TYR PET is not suitable to replace 18F-FDG PET in staging SCC of oral cavity and oropharynx. © 2009 Wiley Periodicals, Inc. Head Neck, 2010 [source] What Is the Relationship of Low Back Pain to Signs of Abnormal Skeletal Metabolism Detected by Bone Scans?PAIN MEDICINE, Issue 2 2008Brenda Breuer PhD ABSTRACT Background., In approximately 80,85% of patients with chronic nonspecific low back pain (NSLBP), a precise pathoanatomical diagnosis cannot be identified. Mechanisms of bone nociception may contribute to NSLBP. Objective., To determine whether findings on bone scans, which provide a pathophysiological picture of functional activity, are associated with self-reports of NSLBP intensity. Design., A cross-sectional study of the relationship of self-reported chronic NSLBP intensity to the uptake of radiolabeled technetium-99m-methylene diphosphonate in the lumbosacral area. Study Participants., Patients referred for bone scans who were at least 18 years old. Outcome Measures., Subject reports of pain intensity and intensity of uptake of radiolabeled technetium-99m-methylene diphosphonate in the lumbosacral area. Results., Among subjects who were 65 years or younger, the age-adjusted worst pain intensity accounted for 45% of the variability in the amount of tracer uptake (r = 0.67, P = 0.0006). The association was not significant for those older than 65 years. Conclusion., Further studies should be conducted on possible mechanisms relating bone nociception to chronic NSLBP in individuals who are 65 years or younger. [source] Prospective comparison of [18F]fluorodeoxyglucose positron emission tomography with conventional assessment by computed tomography scans and serum tumor markers for the evaluation of residual masses in patients with nonseminomatous germ cell carcinomaCANCER, Issue 9 2002Christian Kollmannsberger M.D. Abstract BACKGROUND To assess the ability of [18F]fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET) to predict the viability of residual masses after chemotherapy in patients with metastatic nonseminomatous germ cell tumors (GCT), PET results were compared in a blinded analysis with computed tomography (CT) scans and serum tumor marker changes (TUM) as established methods of assessment. METHODS Independent reviewers who were blinded to each other's results evaluated the PET results and corresponding CT scan and TUM results in 85 residual lesions from 45 patients. All patients were treated within prospective clinical trials and received primary/salvage, high-dose chemotherapy with autologous blood stem cell support for primary poor prognosis disease or recurrent disease. PET results were assessed both visually and by quantifying glucose uptake (standardized uptake values). Results were validated either by histologic examination of a resected mass and/or biopsy (n = 28 lesions) or by a 6-month clinical follow-up after evaluation (n = 57 lesions). RESULTS F-18 FDG PET showed increased tracer uptake in 32 of 85 residual lesions, with 29 true positive (TP) lesions and three false positive (FP) lesions. Fifty-three lesions were classified by PET as negative (no viable GCT), 33 lesions were classified by PET as true negative (TN), and 20 lesions were classified by PET as false negative (FN). In the blinded reading of the corresponding CT scan and TUM results, 38 residual lesions were assessed correctly as containing viable carcinoma and/or teratoma. Forty-six lesions were classified as nonsuspicious by CT scan/TUM (33 TN lesions and 14 falsely classified lesions). PET correctly predicted the presence of viable carcinoma in 5 of these 14 and the absence of viable carcinoma in 3 of these 14 lesions. Resulting sensitivities and specificities for the prediction of residual mass viability were as follows: PET, 59% sensitivity and 92% specificity; radiologic monitoring, 55% sensitivity and 86% specificity; and TUM, 42% sensitivity and 100% specificity. The positive and negative predictive values for PET were 91% and 62%, respectively. The diagnostic efficacy of PET did not improve when patients with teratomatous elements in the primary tumor were excluded from the analysis. In patients with multiple residual masses, a uniformly increased residual F-18 FDG uptake in all lesions was a strong predictor for the presence of viable carcinoma. CONCLUSIONS F-18 FDG PET imaging performed in conjunction with conventional staging methods offers additional information for the prediction of residual mass histology in patients with nonseminomatous GCT. A positive PET is highly predictive for the presence of viable carcinoma. Other useful indications for a PET examination include patients with multiple residual masses and patients with marker negative disease. Cancer 2002;94:2353,62. © 2002 American Cancer Society. DOI 10.1002/cncr.10494 [source] The role of 18F-FDOPA and 18F-FDG,PET in the management of malignant and multifocal phaeochromocytomasCLINICAL ENDOCRINOLOGY, Issue 4 2008D. Taïeb Summary Background,18F-DOPA has emerged as a promising tool in the localization of chromaffin-tissue-derived tumours. Interestingly, phaeochromocytomas (PHEO) are also FDG avid. Aim and methods,The aim of this study was to retrospectively evaluate the results of 18F-FDOPA and/or 18F-FDG,PET in patients with PHEO and paragangliomas (PGLs) and to compare the outcome of this approach with the traditional therapeutic work-up. Nine patients with non-MEN2 related PHEO or PGL were evaluated. At the time of the PET studies, the patients were classified into three groups based on their clinical history, conventional and SPECT imaging. The groups were malignant disease (n = 5, 1 VHL), apparently unique tumour site in patients with previous surgery (n = 1, SDHB) and multifocal tumours (n = 3, 1 VHL, 1 SDHD). 18F-FDOPA and 18F-FDG,PET PET/CT were then performed in all patients. Results, PET successfully identified additional tumour sites in five out of five patients with metastatic disease that had not been identified with SPECT + CI. Whilst tumour tracer uptake varied between patients it exhibited a consistently favourable residence time for delayed acquisitions. 18F-FDOPA uptake (SUVmax) was superior to 18F-FDG uptake in cases of neck PGL (three patients, four tumours). If only metastatic forms and abdominal PGLs were considered, 18F-FDG provided additional information in three cases (two metastatic forms, one multifocal disease with SDHD mutation) compared to 18F-FDOPA. Conclusions, Our results suggest that tumour staging can be improved by combining 18F-FDOPA and 18F-FDG in the preoperative work-up of patients with abdominal and malignant PHEOs. 18F-FDOPA is also an effective localization tool for neck PGLs. MIBG however, still has a role in these patients as MIBG and FDOPA images did not completely overlap. [source] Giant cell arteritis on 18F-FDG PET/CTCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2009Thomas F. Heston Summary Purpose:, We present a case of incidentally noted giant cell arteritis in a patient undergoing 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT imaging. The patient was originally referred to PET/CT for staging of his renal transitional cell carcinoma. Methods:, The patient was injected intravenously with 370 MBq of 18F-FDG. After a 60 min uptake period, PET/CT imaging was performed from the skull base to the mid thighs. Results:, A small para-aortic node in the region of the surgical bed showed increased tracer uptake of concern for malignancy. In addition, there were several non-calcified pulmonary nodules present, also concerning for malignancy. Incidentally noted was diffusely increased tracer uptake throughout the aorta and a thickened aortic wall on CT images. Diffuse tracer uptake was also present in the proximal branches of the aorta, including the carotid, iliac, femoral, and subclavian arteries. The patient had biopsy proven giant cell arteritis. Conclusion:, Increased 18F-FDG uptake by the aorta on PET/CT imaging is an abnormal finding that prompts a more thorough assessment for malignancy, and also can indentify important co-morbidities in cancer patients. Evaluation of aortic uptake should be a routine practice in the interpretation of 18F-FDG PET/CT scans. [source] Arterial concentration of 99mTc-sestamibi at rest, during peak exercise and after dipyridamole infusionCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2004Niels Peter Rønnow Sand Summary Tracers for myocardial perfusion imaging during stress should not only have high cardiac uptake but they should also have a fast blood clearance to prevent myocardial tracer uptake after the ischaemic stimulus. The present study characterize the early phase of the arterial 99mTc-sestamibi (MIBI) time-activity curve after venous bolus injection at rest, during peak exercise and after dipyridamole infusion. We included 11 patients undergoing angioplasty for one-vessel disease (rest study) and 20 patients evaluated for the detection of haemodynamic significant coronary stenoses by 99mTc-sestamibi single photon emission computed tomography (SPECT) using either bicycle exercise testing (10 patients) or standard dipyridamole testing (10 patients). Arterial blood samples of 1 ml were taken from the left femoral artery (rest study) or the right radial artery (exercise and dipyridamole studies) every 5 s during the first 5 min postinjection. In the exercise and the dipyridamole studies blood sampling were extended to include blood samples every 5 min 5,30 min postinjection. Peak MIBI concentration was lower and decrease in concentration slower after tracer injection during exercise than during dipyridamole stress testing. This may cause an underestimation of perfusion defects during exercise because of MIBI uptake after the ischaemic stimulus. The implications of the study not only refer to the choice of stress modality when using MIBI. This study also underlines the importance of considering early blood clearance in addition to regional myocardial tracerkinetic aspects such as myocardial extraction fraction when new tracers are introduced. [source] | ||||||||||