Degree Of Fluorodeoxyglucose Uptake Research Articles

Cross-sectional evaluation of FGD-avid polyostotic fibrous dysplasia: MRI, CT and PET/MRI findings

A 42-year-old male with left hip pain was diagnosed of several right femoral and tibial bone tumours. All lesions were osteolytic with sclerotic margins. The symptomatic lesion in the proximal femur also showed bone expansion and focal cortical thinning. Whole-body [18F]-fluorodeoxyglucose (FDG) PET/CT and segmental PET/MRI of the left hip and femur were performed for metabolic characterization of the lesions and for biopsy guidance. The lesions showed a heterogenous degree of FDG uptake corresponding to different metabolic stages of the disease. A biopsy of the tumour portion showing the highest FDG uptake revealed a fibrous dysplasia (FD). In conclusion, although generally affecting paediatric and adolescent subjects, polyostotic FD may be detected in the adulthood. Despite the benign nature of the disease, increased glucose metabolism can be seen in some lesions. Hybrid imaging combining morphological and functional information may help guide biopsy and better define the treatment strategy.

Prevalence and Significance of FDG-avid Mediastinal Lymph Nodes in Patients with Colorectal Cancer in a Tuberculosis-endemic Area

Objective: To find prevalence and causes of fluorodeoxyglucose (FDG)-avid mediastinal lymph nodes in patients with colorectal cancer in a tuberculosis-endemic area.Material and Methods: For this study we enrolled patients with colorectal cancer who underwent Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT). Then, PET/CT images were reviewed by a nuclear medicine physician to find mediastinal lymph nodes with FDG uptake beyond the lung background defined as FDG-avid node. The degree of FDG uptake was graded and measured, and associated factors for presence of FDG-avid nodes were evaluated. The causes of FDG-avid nodes were also determined.Results: A total of 109 patients (64 males; mean age 61.2 years) were studied. Seventy-five patients had FDG-avid mediastinal nodes; accounting for a prevalence of 68.8% (95% CI: 59.2-77.3%). Most of the patients had multiple and bilateral nodes; with the zones of hilar and interlobar being the most common location. Age ≥50 years was the only associated factor for FDG-avid nodes (OR of 3.16, p-value=0.035). Only one out of the 32 patients (with fulfilled followup criteria) had a metastatic node.Conclusion: The prevalence of FDG-avid mediastinal nodes in colorectal cancer patients in a tuberculosis-endemic area was significantly high. Most of the lesions were benign in nature; thus, interpretation of these findings should be considered carefully to avoid false-positive results.

Automatic detection and classification of regions of FDG uptake in whole-body PET-CT lymphoma studies

[18F]-Fluorodeoxyglucose (FDG) positron emission tomography–computed tomography (PET–CT) scans of lymphoma patients usually show disease involvement as foci of increased radiotracer uptake. Existing methods for detecting abnormalities, model the characteristics of these foci; this is challenging due to the inconsistent shape and localization information about the lesions. Thresholding the degree of FDG uptake is the standard method to separate different sites of involvement. But may fragment sites into smaller regions, and may also incorrectly identify sites of normal physiological FDG uptake and normal FDG excretion (sFEPU) such as the kidneys, bladder, brain and heart. These sFEPU can obscure sites of abnormal uptake, which can make image interpretation problematic. Identifying sFEPU is therefore important for improving the sensitivity of lesion detection and image interpretation. Existing methods to identify sFEPU are inaccurate because they fail to account for the low inter-class differences between sFEPU fragments and their inconsistent localization information. In this study, we address this issue by using a multi-scale superpixel-based encoding (MSE) to group the individual sFEPU fragments into larger regions, thereby, enabling the extraction of highly discriminative image features via domain transferred convolutional neural networks. We then classify there regions into one of the sFEPU classes using a class-driven feature selection and classification model (CFSC) method that avoids overfitting to the most frequently occurring classes. Our experiments on 40 whole-body lymphoma PET-CT studies show that our method achieved better accuracy (an average F-score of 91.73%) compared to existing methods in the classification of sFEPU.

Malignancies with Low Fluoro-deoxyglucose Uptake at PET/CT: Pitfalls and Prognostic Importance

This copy is for personal use only. To order printed copies, contact reprints@rsna.org Malignancies with Low Fluoro- deoxyglucose Uptake at PET/CT: Pitfalls and Prognostic Importance 1 Abbreviations: FDG = fluorine 18 fluoro- deoxyglucose, HCC = hepatocellular carci- noma, SUV = standardized uptake value RadioGraphics 2016; 36:293–294 Published online 10.1148/rg.2015150073 Content Codes: From the Department of Radiology and Bio- medical Imaging, University of California–San Francisco, 505 Parnassus Ave, San Francisco, CA 94143. Recipient of a Certificate of Merit award for an education exhibit at the 2014 RSNA Annual Meeting. Received March 19, 2015; revision requested August 28 and received October 3; accepted October 23. All authors have disclosed no relevant relationships. Ad- dress correspondence to S.C.B. (e-mail: spen- cer.behr@ucsf.edu). Funding: The work was the National Institutes of 5T32EB001631-10). supported by Health (grant R.R.F. supported by an RSNA Research Fel- low Grant and a Society of Nuclear Medicine and Molecular Imaging–Educational Research Foundation Mitzi & William Blahd, MD, Pilot Research Grant. RSNA, 2016 The full digital presentation is available online. Fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) is commonly performed for staging and restaging of solid tu- mors. Although most solid tumors demonstrate high uptake of FDG, many others do not. Low FDG uptake may be due to various reasons, including tumors with low glucose metabolism or low cellularity, improper patient preparation, and small tumor size. The presence of low-level FDG uptake could be a source of scan misinterpretation in these low-cellularity or low-glucose-metabolizing tumors, including low-grade lung adenocarcinomas, renal cell cancers, and mucinous neoplasms. The ability to detect lesions at PET/computed tomography (CT) stems from many factors, including size of the lesion, ability of the tumor to concentrate FDG, proper patient preparation, back- ground FDG uptake in surrounding tissues, and type of scanner used. Several examples of low-grade lung adenocarcinoma, renal cell cancer, and mucinous neoplasms are presented that have low FDG uptake. For example, Figure 1 depicts a renal cell cancer without associated FDG avidity above background activity. In many neoplasms, including hepatocellular carcinoma (HCC), lymphoma, and prostate cancer, there is strong evidence that increas- ing FDG avidity correlates with poor prognosis and poor response to treatment. In these cases, high FDG uptake likely correlates with de- differentiation or transformation to a more aggressive form of cancer. For example, in HCC, high FDG uptake predicts poor response to radiation therapy, transarterial chemoembolization, and liver trans- plantation and is also associated with higher stage and the presence of metastatic disease. Similarly, lesions with high FDG uptake in a patient with a known low-grade lymphoma are suspicious for high- grade transformation (also called Richter transformation). Therefore, in lymphoma, prostate cancer, and HCC, it is important for radiolo- gists to report the degree of FDG uptake. TEACHING POINTS Some malignancies will demonstrate low-level or absent FDG uptake, including renal cell cancer, low-grade lung adenocarcinomas, and mucinous neoplasms. In some malignancies, including HCC, prostate cancer, and low-grade lymphomas, the presence of high-level FDG uptake correlates with poor prognosis. In general, higher FDG uptake in these malignancies correlates with a poorly differenti- ated neoplasm that will have a relatively poor treatment response. In some malignancies, uptake of a second radiotracer is typically inversely correlated with uptake of FDG. This property is termed the flip-flop effect and is commonly seen in thyroid cancer and neuroendocrine tumors. RESIDENT AND FELLOW EDUCATION FEATURE Robert R. Flavell, MD, PhD David M. Naeger, MD Carina Mari Aparici, MD Randall A. Hawkins, MD, PhD Miguel H. Pampaloni, MD, PhD Spencer C. Behr, MD NUCLEAR MEDICINE |

Colorectal Cancer Liver Metastases: Diagnostic Performance and Prognostic Value of PET/MR Imaging.

Purpose To evaluate the diagnostic performance of combined positron emission tomography (PET) and magnetic resonace (MR) imaging (hereafter, PET/MR imaging) in the detection of liver metastases and to assess its prognostic value in patients with colorectal cancer liver metastases (CRLMs). Materials and Methods Institutional review board approval was obtained for this retrospective study, with waiver of informed consent. A total of 55 patients with 98 CRLMs who underwent PET/MR imaging and multidetector computed tomography (CT) between January 2013 and June 2014 comprised the study population. Of these patients, 34 underwent hepatic resection, 18 of whom also underwent neoadjuvant chemotherapy (NAC). Two board-certificated radiologists independently assessed the four image sets (ie, multidetector CT, whole-body PET, MR imaging with a liver-specific contrast agent [hereafter, EOB MR imaging], and PET/MR imaging). To compare the diagnostic performance of each imaging modality, jackknife alternative free-response receiver operating characteristic and generalized estimating equations were used. To assess prognostic value, recurrence-free survival of the 18 patients who underwent NAC followed by hepatic resection was analyzed by using the Kaplan-Meier method and log-rank test. Results The reader-averaged figure of merit of PET/MR imaging was significantly higher than that of either multidetector CT (P = .003) or PET (P = .020) in the detection of CRLMs. However, no significant difference was observed between figure of merit for PET/MR imaging and that for EOB MR imaging (P = .231). After NAC, six of the 18 patients had isometabolic CRLMs on PET images, and 12 patients had hypermetabolic CRLMs. The 1-year recurrence-free survival rate was 80% in patients with isometabolic CRLMs and 14% in patients with hypermetabolic CRLMs, showing a significant difference (P = .026). Conclusion PET/MR imaging can yield significantly higher diagnostic performance in the detection of CRLMs when compared with the performance of multidetector CT or PET. However, no significant difference in diagnostic performance was observed between PET/MR imaging and EOB MR imaging. In addition, the degree of fluorodeoxyglucose uptake after NAC may have the potential to yield prognostic information for recurrence-free survival after hepatic resection. (©) RSNA, 2016 Online supplemental material is available for this article.

Malignancies with Low Fluorodeoxyglucose Uptake at PET/CT: Pitfalls and Prognostic Importance: Resident and Fellow Education Feature.

This copy is for personal use only. To order printed copies, contact reprints@rsna.org Malignancies with Low Fluoro- deoxyglucose Uptake at PET/CT: Pitfalls and Prognostic Importance 1 Abbreviations: FDG = fluorine 18 fluoro- deoxyglucose, HCC = hepatocellular carci- noma, SUV = standardized uptake value RadioGraphics 2016; 36:293–294 Published online 10.1148/rg.2015150073 Content Codes: From the Department of Radiology and Bio- medical Imaging, University of California–San Francisco, 505 Parnassus Ave, San Francisco, CA 94143. Recipient of a Certificate of Merit award for an education exhibit at the 2014 RSNA Annual Meeting. Received March 19, 2015; revision requested August 28 and received October 3; accepted October 23. All authors have disclosed no relevant relationships. Ad- dress correspondence to S.C.B. (e-mail: spen- cer.behr@ucsf.edu). Funding: The work was the National Institutes of 5T32EB001631-10). supported by Health (grant R.R.F. supported by an RSNA Research Fel- low Grant and a Society of Nuclear Medicine and Molecular Imaging–Educational Research Foundation Mitzi & William Blahd, MD, Pilot Research Grant. RSNA, 2016 The full digital presentation is available online. Fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) is commonly performed for staging and restaging of solid tu- mors. Although most solid tumors demonstrate high uptake of FDG, many others do not. Low FDG uptake may be due to various reasons, including tumors with low glucose metabolism or low cellularity, improper patient preparation, and small tumor size. The presence of low-level FDG uptake could be a source of scan misinterpretation in these low-cellularity or low-glucose-metabolizing tumors, including low-grade lung adenocarcinomas, renal cell cancers, and mucinous neoplasms. The ability to detect lesions at PET/computed tomography (CT) stems from many factors, including size of the lesion, ability of the tumor to concentrate FDG, proper patient preparation, back- ground FDG uptake in surrounding tissues, and type of scanner used. Several examples of low-grade lung adenocarcinoma, renal cell cancer, and mucinous neoplasms are presented that have low FDG uptake. For example, Figure 1 depicts a renal cell cancer without associated FDG avidity above background activity. In many neoplasms, including hepatocellular carcinoma (HCC), lymphoma, and prostate cancer, there is strong evidence that increas- ing FDG avidity correlates with poor prognosis and poor response to treatment. In these cases, high FDG uptake likely correlates with de- differentiation or transformation to a more aggressive form of cancer. For example, in HCC, high FDG uptake predicts poor response to radiation therapy, transarterial chemoembolization, and liver trans- plantation and is also associated with higher stage and the presence of metastatic disease. Similarly, lesions with high FDG uptake in a patient with a known low-grade lymphoma are suspicious for high- grade transformation (also called Richter transformation). Therefore, in lymphoma, prostate cancer, and HCC, it is important for radiolo- gists to report the degree of FDG uptake. TEACHING POINTS Some malignancies will demonstrate low-level or absent FDG uptake, including renal cell cancer, low-grade lung adenocarcinomas, and mucinous neoplasms. In some malignancies, including HCC, prostate cancer, and low-grade lymphomas, the presence of high-level FDG uptake correlates with poor prognosis. In general, higher FDG uptake in these malignancies correlates with a poorly differenti- ated neoplasm that will have a relatively poor treatment response. In some malignancies, uptake of a second radiotracer is typically inversely correlated with uptake of FDG. This property is termed the flip-flop effect and is commonly seen in thyroid cancer and neuroendocrine tumors. RESIDENT AND FELLOW EDUCATION FEATURE Robert R. Flavell, MD, PhD David M. Naeger, MD Carina Mari Aparici, MD Randall A. Hawkins, MD, PhD Miguel H. Pampaloni, MD, PhD Spencer C. Behr, MD NUCLEAR MEDICINE |

Primary tumor PET/CT [18F]FDG uptake is an independent predictive factor for regional lymph node metastasis in patients with non-small cell lung cancer

Aim: To investigate the correlation between [18F]fluorodeoxyglucose (FDG) uptake in a primary tumor and pathologic N stages, and to further analyze the possible risk factors contributing to the regional lymph node metastasis. Patients and methods: Eighty patients with non-small cell lung cancer (NSCLC) who underwent positron emission tomography/computed tomography were enrolled in the study. The FDG uptake in the primary tumor was compared for the different N staging groups and further correlation was performed. The degree of FDG uptake in the primary tumor and other possible variables related to the incidence of lymph node metastasis were examined by univariate and logistic multivariate analysis. FDG uptake was quantitated using the maximum standardized uptake value (SUVmax). Results: Statistically significant differences were found in the SUVmax of the primary tumors among different N staging groups (F = 4.124, P = 0.023), and the correlation between them was also statistically significant (r = 0.438, P = 0.000). Univariate analysis showed that blood tumor markers, primary tumor size, histologic grade, and SUVmax of the primary tumor were significantly associated with lymph node involvement. Logistic multivariate analysis showed that blood tumor makers and SUVmax of primary tumor might be considered as significant predictive factors for lymph node metastasis in patients with NSCLC. Conclusion: Our results show that there is a significant relationship between the SUVmax of the primary tumor and the pathologic N stage of NSCLC. FDG uptake by the primary tumor may be an independent predictor of regional lymph node metastasis in patients with NSCLC.

18F-FDG PET and PET/CT in Burkitt's lymphoma

Objective To explore the value of 18F fluorodeoxy-glucose (FDG) positron emission tomography (PET) in Burkitt's lymphoma. Methods All Burkitt's lymphoma patients referred for FDG PET or FDG PET/computed tomography (CT) exams at our institution from June 2003 to June 2006 were included. Selected patients were followed and clinical information was reviewed retrospectively. Results from FDG PET–PET/CT, as blindly reviewed by a consensus of two experienced readers, were compared with the status of the disease as determined by other laboratory, clinical and imaging exams and clinical follow-up. FDG PET–PET/CT results were classified as true positive or negative and false positive or negative. The degree of FDG uptake in the positive lesions was semiquantified as maximum standard uptake value (SUVmax). Results Fifty-seven FDG PET–PET/CT exams were done in 15 patients. Seven exams were done for initial staging, 8 during and 14 after the completion of therapy, and 28 for disease surveillance. For nodal disease FDG PET–PET/CT was true positive in 8, true negative in 47 and false positive in 2 exams (sensitivity 100%, specificity 96%). For extranodal disease FDG PET–PET/CT was true positive in 6, true negative in 48 and false positive in 3 exams (sensitivity 100%, specificity 94%). The mean SUVmax for the positive nodal lesions was 15.7 (range 6.9–21.7, median 18.5) and for extranodal lesions was 14.2 (range 6.2–24.3, median 12.4). Conclusions FDG PET–PET/CT is sensitive for the detection of viable disease in Burkitt's lymphoma. Affected areas demonstrated high degree of uptake that was reversible upon successful implementation of treatment.

Different Degree of FDG Uptake of Non-Small Cell Lung Cancer in PET-CT: What Dose It Imply?

Purpose: To examine the degree of fluorodeoxyglucose (FDG) uptake in non small cell lung cancers (NSCLCs) and its implications according to the cell type, tumor differentiation, size and stage. Materials and Methods: From February 2004 to February 2008, 161 patients (117 males, 44 Females) with surgically proven NSCLCs who underwent preoperative FDG positron emission tomography (PET) and curative surgery (stage I-IIIA) were enrolled in this study. The degree of FDG uptake of NSCLCs was evaluated retrospectively by measuring the maximum standard uptake values (max SUVs) in PET-CT according to the cell type, tumor differentiation, size and stage. Results: Squamous cell carcinomas (SCCs, n=75) had higher max SUVs than the adenocarcinomas (ADCs, n=86) (p

The Value of [18F]Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Extranodal Natural Killer/T—Cell Lymphoma

PurposeTo our knowledge, there are no published data pertinent to the use of [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in patients with natural killer (NK)/T—cell lymphoma. The purpose of this study was to assess the value of FDG PET/CT in this aggressive type of non-Hodgkin lymphoma. Patients and MethodsAll patients with NK/T-cell lymphoma referred for FDG PET/CT at our institution from July 2001 to July 2006 were retrospectively studied. PET/CT examinations were blindly reviewed by 2 experienced readers. The results were compared with the status of the disease, which was determined after evaluation of biopsy, laboratory, clinical and conventional imaging examination, and follow-up results. PET/CT results were thereby classified as true-positive, true-negative, false-positive, or false-negative. The degree of FDG uptake in the positive lesions was semiquantified using maximum standard uptake value (SUVmax). ResultsTwenty-one PET/CT examinations were performed in 10 patients with NK/T-cell lymphoma. For nasal disease, PET/CT was true-positive in 5 cases, true-negative in 15 cases, and positive but unconfirmed in 1 case. For extranasal disease, PET/CT was true-positive in 3 cases, true-negative in 16 cases, and false-negative in 2 cases. The mean SUVmax in PET-positive lesions in nasal cavities or paranasal sinuses was 16 gm/mL (range, 5–25 gm/mL; median, 19.3 gm/mL). In extranasal disease, the mean SUVmax was 10.9 gm/mL (range, 4.6–34.1 gm/mL; median, 5.6 gm/mL). ConclusionViable NK/T-cell lymphoma is intensely FDG hypermetabolic. PET/CT appears to be sensitive for the detection of disease in the nasopharynx and, to a lesser extent, in extranasal sites.

Predictive and prognostic value of FDG-PET.

The predictive and prognostic value of fluorodeoxyglucose (FDG)-positron emission tomography (PET) in non-small-cell lung carcinoma, colorectal carcinoma and lymphoma is discussed. The degree of FDG uptake is of prognostic value at initial presentation, after induction treatment prior to resection and in the case of relapse of non-small cell lung cancer (NSCLC). In locally advanced and advanced stages of NSCLC, FDG-PET has been shown to be predictive for clinical outcome at an early stage of treatment. In colorectal carcinoma, limited studies are available on the prognostic value of FDG-PET, however, the technique appears to have great potential in monitoring the success of local ablative therapies soon after intervention and in the prediction and evaluation of response to radiotherapy, systemic therapy, and combinations thereof. The prognostic value of end-of treatment FDG-PET for FDG-avid lymphomas has been established, and the next step is to define how to use this information to optimize patient outcome. In Hodgkin's lymphoma, FDG-PET has a high negative predictive value, however, histological confirmation of positive findings should be sought where possible. For non-Hodgkin's lymphoma, the opposite applies. The newly published standardized guidelines for interpretation formulates specific criteria for visual interpretation and for defining PET positivity in the liver, spleen, lung, bone marrow and small residual lesions. The introduction of these guidelines should reduce variability among studies. Interim PET offers a reliable method for early prediction of long-term remission, however it should only be performed in prospective randomized controlled trials. Many of the diagnostic and management questions considered in this review are relevant to other tumour types. Further research in this field is of great importance, since it may lead to a change in the therapeutic concept of cancer. The preliminary findings call for systematic inclusion of FDG-PET in therapeutic trials to adequately position FDG-PET in treatment time lines.

Role of Positron Emission Tomography in Lymphoma

Positron emission tomography (PET) scanning, particularly using [F]fluorodeoxyglucose (FDG), has recently emerged as a powerful functional imaging tool for assessment of patients with Hodgkin’s disease and nonHodgkin’s lymphoma (NHL). Numerous investigations have been reported on its use for staging, restaging, and monitoring tumor response of lymphoma, with only a few exploring its value in predicting the tumor’s malignancy grade. In this issue of the Journal of Clinical Oncology, Schoder et al seek to determine whether the intensity of FDG uptake measured using the standardized uptake value (SUV) could differentiate between indolent and aggressive NHL. The SUV is a semiquantitative measure of the degree of FDG uptake, which may be conceptualized as the ratio between the tumoral concentration of tracer and its concentration in the entire body if the tracer were evenly distributed throughout. Because of its simplicity, this parameter is widely utilized both in the research setting and in clinical practice. In their study of 97 patients with NHL, Schoder et al concluded that the SUV is lower in indolent than in aggressive NHL, that patients with an SUV 10 have a high likelihood of aggressive NHL, and that this information may be helpful if there is discordance between biopsy and clinical behavior. These findings clearly have implications in treatment planning and prognosis. While the study by Schoder et al is the largest to date to attempt to distinguish between indolent and aggressive NHLs based on the SUV, the findings are not very different from those of previously reported smaller studies. Similar to those previous studies, a considerable overlap in the SUVs was found between indolent and aggressive NHL, with a relatively wide range of SUVs observed even within the same histologic subtype. This variability could have been even greater had the authors determined the SUVs for all well-delineated tumor lesions in each patient rather than only for the most intense lesion because of the known intrapatient variability in SUV in patients with NHL and other cancer types. Despite this overlap, two conclusions may be drawn reasonably from the data. First, an SUV 13 in the most intense lesion indicates a high likelihood of aggressive histology, while an SUV of 6 is very likely associated with indolent histology. Second, these upper and lower cutoff SUVs provide relatively high accuracy in grading NHL in only approximately 55% of patients, because only approximately 58% of patients with biopsy-proven aggressive histology had an SUV 13, and slightly less than 50% of those with indolent histology had an SUV 6. Consequently, approximately 45% of patients remain in a gray zone between the SUVs of 6 and 13, where the overlap is so pronounced that it practically precludes a justifiable degree of confidence in grading NHL. The adverse effect of this overlap becomes apparent when examining the results of the receiver operating characteristic (ROC) analysis used to determine optimum cutoff SUV that distinguishes indolent from aggressive histologies: this optimum cutoff SUV of 10, although associated with a fair balance of sensitivity and specificity, resulted in a 29% misclassification rate for aggressive NHL and a 19% misclassification rate for indolent NHL. The latter may result in overtreatment of a significant fraction of patients with indolent lymphoma. Conversely, misclassification of almost one third of patients with aggressive lymphoma may result in their undertreatment, which cannot be justified considering the potentially curable nature of their disease. The moderate sensitivity and specificity of the cutoff SUV of 10 needs to be further evaluated in light of the fact that this value was derived post hoc, potentially resulting in an overestimation of its diagnostic accuracy. However, the findings in the 22 patients in whom the biopsy was taken from a site other than that with the most intense FDG uptake could serve as an initial test for the performance of this cutoff in an independent, albeit small, cohort of JOURNAL OF CLINICAL ONCOLOGY E D I T O R I A L VOLUME 23 NUMBER 21 JULY 2

Do high glucose levels have differential effect on FDG uptake in inflammatory and malignant disorders?

The association of hyperglycaemia with reduced fluorodeoxyglucose (FDG) uptake by tumour cells is well established. Therefore, it is standard practice that all patients must fast for at least several hours prior to FDG positron emission tomography (PET) imaging. However, the effect of hyperglycaemia on FDG uptake by inflammatory and infectious lesions is unknown. The aim of this study was to investigate this important issue. For in vitro studies human mononuclear cells were isolated from 12 normal volunteers and FDG uptake was determined in medium containing differing concentrations of glucose. FDG uptake by human mesothelioma cells was also measured for comparison. For studies involving patients, 416 FDG PET scans of patients with confirmed malignancy (n=321) or benign lesions (n=95) were reviewed retrospectively. The relationship between serum glucose level and FDG uptake by the lesions was assessed utilizing the standardized uptake value (SUV) technique. In the in vitro studies, while FDG uptake by mesothelioma cells decreased as glucose concentration increased, there was no differential uptake of FDG uptake by mononuclear cells at glucose concentrations less than 250 mg x dl(-1). In clinical patients, FDG uptake by malignant lesions was slightly, but negatively affected by serum glucose level (r= -0.21, P<0.01) (glucose range 49-187 mg x dl(-1)). In contrast, FDG uptake by inflammatory lesions was positively associated with serum glucose level (r=0.43, P<0.01) (glucose range 54-215 mg x dl(-1)). While the degree of FDG uptake is primarily influenced by the nature of the underlying lesion, serum glucose concentration appears to have a small effect on FDG uptake, which differs between malignant disorders and inflammatory processes. Our data suggest that below a certain level, elevated glucose concentration might not have a negative effect on FDG uptake in inflammatory cells, contrary to that observed in malignant disorders.