F-18 FDG PET detection of a medullary thyroid carcinoma in a patient with metastatic colonic cancer; literature review

Objective

We report a case of a medullary thyroid carcinoma discovered by F-18 fluorodeoxyglucose-positron emission tomography (F-18 FDG PET).

Patient and methods

A 73-year-old man with a history of surgical removal of sigmoid colon cancer underwent F-18 FDG PET to search for distant metastases and / or local recurrence because of elevated CEA level and new episode of occlusion. F-18 FDG PET images showed increased focal FDG uptake in the right lobe of the thyroid. Thyroid ultrasound showed one thyroid nodule in each lobe.

Results

The fine needle aspiration result was suspicious and calcitonin level was elevated. The subject underwent thyroidectomy without lymph node dissection. The pathology showed a 14 mm medullary thyroid carcinoma. There was no germline mutation of RET.

Conclusions

F-18 FDG PET can detect primitive or secondary malignant thyroid tumors. Thus, thyroid incidentaloma revealed by 18 FDG PET uptake always necessitates careful evaluation.     

<Superscript>18</Superscript>F-FDG PET in the detection of extrahepatic metastases from hepatocellular carcinoma

Background Positron emission tomography (PET) with ¹⁸F-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) is useful in detecting distant metastases from a variety of malignancies. However, its efficiency in detecting distant metastases from hepatocellular carcinoma (HCC) has not been investigated. The aim of this study was to evaluate the usefulness of ¹⁸F-FDG PET for the detection of extrahepatic metastases from HCC.Methods Nineteen patients suspected of having extrahepatic HCC underwent ¹⁸F-FDG PET. Fourteen patients (group A) had extrahepatic lesions, which were detected by conventional studies. In five patients (group B), conventional imaging showed no extra- or intrahepatic lesions, but the tumor marker levels were elevated. The PET results were compared with those obtained by histopathology or by clinical follow-up.Results The detection rate of ¹⁸F-FDG PET was 83% (24 of 29 metastases) for extrahepatic metastases larger than 1cm in greatest diameter and 13% (1 of 8 metastases) for lesions less than or equal to 1cm. PET revealed two bone metastases not depicted by bone scan, and detected the nodal metastasis and intestinal metastases inconclusive on computed tomography. Extrahepatic lesions were resected in 5 patients of group A on the basis of PET findings. In all patients of group B, PET results were true negative for extrahepatic metastases, but HCCs were detected in the liver within 4 months in 4 patients. These were no false-positive lesions in either group.Conclusions This preliminary study suggested that ¹⁸F-FDG PET could provide additional information and contribute to the management of HCC patients suspected of having extrahepatic metastases.     

F-18 FDG PET/CT in the assessment of patients with unexplained CEA rise after surgical curative resection for colorectal cancer

Purpose

We evaluated the role of quantitative assessment by maximum standardized uptake value (SUVmax) on F-18 fluorodeoxyglucose [F-18]FDG positron emission tomography/computed tomography (PET/CT) in stratifying colorectal cancer (CRC) patients with unexplained carcinoembryonic antigen (CEA) rise after surgical curative resection.

Material and methods

Forty asymptomatic patients (mean age, 64?±?12 years) with previous CRC and current serum CEA levels >5 ng/ml underwent [F-18] FDG PET/CT 13?±?3 months after complete surgical resection. The SUVmax was registered on anastomosis and peri-anastomotic tissue lesions, if present. The patients were followed for 24?±?9 months thereafter. Re-intervention, evidence of newly discovered distant metastases, and death were recognized as main events and constituted surrogate end points. The receiver-operator-curve (ROC) analysis was performed to estimate the optimal SUVmax cut-off to predict patients at high risk of main events. PET/CT results were then related to disease outcome (overall survival; OS).

Results

The mean SUVmax at the anastomotic site was 6.2?±?3 (range 2.6–15). At multivariate logistic regression analysis, the anastomotic SUVmax remained as the only significant contributor to the prediction of the events (p?=?0.004; OR 1.97). The ROC analysis recognized that the optimal threshold of SUVmax to differentiate patients was 5.7. A worse OS was observed in patients presenting with a SUVmax greater than 5.7 as compared to those having lesser (median survival: 16 vs. 31 months; p?=?0.002).

Conclusions

The quantitative assessment by SUVmax on [F-18]FDG PET/CT may be helpful in patients presenting with unexplained CEA rise after curative resection of CRC, by identifying those at risk of main events.     

Diagnostic role of radiolabelled choline PET or PET/CT in hepatocellular carcinoma: a systematic review and meta-analysis

The role of fluorine-18-fluorodeoxygluose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in hepatocellular carcinoma (HCC) has not been firmly established yet and its sensitivity has been reported to be in the range of 40–60 %. Because of this relatively low sensitivity alternative tracers have been proposed. The aim of our review is to analyse the literature data on the diagnostic role of ¹⁸F/¹¹C-choline PET/CT in the evaluation of HCC. A comprehensive computer literature search of PubMed/MEDLINE, Embase and Scopus databases was conducted to find relevant published articles about the role of whole-body ¹⁸F-choline or ¹¹C-choline PET or PET/CT in patients with HCC. Furthermore, a meta-analysis about the detection rate of this method in HCC was performed. Six articles were included in this systematic review and discussed. The meta-analysis of five out of six articles showed a DR of 84 % (95 % CI 79–89 %). The DR increased when poorly differentiated HCC was excluded from the analysis. Radiolabelled choline PET or PET/CT could be a valuable tool in detecting HCC and it is better than ¹⁸F-FDG PET/CT, especially in well to moderately differentiated lesions; on the other hand, poorly differentiated and higher-stage HCC could be better evaluated with ¹⁸F-FDG and dual tracer imaging should be considered and could be potentially useful to increase accuracy.     

Usefulness of 18F-fluorodeoxyglucose positron emission tomography in differential diagnosis and staging of cholangiocarcinomas

Background and Aim: ¹⁸F‐Fluoro‐2‐deoxy‐d ‐glucose positron emission tomography (¹⁸FDG‐PET) is promising for diagnosis and treatment of various malignancies. The aim of this study was to evaluate the clinical usefulness of ¹⁸FDG‐PET in differential diagnosis and staging of cholangiocarcinomas according to the intrahepatic, perihilar and common bile duct lesions and to compare with computerized tomography (CT) scan. Methods: From January 2000 to September 2003, 54 patients with suspected cholangiocarcinoma underwent abdominal CT scan and ¹⁸FDG‐PET within a 2‐week period. The PET images were analyzed visually and semiquantitatively. Results: The overall accuracy of ¹⁸FDG‐PET for discriminating malignant diseases of bile duct from benign conditions was slightly higher than that of CT scan (88.9% vs 81.5%). The sensitivity of ¹⁸FDG‐PET in perihilar cholangiocarcinoma was lower than the value of intrahepatic and common bile duct cancers (83.3% vs 91.3%, 90.9%); moreover, in cases of perihilar cancer, the sensitivity of ¹⁸FDG‐PET was lower than that of CT scans (83.3% vs 91.7%). ¹⁸FDG‐PET detected nine distant metastatic lesions not found by other imaging studies and excluded two patients who potentially had resectable condition in other imaging studies from unnecessary laparotomy. Conclusion: The clinical usefulness of ¹⁸FDG‐PET in differential diagnosis of bile duct cancers is related to the site of primary disease. Although it is a helpful method for differential diagnosis especially in cases of intrahepatic and common bile duct cancers, ¹⁸FDG‐PET can not provide confirmative clues in perihilar cholangiocarcinoma. ¹⁸FDG‐PET may hold promise in the detection of hidden distant metastasis and can play an additional role in the evaluation of resectability. ¹⁸FDG‐PET can be complementary to CT scan in diagnosing and staging of cholangiocarcinoma.     

Evaluation of tumor growth in vivo in a rat model of liver metastasis,using a newly devised index obtained by positron emission tomography with [18F] FDG

Background/Purpose

[¹⁸F] fluorodeoxyglucose-positron emission tomography (FDG-PET) is regarded as a unique imaging modality, because the images reflect tumor activity. This characteristic of PET encouraged us to use it to develop a novel method of quantitatively measuring liver metastasis viability.

Methods

F344 rats were injected with rat colon adenocarcinoma cells (RCN-9 cell line) via the portal vein, and some of them were treated with 5-fluorouracil (5-FU). Tumor growth and tumor activity were measured by PET. We used a tumor viability index (TVI) to evaluate changes in tumor activity and to quantitatively evaluate tumor proliferation activity, instead of using the standardized uptake value (SUV) of the tumor tissue. The TVI was compared with the number of tumor nodules and the proliferating cell nuclear antigen (PCNA) index 28 days after RCN-9 cell inoculation.

Results

[¹⁸F] FDG uptake by the liver tumors was measured by PET, and the TVI was found to increase as the tumor nodules increased in number and size. The TVI values in the experimental model represented the viability of tumors suppressed by chemotherapy, and the values were significantly correlated with the number of nodules and the PCNA index.

Conclusions

The TVI was concluded to be superior to the SUV, the commonly used indicator, for evaluating tumor growth, especially that of multiple, small tumors.

     

Use of positron emission tomography with methyl‐11C‐choline and 2‐18F‐fluoro‐2‐deoxy‐D‐glucose in comparison with magnetic resonance imaging for the assessment of inflammatory proliferation of synovium

Objective

To compare positron emission tomography (PET) and magnetic resonance imaging (MRI) in the evaluation of inflammatory proliferation of synovium.

Methods

Ten patients (mean ± SD age 36 ± 13 years) with inflammatory joint disease and with clinical signs of inflammation of the joint were studied. A new tracer for cellular proliferation, methyl‐¹¹C‐choline (¹¹C‐choline), and a widely used tracer for the detection of inflammation and cancer, 2‐¹⁸F‐fluoro‐2‐deoxy‐D ‐glucose (¹⁸F‐FDG), were applied for PET imaging, and the results were compared with the findings from gadolinium diethylenetriaminepentaacetic acid–enhanced MR images. The uptake of ¹¹C‐choline and ¹⁸F‐FDG in the inflamed synovium was measured and expressed as the standardized uptake value (SUV) and the kinetic influx constant (K_i) obtained from graphic analysis, and these values were compared with quantitative values on MRI. Synovial volumes were measured on the coronal contrast‐enhanced T1‐weighted MR images using the standard software of the MR imager.

Results

All patients showed high accumulation of both ¹¹C‐choline and ¹⁸F‐FDG at the site of arthritic changes, where quantification of the tracer uptake was performed. The SUV of ¹¹C‐choline was 1.5 ± 0.9 gm/ml (mean ± SD; n = 10) and the SUV of ¹⁸F‐FDG was 1.9 ± 0.9 gm/ml (n = 10) (P = 0.017). The K_i of ¹¹C‐choline (mean ± SD 0.048 ± 0.042 minute⁻¹) was 8‐fold higher than the K_i of ¹⁸F‐FDG (0.006 ± 0.003 minute⁻¹) (P = 0.009). Both the uptake of ¹¹C‐choline and the uptake of ¹⁸F‐FDG correlated highly with the volume of synovium; the highest correlation was observed with the K_i of ¹¹C‐choline (r = 0.954, P < 0.0001).

Conclusion

In the use of PET scans,¹¹C‐choline can be regarded as a promising tracer for quantitative imaging of proliferative arthritis changes. Nevertheless, subsequent prospective studies with larger numbers of patients are necessary to further characterize the relationship between the findings on PET imaging and the clinical and functional measures of inflammation.

     

18FDG uptake in oesophageal adenocarcinoma: linking biology and outcome

Purpose Variable uptake of ¹⁸FDG has been noticed in positron emission tomography (PET) studies of patients with oesophageal adenocarcinoma. The aim of the present study was to investigate biological parameters involved in ¹⁸FDG uptake in oesophageal adenocarcinoma for selection of patients with increased ¹⁸FDG uptake and prediction of prognostic value of ¹⁸FDG PET. Patients and methods Preoperative PET scans were performed in 26 patients with histologically proven oesophageal adenocarcinoma. ¹⁸FDG uptake was semiquantitatively measured by SUV_BSAg. Tumour sections were stained by immunohistochemistry for angiogenic markers (VEGF, CD31), glucose transporter-1 (Glut-1), hexokinase (HK) isoforms, for proliferation marker (Ki67), for macrophage marker (CD68) and for apoptosis marker (cleaved caspase-3). Cell densities, differentiation grade, degree of necrosis and mucus, T-stage and tumour size were assessed. In addition follow-up was analysed. Results No association was found between ¹⁸FDG uptake and angiogenic markers. In contrast, a significant correlation was found between ¹⁸FDG uptake and Glut-1 expression. No correlations were found between ¹⁸FDG uptake and HK isoforms, Ki67 or cleaved caspase-3. Also, no correlations were found between ¹⁸FDG uptake and cell density, differentiation grade, CD68, mucus and necrosis. However, there was a significant correlation between ¹⁸FDG uptake and tumour size and between ¹⁸FDG uptake and tumour recurrence. Conclusions Glut-1 expression and tumour size seem parameters associated with ¹⁸FDG uptake in patients with biopsy proven oesophageal adenocarcinoma, and may be used to select oesophageal cancer patients in whom ¹⁸FDG-PET is of diagnostic value and may predict disease outcome.     

Quantification of liver glucose metabolism by positron emission tomography: validation study in pigs

BACKGROUND & AIMS: The liver is inaccessible to organ balance measurements in humans. To validate [(18)F]fluorodeoxyglucose ([(18)F]FDG) positron emission tomography (PET) in the quantification of hepatic glucose uptake (HGU), we determined [(18)F]FDG modeling parameters, lumped constant (LC), and input functions (single arterial versus dual). METHODS: Anesthetized pigs were studied during fasting (n = 6), physiologic (n = 4), and supraphysiologic (n = 4) hyperinsulinemia. PET was performed with C(15)O (blood pool) and [(18)F]FDG (glucose uptake). 6,6-Deuterated glucose ([(2)H]G) was coinjected with [(18)F]FDG and blood collected from the carotid artery and portal and hepatic veins to compute LC as ratio between tracers fractional extraction. HGU was estimated from PET images and ex vivo from high-performance liquid chromatography measurements of liver [(18)F]FDG versus [(18)F]FDG-6-phosphate and [(18)F]-glycogen. Endogenous glucose production was measured with [(2)H]G and hepatic blood flow by flowmeters. RESULTS: HGU was increased in hyperinsulinemia versus fasting (P < .05). Fractional extraction of [(18)F]FDG and [(2)H]G was similar (not significant), intercorrelated (r = 0.98, P < .0001), and equally higher during hyperinsulinemia than fasting (P 0.95, P < .0001), with a modest underestimation of HGU by the former. CONCLUSIONS: [(18)F]FDG-PET-derived parameters provide accurate quantification of HGU and estimates of liver perfusion and glucose production. In the liver, LC of [(18)F]FDG is nearly unitary. Using a single arterial input introduces only a small error in estimation of HGU.     

Determination of optimum periods between onset of suspected acute myocarditis and F-fluorodeoxyglucose positron emission tomography in the diagnosis of inflammatory left ventricular myocardium

Purpose

To determine optimum periods for ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) examination in subjects with suspected acute myocarditis, we compared ¹⁸F-FDG PET with endomyocardial biopsy (EMB) using the latest definition of ¹⁸F-FDG PET for inflammatory left ventricular (LV) myocardium.

Materials and methods

Retrospective analysis of 29 subjects (18 male, 48 ± 18 years) who have symptoms or LV dysfunction underwent both ¹⁸F-FDG PET (Advance NXi, GE-Healthcare) under fasting conditions and EMB from LV posterior wall within 3 months.

Results

When we defined ¹⁸F-FDG PET positive inflammatory LV posterior wall as ‘focal on diffuse’ pattern, sensitivity, specificity, and positive predictive values (PPV), and negative predictive values (NPV) of ¹⁸F-FDG PET for detecting active inflammatory LV posterior wall compared with EMB were 46.2, 81.3, 66.7, and 65.0%, respectively. Receiver operating characteristic curve of periods (days) between onset of clinically suspected acute myocarditis and performance of ¹⁸F-FDG PET for detecting inflammatory LV posterior wall demonstrated 17 days as a best cut off values with area under the curve (0.497, P = 0.982) with sensitivity = 21.1% and specificity = 100%. Sensitivity, specificity, PPV and NPV of ¹⁸F-FDG PET for detecting inflammatory LV posterior wall on EMB were all 100% when ¹⁸F-FDG PET was performed at 1–14 days after onset of suspected acute myocarditis.

Conclusions

In our definition, ¹⁸F-FDG PET showed excellent agreement with EMB for detecting active inflammatory LV posterior wall in subjects with clinically suspected active acute myocarditis. If possible, ¹⁸F-FDG PET should be performed within 14 days after the onset to maintain high diagnostic accuracy compared with EMB.     

Relation Between Contractile Reserve and Positron Emission Tomographic Patterns of Perfusion and Glucose Utilization in Chronic Ischemic Left Ventricular Dysfunction: Implications for Identification of Myocardial Viability

Objectives. This study sought to determine the incidence and extent of dobutamine-induced contractile reserve in myocardial regions characterized by classical and new positron emission tomographic (PET) patterns in patients with chronic ischemic left ventricular dysfunction.

Background. PET is considered the most accurate method for assessment of myocardial viability, which is traditionally identified by perfusion–metabolism mismatch.

Methods. In 23 patients, segmental wall thickening expressed by four echocardiographic scores at rest and during low dose (5 and 10 μg/kg body weight per min) dobutamine infusion and regional myocardial uptake of potassium-38 and fluorine-18 fluorodeoxyglucose (F-18 FDG) during glucose clamp were compared in 16 corresponding segments.

Results. Of a total of 368 segments, data analysis focused on 214 (58%) dyssynergic segments at baseline. Contractile reserve was identified with increasing incidence according to the six following PET patterns: 1) diminished perfusion and moderate reduction of F-18 FDG uptake (3 [11%] of 28 segments); 2) proportional reduction of perfusion and F-18 FDG uptake (10 [23%] of 43 segments); 3) perfusion–metabolism mismatch (19 [46%] of 41 segments); 4) preserved perfusion but moderate reduction of F-18 FDG uptake (13 [46%] of 27 segments); 5) preserved perfusion and F-18 FDG uptake (37 [59%] of 63 segments) compared with our normal database; and 6) normal perfusion but absolute increased F-18 FDG uptake (8 [73%] of 11 segments). In the latter category, only 7 of 24 segments had normal rest function. In dyssynergic segments with F-18 FDG uptake ≥50% supplied by vessels with ≥75% stenosis, improvement in contractility during dobutamine correlated with the presence of collateral channels.

Conclusions. Myocardial regions with the traditional mismatch pattern of viability show contractile reserve in slightly <50%. In segments with moderate reduction of F-18 FDG uptake, the contractile response to dobutamine is linked to the level of rest perfusion. Most segments with preserved perfusion and increased F-18 FDG uptake have impaired rest function, but contractile reserve is still present. These data suggest that in chronic ischemic left ventricular dysfunction, myocardial hibernation is a heterogeneous condition.     

Diagnosis and evaluation of gastric cancer by positron emission tomography

Gastric cancer is the second leading cause of cancer mortality worldwide.The diagnosis of gastric cancer has been significantly improved with the broad availability of gastrointestinal endoscopy.Effective technologies for accurate staging and quantitative evaluation are still in demand to merit reasonable treatment and better prognosis for the patients presented with advanced disease.Preoperative staging using conventional imaging tools,such as computed tomography(CT)and endoscopic ultrasonography,is inadequate.Positron emission tomography(PET),using 18F-fluorodeoxyglucose(FDG)as a tracer and integrating CT for anatomic localization,holds a promise to detect unsuspected metastasis and has been extensively used in a variety of malignancies.However,the value of FDG PET/CT in diagnosis and evaluation of gastric cancer is still controversial.This article reviews the current literature in diagnosis,staging,response evaluation,and relapse monitoring of gastric cancer,and discusses the current understanding,improvement,and future prospects in this area.     

Clinical implication of F-18 FDG PET/CT in patients with secondary hemophagocytic lymphohistiocytosis

The contribution that F-18 fluoro-2-deoxyglucose positron emission tomography/computed tomography (F-18 FDG) PET/CT makes to the diagnosis of malignancy in patients with hemophagocytic lymphohistiocytosis (HLH) is still uncertain. The aim of this study was to evaluate the diagnostic performance of F-18 FDG PET/CT for the detection of underlying malignancy, to investigate the correlation between PET and laboratory parameters, and to identify prognosis-related factors in patients with secondary HLH. We enrolled 14 patients who were diagnosed with HLH and referred for F-18 FDG PET/CT to exclude malignancy. The diagnostic performance of F-18 FDG PET/CT for malignancy detection was assessed. The correlations between PET and laboratory parameters were determined. The prognostic significance of the following factors was evaluated: PET and laboratory parameters, age in years, presence of underlying malignancy, and fever and splenomegaly. Six of the 14 patients had malignancies (four with lymphoma, one with multiple myeloma, and one with colonic malignancy). Sensitivity, specificity, and diagnostic accuracy of F-18 FDG PET/CT for malignancy detection were 83, 62.5, and 71.4 %, respectively. F-18 FDG uptake in the bone marrow and spleen was positively correlated with neutrophil count and C-reactive protein. All of the PET parameters, but none of the clinical or laboratory parameters, were significantly associated with patient outcome, as determined by univariate analysis. Given the small sample size, F-18 FDG PET/CT was useful for detecting underlying malignancy, and PET parameters correlated with laboratory parameters that reflected inflammatory status. F-18 FDG PET/CT might provide prognostic information for the management of patients with secondary HLH.     

18F‐Fluorodeoxyglucose (FDG)‐PET features of focal nodular hyperplasia (FNH) of the liver

Abstract: Aim: The aim of this paper is to describe the imaging pattern of focal nodular hyperplasia (FNH) by ¹⁸F‐fluorodeoxyglucose (18F‐FDG) positron emission tomography (PET). Methods: Eight consecutive asymptomatic patients with histologic proof of FNH underwent 18F‐FDG PET imaging. The lesions were found incidentally. The 18F‐FDG PET imaging was performed with a dedicated PET tomograph after intravenous injection of 300–370 MBq 18F‐FDG. The 18F‐FDG accumulation in the lesions was (semi)quantified by calculating the standardized uptake value (SUV) and SUV has been corrected for the lean body mass (LBM). Eight patients with liver metastases spread from melanoma (n=2) and colorectal carcinoma (n=6) served as controls. The size of the FNH lesions and of the control group ranged from 2.0 to 8.5 cm (mean 4.83 cm±2.37) and from 1.5 to 6 cm (mean 3.28±1.52), respectively. Results: While in malignant liver lesions the accumulation of 18F‐FDG was significantly increased, all FNH lesions showed normal or even decreased accumulation of 18F‐FDG. In FNH lesions, SUV ranged between 1.5 and 2.6 (mean 2.12±0.38), whereas all liver metastases showed an increased SUV ranging between 6.20 and 16.00 (mean 10.07±3.79). The SUV corrected for LMB (SUV_LBM) was similar to the SUV and ranged between 0.9 and 2.2 (mean 1.81±0.41) for FNH and between 5.9 and 16.3 (mean 9.15±4.03), respectively. Conclusion: In contrast to liver metastases, there is no increased glucose metabolism in FNH in vivo. The imaging feature of FNH by 18F‐FDG‐PET imaging is not specific for FNH; however, it may be helpful to differentiate FNH from liver metastases in cancer patients if radiological methods are not diagnostic.     

Validation of [<Superscript>18</Superscript>F]fluorodeoxyglucose and positron emission tomography (PET) for the measurement of intestinal metabolism in pigs,and evidence of intestinal insulin resistance in patients with morbid obesity

Aims/hypothesis

The role of the intestine in the pathogenesis of metabolic diseases is gaining much attention. We therefore sought to validate, using an animal model, the use of positron emission tomography (PET) in the estimation of intestinal glucose uptake (GU), and thereafter to test whether intestinal insulin-stimulated GU is altered in morbidly obese compared with healthy human participants.

Methods

In the validation study, pigs were imaged using [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) and the image-derived data were compared with corresponding ex vivo measurements in tissue samples and with arterial–venous differences in glucose and [¹⁸F]FDG levels. In the clinical study, GU was measured in different regions of the intestine in lean (n?=?8) and morbidly obese (n?=?8) humans at baseline and during euglycaemic hyperinsulinaemia.

Results

PET- and ex vivo-derived intestinal values were strongly correlated and most of the fluorine-18-derived radioactivity was accumulated in the mucosal layer of the gut wall. In the gut wall of pigs, insulin promoted GU as determined by PET, the arterial–venous balance or autoradiography. In lean human participants, insulin increased GU from the circulation in the duodenum (from 1.3?±?0.6 to 3.1?±?1.1 μmol [100 g]^?1?min^?1, p?<?0.05) and in the jejunum (from 1.1?±?0.7 to 3.0?±?1.5 μmol [100 g]^?1?min^?1, p?<?0.05). Obese participants failed to show any increase in insulin-stimulated GU compared with fasting values (NS).

Conclusions/interpretation

Intestinal GU can be quantified in vivo by [¹⁸F]FDG PET. Intestinal insulin resistance occurs in obesity before the deterioration of systemic glucose tolerance.

     

18 F-fluorodeoxyglucose positron emission tomography to evaluate recurrent gastric cancer: a systematic review and meta-analysis

Background and Aim: We aimed to explore the role of the diagnostic accuracy of ¹⁸F‐fluorodeoxyglucose positron emission tomography (¹⁸F‐FDG PET) in detecting recurrent gastric cancer through a systematic review and meta‐analysis. Methods: The MEDLINE, EMBASE, Cancerlit, and Cochrane Library database, from January 2001 to July 2011, were searched for studies evaluating the diagnostic performance of ¹⁸F‐FDG PET in detecting recurrent gastric cancer. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR+ and LR?), and constructed summary receiver operating characteristic curves. We also compared the performance of ¹⁸F‐FDG PET with computed tomography (CT) by analyzing studies that had also used these diagnostic methods on the same patients. Results: Across nine studies (526 patients), the overall sensitivity of ¹⁸F‐FDG PET was 0.78 (95% confidence interval [CI]: 0.68–0.86), and the overall specificity was 0.82 (95% CI: 0.76–0.87). Overall, LR+ was 3.52 (95% CI: 2.68–4.63) and LR? was 0.32 (95% CI: 0.22–0.46). In studies in which both ¹⁸F‐FDG PET and other diagnostic tests were performed, the sensitivity and specificity of ¹⁸F‐FDG PET were 0.72 (95% CI: 0.62–0.80) and 0.84 (95% CI: 0.77–0.90), respectively; of contrast CT, they were 0.74 (95% CI: 0.64–0.83) and 0.85 (95% CI: 0.78–0.90), respectively; and of combined PET and CT, they were 0.75 (95% CI: 0.67–0.82) and 0.85 (95% CI 0.79–0.90), respectively. Study sensitivity was not correlated with the prevalence of recurrent gastric cancer. Conclusion: ¹⁸F‐FDG PET has good diagnostic performance in the overall evaluation of recurrent gastric cancer, but still has some limited performance compared with contrast CT. ¹⁸F‐FDG PET combined with CT might improve the diagnostic performance in detecting recurrent gastric cancer.     

Advantages and limitations of 18-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography in the diagnosis of infective endocarditis

IntroductionThe early diagnosis of infective endocarditis (IE) is a medical challenge and a multidisciplinary approach is essential to improve its frequently fatal prognosis. Our goal was to evaluate the usefulness of [¹⁸F]2-fluoro-2-deoxy-d-glucose positron emission tomography (¹⁸F-FDG PET) in the diagnosis of this disease.Materials and MethodsWe prospectively assessed 43 patients (five female and 38 male) with clinical suspicion of IE between 2014 and 2017. All patients underwent transesophageal echocardiography (TEE) and an ¹⁸F-FDG PET scan, and the results were compared. A positive PET finding was defined as increased FDG uptake on cardiac valves or intracardiac devices.ResultsOut of 43 patients with suspected IE, the diagnosis was confirmed in 30 cases (79.7%). ¹⁸F-FDG PET was positive in 24 patients, with 19 showing FDG uptake on cardiac valves (two native and 17 prosthetic) and five on cardiac devices, being concordant with echocardiographic findings in 11 cases. ¹⁸F-FDG PET sensitivity was 80%, specificity 92%, positive predictive value (PPV) 96% and negative predictive value (NPV) 66%. Echocardiography presented sensitivity, specificity, PPV and NPV of 36%, 84%, 84% and 36%, respectively.Conclusions¹⁸F-FDG PET proved to be a sensitive technique with a high diagnostic value in patients with prosthetic valves and intracardiac devices and suspected IE. Its utility decreased dramatically in patients with suspected IE on native valves, in which TEE presented higher sensitivity and thus better diagnostic value.     

18F-labelled cardiac PET tracers: selected probes for the molecular imaging of transporters, receptors and proteases

Designated radiopharmaceuticals labelled with the prominent positron-emitter ¹⁸F can be defined as molecular imaging probes for the examination of cardiovascular diseases at the cellular and subcellular level. Such molecular imaging agents representing radioindicators or radiotracers offer the opportunity to non-invasively trace their path and fate in the living organism by the scintigraphic technique, positron emission tomography (PET). The glucose analogue [¹⁸F]FDG is a widespread PET tracer and one of the earliest examples of a PET molecular imaging probe feasible to in vivo visualise glucose utilisation by a metabolic trapping mechanism. This short review is focussed on selected established ¹⁸F-labelled PET tracers as well as ¹⁸F-labelled radioligands in development that show the potential of being probes for the in vivo molecular imaging of proteins relevant in cardiovascular diseases such as receptors (i.e. β-Adrenoceptors), transporters (i.e. NET and VMAT) and proteases (i.e. MMPs). K. Kopka and S. Wagner contributed equally to this work.     

Role of 18F‐FDOPA PET/CT imaging in endocrinology

¹⁸F‐FDOPA (6‐[18F]‐L‐fluoro‐L‐3, 4‐dihydroxyphenylalanine)‐based PET/CT imaging can be a useful tool for the detection of different neuroendocrine tumours (NETs). ¹⁸F‐FDOPA is taken up into the cells via the neutral amino acid transporter (LAT1/4F2hc). This transporter is also coupled to the mammalian target of rapamycin (mTOR) signalling pathway. ¹⁸F‐FDOPA PET/CT may be performed for confirmation of diagnosis of pheochromocytoma/paraganglioma, staging at initial presentation, restaging and follow‐up of patients. In SDHx‐related syndromes, ¹⁸F‐FDG PET/CT should be performed in addition to ¹⁸F‐FDOPA PET/CT. ¹⁸F‐FDOPA PET/CT is also invaluable in the detection staging/restaging of carcinoid tumours and has greater sensitivity as compared to somatostatin receptor scintigraphy. ¹⁸F‐FDOPA PET/CT can also distinguish between focal vs diffuse CHI. It is not as useful in adult hyperinsulinism due to increased background uptake, but the problem may be overcome with the help of premedication with carbidopa. It has limited use in pancreatic NETs. ¹⁸F‐FDOPA PET/CT is a good modality for detection of persistent and residual medullary thyroid cancer (MTC), but ¹⁸F‐FDG PET/CT may be needed in aggressive tumours. In summary, F‐DOPA PET/CT has widespread utility in the diagnosis of different neuroendocrine tumours.     

The role of 18F-FDOPA and 18F-FDG-PET in the management of malignant and multifocal phaeochromocytomas

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.