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Introduction: Dynamic positron emission tomography (PET) and the application of kinetic models can provide important quantitative information based on its temporal information. This however requires arterial blood sampling, which can be challenging to acquire. Nowadays, state-of-the-art PET/CT systems offer fully automated, whole-body (WB) kinetic modelling protocols using image-derived input functions (IDIF) to replace arterial blood sampling. Here, we compared the validity of an automatic WB kinetic model protocol to the reference standard arterial input function (AIF) for both clinical and research settings. Methods: Sixteen healthy participants underwent dynamic WB [18F]FDG scans using a continuous bed motion PET/CT system with simultaneous arterial blood sampling. Multiple processing pipelines that included automatic and manually generated IDIFs derived from the aorta and left ventricle, with and without motion correction were compared to the AIF. Subsequently generated quantitative images of glucose metabolism were compared to evaluate performance of the different input functions. Results: We observed moderate to high correlations between IDIFs and the AIF regarding area under the curve (r = 0.49–0.89) as well as for the cerebral metabolic rate of glucose (CMRGlu) (r = 0.68–0.95). Manual placing of IDIFs and motion correction further improved their similarity to the AIF. Discussion: In general, the automatic vendor protocol is a feasible approach for the quantification of CMRGlu for both, clinical and research settings where expertise or time is not available. However, we advise on a rigorous inspection of the placement of the volume of interest, the resulting IDIF, and the quantitative values to ensure valid interpretations. In protocols requiring longer scan times or where cohorts are prone to involuntary movement, manual IDIF definition with additional motion correction is recommended, as this has greater accuracy and reliability. [ABSTRACT FROM AUTHOR]

Objective: The pancreatic uptake of [11C]methionine ([11C]MET) is associated with beta-cell function and insulin secretion, but [11C]MET uptake and its relationship with exocrine pancreatic performance are less well studied. The postprandial release of cholecystokinin (CCK) depends on gastric emptying velocity and triggers exocrine pancreas secretion. Therefore, we assumed that high postprandial CCK concentrations stimulate the uptake of [11C]MET in the residual pancreas following pancreaticoduodenectomy. Methods: Nineteen tumor-free patients after pancreaticoduodenectomy (median age: 64; 25/75 quantile: 56–67 years); ten males, nine females and ten healthy controls (median age: 24; 25/75 quantile: 23.8–26 years) were given a mixed meal. Plasma CCK, insulin and glucose concentrations were measured before and at 10, 20, 30, 60, 90, 150 and 180 min after ingestion. Simultaneously, 800 MBq of [11C]MET were administered and the activity [maximum tissue standardized uptake values (SUVmax)] over the pancreas was measured using PET-CT at 15, 30 and 60 min after injection. Results: Integrated CCK (AUC30) correlated with SUVmax (AUC60, R2 = 0.45, p value = 0.0013). Multivariate analysis revealed postprandial insulin (AUC60) and CCK concentrations and young age as significant independent predictors of [11C] methionine uptake. Conclusion: The association between CCK concentrations and pancreatic [11C]MET uptake might indicate a causal relationship. Further research should assess whether [11C]MET uptake could serve as a less invasive tool to assess exocrine pancreas activity. [ABSTRACT FROM AUTHOR]

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Background: At the time of diagnosis, one-third of medullary thyroid carcinoma (MTC) patients show lymph node (LN) or distant metastasis. A metastasized MTC requires different surgical strategies.Objective: This study aimed to determine the value of ultrasound and [18F]fluoro-dihydroxyphenylalanine positron emission tomography with computed tomography (F-DOPA-PET-CT) in localizing MTC, as well as LN and distant metastasis.Methods: The study included 50 patients (24 males/26 females) with preoperative ultrasound, F-DOPA-PET-CT, and histologically proven MTC. Imaging results were correlated with both preoperative basal calcitonin (bCt) levels and final histology.Results: Tumors were classified as pT1a:17 (diameter, mean ± standard deviation: 5.8 ± 3.0 mm), pT1b:15 (15.0 ± 3.2 mm), pT2:9 (27.3 ± 7.0 mm), and pT3:9 (38.3 ± 24.2 mm). The median bCt level was 202 pg/mL (lower/upper quartile: 82/1074 pg/mL). Ultrasound was positive for tumor in 45/50 (92%) patients (20.0 ± 16.0 mm) and negative in 5 patients (3.2 ± 2.2 mm). Overall, 43/50 (86%) patients had positive F-DOPA local scans (20.0 ± 16.4 mm), while 7 (14%) patients were negative (7.7 ± 8.1 mm). Lastly, 21/50 (42%) patients had LN metastasis; 8/21 (38%) patients had positive LNs suspected with ultrasound, and 12/21 (57%) patients had positive LNs suspected with F-DOPA. Tumor and LN sensitivity of ultrasound was 92% and 43%, respectively, and 86% and 57% of F-DOPA-PET-CT, respectively. In 3/50 (6%) patients and 3/50 (6%) patients, mediastinal LN metastasis and distant metastasis, respectively, were diagnosed only by F-DOPA-PET-CT.Conclusion: Ultrasound and F-DOPA-PET-CT are sensitive for the localization of MTC but not for the presence and location of LN metastasis (limitations: size/number). Only F-DOPA ensures the diagnosis of distant metastasis and influences the extent of LN surgery. Surgical strategy cannot be predicted based on neither ultrasound nor F-DOPA-PET-CT. [ABSTRACT FROM AUTHOR]

Purpose: To investigate [11C]acetate PET-surrogate parameter of fatty acid synthase activity—as suitable tool for diagnosis and monitoring of liver steatosis.Methods: In this retrospective study, data were obtained from 83 prostatic carcinoma patients from 1/2008 to 1/2014. Mean HU was calculated from unenhanced CT of all patients from liver with liver HU less than 40 as threshold for liver steatosis. SUVmax of the liver and of the blood pool in thoracic aorta (as background for calculation of a liver/background ratio [SUVl/b]) was measured. t test was used with a P < 0.05 considered as statistically significant difference and ROC analysis was used for calculating specificity and sensitivity.Results: 19/83 patients (20%) had diagnosis of hepatic steatosis according to CT. Uptake of [11C]acetate was significantly higher in patients with hepatic steatosis as compared to control group (SUVmax 7.96 ± 2.0 vs. 5.48 ± 2.3 [P < 0.001]). There was also a significant correlation between both SUVmax (r = − 0.52, P < 0.001) and SUVl/b (r = − 0.59, P < 0.001) with the density (HU) of the liver. In ROC analysis for detection of liver steatosis SUVmax (threshold: 5.86) had a sensitivity of 94% and specificity of 69% with an AUC of 0.81. Increasing body mass index is correlated with the severity of steatosis.Conclusion: We showed for the first time that hepatic steatosis associates with increased [11C]acetate uptake. Also, severity of steatosis correlates with [11C]acetate uptake. [11C]acetate uptake PET seems promising for the assessment of liver steatosis. [ABSTRACT FROM AUTHOR]

Purpose: Medullary thyroid carcinoma (MTC) is characterized by a high rate of metastasis. In this study we evaluated the ability of [18F]DOPA PET/ceCT to stage MTC in patients with suspicious thyroid nodules and pathologically elevated serum calcitonin (Ctn) levels prior to total thyroidectomy and lymph node (LN) dissection.Methods: A group of 32 patients with sonographically suspicious thyroid nodules and pathologically elevated basal Ctn (bCtn) and stimulated Ctn (sCtn) levels underwent DOPA PET/ceCT prior to surgery. Postoperative histology served as the standard of reference for ultrasonography and DOPA PET/ceCT region-based LN staging. Univariate and multivariate regression analyses as well as receiver operating characteristic analysis were used to evaluate the correlations between preoperative and histological parameters and postoperative tumour persistence or relapse.Results: Primary MTC was histologically verified in all patients. Of the 32 patients, 28 showed increased DOPA decarboxylase activity in the primary tumour (sensitivity 88%, mean SUVmax 10.5). Undetected tumours were exclusively staged pT1a. The sensitivities of DOPA PET in the detection of central and lateral metastatic neck LN were 53% and 73%, in contrast to 20% and 39%, respectively, for neck ultrasonography. Preoperative bCtn and carcinoembryonic antigen levels as well as cN1b status and the number of involved neck regions on DOPA PET/ceCT were predictive of postoperative tumour persistence/relapse in the univariate regression analysis (P < 0.05). Only DOPA PET/ceCT cN1b status remained significant in the multivariate analysis (P = 0.016, relative risk 4.02).Conclusion: This study revealed that DOPA PET/ceCT has high sensitivity in the detection of primary MTC and superior sensitivity in the detection of LN metastases compared to ultrasonography. DOPA PET/ceCT identification of N1b status predicts postoperative tumour persistence. Thus, implementation of a DOPA-guided LN dissection might improve surgical success. [ABSTRACT FROM AUTHOR]