Effect of blood glucose level on standardized uptake value (SUV) in 18F- FDG PET-scan: a systematic review and meta-analysis of 20,807 individual SUV measurements

FDG imaging with long-axial field-of-view PET/CT in patients with high blood glucose-a matched pair analysis

PURPOSE

High blood glucose (hBG) in patients undergoing [18F]FDG PET/CT scans often results in rescheduling the examination, which may lead to clinical delay for the patient and decrease productivity for the department. The aim of this study was to evaluate whether long-axial field-of-view (LAFOV) PET/CT can minimize the effect of altered bio-distribution in hBG patients and is able to provide diagnostic image quality in hBG situations.

MATERIALS AND METHODS

Oncologic patients with elevated blood glucose (≥ 8.0 mmol/l) and normal blood glucose (< 8.0 mmol/l, nBG) levels were matched for tumor entity, gender, age, and BMI. hBG patients were further subdivided into two groups (BG 8-11 mmol/l and BG > 11 mmol/l). Tracer uptake in the liver, muscle, and tumor was evaluated. Furthermore, image quality was compared between long acquisitions (ultra-high sensitivity mode, 360 s) on a LAFOV PET/CT and routine acquisitions equivalent to a short-axial field-of-view scanner (simulated (sSAFOV), obtained with high sensitivity mode, 120 s). Tumor-to-background ratio (TBR) and contrast-to-noise ratio (CNR) were used as the main image quality criteria.

RESULTS

Thirty-one hBG patients met the inclusion criteria and were matched with 31 nBG patients. Overall, liver uptake was significantly higher in hBG patients (SUVmean, 3.07 ± 0.41 vs. 2.37 ± 0.33; p = 0.03), and brain uptake was significantly lower (SUVmax, 7.58 ± 0.74 vs. 13.38 ± 3.94; p < 0.001), whereas muscle (shoulder/gluteal) uptake showed no statistically significant difference. Tumor uptake was lower in hBG patients, resulting in a significantly lower TBR in the hBG cohort (3.48 ± 0.74 vs. 5.29 ± 1.48, p < 0.001). CNR was higher in nBG compared to hBG patients (12.17 ± 4.86 vs. 23.31 ± 12.22, p < 0.001). However, subgroup analysis of nBG 8-11 mmol/l on sSAFOV PET/CT compared to hBG (> 11 mmol/l) patients examined with LAFOV PET/CT showed no statistical significant difference in CNR (19.84 ± 8.40 vs. 17.79 ± 9.3, p = 0.08).

CONCLUSION

While elevated blood glucose (> 11 mmol) negatively affected TBR and CNR in our cohort, the images from a LAFOV PET-scanner had comparable CNR to PET-images acquired from nBG patients using sSAFOV PET/CT. Therefore, we argue that oncologic patients with increased blood sugar levels might be imaged safely with LAFOV PET/CT when rescheduling is not feasible.

Focal incidental colorectal fluorodeoxyglucose uptake: Should it be spotlighted?

Fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) has emerged as a cornerstone in cancer evaluation imaging, with a well-established history spanning several years. This imaging modality, encompassing the examination of the body from the base of the skull to the upper thighs, comprehensively covers the chest and abdominopelvic regions in a singular scan, allowing for a holistic assessment of nearly the entire body, including areas of marginal interest. The inherent advantage of this expansive scan range lies in its potential to unveil unexpected incidental abnormal hypermetabolic areas. The identification of incidental focal FDG uptake within colorectal regions during PET/CT scans is not an uncommon occurrence, albeit fraught with challenges associated with non-specific FDG uptake. The presence of benign colorectal lesions or physiological uptake poses a particular obstacle, as these may manifest with FDG uptake levels that mimic malignancy. Consequently, physicians are confronted with a diagnostic dilemma when encountering abnormal FDG uptake in unexpected colorectal areas. Existing studies have presented divergent results concerning these uptakes. Standardized uptake value and its derivatives have served as pivotal metrics in quantifying FDG uptake in PET images. In this article, we aim to succinctly explore the distinctive characteristics of FDG, delve into imaging findings, and elucidate the clinical significance of incidental focal colorectal uptake. This discussion aims to contribute valuable insights into the nuanced interpretation of such findings, fostering a comprehensive understanding.

A Review of Machine Learning Algorithms for Biomedical Applications

As the amount and complexity of biomedical data continue to increase, machine learning methods are becoming a popular tool in creating prediction models for the underlying biomedical processes. Although all machine learning methods aim to fit models to data, the methodologies used can vary greatly and may seem daunting at first. A comprehensive review of various machine learning algorithms per biomedical applications is presented. The key concepts of machine learning are supervised and unsupervised learning, feature selection, and evaluation metrics. Technical insights on the major machine learning methods such as decision trees, random forests, support vector machines, and k-nearest neighbors are analyzed. Next, the dimensionality reduction methods like principal component analysis and t-distributed stochastic neighbor embedding methods, and their applications in biomedical data analysis were reviewed. Moreover, in biomedical applications predominantly feedforward neural networks, convolutional neural networks, and recurrent neural networks are utilized. In addition, the identification of emerging directions in machine learning methodology will serve as a useful reference for individuals involved in biomedical research, clinical practice, and related professions who are interested in understanding and applying machine learning algorithms in their research or practice.

Unexpected focal fluorodeoxyglucose uptake in main organs; pass through or pass by?

Since the inception of fluorine-18 fluorodeoxyglucose (F-18 FDG), positron emission tomography/computed tomography (PET/CT) utilizing F-18 FDG has become widely accepted as a valuable imaging modality in the field of oncology, with global prevalence in clinical practice. Given that a single Torso PET/CT scan encompasses the anatomical region from the skull base to the upper thigh, the detection of incidental abnormal focal hypermetabolism in areas of limited clinical interest is both feasible and not uncommon. Numerous investigations have been undertaken to delineate the distinctive features of these findings, yet the outcomes have proven inconclusive. The incongruent results of these studies present a challenge for physicians, leaving them uncertain about the appropriate course of action. This article provides a succinct overview of the characteristics of fluorodeoxyglucose, followed by a comprehensive discussion of the imaging findings and clinical significance associated with incidental focal abnormal F-18 FDG activity in several representative organs. In conclusion, while the prevalence of unrecognized malignancy varies across organs, malignancies account for a substantial proportion, ranging from approximately one-third to over half, of incidental focal uptake. In light of these rates, physicians are urged to exercise vigilance in not disregarding unexpected uptake, facilitating more assured clinical decisions, and advocating for further active evaluation.

Impact of patient characteristic factors on the dynamics of liver glucose metabolism: Evaluation of multiparametric imaging with dynamic whole-body 18 F-fluorodeoxyglucose-positron emission tomography

AIMS

To assess the impact of various patient characteristics on the dynamics of liver glucose metabolism using automated multiparametric imaging with whole-body dynamic 18 F-fluorodeoxyglucose (FDG)-positron emission tomography (PET).

MATERIALS AND METHODS

We retrospectively enrolled 540 patients who underwent whole-body dynamic FDG-PET. Three quantitative indices representing hepatic glucose metabolism [mean standardized uptake value normalized by lean body mass (SULmean), metabolic glucose rate (kinetic index) and distribution volume (DV)] were measured from multiparametric PET images produced automatically based on the Patlak plot model. Patient characteristics including age, sex, body mass index, fasting time, blood glucose level, and the presence of diabetes mellitus (DM) or hepatic steatosis (HS) were collected. We examined the correlations between the characteristic factors and three quantitative indices using multiple regression analysis.

RESULTS

The success rate of kinetic analysis using multiparametric PET imaging was 93.3% (504/540). Hepatic SULmean was significantly correlated with age (p < .001), sex (p < .001) and blood glucose level (p = .002). DV was significantly correlated with age (p = .033), sex (p < .001), body mass index (p = .002), fasting time (p = .043) and the presence of HS (p = .002). The kinetic index was significantly correlated with age (p < .001) and sex (p = .004). In the comparison of the healthy, DM and HS groups, patients with DM had a significantly increased SULmean, whereas patients with HS had a significantly decreased DV.

CONCLUSIONS

Our results showed that liver glucose metabolism was influenced by various patient characteristic factors. Multiparametric FDG-PET imaging can be used to analyse the kinetics of liver glucose metabolism in routine clinical practice.

68Ga-Labeled Fibroblast Activation Protein Inhibitor PET/CT for the Early and Late Prediction of Pathologic Response to Neoadjuvant Chemotherapy in Breast Cancer Patients: A Prospective Study

68Ga-labeled fibroblast activation protein inhibitor (68Ga-FAPI) PET/CT has demonstrated promising clinical results, with a higher SUVmax and tumor-to-background ratio (TBR) in breast cancer (BC) patients than 18F-FDG PET/CT. Here, we aimed to evaluate the suitability of 68Ga-FAPI PET/CT for the early and late prediction of the pathologic response to neoadjuvant chemotherapy (NAC) in BC. Methods: Twenty-two consecutive patients with newly diagnosed BC and an indication for NAC were prospectively included. All patients underwent standard chemotherapy and 68Ga-FAPI PET/CT at baseline, after 2 cycles of NAC (PET2), and 1 wk before surgery (PET3). SUVmax was measured in the primary tumor region and positive regional lymph nodes. The expression of fibroblast activation protein in the primary lesion was analyzed by immunohistochemistry. Results: Seven patients (31.8%) achieved a pathologic complete response (pCR), and 15 (68.2%) had residual tumors. Thirteen patients (59.1%) showed concentric withdrawal of the primary tumor, and 9 (40.9%) showed diffuse withdrawal. Between PET2 and PET3, the ΔSUVmax of the primary tumor (R 2 = 0.822; P = 0.001) and metastatic lymph nodes (R 2 = 0.645; P = 0.002) were significantly correlated. The absolute values of SUVmax and TBR at PET2 and PET3 were lower in patients with pCR than in those without pCR (P < 0.05). Moreover, a larger ΔSUVmax at any time point was strongly associated with pCR (P < 0.05). Similar downward trends in SUVmax, TBR, and ΔSUVmax were observed in the pattern of primary tumor reduction. For predicting pCR, the optimal cutoff values for ΔSUVmax after 2 chemotherapy cycles, ΔSUVmax before surgery, TBR after 2 chemotherapy cycles, and TBR before surgery of the primary tumor were 3.4 (area under the curve [AUC], 0.890), 1.1 (AUC, 0.978), -63.8% (AUC, 0.879), -90.8% (AUC, 0.978), 7.6 (AUC, 0.848), and 1.4 (AUC, 0.971), respectively. Immunohistochemistry showed that the SUVmax and TBR of 68Ga-FAPI PET/CT were positively correlated with fibroblast activation protein expression (P < 0.001 for both). Conclusion: Assessment of early changes in 68Ga-FAPI uptake during NAC by 68Ga-FAPI PET/CT can predict pCR and primary tumor concentric withdrawal in BC patients. 68Ga-FAPI PET/CT has great potential for the early and late prediction of the pathologic response to NAC in BC.

27-Hydroxycholesterol impairs learning and memory ability via decreasing brain glucose uptake mediated by the gut microbiota

Brain glucose hypometabolism is a significant manifestation of Alzheimer's disease (AD). 27-hydroxycholesterol (27-OHC) and the gut microbiota have been recognized as factors possibly influencing the pathogenesis of AD. This study aimed to investigate the link between 27-OHC, the gut microbiota, and brain glucose uptake in AD. Here, 6-month-old male C57BL/6 J mice were treated with sterile water or antibiotic cocktails, with or without 27-OHC and/or 27-OHC synthetic enzyme CYP27A1 inhibitor anastrozole (ANS). The gut microbiota, brain glucose uptake levels, and memory ability were measured. We observed that 27-OHC altered microbiota composition, damaged brain tissue structures, decreased the 2-deoxy-2-[18 F] fluorodeoxyglucose (18F-FDG) uptake value, downregulated the gene expression of glucose transporter type 4 (GLUT4), reduced the colocalization of GLUT1/glial fibrillary acidic protein (GFAP) in the hippocampus, and impaired spatial memory. ANS reversed the effects of 27-OHC. The antibiotic-treated mice did not exhibit similar results after 27-OHC treatment. This study reveals a potential molecular mechanism wherein 27-OHC-induced memory impairment might be linked to reduced brain glucose uptake, mediated by the gut microbiota.

Comparison between an SGLT2 inhibitor and insulin in tumor-to-tissue contrasts in 18F-FDG PET imaging of diabetic mice

18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) has been widely utilized for tumor diagnosis. Hyperglycemia affects the 18F-FDG uptake and reduces tumor-to-tissue contrasts, however, ideal hypoglycemic drugs are lacking. This study compared the role of insulin with the novel widely used hypoglycemic drug, sodium-glucose cotransporter 2 (SGLT2) inhibitor, on 18F-FDG PET imaging in diabetic conditions. The streptozotocin (STZ)-induced diabetic C57BL/6N mice were inoculated with B16 (mouse melanoma) cells to establish the xenograft tumor model. After the mice had been administrated with dapagliflozin (30 mg/kg, IG) or insulin (0.75 U/kg, IP) for one hour, 9.25 MBq/10 g 18F-FDG was injected. Biodistributions were detected by gamma counting and microPET imaging. The results showed dapagliflozin did not significantly affect the 18F-FDG uptake in tumors but reduced uptake in reference tissues, resulting in a significant increase in the tumor-to-skeletal muscle ratio. Conversely, insulin increased 18F-FDG uptake in tumors without significant reduction in uptake in reference tissues; Although there was an observable improvement in tumor imaging, it did not reach significantly statistical differences. This study suggests that insulin and SGLT2 inhibitor yield comparable effects on the quality of 18F-FDG PET imaging in diabetic patients. Nevertheless, SGLT2 inhibitors would be more suitable when skeletal muscle is used as reference tissue.

Use of Oral Empagliflozin to Obtain Optimal Blood Sugar Levels for Conducting 18 F-FDG PET-CT in Patients with Hyperglycemia-A Pilot Study

Background  Flourine-18 fluorodeoxyglucose positron emission tomography-computed tomography ( 18 F-FDG PET-CT) is a well-established imaging modality for the evaluation of patients with oncological and nononcological conditions. The underlying principle of imaging is the preferentially increased glucose consumption by cancer cells, due to overexpression of glucose type 1 receptors that are insulin independent. Thus, one of the factors that leads to decreased sensitivity of an 18 F-FDG PET-CT is elevated blood sugar levels, leading to decreased glucose uptake by cancer cells due to competitive inhibition. A significant percentage of patients scheduled for PET-CT scan has diabetes mellitus type II as a comorbid condition and often has elevated random blood sugar (RBS) precluding an upfront PET-CT evaluation. Such cases must be rescheduled. This causes delay in the evaluation and management of such patients. Empagliflozin is a novel sodium glucose type 2 inhibitor that prevents tubular reabsorption of glucose and increases renal glycosuria resulting in decreased blood sugar. This drug does not cause significant hypoglycemia or increase endogenous insulin secretion. This study was undertaken to evaluate a potential role for empagliflozin in facilitating optimal blood sugar control in patients with hyperglycemia on the day of the scheduled PET scan. Methods  This is an interventional prospective study and patients detected to have RBS more than 200 mg/dL on the day of the scheduled scan were included in the study. The patients were administered two tablets of 10 mg empagliflozin and kept under observation. Samples for RBS were taken at approximately 2nd and 4th hour post administration by bedside method. These patients underwent scan on the same day after adequate sugar control and when an RBS of less than 200 mg/dL was achieved. The primary outcome studied was change in RBS values in the patient cohort and evaluation of PET SUV (standardized uptake value) compared with the rest of the patients scheduled on the same day. Secondary outcome was assessment of any side effects in the patients. Results  Total of 10 patients were found to have elevated blood sugar (RBS > 200 mg/dL; irrespective of being on medication) and did not meet the evaluation criteria for a PET-CT scan on the scheduled day. Following administration of the drug, all 10 patients were able to attain blood sugar levels and fulfill the criteria for undergoing a PET-CT scan. No obvious side effect was noted in any of the patient. The SUV values of the patient cohort were comparable with the rest of the patient scanned on the day. Conclusion  In this pilot study, 20 mg of empagliflozin (2 tablets of 10 mg) appears to be a safe and effective method for achieving optimal decrease in the RBS without causing hypoglycemia or hyperinsulinemia. It can be safely employed in the subset of population with RBS between 201 and 300 mg/dL to adequately bring the sugar levels at acceptable levels RBS less than 200 mg/dl and fulfill the FDG PET-CT criteria as per European Association of Nuclear Medicine (EANM) norms.

Predictors of infectious foci on FDG PET/CT in Staphylococcus aureus bacteremia

We looked for predicting factors for the detection of infectious foci on 18F-fluorodeoxyglucose-positron emission tomography in combination with computed tomography (FDG PET/CT) among patients with Staphylococcus aureus bacteremia (SAB) who participated in an interventional study that was conducted at Rambam Health Care Campus, between July 1, 2015 and February 1, 2019. The primary outcome was an infectious focus detected by FDG PET/CT. Independent predictors for detection of focal infection were identified using univariate followed by a logistic regression multivariate analysis. We included 149 patients with 151 separate episodes of SAB who underwent FDG-PET/CT. Focal infections were detected in 107 patients (70.8%). Independent predictors for focal infection detection were community acquisition of bacteremia with odds ratio (OR) 3.03 [95% confidence interval (CI) 1.04-8.77], p-0.042 and C reactive protein (CRP) with OR 1.09 [95% CI 1.04-1.14], p < 0.001. Primary bacteremia was inversely associated with focal infection detection with OR 0.27 [0.10-0.69], p = 0.007, as were the pre-scan blood glucose levels OR 0.9 [0.98-0.99], p-0.004. The latter stayed significant in the subgroup of patients with diabetes mellitus. To conclude, patients with community-acquired bacteremia or high CRP levels should be carefully investigated for focal infection. Patients who present with primary bacteremia seem to be at low risk for focal infection.

Utility of 18F-FDG uptake in predicting major pathological response to neoadjuvant immunotherapy in patients with resectable non‑small cell lung cancer

PURPOSE

The aim of present study was to investigate the efficiency of ¹⁸F-FDG uptake in predicting major pathological response (MPR) in resectable non-small cell lung cancer (NSCLC) patients with neoadjuvant immunotherapy.

METHODS

A total of 104 patients with stage I-IIIB NSCLC were retrospectively derived from National Cancer Center of China, of which 36 cases received immune checkpoint inhibitors (ICIs) monotherapy (I-M) and 68 cases with ICI combination therapy (I-C). ¹⁸F-FDG PET-CT scans were performed at baseline and after neoadjuvant therapy (NAT). Receiver-operating characteristic (ROC) curve analyses were conducted and area under ROC curve (AUC) was calculated for biomarkers including maximum standardized uptake value (SUVmax), inflammatory biomarkers, tumor mutation burden (TMB), PD-L1 tumor proportion score (TPS) and iRECIST.

RESULTS

Fifty-four resected NSCLC tumors achieved MPR (51.9%, 54/104). In both neoadjuvant I-M and I-C cohorts, post-NAT SUVmax and the percentage changes of SUVmax (ΔSUVmax%) were significantly lower in the patients with MPR versus non-MPR (p < 0.01), and were also negatively correlated with the degree of pathological regression (p < 0.01). The AUC of ΔSUVmax% for predicting MPR was respectively 1.00 (95% CI: 1.00-1.00) in neoadjuvant I-M cohort and 0.94 (95% CI: 0.86-1.00) in I-C cohort. Baseline SUVmax had a statistical prediction value for MPR only in I-M cohort, with an AUC up to 0.76 at the threshold of 17.0. ΔSUVmax% showed an obvious advantage in MPR prediction over inflammatory biomarkers, TMB, PD-L1 TPS and iRECIST.

CONCLUSION

¹⁸F-FDG uptake can predict MPR in NSCLC patients with neoadjuvant immunotherapy.

Importance of Blood Glucose Management Before 18F-FDG PET/CT in 322 Patients with Bacteremia of Unknown Origin

We investigated the effects of blood glucose levels on the performance of ¹⁸F-FDG PET/CT for detecting an infection focus in patients with bacteremia. Methods: A total of 322 consecutive patients with bacteremia who underwent ¹⁸F-FDG PET/CT between 2010 and 2021 were included. Logistic regression analysis was performed to evaluate the association between finding a true-positive infection focus on ¹⁸F-FDG PET/CT and blood glucose level, type of diabetes, and use of hypoglycemic medication. C-reactive protein, leukocyte count, duration of antibiotic treatment, and type of isolated bacteria were considered as well. Results: Blood glucose level (odds ratio, 0.76 per unit increase; P = <0.001) was significantly and independently associated with ¹⁸F-FDG PET/CT outcome. In patients with a blood glucose level between 3.0 and 7.9 mmol/L (54-142 mg/dL), the true-positive detection rate of ¹⁸F-FDG PET/CT varied between 61% and 65%, whereas in patients with a blood glucose level between 8.0 and 10.9 mmol/L (144-196 mg/dL), the true-positive detection rate decreased to 30%-38%. In patients with a blood glucose level greater than 11.0 mmol/L (200 mg/dL), the true-positive detection rate was 17%. In addition to C-reactive protein (odds ratio, 1.004 per point increase; P = 0.009), no other variables were independently associated with ¹⁸F-FDG PET/CT outcome. Conclusion: In patients with moderate to severe hyperglycemia, ¹⁸F-FDG PET/CT was much less likely to identify the focus of infection than in normoglycemic patients. Although current guidelines recommend postponing ¹⁸F-FDG PET/CT only in cases of severe hyperglycemia with glucose levels greater than 11 mmol/L (200 mg/dL), a lower blood glucose threshold seems to be more appropriate in patients with bacteremia of unknown origin and other infectious diseases.

Brain FDG PET for visualizing the relation between impaired lung function and cognitive decline in lung cancer: a preliminary study

OBJECTIVE

Impaired lung function is associated with an increased risk for cognitive decline. F-18 fluorodeoxyglucose (FDG) PET is a well-known neurodegenerative biomarker for dementia. We investigated the association between lung and brain function using FDG PET in patients with lung cancer.

METHODS

A random sub-sample of 102 patients with lung cancer and without a self-reported history of neuropsychiatric disorders were recruited and underwent both lung function tests and FDG PET scans before treatment. Lung function was analyzed as the percentage predicted value (% pred) of forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1). FDG uptake was measured as standardized uptake values (SUVs) in the frontal, parietal, temporal, and occipital cortices and cognition-related regions. Regional SUV ratios (SUVRs) were calculated by dividing the SUV in each region by the whole-brain SUV and were then evaluated against lung function indices and clinical variables.

RESULTS

After excluding five patients with brain metastases, 97 patients were included in the final analysis (mean age, 67.7 ± 10.3 years). Mean FVC and mean FEV1 were 80.0% ± 15.4% and 77.6% ± 17.8%, respectively. Both FVC and FEV1 were positively correlated with SUVRs in all brain regions after adjusting the data for clinical variables. The degree of decrease in SUVRs related to lung function was not significantly different between cognition-related regions and other regions.

CONCLUSION

Impaired lung function was associated with decreased glucose metabolism in all regions of the brain, indicating that cognitive decline related to decreased glucose metabolism may be due to reduced perfusion.

Brain positron emission tomography (PET) and cognitive abnormalities one year after COVID-19

Emerging evidence indicates that the etiologic agent responsible for coronavirus disease 2019 (COVID-19), can cause neurological complications. COVID-19 may induce cognitive impairment through multiple mechanisms. The aim of the present study was to describe the possible neuropsychological and metabolic neuroimaging consequences of COVID-19 12 months after patients' hospital discharge. We retrospectively recruited 7 patients (age [mean ± SD] = 56 years ± 12.39, 4 men) who had been hospitalized for COVID-19 with persistent neuropsychological deficits 12 months after hospital discharge. All patients underwent cognitive assessment and brain (¹⁸F-FDG) PET/CT, and one also underwent ¹⁸F-amyloid PET/CT. Of the seven patients studied, four had normal glucose metabolism in the brain. Three patients showed various brain hypometabolism patterns: (1) unilateral left temporal mesial area hypometabolism; (2) pontine involvement; and (3) bilateral prefrontal area abnormalities with asymmetric parietal impairment. The patient who showed the most widespread glucose hypometabolism in the brain underwent an ¹⁸F-amyloid PET/CT to assess the presence of Aβ plaques. This examination showed significant Aβ deposition in the superior and middle frontal cortex, and in the posterior cingulate cortex extending mildly in the rostral and caudal anterior cingulate areas. Although some other reports have already suggested that brain hypometabolism may be associated with cognitive impairment at shorter intervals from SarsCov-2 infection, our study is the first to assess cognitive functions, brain metabolic activity and in a patient also amyloid PET one year after COVID-19, demonstrating that cerebral effects of COVID-19 can largely outlast the acute phase of the disease and even be followed by amyloid deposition.

Prospective Evaluation of Quantitative F-18-FDG-PET/CT for Pre-Operative Thoracic Lymph Node Staging in Patients with Lung Cancer as a Target for Computer-Aided Diagnosis

Purpose: Pre-operative assessment of thoracic lymphonodal (LN) involvement in patients with lung cancer (LC) is crucial when choosing the treatment modality. Visual assessment of F-18-FDG-PET/CT (PET/CT) is well established, however, there is still a need for prospective quantitative data to differentiate benign from malignant lesions which would simplify staging and guide the further implementation of computer-aided diagnosis (CAD). Methods: In this prospective study, 37 patients with confirmed lung cancer (m/f = 24/13; age: 70 [52–83] years) were analyzed. All patients underwent PET/CT and quantitative data (standardized uptake values) were obtained. Histological results were available for 101 thoracic lymph nodes. Quantitative data were matched to determine cut-off values for delineation between benign vs. malignant lymph nodes. Furthermore, a scoring system derived from these cut-off values was established. Statistical analyses were performed through ROC analysis. Results: Quantitative analysis revealed the optimal cut-off values (p < 0.01) for the differentiation between benign and malignant thoracic lymph nodes in patients suffering from lung cancer. The respective areas under the curve (AUC) ranged from 0.86 to 0.94. The highest AUC for a ratio of lymph node to healthy lung tissue was 0.94. The resulting accuracy ranged from 78.2% to 89.1%. A dedicated scoring system led to an AUC of 0.93 with a negative predictive value of 95.4%. Conclusion: Quantitative analysis of F-18-FDG-PET/CT data provides reliable results for delineation between benign and malignant thoracic lymph nodes. Thus, quantitative parameters can improve diagnostic accuracy and reliability and can also facilitate the handling of the steadily increasing number of clinical examinations.

Prognostic analysis of curatively resected pancreatic cancer using harmonized positron emission tomography radiomic features

BACKGROUND

Texture features reflecting tumour heterogeneity enable us to investigate prognostic factors. The R package ComBat can harmonize the quantitative texture features among several positron emission tomography (PET) scanners. We aimed to identify prognostic factors among harmonized PET radiomic features and clinical information from pancreatic cancer patients who underwent curative surgery.

METHODS

Fifty-eight patients underwent preoperative enhanced dynamic computed tomography (CT) scanning and fluorodeoxyglucose PET/CT using four PET scanners. Using LIFEx software, we measured PET radiomic parameters including texture features with higher order and harmonized these PET parameters. For progression-free survival (PFS) and overall survival (OS), we evaluated clinical information, including age, TNM stage, and neural invasion, and the harmonized PET radiomic features based on univariate Cox proportional hazard regression. Next, we analysed the prognostic indices by multivariate Cox proportional hazard regression (1) by using either significant (p < 0.05) or borderline significant (p = 0.05-0.10) indices in the univariate analysis (first multivariate analysis) or (2) by using the selected features with random forest algorithms (second multivariate analysis). Finally, we checked these multivariate results by log-rank test.

RESULTS

Regarding the first multivariate analysis for PFS after univariate analysis, age was the significant prognostic factor (p = 0.020), and MTV and GLCM contrast were borderline significant (p = 0.051 and 0.075, respectively). Regarding the first multivariate analysis of OS, neural invasion, Shape sphericity and GLZLM LZLGE were significant (p = 0.019, 0.042 and 0.0076). In the second multivariate analysis, only MTV was significant (p = 0.046) for PFS, whereas GLZLM LZLGE was significant (p = 0.047), and Shape sphericity was borderline significant (p = 0.088) for OS. In the log-rank test, age, MTV and GLCM contrast were borderline significant for PFS (p = 0.08, 0.06 and 0.07, respectively), whereas neural invasion and Shape sphericity were significant (p = 0.03 and 0.04, respectively), and GLZLM LZLGE was borderline significant for OS (p = 0.08).

CONCLUSIONS

Other than the clinical factors, MTV and GLCM contrast for PFS and Shape sphericity and GLZLM LZLGE for OS may be prognostic PET parameters. A prospective multicentre study with a larger sample size may be warranted.

Impact of Reduced Image Noise on Deauville Scores in Patients with Lymphoma Scanned on a Long-Axial Field-of-View PET/CT-Scanner

BACKGROUND

Total body and long-axial field-of-view (LAFOV) PET/CT represent visionary innovations in imaging enabling either improved image quality, reduction in injected activity-dose or decreased acquisition time. An improved image quality may affect visual scoring systems, including the Deauville score (DS), which is used for clinical assessment of patients with lymphoma. The DS compares SUVmax in residual lymphomas with liver parenchyma, and here we investigate the impact of reduced image noise on the DS in patients with lymphomas scanned on a LAFOV PET/CT.

METHODS

Sixty-eight patients with lymphoma underwent a whole-body scan on a Biograph Vision Quadra PET/CT-scanner, and images were evaluated visually with regard to DS for three different timeframes of 90, 300, and 600 s. SUVmax and SUVmean were calculated from liver and mediastinal blood pool, in addition to SUVmax from residual lymphomas and measures of noise.

RESULTS

SUVmax in liver and in mediastinal blood pool decreased significantly with increasing acquisition time, whereas SUVmean remained stable. In residual tumor, SUVmax was stable during different acquisition times. As a result, the DS was subject to change in three patients.

CONCLUSIONS

Attention should be drawn towards the eventual impact of improvements in image quality on visual scoring systems such as the DS.

Prognostic value of fibroblast activation protein expressing tumor volume calculated from [68 Ga]Ga-FAPI PET/CT in patients with esophageal squamous cell carcinoma

BACKGROUND

This study aimed to investigate the prognostic value of semiquantitative parameters derived from [68 Ga]Ga-fibroblast activation protein inhibitor (FAPI) PET/CT for patients with esophageal squamous cell carcinoma (ESCC) treated with definitive chemoradiotherapy.

METHODS

We conducted a retrospective analysis on patients from a prospective parent study (NCT04416165). A total of 45 patients with locally advanced ESCC who underwent [68 Ga]Ga-FAPI from December 2019 to March 2021 were included. The maximum standard uptake value (SUVmax), gross tumor volume (GTV), and total lesion-FAPI (TL-FAPI) of the primary tumor were calculated from the corresponding PET/CT image. Unpaired parameters were compared using Student's t test or the Mann-Whitney U test. Paired parameters were compared using the paired t test or the Wilcoxon matched-pairs signed-rank test. Kaplan-Meier curves were generated to calculate progression-free survival (PFS) and overall survival (OS) rates, and Cox regression analysis was performed to determine which PET/CT parameters were prognostic factors for PFS and/or OS.

RESULTS

Thirty-four of the 45 patients met the criteria, and the median follow-up time was 24 months (16-29 months). SUVmax-FAPI, GTVFAPI, and TL-FAPI in patients with stage T4 tumors were significantly higher than those in patients with stage T2/T3 tumors (all P < 0.01). In the univariate Cox regression analysis, T stage, N stage, GTVFAPI, and TL-FAPI were associated with PFS, and T stage, GTVFAPI, and TL-FAPI were associated with OS. Upon multivariable analysis, GTVFAPI was an independent prognostic factor for both PFS (hazard ratio (HR), 5.76; 95% confidence interval (CI), 2.13-15.57, P = 0.001) and OS (HR, 4.96; 95% CI, 2.55-18.79, P = 0.001).

CONCLUSION

This pilot study revealed that [68 Ga]Ga-FAPI PET/CT may have prognostic value for patients with ESCC treated with definitive chemoradiotherapy. It may aid in personalized patient management by steering treatment modifications before therapy. Prospective studies with larger samples and longer observation periods are needed.

The usefulness of the total metabolic tumor volume for predicting the postoperative recurrence of thoracic esophageal squamous cell carcinoma

Background

Induction or adjuvant therapies are not always beneficial for thoracic esophageal squamous cell carcinoma (ESCC) patients, and it is thus important to identify patients at high risk for postoperative ESCC recurrence. We investigated the usefulness of the total metabolic tumor volume (TMTV) for predicting the postoperative recurrence of thoracic ESCC.

Methods

We retrospectively analyzed the cases of 163 thoracic ESCC patients (135 men, 28 women; median age of 66 [range 34–82] years) treated at our hospital in 2007–2012. The TMTV was calculated from the fluorine-18 fluorodeoxyglucose (18F-FDG) uptake in the primary lesion and lymph node metastases. The optimal cut-off values for relapse and non-relapse were obtained by the time-dependent receiver operating curve analyses. Relapse-free survival (RFS) was evaluated by the Kaplan-Meier method, and between-subgroup differences in survival were analyzed by log-rank test. The prognostic significance of metabolic parameters and clinicopathological variables was assessed by a Cox proportional hazard regression analysis. The difference in the failure patterns after surgical resection was evaluated using the χ2-test.

Results

The optimal cut-off value of TMTV for discriminating relapse from non-relapse was 3.82. The patients with a TMTV ≥3.82 showed significantly worse prognoses than those with low values (p < 0.001). The TMTV was significantly related to RFS (model 1 for preoperative risk factors: TMTV: hazard ratio [HR] =2.574, p = 0.004; model 2 for preoperative and postoperative risk factors: HR = 1.989, p = 0.044). The combination of the TMTV and cN0–1 or pN0–1 stage significantly stratified the patients into low-and high-risk recurrence groups (TMTV cN0–1, p < 0.001; TMTV pN0–1, p = 0.004). The rates of hematogenous and regional lymph node metastasis were significantly higher in the patients with TMTV ≥3.82 than those with low values (hematogenous metastasis, p < 0.001, regional lymph node metastasis, p = 0.011).

Conclusions

The TMTV was a more significantly independent prognostic factor for RFS than any other PET parameter in patients with resectable thoracic ESCC. The TMTV may be useful for the identifying thoracic ESCC patients at high risk for postoperative recurrence and for deciding the patient management.

Lesion-to-Liver SUVmax Ratio to Improve the Prognostic Value of the End of Treatment PET/CT in Diffuse Large B-Cell Lymphoma

Background: Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma worldwide. After first-line therapy, 30–40% of patients relapse or experiment with refractory disease. 18F-FDG PET/CT represents a validated diagnostic tool in post-treatment evaluation of FDG-avid lymphoma, and the Deauville Score (DS), a five-point visual scale, is usually used to assess response. However, the increased number of false positive findings suggested the need to search for new parameters. The aim of this study is to evaluate the prognostic value of End-of-Treatment-PET, comparing DS to the semi-quantitative Lesion-to-Liver ratio (LLR). Methods: newly diagnosed DLBCL patients who underwent 18F-FDG PET/CT were retrospectively analyzed. End-of-Treatment PET findings were assessed first using DS; secondly, assigned the LLR. Results: a total of 105 patients were finally enrolled. ROC analysis showed an LLR of 1.80 as the optimal cutoff value for predicting a disease progression (sensitivity 58%, specificity 95%). Both DS and LLR showed a statistically significant correlation with PFS and OS. LLR resulted in a better diagnostic performance than DS. Conclusions: LLR showed to be a reliable diagnostic method to assess treatment response in DLBCL. The integration of visual and semi-quantitative criteria could help in decision making, improving specificity and PPV.

Effect of steroid treatment on the diagnostic yield of baseline 18f-fluorodeoxyglucose positron emission tomography in aggressive B cell lymphoma

Aggressive B cell lymphoma often requires prompt steroid treatment, even before baseline ¹⁸f-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and definitive treatment, to alleviate symptoms or prevent organ damage. Since lymphoma is a steroid-sensitive malignancy, there are concerns that steroids might affect the results of FDG PET/CT and decrease its diagnostic yield. The aim of the current study was to evaluate the effect of steroids administered before baseline PET/CT on the maximum standardized uptake value (SUVmax) and additional PET/CT parameters. Retrospective review of the database in a tertiary medical center yielded 178 patients newly diagnosed with aggressive B cell lymphoma between January 2017 and May 2020 who had an available baseline FDG PET/CT scan. The cohort was divided into patients who received steroids before PET/CT (n = 47) and those who did not (n = 131), and the groups were compared for SUVmax and additional PET/CT parameters. The steroid-treated group had a higher disease stage and lactate dehydrogenase level compared to the steroid-naïve group, with a trend toward a higher international prognostic index. There was no significant between-group difference in SUVmax (P = 0.61). This finding remained consistent across steroid treatment durations and dosage regimens. Further evaluation revealed a significantly larger mean tumor volume and a trend toward a higher tumor metabolic burden in the steroid-treated group, yet no between-group difference in SUV mean or other PET/CT parameters. In this retrospective analysis of patients with aggressive B cell lymphoma, steroid prophase prior to baseline PET/CT did not decrease the diagnostic yield of the scan. However, further studies are required to fully appreciate the impact of steroids on PET CT parameters.

Clinical Impact of Dual Time Point 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Fusion Imaging in Pancreatic Cancer

We examined the value of preoperative dual time point (DTP) 18F-fluorodeoxyglucose positron emission tomography/computed tomography fusion imaging (FDG PET/CT) as a predictor of early recurrence or the outcomes in patients with pancreatic cancer. Standardized uptake values (SUVs) in DTP FDG PET/CT were performed as preoperative staging. SUVmax1 and SUVmax2 were obtained in 60 min and 120 min, respectively. ΔSUVmax% was defined as (SUVmax2 − SUVmax1)/SUVmax1 × 100. The optimal cut-off values for SUVmax parameters were selected based on tumor relapse within 1 year of surgery. Optimal cut-off values for SUVmax1 and ΔSUVmax% were 7.18 and 24.25, respectively. The combination of SUVmax1 and ΔSUVmax% showed higher specificity and sensitivity, and higher positive and negative predictive values for tumor relapse within 1 year than SUVmax1 alone. Relapse-free survival (RFS) was significantly worse in the subgroups of high SUVmax1 and high ΔSUVmax% (median 7.0 months) than in the other subgroups (p < 0.0001). The multivariate Cox analysis of RFS identified high SUVmax1 and high ΔSUVmax% as independent prognostic factors (p = 0.0060). DTP FDG PET/CT may effectively predict relapse in patients with pancreatic cancer. The combination of SUVmax1 and ΔSUVmax% identified early recurrent patient groups more precisely than SUVmax1 alone.

Intrapatient variability of 18F-FDG uptake in normal tissues

Objectives

To investigate the effect of serum glucose level and other confounding factors on the variability of maximum standardized uptake value (SUVmax) in normal tissues within the same patient on two separate occasions and to suggest an ideal reference tissue.

Materials and Methods

We retrospectively reviewed 334 18F-FDG PET/CT scans of 167 cancer patients including 38 diabetics. All patients had two studies, on average 152 ± 68 days apart. Ten matched volumes of interest were drawn on the brain, right tonsil, blood pool, heart, lung, liver, spleen, bone marrow, fat, and iliopsoas muscle opposite third lumber vertebra away from any pathological 18F-FDG uptake to calculate SUVmax.

Results

SUVmax of the lungs and heart were significantly different in the two studies (P = 0.003 and P = 0.024 respectively). Only the brain uptake showed a significant moderate negative correlation with the level of blood glucose in diabetic patients (r = −0.537, P = 0.001) in the first study, while the SUVmax of other tissues showed negligible or weak correlation with the level of blood glucose in both studies.

The liver showed significant moderate positive correlation with body mass index (BMI) in both studies (r = .416, P = <0.001 versus r = 0.453, P = <0.001, respectively), and blood pool activity showed significant moderate positive correlation with BMI in the first study only (r = 0.414, P = <0.001). The liver and blood pool activities showed significant moderate negative correlation with 18F-FDG uptake time in first study only (r = −0.405, P-value = <0.001; and r = −0.409, P-value = <0.001, respectively).

In the multivariate analysis, the liver showed a consistent effect of the injected 18F-FDG dose and uptake duration on its SUVmax on the two occasions. In comparison, spleen and muscle showed consistent effect only of the injected dose on the two occasions.

Conclusion

The liver, muscle, and splenic activities showed satisfactory test/retest stability and can be used as reference activities. The spleen and muscle appear to be more optimal reference than the liver, as it is only associated with the injected dose of 18F-FDG.

Prediction of benzimidazole therapy duration with PET/CT in inoperable patients with alveolar echinococcosis

Alveolar echinococcosis is a rare parasitic disease, most frequently affecting the liver, as a slow-growing tumor-like lesion. If inoperable, long-term benzimidazole therapy is required, which is associated with high healthcare costs and occasionally with increased morbidity. The aim of our study was to determine the role ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in staging of patients with alveolar echinococcosis and to identify quantitative imaging parameters related to patient outcome and/or duration of benzimidazole therapy. In this single-center retrospective cohort study, 47 PET/CT performed for staging in patients with confirmed alveolar echinococcosis were analysed. In 43 patients (91%) benzimidazole therapy was initiated and was successfully stopped after a median of 870 days (766–2517) in 14/43 patients (33%). In inoperable patients, tests for trend of survivor functions displayed clear trends for longer benzimidazole therapy duration (p = 0.05; n = 25), and for longer time intervals to reach non-detectable serum concentration of Em-18 antibodies (p = 0.01, n = 15) across tertiles of SUVratio (maximum standardized uptake value in the echinococcus manifestation compared to normal liver tissue). Hence, in inoperable patients with alveolar echinococcosis, PET/CT performed for staging may predict the duration of benzimidazole therapy.

Evaluation of physiological Waldeyer's ring, mediastinal blood pool, thymic, bone marrow, splenic and hepatic activity with 18F-FDG PET/CT: exploration of normal range among pediatric patients

INTRODUCTION

While ¹⁸F-FDG PET/CT pediatrics applications have increased in number and indications, few studies have addressed normal maximum standardized uptake values (SUV_max) of referral organs in children. The purpose of this study is to assess these in a cohort of pediatric patients.

MATERIAL AND METHODS

285 ¹⁸F-FDG PET/CT scans in 229 patients were reviewed. SUV_max were assessed for mediastinal blood pool (MBP), thymus (T), liver (L), spleen (S), bone marrow (BM) and Waldeyer's Ring (Wald). L/MBP and S/L ratios were calculated. Same day complete blood counts (CBC) were available for 132 studies and compared to BM and S. Means, standard deviations and correlation coefficients with age, weight and body surface area (BSA) were calculated.

RESULTS

Weak correlation with age, weight or BSA was found for Wald. Strong correlations with weight/BSA more than with age were demonstrated for MBP, L and BM and moderate for S and T. After initial decrease between age 0 and 2, thymic activity peaked at age 11 years then involuted. No correlation was found between CBC ad BM or S. In 28 studies, L was less or equal to MBP. In 74 S was superior to L.

CONCLUSIONS

Referral organs ¹⁸F-FDG uptake varies in children more in relation with weight and BSA than with age for key referral organs, such as L, S and MBP. In a significant number of studies, L activity may impede evaluation of treatment response in comparison with MBP or inflammation/infection evaluation in comparison with S.

Follow-up PET/CT of alveolar echinococcosis: Comparison of metabolic activity and immunodiagnostic testing

Purpose

To investigate the potential role of follow-up ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in therapy control of inoperable patients with alveolar echinococcosis.

Materials and methods

In this single-center retrospective cohort study, 48 PET/CT of 16 patients with confirmed alveolar echinococcosis were analysed. FDG-uptake of the most active echinococcosis manifestation was measured (i.e., maximum standardized uptake value (SUVmax) and in relation to background activity in normal liver tissue (SUVratio)) and compared to immunodiagnostic testing. For clinical patient follow-up, patient demographics, laboratory data, including E. granulosus hydatid fluid (EgHF) antibody units (AU) as well as clinical and treatment information were assessed for all patients at the time of PET/CT, and at the last recorded clinical visit.

Results

Metabolic activity of PET/CT measured in the echinococcosis manifestation was significantly correlated with EgHF AU (p < 0.001). The differences in metabolic activity of echinococcosis manifestations between two consecutive PET/CT examinations of the same patient and differences in EgHF AU in the respective time intervals displayed a significant positive correlation (p = 0.01). A trend for a more rapid decline in SUVratio liver over time was found in patients who stopped benzimidazole therapy versus patients who did not stop therapy (p = 0.059).

Conclusion

In inoperable patients with alveolar echinococcosis, the course of metabolic activity in follow-up PET/CT is associated to the course EgHF antibody levels. Both parameters may potentially be used to evaluate the course of the disease and potentially predict the duration of benzimidazole therapy.

SUVfdg: A standard-uptake-value (SUV) body habitus normalizer specific to fluorodeoxyglucose (FDG) in humans

Purpose

To devise a new body-habitus normalizer to be used in the calculation of an SUV that is specific to the PET tracer 18F-FDG.

Methods

A cohort of 481-patients was selected for analysis of 18F-FDG uptake into tissues unaffected by their disease. Among these, 65-patients had only brain concentrations measured and the remaining 416 were randomly divided into an 86-patient test set and a 330-patient training set. Within the test set, normal liver, spleen and blood measures were made. In the training set, only normal liver concentrations were measured. Using data from the training set, a simple polynomial function of height and weight was selected and optimized in a fitting procedure to predict each patient’s mean liver %ID/ml. This function, when used as a normalizer, defines a new SUV metric (SUVfdg) which we compared to SUV metrics normalized by body weight (SUVbw), lean-body mass (SUVlbm) and body surface-area (SUVbsa) in a five-fold cross-validation. SUVfdg was also evaluated in the independent brain-only and whole-body test sets.

Results

For patients of all sizes including pediatric patients, the normal range of liver 18F-FDG uptake at 60 minutes post injection in units of SUVfdg is 1.0 ± 0.16. Liver, blood, and spleen SUVfdg in all comparisons had lower coefficients of variation compared to SUVbw SUVlbm and SUVbsa. Blood had a mean SUVfdg of 0.8 ± 0.11 and showed no correlation with age, height, or weight. Brain SUVfdg measures were significantly higher (P<0.01) in pediatric patients (4.7 ± 0.9) compared to adults (3.1 ± 0.6).

Conclusion

A new SUV metric, SUVfdg, is proposed. It is hoped that SUVfdg will prove to be better at classifying tumor lesions compared to SUV metrics in current use. Other tracers may benefit from similarly tracer-specific body habitus normalizers.

Normal values for 18F-FDG uptake in organs and tissues measured by dynamic whole body multiparametric FDG PET in 126 patients

BACKGROUND

Dynamic whole-body (D-WB) FDG PET/CT is a recently developed technique that allows direct reconstruction of multiparametric images of metabolic rate of FDG uptake (MR_FDG) and "free" FDG (DV_FDG). Multiparametric images have a markedly different appearance than the conventional SUV images obtained by static PET imaging, and normal values of MR_FDG and DV_FDG in frequently used reference tissues and organs are lacking. The aim of this study was therefore to: (1) provide an overview of normal MR_FDG and DV_FDG values and range of variation in organs and tissues; (2) analyse organ time-activity curves (TACs); (3) validate the accuracy of directly reconstructed MR_FDG tissue values versus manually calculated K_i (and MR_FDG) values; and (4) explore correlations between demographics, blood glucose levels and MR_FDG values. D-WB data from 126 prospectively recruited patients (100 without diabetes and 26 with diabetes) were retrospectively analysed. Participants were scanned using a 70-min multiparametric PET acquisition protocol on a Siemens Biograph Vision 600 PET/CT scanner. 13 regions (bone, brain grey and white matter, colon, heart, kidney, liver, lung, skeletal muscle of the back and thigh, pancreas, spleen, and stomach) as well as representative pathological findings were manually delineated, and values of static PET (SUV), D-WB PET (K_i, MR_FDG and DV_FDG) and individual TACs were extracted. Multiparametric values were compared with manual TAC-based calculations of K_i and MR_FDG, and correlations with blood glucose, age, weight, BMI, and injected tracer dose were explored.

RESULTS

Tissue and organ MR_FDG values showed little variation, comparable to corresponding SUV variation. All regional TACs were in line with previously published FDG kinetics, and the multiparametric metrics correlated well with manual TAC-based calculations (r² = 0.97, p < 0.0001). No correlations were observed between glucose levels and MR_FDG in tissues known not to be substrate driven, while tissues with substrate driven glucose uptake had significantly correlated glucose levels and MR_FDG values.

CONCLUSION

The multiparametric D-WB PET scan protocol provides normal MR_FDG values with little inter-subject variation and in agreement with manual TAC-based calculations and literature values. The technique therefore facilitates both accurate clinical reports and simpler acquisition of quantitative estimates of whole-body tissue glucose metabolism.

Influences on PET Quantification and Interpretation

Various factors have been identified that influence quantitative accuracy and image interpretation in positron emission tomography (PET). Through the continuous introduction of new PET technology—both imaging hardware and reconstruction software—into clinical care, we now find ourselves in a transition period in which traditional and new technologies coexist. The effects on the clinical value of PET imaging and its interpretation in routine clinical practice require careful reevaluation. In this review, we provide a comprehensive summary of important factors influencing quantification and interpretation with a focus on recent developments in PET technology. Finally, we discuss the relationship between quantitative accuracy and subjective image interpretation.

Cerebellum/liver index in pretherapeutic 18F-FDG PET/CT as a predictive marker of progression-free survival in follicular lymphoma treated by immunochemotherapy and rituximab maintenance

The purpose of this study was to investigate the value of the "cerebellum/ liver index for prognosis" (CLIP) as a new prognostic marker in pretherapeutic 18F-Fluorodeoxyglucose positron emission tomography (18F-FDG PET) in patients with follicular lymphoma treated by immunochemotherapy and rituximab maintenance, focusing on progression-free survival (PFS).Clinicobiological and imaging data from patients with follicular lymphoma between March 2010 and September 2015 were retrospectively collected and 5-year PFS was determined. The conventional PET parameters (maximum standardized uptake value and total metabolic tumor volume) and the CLIP, corresponding to the ratio of the cerebellum maximum standardized uptake value over the liver SUVmean, were extracted from the pretherapeutic 18F-FDG PET.Forty-six patients were included. Eighteen patients (39%) progressed within the 5 years after treatment initiation. Five-year PFS was 78.6% when CLIP was >4.0 and 42.0% when CLIP was <4.0 (P = .04). CLIP was a significant predictor of PFS on univariate analysis (hazard ratio 3.1, P = .049) and was near-significant on multivariate analysis (hazard ratio 2.8, P = .07) with ECOG PS as a cofactor.The CLIP derived from pretherapeutic 18F-FDG PET seems to be an interesting predictive marker of PFS in follicular lymphoma treated by immunochemotherapy and rituximab maintenance. These results should be evaluated prospectively in a larger cohort.

EANM procedure guidelines for brain PET imaging using [18F]FDG, version 3

The present procedural guidelines summarize the current views of the EANM Neuro-Imaging Committee (NIC). The purpose of these guidelines is to assist nuclear medicine practitioners in making recommendations, performing, interpreting, and reporting results of [¹⁸F]FDG-PET imaging of the brain. The aim is to help achieve a high-quality standard of [¹⁸F]FDG brain imaging and to further increase the diagnostic impact of this technique in neurological, neurosurgical, and psychiatric practice. The present document replaces a former version of the guidelines that have been published in 2009. These new guidelines include an update in the light of advances in PET technology such as the introduction of digital PET and hybrid PET/MR systems, advances in individual PET semiquantitative analysis, and current broadening clinical indications (e.g., for encephalitis and brain lymphoma). Further insight has also become available about hyperglycemia effects in patients who undergo brain [¹⁸F]FDG-PET. Accordingly, the patient preparation procedure has been updated. Finally, most typical brain patterns of metabolic changes are summarized for neurodegenerative diseases. The present guidelines are specifically intended to present information related to the European practice. The information provided should be taken in the context of local conditions and regulations.

Characteristics of Physiological 18F-Fluoro-2-Deoxy-D-Glucose Uptake and Comparison Between Cats and Dogs With Positron Emission Tomography

This study aimed to identify the physiological 18F-fluoro-2-deoxy-D-glucose (FDG) uptake in cats using positron emission tomography/computed tomography (PET/CT) and determine its characteristics by comparing physiological differences with dogs. Seven healthy cats and six healthy beagle dogs were examined using FDG-PET/CT. Regions of interest (ROIs) were manually drawn over 41 detailed structures of 5 gross structures (brain, head and neck, musculoskeleton, thorax, and abdomen). The mean and maximum standard uptake values (SUVmean and SUVmax) were calculated for each ROI. Physiological variation was classified as having increased radiopharmaceutical activity with no evidence of abnormal clinical or radiological findings. The brain had the highest SUV, which was observed in the cerebellum of both cats (SUVmean: 4.90 ± 1.04, SUVmax: 6.04 ± 1.24) and dogs (SUVmean: 3.15 ± 0.57, SUVmax: 3.90 ± 0.74). Cats had a significantly higher intracranial uptake than dogs did (P < 0.01). In the digestive system, the SUVs of the duodenum and jejunum were significantly higher in dogs than in cats (P < 0.05). FDG uptake of the submandibular tip, tonsils, neck of the gallbladder, and caudal colliculus were physiologically increased in cats. This study demonstrates physiological FDG uptake in normal tissues, and the differences between cats and dogs were interpreted based on species-specificity. This information contributes to improving the accurate diagnosis of cancer in cats and will aid in understanding glucose metabolism in both cats and dogs.

Impact of unknown incidental findings in PET/CT examinations of patients with proven or suspected vascular graft or endograft infections

Vascular graft or endograft Infections (VGEI) are rare but severe complications of vascular reconstructive surgery, and associated with significant mortality and morbidity risk. Positron emission tomography/computed tomography with ¹⁸F-fluorodeoxyglucose (PET/CT) has been shown to have a high diagnostic accuracy in the detection of VGEI. In this single-center prospective cohort study, we assessed the rate and the impact on patient management of relevant unknown incidental findings in PET/CT of patients with proven or suspected VGEI, and clinical follow-up of all patients was performed. Our study results show a comparably high rate of relevant unknown incidental findings (181 in 502 examinations), with documented direct impact on patient management in 80 of 181 (44%) of all findings. PET/CT scan- and patient-based evaluation revealed impact on patient management in 76 of 502 (17%) of all PET/CT scans, and in 59 of 162 (36%) of all patients, respectively. Furthermore, PET/CT correctly identified the final diagnosis in 20 of 36 (56%) patients without VGEI. In conclusion, in proven and suspected VGEI, PET/CT detects a high rate of relevant unknown incidental findings with high impact on patient management.

PET/CT in therapy control of infective native aortic aneurysms

Infective native aortic aneurysms (INAA) are aneurysms arising from infection of the aortic wall. Treatment is demanding with 5-year survival rates between 53 and 55%. The aim of our study was to evaluate the usefulness of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) in the long-term monitoring of patients with proven INAA. Fifty-three PET/CT were performed in 15 patients with INAA in this single-center retrospective cohort study and retrospective analysis of prospectively collected Vascular Graft Cohort Study (VASGRA) data. Median metabolic activity (as measured by maximum standardized uptake value, SUVmax) of the aneurysms at the initial PET/CT was high (6.8 (IQR 5.7–21.8)), and lower at the last PET/CT prior to the end of antimicrobial therapy (3.9 (IQR 2.7–6.8); n = 11) as well as in the first PET/CT after the end of the treatment (3.9 (IQR 3.0–4.4);n = 6). Compared to the course of C-reactive protein alone, PET/CT provided different (> 20% difference in trend) or altering (opposed trend) information on the course of disease in at least 14 comparisons (56%) in 11 patients (73%). The one-year and five-year freedom from all-cause lethality was 92% (95% confidence interval 57%-99%). As compared to the course of C-reactive protein, PET/CT provides different and occasionally altering information in therapy control of INAA.

Recommendations for Standardizing Thorax PET-CT in Non-Human Primates by Recent Experience from Macaque Studies

Despite the possibilities of routine clinical measures and assays on readily accessible bio-samples, it is not always essential in animals to investigate the dynamics of disease longitudinally. In this regard, minimally invasive imaging methods provide powerful tools in preclinical research. They can contribute to the ethical principle of gathering as much relevant information per animal as possible. Besides, with an obvious parallel to clinical diagnostic practice, such imaging platforms are potent and valuable instruments leading to a more refined use of animals from a welfare perspective. Non-human primates comprise highly relevant species for preclinical research to enhance our understanding of disease mechanisms and/or the development of improved prophylactic or therapeutic regimen for various human diseases. In this paper, we describe parameters that critically affect the quality of integrated positron emission tomography and computed tomography (PET-CT) in non-human primates. Lessons learned are exemplified by results from imaging experimental infectious respiratory disease in macaques; specifically tuberculosis, influenza, and SARS-CoV-2 infection. We focus on the thorax and use of 18F-fluorodeoxyglucose as a PET tracer. Recommendations are provided to guide various stages of PET-CT-supported research in non-human primates, from animal selection, scan preparation, and operation, to processing and analysis of imaging data.

Brain control of blood glucose levels: implications for the pathogenesis of type 2 diabetes

Despite a rapidly growing literature, the role played by the brain in both normal glucose homeostasis and in type 2 diabetes pathogenesis remains poorly understood. In this review, we introduce a framework for understanding the brain's essential role in these processes based on evidence that the brain, like the pancreas, is equipped to sense and respond to changes in the circulating glucose level. Further, we review evidence that glucose sensing by the brain plays a fundamental role in establishing the defended level of blood glucose, and that defects in this control system contribute to type 2 diabetes pathogenesis. We also consider the possibility that the close association between obesity and type 2 diabetes arises from a shared defect in the highly integrated neurocircuitry governing energy homeostasis and glucose homeostasis. Thus, whereas obesity is characterised by an increase in the defended level of the body's fuel stores (e.g. adipose mass), type 2 diabetes is characterised by an increase in the defended level of the body's available fuel (e.g. circulating glucose), with the underlying pathogenesis in each case involving impaired sensing of (or responsiveness to) relevant humoral negative feedback signals. This perspective is strengthened by growing preclinical evidence that in type 2 diabetes the defended level of blood glucose can be restored to normal by therapies that restore the brain's ability to properly sense the circulating glucose level. Graphical abstract.

Patient Preparation and Patient-related Challenges with FDG-PET/CT in Infectious and Inflammatory Disease

Several factors that influence physiologic 18F-fluorodeoxyglucose (FDG) uptake and general FDG distribution may affect PET/CT imaging in infection and inflammation. The general impact of hyperglycemia on the diagnostic performance of FDG-PET/CT is probably less in infection/inflammation than in malignancy. Patient preparation may reduce physiologic FDG uptake, but recommendations are less established than in malignancy. Local implementation of various patient preparatory measures should reflect the specific patient population and indications. This article outlines some of the challenges with physiologic FDG distribution, focusing on infectious and inflammatory diseases, and potential countermeasures and patient preparation to limit physiologic uptake before scan.

Clinical implications of increased uptake in bone marrow and spleen on FDG-PET in patients with bacteremia

PURPOSE

To investigate which clinical factors and laboratory values are associated with high FDG uptake in the bone marrow and spleen on 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography (PET)/computed tomography (CT) in patients with bacteremia.

METHODS

One hundred forty-five consecutive retrospective patients with bacteremia who underwent FDG-PET/CT between 2010 and 2017 were included. Mean standard uptake values (SUV_mean) of FDG in bone marrow, liver, and spleen were measured. Bone marrow-to-liver SUV ratios (BLR) and spleen-to-liver SUV ratios (SLR) were calculated. Linear regression analyses were performed to examine the association of BLR and SLR with age, gender, hemoglobin, leukocyte count, platelets, glucose level, C-reactive protein (CRP), microorganism, days of antibiotic treatment before FDG-PET/CT, infection focus, use of immunosuppressive drugs, duration of hospital stay (after FDG-PET/CT), ICU admission, and mortality.

RESULTS

C-reactive protein (p = 0.006), a cardiovascular or musculoskeletal focus of infection (p = 0.000 for both), and bacteremia caused by Gram-negative bacteria (p = 0.002) were independently and positively associated with BLR, while age (p = 0.000) and glucose level before FDG-PET/CT (p = 0.004) were independently and negatively associated with BLR. For SLR, CRP (p = 0.001) and a cardiovascular focus of infection (p = 0.020) were independently and positively associated with SLR, while age (p = 0.002) and glucose level before FDG-PET/CT (p = 0.016) were independently and negatively associated with SLR.

CONCLUSION

High FDG uptake in the bone marrow is associated with a higher inflammatory response and younger age in patients with bacteremia. In patients with high FDG uptake in the bone marrow, a cardiovascular or musculoskeletal focus of infection is more likely than other foci, and the infection is more often caused by Gram-negative species. High splenic FDG uptake is associated with a higher inflammatory response as well, and a cardiovascular focus of infection is also more likely in case of high splenic FDG uptake.

Borderline Resectable and Locally Advanced Pancreatic Cancer: FDG PET/MRI and CT Tumor Metrics for Assessment of Pathologic Response to Neoadjuvant Therapy and Prediction of Survival

BACKGROUND. Imaging biomarkers of response to neoadjuvant therapy (NAT) for pancreatic ductal adenocarcinoma (PDA) are needed to optimize treatment decisions and long-term outcomes. OBJECTIVE. The purpose of this study was to investigate metrics from PET/MRI and CT to assess pathologic response of PDA to NAT and to predict overall survival (OS). METHODS. This retrospective study included 44 patients with ¹⁸F-FDG-avid borderline resectable or locally advanced PDA on pretreatment PET/MRI who also underwent post-NAT PET/MRI before surgery between August 2016 and February 2019. Carbohydrate antigen 19-9 (CA 19-9) level, metabolic metrics from PET/MRI, and morphologic metrics from CT (n = 34) were compared between pathologic responders (College of American Pathologists scores 0 and 1) and nonresponders (scores 2 and 3). AUCs were measured for metrics significantly associated with pathologic response. Relation to OS was evaluated with Cox proportional hazards models. RESULTS. Among 44 patients (22 men, 22 women; mean age, 62 ± 11.6 years), 19 (43%) were responders, and 25 (57%) were nonresponders. Median OS was 24 months (range, 6-42 months). Before treatment, responders and nonresponders did not differ in CA 19-9 level, metabolic metrics, or CT metrics (p > .05). After treatment, responders and nonresponders differed in complete metabolic response (CMR) (responders, 89% [17/19]; nonresponders, 40% [10/25]; p = .04], mean change in SUV_max (ΔSUV_max; responders, -70% ± 13%; nonresponders, -37% ± 42%; p < .001), mean change in SUV_max corrected to serum glucose level (ΔSUV_gluc) (responders, -74% ± 12%; nonresponders, -30% ± 58%; p < .001), RECIST response on CT (responders, 93% [13/14]; nonresponders, 50% [10/20]; p = .02)], and mean change in tumor volume on CT (ΔTvol) (responders, -85% ± 21%; nonresponders, 57% ± 400%; p < .001). The AUC of CMR for pathologic response was 0.75; ΔSUV_max, 0.83; ΔSUV_gluc, 0.87; RECIST, 0.71; and ΔTvol 0.86. The AUCs of bivariable PET/MRI and CT models were 0.83 (CMR and ΔSUV_max), 0.87 (CMR and ΔSUV_gluc), and 0.87 (RECIST and ΔTvol). OS was associated with CMR (p = .03), ΔSUV_max (p = .003), ΔSUV_gluc (p = .003), and RECIST (p = .046). CONCLUSION. Unlike CA 19-9 level, changes in metabolic metrics from PET/MRI and morphologic metrics from CT after NAT were associated with pathologic response and OS in patients with PDA, warranting prospective validation. CLINICAL IMPACT. Imaging metrics associated with pathologic response and OS in PDA could help guide clinical management and outcomes for patients with PDA who undergo emergency therapeutic interventions.

Thalamic pulvinar metabolism, sleep disturbances, and hallucinations in dementia with Lewy bodies: Positron emission tomography and actigraphy study

OBJECTIVES

Although sleep disturbances are prevalent among patients with dementia with Lewy bodies (DLB), their neural substrates remain unclear. We aimed to clarify the neural substrates of sleep disturbances in patients with DLB.

METHODS

We evaluated sleep disturbances, neuropsychiatric symptoms, and brain glucose metabolism in 22 patients with probable DLB using actigraphy, the Neuropsychiatric Inventory (NPI), and ¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography, respectively. Total sleep time (TST) and average activity count per minute (AAC) during sleep were calculated for seven consecutive days via actigraphy. We investigated associations between FDG uptake and the actigraphy parameters using Statistical Parametric Mapping version 12b. Spearman's rank correlation coefficients were used to investigate associations among TST, AAC, and clinical symptoms. The level of statistical significance was set at P < .05. P values were adjusted using the Benjamini-Hochberg method for multiple comparisons. This study was registered with ClinicalTrials.gov (NCT00776347).

RESULTS

TST exhibited a significant positive association with FDG uptake in the bilateral orbitofrontal cortex and left thalamus, while AAC exhibited a significant negative association with FDG uptake in the left thalamus and the left parieto-occipital region. FDG uptake in the left pulvinar was associated with both TST and AAC. In addition, TST exhibited a significant negative association with the NPI hallucinations score (r = -0.66, P = .001), while AAC exhibited significant positive associations with the NPI delusions (r = 0.70, P < .001) and hallucinations (r = 0.63, P = .002) scores.

CONCLUSIONS

TST and bodily activity during sleep are associated with dysfunction of the left pulvinar and the severity of hallucinations in patients with DLB.

Glucose Loading Enhances the Value of 18F-FDG PET/CT for the Characterization and Delineation of Cerebral Gliomas

This study aimed to assess how to enhance the value of ¹⁸F-Fluorodeoxyglucose (FDG) PET/CTs for glioma grading and better delineation of the tumor boundary by glucose loading. In mouse models of brain tumor using U87MG cells, ¹⁸F-FDG-PET images were obtained after fasting and after glucose loading. There was a significant difference in the tumor-to-normal cortex-uptake ratio (TNR) between the fasting and glucose-loading scans. ¹⁴C-2-Deoxy-D-glucose (¹⁴C-DG) uptake was measured in vitro using U87MG, U373MG and primary neurons cultured with different concentrations of glucose. The tumor-to-neuron ratio of ¹⁴C-DG uptake increased with up to 10 mM of glucose. Finally, 10 low-grade and 17 high-grade glioma patients underwent fasting and glucose loading ¹⁸F-FDG PET/CT and the TNR was compared between scans. The effect of glucose loading was significant in high-grade but not in low-grade gliomas. The receiver operating characteristic curve analyses with a cut-off TNR of 0.81 showed a higher area under the curve after glucose loading than fasting for differentiating low-grade versus high-grade gliomas. In addition, the glucose loading PET/CT was more useful than the fasting PET/CT for the discrimination of oligodendrogliomas from IDH-wildtype glioblastomas. Glucose loading resulted in a greater reduction in ¹⁸F-FDG uptake in the normal cortex than in tumors, which increases the usefulness of ¹⁸F-FDG PET/CT for grading.

Frontiers in positron emission tomography imaging of the vulnerable atherosclerotic plaque

Rupture of vulnerable atherosclerotic plaques leading to an atherothrombotic event is the primary driver of myocardial infarction and stroke. The ability to detect non-invasively the presence and evolution of vulnerable plaques could have a huge impact on the future identification and management of atherosclerotic cardiovascular disease. Positron emission tomography (PET) imaging with an appropriate radiotracer has the potential to achieve this goal. This review will discuss the biological hallmarks of plaque vulnerability before going on to evaluate and to present PET imaging approaches which target these processes. The focus of this review will be on techniques beyond [18F]FDG imaging, some of which are clinically advanced, and others which are on the horizon. As inflammation is the primary driving force behind atherosclerotic plaque development, we will predominantly focus on approaches which either directly, or indirectly, target this process.

Understanding multifactorial brain changes in type 2 diabetes: a biomarker perspective

People with type 2 diabetes are at an increased risk of cognitive impairment and dementia (including Alzheimer's disease), as well as subtle forms of cognitive dysfunction. Current diabetes guidelines recommend screening for cognitive impairment in groups at high risk and providing guidance for diabetes management in patients with diabetes and cognitive impairment. Yet, no disease-modifying treatment is available and important questions remain about the mechanisms underlying diabetes-associated cognitive dysfunction. These mechanisms are likely to be multifactorial and different for subtle and more severe forms of diabetes-associated cognitive dysfunction. Over the past years, research on dementia, brain ageing, diabetes, and vascular disease has identified novel biomarkers of specific dementia aetiologies, brain parenchymal injury, and cerebral blood flow and metabolism. These markers shed light on the processes underlying diabetes-associated cognitive dysfunction, have clear applications in current research and increasingly in clinical diagnosis, and might ultimately guide targeted treatment.

The Elusive Link Between Cancer FDG Uptake and Glycolytic Flux Explains the Preserved Diagnostic Accuracy of PET/CT in Diabetes

This study aims to verify in experimental models of hyperglycemia induced by streptozotocin (STZ-DM) to what degree the high competition between unlabeled glucose and metformin (MET) treatment might affect the accuracy of cancer FDG imaging. The study included 36 “control” and 36 “STZ-DM” Balb/c mice, undergoing intraperitoneal injection of saline or streptozotocin, respectively. Two-weeks later, mice were subcutaneously implanted with breast (4 T1) or colon (CT26) cancer cells and subdivided in three subgroups for treatment with water or with MET at 10 or 750 mg/Kg/day. Two weeks after, mice were submitted to micro-PET imaging. Enzymatic pathways and response to oxidative stress were evaluated in harvested tumors. Finally, competition by glucose, 2-deoxyglucose (2DG) and the fluorescent analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) on FDG uptake was studied in 4 T1 and CT26 cultured cells. STZ-DM slightly decreased cancer volume and FDG uptake rate (MRF). More importantly, it also abolished MET capability to decelerate lesion growth and MRF. This metabolic reprogramming closely agreed with the activity of hexose-6-phosphate dehydrogenase within the endoplasmic reticulum. Finally, co-incubation with 2DG virtually abolished FDG and 2-NBDG uptake within the endoplasmic reticulum in cultured cells. These data challenge the current dogma linking FDG uptake to glycolytic flux and introduce a new model to explain the relation between glucose analogue uptake and hexoses reticular metabolism. This selective fate of FDG contributes to the preserved sensitivity of PET imaging in oncology even in chronic moderate hyperglycemic conditions.

HYPHYCA: a prospective study in 613 patients conducting a comprehensive analysis for predictive factors of physiological 18F-FDG anal uptake

Background

Anal cancer is a relatively rare tumor of which incidence increases in developed countries. ¹⁸F-FDG PET has been increasingly used for its post radio-chemotherapy evaluation. However, several authors have reported the risk of local false-positive findings leading to low specificity and positive predictive values. These false-positive results could be due to post-radiotherapy inflammation or infection but certainly also to physiological anal canal uptake that is observed on a regular basis in clinical practice. The purpose of this prospective study (NCT03506529; HYPHYCA) was therefore to seek predictive factors of physiological anal canal hypermetabolism.

Materials and methods

Over a 2-month period, patients aged 18 years old and more, referred for ¹⁸F-FDG PET-CT at two EARL-accredited PET centers were included, after obtaining their informed and written consent. They were asked to fill in a questionnaire including seven closed questions about usual intestinal transit, ongoing medications relative to intestinal transit, history of digestive, and anal and/or pelvic diseases. Age, gender, and body mass index (BMI) were recorded. A single nuclear medicine physician visually and quantitatively analyzed anal canal uptake (SUV_{max_EARL}) and assessed visual rectal content (air, feces, or both) and the largest rectal diameter (mm).

Results

Six hundred and thirteen patients were included (sex ratio F/M = 0.99) and 545 (89%) questionnaires were entirely completed. Significantly more males presented anal canal hypermetabolism (sex ratio (M/F) = 1.18 versus 0.85, p = 0.048). Moreover, patients with anal canal hypermetabolism had higher BMI (27.6 (5.7) kg/m² versus 23.9 (4.5) kg/m², p < 0.0001), higher rate of hemorrhoid history (43% versus 27%, p = 0.016), and higher rate of rectum filled with only feces (21% versus 12%, p = 0.019) as compared to patients with no anal canal uptake. On logistic regression, all these variables were found to be independent predictors of the occurrence of an anal canal hypermetabolism. Odds ratio were 1.16 (1.12–1.20) per unit of BMI (kg/m²) (p < 0.0001), 1.48 (1.04–2.11) for males (p = 0.030), 1.64 (1.10–2.45) for hemorrhoids history (p = 0.016), and 1.94 (1.147–3.22) for the rectum filled with only feces (p = 0.010).

Conclusion

According to our study, the predictive factors of physiological anal canal hypermetabolism are high BMI, male gender, hemorrhoid history, and rectum filled with only feces. This may pave the way to a more specific interpretation of post radio-chemotherapy PET evaluations of anal canal cancer, provided that other studies are conducted in this specific population.

Trial registration

This prospective study was registered at Clinicaltrial.gov: NCT03506529; HYPHYCA on April 24, 2018

Hyperglycemia and 18F-FDG PET/CT, issues and problem solving: a literature review

Positron emission tomography/computed tomography (PET/CT) is a standard procedure for imaging cancer commonly used in the clinical practice for several diseases, in particular for cancer staging, restaging, treatment monitoring and radiation therapy planning. Despite the availability of many radiotracers, 18F-fluoro-2-deoxy-2-D-glucose ([18F]FDG) is the most used. International PET/CT guidelines propose protocols for patients' correct preparation before [18F]FDG injection, in particular with the regard of diabetic patients and therapy management. Hyperglycemic conditions and oral or insulin medication showed advantages and disadvantages on PET/CT scan accuracy: A correct knowledge of effects of these conditions on glucose metabolism assumes a fundamental role on patients management before [18F]FDG PET/CT scan.

Usefulness of Hybrid PET/MRI in Clinical Evaluation of Head and Neck Cancer Patients

(1) Background: The novel hybrid of positron emission tomography/magnetic resonance (PET/MR) examination has been introduced to clinical practice. The aim of our study was to evaluate PET/MR usefulness in preoperative staging of head and neck cancer (HNC) patients (pts); (2) Methods: Thirty eight pts underwent both computed tomography (CT) and PET/MR examination, of whom 21 pts underwent surgical treatment as first-line therapy and were further included in the present study. Postsurgical tissue material was subjected to routine histopathological (HP) examination with additional evaluation of p16, human papillomavirus (HPV), Epstein-Barr virus (EBV) and Ki67 status. Agreement of clinical and pathological T staging, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of CT and PET/MR in metastatic lymph nodes detection were defined. The verification of dependences between standardized uptake value (SUV value), tumor geometrical parameters, number of metastatic lymph nodes in PET/MR and CT, biochemical parameters, Ki67 index, p16, HPV and EBV status was made with statistical analysis of obtained results; (3) Results: PET/MR is characterized by better agreement in T staging, higher specificity, sensitivity, PPV and NPV of lymph nodes evaluation than CT imaging. Significant correlations were observed between SUVmax and maximal tumor diameter from PET/MR, between SUVmean and CT tumor volume, PET/MR tumor volume, maximal tumor diameter assessed in PET/MR. Other correlations were weak and insignificant; (4) Conclusions: Hybrid PET/MR imaging is useful in preoperative staging of HNC. Further studies are needed.

Factors influencing incidental 18F-FDG uptake in the gallbladder in a large cohort of patients: A retrospective study

OBJECTIVES

This study aims to assess the incidence of incidental activity in the gallbladder and the factors that may contribute to it in a large cohort of patients undergoing ¹⁸F-fluorodeoxyglucose-PET/CT for cancer evaluation.

METHODS

8096 PET/CTs were retrospectively reviewed. Data pertaining to patient demographics and PET/CT parameters were collected. Patients' records were reviewed for gallbladder disorders for up to 3 years after the exam. The presence/absence of gallbladder uptake was visually assessed. Findings were classified as focal, diffuse increased and diffuse increased wall uptake, or no uptake. Volumetric measurements of the gallbladder and SUVmax of the gallbladder, liver and blood pool were measured. Chi-square and Student's t-test were used for statistical analysis.

RESULTS

54 cases (0.67%) of incidental gallbladder uptake were detected (uptake group). 162 exams without uptake were selected as control (no uptake group). The injection-to-scan interval, SUVmax of the liver and blood pool, and the gallbladder volume did not differ significantly between both groups. Higher blood glucose levels were observed in the uptake (109.9 ± 32.5) vs. no uptake group (97.4 ± 18) (p = 0.01), with levels >150 mg/dL more common in the uptake group (p = 0.004). The incidence of gallbladder disease within 3 years after imaging was higher for the uptake group (12/36) compared to the no uptake group (15/115) (p = 0.02). Diffuse increased wall uptake was more likely in the group who later developed a pathology (4/12) (p = 0.03).

CONCLUSION

Incidental gallbladder uptake in patients is independent of the injected FDG dose, injection-to-scan interval or gallbladder volume, but may be related to blood glucose level. There's a higher incidence of gallbladder pathology three years after the exam particularly in cases of diffuse increased wall uptake.