Effects of blood glucose level on FDG uptake by liver: a FDG-PET/CT study

A fluorescence probe for imaging lipid droplet and visualization of diabetes-related polarity variations

Diabetes mellitus is a disorder that affects lipid metabolism. Abnormalities in the lipid droplets (LDs) can lead to disturbances in lipid metabolism, which is a significant feature of diabetic patients. Nevertheless, the correlation between diabetes and the polarity of LDs has received little attention in the scientific literature. In order to detect LDs polarity changes in diabetes illness models, we created a new fluorescence probe LD-DCM. This probe has a stable structure, high selectivity, and minimal cytotoxicity. The probe formed a typical D-π-A molecular configuration with triphenylamine (TPA) and dicyanomethylene-4H-pyran (DCM) as electron donor and acceptor parts. The LD-DCM molecule has an immense solvatochromic effect (λem = 544-624 nm), fluorescence enhancement of around 150 times, and a high sensitivity to polarity changes within the linear range of Δf = 0.28 to 0.32, all due to its distinctive intramolecular charge transfer effect (ICT). In addition, LD-DCM was able to monitor the accumulation of LDs and the reduction of LDs polarity in living cells when stimulated by oleic acid, lipopolysaccharide, and high glucose. More importantly, LD-DCM has also been used effectively to detect polarity differences in organs from diabetic, drug-treated, and normal mice. The results showed that the liver polarity of diabetic mice was lower than that of normal mice, while the liver polarity of drug-treated mice was higher than that of diabetic mice. We believe that LD-DCM has the potential to serve as an efficient instrument for the diagnosis of disorders that are associated with the polarity of LDs.

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.

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.

Reproducibility of [18F]FDG PET/CT liver SUV as reference or normalisation factor

INTRODUCTION

Although visual and quantitative assessments of [18F]FDG PET/CT studies typically rely on liver uptake value as a reference or normalisation factor, consensus or consistency in measuring [18F]FDG uptake is lacking. Therefore, we evaluate the variation of several liver standardised uptake value (SUV) measurements in lymphoma [18F]FDG PET/CT studies using different uptake metrics.

METHODS

PET/CT scans from 34 lymphoma patients were used to calculate SUVmaxliver, SUVpeakliver and SUVmeanliver as a function of (1) volume-of-interest (VOI) size, (2) location, (3) imaging time point and (4) as a function of total metabolic tumour volume (MTV). The impact of reconstruction protocol on liver uptake is studied on 15 baseline lymphoma patient scans. The effect of noise on liver SUV was assessed using full and 25% count images of 15 lymphoma scans.

RESULTS

Generally, SUVmaxliver and SUVpeakliver were 38% and 16% higher compared to SUVmeanliver. SUVmaxliver and SUVpeakliver increased up to 31% and 15% with VOI size while SUVmeanliver remained unchanged with the lowest variability for the largest VOI size. Liver uptake metrics were not affected by VOI location. Compared to baseline, liver uptake metrics were 15-18% and 9-18% higher at interim and EoT PET, respectively. SUVliver decreased with larger total MTVs. SUVmaxliver and SUVpeakliver were affected by reconstruction protocol up to 62%. SUVmax and SUVpeak moved 22% and 11% upward between full and 25% count images.

CONCLUSION

SUVmeanliver was most robust against VOI size, location, reconstruction protocol and image noise level, and is thus the most reproducible metric for liver uptake. The commonly recommended 3 cm diameter spherical VOI-based SUVmeanliver values were only slightly more variable than those seen with larger VOI sizes and are sufficient for SUVmeanliver measurements in future studies.

TRIAL REGISTRATION

EudraCT: 2006-005,174-42, 01-08-2008.

Improvement of liver metabolic activity in people with advanced HIV after antiretroviral therapy initiation

OBJECTIVE

Evaluating hepatic metabolic changes in people with HIV (PWH) with advanced disease, before and after antiretroviral therapy (ART) initiation, using [ 18 F]-fluorodeoxyglucose (FDG) PET-computed tomography (PET/CT). FDG PET/CT noninvasively quantifies glucose metabolism in organs.

DESIGN/METHODS

Forty-eight viremic PWH (CD4 + cell counts <100 cells/μl) underwent FDG PET/CT at baseline and approximately 6 weeks after ART initiation (short-term). Twenty-seven PWH participants underwent follow-up scans 2 years after treatment (long-term). FDG PET/CT scans from 20 healthy controls were used for comparison. Liver FDG uptake was quantified from the PET/CT scans. Imaging findings as well as clinical, laboratory, and immune markers were compared longitudinally and cross-sectionally to healthy controls.

RESULTS

Liver FDG uptake was lower at baseline and short-term in PWH compared with controls ( P  < 0.0001). At the long-term scan, liver FDG uptake of PWH increased relative to baseline and short-term ( P  = 0.0083 and 0.0052) but remained lower than controls' values ( P  = 0.004). Changes in FDG uptake correlated negatively with levels of glucagon, myeloperoxidase, sCD14, and MCP-1 and positively with markers of recovery (BMI, albumin, and CD4 + cell counts) ( P  < 0.01). In multivariable analyses of PWH values across timepoints, BMI and glucagon were the best set of predictors for liver FDG uptake ( P  < 0.0001).

CONCLUSION

Using FDG PET/CT, we found decreased liver glucose metabolism in PWH that could reflect hepatocytes/lymphocytes/myeloid cell loss and metabolic dysfunction because of inflammation. Although long-term ART seems to reverse many hepatic abnormalities, residual liver injury may still exist within 2 years of treatment initiation, especially in PWH who present with low nadir CD4 + cell counts.

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.

Intrapatient repeatability of background 18F-FDG uptake on PET/CT

Background

Background activity is often used as a reference to assess tumor treatment response on positron emission tomography with 2-deoxy-2-[fluorine-18] fluoro-D-glucose integrated with computed tomography (18F-FDG PET/CT). Our objective was to find the preferred background by assessing the repeatability of its activity. The activity was expressed by a standardized uptake value normalized to lean body mass (SUL).

Methods

Patients who received repeat ¹⁸F-FDG PET/CT scans within 1 to 4 days were selected. The indications included cancer screening, tumor staging, or treatment response evaluation. Background SULs from the aortic blood pool (ABP), liver, and muscle were recorded. Intraclass correlation coefficients (ICCs), the coefficient of variation (CV), and Bland-Altman plots for repeated measures were used to evaluate the degree of repeatability between the two scans. Intrapatient variation in SULs and factors, including the blood glucose level (BGL), tracer uptake period, and dose, were calculated as relative changes between the two scans. A linear regression model was used to analyze all relative changes to identify the correlation between factors and SULs.

Results

Thirty patients were included. The SUL ICCs for the ABP, liver, and muscle were 0.65 (95% CI, 0.38-0.81), 0.47 (95% CI, 0.15-0.70), and 0.82 (95% CI, 0.65-0.91), respectively. The SUL coefficients of variation (CVs) were 9% for the ABP, 12% for the liver, and 10% for muscle. Similar results were obtained from the Bland-Altman plots. There was a positive correlation between the variations in the liver SUL and the BGL (b=0.60, P<0.01). A similar result was found between the variations in muscle SUL and the BGL (b=0.45, P<0.01). The variation in muscle SUL showed a positive correlation with the variation in the tracer uptake period (b=0.58, P<0.01).

Conclusions

The SUL of the liver is more sensitive to BGLs and, therefore, may not be suitable as a referential background. Activities within the ABP and muscle are more stable than those of the liver and should be used as the preferred background for sequential patient evaluation.

The difference between steroid diabetes mellitus and type 2 diabetes mellitus: a whole-body 18F-FDG PET/CT study

AIMS

Steroid diabetes mellitus (SDM) is a metabolic syndrome caused by an increase in glucocorticoids, and its pathogenesis is unclear. ¹⁸F-FDG PET/CT can reflect the glucose metabolism of tissues and organs under living conditions. Here, PET/CT imaging of SDM and type 2 diabetes mellitus (T2DM) rats was used to visualize changes in glucose metabolism in the main glucose metabolizing organs and investigate the pathogenesis of SDM.

METHODS

SDM and T2DM rat models were established. During this time, PET/CT imaging was used to measure the %ID/g value of skeletal muscle and liver to evaluate glucose uptake. The pancreatic, skeletal muscle and liver were analyzed by immunohistochemistry.

RESULTS

SDM rats showed increased fasting blood glucose and insulin levels, hyperplasia of islet α and β cells, increased FDG uptake in skeletal muscle accompanied by an up-regulation of PI3Kp85α, IRS-1, and GLUT4, no significant changes in liver uptake, and that glycogen storage in the liver and skeletal muscle increased. T2DM rats showed atrophy of pancreatic islet β cells and decreased insulin levels, significantly reduced FDG uptake and glycogen storage in skeletal muscle and liver.

CONCLUSIONS

The pathogenesis of SDM is different from that of T2DM. The increased glucose metabolism of skeletal muscle may be related to the increased compensatory secretion of insulin. Glucocorticoids promote the proliferation of islet α cells and cause an increase in gluconeogenesis in the liver, which may cause increased blood glucose.

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.

P2Y12 shRNA normalizes inflammatory dysfunctional hepatic glucokinase activity in type 2 diabetic rats

The celiac ganglion projects its postganglionic (including purinergic) fibers to the liver. P2Y12 receptor is one of the P2Y family members. We found that the expression levels of P2Y12 receptor in both celiac ganglia and liver were increased in type 2 diabetes mellitus (T2DM) rats which also displayed an enhanced activity of celiac sympathetic nerve discharge (SND). In addition, a marked decrease of hepatic glucokinase (GK) expression was accompanied by reduced hepatic glycogen synthesis in T2DM rats, whereas meanwhile the levels of NLRP3, active caspase-1, NF-κB, and interleukin-1β were elevated. All these abnormal alterations could be largely reversed after treatment of short hairpin RNA (shRNA) targeting P2Y12. Our results indicate that the silence of P2Y12 by shRNA may effectively correct the anomalous activity of celiac SND and improve the dysfunctional hepatic glucokinase by counteracting hepatocyte inflammation and likely pyroptosis due to activated NLRP3 inflammasome and caspase-1 signaling, thereby attenuating hyperglycemia in T2DM rats.

Assessing PET Parameters in Oncologic 18F-FDG Studies

PET imaging, particularly oncologic applications of ¹⁸F-FDG, has become a routine diagnostic study. To better describe malignancies, various PET parameters are used. In ¹⁸F-FDG PET studies, SUV_max is the most commonly used parameter to measure the metabolic activity of the tumor. In obese patients, SUV corrected by lean body mass (SUL), and in pediatric patients, SUV corrected by body surface area, are recommended. Metabolic tumor volume is an important parameter to determine the local and total tumor burden. Total lesion glycolysis (SUV_mean × metabolic tumor volume) provides information about averages. Some treatment response assessment protocols recommend using the SUV_peak or SUL_peak of the tumor. Tumor-to-liver ratio and tumor-to-blood-pool ratio are helpful when comparing studies for treatment response assessment. Dual-time-point PET imaging with retention index can help differentiate malignant from benign lesions and may help detect small lesions. Dynamic ¹⁸F-FDG PET imaging and quantitative analysis can measure the metabolic, phosphorylation, and dephosphorylation rates of lesions but are mainly used for research purposes. In this article, we will review the currently available PET parameters in ¹⁸F-FDG studies with their importance, uses, limitations, and reasons for erroneous results.

Assessing the Effect of Various Blood Glucose Levels on 18F-FDG Activity in the Brain, Liver, and Blood Pool

Studies have extensively analyzed the effect of hyperglycemia on ¹⁸F-FDG uptake in normal tissues and tumors. In this study, we measured SUV in the brain, liver, and blood pool in normoglycemia, hyperglycemia, and hypoglycemia to understand the effect of blood glucose on ¹⁸F-FDG uptake and to develop a formula to correct SUV. Methods: Whole-body ¹⁸F-FDG PET/CT images of adults were selected for analysis. Brain SUV_max, blood-pool SUV_mean, and liver SUV_mean were measured at blood glucose ranges of 61-70, 71-80, 81-90, 91-100, 101-110, 111-120, 121-130, 131-140, 141-150, 151-160, 161-170, 171-180, 181-190, 191-200, and 201 mg/dL and above. At each blood glucose range, 10 PET images were analyzed (total, 150). The mean (±SD) SUV of the brain, liver, and blood pool at each blood glucose range was calculated, and blood glucose and SUV curves were generated. Because brain and tumors show a high expression of glucose transporters 1 and 3, we generated an SUV correction formula based on percentage reduction in brain SUV_max with increasing blood glucose level. Results: Mean brain SUV_max gradually decreased with increasing blood glucose level, starting after a level of 110 mg/dL. The approximate percentage reduction in brain SUV_max was 20%, 35%, 50%, 60%, and 65% at blood glucose ranges of 111-120, 121-140, 141-160, 161-200, and 201 mg/dL and above, respectively. In the formula we generated, measured SUV_max is multiplied by a reduction factor of 1.25, 1.5, 2, 2.5, and 2.8 for the blood glucose ranges of 111-120, 121-140, 141-160, 161-200, and 201 mg/dL and above, respectively, to correct SUV. Brain SUV_max did not differ between hypoglycemic and normoglycemic patients (P > 0.05). SUV_mean in the blood pool and liver was lower in hypoglycemic patients (P < 0.05) and did not differ between hyperglycemic (P > 0.05) and normoglycemic patients. Conclusion: Hyperglycemia gradually reduces brain ¹⁸F-FDG uptake, starting after a blood glucose level of 110 mg/dL. Hyperglycemia does not affect ¹⁸F-FDG activity in the liver or blood pool. Hypoglycemia does not seem to affect brain ¹⁸F-FDG uptake but appears to reduce liver and blood-pool activity. The simple formula we generated can be used to correct SUV in hyperglycemic adults in selected cases.

Clinical utility of FDG uptake within reticuloendothelial system on F-18 FDG PET/CT for prediction of tumor recurrence in breast cancer

BACKGROUND

The aim of this study was to investigate the metabolism of the spleen, bone marrow (BM), and liver from preoperative F-18 FDG PET/CT scans for the prediction of recurrence in breast cancer.

METHODS

We retrospectively included 153 patients diagnosed with invasive ductal carcinoma (IDC) of the breast who underwent preoperative F-18 FDG PET/CT scan and a curative operation. The mean standardized uptake value (SUVmean) of the spleen, liver, and BM and maximum SUV (SUVmax) of primary tumors were measured. The relationships between spleen, BM, and liver metabolism and clinicopathologic parameters were evaluated, and possible prognostic parameters predicting recurrence were assessed using disease-free survival (DFS).

RESULTS

Spleen SUVmean was significantly correlated with primary tumor SUVmax, pathologic T (pT) stage, and histologic grade of primary tumor. BM SUVmean also showed a positive correlation with primary tumor SUVmax. Spleen SUVmean were significantly associated with recurrence from binary logistic regression analysis (P = 0.004). Spleen, BM, liver, and primary tumor SUVs were all significant prognostic factors for DFS in univariate Cox regression analysis (all P<0.024). Among all PET parameters analyzed, spleen SUVmean ≥ 2.21 (P = 0.032) was in the multivariable analysis the powerful poor prognostic factor predicting DFS that was independent of other clinicopathological features like T stage (pT >2; P = 0.009) and estrogen receptor (ER) status (ER negativity; P = 0.001).

CONCLUSION

Splenic metabolism together with pT stage and ER status was an independent prognostic factor for predicting recurrence in breast cancer. Metabolic activity of reticuloendothelial system such as spleen, liver or BM on preoperative F-18 FDG PET/CT can be a meritorious imaging factor for discriminating patients with IDC that require adjunctive therapy to prevent recurrence.

Variations of the liver standardized uptake value in relation to background blood metabolism: An 2-[18F]Fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography study in a large population from China

To investigate the influence of background blood metabolism on liver uptake of 2-[F]fluoro-2-deoxy-D-glucose (F-FDG) and search for an appropriate corrective method.Positron emission tomography/computed tomography (PET/CT) and common serological biochemical tests of 633 healthy people were collected retrospectively. The mean standardized uptake value (SUV) of the liver, liver artery, and portal vein (i.e., SUVL, SUVA, and SUVP) were measured. SUVL/A was calculated as SUVL/SUVA, while SUVL/P was calculated as SUVL/SUVP. SUV of liver parenchyma (SUVLP) was calculated as SUVL - .3 × (.75 × SUVP + .25 × SUVA). The coefficients of variation (CV) of SUVL, SUVL/A, SUVL/P, and SUVLP were compared to assess their interindividual variations. Univariate and multivariate analyses were performed to identify vulnerabilities of these SUV indexes to common factors assessed using serological liver functional tests.SUVLP was significantly larger than SUVL (2.19 ± .497 vs 1.88 ± .495, P < .001), while SUVL/P was significantly smaller than SUVL (1.72 ± .454 vs 1.88 ± .495, P < .001). The difference between SUVL/A and SUVL was not significant (1.83 ± .500 vs 1.88 ± .495, P = .130). The CV of SUVLP (22.7%) was significantly smaller than that of SUVL (22.7%:26.3%, P < .001), while the CVs of SUVL/A (27.2%) and SUVL/P (26.4%) were not different from that of SUVL (P = .429 and .929, respectively). Fewer variables independently influenced SUVLP than influenced SUVL, SUVL/A, and SUVL/P; Only aspartate aminotransferase, body mass index, and total cholesterol, all P-values <.05.The activity of background blood influences the variation of liver SUV. SUVLP might be an alternative corrective method to reduce this influence, as its interindividual variation and vulnerability to effects from common factors of serological liver functional tests are relatively lower than the commonly used SUVL.

Effects of Tumor Burden on Reference Tissue Standardized Uptake for PET Imaging: Modification of PERCIST Criteria

Purpose To examine the effect metabolic burden (tumor and/or cardiac myocyte uptake) has on fluorine 18 fluorodeoxyglucose (FDG) distribution in organs and tissues of interest. Materials and Methods Positron emission tomographic (PET)/computed tomographic (CT) scans at the Ann Arbor Veterans Affairs hospital from January to July 2015 were reviewed. A total of 107 scans (50 patients; mean age, 64.3 years ± 13.2 [standard deviation]) had metabolic tissue burden assessed by using total lesion glycolysis (TLG) obtained from autosegmentation of the tumor and/or cardiac tissue. Standardized uptake value (SUV) and subsequent normalized SUV uptake in target organs and tissues were compared with 436 FDG PET/CT scans previously reported in 229 patients as a function of TLG to describe the effect(s) that metabolic burden has on reference tissue (blood pool, liver, and brain) FDG uptake. Subsequent regression by using linear mixed-effects models was used. If the slope of the regression was significantly (P < .05) different than zero, then an effect from TLG was present. Results There was a negative inverse relationship (P < .0001) between FDG uptake within reference tissues (blood pool, liver, and brain) and TLG in comparison to the study population at similar blood glucose levels. This TLG effect was no longer statistically significant (P > .05) when FDG uptake was normalized to a reference tissue (eg, blood pool or liver). Conclusion Metabolic tissue burden can have a significant effect on SUV measurements for PET imaging. This effect can be mitigated by normalizing FDG uptake to a reference tissue. ^© RSNA, 2018.

Effects of blood glucose level on 18F-FDG uptake for PET/CT in normal organs: A systematic review

Purpose

To perform a systematic review of the effect of blood glucose levels on 2-Deoxy-2-[18F]fluoro-D-glucose (18F-FDG) uptake in normal organs.

Methods

We searched the MEDLINE, EMBASE and Cochrane databases through 22 April 2017 to identify all relevant studies using the keywords “PET/CT” (positron emission tomography/computed tomography), “standardized uptake value” (SUV), “glycemia,” and “normal.” Analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. Maximum and mean SUVs and glycemia were the main parameters analyzed. To objectively measure the magnitude of the association between glycemia and 18F-FDG uptake in different organs, we calculated the effect size (ES) and the coefficient of determination (R²) whenever possible.

Results

The literature search yielded 225 results, and 14 articles met the inclusion criteria; studies included a total of 2714 (range, 51–557) participants. The brain SUV was related significantly and inversely to glycemia (ES = 1.26; R² 0.16–0.58). Although the liver and mediastinal blood pool were significantly affected by glycemia, the magnitudes of these associations were small (ES = 0.24–0.59, R² = 0.01–0.08) and negligible (R² = 0.02), respectively. Lung, bone marrow, tumor, spleen, fat, bowel, and stomach 18F-FDG uptakes were not influenced by glycemia. Individual factors other than glycemia can also affect 18F-FDG uptake in different organs, and body mass index appears to be the most important of these factors.

Conclusion

The impact of glycemia on SUVs in most organs is either negligible or too small to be clinically significant. The brain SUV was the only value largely affected by glycemia.

Effects of blood glucose level on 18F fluorodeoxyglucose (18F-FDG) uptake for PET/CT in normal organs: an analysis on 5623 patients

Our purpose was to evaluate the effect of glycemia on ¹⁸F-FDG uptake in normal organs of interest. The influences of other confounding factors, such as body mass index (BMI), diabetes, age, and sex, on the relationships between glycemia and organ-specific standardized uptake values (SUVs) were also investigated. We retrospectively identified 5623 consecutive patients who had undergone clinical PET/CT for oncological indications. Patients were stratified into groups based on glucose levels, measured immediately before ¹⁸F-FDG injection. Differences in mean SUVmax values among glycemic ranges were clinically significant only when >10% variation was observed. The brain was the only organ that presented a significant inverse relationship between SUVmax and glycemia (p < 0.001), even after controlling for diabetic status. No such difference was observed for the liver or lung. After adjustment for sex, age, and BMI, the association of glycemia with SUVmax was significant for the brain and liver, but not for the lung. In conclusion, the brain was the only organ analyzed showing a clinically significant relationship to glycemia after adjustment for potentially confounding variables. The lung was least affected by the variables in our model, and may serve as an alternative background tissue to the liver.

FDG-PET reproducibility in tumor-bearing mice: comparing a traditional SUV approach with a tumor-to-brain tissue ratio approach

BACKGROUND

Current [F-18]-fluorodeoxyglucose positron emission tomography (FDG-PET) procedures in tumor-bearing mice typically includes fasting, anesthesia, and standardized uptake value (SUV)-based quantification. Such procedures may be inappropriate for prolonged multiscan experiments. We hypothesize that normalization of tumor FDG retention relative to a suitable reference tissue may improve accuracy as this method may be less susceptible to uncontrollable day-to-day changes in blood glucose levels, physical activity, or unnoticed imperfect tail vein injections.

MATERIAL AND METHODS

Fed non-anesthetized tumor-bearing mice were administered FDG intravenously (i.v.) or intraperitoneally (i.p.) and PET scanned on consecutive days using a Mediso nanoScan PET/magnetic resonance imaging (MRI). Reproducibility of various PET-deduced measures of tumor FDG retention, including normalization to FDG signal in reference organs and a conventional SUV approach, was evaluated.

RESULTS

Day-to-day variability in i.v. injected mice was lower when tumor FDG retention was normalized to brain signal (T/B), compared to normalization to other tissues or when using SUV-based normalization. Assessment of tissue radioactivity in dissected tissues confirmed the validity of PET-derived T/B ratios. Mean T/B and SUV values were similar in i.v. and i.p. administered animals, but SUV normalization was more robust in the i.p. group than in the i.v. group.

CONCLUSIONS

Multimodality scanners allow tissue delineation and normalization of tumor FDG uptake relative to reference tissues. Normalization to brain, but not liver or kidney, improved scan reproducibility considerably and was superior to traditional SUV quantification in i.v. tracer-injected animals. Day-to-day variability in SUV's was lower in i.p. than in i.v. injected animals, and i.p. injections may therefore be a valuable alternative in prolonged rodent studies, where repeated vein injections are undesirable.

Effect of hyperglycemia on brain and liver 18F-FDG standardized uptake value (FDG SUV) measured by quantitative positron emission tomography (PET) imaging

PURPOSE

Blood glucose is routinely measured prior to ¹⁸F-fluorodeoxyglucose (FDG) administration in positron emission tomography (PET) imaging to identify hyperglycemia that may affect image quality. In this study we explore the effects of blood glucose levels upon semi-quantitative standardized uptake value (SUV) measurements of target organs and tissues of interest and in particular address the relationship of blood glucose to FDG accumulation in the brain and liver.

METHODS

436 FDG PET/CT consecutive studies performed for oncology staging in 229 patients (226 male) at the Ann Arbor Veterans Administration Healthcare System were reviewed. All patients had blood glucose measured (112.4±34.1mg/dL) prior to injection of 466.2±51.8MBq (12.6±1.4mCi) of FDG. SUV measurements of brain, aortic arch blood-pool, liver, and spleen were obtained at 64.5±10.2min' post-injection.

RESULTS

We found a negative inverse relationship of brain SUV with increasing plasma glucose, levels for both absolute and normalized (either to blood-pool or liver) values. Higher blood glucose levels had a mild effect upon liver and blood-pool SUV. By contrast, spleen SUV was independent of blood glucose, but demonstrated the greatest variability (deviation on linear regression). In contrast to other tissues, liver and spleen SUV normalized to blood-pool SUV were not dependent upon blood glucose levels.

CONCLUSION

The effects of hyperglycemia upon FDG uptake in brain and liver, over a range of blood glucose values generally considered acceptable for clinical PET imaging, may have measurable effects on semi-quantitative image analysis.

Concurrent Low Brain and High Liver Uptake on FDG PET Are Associated with Cardiovascular Risk Factors

Objective

Concurrent low brain and high liver uptake are sometimes observed on fluorine-18-labeled fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET). We investigated the potential clinical significance of this uptake pattern related to metabolic syndrome (MS).

Materials and Methods

We retrospectively reviewed data from 264 consecutive males who had undergone general health check-ups, including FDG PET/CT scans. After an overnight fast, the men had their peripheral blood drawn and the levels of various laboratory parameters measured; an FDG PET/CT scan was performed on the same day. We measured the maximum standardized uptake values of the brain and liver from regions of interest manually placed over the frontal cortex at the level of the centrum semiovale and the right lobe of the liver parenchyma, respectively.

Results

Fasting blood glucose (FBG; odds ratio [OR] = 1.063, p < 0.001) and glycated hemoglobin (HbA1c; OR = 3.634, p = 0.010) were the strongest predictive factors for low brain FDG uptake, whereas waist circumference (OR = 1.200, p < 0.001) and γ-glutamyl transpeptidase (OR = 1.012, p = 0.001) were the strongest predictive factors for high liver uptake. Eleven subjects (4.2%) showed concurrent low brain and high liver FDG uptake, and all but one of these subjects (90.9%) had MS. Systolic blood pressure, waist circumference, FBG, triglyceride, alanine aminotransferase, insulin resistance (measured by homeostasis model assessment), insulin, HbA1c, and body mass index were higher in subjects with this FDG uptake pattern than in those without (all, p < 0.001).

Conclusion

Concurrent low brain and high liver FDG uptake were closely associated with MS. Moreover, subjects with this pattern had higher values for various cardiovascular risk factors than did those without.

The predictive ability of liver function indexes on 18F-FDG uptake in the liver

AIM

The liver is an important reference organ for positron emission tomography/ computed tomography (PET-CT) examination using 18F-fluorodeoxyglucose (18F-FDG). However, 18F-FDG uptake by the liver is affected by many factors. We therefore investigated the effect of hepatic function on 18F-FDG uptake in the liver.

METHODS

A retrospective analysis of data on the hepatic function and the mean liver standardized up-take value (SUV) of 18F-FDG uptake in the liver during PET-CT examination of 500 (381 males, 119 females, aged 27-71) physical examinees.

RESULTS

The mean liver SUV was 1.88 ± 0.20. The correlation coefficient and partial correlation coefficient for age, the levels of conjugated bilirubin, globulin, AST and the mean liver SUV were statistically significant (r' = 0.119, -0.197, -0.089 and 0.151, all p < 0.05). Multiple linear regression analysis showed that age and the levels of conjugated bilirubin, globulin and aspartate amino-transferase (AST) were independent factors that influenced changes in the mean liver SUV (β = 0.008, -0.025, -0.151 and 0.005, all p < 0.05). The globulin level had the biggest predictive ability (β' = -0.151, p < 0.05).

CONCLUSIONS

The uptake of 18F-FDG in the liver was influenced by some liver function indexes. The levels of conjugated bilirubin, globulin and AST were independent factors for predicting changes in the uptake of 18F-FDG in the liver. Liver function test results should be combined with an evaluation of the metabolic activity of the liver.

Factors that affect PERCIST-defined test-retest comparability: an exploration of feasibility in routine clinical practice

PURPOSE

The aim of this study was to evaluate the factors affecting the comparability of F-FDG PET/CT scans using the PERSIST criteria for treatment response evaluation in a clinical PET/CT unit.

PATIENTS AND METHODS

Patients diagnosed with esophageal cancer were assessed for treatment response by comparing 2 F-FDG PET/CT scans, at baseline (PET 1) and 1 month after the end of induction chemoradiation (PET 2). According to the PERCIST recommendations, patients with mean SUV normalized by the lean body mass within reference volume of interest that changed less than 0.3 unit and less than 20% were deemed as comparable. Absolute differences of body weight, blood glucose level, activity of F-FDG, and uptake time between the 2 scans were computed. Binary logistic regression was used to identify the predictive factors, and receiver operating characteristic curves were used for thresholds. P < 0.05 was considered statistically significant.

RESULTS

Sixty-nine subjects were identified. The mean (SD) values at PET 0 and PET 2 were 5.9 (1.04) mmol/L and 6.2 (1.06) mmol/L (P = 0.013), 54.6 (10.0 kg) and 53.3 (10.3 kg) (P = 0.013), 7.7 (1.3 mCi) and 7.6 (1.5 mCi) (P = 0.349), as well as 74.2 (12.4) minutes and 73.0 (12.3) minutes (P = 0.539), for blood glucose level, body weight, injected activity, and uptake time, respectively. Seventeen (24.6%) failed to match the PERCIST-defined comparability criteria. Case-based discrepancies (mean [SD]) were 0.76 (0.62) mmol/L, 3.4 (2.9) kg, 0.8 (0.7) mCi, and 11.7 (9.8) minutes for blood glucose, body weight, injected activity, and uptake time, respectively, of which only uptake time significantly affected comparability (P = 0.046; odds ratio, 1.06; 95% confidence interval, 1.00-1.12), with a limit of 2.2-minute discrepancy identified as the requirement for 100% comparability.

CONCLUSIONS

Uptake time had the strongest effect on PERCIST-defined comparability. Therefore, for response assessment scans, reference to initial scans for determination of optimal uptake time is recommended.

Effects of varying serum glucose levels on 18F-FDG biodistribution

OBJECTIVE

Hyperglycemia has been shown to influence fluorine-18 fluorodeoxyglucose ((18)F-FDG) uptake in tumor cells. Therefore, patients are instructed to fast for 6 h, while maintaining serum glucose levels at an acceptable range. The study was performed to evaluate the effect of fasting blood glucose levels on the biodistribution of (18)F-FDG in various tissues including the liver, heart, bone marrow, skeletal muscle, and tumors.

MATERIALS AND METHODS

Fingerstick fasting blood glucose is routinely measured on the morning of the procedure. The maximum standardized uptake value (SUV(max)) in the right and left hepatic lobes, left ventricle, sacrum, thigh, and tumor was measured in 229 consecutive patients undergoing (18)F-FDG PET/computed tomography for tumor. Patients were divided into three groups depending on their serum glucose levels: low (<100; n = 53), medium (100-160; n = 149), and high (160-201; n = 27). A retrospective analysis of the relationship between glucose levels and standardized uptake value was performed.

RESULTS

There was a statistically significant increase in the average SUV(max) in the right and left hepatic lobes as glucose levels increased (right lobe P=0.00144; left lobe P = 0.03889). Subsequently, pairwise analysis was performed, revealing a statistically significant increase in SUV(max) in the right hepatic lobe between low-glucose and medium-glucose groups and in both hepatic lobes between low and high groups (P < 0.017). No significant difference was observed in any of the other measured tissues.

CONCLUSION

This study shows a directly proportional relationship between blood glucose levels and nonpathologic (18)F-FDG biodistribution in the right and left hepatic lobes. The influence of blood glucose on expected biodistribution patterns, particularly in the liver, should be considered during interpretation.

Variability of Hepatic 18F-FDG Uptake at Interim PET in Patients With Hodgkin Lymphoma

INTRODUCTION

When evaluating response of Hodgkin lymphoma (HL) to chemotherapy on interim (18)F-FDG-PET/CT, physiological liver uptake is used as reference. Hodgkin lymphoma sites with uptake greater than liver are interpreted as positive. We aimed at examining factors that might influence liver uptake as reference organ.

METHODS

Fifty patients with HL who received baseline (18)F-FDG-PET/CT (PET1) and interim PET (PET2), usually after 2 cycles of adriamycin bleomycin, vinblastine, and dacarbazine chemotherapy, were included retrospectively. SUVmean normalized for body weight (SUVmean) and for lean body mass (SULmean) were obtained from regions of interest in the right lobe of the liver.

RESULTS

On univariate analysis, liver SUVmean on interim PET increased with increasing body mass index (BMI) (P = 0.0453) and were higher in women (P = 0.0401). These factors remained significant on multivariate analysis (P = 0.009 and P = 0.008, respectively). No significant correlation was found with postinjection delay, blood glucose level, and age. Liver SULmean were not affected by the studied variables. Average liver SUVmean in the 50 patients were similar at baseline and interim PET. In 11 patients (22%), however, there was 30% or greater variation in liver SUVmean between PET1 and PET2. No factors explaining intrapatient variation in hepatic uptake between PET1 and PET2 were found on correlation analysis.

CONCLUSION

At interim PET in patients with HL, liver SUVmean depends on BMI and sex, but not liver SULmean. Furthermore, our study, conducted with standard clinical procedure, also confirmed the high range of liver uptake values from one patient to another. Caution is required when using liver SUV as reference in patients with high BMI. Intrapatient fluctuation in liver SUVmean should also be expected.

Impacts of biological and procedural factors on semiquantification uptake value of liver in fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography imaging

BACKGROUND

Increased metabolic activity of fluorodeoxyglucose (FDG) in tissue is not only resulting of pathological uptake, but due to physiological uptake as well. This study aimed to determine the impacts of biological and procedural factors on FDG uptake of liver in whole body positron emission tomography/computed tomography (PET/CT) imaging.

METHODS

Whole body fluorine-18 ((18)F) FDG PET/CT scans of 51 oncology patients have been reviewed. Maximum standardized uptake value (SUVmax) of lesion-free liver was quantified in each patient. Pearson correlation was performed to determine the association between the factors of age, body mass index (BMI), blood glucose level, FDG dose and incubation period and liver SUVmax. Multivariate regression analysis was established to determine the significant factors that best predicted the liver SUVmax. Then the subjects were dichotomised into four BMI groups. Analysis of variance (ANOVA) was established for mean difference of SUVmax of liver between those BMI groups.

RESULTS

BMI and incubation period were significantly associated with liver SUVmax. These factors were accounted for 29.6% of the liver SUVmax variance. Statistically significant differences were observed in the mean SUVmax of liver among those BMI groups (P<0.05).

CONCLUSIONS

BMI and incubation period are significant factors affecting physiological FDG uptake of liver. It would be recommended to employ different cut-off value for physiological liver SUVmax as a reference standard for different BMI of patients in PET/CT interpretation and use a standard protocol for incubation period of patient to reduce variation in physiological FDG uptake of liver in PET/CT study.

Visceral adiposity is associated with altered myocardial glucose uptake measured by (18)FDG-PET in 346 subjects with normal glucose tolerance, prediabetes, and type 2 diabetes

Background

The heart requires constant sources of energy mostly from free fatty acids (FFA) and glucose. The alteration in myocardial substrate metabolism occurs in the heart of diabetic patients, but its specific association with other metabolic variables remains unclear. We aimed to evaluate glucose uptake in hearts of subjects with normal glucose tolerance (NGT), prediabetes, and type 2 diabetes mellitus (T2DM) using [¹⁸F]-fluorodeoxyglucose-positron emission tomography (¹⁸FDG-PET) in association with visceral and subcutaneous adiposity, and metabolic laboratory parameters.

Methods

A total of 346 individuals (NGT, n = 76; prediabetes, n = 208; T2DM, n = 62) in a health promotion center of a tertiary hospital were enrolled. The fasting myocardial glucose uptake, and visceral and subcutaneous fat areas were evaluated using ¹⁸FDG-PET and abdominal computed tomography, respectively.

Results

Myocardial glucose uptake was significantly decreased in subjects with T2DM compared to the NGT or prediabetes groups (p for trend = 0.001). Multivariate linear regression analyses revealed that visceral fat area (β = −0.22, p = 0.018), fasting FFA (β = −0.39, p < 0.001), and uric acid levels (β = −0.21, p = 0.007) were independent determinants of myocardial glucose uptake. Multiple logistic analyses demonstrated that decreased myocardial glucose uptake (OR 2.32; 95 % CI 1.02–5.29, p = 0.045) and visceral fat area (OR 1.02, 95 % CI 1.01–1.03, p = 0.018) were associated with T2DM.

Conclusions

Our findings indicate visceral adiposity is strongly associated with the alteration of myocardial glucose uptake evaluated by ¹⁸FDG-PET, and its association further relates to T2DM.

Liver metabolic activity changes over time with neoadjuvant therapy in locally advanced rectal cancer

OBJECTIVE

The aim of this study was to evaluate, using PET/computed tomography (CT), changes in liver metabolic activity in patients with locally advanced rectal cancer (LARC) after neoadjuvant chemoradiotherapy (CRT).

PATIENTS AND METHODS

A total of 29 biopsy-proven LARC patients between 2009 and 2012 were studied. Liver standardized uptake values (SUVs) and SUVs adjusted for lean body mass (SULs) were obtained from PET/CT images obtained at 1 h (early) and 2 h (late) after (18)F-fluorodeoxyglucose ((18)F-FDG) administration both before and after neoadjuvant CRT. Age, sex, BMI, lean body mass, blood glucose level, and (18)F-FDG dose, which can influence liver SUVs and SULs, were also analyzed.

RESULTS

Fourteen (48%) men and 15 (52%) women with a mean age of 62±11 years (range 34-80 years) were included in the study. The mean SUVs and SULs were significantly decreased in the late scans. Sex was significantly correlated with the mean liver SUV in early and late scans. The mean SUV differed significantly between male and female patients in early and late images (P<0.05). In a multivariate stepwise regression analysis, only liver SUVs (maximum and mean) were significantly associated with BMI before and after therapy. SUVs were significantly higher in the high (≥25) BMI group after but not before therapy. Mean SUL was not influenced by BMI.

CONCLUSION

Liver (18)F-FDG uptake is consistent before and after neoadjuvant CRT therapy in patients with LARC. When assessing response to therapy and using liver metabolic activity to indicate background activity, BMI should be considered as it can influence liver metabolic activity.

Imaging malignant melanoma with (18)F-5-FPN

PURPOSE

Radiolabelled benzamides are attractive candidates for targeting melanoma because they bind to melanin and exhibit high tumour uptake and retention. (18)F-5-Fluoro-N-(2-[diethylamino]ethyl)picolinamide ((18)F-5-FPN), a benzamide analogue, was prepared and its pharmacokinetics and binding affinity evaluated both in vitro and in vivo to assess its clinical potential in the diagnosis and staging of melanoma.

METHODS

(18)F-5-FPN was prepared and purified. Its binding specificity was measured in vitro in two different melanoma cell lines, one pigmented (B16F10 cells) and one nonpigmented (A375m cells), and in vivo in mice xenografted with the same cell lines. Dynamic and static PET images using (18)F-5-FPN were obtained in the tumour-bearing mice, and the static images were also compared with those acquired with (18)F-FDG. PET imaging with (18)F-5-FPN was also performed in B16F10 tumour-bearing mice with lung metastases.

RESULTS

(18)F-5-FPN was successfully prepared with radiochemical yields of 5 - 10 %. Binding of (18)F-5-FPN to B16F10 cells was much higher than to A375m cells. On dynamic PET imaging B16F10 tumours were visible about 1 min after injection of the tracer, and the uptake gradually increased over time. (18)F-5-FPN was rapidly excreted via the kidneys. B16F10 tumours were clearly visible on static images acquired 1 and 2 h after injection, with high uptake values of 24.34 ± 6.32 %ID/g and 16.63 ± 5.41 %ID/g, respectively, in the biodistribution study (five mice). However, there was no visible uptake by A375m tumours. (18)F-5-FPN and (18)F-FDG PET imaging were compared in B16F10 tumour xenografts, and the tumour-to-background ratio of (18)F-5-FPN was ten times higher than that of (18)F-FDG (35.22 ± 7.02 vs. 3.29 ± 0.53, five mice). (18)F-5-FPN PET imaging also detected simulated lung metastases measuring 1 - 2 mm.

CONCLUSION

(18)F-5-FPN specifically targeted melanin in vitro and in vivo with high retention and affinity and favourable pharmacokinetics. (18)F-5-FPN may be an ideal molecular probe for melanoma diagnosis and staging.

Comparison of myocardial F-18 FDG uptake between overnight and non-overnight fasting in non-diabetic healthy subjects

PURPOSE

To evaluate whether an overnight or non-overnight fast for suppressing physiological FDG uptake by the myocardium is better in non-diabetic healthy subjects before F-18 FDG PET/CT studies.

MATERIALS AND METHODS

One hundred two subjects who underwent whole-body F-18 FDG PET/CT for routine health checkups were retrospectively reviewed. For quantitative assessment, a region of interest was drawn around the entire left ventricle visible in the axial view containing the highest visual uptake in order to measure the maximum standardized uptake value (SUV max). FDG uptake in the myocardium was visually graded as follows: grade 0 = minimal, 1 = mostly minimal or mild, 2 = mostly intense or moderate, and 3 = homogeneously intense. Adequate suppression of myocardial uptake was quantitatively defined as a SUV max ≤ 5.0 and grade 0 by visual assessment.

RESULTS

With regard to the SUV max, myocardial uptake was not different between the overnight and the non-overnight fasting subjects (P = 0.753). In subjects who had adequate suppression of myocardial uptake, no significant difference was observed between the overnight and non-overnight fasting subjects either in terms of visual or quantitative assessment (P = 0.539 and P = 0.678, respectively).

CONCLUSION

Both overnight and non-overnight fasts are not adequate for suppressing the physiological uptake of FDG by the myocardium.

Quantification of tumour (18) F-FDG uptake: Normalise to blood glucose or scale to liver uptake?

PURPOSE

To compare normalisation to blood glucose (BG) with scaling to hepatic uptake for quantification of tumour (18) F-FDG uptake using the brain as a surrogate for tumours.

METHODS

Standardised uptake value (SUV) was measured over the liver, cerebellum, basal ganglia, and frontal cortex in 304 patients undergoing (18) F-FDG PET/CT. The relationship between brain FDG clearance and SUV was theoretically defined.

RESULTS

Brain SUV decreased exponentially with BG, with similar constants between cerebellum, basal ganglia, and frontal cortex (0.099-0.119 mmol/l(-1)) and similar to values for tumours estimated from the literature. Liver SUV, however, correlated positively with BG. Brain-to-liver SUV ratio therefore showed an inverse correlation with BG, well-fitted with a hyperbolic function (R = 0.83), as theoretically predicted. Brain SUV normalised to BG (nSUV) displayed a nonlinear correlation with BG (R = 0.55); however, as theoretically predicted, brain nSUV/liver SUV showed almost no correlation with BG. Correction of brain SUV using BG raised to an exponential power of 0.099 mmol/l(-1) also eliminated the correlation between brain SUV and BG.

CONCLUSION

Brain SUV continues to correlate with BG after normalisation to BG. Likewise, liver SUV is unsuitable as a reference for tumour FDG uptake. Brain SUV divided by liver SUV, however, shows minimal dependence on BG.

KEY POINTS

• FDG standard uptake value in tumours helps clinicians assess response to treatment. • SUV is influenced by blood glucose; normalisation to blood glucose is recommended. • An alternative approach is to scale tumour SUV to liver SUV. • The brain used as a tumour surrogate shows that neither approach is valid. • Applying both approaches, however, appropriately corrects for blood glucose.

The combined effects of serum lipids, BMI, and fatty liver on 18F-FDG uptake in the liver in a large population from China: an 18F-FDG-PET/CT study

OBJECTIVES

The aim of the study was to investigate the combined effects of serum lipids, BMI, and fatty liver on the liver uptake of fluorine-18 fluorodeoxyglucose ((18)F-FDG).

METHODS

A total of 676 individuals were retrospectively studied. The mean standardized uptake value (SUV) was used to quantify liver (18)F-FDG uptake. Univariate analyses and multivariate regression models identified variables that predicted the mean liver SUV before and after dichotomizing participants into low and high BMI groups.

RESULTS

The mean liver SUV (1.831 ± 0.417) differed significantly among nutritional categories (P = 0.005) and degrees of fatty liver (P < 0.001). An increase in mean liver SUV was noted in individuals with mild and moderate fatty liver compared with normal individuals and in overweight individuals compared with underweight individuals, whereas a downward trend was identified in both individuals with severe fatty liver and those who were obese. BMI had the strongest association with severity of fatty liver (r = 0.443, P < 0.001). Triglyceride, HDL, apolipoprotein-A, age, and BMI were independent variables predicting liver SUV mean in the whole population, whereas fatty liver severity presented as an independent variable only in the low BMI population (P = 0.031).

CONCLUSION

BMI, age, triglyceride, HDL, and apolipoprotein-A were independent variables predicting liver (18)F-FDG uptake. Mild and moderate degree of fatty liver had a positive effect on liver (18)F-FDG uptake, whereas a severe degree of fatty liver negatively affected (18)F-FDG uptake. Attention should be paid to liver metabolism in patients with fatty liver before using liver as the comparator in determining focal (18)F-FDG uptake elsewhere within the abdomen.

Effect of R-CHOP chemotherapy on liver and mediastinal blood pool (18)F-FDG standardized uptake values in patients with non-Hodgkin's lymphoma

AIM

We aimed to investigate the impact of chemotherapy on (18)F-FDG uptake in the liver and mediastinal blood pool (MBP) among patients with non-Hodgkin's lymphoma.

METHODS

Twenty-three patients with NHL underwent baseline, interim, and postchemotherapy (18)F-FDG PET/CT. SUVmax and SUVmean values of the liver and MBP at imaging time were compared statistically.

RESULTS

We did not find any significant differences between the liver and mediastinum SUVmean and SUVmax values (P>.05).

CONCLUSIONS

Our study demonstrates that the (18)F-FDG uptake in the liver and MBP are not significantly affected by R-CHOP chemotherapy in patients with NHL.

Predictive significance of standardized uptake value parameters of FDG-PET in patients with non-small cell lung carcinoma

¹⁸F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is widely used to diagnose and stage non-small cell lung cancer (NSCLC). The aim of this retrospective study was to evaluate the predictive ability of different FDG standardized uptake values (SUVs) in 74 patients with newly diagnosed NSCLC. ¹⁸F-FDG PET/CT scans were performed and different SUV parameters (SUV_max, SUV_avg, SUV_T/L, and SUV_T/A) obtained, and their relationship with clinical characteristics were investigated. Meanwhile, correlation and multiple stepwise regression analyses were performed to determine the primary predictor of SUVs for NSCLC. Age, gender, and tumor size significantly affected SUV parameters. The mean SUVs of squamous cell carcinoma were higher than those of adenocarcinoma. Poorly differentiated tumors exhibited higher SUVs than well-differentiated ones. Further analyses based on the pathologic type revealed that the SUV_max, SUV_avg, and SUV_T/L of poorly differentiated adenocarcinoma tumors were higher than those of moderately or well-differentiated tumors. Among these four SUV parameters, SUV_T/L was the primary predictor for tumor differentiation. However, in adenocarcinoma, SUV_max was the determining factor for tumor differentiation. Our results showed that these four SUV parameters had predictive significance related to NSCLC tumor differentiation; SUV_T/L appeared to be most useful overall, but SUV_max was the best index for adenocarcinoma tumor differentiation.

Liver standardized uptake value corrected for lean body mass at FDG PET/CT: effect of FDG uptake time

OBJECTIVE

The objective of this study is to establish the magnitude change and interreader reliability of the liver standardized uptake value corrected for lean body mass (SULmean) in dual-time-point imaging at 1 and 2 hours and 1 and 4 hours.

PATIENTS AND METHODS

Early and delayed FDG PET/CT scans were included for 28 patients (13 men and 15 women) who had normal liver by CT or ultrasound. The average uptake time between the early and delayed scans were 55 minutes (range, 44-69 minutes) for pancreatic adenocarcinoma patients (n = 19) and 184 minutes (range, 140-197 minutes) for neurofibromatosis patients (n = 9). A 30-mm-diameter spherical volume of interest was placed within the right lobe of the liver above, below, and at the level of the main portal vein by 2 independent readers. Correlation coefficients, analysis of variance, intraclass correlation coefficient, and Bland-Altman analysis were performed.

RESULTS

The mean liver SULmean was between 1.39 and 1.42 and between 1.28 and 1.3 in early and delayed images, respectively (P = 0.001). There is time-dependent reduction in the mean liver SULmean at 2-hour (7%-8%) and 4-hour uptake time (15%-21%) compared with 1-hour uptake time. The correlation coefficient between delayed uptake time and liver SULmean reduction is 0.39 to 0.41 at the upper aspect of the liver. The intraclass correlation coefficient for 2 readers varied between 0.997 and 0.998 and between 0.995 and 0.999 in early and delayed images, respectively (P = 0.001).

CONCLUSIONS

There is time-dependent reduction of mean liver SULmean, about 7% to 8% within the clinically relevant FDG uptake time, in the same patient with excellent interreader agreement in early and delayed images within the right lobe of the liver. Therefore, liver SULmean could represent a useful reference parameter in quantitative analysis of dual-phase FDG PET/CT in malignancy or atypical infection/inflammatory disease. Furthermore, it may be suitable as a normalization factor in currently available formulae quantifying therapy response on PET imaging.

Implications of Ambient Glucose Variation on the Target-to-Background Ratio of Hepatic Tumors By (18)FDG-PET Imaging

Objectives:

To investigate the effects of ambient glucose on quantitative analysis of hepatic tumors on 2-deoxy-2-(¹⁸F)-fluoro-D-glucose (¹⁸FDG) positron emission tomography (PET) and to establish a method for glucose correction.

Patients and Methods:

Eighty-six patients with hepatic lesions identified on ¹⁸FDG PET/computed tomography (CT) were analyzed. The serum glucose level (Glc) was recorded prior to imaging, and the maximum standardized uptake value (SUV) in the hepatic tumors and the average SUV in normal liver were determined. The inverse relationship of SUV to glucose can be defined as d (SUV)/d (Glc) = g*SUV/(Glc), where g is the glucose sensitivity. Simulations using glucose level from 70 to 250 mg/dl were performed to evaluate the effects of Glc on the maximum SUV of malignant hepatic lesions and normal liver.

Results:

By logarithmic transformation and linear regression, g for metastasis was significantly higher than that for normal liver (−0.636 ± 0.144 vs. −0.0536 ± 0.0583; P = 0.00092). Simulation studies showed that the SUV in malignant lesions will decrease rapidly when Glc level is >120 mg/dl, while background liver remains relatively constant up to 250 mg/dl.

Conclusion:

The tumor FDG uptake is much more sensitive to ambient glucose level variation than the background liver. Therefore, correction by the glucose sensitivity factor will result in more accurate SUV measurements and make semi-quantitative analysis of ¹⁸FDG PET scans more reliable.

Nuclear imaging for functional evaluation and theragnosis in liver malignancy and transplantation

Currently, nuclear imaging such as positron emission tomography (PET) and single photon emission computed tomography (SPECT) is increasingly used in the management of liver malignancy. ¹⁸F-fluorodeoxyglucose (FDG)-PET is the most widely used nuclear imaging in liver malignancy as in other cancers, and has been reported to be effective in diagnosis, response monitoring, recurrence evaluation, and prognosis prediction. Other PET imaging such as ¹¹C-acetate PET is also used complementarily to FDG-PET in diagnosis of liver malignancy. Additionally, image-based evaluation of regional hepatic function can be performed using nuclear imaging. Those imaging modalities are also effective for candidate selection, treatment planning, and perioperative evaluation in liver surgery and transplantation. Recently, nuclear imaging has been actively adopted in the transarterial radioembolization therapy of liver malignancy, according to the concept of theragnosis. With the development of new hybrid imaging technologies such as PET/magnetic resonance imaging and SPECT/CT, nuclear imaging is expected to be more useful in the management of liver malignancy, particularly regarding liver surgery and transplantation. In this review, the efficacy and roles of nuclear imaging methods in diagnosis, transplantation and theragnosis are discussed.

Hepatic steatosis is associated with increased hepatic FDG uptake

OBJECTIVE

The use of liver as a reference tissue for semi-quantification of tumour FDG uptake may not be valid in hepatic steatosis (HS). Previous studies on the relation between liver FDG uptake and HS have been contradictory probably because they ignored blood glucose (BG). Because hepatocyte and blood FDG concentrations equalize, liver FDG uptake parallels BG, which must therefore be considered when studying hepatic FDG uptake. We therefore re-examined the relation between HS and liver uptake taking BG into account.

METHODS

This was a retrospective study of 304 patients undergoing routine PET/CT with imaging 60min post-FDG. Average standard uptake value (SUVave), maximum SUV (SUVmax) and CT density (index of HS) were measured in a liver ROI. Blood pool SUV was based on the left ventricular cavity (SUVLV). Correlations were assessed using least squares fitting of continuous data. Patients were also divided into BG subgroups (<4, 4-5, 5-6, 6-8, 8-10 and 10+mmol/l).

RESULTS

SUVave, SUVmax and SUVLV displayed similar relations with BG. SUVmax/SUVLV, but not SUVave/SUVLV, correlated significantly with BG. SUVmax, but not SUVave, correlated inversely with CT density before and after adjusting for BG. SUVmax/SUVave correlated more strongly with CT density than SUVmax. CT density correlated inversely with SUVmax/SUVLV but positively with SUVave/SUVLV.

CONCLUSIONS

Hepatic SUV is more influenced by BG than by HS. Its relation with BG renders it unsuitable as a reference tissue. Nevertheless, hepatic fat does correlate positively with liver SUV, although this is seen only with SUVmax because SUVave is 'diluted' by hepatic fat.

PET/CT mediastinal and liver FDG uptake: effects of biological and procedural factors

INTRODUCTION

To establish the effects of biological and procedural factors on mediastinal and liver [(18) F]-fluorodeoxyglucose (FDG) uptake in oncological FDG positron emission tomography/computed tomography (PET/CT).

METHODS

This retrospective study included 557 patients who had a baseline FDG PET/CT scan in 2008 and 2009. Mediastinal and liver standardised uptake values mean normalised to lean body mass (SUVlbm mean) were measured in each patient. Univariate and multivariate regression models were established. Study population was then dichotomised into low and high body mass index (BMI) groups, and linear regression models were established for the effects of age, incubation period and blood glucose levels.

RESULTS

BMI had the highest adjusted effect (standardised beta coefficient, b = 0.43) (P < 0.001) and partial correlation, adjusting for covariates included in the final model (r = 0.45; P < 0.001) on mediastinal FDG uptake. Partial correlations (r) were 0.22 for age, -0.17 for male gender, -0.25 for incubation period and 0.14 for blood glucose (P < 0.001). The linear regression models showed significant differences in mediastinal FDG uptake between the low and high BMI groups and the effects of age, incubation period and basal blood glucose levels (P < 0.001). Similar results were observed for liver FDG uptake except the partial correlation for incubation period was r = -0.09 (P = 0.02).

CONCLUSION

BMI has the highest effect and correlation on mediastinal and liver FDG uptake. FDG uptake time has a greater effect on mediastinal than liver SUVlbm mean.

Impact of blood glucose, diabetes, insulin, and obesity on standardized uptake values in tumors and healthy organs on 18F-FDG PET/CT

INTRODUCTION

Chronically altered glucose metabolism interferes with (18)F-FDG uptake in malignant tissue and healthy organs and may therefore lower tumor detection in (18)F-FDG PET/CT. The present study assesses the impact of elevated blood glucose levels (BGL), diabetes, insulin treatment, and obesity on (18)F-FDG uptake in tumors and biodistribution in normal organ tissues.

METHODS

(18)F-FDG PET/CT was analyzed in 90 patients with BGL ranging from 50 to 372 mg/dl. Of those, 29 patients were diabetic and 21 patients had received insulin prior to PET/CT; 28 patients were obese with a body mass index >25. The maximum standardized uptake value (SUV(max)) of normal organs and the main tumor site was measured. Differences in SUV(max) in patients with and without elevated BGLs, diabetes, insulin treatment, and obesity were compared and analyzed for statistical significance.

RESULTS

Increased BGLs were associated with decreased cerebral FDG uptake and increased uptake in skeletal muscle. Diabetes and insulin diminished this effect, whereas obesity slightly enhanced the outcome. Diabetes and insulin also increased the average SUV(max) in muscle cells and fat, whereas the mean cerebral SUV(max) was reduced. Obesity decreased tracer uptake in several healthy organs by up to 30%. Tumoral uptake was not significantly influenced by BGL, diabetes, insulin, or obesity.

CONCLUSIONS

Changes in BGLs, diabetes, insulin, and obesity affect the FDG biodistribution in muscular tissue and the brain. Although tumoral uptake is not significantly impaired, these findings may influence the tumor detection rate and are therefore essential for diagnosis and follow-up of malignant diseases.

System approach to modeling of liver glucose metabolism with physiologically interpreted model parameters outgoing from [18F]FDG concentrations measured by PET

New mathematical models from physiologically interpreted parameters capable of evaluating glucose metabolism within the liver and/or the whole body were developed. The group of pigs in a fasting state and the group of pigs with euglycemic supraphysiological hyperinsulinemia were scanned by positron emission tomography after a single dose of [(18)F]FDG tracer. Simultaneously frequent sampling of the dynamic data of [(18)F]FDG plasma concentration in artery, portal vein and hepatic vein was obtained. A system approach to the liver and/or the whole-body system by the tools of linear dynamic sysztem theory was used. Three kinds of structural models, single input and single output or multiple outputs and multiple inputs and single output, were identified. Differences between the group of fasting pigs and the group of pigs in euglycemic supraphysiological hyperinsulinemia were identified by estimated parameters of the structural models. The suitability of the structural mathematical models for the estimation of physiologically interpreted parameters from PET was validated.

The prognostic significance of maximum standardized uptake value of primary tumor in surgically treated non-small-cell lung cancer patients: analysis of 413 cases

BACKGROUND

Integrated PET/CT is widely used in the preoperative staging and prognostic assessment of non-small-cell lung cancer (NSCLC) patients. The aims of this study were to evaluate the prognostic significance of SUVmax of primary tumor in patients undergoing surgical treatment and, in order to minimize technical interferences, to verify whether SUVmax standardized by SUVmax liver or SUVmax blood pool provided additional prognostic information.

PATIENTS AND METHODS

A retrospective study of 413 consecutive NSCLC patients undergoing potentially curative surgical resection after PET/CT obtained in the same PET center over a 6-year period. The SUVmax was calculated drawing region of interest around the primitive tumor, the liver, and the aortic arch in PET images. The same procedure was performed for 2 adjacent planes and the average of these measures was considered.

RESULTS

Nine patients were considered 30-day postoperative deaths and were excluded from the analysis. At the end of the study, 312 (77.2%) of the 404 patients were alive (median follow-up, 26 months) and 92 had died (median survival, 17 months). At multivariate analysis tumor-node-metastasis stage, primary tumor grading and primary tumor SUVmax (T-SUVmax) were found to be independent prognostic factors, while T-SUVmax/SUVmax blood pool ratio, and T-SUVmax/SUVmax liver ratio were not.

CONCLUSIONS

T-SUVmax is an independent predictor for survival in NSCLC patients undergoing surgery and might be helpful in guiding adjuvant treatment strategies. SUVmax of primary tumor normalized by SUV blood pool or SUV liver does not provide additional prognostic information.

¹⁸F-FDG uptake by spleen helps rapidly predict the dose level after total body irradiation in a Tibetan minipig model

OBJECTIVES

To investigate whether (18)F- FDG uptake can be applied in dosimetry to facilitate the rapid and accurate evaluation of individual radiation doses after a nuclear accident.

METHODS

Forty-eight Tibetan minipigs were randomised into a control group (n = 3) and treatment groups (n = 45). (18)F-FDG combined positron-emission tomography and computed tomography (PET/CT) were carried out before total body irradiation (TBI) and at 6, 24 and 72 h after receiving TBI doses ranging from 1 to 11 Gy. Spleen tissues and blood samples were also collected for histological examination, apoptosis and blood analysis.

RESULTS

Mean standardised uptake values (SUVs) of the spleen showed significant differences between the experimental and the control groups. Spleen SUV at 6 h post-irradiation showed significant correlation with radiation dose; Spearman's correlation coefficient was 0.97 (P < 0.01). Histological observations showed that damage to the splenic lymphocyte became more severe with an increase in the radiation dose. Moreover, apoptosis was one of the major routes of splenic lymphocyte death, which was also confirmed by flow cytometry analysis.

CONCLUSIONS

In the Tibetan minipig model, radiation doses have a close relationship with the (18)F-FDG uptake of the spleen. This finding suggests that (18)F-FDG PET/CT may be useful for the rapid detection of individual radiation doses.

[Variations of the hepatic SUV in relation to the body mass index in whole body PET-CT studies]

OBJECTIVE

To evaluate SUV changes in the liver in relation to body mass index (BMI) of patients who undergo whole body PET-CT scans.

MATERIAL AND METHODS

A retrospective study was performed. The variables studied were injected dose of (18F)FDG (mCi), age (years), blood glucose level (mg/dL), height (cm) and weight (kg). BMI was calculated and the SUV mean value was expressed according to gender and BMI. A linear regression analysis was applied to identify the independent variables that best predict the SUV value.

RESULTS

Six hundred and three patients were studied (305 women, 298 men; mean age: 54.9±15.2 years old). Mean SUV measurement was significantly higher in males than females and increased significantly both in male and female patients who were overweight and even more in obese patients. The independent variables that best predicted the SUV value were gender, age, and BMI. In those patients having similar characteristics related to the analyzed variables, the SUV value increased by 0.002 for each increase in one year, and by 0.066 per unit increase in the BMI value.

CONCLUSIONS

Hepatic uptake of (18F)FDG increases according to the patient's BMI. The independent variables that best predict the hepatic SUV value are age and sex of patients. Our findings show that the practice of using the physiological hepatic metabolic activity level as a reference regarding questionable deposits elsewhere in the abdomen and pelvis is not useful, at least in male patients with overweightness and obesity.