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

Patient factors affecting 18F FDG uptake in children

PURPOSE

To characterize physiologic uptake of 18F FDG in children undergoing PET/CT as a step to informing efforts to optimize FDG PET image quality in children.

METHODS

This retrospective study included 193 clinically indicated 18F FDG PET/CT examinations from 139 patients. 3D spherical regions of interest (ROIs) in the liver and in the thigh muscle (an area of uniform low-level uptake) were used to measure counts and mean standardized uptake value by body weight (SUVmean-bw). Counts, SUVs, and liver signal to noise ratio (SNR) were assessed for associations with patient-specific predictor variables using Pearson correlation and multivariable linear regression.

RESULTS

Mean patient age was 11.0 ± 5.4 (SD) years, mean liver SUVmean-bw was 1.77 ± 0.60 and mean liver counts was 5387 ± 1875 Bq/mL. On univariable analysis liver SUVmean-bw and liver counts were strongly correlated with weight (r = 0.87, p < 0.0001), age (r = 0.75, p < 0.0001) and total injected activity (r = 0.85, p < 0.0001). Mean thigh counts were significantly associated only with injected activity/kilogram (r = 0.37, p < 0.0001). On multivariable analysis, body weight and age (which is collinear with body weight) were the only significant independent predictors (p < 0.0001). Liver SNR was moderately associated with all predictors apart from injected activity per kilogram (r = 0.09, p = 0.23).

CONCLUSION

Liver counts on 18F FDG PET/CT have a significant positive association with age and body weight. However, liver SNR has no significant association with injected activity per kilogram suggesting that increasing dose per kilogram may not improve image quality in young children.

Improved identification of tumors in 18F-FDG-PET examination by normalizing the standard uptake in the liver based on blood test data

PURPOSE

Standardized uptake values (SUVs) derived from 18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography are a crucial parameter for identifying tumors or abnormalities in an organ. Moreover, exploring ways to improve the identification of tumors or abnormalities using a statistical measurement tool is important in clinical research. Therefore, we developed a fully automatic method to create a personally normalized Z-score map of the liver SUV.

METHODS

The normalized Z-score map for each patient was created using the SUV mean and standard deviation estimated from blood-test-derived variables, such as alanine aminotransferase and aspartate aminotransferase, as well as other demographic information. This was performed using the least absolute shrinkage and selection operator (LASSO)-based estimation formula. We also used receiver operating characteristic (ROC) to analyze the results of people with and without hepatic tumors and compared them to the ROC curve of normal SUV.

RESULTS

A total of 7757 people were selected for this study. Of these, 7744 were healthy, while 13 had abnormalities. The area under the ROC curve results indicated that the anomaly detection approach (0.91) outperformed only the maximum SUV (0.89). To build the LASSO regression, sets of covariates, including sex, weight, body mass index, blood glucose level, triglyceride, total cholesterol, γ-glutamyl transpeptidase, total protein, creatinine, insulin, albumin, and cholinesterase, were used to determine the SUV mean, whereas weight was used to determine the SUV standard deviation.

CONCLUSION

The Z-score normalizes the mean and standard deviation. It is effective in ROC curve analysis and increases the clarity of the abnormality. This normalization is a key technique for effective measurement of maximum glucose consumption by tumors in the liver.

Are Semiquantitative Methods Superior to Deauville Scoring in the Monitoring Therapy Response for Pediatric Hodgkin Lymphoma?

Tailoring treatment in patients with Hodgkin lymphoma (HL) is paramount to maximize outcomes while avoiding unnecessary toxicity. We aimed to compare the performance of SUVmax reduction (ΔSUVmax%) and the PET ratio (rPET) versus the Deauville score (DS) for assessing the chemotherapy response in pediatric HL patients undergoing 18F-FDG PET-CT. Fifty-two patients with biopsy-proven HL (aged 8-16 years) were enrolled at baseline, interim (after the second or third chemotherapy round) and post-therapy (on completion of first-line chemotherapy). Interim and post-therapy DS, ΔSUVmax% and rPET were compared as response predictors. Patients were classified as responders or non-responders based on a 24-month clinical follow-up. Interim DS showed a sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy of 100%, 80.4%, 100%, 40% and 82.7%, respectively, in predicting the therapy response. Post-therapy DS showed a sensitivity, specificity, PPV, NPV and accuracy of 66.7%, 97.8%, 95.7%, 80% and 94.2%, repsectively. Interim ΔSUVmax% showed a sensitivity, specificity, PPV, NPV and accuracy of 83.3%, 82.6%, 97.4%, 38.5% and 82.7%, respectively, with a 56.3% cutoff. Post-therapy ΔSUVmax% showed a sensitivity, specificity, PPV, NPV and accuracy of 83.3%, 84.8%, 97.5%, 41.7% and 84.6%, respectively, with a 76.8% cutoff. Compared to ΔSUVmax%, DS showed a significantly higher sensitivity, specificity (p < 0.05) and NPV (p < 0.01). The sensitivity, specificity, PPV, NPV and accuracy of rPET in predicting the therapy response at 24 months were 76.1%, 100%, 100%, 35.3% and 78.8%, respectively, with a cut-off of 1.31. DS and rPET showed comparable predictive performance (p > 0.58). In conclusion, DS is an easier method with better performance than ΔSUVmax% and rPET in predicting the chemotherapy response in pediatric HL patients.

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.

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.

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.

Predicting the Recurrence of Hepatocellular Carcinoma after Primary Living Donor Liver Transplantation Using Metabolic Parameters Obtained from 18F-FDG PET/CT

This study evaluated the prognostic value of metabolic parameters based on the standardized uptake value (SUV) normalized by total body weight (bwSUV) and by lean body mass (SUL) measured on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) for predicting tumor recurrence after primary living donor liver transplantation (LDLT) in patients with hepatocellular carcinoma (HCC) without transplantation locoregional therapy. This retrospective study enrolled 49 patients with HCC. The maximum tumor bwSUV (T-bwSUVmax) and SUL (T-SULmax) were measured on PET. The maximum bwSUV (L-bwSUVmax), mean bwSUV (L-bwSUVmean), maximum SUL (L-SULmax), and mean SUL (L-SULmean) were measured in the liver. All metabolic parameters were evaluated using survival analyses and compared to clinicopathological factors. Tumor recurrence occurred in 16/49 patients. Kaplan–Meier analysis revealed that all metabolic parameters were significant (p < 0.05). Univariate analysis revealed that prothrombin-induced by vitamin K absence or antagonist-II; T-stage; tumor number; tumor size; microvascular invasion; the Milan criteria, University of California, San Francisco (UCSF), and up-to-seven criteria; T-bwSUVmax/L-bwSUVmean; T-SULmax; T-SULmax/L-SULmax; and T-SULmax/L-SULmean were significant predictors. Multivariate analysis revealed that the T-SULmax/L-SULmean (hazard ratio = 115.6; p = 0.001; cut-off, 1.81) and UCSF criteria (hazard ratio = 172.1; p = 0.010) were independent predictors of tumor recurrence. SUL-based metabolic parameters, especially T-SULmax/L-SULmean, were significant, independent predictors of HCC recurrence post-LDLT.

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.

Physiological fluorodeoxyglucose uptake of spinal cord in adults

OBJECTIVE

Physiological fluorodeoxyglucose (FDG) uptake of spinal cord needs to be correctly recognized during evaluation of whole-body PET scans, especially for oncological cases. Our aim was to analyze physiological cord FDG uptake and its relation to gender, age, body weight, environmental temperature and time to imaging.

MATERIALS AND METHODS

PET scans of 254 patients in a single year, one patient for every working day were retrospectively selected. Temperature data were obtained from meteorology recordings. Maximum standard uptake value (SUVmax) of spinal cord at cervical and lower thoracic levels were noted. Spinal canal at L5 level, cerebellum and liver were used for normalization. Correlations with age, body weight, time to imaging and environmental temperature were analyzed.

RESULTS

Cervical SUV was higher than thoracic SUV (2.5-2.3). Cervical and lower thoracic SUV's were strongly correlated, highest when corrected with L5 level vertebral canal and liver (corr coeff 0.84 and 0.75) and lowest with cerebellum (corr coeff 0.4). Cervical spinal cord FDG uptake was higher for females than males (2.6 to 2.4). Temperature and age did not change spinal cord uptake. There were weak positive correlations with body weight (corr coeff 0.16 and 0.28, cervical and thoracic). There was weak negative correlation of cervical uptake with time to imaging (corr coeff -0.17).

CONCLUSION

Spinal cord FDG uptake at cervical and lower thoracic levels are strongly correlated. Females have slightly higher cervical SUV. Age and temperature does not change spinal cord FDG uptake in adults. Cord SUV's slightly increased with body weight.

Effects of Fever on 18F-FDG Distribution In Vivo: a Preliminary Study

PURPOSE

Elevated body temperature might change glucose metabolism in human organs. The purpose of this study is to explore ¹⁸F-FDG distribution in febrile patients on the day of ¹⁸F-FDG PET/CT scanning and compare it with patients with a normal temperature.

PROCEDURES

¹⁸F-FDG PET/CT was performed on 69 febrile patients and 82 patients with a normal temperature. Patient sociodemographic data, blood glucose levels before PET/CT, body temperature on the day of the exam, and laboratory test results were collected. Maximal standard uptake values (SUV_max) in the brain, mediastinal blood pool, liver, spleen, and the bone marrow were compared.

RESULTS

Compared with the controls, SUV_max of the febrile patients was significantly lower in the brain, mediastinal blood pool, and the liver (p < 0.01), and higher in the spleen and bone marrow (p < 0.01). In the febrile group, SUV_max was not significantly different between the FDG burden and non-FDG burden patients (p > 0.05). Body temperature was found negatively correlated with SUV_max in the brain (r = - 0.646), mediastinal blood pool (r = - 0.530), and the liver (r = - 0.384), and positively correlated with the SUV_max in the spleen (r = 0.592) and bone marrow (r = 0.651). Multivariate linear regression established body temperature on the day of PET/CT as an independent affecting factor (p < 0.01) for the SUV_max in the brain, mediastinal blood pool, liver, spleen, and bone marrow. The SUV in the brain, liver, and mediastinal blood pool remained different (p < 0.05) after corrected with the SUV_max in the blood pool or liver.

CONCLUSIONS

Fever influences ¹⁸F-FDG distribution in multiple human tissues and organs. Altered ¹⁸F-FDG distribution in vivo might affect results of disease lesion detection and tumor therapy response assessment. Correction with blood pool or liver SUV fails to cancel the effects of fever. The day of fever should be avoided for PET/CT scan, especially in assessing tumor therapy response.

What and how should we measure in paediatric oncology FDG-PET/CT? Comparison of commonly used SUV metrics for differentiation between paediatric tumours

Background

In clinical routine, SUV_max and SUV_peak are most often used to determine the glucose metabolism in tumours by ¹⁸F-FDG PET/CT. Both metrics can be further normalised to SUVs in reference regions resulting in a SUV ratio (SUV_ratio). The aim of the study was to directly compare several widely used SUVs/SUV_ratios with regard to differentiation between common tumours in paediatric patients; a special focus was put on characteristics of reference region SUVs.

Methods

The final study population consisted of 61 children and adolescents with diagnoses of non-Hodgkin lymphoma (NHL, n = 25), Hodgkin lymphoma (HL, n = 14), and sarcoma (n = 22). SUV metrics included SUV_max and SUV_peak as well as both parameters normalised to liver and mediastinal blood pool, respectively, yielding the SUV_ratios SUV_max/liver, SUV_{max/mediastinum}, SUV_peak/liver, and SUV_{peak/mediastinum}.

Results

The metrics SUV_max, SUV_peak, SUV_max/liver, and SUV_peak/liver all proved to be sensitive for tumour differentiation (p ≤ 0.008); in contrast, SUV_{max/mediastinum} and SUV_{peak/mediastinum} revealed to be non-sensitive approaches. Correlation analyses showed inverse associations between reference region SUVs and SUV_ratios (p < 0.05). Multiple regression analyses demonstrated significant effects of factors as bodyweight and uptake time on reference region SUVs (p < 0.01), and thus indirectly on the corresponding SUV_ratios.

Conclusions

In the paediatric population, the ability to differentiate between common tumours remarkably varies between SUV metrics. When using SUV_ratios, the choice of reference region is crucial. Factors potentially influencing reference region SUVs (and thus SUV_ratios) should be taken into account in order to avoid erroneous conclusions. When not possible, SUV_max and SUV_peak represent less complex, more robust alternatives.

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.

Multicenter Trial of [18F]fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Staging of Head and Neck Cancer and Negative Predictive Value and Surgical Impact in the N0 Neck: Results From ACRIN 6685

PURPOSE

The objective of this study was to determine the negative predictive value (NPV) of positron emission tomography (PET)/computed tomography (CT) for the clinically N0 neck on the basis of neck dissection.

METHODS

Participants with newly diagnosed, first-time, head and neck squamous cell carcinoma (HNSCC) and at least one clinically N0 neck side for which dissection was planned were included. A total of 287 participants were prospectively enrolled from 23 American College of Radiology Imaging Network-qualified institutions. PET/CT was compared with findings at neck dissection.

RESULTS

PET/CT scans and pathology findings were available for 270 N0 neck sides from 212 participants. For visual assessment, the NPV specific to the clinical-N0 sides was 0.868 (95% CI, 0.803 to 0.925). For dichotomized maximum standardized uptake value, the NPVs specific to the nodal basins were 0.940 (95% CI, 0.928 to 0.952) and 0.937 (95% CI, 0.925 to 0.949) at prespecified cutoffs of 2.5 and 3.5, respectively. The optimal cutoff maximum standardized uptake value was determined to be 1.8, with an NPV of 0.942 (95% CI, 0.930 to 0.953). The PET/CT-informed surgical treatment plan was changed in 51 of 237 participants (22%) compared with the PET/CT-blinded surgical plan. In 34 participants (14%), this led to planned dissection of additional nodal levels. In 12 participants (5%), this led to fewer planned dissected nodal levels. Negative PET/CT scans in N0 necks was true negative in 87% and false negative in 13%.

CONCLUSION

[¹⁸F]fluorodeoxyglucose-PET/CT has high NPV for the N0 neck in T2 to T4 HNSCC. The surgical treatment plans on the basis of PET/CT findings may be changed in approximately 22% of this group. These findings suggest that [¹⁸F]fluorodeoxyglucose-PET/CT may assist the clinician in deciding on the best therapy for the clinically N0 neck in HNSCC. Well-designed clinical trials should be performed to test the outcome of omitting neck dissection by using PET/CT.

Impacts of time interval on 18F-FDG uptake for PET/CT in normal organs: A systematic review

BACKGROUND

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

METHODS

PubMed, EMBASE, Ovid, and Cochrane databases were searched to identity all potential eligible literature. The study characteristics and relevant data were extracted and analyzed. We adopted the effect size (ES) and the coefficient of determination (R) to best measure the magnitude of the relation between time interval and 18F-FDG uptake in normal organs.

RESULTS

Seven articles and 860 participants were included. The time interval on liver and mediastinal blood pool were relatively medium (R=0.01-0.03, ES = -0.57 and -0.60) but noticeable (R = 0.06, ES = -0.68 and -0.39), respectively. The uptake of 18F-FDG on cerebellum, spleen, bone marrow, muscle, bowel, and adipose remains to be verified as the rare studies. In addition, other factors such as body mass index and blood glucose level appeared to be important which also affect 18F-FDG uptake in normal organs.

CONCLUSION

The impact of time interval on SUVs in liver and mediastinal blood pool were relatively medium but clinically noticeable. More studies need to be done to solve the relation between the SUVs of other organs and time interval.

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 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.

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.

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.

Two-time-point FDG PET/CT: liver SULmean repeatability

OBJECTIVE. The purpose of this study was to evaluate the repeatability of liver mean standardized uptake value normalized to lean body mass (SULmean) in the same patients at different time points within the right lobe of the liver at (18)F-FDG PET/CT, in a clinical setting. MATERIALS AND METHODS. Two PET/CT studies performed on two different dates from each of 130 patients who had normal livers according to structural imaging were included in this reader study. The mean (± SD) length of time between the studies was 235 ± 192 days. SULmean was measured with a 30-mm diameter spherical volume of interest (VOI) placed within the right lobe of the liver (above, below, and at the level of the main portal vein) by two expert readers. ANOVA, intraclass correlation coefficient (ICC), and Bland-Altman analysis were performed. RESULTS. The ICC for the first and second set of studies varied between 0.487 and 0.535 for reader 1 and between 0.472 and 0.545 for reader 2. The mean percentage variation for SULmean between the two time scans for the VOIs placed above, below, and at the level of the main portal vein were 3.55% ± 23.19%, 4.65% ± 23.87%, and 4.30% ± 23.03%, respectively, for reader 1 and 4.49% ± 23.23%, 4.33% ± 23.74%, and 4.48% ± 23.01%, respectively, for reader 2. Using 95% CI, the reference range for intrapatient variations between the studies in liver SULmean was -0.5 to 0.60. CONCLUSION. There is only fair repeatability of liver SULmean measured between two time points in the same patient in a clinical setting. Scan-to-scan intrapatient variation in absolute liver SULmean was -0.5 to 0.60.

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.

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.

Prospective evaluation of the clinical utility of 18-fluorodeoxyglucose PET CT scanning in patients with von hippel-lindau-associated pancreatic lesions

BACKGROUND

The natural history of pancreatic neuroendocrine neoplasms (PNENs) in patients with Von Hippel-Lindau (VHL) disease is poorly defined. Management of patients with PNENs is challenging because there are no reliable preoperative criteria to detect malignant lesions, and the majority of resected tumors are found to be benign. The aim of this study was to determine whether 18-fluorodeoxyglucose-positron emission tomography ((18)FDG-PET) uptake predicts growth and detects malignant VHL-associated PNENs.

STUDY DESIGN

We performed a prospective study of 197 patients with VHL-associated pancreatic lesions. Clinical and imaging characteristics were analyzed to study the associations between FDG-PET uptake, tumor growth, and the development of metastatic disease.

RESULTS

One hundred nine of 197 patients had solid pancreatic lesions and underwent both CT and (18)FDG-PET scanning, which identified 165 and 144 lesions, respectively. Metastatic disease was detected by (18)FDG-PET in 3 patients in whom it was not detected by CT scan and suggested non-neoplastic disease in 3 patients. Maximum standardized uptake values (SUV) on (18)FDG-PET correlated with tumor size on CT (r = 0.47, p < 0.0001), and an increase in SUVmax was associated with tumor growth (r = 0.36, p = 0.0062). No association was seen between (18)FDG-PET uptake and age, VHL genotype, or serum chromogranin A levels.

CONCLUSIONS

Scanning with FDG-PET identifies metastatic disease not detected by CT scan and avoids resection of non-PNEN lesions that have no malignant potential in patients with VHL-associated PNENs. It should be considered as a valuable functional imaging modality in the clinical management of patients with VHL-associated PNENs.