Preliminary clinical assessment of dynamic 18F-fluorodeoxyglucose positron-emission tomography/computed tomography for evaluating the clinicopathological grade in patients with non-Hodgkin's lymphoma: a prospective study.

OBJECTIVE: We prospectively assessed the diagnostic capacity of dynamic and dual-time-point F-fluorodeoxyglucose PET/computed tomography and explored the most appropriate scan timing for clinicopathological discrimination of non-Hodgkin's lymphoma. METHODS: Thirteen patients underwent dynamic scans dynamic scans (5-15, 15-25, and 25-35 minute postinjection) and consecutive dual-time-point scans (1- and 2-hour postinjection). For five indolent and 16 aggressive lymphomas, we statistically compared the maximum standardized uptake value (SUVmax) and the retention index of the SUVmax (RI-SUVmax) for each scan and explored the diagnostic capacities using receiver operating characteristic (ROC) curve analyses. RESULTS: SUVmax increased progressively over time in all lymphomas and was significantly higher for aggressive lymphoma than for indolent lymphoma in each timephase. RI-SUVmax of dynamic scans (RI-SUV-dynamic) was significantly higher in aggressive than in indolent lymphoma. The cutoff values obtained a sensitivity of 94%, positive-predictive value of 94%, and accuracy of 91% for SUVmax analyses of the dynamic second and third phases, 1-hour early phase, and 2-hour delayed phase, and a sensitivity of 88%, positive-predictive value of 93%, and accuracy of 86% for RI-SUV-dynamic. In contrast, for the dynamic first phase, the cutoff value of SUVmax yielded moderate sensitivity of 69%, a positive-predictive value of 92%, and an accuracy of 71%. The area under the ROC curve (AUC) of the RI-SUV-dynamic had the highest value (0.938), whereas the AUCs of the other ROC analyses were not significantly different. CONCLUSION: The dynamic second and third phase could potentially provide good predictors of clinicopathological discrimination, as can the early and delayed phases.

A reduced liver 18F-FDG uptake may be related to hypoalbuminemia in patients with malnutrition.

OBJECTIVE: 18F-FDG PET/CT is a hybrid imaging method widely used as a useful, noninvasive imaging modality for evaluating various neoplastic diseases. When assessing the tumor uptake, the liver and the mediastinal blood pool are often used as a reference region. In daily clinical practice, the 18F-FDG uptake in the liver sometimes appears to decrease on PET images of patients with malnutrition. The purpose of this study was to investigate whether or not the liver 18F-FDG uptake is decreased in patients with malnutrition. METHODS: We retrospectively analyzed 246 patients who underwent 18F-FDG PET/CT from January 2018 to June 2018 and whose blood serum albumin was measured within 1 month of PET/CT. We compared the liver uptake and mediastinal blood uptake of patients with low serum albumin level (< 4.0 g/dl) and hypoalbuminemia (< 3.5 g/dl) with those with a normal serum albumin level (≥ 4.0 g/dl). Correlations between the liver and mediastinal blood uptake and the serum albumin level were also calculated. RESULTS: The maximum standardized uptake value (SUVmax) and mean standardized uptake value (SUVmean) of the liver in 117 patients with low serum albumin were 3.1 ± 0.5 and 2.3 ± 0.3, respectively, while they were 2.9 ± 0.4, 2.0 ± 0.3 in 29 patients with hypoalbuminemia; these values were all significantly lower than the respective ones (3.4 ± 0.5, 2.5 ± 0.4) in 129 patients with normal serum albumin (all p < 0.001). The SUVmean of the mediastinal blood uptake in patients with hypoalbuminemia and normal serum albumin were 1.6 ± 0.2 and 1.7 ± 0.3, respectively (p = 0.053). The serum albumin level demonstrated a significantly positive, moderate correlation with the liver SUVmean, showing a regression line of y = 0.31x + 1.1 (r = 0.41, p < 0.001). CONCLUSION: The liver 18F-FDG uptake tended to decrease in patients with hypoalbuminemia. In the patients with malnutrition, the mediastinal blood pool may be a more stable reference than the liver for evaluating the tumor activity because hypoalbuminemia is considered to less strongly influence the mediastinal blood pool than that in the liver.