Pretreatment quantitative 18F-FDG PET/CT parameters as a predictor of survival in adenoid cystic carcinoma of the salivary glands

PurposeThe aim of this study was to determine the unique prognostic value of quantitative ¹⁸F-FDG PET/CT parameters to assess progression-free survival (PFS), distant metastasis-free survival (DMFS), and overall survival (OS) in patients with salivary gland adenoid cystic carcinoma (ACC).MethodsWe performed a retrospective study including 23 patients (15 men, 8 women; median age, 58 years; range, 21–91 years) with salivary gland ACC between January 2009 and October 2017 who underwent ¹⁸F-FDG PET/CT scan prior to treatment. Maximum, mean, peak, tumor-to-mediastinal blood pool and tumor-to-liver standardized uptake values (SUV_max, SUV_mean, SUV_peak, SUV_ratio[med] and SUV_ratio[liver]), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were obtained from ¹⁸F-FDG PET/CT. The prognostic value of quantitative ¹⁸F-FDG PET/CT parameters and other clinicopathological variables were evaluated utilizing the Cox proportional regression analysis.ResultsThe 3-year and 5-year OS for all the patients were 90.9%, and 62.3%, respectively. Log rank test determined that the SUV_ratio[med], SUV_ratio[liver], MTV and TLG were predictive factors of DMFS, PFS, and OS (p < 0.05), furthermore, SUV_max, minor salivary gland tumors and DM at initial diagnosis (M1 stage) were predictor for PFS; M1 stage and overall stage 3–4 predicted DMFS (all p < 0.05). Cox regression analyses confirmed that the higher SUV_ratio[med], SUV_ratio[liver], MTV, and TLG values predicted DMFS, PFS and OS independently, whereas SUV_max was an independent predictor of only PFS (p < 0.05).ConclusionsThe pretreatment metabolic ¹⁸F-FDG PET/CT parameters may reflect tumor aggressiveness in patients with salivary gland ACC and may potentially be utilized as a prognostic biomarker.     

Shorter-time dual-phase FDG PET/CT in characterizing solid or ground-glass nodules based on surgical results

ObjectivesWe compared the accuracy of shorter-time dual-phase ¹⁸F-FDG PET/CT in evaluating 94 different lung nodules classified as solid or ground-glass nodules (GGNs).Materials and MethodsEarly and delayed maximum standardized uptake values (SUV_max) as well as the retention index (RI) of each nodule were determined in 75 solid nodules and 19 GGNs.ResultsIn solid nodules, early SUV_max, delayed SUV_max, and RI were higher in malignant than in benign lesions. In GGNs, these values were not significantly lower in the malignant than in the benign lesions.ConclusionIn the patient group with solid nodules, shorter-time dual-phase ¹⁸F-FDG PET/CT could significantly differentiate the malignant from the benign ones.     

Opportunistic body composition evaluation in patients with esophageal adenocarcinoma: association of survival with 18F-FDG PET/CT muscle metrics

Objective

¹⁸F-FDG PET is widely used to accurately stage numerous types of cancers. Although ¹⁸F-FDG PET/CT features of tumors aid in predicting patient prognosis, there is increasing interest in mining additional quantitative body composition data that could improve the prognostic power of ¹⁸F-FDG PET/CT, without additional examination costs or radiation exposure. The aim of this study was to determine the association between overall survival and body composition metrics derived from routine clinical ¹⁸F-FDG PET/CT examinations.

Methods

Patients who received baseline ¹⁸F-FDG PET/CT imaging during workup for newly diagnosed esophageal adenocarcinoma (EAC) were included. From these studies, psoas cross-sectional area (CSA), muscle attenuation (MA), SUV_mean, and SUV_max were obtained. Correlation with overall survival was assessed using a Cox Proportional Hazards model, controlling for age, body mass index, ¹⁸F-FDG dose, glucose level, diabetes status, in-hospital status, and tumor stage.

Results

Among the 59 patients studied, psoas MA and SUV_max were found to be significant predictors of survival (HR 0.94, 95% CI 0.88–0.99, p?=?0.04, and HR 0.37, 95% CI 0.14–0.97, p?=?0.04, respectively) and remained independent predictors. Psoas CSA and SUV_mean did not significantly influence survival outcomes.

Conclusions

Characterization of psoas muscles as a surrogate marker for sarcopenia on baseline ¹⁸F-FDG PET/CT imaging is relatively easily obtained and may offer additional prognostic value in patients with EAC.

     

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

IntroductionChronically altered glucose metabolism interferes with ¹⁸F-FDG uptake in malignant tissue and healthy organs and may therefore lower tumor detection in ¹⁸F-FDG PET/CT. The present study assesses the impact of elevated blood glucose levels (BGL), diabetes, insulin treatment, and obesity on ¹⁸F-FDG uptake in tumors and biodistribution in normal organ tissues.Methods¹⁸F-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.ResultsIncreased 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.ConclusionsChanges 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.     

Clinical significance of MRI/18F-FDG PET fusion imaging of the spinal cord in patients with cervical compressive myelopathy

Purpose

¹⁸F-FDG PET is used to investigate the metabolic activity of neural tissue. MRI is used to visualize morphological changes, but the relationship between intramedullary signal changes and clinical outcome remains controversial. The present study was designed to evaluate the use of 3-D MRI/¹⁸F-FDG PET fusion imaging for defining intramedullary signal changes on MRI scans and local glucose metabolic rate measured on ¹⁸F-FDG PET scans in relation to clinical outcome and prognosis.

Methods

We studied 24 patients undergoing decompressive surgery for cervical compressive myelopathy. All patients underwent 3-D MRI and ¹⁸F-FDG PET before surgery. Quantitative analysis of intramedullary signal changes on MRI scans included calculation of the signal intensity ratio (SIR) as the ratio between the increased lesional signal intensity and the signal intensity at the level of the C7/T1 disc. Using an Advantage workstation, the same slices of cervical 3-D MRI and ¹⁸F-FDG PET images were fused. On the fused images, the maximal count of the lesion was adopted as the standardized uptake value (SUV_max). In a similar manner to SIR, the SUV ratio (SUVR) was also calculated. Neurological assessment was conducted using the Japanese Orthopedic Association (JOA) scoring system for cervical myelopathy.

Results

The SIR on T1-weighted (T1-W) images, but not SIR on T2-W images, was significantly correlated with preoperative JOA score and postoperative neurological improvement. Lesion SUV_max was significantly correlated with SIR on T1-W images, but not with SIR on T2-W images, and also with postoperative neurological outcome. The SUVR correlated better than SIR on T1-W images and lesion SUV_max with neurological improvement. Longer symptom duration was correlated negatively with SIR on T1-W images, positively with SIR on T2-W images, and negatively with SUV_max.

Conclusion

Our results suggest that low-intensity signal on T1-W images, but not on T2-W images, is correlated with a poor postoperative neurological outcome. SUV_max of lesions showing increased signal intensity and SUVR measured on fusion MRI/PET scans are more sensitive parameters for predicting clinical outcome than signal intensity on the MRI scan.     

Anatomical and functional volume concordance between FDG PET,and T2 and diffusion-weighted MRI for cervical cancer: a hybrid PET/MR study

Purpose

To evaluate the concordance among ¹⁸F-FDG PET imaging, MR T2-weighted (T2-W) imaging and apparent diffusion coefficient (ADC) maps with diffusion-weighted (DW) imaging in cervical cancer using hybrid whole-body PET/MR.

Methods

This study prospectively included 35 patients with cervical cancer who underwent pretreatment ¹⁸F-FDG PET/MR imaging. ¹⁸F-FDG PET and MR images were fused using standard software. The percent of the maximum standardized uptake values (SUV_max) was used to contour tumours on PET images, and volumes were calculated automatically. Tumour volumes measured on T2-W and DW images were calculated with standard techniques of tumour area multiplied by the slice profile. Parametric statistics were used for data analysis.

Results

FDG PET tumour volumes calculated using SUV_max (14.30?±?4.70) and T2-W imaging volume (33.81?±?27.32 cm³) were similar (P?>?0.05) at 35 % and 40 % of SUV_max (32.91?±?18.90 cm³ and 27.56?±?17.19 cm³ respectively) and significantly correlated (P?<?0.001; r?=?0.735 and 0.766). The mean DW volume was 30.48?±?22.41 cm³. DW volumes were not significantly different from FDG PET volumes at either 35 % SUV_max or 40 % SUV_max or from T2-W imaging volumes (P?>?0.05). PET subvolumes with increasing SUV_max cut-off percentage showed an inverse change in mean ADC values on DW imaging (P?<?0.001, ANOVA).

Conclusion

Hybrid PET/MR showed strong volume concordance between FDG PET, and T2-W and DW imaging in cervical cancer. Cut-off at 35 % or 40 % of SUV_max is recommended for ¹⁸F-FDG PET/MR SUV-based tumour volume estimation. The linear tumour subvolume concordance between FDG PET and DW imaging demonstrates individual regional concordance of metabolic activity and cell density.     

Reproducibility of functional volume and activity concentration in 18F-FDG PET/CT of liver metastases in colorectal cancer

Purpose

Several studies showed potential for monitoring response to systemic therapy in metastatic colorectal cancer patients with ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET). Before ¹⁸F-FDG PET can be implemented for response evaluation the repeatability should be known. This study was performed to assess the magnitude of the changes in standardized uptake value (SUV), volume and total lesion glycolysis (TLG) in colorectal liver metastases and validate the biological basis of ¹⁸F-FDG PET in colorectal liver metastases.

Methods

Twenty patients scheduled for liver metastasectomy underwent two ¹⁸F-FDG PET scans within 1?week. Bland-Altman analysis was performed to assess repeatability of SUV_max, SUV_mean, volume and TLG. Tumours were delineated using an adaptive threshold method (PET_SBR) and a semiautomatic fuzzy locally adaptive Bayesian (FLAB) delineation method.

Results

Coefficient of repeatability of SUV_max and SUV_mean were ～39 and ～31?%, respectively, independent of the delineation method used and image reconstruction parameters. However, repeatability was worse in recently treated patients. The FLAB delineation method improved the repeatability of the volume and TLG measurements compared to PET_SBR, from coefficients of repeatability of over 85?% to 45?% and 57?% for volume and TLG, respectively. Glucose transporter 1 (GLUT1) expression correlated to the SUV_mean. Vascularity (CD34 expression) and tumour hypoxia (carbonic anhydrase IX expression) did not correlate with ¹⁸F-FDG PET parameters.

Conclusion

In conclusion, repeatability of SUV_mean and SUV_max was mainly affected by preceding systemic therapy. The repeatability of tumour volume and TLG could be improved using more advanced and robust delineation approaches such as FLAB, which is recommended when ¹⁸F-FDG PET is utilized for volume or TLG measurements. Improvement of repeatability of PET measurements, for instance by dynamic PET scanning protocols, is probably necessary to effectively use PET for early response monitoring.     

Dual-time-point <Superscript>18</Superscript>F-FDG PET/CT in the diagnosis of solitary pulmonary lesions in a region with endemic granulomatous diseases

Objective

Granulomatous diseases (GDs) can be metabolically active and indistinguishable from lung cancer on ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) imaging. Evaluation of solitary pulmonary lesions remains a diagnostic challenge in regions with endemic GD. This study sought to determine the efficacy of dual-time-point (DTP) ¹⁸F-FDG PET/computed tomography (CT) imaging in diagnosing solitary pulmonary lesions from such regions.

Methods

A total of 50 patients with solitary pulmonary nodules or masses with confirmed histopathological diagnoses underwent DTP ¹⁸F-FDG PET/CT imaging at 1 and 3 h after tracer injection. The maximum standardized uptake value (SUV_max) on early and delayed scans (SUV_1h and SUV_3h, respectively) and retention index (RI) were calculated for each pulmonary lesion. Receiver operating characteristic analysis was performed to evaluate the discriminating validity of the parameters.

Results

There were 37 malignant and 13 benign solitary pulmonary lesions. Eight of the 13 (62 %) benign lesions were GDs. The sensitivity/specificity/accuracy of SUV_1h, SUV_3h and RI were 84/69/80 %, 84/85/84 %, and 81/54/74 %, respectively. SUV_3h had the best diagnostic performance, especially regarding specificity. The values of SUV_1h and SUV_3h were significantly different between malignant lesions and GD, while the RI values of malignant lesions and GD were both high (18.6 ± 19.5 and 18.7 ± 15.3 %, respectively; P = not significant).

Conclusion

SUV_3h appeared to improve the diagnostic specificity of ¹⁸F-FDG PET/CT in evaluating solitary pulmonary lesions from regions with endemic GD.

     

Steroid responsive inflammatory myofibroblastic tumor of the lung evaluated by FDG PET/CT imaging

A 68-year-old gentleman was referred for ¹⁸F-FDG PET/CT for a pulmonary mass in the left upper lobe which demonstrated intensely FDG-avid confluent pulmonary consolidation in the left upper lobe (SUV_max 15.1). Histopathologic biopsy of the left upper lobe lung mass was consistent with inflammatory myofibroblastic tumor (IMT). The patient was started on steroid treatment in conjunction with antibiotics. Follow-up FDG PET/CT 3 weeks after commence of treatment showed remarkable response of the IMTs to therapy with much less avid FDG uptake (SUV_max 5.4) and marked improvement in the pulmonary consolidation. Nevertheless, the patient underwent left upper lobe lobectomy due to evidence of persistent cystic disease and malignant potential associated with IMTs. Final histopathology was consistent with IMT with no evidence of malignancy.     

Role of 68Ga-DOTATOC PET/CT in initial evaluation of patients with suspected bronchopulmonary carcinoid

Purpose

The objective of this study was to evaluate the role of ⁶⁸Ga-DOTATOC positron emission tomography (PET)/CT scan in patients with suspected pulmonary carcinoid tumour and to compare its results with ¹⁸F-fluorodeoxyglucose (FDG) PET/CT scan.

Methods

In this prospective study, 32 patients (age 34.22?±?12.03 years; 53.1 % female) with clinical suspicion of bronchopulmonary carcinoid were evaluated with ⁶⁸Ga-DOTATOC PET/CT and ¹⁸F-FDG PET/CT. The two imaging modalities were compared, considering the tissue diagnosis as the reference standard.

Results

Based on the reference standard 26 cases were carcinoid tumours [21 typical carcinoids (TC) and 5 atypical carcinoids (AC)] and 6 cases were non-carcinoid tumours. The sensitivity, specificity and accuracy of ⁶⁸Ga-DOTATOC PET/CT in the diagnosis of pulmonary carcinoid tumour were 96.15, 100 and 96.87 % respectively, whereas those of ¹⁸F-FDG PET/CT were 78.26, 11.1 and 59.37 % respectively. The maximum standardised uptake value (SUV_max) of TC on ⁶⁸Ga-DOTATOC PET/CT scan ranged from 3.58 to 55, while that of AC ranged from 1.1 to 32.5. ¹⁸F-FDG PET/CT was true-positive in all cases of AC and false-negative in eight cases of TC (sensitivity for TC 61.9 % and for AC 100 %).

Conclusion

⁶⁸Ga-DOTATOC PET/CT is a useful imaging investigation for the evaluation of pulmonary carcinoids. ¹⁸F-FDG PET/CT scan suffers from low sensitivity and specificity in differentiating the pulmonary carcinoids from other tumours.     

A pilot study on lung cancer detection based on regional metabolic activity distribution in digital low-dose 18F-FDG PET

ObjectivesTo investigate the potential of automatic lung cancer detection on submillisievert dose ¹⁸F-fludeoxyglucose (¹⁸F-FDG) scans using different positron emission tomography (PET) parameters, as a primary step towards a potential new indication for ¹⁸F-FDG PET in lung cancer screening.MethodsWe performed a retrospective cohort analysis with 83 patients referred for ¹⁸F-FDG PET/CT, including of 34 patients with histology-proven lung cancer and 49 patients without lung disease. Aside clinical standard PET images (PET_100%) two additional low-dose PET reconstructions were generated, using only 15 s and 5 s of the 150 s list mode raw data of the full-dose PET, corresponding to 10% and 3.3% of the original ¹⁸F-FDG activity. The lungs were subdivided into three segments on each side, and each segment was classified as normal or containing cancer. The following standardized uptake values (SUVs) were extracted from PET per lung segment: SUV_mean, SUV_hot5, SUV_median, SUV_std and SUV_total. A multivariate linear regression model was used and cross-validated. The accuracy for lung cancer detection was tested with receiver operating characteristics analysis and T-statistics was used to calculate the weight of each parameter.ResultsThe T-statistics showed that SUV_std was the most important discriminative factor for lung cancer detection. The multivariate model achieved an area under the curve of 0.97 for full-dose PET, 0.85 for PET_10% with PET_3.3% reconstructions resulting in a still high sensitivity the PET_10% reconstruction of 80%.ConclusionThis pilot study indicates that segment-based, quantitative PET parameters of low-dose PET reconstructions could be used to automatically detect lung cancer with high sensitivity.Advances in knowledgeAutomated assessment of PET parameters in low-dose PET may aid for an early detection of lung cancer.     

Role of <Superscript>18</Superscript>F-FDG PET/CT in patients affected by Langerhans cell histiocytosis

Purpose

Langerhans cell histiocytosis (LCH) is a rare hematological disorder for which the utility of¹⁸F-FDG PET/CT is unclear. Our aim was to explore the metabolic features of LCH and the possible role of¹⁸F-FDG PET/CT in LCH evaluation.

Materials and methods

We found 17 patients with histologically proven LCH who underwent 17¹⁸F-FDG PET/CT scans for staging and 42 scans for restaging/follow-up purposes. PET/CT results were compared with those obtained from other conventional imaging modalities (bone scintigraphy, plain radiogram, computed tomography, magnetic resonance).

Results

¹⁸F-FDG PET/CT was positive in 15/17 patients, and it detected 36/37 lesions; all bone and extraskeletal lesions, except for a cecal lesion, were¹⁸F-FDG-avid. Only 1/4 of the patients with lung LCH had hypermetabolic lesions. The average SUV_max of the FDG-avid lesions was 7.3 ± 6.7, the average lesion-to-liver SUV_max ratio was 3.4 ± 2.5, and the average lesion-to-blood pool SUV_max ratio was 4 ± 3.2. In comparison to other imaging methods,¹⁸F-FDG PET/CT detected additional lesions or was able to evaluate treatment response earlier in 33/74 cases; it was confirmatory in 38/74 and detected fewer lesions in 3/74 (all three with lung LCH).

Conclusions

¹⁸F-FDG PET/CT seems to be useful for evaluating LCH when compared to conventional imaging, except in pulmonary cases. It can be used both for staging and restaging purposes.

     

Role of 18F-FDG PET/CT in the prediction of gastric cancer recurrence after curative surgical resection

Purpose

The study evaluated the role of preoperative ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in the prediction of recurrent gastric cancer after curative surgical resection.

Methods

A total of 271 patients with gastric cancer who underwent ¹⁸F-FDG PET/CT and subsequent curative surgical resection were enrolled. All patients underwent follow-up for cancer recurrence with a mean duration of 24?±?12?months. ¹⁸F-FDG PET/CT images were visually assessed and, in patients with positive ¹⁸F-FDG cancer uptake, the maximum standardized uptake value (SUV_max) of cancer lesions was measured. ¹⁸F-FDG PET/CT findings were tested as prognostic factors for cancer recurrence and compared with conventional prognostic factors. Furthermore, ¹⁸F-FDG PET/CT findings were assessed as prognostic factors according to histopathological subtypes.

Results

Of 271 patients, 47 (17?%) had a recurrent event. Positive ¹⁸F-FDG cancer uptake was shown in 149 patients (55?%). Tumour size, depth of invasion, presence of lymph node metastasis, positive ¹⁸F-FDG uptake and SUV_max were significantly associated with tumour recurrence in univariate analysis, while only depth of invasion, positive ¹⁸F-FDG uptake and SUV_max had significance in multivariate analysis. The 24-month recurrence-free survival rate was significantly higher in patients with negative ¹⁸F-FDG uptake (95?%) than in those with positive ¹⁸F-FDG uptake (74?%; p?18F-FDG uptake was a significant prognostic factor in patients with tubular adenocarcinoma (p?=?0.003) or poorly differentiated adenocarcinoma (p?=?0.0001). However, only marginal significance was shown in patients with signet-ring cell carcinoma and mucinous carcinoma (p?=?0.05).

Conclusion

¹⁸F-FDG uptake of gastric cancer is an independent and significant prognostic factor for tumour recurrence. ¹⁸F-FDG PET/CT could provide effective information on the prognosis after surgical resection of gastric cancer, especially in tubular adenocarcinoma and poorly differentiated adenocarcinoma.     

Quantitative assessment of atherosclerotic plaques on <Superscript>18</Superscript>F-FDG PET/MRI: comparison with a PET/CT hybrid system

Purpose

PET with ¹⁸F-FDG has the potential to assess vascular macrophage metabolism. ¹⁸F-FDG is most often used in combination with contrast-enhanced CT to localize increased metabolism to specific arterial lesions. Novel ¹⁸F-FDG PET/MRI hybrid imaging shows high potential for the combined evaluation of atherosclerotic plaques, due to the superior morphological conspicuity of plaque lesions. The purpose of this study was to evaluate the reliability and accuracy of ¹⁸F-FDG PET/MRI uptake quantification compared to PET/CT as a reference standard in patients with carotid atherosclerotic plaques.

Methods

The study group comprised 34 consecutive oncological patients with carotid plaques who underwent both PET/CT and PET/MRI with ¹⁸F-FDG on the same day. The presence of atherosclerotic plaques was confirmed by 3 T MRI scans. Maximum standardized uptake values (SUV_max) for carotid plaque lesions and the average SUV of the blood pool within the adjacent internal jugular vein were determined and target-to-blood ratios (TBRs, plaque to blood pool) were calculated.

Results

Atherosclerotic lesions with maximum colocalized focal FDG uptake were assessed in each patient. SUV_max values of carotid plaque lesions were significantly lower on PET/MRI than on PET/CT (2.3?±?0.6 vs. 3.1?±?0.6; P?<?0.01), but were significantly correlated between PET/CT and PET/MRI (Spearman’s r?=?0.67, P?<?0.01). In contrast, TBR_max values of plaque lesions were similar on PET/MRI and on PET/CT (2.2?±?0.3 vs. 2.2?±?0.3; P?=?0.4), and again were significantly correlated between PET/MRI and PET/CT (Spearman’s r?=?0.73, P?<?0.01). Considering the increasing trend in SUV_max and TBR_max values from early to delayed imaging time-points on PET/CT and PET/MRI, respectively, with continuous clearance of radioactivity from the blood, a slight underestimation of TBR_max values may also be expected with PET/MRI compared with PET/CT.

Conclusion

SUV_max and TBR_max values are widely accepted reference parameters for estimation of the radioactivity of atherosclerotic plaques on PET/CT. However, due to a systematic underestimation of SUV_max and TBR_max with PET/MRI, the optimal cut-off values indicating the presence of inflamed plaque tissue need to be newly defined for PET/MRI.

     

Differentiating the grades of thymic epithelial tumor malignancy using textural features of intratumoral heterogeneity via <Superscript>18</Superscript>F-FDG PET/CT

Objective

We aimed to explore the ability of textural heterogeneity indices determined by ¹⁸F-FDG PET/CT for grading the malignancy of thymic epithelial tumors (TETs).

Methods

We retrospectively enrolled 47 patients with pathologically proven TETs who underwent pre-treatment ¹⁸F-FDG PET/CT. TETs were classified by pathological results into three subgroups with increasing grades of malignancy: low-risk thymoma (LRT; WHO classification A, AB and B1), high-risk thymoma (B2 and B3), and thymic carcinoma (TC). Using ¹⁸F-FDG PET/CT, we obtained conventional imaging indices including SUV_max and 20 intratumoral heterogeneity indices: i.e., four local-scale indices derived from the neighborhood gray-tone difference matrix (NGTDM), eight regional-scale indices from the gray-level run-length matrix (GLRLM), and eight regional-scale indices from the gray-level size zone matrix (GLSZM). Area under the receiver operating characteristic curve (AUC) was used to demonstrate the abilities of the imaging indices for differentiating subgroups. Multivariable logistic regression analysis was performed to show the independent significance of the textural indices. Combined criteria using optimal cutoff values of the SUV_max and a best-performing heterogeneity index were applied to investigate whether they improved differentiation between the subgroups.

Results

Most of the GLRLM and GLSZM indices and the SUV_max showed good or fair discrimination (AUC >0.7) with best performance for some of the GLRLM indices and the SUV_max, whereas the NGTDM indices showed relatively inferior performance. The discriminative ability of some of the GLSZM indices was independent from that of SUV_max in multivariate analysis. Combined use of the SUV_max and a GLSZM index improved positive predictive values for LRT and TC.

Conclusions

Texture analysis of ¹⁸F-FDG PET/CT scans has the potential to differentiate between TET tumor grades; regional-scale indices from GLRLM and GLSZM perform better than local-scale indices from the NGTDM. The SUV_max and heterogeneity indices may have complementary value in differentiating TET subgroups.

     

Defining optimal tracer activities in pediatric oncologic whole-body <Superscript>18</Superscript>F-FDG-PET/MRI

Purpose

To explore the feasibility of reducing administered tracer activities and to assess optimal activities for combined ¹⁸F-FDG-PET/MRI in pediatric oncology.

Methods

30 ¹⁸F-FDG-PET/MRI examinations were performed on 24 patients with known or suspected solid tumors (10 girls, 14 boys, age 12?±?5.6 [1–18] years; PET scan duration: 4 min per bed position). Low-activity PET images were retrospectively simulated from the originally acquired data sets using randomized undersampling of list mode data. PET data of different simulated administered activities (0.25–2.5 MBq/kg body weight) were reconstructed with or without point spread function (PSF) modeling. Mean and maximum standardized uptake values (SUV_mean and SUV_max) as well as SUV variation (SUV_var) were measured in physiologic organs and focal FDG-avid lesions. Detectability of organ structures and of focal ¹⁸F-FDG-avid lesions as well as the occurrence of false-positive PET lesions were assessed at different simulated tracer activities.

Results

Subjective image quality steadily declined with decreasing tracer activities. Compared to the originally acquired data sets, mean relative deviations of SUV_mean and SUV_max were below 5 % at ¹⁸F-FDG activities of 1.5 MBq/kg or higher. Over 95 % of anatomic structures and all pathologic focal lesions were detectable at 1.5 MBq/kg ¹⁸F-FDG. Detectability of anatomic structures and focal lesions was significantly improved using PSF. No false-positive focal lesions were observed at tracer activities of 1 MBq/kg ¹⁸F-FDG or higher. Administration of ¹⁸F-FDG activities of 1.5 MBq/kg is, thus, feasible without obvious diagnostic shortcomings, which is equivalent to a dose reduction of more than 50 % compared to current recommendations.

Conclusion

Significant reduction in administered ¹⁸F-FDG tracer activities is feasible in pediatric oncologic PET/MRI. Appropriate activities of ¹⁸F-FDG or other tracers for specific clinical questions have to be further established in selected patient populations.

     

Pretreatment tumor SUV<Subscript>max</Subscript> predicts disease-specific and overall survival in patients with head and neck soft tissue sarcoma

Purpose

Head and neck soft tissue sarcoma (HNSTS) is a rare type of tumor with various histological presentations and clinical behaviors. ¹⁸F-FDG PET/CT is being increasingly used for staging, grading, and predicting treatment outcomes in various types of human cancers, although this modality has been rarely studied in the survival prediction of HNSTS. Here we examined the prognostic value of tumor metabolic parameters measured using ¹⁸F-FDG PET/CT in patients with HNSTS.

Methods

This study included 36 consecutive patients with HNSTS who underwent ¹⁸F-FDG PET/CT scanning prior to treatment at our institution. Tumor gross total volume (GTV) was measured from pretreatment contrast-enhanced CT scans, and maximum standardized uptake value (SUV_max), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured using pretreatment ¹⁸F-FDG PET/CT scans. Univariate and multivariate Cox proportional hazard regression analyses were used to identify associations between imaging parameters and disease-specific survival (DSS) or overall survival (OS).

Results

Univariate analyses showed that SUV_max, MTV, and TLG, but not GTV, were significantly associated with DSS and OS (all P?<?0.05). After controlling for clinicopathological factors, SUV_max, MTV, and TLG were significantly associated with DSS and OS (all P?<?0.05). Patients with a tumor SUV_max value of >7.0 experienced an approximately fivefold increase in mortality in terms of DSS and OS relative to those with a tumor SUV_max <7.0.

Conclusion

Quantitative metabolic measurements on pretreatment ¹⁸F-FDG PET/CT can yield values that are significantly predictive of survival after treatment for HNSTS.

     

Comparison of L-type amino acid transporter 1 expression and L-[3-18F]-α-methyl tyrosine uptake in outcome of non-small cell lung cancer

Objectivel-Type amino acid transporter 1 (LAT1) has associated with tumor growth and poor outcome of patients with non-small cell lung cancer (NSCLC). l-[3-¹⁸F]-α-methyl tyrosine (¹⁸F-FAMT) is an amino acid tracer for positron emission tomography (PET) imaging, and ¹⁸F-FAMT uptake is mediated by LAT1. The purpose of this study is to compare the prognostic significance of ¹⁸F-FAMT uptake in the primary tumors with that of LAT1 expression in patients with NSCLC.MethodsFifty-nine patients with NSCLC were enrolled in this study. All patients underwent ¹⁸F-FAMT PET prior to resection of the tumor, and immunohistochemical staining of the resected tumors were performed to compare the ¹⁸F-FAMT uptake and LAT1 expression. Uptake of ¹⁸F-FAMT was evaluated using semiquantitative standardized uptake value (SUV_max), and the cutoff value was determined to discriminate patients with high SUV_max from those with low SUV_max. Expression of LAT1 was evaluated by the score of staining intensity through 1 to 4. SUV_max and LAT1 expression were compared according to the clinicopathological variables.ResultsThe best discriminative cutoff value of ¹⁸F-FAMT SUV_max within the primary tumors was 1.6. The high SUV_max (>1.6) in ¹⁸F-FAMT PET was significantly associated with male, and positive LAT1 expression was significantly associated with male and nonadenocarcinoma. In the univariate analysis, high SUV_max (>1.6) in ¹⁸F-FAMT PET and positive LAT1 expression were significant predictor of the poor outcome. Multivariate analysis confirmed that positive LAT1 expression was an independent and significant factor for predicting poor prognosis in NSCLC (P=.035).ConclusionLAT1 expression is a stronger prognostic factor than ¹⁸F-FAMT uptake in surgically resected NSCLC.     

PET/CT studies of multiple myeloma using 18 F-FDG and 18 F-NaF: comparison of distribution patterns and tracers’ pharmacokinetics

Objective

The aim of this prospective study is to evaluate the combined use of fluorine-18 fluorodeoxyglucose (¹⁸?F-FDG) and fluorine-18 sodium fluoride (¹⁸?F-NaF) PET/CT in the skeletal assessment of patients with multiple myeloma (MM) and to compare the efficacy of these two PET tracers regarding detection of myeloma-indicative osseous lesions.

Patients and methods

The study includes 60 patients with multiple myeloma (MM) diagnosed according to standard criteria. All patients underwent dynamic (dPET/CT) scanning of the pelvis as well as whole body PET/CT studies with both tracers. The interval between the two exams was one day. Sites of focal increased ¹⁸?F-FDG uptake were considered as highly suspicious of myelomatous involvement. The lesions detected on the ¹⁸?F-NaF PET/CT scans were then correlated with those detected on ¹⁸?F-FDG PET/CT, which served as a reference. Moreover, the ¹⁸?F-FDG PET/CT results were also correlated with the low-dose CT findings. The evaluation of dPET/CT studies was based on qualitative evaluation, SUV calculation, and quantitative analysis based on a 2-tissue compartment model and a non-compartmental approach.

Results

Whole body ¹⁸?F-FDG PET/CT revealed approximately 343 focal lesions while ¹⁸?F-NaF PET/CT revealed 135 MM-indicative lesions (39 % correlation). CT demonstrated 150 lesions that correlated with those in ¹⁸?F-FDG PET/CT (44 % correlation). Six patients demonstrated a diffuse pattern of disease with ¹⁸?F-FDG, while 15 of them had a mixed (diffuse and focal) pattern of skeletal ¹⁸?F-FDG uptake. A high number of degenerative, traumatic and arthritic disease lesions were detected with ¹⁸?F-NaF PET/CT. In three patients with multiple focal ¹⁸?F-FDG-uptake, ¹⁸?F-NaF PET/CT failed to demonstrate any bone lesion. The dPET/CT scanning of the pelvic area with ¹⁸?F-FDG and ¹⁸?F-NaF revealed 77 and 24 MM-indicative lesions, respectively. Kinetic analysis of ¹⁸?F-FDG revealed the following mean values: SUV_aver?=?5.1, k₁?=?0.37 (1/min), k₃?=?0.10 (1/min), V_B?=?0.06, influx?=?0.04 (1/min), FD?=?1.28; the respective values for ¹⁸?F-NaF were SUV_average?=?10.7, k₁?=?0.25 (1/min), k₃?=?0.34 (1/min), V_B?=?0.02, influx?=?0.10 (1/min), FD?=?1.37. Apart from the correlation between V_B of ¹⁸?F-FDG and k₁ of ¹⁸?F-NaF (r?=?0.54), no other significant correlation was observed between the two tracers’ kinetic parameters. We found a significant correlation between FD and SUV_average (r?=?0.93), FD and SUV_max (r?=?0.80), FD and influx ( r?=?0.85), as well as between influx and SUV_average (r?=?0.74) for ¹⁸?F-FDG. In ¹⁸?F-NaF we observed the most significant correlations between FD and SUV_average (r?=?0.97), FD and SUV_max (r?=?0.87), and between influx and k₁ (r?=?0.72).

Conclusion

The combined use of ¹⁸?F-FDG PET/CT and ¹⁸?F-NaF PET/CT provides different molecular information regarding the biological processes that take place in a MM osseous lesion. ¹⁸?F-FDG PET/CT proved to be a more specific biomarker than ¹⁸?F-NaF PET/CT in multiple myeloma skeletal assessment.     

Evaluation of intratumoural heterogeneity on 18F-FDG PET/CT for characterization of peripheral nerve sheath tumours in neurofibromatosis type 1

Purpose

The aim of the study was to evaluate the potential usefulness of intratumoural tracer uptake heterogeneity on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT as compared to a cut-off maximum standardized uptake value (SUV_max) for characterization of peripheral nerve sheath tumours (PNSTs) in neurofibromatosis type 1 (NF1).

Methods

Fifty patients suffering from NF1 were examined by ¹⁸F-FDG PET/CT. Intralesional tracer uptake was analysed qualitatively and semi-quantitatively by measuring the mean and maximum SUV. Uptake heterogeneity was graded qualitatively using a three-point scale and semi-quantitatively by calculating an SUV-based heterogeneity index (HI_SUV). Cohen’s κ was used to determine inter- and intra-rater agreement. Histopathological evaluation and clinical as well as radiological follow-up examinations served as the reference standards.

Results

A highly significant correlation between the degree of intratumoural uptake heterogeneity on ¹⁸F-FDG PET and malignant transformation of PNSTs was observed (p?<?0.0001). Semi-quantitative HI_SUV was significantly higher in malignant PNSTs (MPNSTs) than in benign tumours (p?=?0.0002). Both intralesional heterogeneity and SUV_max could be used to identify malignant tumours with a sensitivity of 100 %. Cohen’s κ was 0.86 for inter-rater agreement and 0.88 for intra-rater agreement on heterogeneity.

Conclusion

MPNSTs in patients with NF1 demonstrate considerable intratumoural uptake heterogeneity on ¹⁸F-FDG PET/CT. Assessment of tumour heterogeneity is highly reproducible. Both tumour heterogeneity and a cut-off SUV_max may be used to sensitively identify malignant PNSTs, but the specificity is higher for the latter. A combination of both methods leads to a non-significant improvement in diagnostic performance.