Objective(s): This study aimed to evaluate the role of pretreatment SUVmax and volumetric FDG positron emission tomography (PET) parameters in the differentiation between benign and malignant mediastinal tumors. In addition, we investigated whether pretreatment SUVmax and volumetric FDG-PET parameters could distinguish thymomas from thymic carcinomas, and low-risk from high-risk thymomas.Methods: This study was conducted on 52 patients with mediastinal tumors undergoing FDG-PET/CT. Histological examination indicated that 29 mediastinal tumors were benign, and 23 cases were malignant. To obtain quantitative PET/CT parameters, we determined the maximum standardized uptake value (SUVmax), volumetric parameters, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) for primary tumors using SUVmax cut-off value of 2.5. SUVmax, MTV and TLG of benign and malignant tumors were compared using the Mann-Whitney U test. Moreover, receiver-operating curve (ROC) analysis was applied to identify the cut-off values of SUVmax, MTV and TLG for the accurate differentiation of benign and malignant tumors. SUVmax, MTV and TLG were compared between thymomas and thymic carcinomas, as well as low-risk and high-risk thymomas.Results: Mean SUVmax, MTV and TLG of malignant mediastinal tumors were significantly higher compared to benign tumors (P<0.001). Sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of SUVmax were 78.2%, 86.2%, 82.6%, 81.8%, and 83.3%, respectively. These values were estimated at 82.6%, 96.6%, 90.4%, 95%, and 87.5% for MTV and TLG, respectively. Additionally, optimal cut-off values for the differentiation of benign and malignant mediastinal tumors were determined at 4.2 and 22.3 mL and 79.7 g for SUVmax, MTV and TLG, respectively. Mean SUVmax, MTV and TLG of thymic carcinomas were significantly higher compared to thymomas (P<0.01), while no significant differences were observed in the mean quantitative parameters between low-risk and high-risk thymomas.Conclusion: Although SUVmax, MTV and TLG could not distinguish between low-risk and high-risk thymomas, these parameters might be able to differentiate benign tumors from malignant mediastinal tumors noninvasively. These parameters could be used to distinguish between thymomas and thymic carcinomas as well. Therefore, FDG-PET/CT parameters seem to be accurate indices for the detection of malignant mediastinal tumors.

Introduction: 18F-Choline PET-CT is an increasingly used technique in patients with prostate cancer. The main indication is to localise the disease in patients with biochemical recurrence. To accurately interpret 18F-Choline PET, knowledge of normal tracer distribution is paramount. The aim of this study was to describe the normal distribution pattern of 18F-Choline by measuring the maximum standardized uptake values (SUVs) of various organs.Methods: 18F-Choline PET was performed in ten consecutive patients. Approximately 370 MBq of tracer was injected intravenously and a low amperage CT scan was performed for attenuation correction of PET images.Maximum SUVs were calculated on the reconstructed images for various organs. These SUVmax values depend on multiple factors and could be variable depending on the reconstruction CT methods, acquisition time and region of interest (ROI) parameters.Results: Physiologic symmetric increased tracer uptake was noted in the salivary glands and parotid glands. Intense physiological uptake was present in the liver, pancreas, duodenum, stomach, kidneys and urinary bladder and moderate to intense uptake in the sublingual glands, lacrimal glands, nasal mucosa, thyroid gland, tonsils, adrenal glands, large bowel, bone marrow and spleen. Low-grade-to-moderate uptake was present in the choroid plexus, pituitary gland, soft palate, pharynx, left myocardium, lungs, mediastinal blood pool, testicles and muscles. Prostate and prostatic beds were excluded from the volumes of interest.Conclusion: This study is the first one to describe a normal range of SUVmax values for 18F-Choline PET in various organs.

Background: The use of 68-gallium prostatespecific membrane antigen positron emission tomography/computed tomography (68Ga-PSMAPET/CT) scan has recently received particular attention in the evaluation of prostate cancer patients. Objectives: The present study aimed to evaluate the relationship between the prostate-specific antigen (PSA) level, Gleason score, and 68Ga-PSMAPET/CT findings in prostate cancer patients. PatientsandMethods: In this cross-sectional study, 80 male patients with a definitive diagnosis of prostate cancer, whowere candidates for 68Ga-PSMA PET/CT scan for both initial staging and restaging, were included. Restaging indicated biochemical recurrence, which refers to a detectable level of PSA after being documented undetectable following a definitive primary treatment. All prostate cancer patients, who were not initially treated with a definitive therapy, were excluded from the study. A cutoff value,4 was considered significant for maximum standardized uptake value (SUVmax) to differentiate benign from malignant 68Ga-PSMA-avid lesions. Any 68Ga-PSMA uptake outside the prostate bed, especially in the lymph nodes, bones, and visceral organs, was considered metastatic. Results: Comparison of the PSA level between two subgroups with and without metastasis demonstrated a higher PSA level in patients with metastatic abdominal lymph nodes and a slightly higher PSA level in patients with metastatic pelvic lymph nodes. No significant correlation was found between the Gleason score and the total PSA. There was also no significant association between the level of PSA and the type of Lymph node involvement (single or multiple) in different involved areas. Besides, there was no significant correlation between the SUVmax and the level of PSA and the Gleason score in different involved areas. Conclusion: The SUVmax value in 68Ga PSMA PET/CT scan provides a reliable predictor for neither the grade of prostate cancer, nor the metastatic status associated with cancer progression. The measurement of total PSA may predict metastasis to the abdominal and pelvic lymph nodes caused by prostate cancer.

Introduction: 18F-FDG PET/CT provides very effective results in detecting metastases of breast cancer. In our study, we investigated the relationship between maximum standard uptake value (SUVmax) and prognostic pathologic factors in breast cancer cases with isolated bone metastasis and whether there was any difference in terms of prognostic pathologic factors between the group with and without bone metastasis. Methods: Between 2013 and 2016, isolated bone metastases (55 female; 56± 12 years; 32-87), and non-metastatic (46 female; 55± 13 years; 30-81) patients who were referred to department of nuclear medicine and underwent 18F-FDG PET/CT for staging were included in the study. PET/CT images of patients and pathologic prognostic factors were evaluated retrospectively. SUVmax value of the most intense activity from metastatic bone lesions was calculated. p <0. 05 was considered statistically significant. Results: In the metastatic group, there was no statistically significant relationship between measured SUVmax value of bone metastasis and pathologic prognostic factors. A statistically significant difference was found between the metastatic group and the non-metastatic group in terms of lymph node stage, lymphovascular/perineural invasion. The lymph node stage in the metastatic group was higher than the non-metastatic group. The presence of lymphovascular/perineural invasion in bone metastasis cases was more than in the non-metastatic group. Conclusion: In our study, it was determined that there was a relationship between the lymph node stage, lymphovascular/ perineural invasion and formation of bone metastasis in breast cancer. Between SUVmax values and other factors in the metastatic group, no significant relationship was detected.

Background: Flourine-18 fl, uorodeoxyglucose positron emission tomography/computed tomography ( F-FDG PET/CT) scan is employed for initial staging and restaging of esophageal cancer patients. Objectives: The present study aimed to assess the value of a semi-quantitative parameter of 18 F-FDG PET/CT scan, that is, maximum standardized uptake value (SUVmax), to determine its correlation with patient survival in two subtypes of esophageal cancer, including squamous cell carcinoma (SCC) and adenocarcinoma. Patients and Methods: This cross-sectional study was performed on patients with esophageal SCC and adenocarcinoma, undergoing 18 18 F-FDG PET/CT semi-quantitative parameter (SUVmax) was determined by reviewing the PET/CT images. The patients were reevaluated using F-FDG PET/CT scan for initial staging before any treatment. The 18 F-FDG PET/CT scan for restaging within 12-24 months. Results: No signifi, cant diff, erence was observed in the SUVmax values of the primary tumor, metastatic lymph nodes, or distant metastasis between the adenocarcinoma and SCC groups, regardless of response to treatment. Similarly, no signifi, cant association was found between the short-term survival of patients with adenocarcinoma and the SUVmax values of the primary tumor, metastatic lymph nodes, or distant metastasis. Based on the survival curve, one-and two-year survival rates were estimated at 75% and 63. 9% in patients with SCC and at 80% and 60% in patients with adenocarcinoma, respectively. In the SCC group, a signifi, cantly higher SUVmax 18 was detected in deceased patients with distant metastatic lesions compared to cancer survivors. According to the area under the ROC curve, the SUVmax of metastatic lesions showed high potential for predicting the mortality of SCC patients. Conclusion: The assessment of SUVmax in distant metastatic lesions by F-FDG-PET/CT may help predict the survival of patients with esophageal SCC. However, 18 F-FDG-PET/CT fi, ndings were not associated with the survival of esophageal adenocarcinoma,therefore, further evaluations on a larger sample size and a longer follow-up are required.

Introduction: Early recurrence of hepatocellular carcinoma (HCC) is a major risk factor affecting survival even after hepatectomy. Many clinical, biochemical parameters and pathological grading like fibrosis 1 index have been used for risk stratifying HCC. However not many studies have combined all of them. It is therefore important to risk stratify HCC especially with newer PET based metabolic parameters to see if they match with existing clinicopathological parameters to achieve better clinical outcome. The objectives of this study were twofold,firstly, to evaluate [ F]FDG PET as a prognostic biomarker to predict tumour recurrence. Secondly, if clinicopathological parameters combined with PET indices increase the risk correlate in predicting HCC disease recurrence. 18 Methods: Records of 200 adult HCC patients were analysed, (6: 1, Male: Female,mean age ±,SD, 52 ±,2 year). All underwent [ 18 F]FDG PET (PET MR: PET CT = 168: 32) and subsequent therapy. Patients had a follow up for at least 15 months or onset of first recurrence, whichever was earlier. Clinicopathological data, alpha-fetoprotein (AFP) titres, SUVmax and few other PET indices were documented along with details of first recurrence. Statistical analysis was also performed. Results: In a multivariate analysis of various prognostic factors including T (SUVmax)/ L (SUVmax), serum alphafetoprotein, T stage, size of tumour, and vascular invasion of tumour, T (SUVmax)/ L (SUVmax) was the most significant with a cut off value of 1. 9. Only vascular invasion of tumour and AFP titres had additional significance. 16% ( 32/200 patients) developed recurrence (OR 1. 673). Comparing the low and high AFP titres by Kaplan Meir curve, P was found to be 0. 039 that predicted a worse prognosis in patients with higher AFP titres. Similarly patients with higher SUV T/L: ratio of tumour SUVmax to liver (> 1. 9) also revealed higher recurrence rate. Cut-off SUVmax was 3. 03 g/ml in our series (range 2. 5-23. 8 g/ml) and found to be strongly associated with AFP, tumour size, number, and histological grade of tumour. Conclusion: Our study shows that PET based metabolic indices are effective robust tools to predict tumour recurrence in aggressive HCC. Secondly, when clinicopathological parameters are combined with PET based indices there is better prediction of HCC recurrence and one can reclassify HCC patients into mild, moderate, and high-risk groups. We found it very useful in predicting poor clinical outcome especially in high-risk HCC patients,so that stricter surveillance measures can be recommended to identify early recurrence and offer appropriate therapy. The strength of this study lies in the fact that the observed associations between the combined parameters were found to be stronger than those reported in the past.

Background: Melanoma is one of the most serious types of skin cancer and one of the leading causes of cancer-related mortality worldwide. Objectives: This study aimed to investigate the association between 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/ computed tomography (PET/CT) scan findings and the pathological characteristics of primary tumors in patients with malignant melanoma. Patients and Methods: In this cross-sectional study, the baseline data of 103 patients with cutaneous or mucosal melanoma (stage III or IV) were recorded, and tumor characteristics and PET/CT scan findings were analyzed. The association between each pathological finding and PET/CT results was also investigated. Results: Patients without a free margin had a significantly higher mean standardized uptake value (SUVmax) of lung metastasis compared to patients with a free margin (3. 12 vs. 1. 69,P = 0. 047). Also, patients with ulceration had a significantly higher mean SUVmax of lung metastasis compared to patients without ulceration (3. 28 vs. 1. 81,P = 0. 041). Based on the results, increased primary tumor thickness was associated with a higher SUVmax of lung metastasis. However, there was no significant association between the metastasis type (single vs. multiple) and free margin, ulceration, or Ki-67 protein. The mean SUVmax of lung metastasis was significantly higher in mucosal melanoma compared to cutaneous melanoma. However, the mean SUVmax values of other metastases (bone, liver, and lymph nodes), even the primary lesion itself, were not significantly different between cutaneous melanoma and mucosal melanoma. Conclusion: The primary tumor margin status, ulceration, tumor thickness, primary tumor location (cutaneous vs. mucosal), and the presence of lung metastasis were significantly associated with PET/CT scan findings.

Background: In the present study, PET/CT imaging characteristics were explored to investigate the prognostic value of 18F–fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in oesophageal squamous cell carcinoma (ESCC). Materials and Methods: Baseline PET/CT and clinical characteristics were collected in 125 patients with ESCC treated with radical radiotherapy from 2007–2016. The maximum standardized uptake value (SUVmax) of the primary gross tumour (SUVmax-T) and metastatic lymph nodes (SUVmax-N) were separately measured using X-tile. Overall survival (OS) and progression free survival (PFS) were estimated according to the Kaplan–Meier method. A multivariate Cox model was used to establish the independent prognostic factors. Results: The gross tumours presented higher 18F-FDG uptake than normal tissues. The OS and PFS did not show significant differences between patients with different SUVmax-T values. However, patients with SUVmax-N ≥ 11 had a significantly worse OS and PFS than those with SUVmax-N <11 (P<0.05). A weak correlation was observed in SUVmax-T and SUVmax-N. The OS and PFS of patients with PET-negative lymph nodes (LNs) were significantly better than those with PET-positive LNs. However, the OS and PFS of patients with one or two PET-positive LNs were not significantly better than those with more than two PET-positive LNs. In multivariate analysis, SUVmax-N was suggested to be an independent predictor for OS and PFS. Conclusions: SUVmax-N, but not SUVmax-T, is an independent prognostic indicator for patients with ESCC.

Objective(s): 18F-Fluorodeoxyglucose (FDG) uptake in children is different from that in adults. Physiological accumulation is known to occur in growth plates, but the pattern of distribution has not been fully investigated. Our aim was to evaluate the metabolic activity of growth plates according to age and location. Methods: We retrospectively evaluated 89 PET/CT scans in 63 pediatric patients (male: female=25: 38, range, 0– 18 years). Patients were classified into four age groups (Group A: 0– 2 years, Group B: 3– 9 years, Group C: 10– 14 years and Group D: 15-18 years). The maximum standardized uptake value (SUVmax) of the proximal and distal growth plates of the humerus, the forearm bones and the femur were measured. The SUVmax of each site and each age group were compared and statistically analyzed. We also examined the correlations between age and SUVmax. Results: As for the comparison of SUVmax in each location, the SUVmax was significantly higher in the distal femur than those in the other sites (p< 0. 01). SUVmax in the distal humerus and the proximal forearm bones were significantly lower than those in the other sites (p< 0. 01). In the distal femur, there was large variation in SUVmax, while in the distal humerus and the proximal forearm bones, there was small variation. As for the comparison of SUVmax in each age group, the SUVmax in group D tended to be lower than those in the other groups, but in the distal femur, there was no significant difference among each age group. Conclusion: Our data indicate that FDG uptake in growth plates varies depending on the site and age with remarkable uptake especially in the distal femur.