Objective To investigate the value of 18 F-fluorodeoxyglucose (18 FDG)positron emission tomography and computer tomography (PET/CT)in the diagnosis and localization of ectopic ACTH syndrome (EAS)induced by lung cancer,and to increase the accuracy rate of diagnosis of EAS.Methods 8 patients were histopathologically proven to be lung cancer.18 FDG PET/CT wholebody and brain scan were performed;magnetic resonance imaging (MRI),99m Tc-octreotide (OCT)imaging and inferior petrosal sinus sampling (IPSS)were done in all patients.On 18 FDG PET/CT images,the SUVmax values of lesions and the SUVmax ratio of lesion tissue to normal lung tissue were calculated.Results ① 8 patients with EAS included 2 cases of carciniod,4 cases of atypical carciniod,and 2 cases of small cell lung cancer.The ACTH levels in inferior petrosal sinus and peripheral veins of 8 patients had no difference.②The chest CT showed there were pulmonary nodules in 6 cases (75%),among them 2 cases were atypical lesions.5 cases of pituitary adenomas were found by MRI (25%),and OCT imaging was positive in 2 cases (25%).③The 18 FDG PET/CT showed nodular,mass like or patch samples with high metabolic activity in 8 cases (100%)of pulmonary lesions.The SUVmax of tumor was 0.72 to 14.05 (3.67±4.68),and the ratio of SUVmax of lesion tissue to normal lung tissue was 1.69 to 27.54 (8.14 ± 9.63).18 FDG hypermetabolism was found in 8 cases of bilateral adrenal hyperplasia,while 4 cases showed pituitary tumor.Conclusion Lung cancer is a common source of EAS,especially carcinoid.18 FDG PET may show lower glucose metabolism.18 FDG PET/CT should be used as an assisted method to diagnose EAS.

Objective To retrospectively study the biodistribution of 68Ga-DOTA-TATE as a SSTR imaging agent in human subjects.Methods A total of 106 patients with suspected disease were enrolled in this study.All patients were histologically proven for having either a single tumor ＜2 cm or without evidence of tumor during follow-up.Patients underwent PET/CT whole-body scan 17-100 min after intravenous injection of 55.2-220.0 MBq 68Ga-DOTA-TATE.ROI was drawn for measuring SUV of tracer-avid pathologies.One-way analysis of variance and two-sample t test were used for statistical analysis.Results High 68Ga-DOTA-TATE avidity was found in pituitary,with SUVmax of 4.00± 1.21.Tracer was excreted mainly through urinary system resulting in highest uptake in the urinary tracts.The SUVmax of kidney cortex was 19.01 ± 5.45.Mediastinal blood pool and liver SUVmax were 0.93±0.33 and 7.69±2.26,respectively.Mild uptake of 68Ga-DOTA-TATE was found in the brain,cerebellum,lung and muscle,all lower than that of mediastinal blood pool.Moderate accumulation of 68 Ga-DOTA-TATE (close to or slightly higher than liver) was found in adrenal gland and spleen,with SUVmax 7.61 ± 3.42 and 8.63± 2.31,respectively.Other organs (pituitary,salivary gland,thyroid,pancreas,small intestine,colon,uterus,prostate and bone) showed tracer uptake in the range between those of mediastinal blood pool and liver.68Ga-DOTA-TATE distribution in pancreas was not uniform.Nine patients had focal accumulation in the uncinate process of pancreas with highest SUVm~ up to 8.48.However,the SUVmax and SUV in the rest of pancreas (head,neck,body and tail) showed insignificant difference (F values:0.703,0.563,both P＞0.05).68Ga-DOTA-TATE uptake in each organ reached equilibrium quickly after injection but with slight increase over time.The changes in SUV,however,showed insignificant difference among organs,including different parts of pancreas (t values:from -0.09 to 1.75,from-1.70 to-0.42,respectively,all P＞0.05).Conclusions The biodistribution of 68Ga-DOTA-TATE reaches equilibrium shortly after intravenous administration and is stably maintained.The biodistribution activities are organ-specific,and characteristic to that of SSTR concentration.

Objective To investigate the characteristics of NEN metastasis with SSTR PET/CT and to correlate the results with FDG-PET and pathology.Methods From November 2011 to August 2016,a total of 43 patients with NEN (18 males,25 females;age range:26-74 years) were recruited into this retrospective study;they underwent 68Ga-DOTA-TATE PET/CT (TATE-PET) imaging 40-60 min after 44.4-229.4 MBq 68Ga-DOTA-TATE administration.Metastases in 31 patients were confirmed by histopathology and in 12 patients by follow-up and other imaging modalities.Twenty-eight of 43 patients finished routine FDG-PET in a week after TATE-PET.PET/CT results were considered positive when the metastatic lesions were tracer-avid.ROI was drawn over each lesion for size and SUV measurement.x2 test and Pearson correlation analysis were used for statistical analysis.Results (1) Of 43 patients,TATE-PET detection rates of metastasis in the liver,lymph nodes,bones.and lungs were 85.7％(30/35),12/13,7/7,2/3,respectively,with their corresponding SUVmax of 18.1(11.3-23.3),10.8(5.4-15.6),7.7(4.2-9.9) and 1.8(1.3-2.3),respectively.Statistical correlation between size and SUVmax was found in metastatic bone lesions(r=0.233,P＜0.05).(2) In 31 patients with histopathologically proven metastasis,TATE-PET detected 23/24 (95.8％) G2,1/2 G1 and 5/5 G3 metastases.G1 metastases were only found in the liver.(3)Among 28 patients underwent both TATE-PET and FDG-PET,there was no significant difference between the detecting rate of metastasis:89.2％ (25/28) vs 71.4％ (20/28);x2 =2.389,P＞0.05.Compared with FDG-PET,TATE-PET was superior in demonstrating metastasis in the liver and bones (70.0％ (14/20) vs 65.0％ (13/20),3/3 vs 2/3),equal in detecting lung metastasis (both 2/3) but inferior in demonstrating metastasis in lymph nodes (9/10vs 10/10).Conclusions The capability of TATE-PET in revealing NEN metastasis varies depending on lesion localization and histologic grade.TATE-PET and FDG-PET are complementary to each other in detection of NEN metastasis,but without obvious relationship to histologic grade.

Objective:To investigate the radiation dosimetry and biodistribution of 68Ga-FAPI-04 PET/CT in patients with hepatobiliary tumor. Methods:A total of six patients with hepatic lesions who underwent PET/CT examination in Peking Union Medical College Hospital were enrolled. After intravenous injection of radiotracer 68Ga-FAPI-04 at (170.57 ± 14.43) MBq, whole-body imaging were performed at the time points of 3, 10, 15, 20, 30 and 60 min, respectively. Biodistribution pattern was observed. Regions of interest were manually delineated. Radiation dosimetry of all target organs were calculated by Olinda/EXM software. Results:The radioactive uptake dissipated gradually in liver whereas it was relatively stable in tumor lesions. The average SUV max of tumor lesions reached the maximum value (13.87± 2.55) at 20 min after injection. The target-to-background ratio increased with time, reaching the maximum value (10.09 ± 8.17) at 30 min after injection. The average effective dose in total body was (0.020 ± 0.002) mSv/MBq and organ with the highest effective dose was bladder wall at (0.146 ± 0.035) mSv/MBq. Conclusions:The effective dose in total body of 68Ga-FAPI-04 was similar to that of 18F-FDG. 68Ga-FAPI-04 is expected to be a PET/CT radiotracer for hepatobiliary tumors in consideration of rapid tumor uptake, low accumulation of liver background, and no influence of blood sugar levels.

Objective:To investigate the segmentation methods of pancreatic ductal adenocarcinoma (PDAC) tumor regions in 18F-fluorodeoxyglucose (FDG) PET/CT images, as well as their impact on radiomic features-based pathological grade prediction. Methods:A total of 72 patients (46 males, 26 females, age range: 25-87 years) with pathologically confirmed PDAC and a preoperative 18F-FDG PET/CT scan in Peking Union Medical College Hospital between September 2010 and January 2016 were enrolled retrospectively. The cohort of patients was classified as well differentiated group and non-well differentiated group based on the pathological grade of PDAC, and patients were divided into training set and validation set in the ratio of 3∶1 randomly. Two physicians performed manual contours in the tumor region (referred as region of interest (ROI)_M1 and ROI_M2) and semi-automatic ROIs based on standardized uptake value (SUV) gradient edge search (referred as ROI_G) and 40% threshold applied to the maximum SUV (SUV max; referred as ROI_S) were drawn. The four types of segmentation results were compared in terms of volume and Dice similarity coefficient (DSC). Shape, first-order, and texture features were extracted from PET/CT original and preprocessed images, and the interclass correlation coefficient (ICC) was used to assess each feature′s consistency across all segmentations. Kruskal-Wallis rank sum test, independent-sample t test or z test were used to analyze the data. The area under the receiver operating characteristic curve was used to assess model accuracy, and cross validation was used to assess generalization ability. Results:There were 55 patients in the training set (14 well differentiated cases and 41 non-well differentiated cases) and 17 patients in the validation set (4 well differentiated cases and 13 non-well differentiated cases). A total of 44 selected features were predictive of the pathological grade of PDAC among 20 feature groups. There was significant difference among the volumes of ROI_M1, ROI_M2, ROI_G and ROI_S (10.29(4.01, 19.43), 9.34(4.26, 17.27), 11.86(5.52, 19.74) and 15.08(9.62, 27.44) cm 3; H=18.641, P<0.05). The degree of contour coincidence and feature consistency between ROI_M1 and ROI_M2 were both higher (DSC=0.86 (0.76, 0.90), ICC=0.86 (0.74, 0.94)). Compared to manual contours, the degree of contour coincidence and feature consistency of ROI_G (DSC: 0.86(0.75, 0.91), 0.91(0.85, 0.96); ICC: 0.87(0.72, 0.94), 0.94(0.88, 0.98)) were better. There was no statistically significant difference in model accuracy or generalization ability between ROI_M1 and ROI_G ( z=1.052, t=0.712, both P>0.05). The accuracy of ROI_M2 was better than ROI_G ( z=3.031, P=0.002), but the generalization ability of ROI_M2 was insufficient ( t=3.086, P=0.012). Conclusions:Although the manual contour prediction models are highly accurate, their performance are unstable. Semi-automatic contouring based on gradient can achieve comparable accuracy to manual contouring, and the model′s generalization ability is stronger.

Objective:To prepare 68Ga-fibroblast activation protein inhibitor (FAPI)-04, and evaluate its biodistribution and imaging characteristics in animals and healthy volunteers, in order to investigate the clinical translation potential. Methods:68Ga-FAPI-04 was synthesized by a manual method and its radiolabeling yield, radiochemical purity, and stability ( in vivo and in vitro) were analyzed. ICR mice ( n=16) were scarified at 5, 30, 60 and 120 min postinjection of 68Ga-FAPI-04 (1.11 MBq) to measure radioactive counts in main organs. The dynamic mircoPET imaging was acquired for 60 min on 3 ICR mice, and tumor imaging capabilities were examined with nude mice bearing HepG2 tumors. Furthermore, 2 healthy volunteers (1 male with age of 64 years, 1 female with age of 56 years) were recruited for the investigation of probe biodistribution in humans. A serial whole-body dynamic PET/CT scan was performed immediately following injection. Results:68Ga-FAPI-04 was synthesized within 20 min with the radiochemical yield of (68.7±4.0)% (decay corrected). The radiochemical purities of 68Ga-FAPI-04 were over 99% and the products were stable for 180 min in vitro and for 90 min in blood. 68Ga-FAPI-04 was mainly cleared through urinary tracts, while other organs only showed mild tracer accumulation. MicroPET imaging showed high uptake of 68Ga-FAPI-04 in the tumor tissue of mice, and the ratio of tumor/liver was 2.14±0.01 (35 min). The PET/CT imaging results of healthy volunteers revealed 68Ga-FAPI-04 could be quickly cleared. Conclusion:68Ga-FAPI-04 has many advantages for PET imaging, such as easy labeling, good stability, quick clearance and low background signals in the liver, which can be used as an attractive PET tracer for detection hepatocellular carcinoma.

Gliomas are the most common primary intracranial tumors in adults, among which high-grade glioma patients are characterized by short survival and poor prognosis. The diagnosis, treatment, evaluation of effective treatments, and prognosis prediction of high-grade gliomas are of great significance for improving patient survival. Conventional enhanced magnetic resonance imaging has deficiencies in delineating tumor extent, identifying tumor progression and treatment-related changes. Therefore, there is a broad consensus to incorporate amino acid PET, and ¹⁸F-FET PET inparticular, into the diagnostic and therapeutic process of high-grade gliomas. In this article, we review the new research progress of ¹⁸F-FET PET in the diagnosis and treatment of adult high-grade glioma in recent years.