Haiqun Xing

Brown Adipose Tissue Can Be Activated or Inhibited within an Hour before 18F-FDG Injection: A Preliminary Study with MicroPET

Brown adipose tissue (BAT) is emerging as a potential target for treating human obesity. It has been indicated that BAT is rich in innervations of sympathetic nerve control. Using 18F-FDG microPET imaging, this study aims at evaluating how factors related to sympathetic activation/inhibition changed BAT metabolism of mice. BAT 18F-FDG uptake were semiquantitatively evaluated in different groups of mice under temperature (cold or warm stimulus) or pharmacological interventions (norepinephrine, epinephrine, isoprenaline, or propranolol) and were compared with the corresponding controls. It was found that BAT activation can be stimulated by cold exposure (P = 1.96 × 10−4), norepinephrine (P = .002), or both (P = 2.19 × 10−6) within an hour before 18F-FDG injection and can also be alleviated by warming up (P = .001) or propranolol lavage (P = .027). This preliminary study indicated that BAT function could be evaluated by 18F-FDG PET imaging through short-term interventions, which paved the way for further investigation of the relationship between human obesity and BAT dysfunction.

68Ga DOTATATE PET/CT is an Accurate Imaging Modality in the Detection of Culprit Tumors Causing Osteomalacia.

Objectives Tumor-induced osteomalacia (TIO) is generally caused by small benign mesenchymal tumors producing fibroblast growth factor-23 (FGF-23). The only curative therapy of the disease is resection of the causative tumors. However, these tumors are extremely difficult to detect using conventional imaging modalities. This research was undertaken to evaluate efficacy of 68Ga DOTATATE PET/CT in this clinical setting. Methods Images of 68Ga DOTATATE PET/CT and clinical charts from 54 patients with clinically suspected TIO were retrospectively reviewed. The image findings were compared with the results of histopathological examinations and clinical follow-ups. Results 68Ga DOTATATE PET/CT scans were positive in 44 patients, among which, 33 had surgery to remove the lesions. Postsurgical pathological examination confirmed causative tumors in 32 patients whose symptoms diminished promptly, and the serum phosphate levels became normal, which confirmed the diagnoses of TIO. Eleven patients with positive 68Ga DOTATATE PET/CT did not have surgery. These 11 patients continued to have symptoms and hypophosphatemia but were not included in the final analysis because of lack of evidence to confirm or exclude TIO. Ten patients had negative 68Ga DOTATATE PET/CT scans. All of these10 patients responded to conservative therapy and had normal serum phosphate levels in the follow-up, which excluded TIO. Therefore, the 68Ga DOTATATE PET/CT imaging had a sensitivity of 100% (32/32) and a specificity of 90.9% (10/11). The overall accuracy of 68Ga DOTATATE PET/CT scan in the detection of tumors responsible for osteomalacia is 97.7% (42/43). Conclusions 68Ga DOTATATE PET/CT scan is an accurate imaging modality in the detection of tumors causing TIO.

Infection Imaging With 18F-FDS and First-in-Human Evaluation

PURPOSE The noninvasive imaging of bacterial infections is critical in order to reduce mortality and morbidity caused by these diseases. The recently reported (18)F-FDS ((18)F-2-fluorodeoxy sorbitol) as a PET (positron emission tomography) tracer can be used to image Enterobacteriaceae-specific infections and provides a potential alternative to this problem compared with other probes for imaging infections. In this study, automatic synthesis, validation of (18)F-FDS and a first-in-human study were performed and discussed. METHODS A multifunctional synthesis module was employed for the radiosynthesis of (18)F-FDG ((18)F-2-fluorodeoxy glucose) and (18)F-FDS starting from (18)F ion using two-pot three-step fully automated reactions. The behavior of (18)F-FDS as an in vivo imaging probe for infections was evaluated in an Escherichia coli mouse infection model. The first detailed pharmacokinetic and biodistribution parameters were obtained from healthy human volunteers. RESULTS The uptake of (18)F-FDS in an E. coli mouse-myositis infection model was easily differentiated from other organs and normal muscle. Intensive lesion uptake declined after antibiotic treatment. In the pilot human study, no adverse effects due to (18)F-FDS were observed up to 24 h post-injection. The radiotracer was rapidly cleared from the circulation and excreted mainly through the urinary system. CONCLUSION We conclude that (18)F-FDS PET holds great potential for appropriate and effective for the imaging of bacterial infections in vivo. These preliminary results indicate that further clinical studies are warranted.

Application of dual phase imaging of 11C-acetate positron emission tomography on differential diagnosis of small hepatic lesions.

Objective Previously we observed that dual phase 11C-acetate positron emission tomography (AC-PET) could be employed for differential diagnosis of liver malignancies. In this study, we prospectively evaluated the effect of dual phase AC-PET on differential diagnosis of primary hepatic lesions of 1–3 cm in size. Methods 33 patients having primary hepatic lesions with size of 1–3 cm in diameter undertook dual phase AC-PET scans. Procedure included an early upper-abdomen scan immediately after tracer injection and a conventional scan in 11–18 min. The standardized uptake value (SUV) was calculated for tumor (SUVT) and normal tissue (SUVB), from which 11C-acetate uptake ratio (as lesion against normal liver tissue, SUVT/SUVB) in early imaging (R1), conventional imaging (R2), and variance between R2 and R1 (ΔR) were derived. Diagnoses based on AC-PET data and histology were compared. Statistical analysis was performed with SPSS 19.0. Results 20 patients were found to have HCC and 13 patients had benign tumors. Using ΔR>0 as criterion for malignancy, the accuracy and specificity were significantly increased comparing with conventional method. The area under ROC curve (AUC) for R1, R2, and ΔR were 0.417, 0.683 and 0.831 respectively. Differential diagnosis between well-differentiated HCCs and benign lesions of FNHs and hemangiomas achieved 100% correct. Strong positive correlation was also found between R1 and R2 in HCC (r2 = 0.55, P<0.001). Conclusions Dual phase AC-PET scan is a useful procedure for differential diagnosis of well-differentiated hepatocellular carcinoma and benign lesions. The dynamic changes of 11C-acetate uptake in dual phase imaging provided key information for final diagnosis.

99mTc-HYNIC-TOC imaging in the evaluation of pancreatic masses which are potential neuroendocrine tumors.

Purpose The aim of this investigation was to determine the accuracy of the findings and the diagnoses of 99mTc-hydrazinonicotinyl-Tyr3-octreotide scan (99mTc-HYNIC-TOC imaging) in patients with pancreatic masses which were potential neuroendocrine tumors. Methods Records of total 20 patients with pancreatic masses were retrospectively reviewed. All of the patients had been revealed by abdominal contrast CT and possibility of neuroendocrine tumors could not be excluded by CT imaging before 99mTc-HYNIC-TOC imaging. 99mTc-HYNIC-TOC imaging was performed at 1 and 4 hours post-tracer injection, and SPECT/CT images of the abdomen were also acquired. The image findings were compared to final diagnoses which were made from pathological examination. Results Among all 20 pancreatic masses evaluated, there were 16 malignant lesions which included 1 ductal adenocarcinoma and 15 neuroendocrine tumors. 99mTc-HYNIC-TOC imaging identified 14 of 15 pancreatic neuroendocrine tumors and excluded 4 of 5 lesions which were not neuroendocrine tumors. The overall sensitivity, specificity, and accuracy was therefore 93.3% (14 of 15), 80% (4 of 5), and 90.0% (18 of 20), respectively, in our patient population. Conclusion 99mTc-HYNIC-TOC imaging provides reasonable accuracy in the evaluation pancreatic mass suspected to be neuroendocrine tumors.

Focal Autoimmune Pancreatitis Mimicking Pancreatic Cancer on FDG PET/CT Imaging

Autoimmune pancreatitis generally results in diffuse increased FDG activity throughout the pancreas on PET/CT images. We present a case of focal autoimmune pancreatitis with abnormal FDG activity involving only the pancreatic tail on PET/CT in a 61-year-old man who was provisionally diagnosed as having pancreatic cancer based on the CT findings. The diagnosis of autoimmune pancreatitis was based on pathological examination and elevated serum immunoglobulin G4 level. Following the steroid therapy, the patient was gradually recovered.