Differential diagnosis between cancer and inflammation is a hot issue in medical practice and research. PET metabolic imaging, as a functional imaging modality, demonstrates unique advantages in cancer diagnosis, clinical staging and therapeutic evaluation. In this article, the progress, problems and de?velopment trends about PET metabolic imaging in the differential diagnosis between cancer and inflammation are reviewed.

Objective To investigate the diagnostic efficacy of 13N-NH3 and 18F-FDG PET/CT in the evaluation of untreated gliomas.Methods A total of 45 consecutive patients (29 males,16 females;age range 14-75 years,average age (47.47± 15.64) years) with final diagnosis of glioma from August 2009 to May 2012 were retrospectively analyzed.PET/CT imaging was performed with both 18F-FDG and 13N-NH3.Imaging results were analyzed by tumor-to-gray matter (T/G) ratios.ROC curve analysis was conducted to determine the optimal T/G cutoff values between low-grade and high-grade gliomas.One-way analysis of variance was applied to assess the differential efficacy of the two tracers in different grade of glioma.Results Forty-eight separate lesions were identified (WHO grade Ⅱ,n=16;grade Ⅲ,n=12;and grade Ⅳ,n=20).The sensitivities of 13N-NH3 PET/CT and 18F-FDG PET/CT on predicting high-grade gliomas were 91％(29/32) and 66％ (21/32),respectively.The optimal T/G cutoff values for 18F-FDG and 13N-NH3 were 0.64 and 0.86 with the AUC of 0.910 and 0.943,respectively.The sensitivity and positive predictive value of predicting high-grade gliomas with optimal cutoff values were 84％ (27/32) and 93％ (27/29)for 18F-FDG PET/CT,those for 13N-NH3 PET/CT were 94％ (30/32) and 94％ (30/32),respectively.Conclusion 13N-NH3 PET/CT is superior to 18F-FDG PET/CT not only in separating low-grade gliomas from high-grade ones,but also in the detection of high-grade gliomas for better tumor to normal gray matter contrast.

Objective To analyze the risk factors of hepatocellular carcinoma (HCC) recurrence after liver transplantation based on 18F-FDG PET/CT.Method We respectively analyzed 54 cases of HCC patients who accepted liver transplantation from 2008 September to 2012 November.The clinicopathological features of 54 patients were analyzed by univariate and multivariate analysis to determine the risk factors of HCC recurrence after liver transplantation.The ROC curve was drawn to determine the optimal cutoff value of T/B that affects HCC recurrence after liver transplantation.Result The total incidence of HCC recurrence was 48.1％ (26/54); the disease-free survival (DFS) rate of 0.5 year,1 year and 2 years after transplantation in 54 patients was 92.6％,66.7％,52.2％,49.1 ％ and 49.1％ respectively.The univariate analysis results showed that there were 5 variables to affect HCC recurrence,namely PET imaging,tumor size,tumor number,preoperative AFP level,and tumor degree.On ROC curve analysis,the optimal cutoff value for T/B was 1.69.The multivariate analysis concluded that T/B,and preoperative AFP level were independent factors.Conclusion T/B ＞1.69 and preoperative AFP level ＞400 μg/L are important biological factors of HCC recurrence after liver transplantation.

Objective To compare the efficiency of 18F-FDG PET/CT and contrast enhanced ultrasound (CEUS) in detection of HCC recurrence after surgery or radiofrequency ablation (RFA).Methods Twenty-seven HCC patients (22 males,5 females; average age:47 years) were included in this study,of which 15 patients underwent surgery and 12 patients underwent RFA therapy.18F-FDG PET/CT and CEUS were performed within 2 weeks in all patients to detect recurrence.Final diagnosis was made by pathology or clinical follow-up (＞6 months),and the sensitivity,specificity and accuracy of 18F-FDG PET/CT and CEUS were calculated and compared.McNemar test was used for data analysis.Results Twenty-five patients were diagnosed with HCC recurrence,including 11 cases with extrahepatic metastases.Another 2 patients had extrahepatic metastases without HCC recurrences.The sensitivity,specificity and accuracy in detection of liver lesion with 18F-FDG PET/CT were 92.0％ (23/25),2/2 and 92.6％ (25/27),respectively.While with CEUS,the corresponding values were 60.0％ (15/25),2/2 and 63.0％ (17/27),respectively.In CEUS positive group,the sensitivity and accuracy were 100％(15/15) for both methods.In CEUS negative group,the sensitivity,specificity and accuracy of 18 F-FDG PET/CT in detection of liver lesion were 8/10,2/2 and 83.3％(10/12),respectively.The sensitivity and accuracy of 18F-FDG PET/CT were significantly higher than those of CEUS (0,16.7％(2/12) ; x2 =5.373,5.250,both P＜0.05).Moreover,the sensitivity of 18 F-FDG PET/CT in detecting extrahepatic metastasis was 100％ (13/13).Conclusions 18 F-FDG PET/CT is more sensitive and accurate than CEUS (especially in CEUS negative cases) in detecting recurrence of HCC after surgery or RFA.18F-FDG PET/CT also could be useful for detection of extrahepatic metastasis.

Objective To investigate the expression of glutamine synthetase ( GS ) in prostate cancer and the utility of 13 N?NH3 PET/CT in detecting prostate cancer. Methods The uptake ratio of 13 N?NH3 and the expression of GS in PC3 and DU145 cells were measured by Western blot and PCR methods. A total of 34 patients with suspected prostate cancer underwent 13 N?NH3 PET/CT imaging and prostate biopsy. Immunohistochemistry staining of GS was performed and Gleason scores of tumors were evaluated. One?way analysis of variance, the least significant difference?t test and Spearman correlation analysis were used to an?alyze data. Results The uptake of 13 N?ammonia in PC3 and DU145 cells elevated along with the decrease of glutamine in medium. The expression of GS mRNA and protein also increased when glutamine was de?creased. In biopsy samples, the mean GS expression scores of prostate cancer, benign prostatic hyperplasia (BPH) and prostatitis were 7.76±2.57, 3.98±2.60, 3.34±0.36, respectively (F=36.85, t1=7.97, t2=4?45, all P<0.05), which had a weak correlation with Gleason scores (rs=0.52, P<0.05). In 34 patients, the mean SUVmax of prostate cancer segments (1.56±0.58 and 1.14±0.22;F=5.966, t1=2.63, t2=2.65, all P<0.05). There was a weak correlation between GS expression scores and the uptake of 13 N?ammonia in prostate cancer (rs=0.47, P<0.05). Conclusions Up?regulated expression of GS is common in prostate cancer cells. GS is the main reason for the uptake of 13 N?ammonia, which is a useful tracer for prostate cancer imaging.

Objective To explore the value of 18F-FDG PET/CT in predicting tumor recurrence for hepatocellular carcinoma (HCC) after liver transplantation (LT).Method We respectively analyzed 52 patients with HCC who underwent the 18F-FDG PET/CT examination before LT.In terms of tumor recurrence,all patients were divided into recurrence group and non-recurrence group.According to the degree of 18F-FDG uptake,all patients were divided into PET(-) group and PET (+) group.The SUVmax of primary tumor/the SUVmax of normal-liver background (T/B) was calculated by 18F FDG PET/CT.All patients were then divided into T/B≤1.15 group and T/B＞1.15 group.Result During the follow-up period,25 out of 52 patients (48.1％) developed posttransplant HCC recurrence and 27 (51.9％) had no recurrence.T/B of patients with recurrence (2.51 ± 0.95) was significantly higher than that of patients with non-recurrence (1.37 ± 0.46),t =4.12,P＜0.001.The disease-free survival rate of 0.5 year,1 year,2 years and 3 years after LT in PET(-) group and PET(+) group was 100.0％,92.3％,92.3％ and 92.3％,and 89.7％,59.0％,43.6％ and 35.7％ respectively.Log-rank test revealed that disease-free survival rate in PET(-) group was significantly higher than that in PET(+) group,x2 =17.8,P=0.003.The disease-free survival rate of 0.5 year,1 year,2 years and 3 years after LT in T/B≤1.15 group and T/B＞1.15 group was 100.0％,92.3％,92.3％ and 92.3％,and 89.5％,59.7％,42.1％ and 33.7％ respectively.Log-rank test showed that disease-free survival rate of T/B≤1.15 group was significantly higher than that of T/B＞1.15 group,x2 =10.24,P =0.001.Conclusion 18F-FDG PET/CT can predict HCC recurrence after LT.PET(-)and T/B≤1.15 of the 18F-FDG PET/CT in patients with HCC after LT were associated with a good prognosis,and PET(+) and T/B＞1.15 of the 18F-FDG PET/CT in patients with HCC after LT with a poor prognosis.

Objective To evaluate the biodistribution and radiation-absorbed doses of main organs in healthy people with 13 N-ammonia.Methods Five healthy volunteers underwent whole-body PET and CT scans after injection of 666-814 MBq of 13 N-ammonia.The serial dynamic emission images of each healthy volunteer were acquired.ROI were drawn manually based on the transverse CT images and transferred to the corresponding PET slices.Radiation-absorbed doses were calculated using the medical internal radiation dosimetry (MIRD) method.Results The highest concentrations of 13 N-ammonia were found in the heart,liver and kidneys,followed by pancreas,brain,spleen and stomach.The organ of highest absorbed dose was heart with (7.14±3.63) × 10-3 mGy/MBq.The whole-body absorbed dose was (2.11±0.44) × 10 3 mGy/MBq.The whole-body effective dose was (6.58± 1.23) × 10-3 mSv/MBq.Conclusion As one of the most important myocardial perfusion tracers,the whole-body 13 N-NH3 · H2 O PET appears to be safe for humans.

Objective:To explore the application of OTSU-based self-attenuation correction PET (sacPET) reconstruction technology in 18F-florbetapir (AV45) imaging. Methods:From November 2018 to December 2019, 7 confirmed Alzheimer′s disease (AD) patients (4 males, 3 females, age (69.6±4.5)years) and 3 healthy controls (HC; 1 male, 2 females, age (68.0±4.6) years) were recruited prospectively for 18F-AV45 PET imaging in the First Affiliated Hospital of Sun Yat-Sen University. Original data collected by PET acquisition was processed with sacPET reconstruction and then compared with standard PET images by visual analysis and semi-quantitative analysis. Fisher exact test, Kappa test and Pearson correlation analysis were used to analyze data. Results:In HC group and AD group, the radioactive distribution showed by sacPET images and that by standard PET images were similar, and the contrast of gray-white matter in sacPET images was weaker than that in standard PET images. Moreover, the positive uptake area of the cortex in the AD group was smaller than that in standard PET images. Visual analysis showed 19 positive regions in sacPET images and 22 in standard PET images, with no statistical difference of positive rates of the sub-regions in the cortex between the two PET images (all P>0.05), and the overall consistency of 88.00% (44/50; Kappa=0.75 (95% CI: 0.57-0.94), P<0.05). Semi-quantitative analysis showed that the standardized uptake value ratio (SUVR) of frontal lobe and cingulate gyrus measured by sacPET was lower than that measured by standard PET (0.93±0.06 vs 0.96±0.06 and 0.99±0.04 vs 1.01±0.04; t values: 5.30 and 5.10, both P<0.01), while SUVR of parietal lobe, temporal lobe and occipital lobe measured by sacPET was higher than that measured by standard PET (0.78±0.08 vs 0.68±0.07, 0.97±0.07 vs 0.91±0.08 and 0.94±0.11 vs 0.71±0.12; t values: 6.27, 7.36 and 16.90, all P<0.01). The overall SUVR of sacPET images was significantly correlated with the standard PET images ( r=0.75, P<0.001). Conclusion:For 18F-AV45 imaging, sacPET reconstruction technology can obtain reliable and effective PET images without CT data, but its accuracy and precision still need to be improved.

Objective:To explore the relationship between vesicular monoamine transporter 2(VMAT2) density in the striatum and the non-motor symptoms(NMSs) in patients with Parkinson′s disease(PD).Methods:From December 2018 to December 2019, 29 normal controls (16 males, 13 females, age: (48.8±14.2) years), 31 patients with PD at the Hoehn-Yahr (mH-Y) Ⅱ stage (16 males, 15 females, age: (53.4±8.5) years) and 36 patients with PD at mH-Y Ⅲ stage (19 males, 17 females, age: (63.1±8.2) years) in the First Affiliated Hospital of Sun Yat-sen University were prospectively enrolled in this study. All subjects underwent 18F-fluoropropyl-(+ )-dihydrotetrabenazine( 18F-FP-(+ )-DTBZ, 18F-AV133) PET/CT imaging, then the specific uptake ratios (SURs) of striatal subregions were measured with the occipital cortex as the reference background region. The clinical data, laboratory data and imaging results were collected. The NMSs of each patient were evaluated with Hamilton Anxiety Rating Scale (HAMA), Hamilton Depression Rating Scale (HAMD), Parkinson′s Disease Sleep Scale (PDSS), Montreal Cognitive Assessment (MoCA), Parkinson′s Disease Quality of Life Questionnaire (PDQL) and Non-Motor Symptoms Scale (NMSS). The independent-sample t test and one-way analysis of variance (the least significant difference t test) were used to compare data differences. Finally, the association of the striatal SURs with the clinical symptom scores were evaluated with Pearson correlation analysis and multivariable stepwise regression analysis. Results:Significant differences were found in depression (3.51±1.34 vs 11.36±3.87), anxiety (2.35±1.45 vs 6.00±3.32), sleep disorder (132.90±12.26 vs 110.34±19.69) and life quality (7.58±3.37 vs 24.01±10.15) scores between the mH-Y stage Ⅱ and the stage Ⅲ patients ( t values: from -10.573 to 5.439, all P<0.05), while cognitive scores did not differ significantly between the 2 PD groups ( t=1.067, P>0.05). Compared with healthy control group (1.28±0.22), the PD groups displayed a more marked decrease of SURs in the bilateral putamen and in the caudate nucleus (0.65±0.16 and 0.31±0.14; F=83.11, P<0.05), and the SURs of patients at stage Ⅱ were higher than those of the patients at stage Ⅲ ( t=9.116, P<0.05). NMSs scores of PD patients, with the exception of cognition scores, were correlated with striatal SURs ( r values: from -0.647 to -0.426, all P<0.05). Regression analysis showed that total striatum SURs was the best predictor of PDSS and NMSS scores ( R2 values: 0.234, 0.378, both P<0.001), while contralateral caudate nucleus SURs were best predictor of HAMD scores ( R2=0.402, P<0.001). The SURs of contralateral putamen were best variables for predicting HAMA scores ( R2=0.204, P<0.001). Conclusion:The correlation between the decreased striatal VMAT2 and a broad spectrum of NMSs in patients with PD is established, suggesting that the defect in dopamine supply may be an early abnormality promoting mechanisms leading to the development of NMSs in PD.

Dynamic ~(13)N-NH_3 positron emission tomography (PET) imaging was performed in 8 normal subjects and 6 cases of hypopituitarism. The pituitary images were small and delayed, and blood perfusion and radioactive uptake were decreased in hypopituitarism. ~(13)N-NH_3 PET imaging shows diagnostic value in hypopituitarism.