Xiangsong Zhang

The combination of 13N-ammonia and 18F-FDG in predicting primary central nervous system lymphomas in immunocompetent patients.

Objective Accurate identification of primary central nervous system lymphoma (PCNSL) and its differentiation from other brain tumors remain difficult but are essential for treatment. In this study, we investigated whether 13N-ammonia combined with 18F-FDG could distinguish PCNSL from solid gliomas effectively. Methods Ten consecutive patients with final diagnosis of PCNSL (5 female and 5 male patients; mean [SD] age, 59.10 [12.47] years; range, 43–74 years) and another fifteen consecutive patients with solid glioma lesions (5 female and 10 male patients; mean [SD] age, 46.73 [19.61] years; range, 14–72 years) were included in this study. PET/CT imaging was performed for all of them with both 18F-FDG and 13N-ammonia as tracers. Tumor-to-gray matter (T/G) ratios were calculated for the evaluation of tumor uptake. Both Student t test and discriminant analysis were recruited to assess the differential efficacy of these 2 tracers. Results The T/G ratios of 18F-FDG in PCNSL lesions were higher than in solid gliomas (3.26 [1.18] vs 1.56 [0.41], P < 0.001), whereas the T/G ratios of 13N-ammonia in PCNSL lesions were lower than in solid gliomas significantly (1.38 [0.20] vs 2.11 [0.69], P < 0.001). All the lesions of PCNSL displayed higher T/G ratios of 18F-FDG than 13N-ammonia, whereas 14 (77.8%) of 18 glioma lesions showed contrary results. Tumor classification by means of canonical discriminant analysis yielded an overall accuracy of 96.9%, and only one glioma lesion was misclassified into the PCNSL group. Conclusions PCNSLs and solid gliomas have different metabolic profiles on 13N-ammonia and 18F-FDG imaging. The combination of these 2 tracers can distinguish these 2 clinical entities effectively and make an accurate prediction of PCNSL.

13N-ammonia combined with 18F-FDG could discriminate between necrotic high-grade gliomas and brain abscess.

Purpose Accurate prediction of brain abscess is beneficial for timely management. In this study, we investigated the utility of 13N-ammonia and its combination with 18F-FDG in differentiating brain abscess from necrotic high-grade gliomas. Patients and Methods Thirteen patients with ring-like enhancement high-grade gliomas and 11 patients with brain abscess were recruited in our study. All of them underwent both 18F-FDG and 13N-ammonia PET imaging. Lesion uptake was evaluated by lesion to normal gray matter ratio (L/N). Histopathology diagnosis was obtained for all the patients after PET imaging. Results The L/N values of 18F-FDG were not significantly different between brain abscess and necrotic high-grade gliomas (P = 0.35). The uptake of 13N-ammonia in gliomas was higher than that in abscess lesions (L/N: 1.38 ± 0.31 vs 0.84 ± 0.18, P < 0.001). The receiver operating characteristic curve analysis determined the optimal L/N cutoff value (13N-ammonia) of 1.0 with the area under the curve of 0.94 and the overall accuracy of 87.5%. Discriminant analysis demonstrated that the combination of 18F-FDG and 13N-ammonia could distinguish the 2 clinical entities with higher accuracy of 95%, and only 1 necrotic glioma lesion was misclassified into the abscess group. Conclusions 13N-ammonia is effective in distinguishing brain abscess from necrotic high-grade gliomas, and its combination with 18F-FDG could further elevate the diagnostic accuracy.

Hepatic tuberculosis mimics metastasis revealed by 18F-FDG PET/CT.

Extrapulmonary tuberculosis can affect almost any organ in the body. Here, we report a rare case of primary hepatic tuberculosis presented as multiple hepatic lesions and enlarged lymph nodes in the retroperitoneum and porta hepatis. PET/CT imaging showed avid FDG uptake by these lesions but did not find any definite primary malignancy. Finally, a diagnosis of primary hepatic tuberculosis was made with histopathologic examination.

The comparison of 13N-ammonia and 18F-FDG in the evaluation of untreated gliomas.

Objective Noninvasive evaluation of glioma is of great help for clinical practice. In this study, we investigated the utility of 13N-ammonia in the evaluation of untreated gliomas and compared the results with that of 18F-FDG. Methods Forty-five consecutive patients with final diagnosis of glioma were included in this study. PET/CT imaging was performed for all of them with both 18F-FDG and 13N-ammonia as tracers. Imaging results were analyzed by tumor-to-gray matter (T/G) ratios. Receiver operating characteristic curve analysis was conducted to determine the optimal T/G cutoff values of each tracer between low-grade and high-grade gliomas. Results Forty-eight separate lesions were identified in all (grade II, n = 16; grade III, n = 12; and grade IV, n = 20). Twenty-nine out of 32 high-grade lesions (91%) showed higher uptakes than normal gray matter with 13N-ammonia in comparison with the result of 21 lesions (66%) with 18F-FDG. The optimal T/G cutoff values for 18F-FDG and 13N-ammonia were 0.64 and 0.86 separately with the area under each curve 0.910 and 0.943. The sensitivity and specificity of predicting high-grade gliomas with optimal cutoff values were 83% and 93% for 18F-FDG and 94% and 94% for 13N-ammonia, respectively. Conclusion 13N-Ammonia is superior to 18F-FDG 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.

Human radiation dose estimation of (11)C-CFT using whole-body PET.

Purpose 11C-Labeled 2-&bgr;-carbomethoxy-3-&bgr;-(4-fluorophenyl)tropane (11C-CFT) is a commonly used positron emission tomography (PET) tracer for dopamine transporters imaging. The present study estimated human radiation absorbed doses of 11C-CFT based on whole-body PET imaging in healthy subjects. Methods Whole-body PET was performed on 6 subjects after injection of 472.06 ± 116.47 MBq of 11C-CFT. 7 Frames were acquired for about 70 min in 7 segments of the body. Regions of interest were drawn on PET images of source organs. Residence time was calculated as the area under the time-activity curve. Radiation dosimetry was calculated from organ residence time using the medical internal radiation dosimetry (MIDR) method. Results The organs with the highest radiation-absorbed doses were the urinary bladder, followed the spleen, pancreas, kidneys, and stomach. The dose-limiting critical organ was the urinary bladder. The effective dose was 8.89E−03 mSv/MBq (22.9 mrem/mCi). Biexponential fitting of mean bladder activity demonstrated that 18% of activity was excreted via the urine. Conclusions The potential radiation risks of 11C-CFT associated with in this study are well within accepted limits. 11C-CFT demonstrates a favorable radiation dose profile in humans and allows multiple PET examinations on the same subject per year.

A child with Burkitt lymphoma with pleural, peritoneal, mesenteric, omental, and renal involvement: diagnostics by FDG PET/CT.

A 7-year-old boy presented with increasing abdominal girth and abdominal pain. Abdominal ultrasound revealed a pleural effusion and ascites. Computed tomography (CT) demonstrated a mass involving the peritoneum, mesentery, and omentum with marked ascites, mesenteric nodules, and renal involvement. Positron emission tomography (PET)/CT scan identified additional tumor within the pleura. PET/CT imaging was helpful in identifying the appropriate pleural mass biopsy site in this patient with Burkitt lymphoma.

18F-Labeled NaF PET-CT in Detection of Bone Metastases in Patients With Preoperative Lung Cancer

AbstractWe compared the diagnostic accuracy of 18F-labeled sodium fluoride (18F-NaF) PET-CT with 99m-technetium methylene diphosphonate (99mTc-MDP) single photon emission computed tomography (SPECT) to detect bone metastases (BMs) in patients with preoperative lung cancer.Patients with lung cancer (n = 181) were examined with 18F-NaF PET-CT, and another 167 patients with lung cancer were examined with 99mTc-MDP SPECT. 18F-NaF PET-CT and 99mTc-MDP SPECT were evaluated by 2 experienced readers. Lesions were graded on a scale of 0 (degenerative lesion) to 4 (definite BM), and equivocal lesions were determined as indifferent (grade 3).Based on patient-based analysis, there were only 4 equivocal patients in 18F-NaF PET-CT detection. However, in 99mTc-MDP SPECT detection, there were 19 equivocal patients, which indicated a significant difference in terms of occurrence ratio (&khgr;2 = 9.005, P = 0.03). Sensitivity and specificity of PET-CT was significantly better than that of SPECT when equivocal reading was categorized as malignant or benign (P < 0.05). Based on lesions-based analysis, SPECT produced 26 equivocal lesions of 333 lesions, but PET-CT produced only 5 equivocal lesions of 991 lesions. PET-CT was significantly better than SPECT in the aspect of producing equivocal patients (&khgr;2 = 58.141, P < 0.001). Sensitivity and specificity of PET-CT was significantly better than that of SPECT when equivocal reading was categorized as malignant or benign (P < 0.05).18F-NaF PET-CT is a highly sensitive and specific modality for the detection of BM in patients with preoperative lung cancer. It is better than conventional 99mTc-MDP SPECT in detecting BM in patients with preoperative lung cancer.

18F-FDG PET/CT Findings in Multicentric Reticulohistiocytosis.

Multicentric reticulohistiocytosis is a rare systemic inflammatory disease of unknown etiology characterized by the infiltration of histiocytes and multinucleated giant cells into multiple systems. The definitive diagnosis depends on biopsy of the affected tissues. Here, we report the F-FDG PET/CT findings of a 62-year-old man with multicentric reticulohistiocytosis. Increased FDG uptake was observed in cutaneomucosal papules, surrounding tissues of many joints, multiple muscles, and lymph nodes.

[¹³N]Ammonia positron emission tomographic/computed tomographic imaging targeting glutamine synthetase expression in prostate cancer.

The purpose of this study was to investigate the expression of glutamine synthetase (GS) in prostate cancer (PCa) and the utility of [13N]ammonia positron emission tomography/computed tomography (PET/CT) in the imaging of PCa. The uptake ratio of [13N]ammonia and the expression of GS in PC3 and DU145 cells was measured. Thirty-four patients with suspected PCa underwent [13N]ammonia PET/CT imaging, and immunohistochemistry staining of GS was performed. The uptake of [13N]ammonia in PC3 and DU145 cells elevated along with the decrease in glutamine in medium. The expression of GS messenger ribonucleic acid and protein also increased when glutamine was deprived. In biopsy samples, the GS expression scores were significantly higher in PCa tissue than in benign tissues (p < .001), and there was a positive correlation between the maximum GS expression scores and Gleason scores (Spearman r = .52). In 34 patients, [13N]ammonia uptake in PCa segments was significantly higher than that in benign segments (p ≤ .01), and there was a weak correlation between GS expression scores and the uptake of [13N]ammonia (Spearman r = .47). The expression of GS in PCa cells upregulated along with the deprivation of glutamine. GS is the main reason for the uptake of [13N]ammonia, and [13N]ammonia is a useful tracer for PCa imaging.The purpose of this study was to investigate the expression of glutamine synthetase (GS) in prostate cancer (PCa) and the utility of [¹³N]ammonia positron emission tomography/computed tomography (PET/CT) in the imaging of PCa. The uptake ratio of [¹³N]ammonia and the expression of GS in PC3 and DU145 cells was measured. Thirty-four patients with suspected PCa underwent [¹³N]ammonia PET/CT imaging, and immunohistochemistry staining of GS was performed. The uptake of [¹³N]ammonia in PC3 and DU145 cells elevated along with the decrease in glutamine in medium. The expression of GS messenger ribonucleic acid and protein also increased when glutamine was deprived. In biopsy samples, the GS expression scores were significantly higher in PCa tissue than in benign tissues (p < .001), and there was a positive correlation between the maximum GS expression scores and Gleason scores (Spearman r  =  .52). In 34 patients, [¹³N]ammonia uptake in PCa segments was significantly higher than that in benign segments (p ≤ .01), and there was a weak correlation between GS expression scores and the uptake of [¹³N]ammonia (Spearman r  =  .47). The expression of GS in PCa cells upregulated along with the deprivation of glutamine. GS is the main reason for the uptake of [¹³N]ammonia, and [¹³N]ammonia is a useful tracer for PCa imaging.

De Novo Glutamine Synthesis Importance for the Proliferation of Glioma Cells and Potentials for Its Detection With 13N-Ammonia

Purpose: The aim of this study was to investigate the role of de novo glutamine (Gln) synthesis in the proliferation of C6 glioma cells and its detection with 13N-ammonia. Methods: Chronic Gln-deprived C6 glioma (0.06C6) cells were established. The proliferation rates of C6 and 0.06C6 cells were measured under the conditions of Gln deprivation along with or without the addition of ammonia or glutamine synthetase (GS) inhibitor. 13N-ammonia uptake was assessed in C6 cells by gamma counting and in rats with C6 and 0.06C6 xenografts by micro–positron emission tomography (PET) scanning. The expression of GS in C6 cells and xenografts was assessed by Western blotting and immunohistochemistry, respectively. Results: The Gln-deprived C6 cells showed decreased proliferation ability but had a significant increase in GS expression. Furthermore, we found that low concentration of ammonia was sufficient to maintain the proliferation of Gln-deprived C6 cells, and 13N-ammonia uptake in C6 cells showed Gln-dependent decrease, whereas inhibition of GS markedly reduced the proliferation of C6 cells as well as the uptake of 13N-ammoina. Additionally, microPET/computed tomography exhibited that subcutaneous 0.06C6 xenografts had higher 13N-ammonia uptake and GS expression in contrast to C6 xenografts. Conclusion: De novo Gln synthesis through ammonia–glutamate reaction plays an important role in the proliferation of C6 cells. 13N-ammonia can be a potential metabolic PET tracer for Gln-dependent tumors.