PET Tracer Conversion among Brain PET via Variable Augmented Invertible Network

Positron emission tomography (PET) serves as an essential tool for diagnosis of encephalopathy and brain science research. However, it suffers from the limited choice of tracers. Nowadays, with the wide application of PET imaging in neuropsychiatric treatment, 6-18F-fluoro-3, 4-dihydroxy-L-phenylalanine (DOPA) has been found to be more effective than 18F-labeled fluorine-2-deoxyglucose (FDG) in the field. Nevertheless, due to the complexity of its preparation and other limitations, DOPA is far less widely used than FDG. To address this issue, a tracer conversion invertible neural network (TC-INN) for image projection is developed to map FDG images to DOPA images through deep learning. More diagnostic information is obtained by generating PET images from FDG to DOPA. Specifically, the proposed TC-INN consists of two separate phases, one for training traceable data, the other for rebuilding new data. The reference DOPA PET image is used as a learning target for the corresponding network during the training process of tracer conversion. Meanwhile, the invertible network iteratively estimates the resultant DOPA PET data and compares it to the reference DOPA PET data. Notably, the reversible model employs variable enhancement technique to achieve better power generation. Moreover, image registration needs to be performed before training due to the angular deviation of the acquired FDG and DOPA data information. Experimental results exhibited excellent generation capability in mapping between FDG and DOPA, suggesting that PET tracer conversion has great potential in the case of limited tracer applications

[N]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 [ 13 N]ammonia positron emission tomography/computed tomography (PET/CT) in the imaging of PCa. The uptake ratio of [ 13 N]ammonia and the expression of GS in PC3 and DU145 cells was measured. Thirty-four patients with suspected PCa underwent [ 13 N]ammonia PET/CT imaging, and immunohistochemistry staining of GS was performed. The uptake of [ 13 N]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, [ 13 N]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 [ 13 N]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 [ 13 N]ammonia, and [ 13 N]ammonia is a useful tracer for PCa imaging

Role of Fe, Transferrin and Transferrin Receptor in Anti-Tumor Effect of Vitamin C

High-dose vitamin C (VC) exhibits anti-tumor effects, and the cytotoxicity of VC is correlated with oxidative stress. However, iron, as a redox metal, plays an important effect in redox cycling and free radical formation in cells. This study addresses the role of iron ion in the cytotoxicity of VC. We found that iron supplementation increases the anti-tumor effect of VC, which was influenced by the cellular iron uptake pathway&ndash;transferrin (TF)/transferrin receptor (TFR) system. The TFR expression of tumors can be assessed by 68Ga-citrate PET imaging, and it would be helpful to screen out the tumor type which is more sensitive to VC combined with an iron supplementation treatment

De Novo Glutamine Synthesis

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 13 N-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. 13 N-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 13 N-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 13 N-ammoina. Additionally, microPET/computed tomography exhibited that subcutaneous 0.06C6 xenografts had higher 13 N-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. 13 N-ammonia can be a potential metabolic PET tracer for Gln-dependent tumors