Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography

Charged lepton system symmetry under combined charge, parity, and time-reversal transformation (CPT) remains scarcely tested. Despite stringent quantum-electrodynamic limits, discrepancies in predictions for the electron–positron bound state (positronium atom) motivate further investigation, including fundamental symmetry tests. While CPT noninvariance effects could be manifested in non-vanishing angular correlations between final-state photons and spin of annihilating positronium, measurements were previously limited by knowledge of the latter. Here, we demonstrate tomographic reconstruction techniques applied to three-photon annihilations of ortho-positronium atoms to estimate their spin polarisation without magnetic field or polarised positronium source. We use a plastic-scintillator-based positron-emission-tomography scanner to record ortho-positronium (o-Ps) annihilations with single-event estimation of o-Ps spin and determine the complete spectrum of an angular correlation operator sensitive to CPT-violating effects. We find no violation at the precision level of 10−4, with an over threefold improvement on the previous measurement.

The role of endoplasmic reticulum in in vivo cancer FDG kinetics

A recent result obtained by means of an in vitro experiment with cancer cultured cells has configured the endoplasmic reticulum as the preferential site for the accumulation of 2-deoxy-2-[18F]fluoro-D-glucose (FDG). Such a result is coherent with cell biochemistry and is made more significant by the fact that the reticular accumulation rate of FDG is dependent upon extracellular glucose availability. The objective of the present paper is to confirm in vivo the result obtained in vitro concerning the crucial role played by the endoplasmic reticulum in FDG cancer metabolism. This study utilizes data acquired by means of a Positron Emission Tomography scanner for small animals in the case of CT26 models of cancer tissues. The recorded concentration images are interpreted within the framework of a three-compartment model for FDG kinetics, which explicitly assumes that the endoplasmic reticulum is the dephosphorylation site for FDG in cancer cells. The numerical reduction of the compartmental model is performed by means of a regularized Gauss-Newton algorithm for numerical optimization. This analysis shows that the proposed three-compartment model equals the performance of a standard Sokoloff’s two-compartment system in fitting the data. However, it provides estimates of some of the parameters, such as the phosphorylation rate of FDG, more consistent with prior biochemical information. These results are made more solid from a computational viewpoint by proving the identifiability and by performing a sensitivity analysis of the proposed compartment model.

Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography

Charged lepton system symmetry under combined charge, parity, and time-reversal transformation (CPT) remains scarcely tested. Despite stringent quantum-electrodynamic limits, discrepancies in predictions for the electron–positron bound state (positronium atom) motivate further investigation, including fundamental symmetry tests. While CPT noninvariance effects could be manifested in non-vanishing angular correlations between final-state photons and spin of annihilating positronium, measurements were previously limited by knowledge of the latter. Here, we demonstrate tomographic reconstruction techniques applied to three-photon annihilations of ortho-positronium atoms to estimate their spin polarisation without magnetic field or polarised positronium source. We use a plastic-scintillator-based positron-emission-tomography scanner as a high-acceptance photon detector to study CPT-prohibited angular correlation in ortho-positronium (o-Ps) annihilations. We record an unprecedented range of kinematical configurations of o-Ps annihilations into three photons. Tomographic reconstruction of the annihilation points in a large medium allows single-event estimation of positronium spin orientation and, consequently, determination of the complete spectrum of angular correlation between the annihilation plane orientation and positronium spin, the non-vanishing expectation value of which would manifest CPT-violating effects. We find no violation at the precision level of 10^{−4}, with a fourfold improvement on the previous measurement. This work enables application of positronium-imaging techniques to study discrete symmetries in positronium decays.

Multiple Synchronous Squamous Cell Cancers of the Skin and Esophagus: Differential Management of Primary Versus Secondary Tumor

Multiple primary tumors are uncommon in patients with squamous cell esophageal cancer. Conventional imaging methods have limitations in detecting those tumors. Although 18-F-fluoro-deoxyglucose-positron emission tomography scanner increases the detection of multiple synchronous tumors in patients with other malignancies, its contribution in patients with squamous cell esophageal cancer has not been assessed as it is not systematically performed. The detection of synchronous skin squamous cell tumors in patients with squamous cell esophageal cancer presents a challenge for making diagnostic and therapeutic decisions. A metastatic tumor leads to palliative management, whereas the diagnosis of a primary skin tumor requires curative treatment of both squamous cell tumors. Pathological evaluation appears crucial in the decision.

Curative Effects for B-Cell Lymphoma Accomplished by Direct-Acting Antiviral Agents of Hepatitis C

Hepatitis C virus (HCV) is a hepatotropic and lymphotropic virus with the capabilities of tumorigenesis. We present an HCV-infected patient affected with B-cell lymphomas after suffering from hepatocellular carcinoma. The patient exhibited curative effects for lymphomas after treatment with sofosbuvir and ledipasvir, which is shown clearly with a positron emission tomography scanner.