18F-fluoro-deoxy-glucose focal uptake in very small pulmonary nodules: fact or artifact? Case reports

ABSTRACT: BACKGROUND: F-fluoro-deoxy-glucose (18F-FDG) positron emission tomography integrated/combined with computed tomography (PET-CT) provides the best diagnostic results in the metabolic characterization of undetermined solid pulmonary nodules. The diagnostic performance of 18F-FDG is similar for nodules measuring at least 1 cm and for larger masses, but few data exist for nodules smaller than 1 cm. CASE PRESENTATION: We report five cases of oncologic patients showing focal lung 18F-FDG uptake on PET-CT in nodules smaller than 1 cm. We also discuss the most common causes of 18F-FDG false-positive and false-negative results in the pulmonary parenchyma. In patient 1, contrast-enhanced CT performed 10 days before PET-CT did not show any abnormality in the site of uptake; in patient 2, high-resolution CT performed 1 month after PET showed a bronchiole filled with dense material interpreted as a mucoid impaction; in patient 3, contrast-enhanced CT performed 15 days before PET-CT did not identify any nodules; in patients 4 and 5, contrast-enhanced CT revealed a nodule smaller than 1 cm which could not be characterized. The 18F-FDG uptake at follow-up confirmed the malignant nature of pulmonary nodules smaller than 1 cm which were undetectable, misinterpreted, not recognized or undetermined at contrast-enhanced CT. CONCLUSION: In all five oncologic patients, 18F-FDG was able to metabolically characterize as malignant those nodules smaller than 1 cm, underlining that: 18F-FDG uptake is not only a function of tumor size but it is strongly related to the tumor biology; functional alterations may precede morphologic abnormalities. In the oncologic population, especially in higher-risk patients, PET can be performed even when the nodules are smaller than 1 cm, because it might give an earlier characterization and, sometimes, could guide in the identification of alterations missed on CT

Proposed Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation at a Noninnocent Mononuclear Metal-Thiolate.

The noninnocent coordinatively saturated mononuclear metal-thiolate complex ReL3 (L = diphenylphosphinobenzenethiolate) serves as an electrocatalyst for hydrogen evolution or hydrogen oxidation dependent on the presence of acid or base and the applied potential. ReL3 reduces acids to H2 in dichloromethane with an overpotential of 380 mV and a turnover frequency of 32 ± 3 s(-1). The rate law displays a second-order dependence on acid concentration and a first-order dependence on catalyst concentration with an overall third-order rate constant (k) of 184 ± 2 M(-2) s(-1). Reactions with deuterated acid display a kinetic isotope effect of 9 ± 1. In the presence of base, ReL3 oxidizes H2 with a turnover frequency of 4 ± 1 s(-1). The X-ray crystal structure of the monoprotonated species [Re(LH)L2](+), an intermediate in both catalytic H2 evolution and oxidation, has been determined. A ligand-centered mechanism, which does not require metal hydride intermediates, is suggested based on similarities to the redox-regulated, ligand-centered binding of ethylene to ReL3

Proposed Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation at a Noninnocent Mononuclear Metal–Thiolate

The noninnocent coordinatively saturated mononuclear metal–thiolate complex ReL₃ (L = diphenylphosphinobenzenethiolate) serves as an electrocatalyst for hydrogen evolution or hydrogen oxidation dependent on the presence of acid or base and the applied potential. ReL₃ reduces acids to H₂ in dichloromethane with an overpotential of 380 mV and a turnover frequency of 32 ± 3 s^–1. The rate law displays a second-order dependence on acid concentration and a first-order dependence on catalyst concentration with an overall third-order rate constant (<i>k</i>) of 184 ± 2 M^–2 s^–1. Reactions with deuterated acid display a kinetic isotope effect of 9 ± 1. In the presence of base, ReL₃ oxidizes H₂ with a turnover frequency of 4 ± 1 s^–1. The X-ray crystal structure of the monoprotonated species [Re­(LH)­L₂]⁺, an intermediate in both catalytic H₂ evolution and oxidation, has been determined. A ligand-centered mechanism, which does not require metal hydride intermediates, is suggested based on similarities to the redox-regulated, ligand-centered binding of ethylene to ReL₃

Proposed Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation at a Noninnocent Mononuclear Metal–Thiolate

The noninnocent coordinatively saturated mononuclear metal–thiolate complex ReL₃ (L = diphenylphosphinobenzenethiolate) serves as an electrocatalyst for hydrogen evolution or hydrogen oxidation dependent on the presence of acid or base and the applied potential. ReL₃ reduces acids to H₂ in dichloromethane with an overpotential of 380 mV and a turnover frequency of 32 ± 3 s^–1. The rate law displays a second-order dependence on acid concentration and a first-order dependence on catalyst concentration with an overall third-order rate constant (<i>k</i>) of 184 ± 2 M^–2 s^–1. Reactions with deuterated acid display a kinetic isotope effect of 9 ± 1. In the presence of base, ReL₃ oxidizes H₂ with a turnover frequency of 4 ± 1 s^–1. The X-ray crystal structure of the monoprotonated species [Re­(LH)­L₂]⁺, an intermediate in both catalytic H₂ evolution and oxidation, has been determined. A ligand-centered mechanism, which does not require metal hydride intermediates, is suggested based on similarities to the redox-regulated, ligand-centered binding of ethylene to ReL₃