Evaluation of the biodistribution of 11C-methionine in children and young adults.

UNLABELLED: The purpose of this study was to evaluate the biodistribution of (11)C-labeled methionine in non-tumor-involved organs in pediatric patients studied for malignant diseases. METHODS: Ninety-three children and young adults with known or suspected malignancies underwent (11)C-methionine PET and CT scans. Imaging began 5-15 min after injection of 740 MBq (20 mCi) per 1.7 m(2) of body surface area. Images were acquired from the top of the head through the mid thighs. Standardized uptake values were determined using regions of interest drawn on the CT image and transferred to the corresponding transverse PET slice. RESULTS: The highest concentrations of (11)C-methionine were found in the pancreas and liver. Less intense uptake was seen in other regions, such as the salivary glands, tonsils, and bone marrow. There was little uptake in the lungs, fat (including brown adipose tissue), and muscle. Uptake in bone marrow, parotid glands, and tonsils was slightly but statistically significantly higher in men than women. Testicular, bone marrow, and left ventricular uptake increased with age. There was little variability statistically between comparisons of uptake change and groupings of age, race, sex, and patients studied at the time of diagnosis versus previously treated patients. CONCLUSION: High uptake of (11)C-methionine is reliably found in the pancreas and liver, consistent with the anabolic functions of these organs. Low uptake in the brain, neck, chest, pelvis, and extremities will facilitate tumor localization in those areas. However, intense uptake in the upper abdomen may limit the diagnostic utility of (11)C-methionine in that area.

Dichloro(4,10-dimethyl-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane)iron(III) hexafluorophosphate.

The title compound, [FeCl2(C12H26N4)]PF6, is the first mononuclear Fe3+ complex of an ethylene cross-bridged tetraaza-macrocycle to be structurally characterized. Comparison with the mononuclear Fe2+ complex of the same ligand shows that the smaller Fe3+ ion is more fully encapsulated by the cavity of the bicyclic ligand. Comparison with the mu-oxo dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,10-dimethyl-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane prevent dimerization upon oxidation of the metal centre. Nax -Fe3+ -Nax bond angles (ax is axial), and thus the degree of encapsulation by the ligand, are quite different between the mononuclear and dinuclear mu-oxo species, which is probably the consequence of steric considerations.