Comparison of amino acid positron emission tomographic radiotracers for molecular imaging of primary and metastatic brain tumors.

Positron emission tomography (PET) is an imaging technology that can detect and characterize tumors based on their molecular and biochemical properties, such as altered glucose, nucleoside, or amino acid metabolism. PET plays a significant role in the diagnosis, prognostication, and treatment of various cancers, including brain tumors. In this article, we compare uptake mechanisms and the clinical performance of the amino acid PET radiotracers (l-[methyl-11C]methionine [MET], 18F-fluoroethyl-tyrosine [FET], 18F-fluoro-l-dihydroxy-phenylalanine [FDOPA], and 11C-alpha-methyl-l-tryptophan [AMT]) most commonly used for brain tumor imaging. First, we discuss and compare the mechanisms of tumoral transport and accumulation, the basis of differential performance of these radioligands in clinical studies. Then we summarize studies that provided direct comparisons among these amino acid tracers and to clinically used 2-deoxy-2[18F]fluoro-d-glucose [FDG] PET imaging. We also discuss how tracer kinetic analysis can enhance the clinical information obtained from amino acid PET images. We discuss both similarities and differences in potential clinical value for each radioligand. This comparative review can guide which radiotracer to favor in future clinical trials aimed at defining the role of these molecular imaging modalities in the clinical management of brain tumor patients.

Group B streptococcal meningitis in infants beyond the neonatal period.

OBJECTIVES: To describe the clinico-bacteriological profile, and early outcomes of infants diagnosed with Group B streptococcus (GBS) meningitis. METHODS: This was a retrospective review of infants (aged 1 mo to 2 y) diagnosed with GBS meningitis in a tertiary care hospital in New Delhi from October 2010 through January 2012. The clinico-bacteriological data and early outcomes of infants with suspected bacterial meningitis and a positive CSF latex agglutination test for GBS were studied. The CSF samples were subjected to PCR for broad spectrum 16s ribosomal DNA and the GBS species specific gene, the scpB. RESULTS: Twenty seven patients (13 boys, and 14 girls) were diagnosed with GBS meningitis during the study period. Broad spectrum 16s ribosomal DNA PCR was performed on 18 of the 27 CSF samples. Sixteen were positive. All these 16 were also positive for the species specific scpB gene. The median duration of hospital stay was 7 d (range 1-72 d). Nine patients died. One patient each developed ventriculitis, optic atrophy and hydrocephalus. Overall, 12 patients had a complete recovery at discharge. CONCLUSIONS: GBS must be considered in the etiology of bacterial meningitis in Indian infants.