title: Assessment of [11C]-L-methionine transport into the human brain.
abstract: Neutral amino acid transport into human brain was measured using a dual-probe positron detection system or positron emission tomography (PET). Rate constants (ml/min/cc) for brain accumulation of [11C]L-methionine measured with the dual detector ranged from 0.012 to 0.078 (average 0.031) under baseline conditions and from 0.010 to 0.017 (average 0.014) after administration of nonradioactive L-phenylalanine (100 mg/kg). The net rate of brain accumulation of L-methionine ranged from 0.42 to 2.89 (average 1.28) nmol/min/cc, and decreased by 27.5-91.2% (average 53.9%) after L-phenylalanine. PET-estimated accumulation rates (ml/min/cc) of [11C]L-methionine ranged from 0.004 to 0.028 (average 0.016) baseline and from 0.010 to 0.021 (average 0.017) after L-phenylalanine. Initial volumes of distribution (ml/cc) of [11C]L-methionine (dual detector) were 0.044-0.070 (average 0.058) baseline and 0.032-0.074 (average 0.051) after phenylalanine and (PET) 0.026-0.098 (average 0.051) baseline and 0.021-0.061 (average 0.042) after phenylalanine. PET permits more accurate measurement of tracer accumulation by brain, excluding noncerebral regions included in dual-detector measurements. The dual-detector system permits better temporal resolution, facilitating kinetic analysis, and requires only one-fortieth the dose of tracer needed for PET. Multiple studies in the same patient are thus possible at low cost.
authors.affiliation: Division of Nuclear Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21205-2179.
authors.forename: L A
authors.initials: LA
authors.lastname: O'Tuama
authors.forename: T R
authors.initials: TR
authors.lastname: Guilarte
authors.forename: K H
authors.initials: KH
authors.lastname: Douglass
authors.forename: H N
authors.initials: HN
authors.lastname: Wagner
authors.forename: D F
authors.initials: DF
authors.lastname: Wong
authors.forename: R F
authors.initials: RF
authors.lastname: Dannals
authors.forename: H T
authors.initials: HT
authors.lastname: Ravert
authors.forename: A A
authors.initials: AA
authors.lastname: Wilson
authors.forename: N D
authors.initials: ND
authors.lastname: LaFrance
authors.forename: A N
authors.initials: AN
authors.lastname: Bice
mesh_terms: D001692:Biological Transport; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D002250:Carbon Radioisotopes; D006801:Humans; D008715:Methionine / Q000097:blood / Q000378:metabolism*; D008959:Models, Neurological; D010649:Phenylalanine / Q000494:pharmacology; D014055:Tomography, Emission-Computed
chemical_list: D002250:Carbon Radioisotopes; D010649:Phenylalanine; D008715:Methionine