Visibility of vascular phenylalanine in dynamic uptake studies in humans using magnetic resonance spectroscopy.
In general, vascular contributions to the in vivo magnetic resonance (MR) brain spectrum are too small to be relevant. In cerebral uptake studies, however, vascular contributions may constitute a major confounder. MR visibility of vascular Phe was investigated by recording localized spectra from fully oxygenated and well-mixed whole blood. Blood Phe levels determined by MR spectroscopy (MRS) and ion-exchange chromatography showed excellent correlation. In addition, effects of blood flow were shown to have a small effect on signal amplitude with the MRS methodology used. Hence, blood Phe is almost completely MR visible at 1.5 T, even though it is severely broadened at higher fields. Without appropriate correction, cerebral Phe influx in studies of brain Phe uptake in phenylketonuria patients or healthy subjects would appear to be faster and lead to higher levels. Similar effects are envisaged for studies of ethanol or glucose uptake across the blood-brain barrier.
Kreis
Roland
R
Department of Clinical Research, Unit for MR Spectroscopy & Methodology, University of Berne, Switzerland. roland.kreis@insel.ch
Salvisberg
Christian
C
Lutz
Thomas
T
Boesch
Chris
C
Pietz
Joachim
J
D001783:Blood Flow Velocity / Q000502:physiology; D001923:Brain Chemistry; D002560:Cerebrovascular Circulation; D002852:Chromatography, Ion Exchange; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010649:Phenylalanine / Q000097:blood*; D010661:Phenylketonurias / Q000097:blood*
D010649:Phenylalanine