title: Automatic tuning and matching of a small multifrequency saddle coil at 4.7 T.
abstract: A new circuit design for automatically tuning and matching a saddle coil for small animal imaging is presented. This design allows working at (1)H, (19)F, and (3)He resonance frequencies in a 4.7 T spectrometer. It is based on a balanced circuit with commercial variable capacity diodes controlled by a computer using digital potentiometers. The change between two different frequencies can be accurately performed in a few seconds. System Q is compared, between 140-210 MHz, to the same coil tuned and matched with high Q variable capacitors. Differences lower than 5% were found with a loaded coil. The proposed design has initially been evaluated in (19)F and (1)H NMR images acquired with a five-tube phantom. An application is also shown for the acquisition of (3)He, (19)F, and (1)H lung images in a control rat.
authors.affiliation: Instituto de Estudios Biofuncionales, Universidad Complutense de Madrid, Madrid 28040, Spain. pdeafr@ieb.ucm.es
authors.forename: Rigoberto Pérez
authors.initials: RP
authors.lastname: de Alejo
authors.forename: Carlos
authors.initials: C
authors.lastname: Garrido
authors.forename: Palmira
authors.initials: P
authors.lastname: Villa
authors.forename: Ignacio
authors.initials: I
authors.lastname: Rodriguez
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Vaquero
authors.forename: Jesús
authors.initials: J
authors.lastname: Ruiz-Cabello
authors.forename: Manuel
authors.initials: M
authors.lastname: Cortijo
mesh_terms: D000703:Analog-Digital Conversion; D000818:Animals; D004867:Equipment Design; D005461:Fluorine; D006371:Helium; D006859:Hydrogen; D007089:Image Enhancement / Q000295:instrumentation*; D007554:Isotopes; D008168:Lung / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation; D019047:Phantoms, Imaging; D011199:Potentiometry / Q000295:instrumentation; D051381:Rats; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation
chemical_list: D007554:Isotopes; D006371:Helium; D005461:Fluorine; D006859:Hydrogen