title: Synthetic signal injection using a single radiofrequency channel.
abstract: OBJECTIVE
  To demonstrate that, when injecting an artificial reference signal for quantitation purposes, the real and artificial signals can be acquired separately, using a single radiofrequency (RF) channel, with no loss of fidelity. Conversion of MR signals to units of concentration can be simplified by injection of a precalibrated, artificial reference signal, or pseudo-signal. In previous implementations, the pseudo-signal was acquired simultaneously with the real signals arising from the sample and this requires a second, integrated RF channel.
  
  
  METHODS
  We used in vivo spectroscopy and in vitro imaging measurements to test the validity of the separate acquisition method.
  
  
  RESULTS
  There was very strong correlation (r = 0.94; P = 0.02) between the in vivo concentrations determined with separate and simultaneous acquisition methods. The in vitro measurements validated that the separate acquisition method compensates for differences in coil loading conditions as well as the simultaneous acquisition method.
  
  
  CONCLUSIONS
  Separate acquisition eliminates the need for a second RF channel, which allows easier implementation at sites that have only one channel available, and relaxes the constraints on the number and amplitude of pseudo-signals. This flexibility can be exploited to increase the signal to noise ratio of the pseudo-signal and reduce variability when making the conversion to units of concentration.
authors: Department of Radiology, University of Washington, Seattle, Washington, USA; Department of Radiology, Seattle Children's Hospital, Seattle, Washington, USA. marro@u.washington.edu
authors: Kenneth I
authors: KI
authors: Marro
authors: Donghoon
authors: D
authors: Lee
authors: Eric G
authors: EG
authors: Shankland
authors: Clinton M
authors: CM
authors: Mathis
authors: Cecil E
authors: CE
authors: Hayes
mesh_terms: D002138:Calibration; D005461:Fluorine; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D019047:Phantoms, Imaging
chemical_list: D005461:Fluorine