title: Constrained Source Space MR Spectroscopy: Multiple Voxels, No Gradient Readout.
abstract: OBJECTIVE
  Our goal was to develop a novel technique for measuring a small number of localized spectra simultaneously and in a time-efficient manner.
  
  
  METHODS
  Using appropriate radiofrequency pulses, the magnetization from multiple voxels is excited simultaneously and then separated (reconstructed) by using the individual coil-sensitivity profiles from a multichannel receiver coil. Because no gradients are used for k-space encoding, constrained source space MR spectroscopy provides a time advantage over conventional spectroscopic imaging and an improved signal-to-noise ratio per square root of unit time over single-voxel spectroscopy applied at each successive location. In the present work, we considered prototype application of constrained source space MR spectroscopy for 2 voxels.
  
  
  RESULTS
  Experimental data from healthy volunteers and simulation results showed that constrained source space MR spectroscopy is effective at extracting 2 independent spectra even in the challenging scenario of the voxels being closely spaced. Also, from 6 patients with various types of brain cancer we obtained 2-voxel constrained source space MR spectroscopy data, which showed spectra of clinical quality in half the time required to perform successive single-voxel MR spectroscopy.
  
  
  CONCLUSIONS
  Constrained source space MR spectroscopy provides clinical quality spectra and could be used to probe multiple voxels simultaneously in combination with Hadamard encoding for further scan-time reductions.
authors.affiliation: From the Departments of Medical Biophysics (K.L., S.J.G.) Physical Sciences (K.L., S.J.G.), Sunnybrook Research Institute, Toronto, Ontario, Canada landheer@sri.utoronto.ca.
authors.forename: K
authors.initials: K
authors.lastname: Landheer
authors.affiliation: Radiation Oncology, Sunnybrook Odette Cancer Centre (A.S.), University of Toronto, Ontario, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Sahgal
authors.affiliation: Surgery (S.D.) Keenan Research Centre (S.D.), St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Das
authors.affiliation: From the Departments of Medical Biophysics (K.L., S.J.G.) Physical Sciences (K.L., S.J.G.), Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors.forename: S J
authors.initials: SJ
authors.lastname: Graham
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods; D001932:Brain Neoplasms / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio