title: Quantitative T2 measurement of a single voxel with arbitrary shape using pinwheel excitation and CPMG acquisition.
abstract: OBJECTIVE
  The aim of this study is to present a new approach for making quantitative single-voxel T (2) measurements from an arbitrarily shaped region of interest (ROI), where the advantage of the signal-to-noise ratio (SNR) per unit time of the single-voxel approach over conventional imaging approach can be achieved.
  
  
  METHODS
  Two-dimensional (2D) spatially selective radiofrequency (RF) pulses are proposed in this work for T (2) measurements based on using interleaved spiral trajectories in excitation k-space (pinwheel excitation pulses), combined with a summed Carr-Purcell Meiboom-Gill (CPMG) echo acquisition. The technique is described and compared to standard multi-echo imaging methods, on a two-compartment water phantom and an excised brain tissue.
  
  
  RESULTS
  The studies show good agreement between imaging and our method. The measured improvement factors of SNR per unit time of our single-voxel approach over imaging approach are close to the predicted values.
  
  
  CONCLUSIONS
  Measuring T (2) relaxation times from a selected ROI of arbitrary shape using a single-voxel rather than an imaging approach can increase the SNR per unit time, which is critical for dynamic T (2) or multi-component T (2) measurements.
authors.affiliation: Department of Biomedical Engineering, Yale University, New Haven, CT, USA. qin@mri.jhu.edu
authors.forename: Qin
authors.initials: Q
authors.lastname: Qin
authors.forename: John C
authors.initials: JC
authors.lastname: Gore
authors.forename: Robin A
authors.initials: RA
authors.lastname: de Graaf
authors.forename: Mark D
authors.initials: MD
authors.lastname: Does
mesh_terms: D000818:Animals; D001698:Biomedical Engineering; D001921:Brain / Q000033:anatomy & histology; D017352:Echo-Planar Imaging / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D019047:Phantoms, Imaging; D011846:Radio Waves; D012453:Saimiri