title: A dual K-space UNFOLD method for 3D functional brain imaging: A preliminary study.
abstract: OBJECTIVE
  To investigate a method of dual k-space unaliasing by Fourier-encoding the overlaps using the temporal dimension (DUNFOLD), a novel technique for high temporal resolution 3D functional brain imaging.
  
  
  METHODS
  Two different methods of unaliasing by Fourier-encoding the overlaps using the temporal dimension (UNFOLD), excitation UNFOLD (XUNFOLD) and acquisition UNFOLD, were merged to obtain a DUNFOLD. The feasibility of the DUNFOLD technique was examined by using a phantom and comparing its result to that of the previous XUNFOLD method. A high temporal resolution 3D functional brain imaging study was also performed, focusing on the microvascular response. Three different temporal resolutions, 20s, 10s and 5s, were tested with a spatial resolution of 0.6(3) mm3 to evaluate the method. The vascular regions of interest were selected for data analysis.
  
  
  RESULTS
  The DUNFOLD method achieved a temporal resolution approximately four times greater than those of the UNFOLD and XUNFOLD methods, without apparent signal degradation. The vascular responses in the visual cortex were obtained with high spatiotemporal resolution by using the DUNFOLD method during visual stimulation. For small vessels, the percentage change in the signal reached 18%.
  
  
  CONCLUSIONS
  The proposed DUNFOLD method yields a temporal resolution higher than those of the previous UNFOLD and XUNFOLD methods. The conclusions are likely to be important for functional imaging studies, especially those targeting cerebral vascular responsiveness.
authors.affiliation: School of Medicine, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Sang-Hoon
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Radiological Science & Neuroscience Research Institute, Gachon University, Incheon, Republic of Korea. Electronic address: changkik@gmail.com.
authors.forename: Chang-Ki
authors.initials: CK
authors.lastname: Kang
mesh_terms: D000465:Algorithms; D001931:Brain Mapping / Q000379:methods*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005583:Fourier Analysis; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010865:Pilot Projects; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D062211:Spatio-Temporal Analysis; D014793:Visual Cortex / Q000502:physiology*
keywords: Functional imaging; Tailored RF; UNFOLD; Vascular response; XUNFOLD