title: Interleaved multishot imaging by spatiotemporal encoding: A fast, self-referenced method for high-definition diffusion and functional MRI.
abstract: OBJECTIVE
  Single-shot imaging by spatiotemporal encoding (SPEN) can provide higher immunity to artifacts than its echo planar imaging-based counterparts. Further improvements in resolution and signal-to-noise ratio could be made by rescinding the sequence's single-scan nature. To explore this option, an interleaved SPEN version was developed that was capable of delivering optimized images due to its use of a referenceless correction algorithm.
  
  
  METHODS
  A characteristic element of SPEN encoding is the absence of aliasing when its signals are undersampled along the low-bandwidth dimension. This feature was exploited in this study to segment a SPEN experiment into a number of interleaved shots whose inaccuracies were automatically compared and corrected as part of a navigator-free image reconstruction analysis. This could account for normal phase noises, as well as for object motions during the signal collection.
  
  
  RESULTS
  The ensuing interleaved SPEN method was applied to phantoms and human volunteers and delivered high-quality images even in inhomogeneous or mobile environments. Submillimeter functional MRI activation maps confined to gray matter regions as well as submillimeter diffusion coefficient maps of human brains were obtained.
  
  
  CONCLUSIONS
  We have developed an interleaved SPEN approach for the acquisition of high-definition images that promises a wider range of functional and diffusion MRI applications even in challenging environments.
authors.affiliation: Chemical Physics Department, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Rita
authors.initials: R
authors.lastname: Schmidt
authors.affiliation: Chemical Physics Department, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Amir
authors.initials: A
authors.lastname: Seginer
authors.affiliation: Chemical Physics Department, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Lucio
authors.initials: L
authors.lastname: Frydman
mesh_terms: D000465:Algorithms; D001921:Brain / Q000473:pathology; D001940:Breast / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging; D017352:Echo-Planar Imaging; D005260:Female; D066128:Gray Matter / Q000473:pathology; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D015233:Models, Statistical; D009038:Motion; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio
keywords: full refocusing; high-definition fMRI; high-resolution ADCs; interleaved MRI; referenceless reconstruction; spatiotemporal encoding