title: Accelerated electron paramagnetic resonance imaging using partial Fourier compressed sensing reconstruction.
abstract: Electron paramagnetic resonance (EPR) imaging has evolved as a promising tool to provide non-invasive assessment of tissue oxygenation levels. Due to the extremely short T2relaxation time of electrons, single point imaging (SPI) is used in EPRI, limiting achievable spatial and temporal resolution. This presents a problem when attempting to measure changes in hypoxic state. In order to capture oxygen variation in hypoxic tissues and localize cycling hypoxia regions, an accelerated EPRI imaging method with minimal loss of information is needed.
  
  
  
  We present an image acceleration technique, partial Fourier compressed sensing (PFCS), that combines compressed sensing (CS) and partial Fourier reconstruction. PFCS augments the original CS equation using conjugate symmetry information for missing measurements. To further improve image quality in order to reconstruct low-resolution EPRI images, a projection onto convex sets (POCS)-based phase map and a spherical-sampling mask are used in the reconstruction process. The PFCS technique was used in phantoms and in vivo SCC7 tumor mice to evaluate image quality and accuracy in estimating O2concentration.
  
  
  
  In both phantom and in vivo experiments, PFCS demonstrated the ability to reconstruct images more accurately with at least a 4-fold acceleration compared to traditional CS. Meanwhile, PFCS is able to better preserve the distinct spatial pattern in a phantom with a spatial resolution of 0.6mm. On phantoms containing Oxo63 solution with different oxygen concentrations, PFCS reconstructed linewidth maps that were discriminative of different O2concentrations. Moreover, PFCS reconstruction of partially sampled data provided a better discrimination of hypoxic and oxygenated regions in a leg tumor compared to traditional CS reconstructed images.
  
  
  
  EPR images with an acceleration factor of four are feasible using PFCS with reasonable assessment of tissue oxygenation. The technique can greatly enhance EPR applications and improve our understanding cycling hypoxia. Moreover this technique can be easily extended to various MRI applications.
authors.affiliation: University of Maryland College Park, College Park, MD 20742, United States; Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Chia-Chu
authors.initials: CC
authors.lastname: Chou
authors.affiliation: GenEpria Consulting Inc., Columbia MD 21046, United States.
authors.forename: Gadisetti V R
authors.initials: GV
authors.lastname: Chandramouli
authors.affiliation: Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Taehoon
authors.initials: T
authors.lastname: Shin
authors.affiliation: National Cancer Institute, Bethesda, MD 20892, United States.
authors.forename: Nallathamby
authors.initials: N
authors.lastname: Devasahayam
authors.affiliation: Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, United States.
authors.forename: Alan
authors.initials: A
authors.lastname: McMillan
authors.affiliation: University of Maryland College Park, College Park, MD 20742, United States.
authors.forename: Behtash
authors.initials: B
authors.lastname: Babadi
authors.affiliation: Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Rao
authors.initials: R
authors.lastname: Gullapalli
authors.affiliation: National Cancer Institute, Bethesda, MD 20892, United States.
authors.forename: Murali C
authors.initials: MC
authors.lastname: Krishna
authors.affiliation: Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, United States. Electronic address: jzhuo@umm.edu.
authors.forename: Jiachen
authors.initials: J
authors.lastname: Zhuo
mesh_terms: D000465:Algorithms; D000818:Animals; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005260:Female; D005583:Fourier Analysis; D000860:Hypoxia / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008175:Lung Neoplasms / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D019047:Phantoms, Imaging
keywords: Compressed sensing; Cycling hypoxia; Electron paramagnetic resonance imaging; Single point imaging; Virtual coils