title: Multi-spin echo spatial encoding provides three-fold improvement of temperature precision during intermolecular zero quantum thermometry.
abstract: OBJECTIVE
  Intermolecular multiple quantum coherences (iMQCs) are a source of MR contrast with applications including temperature imaging, anisotropy mapping, and brown fat imaging. Because all applications are limited by signal-to-noise ratio (SNR), we developed a pulse sequence that detects intermolecular zero quantum coherences with improved SNR.
  
  
  METHODS
  A previously developed pulse sequence that detects iMQCs, HOMOGENIZED with off resonance transfer (HOT), was modified with a multi-spin echo spatial encoding scheme (MSE-HOT). MSE-HOT uses a series of refocusing pulses to generate a stack of images that are averaged in postprocessing for higher SNR. MSE-HOT performance was quantified by measuring its temperature accuracy and precision during hyperthermia of ex vivo red bone marrow samples.
  
  
  RESULTS
  MSE-HOT yielded a three-fold improvement in temperature precision relative to previous pulse sequences. Sources of improved precision were 1) echo averaging and 2) suppression of J-coupling in the methylene protons of fat. MSE-HOT measured temperature change with an accuracy of 0.6°C.
  
  
  CONCLUSIONS
  MSE-HOT improved the temperature accuracy and precision of HOT to a level that is sufficient for hyperthermia of bone marrow.
authors.affiliation: Duke University, Durham, North Carolina, USA.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Davis
authors.affiliation: Duke University, Durham, North Carolina, USA.
authors.forename: Zijian
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Georgia Institute of Technology, Atlanta, Georgia, USA.
authors.forename: Hyunkoo
authors.initials: H
authors.lastname: Chung
authors.affiliation: Duke University, Durham, North Carolina, USA.
authors.forename: Warren S
authors.initials: WS
authors.lastname: Warren
mesh_terms: D000465:Algorithms; D016880:Anisotropy; D001853:Bone Marrow / Q000000981:diagnostic imaging*; D003198:Computer Simulation; D003287:Contrast Media / Q000737:chemistry; D017352:Echo-Planar Imaging / Q000379:methods; D006801:Humans; D006979:Hyperthermia, Induced; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015233:Models, Statistical; D019047:Phantoms, Imaging; D011789:Quantum Theory; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D013696:Temperature
chemical_list: D003287:Contrast Media
keywords: Carr-Purcell-Meiboom-Gill; intermolecular multiple quantum coherence; red bone marrow; temperature imaging