title: Estimation of the absolute shear stiffness of human lung parenchyma using (1) H spin echo, echo planar MR elastography.
abstract: OBJECTIVE
  To develop a rapid proton MR elastography (MRE) technique that can quantify the absolute shear stiffness of lung parenchyma, to investigate the ability to differentiate respiration-dependent stiffness variations of the lung, and to demonstrate clinical feasibility.
  
  
  METHODS
  A spin-echo echo planar imaging MRE sequence (SE-EPI MRE) with a very short echo time was developed and tested in a series of five healthy volunteers at three different lung volumes: (i) residual volume (RV), (ii) total lung capacity (TLC), (iii) and midway between RV and TLC (MID). At each volume, lung density was quantified using a MR-based density mapping sequence. For reference, data were acquired using the previously described spin-echo lung MRE sequence (SE-MRE). MRE data were also acquired in a patient with proven Idiopathic Pulmonary Fibrosis (IPF) to test clinical feasibility.
  
  
  RESULTS
  The SE-EPIMRE sequence reduced total acquisition time by a factor of 2 compared with the SE-MRE sequence. Lung parenchyma median shear stiffness for the 5 volunteers quantified with the SE-EPI MRE sequence was 0.9 kPa, 1.1 kPa, and 1.6 kPa at RV, MID, and TLC, respectively. The corresponding values obtained with the SE-MRE sequence were 0.9 kPa, 1.1 kPa, and 1.5 kPa. Absolute shear stiffness was also successfully measured in the IPF patient.
  
  
  CONCLUSIONS
  The results indicate that stiffness variations due to respiration could be measured with the SE-EPIMRE technique and were equivalent to values generated by the previously described SE-MRE approach. Preliminary data obtained from the patient demonstrate clinical feasibility.
authors.affiliation: Philips Healthcare, Bangalore, Karnataka, India.
authors.forename: Yogesh K
authors.initials: YK
authors.lastname: Mariappan
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Glaser
authors.forename: David L
authors.initials: DL
authors.lastname: Levin
authors.forename: Robert
authors.initials: R
authors.lastname: Vassallo
authors.forename: Rolf D
authors.initials: RD
authors.lastname: Hubmayr
authors.forename: Carl
authors.initials: C
authors.lastname: Mottram
authors.forename: Richard L
authors.initials: RL
authors.lastname: Ehman
authors.forename: Kiaran P
authors.initials: KP
authors.lastname: McGee
mesh_terms: D000328:Adult; D017352:Echo-Planar Imaging / Q000379:methods*; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005240:Feasibility Studies; D005652:Functional Residual Capacity / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008168:Lung / Q000503:physiopathology*; D017563:Lung Diseases, Interstitial / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012115:Residual Volume / Q000502:physiology; D033081:Shear Strength / Q000502:physiology*; D014109:Total Lung Capacity / Q000502:physiology
keywords: interstitial lung disease; lung MR elastography; lung fibrosis; magnetic resonance elastography; shear stiffness