Imaging obstructed ventilation with NMR using inert fluorinated gases

J Appl Physiol (1985). 2000 Jun;88(6):2279-86. doi: 10.1152/jappl.2000.88.6.2279.


We partially obstructed the left bronchi of rats and imaged an inert insoluble gas, SF(6), in the lungs with NMR using a technique that clearly differentiates obstructed and normal ventilation. When the inhaled fraction of O(2) is high, SF(6) concentrates dramatically in regions of the lung with low ventilation-to-perfusion ratios (VA/Q); therefore, these regions are brighter in an image than where VA/Q values are normal or high. A second image, made when the inhaled fraction of O(2) is low, serves as a reference because the SF(6) fraction is nearly uniform, regardless of VA/Q. The quotient of the first and second images displays the low-VA/Q regions and is corrected for other causes of brightness variation. The technique may provide sufficient quantification of VA/Q to be a useful research tool. The noise in the quotient image is described by the probability density function for the quotient of two normal random variables. When the signal-to-noise ratio of the denominator image is >10, the signal-to-noise ratio of the quotient image is similar to that of the parent images and decreases with pixel value.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Artifacts
  • Magnetic Resonance Imaging*
  • Oxygen
  • Rats
  • Reference Values
  • Respiration
  • Respiration Disorders / diagnosis*
  • Respiration Disorders / physiopathology
  • Sulfur Hexafluoride*
  • Ventilation-Perfusion Ratio


  • Oxygen
  • Sulfur Hexafluoride