Imaging obstructed ventilation with NMR using inert fluorinated gases

Dean O. Kuethe, Arvind Caprihan, H. Michael Gach, Irving J. Lowe, Eiichi Fukushima

Research output: Contribution to journalArticlepeer-review

71 Scopus citations

Abstract

We partially obstructed the left bronchi of rats and imaged an inert insoluble gas, SF6, in the lungs with NMR using a technique that clearly differentiates obstructed and normal ventilation. When the inhaled fraction of O2 is high, SF6 concentrates dramatically in regions of the lung with low ventilation-to-perfusion ratios (V̇A/Q̇); therefore, these regions are brighter in an image than where V̇A/Q̇ values are normal or high. A second image, made when the inhaled fraction of O2 is low, serves as a reference because the SF6 fraction is nearly uniform, regardless of V̇/Q̇. The quotient of the first and second images displays the low-V̇A/Q̇ regions and is corrected for other causes of brightness variation. The technique may provide sufficient quantification of V̇A/Q̇ 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.

Original languageEnglish
Pages (from-to)2279-2286
Number of pages8
JournalJournal of Applied Physiology
Volume88
Issue number6
DOIs
StatePublished - 2000

Keywords

  • Lung
  • Magnetic resonance imaging
  • Nuclear magnetic resonance
  • Perfusion
  • Probability density function
  • Quotient
  • Sulfur hexafluoride

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