Imaging obstructed ventilation with NMR using inert fluorinated gases.
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.
Kuethe
D O
DO
Lovelace Respiratory Research Institute, Albuquerque, NM 87108, USA. dkuethe@NMR.org
Caprihan
A
A
Gach
H M
HM
Lowe
I J
IJ
Fukushima
E
E
D000818:Animals; D016477:Artifacts; D008279:Magnetic Resonance Imaging; D010100:Oxygen; D051381:Rats; D012016:Reference Values; D012119:Respiration; D012120:Respiration Disorders / Q000175:diagnosis* / Q000503:physiopathology; D013459:Sulfur Hexafluoride; D014692:Ventilation-Perfusion Ratio
D010100:Oxygen; D013459:Sulfur Hexafluoride