Imaging obstructed ventilation with NMR using inert fluorinated gases.

Area of Science:

• Pulmonary Medicine
• Medical Imaging
• Nuclear Magnetic Resonance (NMR)

Background:

• Assessing regional lung ventilation-perfusion ratios (VA/Q) is crucial for diagnosing respiratory diseases.
• Current imaging techniques may lack the resolution or quantification needed for detailed VA/Q analysis.
• Nuclear Magnetic Resonance (NMR) offers a non-invasive imaging modality with potential for physiological measurements.

Purpose of the Study:

• To develop and validate a novel NMR imaging technique for differentiating and quantifying regional lung VA/Q.
• To utilize an inert, insoluble gas, sulfur hexafluoride (SF(6)), for enhanced ventilation imaging.
• To establish a method that corrects for variations in image brightness unrelated to VA/Q.

Main Methods:

• Partial obstruction of the left bronchi in rats to create ventilation defects.
• Inhaled SF(6) gas NMR imaging under two conditions: high and low inhaled oxygen fractions.
• Image analysis involving the quotient of images acquired under different oxygen conditions to highlight low VA/Q regions.

Main Results:

• SF(6) concentrated in low VA/Q lung regions when the inhaled O(2) fraction was high, creating brighter image areas.
• A reference image with a low inhaled O(2) fraction showed uniform SF(6) distribution, independent of VA/Q.
• The quotient image effectively displayed and corrected for low VA/Q regions, demonstrating its utility.
• The noise characteristics of the quotient image were analyzed and found to be dependent on the signal-to-noise ratio of the input images.

Conclusions:

• The developed NMR technique successfully differentiates lung regions with low VA/Q using SF(6) gas.
• This method provides a quantitative research tool for studying ventilation abnormalities.
• The technique offers improved visualization and correction for brightness variations in lung imaging.