Volume-Controlled ¹⁹F MR Ventilation Imaging of Fluorinated Gas

Background

19F MRI of inhaled gas tracers has developed into a promising tool for pulmonary diagnostics. Prior to clinical use, the intersession repeatability of acquired ventilation parameters must be quantified and maximized.

Purpose

To evaluate repeatability of static and dynamic 19F ventilation parameters and correlation with predicted forced expiratory volume in 1 second (FEV1%pred) with and without inspiratory volume control.

Study Type

Prospective.

Population

A total of 30 healthy subjects and 26 patients with chronic obstructive pulmonary disease (COPD).

Field Strength/Sequence

Three-dimensional (3D) gradient echo pulse sequence with golden-angle stack-of-stars k-space encoding at 1.5 T.

Assessment

All study participants underwent 19F ventilation MRI over eight breaths with inspiratory volume control (w VC) and without inspiratory volume control (w/o VC), which was repeated within 1 week. Ventilated volume percentage (VVP), fractional ventilation (FV), and wash-in time (WI) were computed. Lung function testing was conducted on the first visit.

Statistical Tests

Correlation between imaging and FEV1%pred was measured using Pearson correlation coefficient (r). Differences in imaging parameters between first and second visit were analyzed using paired t-test. Repeatability was quantified using intraclass correlation coefficient (ICC) and coefficient of variation (CoV). Minimum detectable effect size (MDES) was calculated with a power analysis for study size n = 30 and a power of 0.8. All hypotheses were tested with a significance level of 5% two sided.

Results

Strong and moderate linear correlations with FEV1%pred for COPD patients were found in almost all imaging parameters. The ICC w VC exceeds the ICC w/o VC for all imaging parameters. CoV was significantly lower w VC for initial VVP in COPD patients, FV, CoV FV, WI and standard deviation (SD) of WI. MDES of all imaging parameters were smaller w VC.

Data Conclusion

19F gas wash-in MRI with inspiratory volume control increases the correlation and repeatability of imaging parameters with lung function testing.