Assessment of pulmonary perfusion with breath-hold and free-breathing dynamic contrast-enhanced magnetic resonance imaging: quantification and reproducibility.

OBJECTIVES: The purpose of this study was to investigate whether quantification of pulmonary perfusion from dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) yields more reproducible results with data acquired during free breathing than with data from conventional breath-hold measurements.
MATERIAL AND METHODS: Ten healthy male volunteers underwent 2 imaging sessions at a clinical 1.5-T MRI system, separated by a week±1 day. Each of these sessions comprised 2 DCE MRI acquisitions: one performed during breath-hold and one during free, shallow breathing; both acquisitions were separated by at least 20 minutes. For all DCE MRI measurements, a standard dose of gadobutrol was used. Breath-hold measurements lasted 53 seconds; free-breathing acquisitions were performed in a total acquisition time of 146 seconds.Lung tissue was segmented automatically to minimize user influence, and pulmonary plasma flow (PPF) and volume (PPV) were quantified on a per-pixel basis with a 1-compartment model. Free-breathing measurements were analyzed twice, (a) including data from the entire acquisition duration and (b) after truncation to the duration of the breath-hold measurements. For further statistical analysis, median values of the resulting parameter maps were determined. To assess intraindividual reproducibility, intraclass correlation coefficients and coefficients of variation between the first and second measurements were calculated for breath-hold, truncated, and full free-breathing measurements, respectively. Differences in the coefficients of variation were assessed with a nonparametric 2-sided paired Wilcoxon signed rank test.
RESULTS: All 40 measurements were completed successfully. Maps of PPF and PPV could be calculated from both measurement techniques; PPF and PPV in the breath-hold measurements were significantly lower (P < 0.001) than in truncated and full free-breathing measurements. Both evaluations of the free-breathing measurements yielded higher intraclass correlation coefficients and lower coefficients of variation between the first and second measurements than the breath-hold measurements.
CONCLUSIONS: Besides offering substantially higher patient comfort, free-breathing DCE MRI acquisitions allow for pixelwise quantification of pulmonary perfusion and hence generation of parameter maps. Moreover, quantitative perfusion estimates derived from free-breathing DCE MRI measurements have better reproducibility than estimates from the conventionally used breath-hold measurements.