Free-breathing quantification of regional ventilation derived by phase-resolved functional lung (PREFUL) MRI

Science and Research

PURPOSE: To test the feasibility of regional fully quantitative ventilation measurement in free breathing derived by phase-resolved functional lung (PREFUL) MRI in the supine and prone positions. In addition, the influence of T2 * relaxation time on ventilation quantification is assessed. METHODS: Twelve healthy volunteers underwent functional MRI at 1.5 T using a 2D triple-echo spoiled gradient echo sequence allowing for quantitative measurement of T2 * relaxation time. Minute ventilation (DeltaV) was quantified by conventional fractional ventilation (FV) and the newly introduced regional ventilation (VR), which corrects volume errors due to image registration. DeltaVFV versus DeltaVVR and DeltaVVR versus DeltaVVR with T2 * correction were compared using Bland-Altman plots and correlation analysis. The repeatability and physiological plausibility of all measurements were tested in the supine and prone positions. RESULTS: On global and regional scales a strong correlation was observed between DeltaVFV versus DeltaVVR and DeltaVVR versus DeltaVVRT2* (r > 0.93); however, regional Bland-Altman analysis showed systematic differences (p < 0.0001). Unlike DeltaVVRT2* , DeltaVVR and DeltaVFV showed expected physiologic anterior-posterior gradients, which decreased in the supine but not in the prone position at second measurement during 3 min in the same position. For all quantification methods a moderate repeatability (coefficient of variation <20%) of ventilation was found. CONCLUSION: A fully quantified regional ventilation measurement using DeltaVVR in free breathing is feasible and shows physiologically plausible results. In contrast to conventional DeltaVFV, volume errors due to image registration are eliminated with the DeltaVVR approach. However, correction for the T2 * effect remains challenging.