Abstract
PURPOSE: The placenta remains the least understood human organ in large part because of the lack of non-invasive tools currently available to examine placental function in vivo. This study investigates the feasibility of using velocity-selective arterial spin labeling (VSASL) to assess placental perfusion. METHODS: In placental perfusion imaging, VSASL was compared with pseudocontinuous ASL (PCASL), which is currently the standard technique in brain ASL. Reproducibility of placental VSASL was evaluated using two repeated scans within the same imaging session. Inflow-dependence of placental VSASL was investigated by modulating VSASL signal using maternal inhalation of 100% oxygen and variation of cutoff velocity. All experiments were performed in healthy pregnant volunteers at 1.5 T. RESULTS: Apparent placental perfusion measured using PCASL with two different labeling locations was only 16% and 9% of that of VSASL (n=7, p<0.01 for both). Placental VSASL was highly reproducible based on within-subject coefficient of variation of 3.5%, repeatability of 19.7 ml/100 g/min, and intraclass correlation coefficient of 0.97 (n=14). Placental VSASL was also found to be dependent on blood inflow given that the absolute change in apparent placental perfusion with maternal hyperoxia was significantly larger than that of two repeated scans under normoxia (n=7, p<0.01) and there was a significant difference in apparent placental perfusion between different cutoff velocities (n=6, p<0.01). CONCLUSION: This study demonstrates the feasibility of non-invasive placental perfusion imaging using VSASL and lays the groundwork for acquiring placental perfusion images in pregnancies at high risk where placental function is impaired.