Systematic evaluation of velocity‐selective arterial spin labeling settings for placental perfusion measurement

Abstract

Purpose Placental function is key for successful human pregnancies. Perfusion may be a sensitive marker for the in vivo assessment of placental function. Arterial spin labeling (ASL) MRI enables noninvasive measurement of tissue perfusion and it was recently suggested that ASL with velocity‐selective (VS) labeling could be advantageous in the placenta. We systematically evaluated essential VS‐ASL sequence parameters to determine optimal settings for efficient placental perfusion measurements. Methods Eleven pregnant women were scanned at 3T using VS‐ASL with 2D multislice echo planar imaging (EPI)‐readout. One reference VS‐ASL scan was acquired in all subjects; within subgroups the following parameters were systematically varied: cutoff velocity, velocity encoding direction, and inflow time. Visual evaluation and region of interest analyses were performed to compare perfusion signal differences between acquisitions. Results In all subjects, a perfusion pattern with clear hyperintense focal regions was observed. Perfusion signal decreased with inflow time and cutoff velocity. Subject‐specific dependence on velocity encoding direction was observed. High temporal signal‐to‐noise ratios with high contrast on the perfusion images between the hyperintense regions and placental tissue were seen at ~1.6 cm/s cutoff velocity and ~1000 ms inflow time. Evaluation of measurements at multiple inflow times revealed differences in blood flow dynamics between placental regions. Conclusion Placental perfusion measurements are feasible at 3T using VS‐ASL with 2D multislice EPI‐readout. A clear dependence of perfusion signal on VS labeling parameters and inflow time was demonstrated. Whereas multiple parameter combinations may advance the interpretation of placental circulation dynamics, this study provides a basis to select an effective set of parameters for the observation of placenta perfusion natural history and its potential pathological changes.

Perfusion imaging of neuroblastoma and nephroblastoma in a paediatric population using pseudo-continuous arterial spin-labelling magnetic resonance imaging

“…For clarity data points are slightly shifted with respect to each other at each post-labelling delay and one-sided error bars are shown. pCASL pseudo-continuous arterial spin labelling, PWS perfusion weighted signal few studies have already shown promising results of flowbased ASL imaging in the abdomen for the kidneys [31,32] and placenta [33,34] in adults. Another recent study in paediatric patients with Moyamoya has shown VSASL offers a powerful approach to accurately image perfusion in these patients due to transit delay insensitivity [35].…”

Is fetal MRI ready for neuroimaging prime time? An examination of progress and remaining areas for development

“…More recently, MRI has proved to be a panoply in understanding the human placenta and its role in determining lifetime outcomes. Together with extensive innovation in adapting MRI techniques, many recent studies have provided invaluable information on the structure, function and biochemistry of the placenta across gestation ( Siauve et al, 2015 ; Porras et al, 2017 ; Rajagopalan et al, 2017b ; Harteveld et al, 2020 ). Further, this research is being extended to understand how pathophysiological conditions in the placenta or the fetus interact with the other ( Andescavage et al, 2015 ; Zun and Limperopoulos, 2018 ; Luo et al, 2017 ; León et al, 2018 ).…”

Exploring label dynamics of velocity‐selective arterial spin labeling in the kidney

“…Another advantage of flow‐sensitized ASL is that placement of a labeling slab is not required, simplifying the planning of the ASL examination, which can be complicated in the kidneys. Thus far, flow‐sensitized perfusion measurements have been demonstrated primarily in the brain, 11,13,14,16,17 with recent applications in the heart 18,19 and placenta 20,21 . We recently investigated the feasibility of VSASL labeling in the kidney at 1.5 T, and demonstrated that with properly chosen VSASL sequence parameters, labeling and subtraction artifacts due to (respiratory) motion can be avoided, and with that showed feasibility of VSASL for renal perfusion measurements 22 .…”

“…Thus far, flow-sensitized perfusion measurements have been demonstrated primarily in the brain, 11,13,14,16,17 with recent applications in the heart 18,19 and placenta. 20,21 We recently investigated the feasibility of VSASL labeling in the kidney at 1.5 T, and demonstrated that with properly chosen VSASL sequence parameters, labeling and subtraction artifacts due to (respiratory) motion can be avoided, and with that showed feasibility of VSASL for renal perfusion measurements. 22 Because a low V C in the presence of respiratory motion can cause spurious labeling of moving tissue, a higher V C is advised for the kidney than, for example, for the brain (≈ 2 cm/s) with velocity-encoding direction perpendicular to the primary direction of respiratory motion.…”