Volumetric abdominal perfusion measurement using a pseudo‐randomly sampled 3D fast‐spin‐echo (FSE) arterial spin labeling (ASL) sequence and compressed sensing reconstruction

Abstract

Purpose To improve image quality and spatial coverage for abdominal perfusion imaging by implementing an arterial spin labeling (ASL) sequence that combines variable‐density 3D fast‐spin‐echo (FSE) with Cartesian trajectory and compressed‐sensing (CS) reconstruction. Methods A volumetric FSE sequence was modified to include background‐suppressed pseudo‐continuous ASL labeling and to support variable‐density (VD) Poisson‐disk sampling for acceleration. We additionally explored the benefits of center oversampling and variable outer k‐space sampling. Fourteen healthy volunteers were scanned on a 3T scanner to test acceleration factors as well as the various sampling schemes described under synchronized‐breathing to limit motion issues. A CS reconstruction was implemented using the BART toolbox to reconstruct perfusion‐weighted ASL volumes, assessing the impact of acceleration, different reconstruction, and sampling strategies on image quality. Results CS acceleration is feasible with ASL, and a strong renal perfusion signal could be observed even at very high acceleration rates (≈15). We have shown that ASL k‐space complex subtraction was desirable before CS reconstruction. Although averaging of multiple highly accelerated images helped to reduce artifacts from physiologic fluctuations, superior image quality was achieved by interleaving of different highly undersampled pseudo‐random spatial sampling patterns and using 4D‐CS reconstruction. Combination of these enhancements produces high‐quality ASL volumes in under 5 min. Conclusions High‐quality isotropic ASL abdominal perfusion volumes can be obtained in healthy volunteers with a VD‐FSE and CS reconstruction. This lays the groundwork for future developments toward whole abdomen free‐breathing non‐contrast perfusion imaging.

Consensus-based technical recommendations for clinical translation of renal ASL MRI

“…Issues such as repeatability and validation of ASL with alternative methods to measure renal perfusion were extensively addressed therewith and, therefore, will not be covered in the present manuscript. The previous literature review [8] as well as 12 studies published in the intervening period [11][12][13][14][15][16][17][18][19][20][21][22], the results of a series of surveys and the discussions that took place at the in-person meetings form the basis for the final recommendations presented here.…”

Regional and depth-dependence of cortical blood-flow assessed with high-resolution Arterial Spin Labeling (ASL)

“…After estimating the coil-sensitivity using ESPIRiT on the reference PD-weighted volume, 16 we reconstructed perfusion-weighted volumes using a L 1 -wavelet regularized Compressed-Sensing reconstruction as described previously. 8…”

“…Here we employed a recently reported ASL volumetric image acquisition method 8 to explore the implications of higher resolution acquisition for cortical CBF imaging. An important advantage of this acquisition is the absence of susceptibility induced spatial distortions such that highly accurate registration with quantitative T 1 imaging and cortical surface-based analysis were readily possible across the whole brain.…”

Pancreatic perfusion modulation following glucose stimulation assessed by noninvasive arterial spin labeling (ASL) MRI

“…Additionally, multislice or volumetric acquisitions could provide information on the potential spatial modulation of perfusion and whether that might follow prior spatial knowledge on pancreatic islet routes . Previous work using volumetric segmented FSE acquisitions combined with compressed‐sensing reconstruction could be optimized for pancreatic imaging (especially due to the short T 2 ) . All this might enable studying the potential alterations of pancreatic perfusion in prediabetic or confirmed T2‐DM populations as prior experimental models have shown perfusion alterations through the timecourse of the disease …”