Nederveen, A. | Search bioRxiv

bioRxiv2019

ExploreASL: an image processing pipeline for multi-center ASL perfusion MRI studies

Arterial spin labeling (ASL) has undergone significant development since its inception, with a focus on improving standardization and reproducibility of its acquisition and quantification. In a community-wide effort towards robust and reproducible clinical ASL image processing, we developed the software package ExploreASL, allowing standardized analyses across centers and scanners. The procedures used in ExploreASL capitalize on published image processing advancements and address the challenges of multi-center datasets with scanner-specific processing and artifact reduction to limit patient exclusion. ExploreASL is self-contained, written in MATLAB and based on Statistical Parameter Mapping (SPM) and runs on multiple operating systems. The toolbox adheres to previously defined international standards for data structure, provenance, and best analysis practice. ExploreASL was iteratively refined and tested in the analysis of >10,000 ASL scans using different pulse-sequences in a variety of clinical populations, resulting in four processing modules: Import, Structural, ASL, and Population that perform tasks, respectively, for data curation, structural and ASL image processing and quality control, and finally preparing the results for statistical analyses on both single-subject and group level. We illustrate ExploreASL processing results from three cohorts: perinatally HIV-infected children, healthy adults, and elderly at risk for neurodegenerative disease. We show the reproducibility for each cohort when processed at different centers with different operating systems and MATLAB versions, and its effects on the quantification of gray matter cerebral blood flow. ExploreASL facilitates the standardization of image processing and quality control, allowing the pooling of cohorts to increase statistical power and discover between-group perfusion differences. Ultimately, this workflow may advance ASL for wider adoption in clinical studies, trials, and practice.

neuroscience↗

bioRxiv2018

Improved localizers and anatomical images to enable phosphorus magnetic resonance spectroscopy of liver metastasis at 7T

Phosphorus spectroscopy (31P) at 7T (300 MHz) enables clinically-relevant spatial resolutions and time scales with high potential for monitoring response to cancer treatment. However, at 7T collecting a radiological-grade anatomical image of the liver--which is required for performing localized 31P spectroscopy--presents a challenge. Unlike lower field-strength scanners, there is no body coil in the bore of the 7T and despite inadequate penetration depth (<10 cm), surface coils are the current state-of-the-art for acquiring anatomical (1H) images. Therefore, thus far, high field 31P spectroscopy has been limited to diffuse liver disease. However, the use of antennas enable improved penetration depths at 300 MHz, and when combined with parallel transmit, can enable body imaging at 7T. We have developed a protocol for imaging liver metastases of patients using parallel transmit and 31P spectroscopy at 7T. We used a custom-made liver coil consisting of eight 30-cm dipole antennas tuned to the proton (300 MHz) frequency, and two partially overlapping 20-cm-diameter loops tuned for 31P (120 MHz). The field of view afforded by the two antennas underneath the 31P loops is not sufficient to image the complete boundaries of the liver for chemical shift imaging (CSI) planning and region-of-interest-based B0 shimming. The liver and full axial slice of the abdomen was imaged with eight transmit/receive antennas using parallel transmit B1-shimming to overcome image voids. Through the use of antennas we overcome the challenges for multi-parametric body imaging, and can begin to explore the possibility of monitoring the response of patients with liver metastasis to cancer treatments.\n\nABBREVIATIONS

bioengineering↗