Abstract
BackgroundImage-quality assessment is a fundamental step before clinical evaluation of magnetic resonance images. The aim of this study was to introduce a visual scoring system that provides a quality control standard for arterial spin labeling (ASL) and that can be applied to cerebral blood flow (CBF) maps, as well as to ancillary ASL images.MethodsThe proposed image quality control (QC) system had two components: (1) contrast-based QC (cQC), describing the visual contrast between anatomical structures; and (2) artifact-based QC (aQC), evaluating image quality of the CBF map for the presence of common types of artifacts. Three raters evaluated cQC and aQC for 158 quantitative signal targeting with alternating radiofrequency labelling of arterial regions (QUASAR) ASL scans (CBF, T1 relaxation rate, arterial blood volume, and arterial transient time). Spearman correlation coefficient (r), intraclass correlation coefficients (ICC), and receiver operating characteristic analysis were used.ResultsIntra/inter-rater agreement ranged from moderate to excellent; inter-rater ICC was 0.72 for cQC, 0.60 for aQC, and 0.74 for the combined QC (cQC + aQC). Intra-rater ICC was 0.90 for cQC; 0.80 for aQC, and 0.90 for the combined QC. Strong correlations were found between aQC and CBF maps quality (r = 0.75), and between aQC and cQC (r = 0.70). A QC score of 18 was optimal to discriminate between high and low quality clinical scans.ConclusionsThe proposed QC system provided high reproducibility and a reliable threshold for discarding low quality scans. Future research should compare this visual QC system with an automatic QC system.
Highlights
Image-quality assessment is a fundamental step before clinical evaluation of magnetic resonance images
Arterial blood volume maps are similar to low-resolution angiography maps, whereas arterial transit time (ATT) maps show the time necessary for the labelled blood to flow from the labelling slab to the vascular compartment of the imaging voxel
This study introduces a visual quality control (QC) system for the clinical evaluation of arterial spin labeling (ASL) perfusion maps
Summary
Image-quality assessment is a fundamental step before clinical evaluation of magnetic resonance images. The aim of this study was to introduce a visual scoring system that provides a quality control standard for arterial spin labeling (ASL) and that can be applied to cerebral blood flow (CBF) maps, as well as to ancillary ASL images. ASL techniques can be modified to acquire CBF images at multiple post-labelling delays This offers more information about the labelled bolus and its arrival to the tissue, providing more comprehensive haemodynamic parameters [14, 15]. One of these techniques is the quantitative signal targeting with alternating radiofrequency labelling of arterial regions (QUASAR) [16]. Boundaries between the territories of the anterior, middle, and posterior cerebral arteries (watershed areas) have longer ATT than the core of these perfusion territories, thereby delineating areas prone to borderzone or watershed stroke [17]
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