High Intravascular Signal Arterial Transit Time Artifacts Have Negligible Effects on Cerebral Blood Flow and Cerebrovascular Reserve Capacity Measurement Using Single Postlabel Delay Arterial Spin-Labeling in Patients with Moyamoya Disease

Abstract

BACKGROUND AND PURPOSE: Arterial spin-labeling-derived CBF values may be affected by arterial transit time artefacts. Thus, our aim was to assess to what extent arterial spin-labeling-derived CBF and cerebrovascular reserve capacity values in major vascular regions are overestimated due to the arterial transit time artifacts in patients with Moyamoya disease. MATERIALS AND METHODS:Eight patients with Moyamoya disease were included before or after revascularization surgery. CBF maps were acquired using a 3D pseudocontinuous arterial spin-labeling sequence, before and 5, 15, and 25 minutes after an IV acetazolamide injection and were registered to each patient's 3D-T1-weighted images. Vascular regions were defined by spatial normalization to a Montreal Neurological Institute-based vascular regional template. The arterial transit time artifacts were defined as voxels with high signal intensity corresponding to the right tail of the histogram for a given vascular region, with the cutoff selected by visual inspection. Arterial transit time artifact maps were created and applied as masks to exclude arterial transit time artifacts on CBF maps, to create corrected CBF maps. The cerebrovascular reserve capacity was calculated as CBF after acetazolamide injection relative to CBF at baseline for corrected and uncorrected CBF values, respectively. RESULTS: A total of 16 examinations were analyzed. Arterial transit time artifacts were present mostly in the MCA, whereas the posterior cerebral artery was generally unaffected. The largest differences between corrected and uncorrected CBF and cerebrovascular reserve capacity values, reported as patient group average ratio and percentage point difference, respectively, were 0.978 (95% CI, 0.968-0.988) and 1.8 percentage points (95% CI, 0.3-3.2 percentage points). Both were found in the left MCA, 15 and 5 minutes post-acetazolamide injection, respectively. CONCLUSIONS: Arterial transit time artifacts have negligible overestimation effects on calculated vascular region-based CBF and cerebrovascular reserve capacity values derived from single-delay 3D pseudocontinuous arterial spin-labeling. ABBREVIATIONS: ACA ¼ anterior cerebral artery; ACZ ¼ acetazolamide; ASL ¼ arterial spin-labeling; ATT ¼ arterial transit time; ATT over ¼ long arterial transit time where CBF is overestimated; ATT under ¼ very long arterial transit time where CBF is underestimated; CVRC ¼ cerebrovascular reserve capacity; Diff ¼ absolute difference; MMD ¼ Moyamoya disease; PCA ¼ posterior cerebral artery; pCASL ¼ pseudocontinuous arterial spin-labeling; PLD ¼ postlabeling delay; pp ¼ percentage points

Variable Temporal Cerebral Blood Flow Response to Acetazolamide in Moyamoya Patients Measured Using Arterial Spin Labeling

“…No exclusions were made due to head motion, and no venous hyperintensities were found in major venous structures and cortical veins. High signal intravascular arterial transit time artifacts were generally found; however, we have previously shown that these have a negligible effect upon CBF quantification using the same method as described here (26). Structural 3D T2-weighted fluid-attenuated inversion recovery (FLAIR) and 3D contrastenhanced T1-weighted (CE-T1WI) images were acquired with spatial resolution 0.625 × 0.625 × 0.560 and 0.938 × 0.938 × 1 mm 3 for tissue segmentation and registration purposes, respectively.…”

Screening of postoperative cerebral hyperperfusion syndrome in moyamoya disease: a three-dimensional pulsed arterial-spin labeling magnetic resonance imaging approach

“…The results of ASL perfusion MRI can be influenced by moyamoya vessels, which may lead to an underestimation of CBF values ( Zaharchuk et al, 2011 ). However, recent studies have suggested that the overestimation effects on the calculated CBF using single post-label delay ASL can be negligible in patients with MMD ( Fahlström et al, 2020 ). A validation study that compares it with other methods and re-evaluates it will be conducted in the future.…”

ASL-MRI-guided evaluation of multiple burr hole revascularization surgery in Moyamoya disease

“…Parametric maps of time-to-peak (TTP) were generated. In addition, a structural 3D T2-weighted fluid attenuated inversion recovery (FLAIR) image, 3D contrast-enhanced T1-weighted (CE-T1WI) image and 3D time-of-flight MR angiography were acquired [ 9 , 10 ].…”