Apparent posterior cerebral artery territory perfusion asymmetry on arterial spin labeling MRI is a common non-pathologic finding in patients with a unilateral fetal posterior cerebral artery

Abraham Noorbakhsh,Nikdokht Farid,Divya S Bolar

doi:10.1007/s00234-021-02794-9

Abraham Noorbakhsh, Nikdokht Farid + Show 1 more

Open Access

https://doi.org/10.1007/s00234-021-02794-9

Copy DOI

Journal: Neuroradiology	Publication Date: Aug 30, 2021
Citations: 2	License type: open-access

Affiliation: University of California, San Diego

Abstract

PurposeTo determine the frequency of apparent posterior cerebral artery (PCA) territory asymmetry seen on arterial spin labeling (ASL) imaging in patients with a unilateral fetal PCA, but without underlying clinical or imaging pathology to suggest true hypoperfusion.MethodsA search of radiology reports from 1/2017 through 6/2020 was performed with the inclusion term "fetal PCA.” Eighty patients were included with unilateral fetal PCA confirmed on MRA or CTA, with brain MRI including ASL imaging, and without conventional imaging abnormality or clinical symptoms referable to the PCA territories. Cases were evaluated by two independent readers for visually apparent PCA perfusion asymmetries. ASL imaging consisted of pseudocontinuous ASL with 1.5 s labeling duration and 2 s post-labeling delay adapted from white paper recommendations.ResultsThirteen of 80 cases (16.2%) had apparent hypoperfusion in the PCA territory contralateral to the side of the fetal PCA. Agreement between readers was near perfect (97.5%, κ = 0.91). This finding was more common in patients who were older, scanned on a 3.0 T magnet, and who had non-visualization of the posterior communicating artery contralateral to the fetal PCA.ConclusionApparent PCA hypoperfusion on ASL is not uncommon in patients with a contralateral fetal PCA who have no clinical or conventional imaging findings to suggest true hypoperfusion. This phenomenon is likely due to differential blood velocities between the carotid and vertebral arteries that result in differential arterial transit times and labeling efficiency. It is important for radiologists to know that apparent hypoperfusion may arise from variant circle of Willis anatomy.

Highlights

Arterial spin labeling (ASL) is a non-contrast MR imaging technique used to assess cerebral perfusion and has increasingly become a common component of routine clinical brain MRI protocols, after the 2015 publication of consensus recommendations for clinical use, known as the ASL white paper [1]
Pseudocontinuous ASL is the most common variant of ASL imaging used in practice and recommended by the white paper for clinical applications [1]
The two cases with disagreement were reviewed and discussed by the readers together to reach a final consensus on the presence of Pseudocontinuous ASL (pCASL) CBF perfusion asymmetry

Summary

Introduction

Arterial spin labeling (ASL) is a non-contrast MR imaging technique used to assess cerebral perfusion and has increasingly become a common component of routine clinical brain MRI protocols, after the 2015 publication of consensus recommendations for clinical use, known as the ASL white paper [1]. Pseudocontinuous ASL (pCASL) is the most common variant of ASL imaging used in practice and recommended by the white paper for clinical applications [1]. With pCASL, a series of radiofrequency (RF) pulses are applied to a labeling plane in the upper neck to generate a magnetically labeled bolus within the cervical arteries [10]. A post-labeling delay (PLD) allows this labeled blood to arrive at the imaging plane, disseminate out of the macrovasculature, and accumulate into the microvasculature and parenchyma. Cerebral perfusion images are subsequently generated. pCASL, is prone to several artifacts that can result in erroneous perfusion estimates [11]

Methods

Results

Discussion

Conclusion