Abstract
Cerebral blood flow (CBF) measurements are of high clinical value and can be acquired non-invasively with no radiation exposure using pseudo-continuous arterial spin labeling (ASL). The aim of this study was to evaluate accordance in resting state CBF between ASL (CBFASL) and 15O-water positron emission tomography (PET) (CBFPET) acquired simultaneously on an integrated 3T PET/MR system. The data comprised ASL and dynamic 15O-water PET data with arterial blood sampling of eighteen subjects (eight patients with focal epilepsy and ten healthy controls, age 21 to 61 years). 15O-water PET parametric CBF images were generated using a basis function implementation of the single tissue compartment model. Cortical and subcortical regions were automatically segmented using Freesurfer. Average CBFASL and CBFPET in grey matter were 60 ± 20 and 75 ± 22 mL/100 g/min respectively, with a relatively high correlation (r = 0.78, p < 0.001). Bland-Altman analysis revealed poor agreement (bias = −15 mL/100 g/min, lower and upper limits of agreements = −16 and 45 mL/100 g/min, respectively) with a negative relationship. Accounting for the negative relationship, the width of the limits of agreement could be narrowed from 61 mL/100 g/min to 35 mL/100 g/min using regression-based limits of agreements. Although a high correlation between CBFASL and CBFPET was found, the agreement in absolute CBF values was not sufficient for ASL to be used interchangeably with 15O-water PET.
Highlights
Cerebral blood flow (CBF) measurements are of high clinical value for various brain disorders such as cerebrovascular disorders, brain tumors, and neurodegenerative diseases [1,2,3]
The aim of this study was to evaluate accordance in resting state CBF values based on simultaneously acquired Arterial spin labeling (ASL) (CBFASL) and 15O-water positron emission tomography (PET) (CBFPET) on an integrated PET/MR system and using zero-echo time (ZTE)-based attenuation correction and arterial sampling
This figure illustrates that CBF between ASL (CBFASL) resulted in lower values than CBFPET, which was consistent throughout the whole Grey matter (GM)
Summary
Cerebral blood flow (CBF) measurements are of high clinical value for various brain disorders such as cerebrovascular disorders, brain tumors, and neurodegenerative diseases [1,2,3]. Current reference standard for CBF measurements is positron emission tomography (PET) with 15O-water [3]. 15O-water PET has proven its usefulness in physiological experiments and clinical assessments [4], it is often considered costly and implementations are limited due to the requirement for an on-site cyclotron and an arterial line for blood sampling. Arterial spin labeling (ASL) is a non-invasive magnetic resonance imaging (MRI)-based CBF measurement technique using the patient’s own water molecules in blood as a freely diffusible tracer. A consensus statement was published in 2015 [8] recommending pseudo-continuous ASL as a labeling strategy with 3D segmented read-out applying background suppression [8]
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