Real-time phase-contrast MRI can be used to quantify cerebrovascular reserve capacity – a comparative study to neurovascular ultrasound in healthy subjects

Cerebrovascular reserve capacity (CVRC) is reduced in patients with advanced large artery atherosclerosis (LAA) and represents a risk factor for ischemic stroke. Aim of this study was to compare CVRC testing derived by neurovascular ultrasound (nvUS) and real-time phase-contrast MRI (RT-PC MRI). In this study 25 subjects (age 33±13 years) without any LAA were first investigated with nvUS followed by RT-PC MRI performing a standardized hyperventilation-apnea-test. CVRC was determined in the medial (MCA) and posterior cerebral artery (PCA) using transtemporal nvUS and RT-PC MRI at 25 fps temporal resolution, 0.8×0.8 mm 2 in plane resolution and a slice thickness of 6 mm during free breathing. For statistical analysis a paired t -test and a pearson correlation were used at α=0.05. Overall, peak-systolic velocities (PSV) and end-diastolic velocities (EDV) showed lower values for the RT-PC MRI as compared to nvUS. The PSV-decrease during hyperventilation relative to baseline was higher in RT-PC MRI measurements (22% (MCA) and 26% (PCA) for nvUS vs. 34% (MCA) and 39% (PCA) for RT-PC MRI, p<0.001), while the relative PSV-increase from hyperventilation to apnea was comparable between both modalities with a mean difference of <10% (62% (MCA) and 78% (PCA) for nvUS vs. 70% (MCA) and 84% (PCA) for RT-PC MRI, p=0.171 for MCA and p=0.324 for PCA). Both nvUS and RT-PC MRI based CVRC measurements showed reliable de- and increases in PSV during the standardized breathing protocol. RT-PC MRI represents a promising technique to determine CVRC in various intracranial vessels. • Real-time phase-contrast MRI (RT-PC MRI) can be used to examine cerebrovascular-reserve-capacity (CVRC) during a standardized breathing protocol in various intracranial arteries. • Compared to neurovascular ultrasound (nvUS) relative decrease of peak-systolic velocity (PSV) during hyperventilation was higher for RT-PC MRI derived measurements. • Relative increase of PSV during apnea was comparable between RT-PC MRI and nvUS with a mean difference of <10%. • Dynamic changes of intracranial blood flow are well detectable using RT-PC MRI. • Quantitative blood flow velocities derived by RT-PC MRI are lower compared to nvUS derived blood flow velocities because of partial volume effects and a lower temporal resolution of RT-PC MRI.