Calibrated MRI to Evaluate Cerebral Hemodynamics in Patients with an Internal Carotid Artery Occlusion

Abstract

The purpose of this study was to assess whether calibrated magnetic resonance imaging (MRI) can identify regional variances in cerebral hemodynamics caused by vascular disease. For this, arterial spin labeling (ASL)/blood oxygen level-dependent (BOLD) MRI was performed in 11 patients (65 ± 7 years) and 14 controls (66 ± 4 years). Cerebral blood flow (CBF), ASL cerebrovascular reactivity (CVR), BOLD CVR, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO 2 ) were evaluated. The CBF was 34 ± 5 and 36 ± 11 mL/100 g per minute in the ipsilateral middle cerebral artery (MCA) territory of the patients and the controls. Arterial spin labeling CVR was 44 ± 20 and 53 ± 10% per 10 mm Hg ΔEtCO 2 in patients and controls. The BOLD CVR was lower in the patients compared with the controls (1.3 ± 0.8 versus 2.2 ± 0.4% per 10 mm Hg ΔEtCO 2 , P o 0.01). The OEF was 41 ± 8% and 38 ± 6%, and the CMRO 2 was 116 ± 39 and 111 ± 40 μmol/100 g per minute in the patients and the controls. The BOLD CVR was lower in the ipsilateral than in the contralateral MCA territory of the patients (1.2 ± 0.6 versus 1.6 ± 0.5% per 10 mmHg ΔEtCO 2 , P o 0.01). Analysis was hampered in three patients due to delayed arrival time. Thus, regional hemodynamic impairment was identified with calibrated MRI. Delayed arrival artifacts limited the interpretation of the images in some patients.

Modeling of dynamic cerebrovascular reactivity to spontaneous and externally induced CO2 fluctuations in the human brain using BOLD-fMRI

“…This line of research yields promise, including the clinical setting, as it may lead to protocols which are easier to implement and applicable to a potentially wider class of patient populations with disorders associated with cerebrovascular dysfunction. Such disorders include arterial stenosis (Mandell et al, 2008b) and occlusion (De Vis et al, 2015), enhanced risk of stroke (Gur et al, 1996;Markus and Cullinane, 2001;Silvestrini et al, 2000), stenoocclusive diseases such as Moyamoya disease (Donahue et al, 2013;Mikulis et al, 2005), small-vessel diseases (Conklin et al, 2011(Conklin et al, , 2010 and Alzheimer's disease (Marmarelis et al, 2016(Marmarelis et al, , 2013Silvestrini et al, 2011). Beyond cerebrovascular diseases, we speculate that modeling dCVR within structures involved in central chemoreception could provide valuable insight towards understanding and treating diseases associated with respiratory control.…”

Reproducibility of a ramping protocol to measure cerebral vascular reactivity using functional magnetic resonance imaging

“…To date, most studies using a ramp protocol with SGD have been conducted specifically to test different physiological CVR relationships (i.e., linear, sigmoidal, etc.) (Bhogal et al, ) in order to better describe CVR (Bhogal et al, ; Sobczyk et al, ) or, simply, the utility in diagnosing steno‐occlusive diseases (De Vis et al, , ; Duffin et al, ). To our knowledge, no studies have specifically investigated, nor reported, the reproducibility of a ramp sequence to assess changes in CVR.…”

“…The most common method of applying SGD during CVR studies is by initiating brief square wave "step" increases (5-10 mmHg) in P et CO 2 above baseline levels (De Vis et al, 2015;Ellis et al, 2016;Han et al, 2011;Mark et al, 2010;Poublanc et al, 2015;Sobczyk et al, 2016). Recently, we demonstrated that square wave "step" increases are reliable in healthy adults when repeated within the same visit, as well as between visits (Dengel et al, 2016).…”

Simultaneous multi‐slice (SMS) acquisition enhances the sensitivity of hemodynamic mapping using gas challenges

“…The assessment of brain hemodynamic function is of significant value in pathological conditions, such as steno‐occlusive conditions, stroke, brain tumor and dementia, and in the correct interpretation of the functional magnetic resonance imaging (fMRI) signal . Hemodynamic mapping using gas challenges has received increasing attention in recent years, as a result of several advancements, including the increasing availability of breathing apparatus, development of a more comfortable breathing paradigm and more sophisticated analysis tools .…”