Cerebrovascular reactivity mapping without gas challenges

Abstract

Cerebrovascular reactivity (CVR), the ability of cerebral vessels to dilate or constrict, has been shown to provide valuable information in the diagnosis and treatment evaluation of patients with various cerebrovascular conditions. CVR mapping is typically performed using hypercapnic gas inhalation as a vasoactive challenge while collecting BOLD images, but the inherent need of gas inhalation and the associated apparatus setup present a practical obstacle in applying it in routine clinical use. Therefore, we aimed to develop a new method to map CVR using resting-state BOLD data without the need of gas inhalation. This approach exploits the natural variation in respiration and measures its influence on BOLD MRI signal. In this work, we first identified a surrogate of the arterial CO2 fluctuation during spontaneous breathing from the global BOLD signal. Second, we tested the feasibility and reproducibility of the proposed approach to use the above-mentioned surrogate as a regressor to estimate voxel-wise CVR. Third, we validated the “resting-state CVR map” with a conventional CVR map obtained with hypercapnic gas inhalation in healthy volunteers. Finally, we tested the utility of this new approach in detecting abnormal CVR in a group of patients with Moyamoya disease, and again validated the results using the conventional gas inhalation method. Our results showed that global BOLD signal fluctuation in the frequency range of 0.02–0.04 Hz contains the most prominent contribution from natural variation in arterial CO2. The CVR map calculated using this signal as a regressor is reproducible across runs (ICC=0.91±0.06), and manifests a strong spatial correlation with results measured with a conventional hypercapnia-based method in healthy subjects (r=0.88, p<0.001). We also found that resting-state CVR was able to identify vasodilatory deficit in patients with steno-occlusive disease, the spatial pattern of which matches that obtained using the conventional gas method (r=0.71±0.18). These results suggest that CVR obtained with resting-state BOLD may be a useful alternative in detecting vascular deficits in clinical applications when gas challenge is not feasible.

Sildenafil Improves Vascular and Metabolic Function in Patients with Alzheimer’s Disease

“…Our experience with the face mask method was that the small size of the head coil sometimes limits the placement of the face mask on the subject. Our group is actively exploring non-gas methods to measure cerebrovascular reactivity [83]. A third limitation of this study is that the metabolic parameters, i.e., OEF and CMRO 2 , are global only, without spatial resolution.…”

ASL‐MRICloud: An online tool for the processing of ASL MRI data

“…Figure A shows an example of the Abnorm index map in a patient with Moyamoya disease, in whom both hypoperfusion (due to ischemia) and apparent hyperperfusion (due to delayed bolus clearance) are present. Figure B summarizes the volume ratio of abnormal perfusion region to whole brain from seven Moyamoya patients, where data were acquired in a previous published study …”

“…The algorithm to identify abnormal perfusion territories was tested using ASL data collected from patients with a steno‐occlusive disease, Moyamoya disease . Seven patients (average age 39 ± 10 years, one male and six females) were studied using the following imaging parameters: 2D multi‐slice acquisition, labeling duration = 1650 ms, PLD = 1525 ms, TR/TE = 4260 ms/14 ms, FOV = 240 × 240 × 145.5 mm 3 , voxel size 3 × 3 × 5 mm 3 , 29 axial slices without gap, 40 pairs of control and label images, scan duration = 5 min 40 s.…”

Limitations of Resting-State Functional MR Imaging in the Setting of Focal Brain Lesions

“…47,48 A recent study proposed a different resting-state CVR map which exploits the natural variation in respiration to map CVR using resting state BOLD data. 51 Because of its easy implementation and less stringent requirements for patient compliance, rsfMRI has been attracting wide attention for use as a preoperative mapping tool. 52,53 However, rsfMRI also suffers from similar important clinical limitations of false negative BOLD signals due to brain-tumor related NVU; 54–56 thus, to use rsfMRI as a reliable pre-surgical tool, it becomes all the more important to study NVU in cases of focal resectable brain lesions such as tumors to evaluate its effects on rsfMRI.…”