Impaired cerebrovascular reactivity is associated with recurrent stroke in patients with severe intracranial arterial stenosis: A C02 BOLD fMRI study.

BACKGROUND AND PURPOSE: Severe intracranial atherosclerotic stenosis (SIAS) remains at risk of recurrent ischemic events despite intensive medical management. Exhausted cerebrovascular reserve seems to be associated with higher risk of recurrent stroke. MATERIALS AND METHODS: We used whole brain MRI to estimate basal perfusion using dynamic susceptibility contrast and cerebrovascular reactivity (CVR) to hypercapnic challenge (CO2 inhalation) using BOLD contrast, in 20 patients with symptomatic SIAS (>70%) of the middle cerebral artery (MCA) or the distal internal carotid artery. We studied relationships between individual clinical, biological, radiological baseline characteristics, recurrent ischemic events, basal perfusion parameters (mean transit time, delay, time to peak, cerebral blood flow and volume), and CVR measured in MCA territories (CVRMCA), and reported using laterality indices (LI). RESULTS: Ten patients had an impaired CVR with (|LI| CVRMCA≥0.08). During a mean follow-up of 3.3 years, all recurrent ipsilateral ischemic events occurred within the first year. They were more frequent in impaired CVRMCA group (n=7/10 patients) than in normal CVRMCA group (n=1/10), with different survival curves (log rank, P=0.007). CONCLUSION: Impaired CVR is associated with an increased rate of recurrent stroke in patients with symptomatic SIAS. CVR mapping should be used as a well tolerated method to select higher-risk patients in further therapeutic trials such as endovascular procedures.

Targeting brain metastases with ultrasmall theranostic nanoparticles, a first-in-human trial from an MRI perspective.

The use of radiosensitizing nanoparticles with both imaging and therapeutic properties on the same nano-object is regarded as a major and promising approach to improve the effectiveness of radiotherapy. Here, we report the MRI findings of a phase 1 clinical trial with a single intravenous administration of Gd-based AGuIX nanoparticles, conducted in 15 patients with four types of brain metastases (melanoma, lung, colon, and breast). The nanoparticles were found to accumulate and to increase image contrast in all types of brain metastases with MRI enhancements equivalent to that of a clinically used contrast agent. The presence of nanoparticles in metastases was monitored and quantified with MRI and was noticed up to 1 week after their administration. To take advantage of the radiosensitizing property of the nanoparticles, patients underwent radiotherapy sessions following their administration. This protocol has been extended to a multicentric phase 2 clinical trial including 100 patients.

BOLD fMRI of cerebrovascular reactivity in the middle cerebral artery territory: A 100 volunteers' study.

BACKGROUND AND PURPOSE: The assessment of cerebrovascular reactivity (CVR) has shown promising results for its use in medical diagnosis and prognosis, especially in patients suffering from severe intracranial arterial stenosis. However, its quantification remains uncertain because of a large variability inherent in brain anatomy and in methodological settings. To overcome this variability, we provide lateralization index (LI) values for CVR within the middle cerebral artery territory to detect CVR impairment. MATERIALS AND METHODS: We assessed CVR in 100 volunteers (41 females; 47.52 ± 21.58 years) without cervico-encephalic arterial stenosis using BOLD-fMRI contrast with a block-design hypercapnic challenge. Averaged end-tidal CO2 was used as a physiological regressor for statistical analyses with a general linear model. We measured %BOLD signal-change in segmented gray matter regions of interest in the middle cerebral artery territory (MCA). We calculated a laterality index according to the following formula: LI=(CVRleft-CVRright)/(CVRleft+CVRright). We tested the effects of methodological settings (i.e. hypercapnic gas, gas administration means, MR acquisition and sex) on %BOLD signal change and LI values with analysis of variance. RESULTS: No adverse effects of the hypercapnic challenge were reported. LI values were independent of experimental conditions. Mean LI calculated in MCA territories was 0.016 ± 0.031, giving the lower and upper limits of 95% (m ± 2SD) of this population distribution at]-0.05; 0.08[. CONCLUSION: LI can effectively help us to overcome measurement variabilities. Therefore, it can be used to detect abnormal asymmetries in CVR and identify patients at higher risk of ischemic stroke.