Loss of labelling efficiency caused by carotid stent in pseudocontinuous arterial spin labelling perfusion study

Effect of remimazolam versus propofol for the induction of general anesthesia on cerebral blood flow and oxygen saturation in elderly patients undergoing carotid endarterectomy

BACKGROUND

This study was conducted to investigate the effects and safety of remimazolam versus propofol on cerebral oxygen saturation and cerebral hemodynamics during the induction of general anesthesia in patients receiving carotid endarterectomy (CEA), so as to provide theoretical basis for better clinical application of remimazolam.

METHODS

Forty-three patients (60-75 years old) with carotid artery stenosis (carotid artery stenosis greater than 70%) were randomly divided into the remimazolam group (R group) and the propofol group (P group). Anesthesia was induced with remimazolam (0.3 mg/kg) or propofol (1.5-2 mg/kg) individually. At time of admission (T0), post-anesthesia induction (T1), consciousness disappears (T2), 1 min after loss of consciousness (T3), 2 min after loss of consciousness (T4) and pre-endotracheal intubation (T5), measurement in patients with regional cerebral oxygen saturation (SrO₂), average blood flow velocity (Vm), resistance index (RI), mean arterial pressure (MAP), heart rate (HR) and cardiac index (CI) were recorded.

RESULTS

SrO₂ increased significantly in both groups after induction of anesthesia compared with baseline (P < 0.05) and decreased after loss of consciousness (P < 0.05). There was no difference in the mean value of the relative changes in SrO₂ between the groups. Meanwhile, the Vm, RI, HR and CI of each time point between two groups showed no statistically significant difference (P > 0.05) while MAP in group P at T5 was lower than that in group R individually(P < 0.05). In each group, Vm, HR, CI and MAP at T2-T5 were all significantly reduced compared with T1, with statistically differences(P < 0.05). Specifically, there was no difference of RI at each time between or within groups(P > 0.05).

CONCLUSIONS

Our study revealed that remimazolam can be administered safely and effectively during the induction of general anesthesia for carotid endarterectomy in elder population and it demonstrated superiority in hemodynamic changes compared with propofol.

CLINICAL TRIAL REGISTRATION

This trial was retrospectively registered with the Chinese Clinical Trial Registry.

REGISTRATION NUMBER

ChiCTR2300070370. Date of registration: April 11, 2023.

Current state and guidance on arterial spin labeling perfusion MRI in clinical neuroimaging

This article focuses on clinical applications of arterial spin labeling (ASL) and is part of a wider effort from the International Society for Magnetic Resonance in Medicine (ISMRM) Perfusion Study Group to update and expand on the recommendations provided in the 2015 ASL consensus paper. Although the 2015 consensus paper provided general guidelines for clinical applications of ASL MRI, there was a lack of guidance on disease-specific parameters. Since that time, the clinical availability and clinical demand for ASL MRI has increased. This position paper provides guidance on using ASL in specific clinical scenarios, including acute ischemic stroke and steno-occlusive disease, arteriovenous malformations and fistulas, brain tumors, neurodegenerative disease, seizures/epilepsy, and pediatric neuroradiology applications, focusing on disease-specific considerations for sequence optimization and interpretation. We present several neuroradiological applications in which ASL provides unique information essential for making the diagnosis. This guidance is intended for anyone interested in using ASL in a routine clinical setting (i.e., on a single-subject basis rather than in cohort studies) building on the previous ASL consensus review.

Intracranial vascular feature changes in time of flight MR angiography in patients undergoing carotid revascularization surgery

PURPOSE

To characterize the intracranial vascular features extracted from time of flight (TOF) images and their changes from baseline to follow-up in patients undergoing carotid revascularization, using arterial spin labeling (ASL) cerebral blood flow (CBF) measurement as a reference.

METHODS

In this retrospective study, brain TOF and ASL images of 99 subjects, acquired before, within 48 h, and/or 6 months after, carotid revascularization surgery were analyzed. TOF images were analyzed using a custom software (iCafe) to quantify intracranial vascular features, including total vessel length, total vessel volume, and number of branches. Mean whole-brain CBF was calculated from ASL images. ASL scans showing low ASL signal in the entire flow territory of an internal carotid artery (ICA), which may be caused by labeling failure, were excluded. Changes and correlations between time points were analyzed separately for TOF intracranial vascular features and ASL CBF.

RESULTS

Similar to ASL CBF, TOF vascular features (i.e. total vessel length, total vessel volume and number of branches) increased dramatically from baseline to post-surgery, then returned to a level slightly higher than the baseline in long-term follow-up (All P < 0.05). Correlation between time points was observed for all three TOF vascular features but not for ASL CBF.

CONCLUSION

Intracranial vascular features, including total vessel length, total vessel volume and number of branches, extracted from TOF images are useful in detecting brain blood flow changes induced by carotid revascularization surgery.

Increased variability of watershed areas in patients with high-grade carotid stenosis

PURPOSE

Watershed areas (WSAs) of the brain are most susceptible to acute hypoperfusion due to their peripheral location between vascular territories. Additionally, chronic WSA-related vascular processes underlie cognitive decline especially in patients with cerebral hemodynamic compromise. Despite of high relevance for both clinical diagnostics and research, individual in vivo WSA definition is fairly limited to date. Thus, this study proposes a standardized segmentation approach to delineate individual WSAs by use of time-to-peak (TTP) maps and investigates spatial variability of individual WSAs.

METHODS

We defined individual watershed masks based on relative TTP increases in 30 healthy elderly persons and 28 patients with unilateral, high-grade carotid stenosis, being at risk for watershed-related hemodynamic impairment. Determined WSA location was confirmed by an arterial transit time atlas and individual super-selective arterial spin labeling. We compared spatial variability of WSA probability maps between groups and assessed TTP differences between hemispheres in individual and group-average watershed locations.

RESULTS

Patients showed significantly higher spatial variability of WSAs than healthy controls. Perfusion on the side of the stenosis was delayed within individual watershed masks as compared to a watershed template derived from controls, being independent from the grade of the stenosis and collateralization status of the circle of Willis.

CONCLUSION

Results demonstrate feasibility of individual WSA delineation by TTP maps in healthy elderly and carotid stenosis patients. Data indicate necessity of individual segmentation approaches especially in patients with hemodynamic compromise to detect critical regions of impaired hemodynamics.