Quantifying cerebral blood arrival times using hypoxia-mediated arterial BOLD contrast

Area of Science:

• Neuroimaging
• Cerebrovascular Physiology
• Medical Physics

Background:

• Cerebral blood arrival and tissue transit times are crucial for assessing brain perfusion and collateral flow.
• Current methods may not fully capture the nuances of blood flow dynamics in various brain tissues.

Purpose of the Study:

• To introduce and validate the Step Hemoglobin re-Oxygenation Contrast Stimulus (SHOCS) method for quantifying cerebral blood arrival and transit times.
• To assess the utility of SHOCS in differentiating between gray and white matter perfusion and in a patient with carotid artery occlusion.

Main Methods:

• SHOCS utilizes controlled changes in arterial hemoglobin saturation via respiratory challenges to generate BOLD signal contrast.
• Carpet plot analysis is employed to measure signal onset (blood arrival), global transit time (gTT), and relative blood volume.
• The method was tested on 12 healthy subjects and one patient with unilateral carotid artery occlusion.

Main Results:

• Average cortical gray matter and deep white matter onset times were 1.1 ± 0.4 s and 1.9 ± 0.6 s, respectively.
• The average whole-brain gTT was 4.5 ± 0.9 s, with a 1.7-fold higher SHOCS response in gray versus white matter.
• In the patient with carotid artery occlusion, SHOCS revealed prolonged ipsilateral signal onset, indicating impaired perfusion.

Conclusions:

• SHOCS is a novel and effective method for quantifying cerebral blood arrival and transit times.
• The technique provides clinically meaningful insights into tissue perfusion efficiency and collateral blood flow status.
• SHOCS has potential applications in evaluating patients with steno-occlusive vascular disease and assessing cerebrovascular reserve.