Correlation Between Noninvasive Blood Vessel Functionality Parameters and Cerebral Hemodynamics in Neurocritical Care Patients

Inclusion Criteria: Subjects who meet all the following inclusion criteria may be included: 1. Adults (\> 18 years of age); 2. Able and willing to provide written informed consent for participation by self or legally authorized representatives. 3. Clinical diagnosis of traumatic brain injury (TBI), brain hemorrhage, brain tumor, neurotrauma (including closed head injuries, penetrating head injuries, or other forms of neurotrauma), hemorrhage (intracerebral or subarachnoid), or stroke. 4. Continuous Blood Pressure Monitoring: Patients must have continuous blood pressure monitoring in place during the study period, obtained from an arterial line. This criterion ensures that we have real-time data on mean arterial pressure (MAP) and systolic pressure (SBP). 5. Intracranial Pressure (ICP) Monitoring: Patients must have intracranial pressure (ICP) monitoring in place during the study period. This criterion ensures that we can assess the correlation between our blood vessel functionality parameters (VDC, VR, and VRx) and ICP, a key indicator of intracranial dynamics. Exclusion Criteria: 1. Subjects who meet any of the following exclusion criteria will be excluded: 2. Expected to be at increased risk due to study participation (e.g. due to hemodynamic instability), in the medical opinion of an investigator; 3. Pregnant as determined per site standard practice; 4. Previously participated in this study, or are enrolled in another research study that could be expected to interfere with participation, in the opinion of the investigator; 5. Require or are anticipated to require emergent medical care in which study participation may reasonably delay his/her medical care or increase risk or unfavorable outcome, in the opinion of the investigator; 6. Allergy to adhesive tape; 7. Ongoing photodynamic therapy.