Edinburgh Imaging

Cerebrovascular-reactivity (CVR)

Cerebrovascular reactivity is the change in cerebral blood flow in response to a vaso-active stimulus.

  • CVR requires a subject to inhale a mixture of air & carbon dioxide.
  • Inhaling this mixture induces hypercapnia & causes vasodilation.
  • It is a well-documented method of measuring CVR.


  • To determine if various imaging methods are sensitive & practical enough to use in early phase clinical trials of interventions to prevent progressive small vessel disease.
  • Patient data pertaining to CVR is currently limited.
  • Our research is designed to:
    • Determine feasibility & to compare CVR with retinal vasoreactivity & measures of peripheral vascular health
    • Provide proof of principle
    • Determine sample size requirements prior to phase 2 trials & mechanistic studies.


  • Prior to MR scanning, the subject undergoes retinal imaging, both before & after the induced hypercapnia.
  • Retinal imaging allows measurement of retinal vascular reactivity & can be correlated with CVR.
  • During the MR scan which follows, the subject undergoes hypercapnia again.
  • MR allows measurement of CVR in grey matter, white matter, & in white matter hyperintensities.
  • Blood Oxygen Level Dependent (BOLD) sequences allow measurement of the CVR.
  • The subject also undergoes structural imaging, plus flow sensitive scans of the cerebral aqueduct, venous sinuses & carotid arteries.
  • The subject then undergoes Doppler ultrasound in order to capture flow measurements of the internal & common carotid arteries.
  • Finally, pulse wave analysis test & pulse wave velocity measurement are carried out using the SphygmoCor system.
  • Subjects are being scanned on both the 1.5T MR scanner at the Edinburgh Imaging Facility WGH & the 3T MR scanner at the Edinburgh Imaging Facility RIE.