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Table 1 Clinical assessment methodologies for the cerebral circulation

From: Regulation of the cerebral circulation: bedside assessment and clinical implications

Method Principle Global or local CBF assessment Robustness Invasive Bedside Continuous Advantage Disadvantage
TCD [33] Doppler principle Global (vascular territory) Fair No Yes Yes High-frequency signal Signal easily lost. Flow velocity assessment only
NIRS [34] Absorbance of oxygenated and deoxygenated haemoglobin Local Good No Yes Yes Easy application Uncertain intracranial contribution to signal
PBTO2 [37] Clark electrode Local Excellent Yes Yes Yes Robust Local
LDF [36] Doppler principle Local Excellent Yes Yes Yes Assessment of microcirculation Unknown biological zero
Thermal diffusion [35] Thermal diffusion Local Excellent Yes Yes Yes Absolute CBF Frequent calibrations
Duplex neck US [106] Doppler principle Global Poor No Potentially No Absolute and global CBF Semi-continuous
CT [107] Time-dependent attenuation of iodine IV contrast bolus (perfusion CT) or Xe gas Global and local Excellent No Potentially No Global and regional CBF Bulky and intermittent
PET [108] Radioactive tracers emit positrons dependent on perfusion Global and local Excellent Minimal (venous access) No No Regional CBF and metabolism Radiation, requires a cyclotron
MRI [109] Perfusion-dependent decrease in T2 signal with gadolinium Global and local Excellent Minimal (IV access) or no for arterial spin labelling technique No No Absolute, regional and global CBF Time-consuming, expensive, difficult to assess critically ill patients
  1. CBF cerebral blood flow, CT computerised tomography, IV intravenous, LDF laser Doppler flowmetry, MRI magnetic resonance imaging, NIRS near-infrared spectroscopy, P B TO 2 pressure of brain tissue oxygen, PET positron emission tomography, TCD transcranial Doppler, US ultrasound