Arterial Pulsations are Present in One Third of the Human Cranial Vascular Volume Penetrated by Near Infrared Light

Abstract

The percentage of cranial vascular volume that undergoes arterial pulsations is estimated by 18 paired measurements in nine healthy volunteers using near infrared spectroscopy (NIRS, 10 Hz sampling frequency, 769 nm). The NIR absorption is decomposed in pulsatile and non-pulsatile components by digital filtering. The time course of absorption changes of these components after sudden intravenous injection of indocyanine-green (ICG) is used to estimate the arterial fraction of vascular volume (f art). Approximately 28% of the vascular volume within the optical field of the NIR spectroscope was arterial. The range of values was 6-43%. Variance of f art was 4.8 times higher between subjects than within subjects, indicating that the variability observed is not due to imprecise estimation but to optode position and subject.