Noninvasive continuous optical monitoring of absolute cerebral blood flow in critically ill adults.

Lian He,Ramani Balu,Kenneth Abramson,Mamadou Diop,Rickson C Mesquita ,David R Busch ,Olivia Amendolia,W Andrew Kofke ,Keith St Lawrence ,Venkaiah C Kavuri ,Wesley B Baker ,Francis Quattrone,Daniel Milej,Jane Yan Jiang ,Arjun G Yodh

doi:10.1117/1.nph.5.4.045006

Abstract

.We investigate a scheme for noninvasive continuous monitoring of absolute cerebral blood flow (CBF) in adult human patients based on a combination of time-resolved dynamic contrast-enhanced near-infrared spectroscopy (DCE-NIRS) and diffuse correlation spectroscopy (DCS) with semi-infinite head model of photon propogation. Continuous CBF is obtained via calibration of the DCS blood flow index (BFI) with absolute CBF obtained by intermittent intravenous injections of the optical contrast agent indocyanine green. A calibration coefficient () for the CBF is thus determined, permitting conversion of DCS BFI to absolute blood flow units at all other times. A study of patients with acute brain injury () is carried out to ascertain the stability of . The patient-averaged DCS calibration coefficient across multiple monitoring days and multiple patients was determined, and good agreement between the two calibration coefficients measured at different times during single monitoring days was found. The patient-averaged calibration coefficient of was applied to previously measured DCS BFI from similar brain-injured patients; in this case, absolute CBF was underestimated compared with XeCT, an effect we show is primarily due to use of semi-infinite homogeneous models of the head.

Highlights

Brain-injured patients are prone to development of secondary brain injury during the management period, and therapeutic interventions for secondary brain injury hold potential for meaningful impact on long-term patient outcome.[1]
We found that the diffuse correlation spectroscopy (DCS) calibration coefficient, γ, remains constant over at least 4 h of monitoring; good agreement was observed between the two daily calibration coefficients determined from two indocyanine green (ICG) bolus injections administered 4 hours apart [Fig. 6(a)]
We demonstrated the long-term stability of noninvasive absolute cerebral blood flow (CBF) monitoring with DCE-NIRS calibrated DCS

Summary

Introduction

Brain-injured patients are prone to development of secondary brain injury during the management period, and therapeutic interventions for secondary brain injury hold potential for meaningful impact on long-term patient outcome.[1]. Several measurement methods, including PET,[8] MRI,[9] Xe133,10 Xe-CT,[11,12] transcranial Doppler,[13,14] thermal diffusion,[15] jugular bulb oximetry,[16] and EEG17,18 have been utilized to infer or to directly evaluate CBF, but none of these offers truly continuous noninvasive absolute CBF monitoring capabilities at the bedside. The present study explores the potential of a combination of near-infrared (NIR) optical methods for DCS employs NIR light to directly and noninvasively measure local microvascular CBF.[22,23,24,25,26] This optical technique is Neurophotonics

Methods

Results

Discussion

Conclusion