Comparison of time-resolved and continuous-wave near-infrared techniques for measuring cerebral blood flow in piglets.
A primary focus of neurointensive care is monitoring the injured brain to detect harmful events that can impair cerebral blood flow (CBF), resulting in further injury. Since current noninvasive methods used in the clinic can only assess blood flow indirectly, the goal of this research is to develop an optical technique for measuring absolute CBF. A time-resolved near-infrared (TR-NIR) apparatus is built and CBF is determined by a bolus-tracking method using indocyanine green as an intravascular flow tracer. As a first step in the validation of this technique, CBF is measured in newborn piglets to avoid signal contamination from extracerebral tissue. Measurements are acquired under three conditions: normocapnia, hypercapnia, and following carotid occlusion. For comparison, CBF is concurrently measured by a previously developed continuous-wave NIR method. A strong correlation between CBF measurements from the two techniques is revealed with a slope of 0.79±0.06, an intercept of -2.2±2.5 ml∕100 g∕min, and an R2 of 0.810±0.088. Results demonstrate that TR-NIR can measure CBF with reasonable accuracy and is sensitive to flow changes. The discrepancy between the two methods at higher CBF could be caused by differences in depth sensitivities between continuous-wave and time-resolved measurements.
Lawson Health Research Institute, Imaging Program, London, Ontario, Canada N6A 4V2. mdiop@lawsonimaging.ca
Mamadou
M
Diop
Kenneth M
KM
Tichauer
Jonathan T
JT
Elliott
Mark
M
Migueis
Ting-Yim
TY
Lee
Keith
K
St Lawrence
D000818:Animals; D000831:Animals, Newborn; D016893:Carotid Stenosis / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D004396:Coloring Agents; D006439:Hemodynamics; D006935:Hypercapnia / Q000503:physiopathology; D007208:Indocyanine Green; D054023:Lasers, Semiconductor; D055620:Optical Phenomena; D019047:Phantoms, Imaging; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D034421:Sus scrofa
D004396:Coloring Agents; D007208:Indocyanine Green