(a) Schematic diagram of the multichannel NIRS system. Diagram includes the flow phantom which is described in Sec. III C. The dashed line represents the electronic control of the multiplexer. (b) Schematic diagram of the multiplexer showing four of eight detection channels. Light from the detection optode passes through one shutter before being collected by a multibranched fiber-optic bundle connected to the entrance of the spectrometer.
Time course of the area under the whole-spectrum recorded by multiple detection channels. For clarity, only five of the eight channels are presented. Light intensity across optodes was intentionally varied to distinguish their respective signals. The intensity level in channel three is typical of the light intensity measured in an animal experiment. The stability of the recorded signals indicates negligible cross-talk between detection channels.
Average CBF values from one piglet data set plotted as a function of the sampling interval (solid line, open circles). The dashed line represents the CBF value determined from the original ICG concentration curve acquired with a sampling interval of 200 ms.
Brain tissue ICG concentration curves obtained from detection optodes 1–4 before (a) and after (b) ET-1 injection. Curves were measured following an i.v. injection of 0.1 mg/kg ICG in 1 ml of sterile water. The reduction in the peak height of the ICG curve for optode 1 after ET-1 injection reflects the reduction in CBF caused by the drug. Shown in the top right hand side of (a) is a cartoon of a piglet head showing the location of the four detection optodes (labeled 1–4) relative to the emission optode (labeled E). The emission-detector distance was 3 cm in all cases. The approximate position of the ET-1 injection site is represented by the mark between the emission optode and detection optode 1.
Average CBF values determined by the multichannel NIRS system before (pre) and after (post) intracerebral injection of ET-1. signifies a statistically significant difference between pre and postinjection CBF measurements .
Computed tomography perfusion maps of CBF from one experiment before (top row) and after (bottom row) intracerebral ET-1 microinjection. The arrows indicate the location of the injury caused by ET-1 injection.
Comparison of CBF values measured by NIRS and CT perfusion. (a) CBF from NIRS optode 1 compared to average CBF determined in the injured region defined in the CT perfusion images. (b) CBF from NIRS optode 4 and average CBF for the same brain region defined in the CT perfusion images (slices 5–7). The labels pre and post refer to CBF before and after ET-1 injection, respectively. signifies a statistically significant difference between pre and postinjection CBF measurements .
(a) Relative ICG concentration curves measured by eight optodes. The positions of the detection optodes relative to the flow target (glass ball) are shown in the schematic diagram in the top right-hand corner. The distance between the emission and each detection optode was 3 cm.
Effect of increasing the sampling rate on CBF. The values are the difference in CBF between the original data (sampled at 200 ms) and the resampled data, respectively.
Article metrics loading...
Full text loading...