Spatial sensitivity and penetration depth of three cerebral oxygenation monitors.

Sonny Gunadi,Ilias Tachtsidis,Clare E Elwell,Terence S Leung

doi:10.1364/boe.5.002896

Abstract

The spatial sensitivities of NIRO-100, ISS Oximeter and TRS-20 cerebral oxygenation monitors are mapped using the local perturbation method to inform on their penetration depths and susceptibilities to superficial contaminations. The results show that TRS-20 has the deepest mean penetration depth and is less sensitive than the other monitors to a localized absorption change in the superficial layer. However, an integration time of more than five seconds is required by the TRS-20 to achieve an acceptable level of signal-to-noise ratio, which is the poorest amongst the monitors. With the exception of NIRO-100 continuous wave method, the monitors are not significantly responsive to layer-wide absorption change that occurs in the superficial layer.

Highlights

The adoption of near infrared spectroscopy (NIRS) in clinics for non-invasive muscle and cerebral oxygenation monitoring has been growing for both adults and infants [1,2,3,4,5,6]
The results showed that all methods were sensitive to localized absorption changes in superficial layers (SPL), especially when these changes occurred in close proximity to the optical source and detector
The oxygenation monitors that we investigated are: (1) the NIRO-100 (Hamamatsu Photonics K.K.) that operates in continuous wave (CW) mode and utilizes SRS to derive the absolute tissue oxygen saturation (StO2) [12, 24]; (2) the ISS Oximeter (Model 96208, ISS Inc.) [10, 14] that operates in the frequency domain (FD) domain mode and applies the multi-distance FD method; and (3) the TRS-20 (Hamamatsu Photonics K.K.) [25, 26] that is based on the TD method

Summary

Introduction

The adoption of near infrared spectroscopy (NIRS) in clinics for non-invasive muscle and cerebral oxygenation monitoring has been growing for both adults and infants [1,2,3,4,5,6]. The cortex lies in a region beneath the scalp, skull and a layer of cerebral spinal fluid (CSF), which are often referred to as the superficial layers (SPL). It has been shown in computer simulations that NIRS can be more sensitive to absorption changes in the SPL than in the deeper regions [7, 8]. The regional sensitivity of the NIRS cerebral oxygenation monitors is investigated This assessment covers both the instrumentation and the adopted NIRS method to derive oxygenation measurements in their respective normal operating modes. The ideal monitor would have 100% sensitivity in the brain and 0% sensitivity in the SPL

Objectives

Methods

Results

Conclusion