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Comparison of 15oxygen positron emission tomography and near-infrared spectroscopy for measurement of cerebral physiology

Introduction

The gold standard technique for imaging cerebral blood flow (CBF) and metabolism is 15oxygen positron emission tomography (15O PET). Continuous near-infrared spectroscopy (NIRS) has been used to assess adequacy of cerebral oxygenation following stroke, traumatic brain injury and subarachnoid haemorrhage [1], and measurements have been compared with jugular oxygen saturation. In this study we compared NIRS with 15O PET within healthy volunteers.

Methods

Fifteen healthy subjects were recruited (12 male, average age 38 years); PET precluded females of reproductive age. Steady-state 15O PET with arterial sampling was performed to measure CBF, cerebral metabolic rate of oxygen (CMRO2), oxygen extraction ratio (OEF) and cerebral blood volume (CBV) [2]. Simultaneously, NIRS data were collected using a Hamamatsu NIRO 200 with sensors on either side of the forehead. NIRS OEF was calculated from tissue oxygen saturation, SaO2 and an assumed arterial/venous blood volume ratio of 30/70 [3].

Results

The frontal region 15O PET CBF, CMRO2, OEF and CBV were mean (SD) 44.9 (10) ml/100 ml/minute, 158.7 (24.7) μmol/100 ml/minute, 45.8 (7.3)%, and 2.8 (0.8) ml respectively, and there was no relationship between NIRS and 15O PET (Figure 1).

Figure 1
figure1

Linear correlation between NIRS and PET OEF.

Conclusion

We found no relationship between NIRS and baseline physiology as determined by 15O PET. Further studies should assess the dynamic response of NIRS to a measured change in physiology in patients. Further confines of NIRS include its limited and focal brain coverage.

References

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Simpson, J., Sudhan, N., Hare, H. et al. Comparison of 15oxygen positron emission tomography and near-infrared spectroscopy for measurement of cerebral physiology. Crit Care 19, P445 (2015). https://doi.org/10.1186/cc14525

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Keywords

  • Traumatic Brain Injury
  • Cerebral Blood Flow
  • Cerebral Blood Volume
  • Extraction Ratio
  • Cerebral Oxygenation