Since fNIRS is not affected by electrical noise or magnetic fields and has few limitations on patient posture during measurements, it can be used to measure brain function in cases where BOLD-fMRI cannot be used, such as on patients being treated with deep brain stimulation (DBS) using a metal electrode.

A: fNIRS Image (overlaid on MRI image) of Essential Tremor Patient Being Treated with DBS

  1. With Electrical Stimulation of DBS OFF (upper graph)
    Oxy-Hb increased significantly and Deoxy-Hb also increased, primarily in the right motor cortex, when a strong tremor occurred in the upper left extremity during a finger-to-finger test.
    (The increase in Deoxy-Hb indicates an abnormal enhanced release of oxygen metabolites.)
  2. With Electrical Stimulation of DBS ON (lower graph)
    The tremor did not occur during the finger-to-finger test and the increase in Deoxy-Hb disappeared.

B: Change in Oxy-Hb, Deoxy-Hb, and Total-Hb Levels During Movement Task

fNIRS Measurement of Change in Active Brain Oxygen Metabolites in Tremor Patient

fNIRS Measurement of Change in Active Brain Oxygen Metabolites in Tremor Patient

Since fNIRS can measure not only Deoxy-Hb, but also changes in Oxy-Hb and blood flow, it is especially well suited to imaging brain function in patients where brain oxygen metabolite activity and hemodynamics are not normal. Currently, BOLD-fMRI is the primary method used to image brain function, but using it in conjunction with fNIRS allows accurately imaging brain function when the patient is sick.

(Data provided by: Mr. Kaoru Sakatani, Department of Neurological Surgery, Nihon University School of Medicine)

Reference: Sakatani, K., (2006) "Imaging Brain-Function of Patients with Encephalopathy: Comparison of fNIRS and fMRI," MEDICAL NOW, No.59: 44-46.

Note: The data shown was acquired using a FOIRE/OMM series model.

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