IDNE 701: Neuroengineering / Syllabus
In-Class Laboratory · Week 6

Worksheet 6.1: fNIRS Demonstration & Hemodynamic Inversion

Interactive real-time optical data reconstruction: Modified Beer-Lambert Law inversion, differential pathlength calibration, and bedside biomarker extraction ($\text{rSO}_2$ & $\text{FTOE}$) for neonatal hypoxic-ischemic neuromonitoring.

01.

Experimental Protocol & Anatomical Parameters

Define the recording montage, optode geometry, and anatomical subject cohort (Adult Cognitive Task vs. NICU Bedside Neonate).

👶 Grand Challenge 06: Neonatal Bedside Calibration Notes In neonates, the unossified skull and thin scalp ($1.5 - 2.5\,\text{mm}$) allow shorter separations ($d_{\text{SD}} = 15 - 20\,\text{mm}$) to reach the cortical mantle with lower light loss. Calibrated DPF is $\approx 4.4 - 4.8$, compared to adult values of $5.5 - 6.5$.
02.

Real-Time Signal Inversion Sandbox (MBLL Engine)

Simulate or stream dual-wavelength optical intensity signals $I(t)$ at $760\,\text{nm}$ and $850\,\text{nm}$, convert to optical density ($\Delta\text{OD}$), and invert via the extinction coefficient matrix to resolve micromolar changes in $[\text{HbO}]$ and $[\text{HbR}]$.

Δ[HbO] Peak
+0.00 µM
Δ[HbR] Nadir
-0.00 µM
Δ[HbT] (Blood Vol)
+0.00 µM
Estimated rSO₂
68.5%
Extraction (FTOE)
0.28
03.

Spectroscopic Matrix Form & Sensitivity Analysis

Calculate the extinction matrix inverse using standard molar extinction coefficients:
$\varepsilon_{\text{HbO}}(760) = 1.486\,\text{mM}^{-1}\text{cm}^{-1}$, $\varepsilon_{\text{HbR}}(760) = 3.843\,\text{mM}^{-1}\text{cm}^{-1}$
$\varepsilon_{\text{HbO}}(850) = 2.526\,\text{mM}^{-1}\text{cm}^{-1}$, $\varepsilon_{\text{HbR}}(850) = 1.798\,\text{mM}^{-1}\text{cm}^{-1}$

Compute $\det(\mathbf{E})$ and discuss how wavelength selection prevents ill-conditioned matrix inversion.
04.

Bedside Clinical Biomarkers: FTOE & Vascular Autoregulation

Evaluate regional cerebral tissue oxygen saturation ($\text{rSO}_2$) and fractional tissue oxygen extraction ($\text{FTOE}$) for hypoxic-ischemic brain injury.

Clinical Scenario Baseline SpO₂ Measured Cerebral rSO₂ Calculated FTOE Clinical Physiological Interpretation
Normoxic Baseline 98% 71% 0.28 Normal resting cerebral oxygen extraction balance.
Severe Cerebral Ischemia (HIE) 96% 48% 0.50 Severe hypoperfusion; tissue maximally extracting available oxygen.
Mitochondrial Failure / Hyperemia 99% 88% 0.11 Secondary energy failure; neurons dead/incapable of utilizing oxygen.
Explain how whole-body hypothermia ($33.5^\circ\text{C}$) depresses $\text{CMRO}_2$ and why a rising FTOE during rewarming indicates secondary brain injury.
05.

Artifact Rejection & Midterm Design Review Integration

How does today's optical instrumentation lab inform your team's preliminary transducer block diagram for next week's Mid-Semester Design Review?

Specify your algorithm: Short-separation regression ($8\,\text{mm}$ detector), wavelet motion filtering, or adaptive Kalman filtering.
How will optical sensing or multi-modal integration (e.g., fNIRS + EEG, fNIRS + fUS) be presented in your Week 7 presentation deck?