Interferometric NIR ICP Sensing via Cerebral Blood Flow Waveforms
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Solution Overview
Problem
Existing near infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) methods for monitoring intracranial pressure (ICP) are invasive, bulky, slow, and rely on assumptions that disregard phase information, leading to inaccurate and cumbersome measurements.
Innovation Solution
An interferometric near infrared spectroscopy (iNIRS) system that combines NIRS and DCS to non-invasively measure intracranial pressure by aligning cerebral and extracerebral blood flow waveforms, using a light source with wavelength sweeping and interferometric optical detectors to process combined light signals for accurate ICP determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional NIRS and DCS methods are used to measure intracranial pressure, then ICP monitoring can be performed, but the measurement process becomes invasive, bulky, and slow
Solution Approach 1:
The patent combines NIRS and DCS into a single integrated system that uses a common light source and detector array. The system simultaneously measures both optical absorption (NIRS) and temporal light fluctuations (DCS) to extract multiple physiological parameters including ICP, blood flow, and oxygenation from a single measurement session, eliminating the need for separate invasive devices.
Solution Approach 2:
The patent replaces invasive mechanical pressure sensors with non-invasive optical measurement. By using near-infrared light to probe brain tissue and analyzing the scattered light properties, the system derives ICP information optically without requiring physical insertion of catheters or pressure transducers into the cranial cavity.
2Measurement precision
If DCS is used to extract ICP information, then ICP data can be obtained, but the process requires heavy averaging making it slow
Solution Approach 1:
The patent implements continuous ICP monitoring by maintaining constant optical illumination and detection. The system continuously tracks temporal light fluctuations and不断更新 the ICP measurements in real-time without requiring repeated measurements or heavy signal averaging, enabling dynamic monitoring of ICP changes as they occur.
Solution Approach 2:
The patent performs preliminary calibration and characterization of tissue optical properties before ICP measurement. By pre-determining the optical characteristics of the specific tissue being monitored, the system can directly interpret DCS signals without requiring extensive real-time averaging, thus accelerating the ICP extraction process.
3Ease of operation
If DCS and NIRS rely only on light intensities, then measurements can be obtained, but phase information is rejected leading to additional assumptions
Solution Approach 1:
The patent transitions from one-dimensional intensity-only measurements to two-dimensional measurements that include both intensity and phase information. By utilizing optical frequency domain reflectometry to detect phase changes in the reflected light, the system extracts additional physiological information such as blood flow velocity and tissue elasticity without sacrificing measurement simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables non-invasive, rapid, and accurate measurement of intracranial pressure by processing combined light signals to align and compare cerebral and extracerebral blood flow waveforms, improving measurement precision and reducing invasiveness.
Implementation Method 1
Radiation at NIRS wavelengths is less easily absorbed by human skin (and also bones) than visible light, and so NIRS radiation may penetrate both skin and skull, and penetrate into brain tissue
Implementation Method 2
The optical detector is arranged to combine the sample light with the reference light to provide combined light signals comprising one or more components at a beat frequency between sample light and reference light
Implementation Method 3
Diffuse correlation spectroscopy (DCS) can be used to noninvasively monitor blood flow in the brain by measuring temporal fluctuations of the light remitted from the sample
Data Source
AI summary
An aspect of the disclosure provides a non-invasive intracranial pressure sensing apparatus comprising an interferometric near infrared spectroscopy, iNIRS system, the iNIRS system comprising: a light emitting arrangement comprising: a light source configured to emit light; a sample delivery channel coupled to the light source and arranged to be coupled to the subject's scalp to direct light from the light source towards the subject's brain tissue; and a reference channel coupled to the light source for receiving light therefrom; a light detecting arrangement configured to be coupled to the subject's scalp and the light emitting arrangement, the light detecting arrangement comprising an interferometric optical detector configured to receive: (i) reference light from the reference channel, and (ii) sample light from the subject's brain, the sample light comprising light emitted from the light source; wherein the optical detector is arranged to combine the sample light with the reference light to provide combined light signals comprising one or more components at a beat frequency between sample light and reference light; and wherein the sensing apparatus comprises a controller configured to process data indicative of the combined light signals to determine an indication of intracranial blood pressure for the subject based on at least one property of a pulsatile waveform of one or more identified pulses of blood flow through the subject's brain.