Frequency-Domain fNIRS System Modulation for Spatial Resolution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Functional near-infrared spectroscopy (fNIRS) systems, particularly frequency-domain (FD) fNIRS, face challenges in achieving enhanced measurement capabilities while maintaining cost-effectiveness and simplicity, with limitations in spatial resolution and signal-to-noise ratio due to complex hardware requirements and scattering issues in biological tissues.
Innovation Solution
A system comprising multiple radiation sources and detectors with modulated wavelengths and frequencies, along with a controller and analyzer, to generate and analyze digitized signals for amplitude and phase information, reducing noise and complexity through time encoding and amplitude modulation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency-domain fNIRS systems use multiple radiation sources and detectors with modulation techniques, then measurement precision and spatial resolution are improved, but device complexity increases
Solution Approach 1:
The patent applies periodic modulation to radiation sources at distinct frequencies, allowing multiplexed illumination of multiple tissue locations. This periodic action enables the system to encode spatial information in frequency domain, achieving improved spatial resolution and measurement precision without requiring physically separate detectors for each location, thereby reducing hardware complexity
Solution Approach 2:
The patent transitions from spatial domain to frequency domain by modulating radiation sources at different frequencies. This dimensionality change allows multiple spatial measurements to be encoded in the frequency spectrum, enabling the system to achieve high spatial resolution through frequency analysis rather than through complex spatial arrangement of multiple detectors
2Measurement precision
If frequency-domain fNIRS systems use multiple radiation sources and detectors with modulation techniques, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
By modulating radiation sources periodically at distinct frequencies and using synchronous detection, the system achieves frequency-based signal separation. This periodic modulation allows the detection of weak optical signals from tissue by encoding them at known frequencies, enabling noise rejection through frequency filtering and improving signal-to-noise ratio without requiring complex amplification or shielding hardware
Solution Approach 2:
The patent introduces frequency modulation as an intermediary mechanism between the radiation source and the tissue. This frequency encoding acts as a mediator that carries spatial and temporal information through the tissue, allowing the detection system to recover multiple measurement channels from a single detector through frequency-domain demodulation, thereby improving signal-to-noise ratio while minimizing hardware complexity
3Loss of information
If radiation sources are modulated at different frequencies, then amplitude and phase information can be determined, but device complexity increases
Solution Approach 1:
The patent uses periodic modulation of radiation sources at distinct frequencies to encode both amplitude and phase information of light propagation through tissue. By detecting the modulated signals and performing frequency-domain analysis, the system recovers both magnitude and phase components, providing complete characterization of tissue optical properties without requiring complex time-resolved measurement systems
Solution Approach 2:
The patent changes the frequency parameter of radiation sources to encode multiple measurement channels. By varying the modulation frequency of each radiation source, the system multiplexes multiple spatial locations onto a single detection channel, allowing recovery of amplitude and phase information through frequency-selective demodulation while reducing the number of physical detectors needed
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
The system enhances the spatial resolution and signal-to-noise ratio of fNIRS measurements, allowing for deeper tissue penetration and improved neural activity decoding without increasing cost or complexity, thereby improving functional imaging capabilities.
Implementation Method 1
The photo-sensitive elements are configured to receive scattered radiation resulting from the first and second beams and to generate first or second detection signals respective to the first or second detectors
Implementation Method 2
The first and second detectors each comprise a photo-sensitive element, a Faraday shielding enclosure, a signal amplifier, and a frequency mixer
Data Source
AI summary
A system includes first and second radiation sources, first and second detectors, a signal digitizer, a controller, and an analyzer. The first and second radiation sources generate respective first and second beams of radiation to irradiate a target. The first beam and second beams each include a first wavelength operated at a first modulation frequency and a second wavelength operated at a second modulation frequency. The first and second detectors each include a photo-sensitive element that generate first or second detection signals, a Faraday shielding enclosure, a signal amplifier, and a frequency mixer to frequency-adjust the first or second detection signals. The controller provides timing information to inform an activation scheme of the first and second radiation sources and corresponding radiation detection events at the first and second detectors. The analyzer analyzes the first and second detection signals and determines at least amplitude and phase information of the scattered radiation.