Periodic Deoxyhemoglobin BOLD Mapping for Vascular Tissue Characterization
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Solution Overview
Problem
Existing perfusion MRI methods using deoxyhemoglobin as a contrast agent face challenges due to the complexity of the default mode network (DMN) patterns, which complicates analysis and limits understanding of vascular physiology and brain function in non-DMN voxels, and there is a lack of knowledge about vasculature in these regions.
Innovation Solution
Implementing a periodic deoxyhemoglobin signal, such as a sinusoidal pattern, by controlling arterial oxygen partial pressure (PaO2) and maintaining normocapnia, while using magnetic resonance imaging to measure and compare the induced signal with the brain's magnetic response, allowing for voxel-specific tissue characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If deoxyhemoglobin concentration is measured using BOLD MRI to assess blood flow, then vascular function information is obtained, but the rapid complex fluctuations of the default mode network (DMN) complicate the analysis and limit understanding of vascular physiology
Solution Approach 1:
The patent applies periodic action by implementing controlled periodic fluctuations in arterial oxygen partial pressure (PaO2) using sequential gas delivery. This creates a known periodic input signal that drives periodic changes in deoxyhemoglobin concentration, allowing the vascular system's transfer function to be characterized through frequency response analysis. The periodic nature of the input simplifies the analysis compared to the complex aperiodic DMN fluctuations.
Solution Approach 2:
The patent employs parameter changes by systematically varying the PaO2 parameter in a controlled periodic manner using sequential gas delivery. This allows the vascular system to be probed at different operating points and frequencies, enabling the measurement of vascular transfer functions and time constants without the confounding complexity of natural DMN fluctuations.
2Loss of information
If complex analysis such as cross correlation is used to group voxels into DMN map, then default mode network patterns are identified, but the source of modulation remains unknown and vascular functions are only partially reflected
Solution Approach 1:
The patent introduces a known periodic PaO2 fluctuation as an intermediary input signal that mediates the investigation of vascular function. This controlled input acts as a probe that elicits a measurable response from the vascular system, allowing the transfer function and time constants to be determined without relying on the unknown endogenous DMN fluctuations.
3Measurement precision
If asymmetric arrival time analysis is performed on DMN patterns to identify unilateral vascular pathologies, then conditions such as stenosis and ischemia can be detected, but the complex DMN pattern complicates the analysis
Solution Approach 1:
The patent employs feedback by measuring the BOLD signal response to the periodic PaO2 input and using this information to characterize the vascular transfer function. The phase and amplitude of the BOLD response relative to the known input provide feedback about vascular health, allowing detection of pathologies such as stenosis and ischemia through quantitative analysis of the transfer function parameters.
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
This approach simplifies the analysis by using predictable, controlled periodic signals, enhances measurement accuracy, and enables precise identification of vascular health and pathologies like arterial stenosis, ischemia, and neurodegenerative diseases by analyzing phase and period changes in response to the induced PaO2 patterns.
Implementation Method 1
concentrations of deoxyhemoglobin can be measured in the tissues using blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI). When blood flow in a tissue increases beyond its metabolic requirements, the [dOHb] is reduced by virtue of being diluted by the 'excess' oxyhemoglobin.
Implementation Method 2
Due to its paramagnetic properties, concentrations of deoxyhemoglobin can be measured in the tissues using blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI).
Implementation Method 3
a magnetic resonance imaging (MRI) device measures a magnetic signal in a voxel of the subject's brain
Data Source
AI summary
A method of implementing changes in deoxyhemoglobin concentration, the method comprising: targeting a sequence of partial pressures of oxygen in arterial blood (PaCh) values in a subject using a sequential gas delivery device in a periodic input pattern; measuring a blood-oxygen level dependent (BOLD) signal in a voxel of the subject's brain using a magnetic resonance imaging device while targeting the sequence of values; comparing the pattern to the signal; and determining a vascular tissue characteristic (vessel type, vessel orientation, or pathological condition) for the voxel based on the comparison.