Portable Single-Sided MR Sensor for Intramuscular Fluid Assessment
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Solution Overview
Problem
Current techniques for assessing fluid volume status in patients are inaccurate, invasive, or easily confounded by patient physiology, leading to inadequate management of conditions like end-stage renal disease and congestive heart failure, and lack a reliable indication of when hemodialysis patients are at risk for intradialytic hypotension.
Innovation Solution
A portable, single-sided MR sensor using a Unilateral Linear Halbach magnet array and multicomponent T2 relaxometry, measurement localization by tuning RF excitation frequency, and diffusion weighting by varying echo time to non-invasively measure intramuscular fluid distribution, providing real-time fluid volume assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional MRI is used for fluid assessment, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent segments the fluid assessment function from the complex MRI system by using a portable NMR sensor that measures only the specific relaxation parameter (T2) related to fluid distribution in muscle tissue, rather than requiring full MRI imaging capabilities. This segmentation allows accurate fluid assessment without the complexity of complete MRI equipment.
Solution Approach 2:
The patent extracts the essential measurement function (T2 relaxometry for fluid assessment) from the complex MRI system and implements it using a simplified portable NMR sensor. This extraction enables the core fluid measurement capability to be separated from the unnecessary complexity of full MRI equipment, achieving the same diagnostic purpose with a much simpler device.
2Device complexity
If bioimpedance or blood pressure techniques are used, then device complexity is reduced, but measurement precision and reliability deteriorate due to physiological variability
Solution Approach 1:
The patent uses muscle tissue as an intermediary medium that reflects systemic fluid status. By measuring fluid distribution in the muscle (a stable, accessible tissue), the system obtains an accurate indicator of overall volume status without being affected by the physiological variability that plagues direct blood pressure or bioimpedance measurements.
Solution Approach 2:
The patent replaces mechanical/physiological measurement systems (blood pressure cuffs, bioimpedance electrodes) with a magnetic resonance-based NMR sensor that measures molecular relaxation properties. This substitution eliminates the interference from physiological variability while maintaining device simplicity.
3Measurement precision
If invasive methods are used for fluid assessment, then measurement precision is improved, but patient comfort and ease of operation worsen
Solution Approach 1:
The patent enables the muscle tissue to serve itself as the measurement target - the tissue naturally contains the fluid whose distribution is being measured, requiring no external intervention, injection, or sampling. The portable NMR sensor simply measures the intrinsic T2 relaxation properties of the muscle tissue, providing accurate fluid compartment information non-invasively.
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 sensor offers accurate, real-time monitoring of fluid volume status, reducing the risk of intradialytic hypotension and improving treatment outcomes by quantifying fluid distribution in muscle tissue, overcoming limitations of traditional MRI and other methods.
Implementation Method 1
one or more magnets configured to provide a static magnetic field source
Implementation Method 2
one or more RF transmitter coils connected to a pulse sequence generator which are configured to apply a varying magnetic field to tissues of the patient
Implementation Method 3
one or more RF receiver coils configured to detect a magnetic field generated within tissues of the patient; perform an NMR measurement of a relaxation parameter of hydrogen nuclei
Data Source
AI summary
Devices and methods are provided for non-invasive sensing of tissue fluid distribution in a patient. The device includes one or more magnets configured to provide a static magnetic field source; one or more RF transmitter coils connected to a pulse sequence generator which are configured to apply a varying magnetic field to tissues of the patient; one or more RF receiver coils configured to detect a magnetic field generated within tissues of the patient; and a signal acquisition and processor system configured to acquire signals from the RF receiver coils and perform an NMR measurement of a relaxation parameter of hydrogen nuclei within a muscle tissue site of the patient. A single-sided MR sensor device may include permanent magnets arranged in a unilateral linear Halbach array; and RF coils and a processor which are configured to produce a depth-resolved, diffusion-weighted, multicomponent T2 relaxometry measurements of intramuscular fluid shifts in a patient.