Coplanar Probe for Microwave Dielectric Tissue Measurement
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Solution Overview
Problem
Current methods for measuring dielectric properties of biological tissues, particularly in the microwave frequency range, face limitations in accurately differentiating between various tissue types and monitoring blood quality over time, as they struggle to quantify total tissue water and discriminate between free and chemically-bound water effectively.
Innovation Solution
A probe sensor with a coplanar transmission line and a first ground plane on a printed circuit board, featuring a plated-through contact via surrounded by a part-circular ring of ground vias, is used to measure dielectric properties. This sensor is integrated into a blood collection and transfusion set, allowing for the measurement of blood quality by comparing initial and subsequent electrical parameters using a network analyzer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coaxial probes are used to measure dielectric properties, then measurements can be made in the 10 kHz to 1 MHz range, but the frequency range is limited and differentiation between tissue types at higher frequencies is not achieved
Solution Approach 1:
The patent changes the measurement frequency parameter from the traditional 10 kHz to 1 MHz range to a higher 100 MHz to 10 GHz microwave frequency range. This parameter change enables differentiation between cancerous and non-cancerous tissues based on their distinct dielectric properties at these higher frequencies, particularly in total tissue water and free versus chemically-bound water discrimination.
2Measurement precision
If conventional coaxial probes are used, then the device structure is simple, but the ability to quantify total tissue water and discriminate between free and chemically-bound water is not achieved
Solution Approach 1:
The patent replaces the conventional mechanical coaxial probe structure with a printed circuit board-based coplanar waveguide structure. This substitution maintains structural simplicity while enabling microwave frequency measurements that provide the capability to quantify total tissue water and discriminate between free and chemically-bound water through dielectric property measurements.
3Measurement precision
If measurements are made at lower frequencies, then intracellular and extracellular water differences can be detected, but total tissue water quantification and free versus chemically-bound water discrimination are not possible
Solution Approach 1:
The patent changes the frequency parameter from lower frequencies (where only intracellular/extracellular water differences are detectable) to microwave frequencies of 100 MHz to 10 GHz. This energy increase enables the measurement system to access higher frequency dielectric relaxation processes that provide information about total tissue water content and the distinction between free and chemically-bound water states.
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 solution enables accurate measurement of dielectric properties of tissues and blood, allowing for discrimination between different tissue types and monitoring blood degradation, ensuring the quality of transfused blood and aiding in surgical margin assessment.
Implementation Method 1
biological materials, including human and animal tissue and blood, have dielectric properties that vary somewhat with the type of tissue. These dielectric properties include permittivity, and conductivity
Implementation Method 2
measuring electrical parameters of tissue in the microwave frequency range, in particular between 100 MHz and 10 GHz
Data Source
AI summary
A probe sensor has a printed circuit comprising a coplanar transmission line, a ground plane, a plated-through contact via, and a part-circular ring of ground vias surrounding the contact via. The coplanar transmission line and ground plane are formed on a first layer of the printed circuit, and the contact via and part-circular ring of ground vias are plated with a conductive biocompatible material on a second layer of the printed circuit. A system uses a network analyzer with the probe to measure electrical properties of biological tissue. Also described is a method of using the system to determine qualities of stored blood.