MRI Contrast Specificity via Dynamic Polarizing Field Control
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Solution Overview
Problem
Current MRI technologies face limitations in producing clear image contrast, particularly with activatable contrast agents that show modest signal intensity ratios between inactivated and activated states, making it difficult to differentiate between tissue types and pathologies.
Innovation Solution
The method involves dynamically controlling the polarizing magnetic field during the relaxation portion of an MRI pulse sequence, using an auxiliary magnetic field to modify the main polarizing magnetic field strength, which enhances the specificity of image contrast by exploiting the magnetic field-dependent variations in relaxivity of activatable contrast agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MRI pulse sequences are used with activatable contrast agents, then imaging can be performed at clinical magnetic field strengths, but the signal intensity ratio between inactivated and activated states is modest, resulting in poor image contrast
Solution Approach 1:
The patent applies dynamics by making the polarizing magnetic field strength variable during the relaxation portion of the pulse sequence. The field strength is dynamically adjusted between a first value and a second value to exploit the magnetic field-dependent variations in relaxivity of activatable contrast agents, thereby significantly improving the signal intensity ratio and image contrast without requiring overly complex pulse sequences
Solution Approach 2:
The patent changes the parameter of magnetic field strength during the relaxation portion of the pulse sequence. By varying the polarizing magnetic field strength between different values, the patent exploits the magnetic field-dependent relaxivity characteristics of activatable contrast agents to enhance the difference in signal intensity between activated and inactivated states, thereby improving image contrast
2Adaptability or versatility
If the polarizing magnetic field is kept constant during MRI scanning, then the pulse sequence is simple, but the ability to differentiate between activated and inactivated contrast agents is limited
Solution Approach 1:
The patent makes the polarizing magnetic field dynamic by adjusting its strength between a first value and a second value during the relaxation portion of the pulse sequence. This dynamic adjustment enables the system to differentiate between activated and inactivated contrast agents by exploiting their magnetic field-dependent relaxivity variations, while maintaining relatively simple magnetic field control through predefined field strength transitions
3Measurement precision
If modality-specific imaging techniques are used to improve tissue identification, then more identification methods are available, but the complexity of the imaging process increases
Solution Approach 1:
The patent improves tissue identification accuracy by changing the magnetic field strength parameter during the relaxation portion of the pulse sequence. This single parameter change exploits the magnetic field-dependent relaxivity of activatable contrast agents to enhance the differentiation between tissue types and pathologies, avoiding the need for multiple complex imaging modalities while maintaining high identification accuracy
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 significantly improves the specificity of MRI imaging by distinguishing between signal intensities produced by activated and inactivated contrast agents, leading to enhanced contrast and better tissue differentiation, even at clinical magnetic field strengths.
Implementation Method 1
When a target substance, such as human tissue, is subjected to the static polarizing magnetic field B0, the individual magnetic moments of the spins in the tissue attempt to align with the static polarizing magnetic field B0
Implementation Method 2
If the target tissue is subjected to an excitation magnetic field B1, which is in the x-y plane and which is near the Larmor frequency, the longitudinal magnetization MZ may be rotated, or 'tipped' into the x-y plane to produce a net transverse magnetic moment MXY
Implementation Method 3
MRI signals are radiated by excited nuclei in the target tissue in the intervals between consecutive RF pulses and are sensed by the RF coils
Implementation Method 4
when the excitation magnetic field B1 is terminated, the longitudinal magnetization MZ relaxes back to its equilibrium. The time constant that describes how the longitudinal magnetization MZ returns to its equilibrium value is commonly referred to as the spin lattice relaxation time T1
Implementation Method 5
The net transverse magnetic moment MXY also relaxes back to its equilibrium when the excitation magnetic field B1 is terminated. The time constant that describes how the transverse magnetic moment MXY returns to its equilibrium value is commonly referred to as transverse relaxation time or spin-spin relaxation time T2
Implementation Method 6
During MRI signal sensing, gradient magnetic fields are switched rapidly to alter the uniform magnetic field at localized areas thereby allowing spatial localization of MRI signals radiated by selected slices of the target tissue
Data Source
AI summary
A method for contrast agent enhanced magnetic resonance imaging (MRI) of a target sample, comprising generating a magnetic field shift in a polarizing magnetic field during a relaxation portion of an MRI pulse sequence and thereafter acquiring an MR image.