Variable-Flip-Angle Radial MRI for Free-Breathing Temperature Mapping
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Solution Overview
Problem
Current MRI-guided thermal therapy techniques face challenges such as susceptibility to motion artifacts, limited field-of-view, and inability to accurately measure temperature changes in adipose tissues, particularly in organs like the liver, due to the limitations of proton resonance frequency shift (PRF) thermometry and the need for breath-holding in Cartesian sampling.
Innovation Solution
A variable-flip-angle golden-angle ordered 3D stack-of-radial MRI technique that acquires multi-echo radial k-space data in segments with alternating flip angles, allowing for simultaneous PRF and T1-based thermometry in aqueous and adipose tissues, and simultaneous quantification of proton-density fat fraction (PDFF), R2*, and T1 relaxation time, enabling free-breathing multiparametric mapping with improved spatio-temporal resolution and motion robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Cartesian sampling with breath-holding is used, then motion artifacts are reduced, but scanning time increases and patient comfort decreases
Solution Approach 1:
The k-space data is divided into multiple segments that are acquired sequentially during free-breathing, allowing the scan to cover the entire field-of-view without requiring a single long breath-hold
Solution Approach 2:
The patent employs periodic acquisition of k-space segments synchronized with the patient's breathing cycle, capturing data at regular intervals to build up the complete image dataset over time
2Measurement precision
If Cartesian sampling with breath-holding is used, then motion artifacts are reduced, but field-of-view coverage is limited
Solution Approach 1:
The field-of-view is divided into multiple segments that can be acquired sequentially, enabling coverage of large anatomical regions such as the entire liver without restricting the imaging area
Solution Approach 2:
The patent transitions from 2D slice-by-slice acquisition to 3D volumetric segmentation, allowing simultaneous coverage of multiple slices in three-dimensional space to expand the effective field-of-view
3Measurement precision
If PRF thermometry is used, then temperature mapping is achieved, but motion artifacts cause errors
Solution Approach 1:
The patent creates multiple baseline phase images corresponding to different breathing phases, which are then selectively applied to correct temperature measurements based on the actual breathing phase at each time point
Solution Approach 2:
The system continuously monitors breathing phase and uses this feedback to select the appropriate baseline image for correction, dynamically adapting the motion compensation strategy to current physiological conditions
4Productivity
If VFA scheme with multiple flip angles is used, then T1 mapping speed is improved, but temporal resolution decreases
Solution Approach 1:
The acquisition of multiple flip angle data is segmented across different time points and breathing phases, allowing T1 mapping to be performed asynchronously without requiring all flip angles to be acquired within a single temporal window
Solution Approach 2:
The patent implements dynamic adjustment of flip angles across different segments and time points, optimizing the balance between T1 mapping accuracy and temporal resolution based on the specific imaging requirements and patient physiology
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 provides accurate, high-resolution temperature mapping and parameter quantification across larger volumes, including moving organs, without the need for breath-holding, enhancing the precision and efficiency of thermal therapy monitoring and liver disease diagnosis.
Implementation Method 1
The most widely used strategy for MR temperature mapping is based on the proton resonance frequency shift (PRF), which decreases linearly with temperature with a coefficient of −0.01 ppm/° C.
Implementation Method 2
One promising approach is to simultaneously quantify T1 relaxation time along with PRF to provide dual temperature measurements in both aqueous and adipose tissues.
Data Source
AI summary
A method for proton resonance frequency shift (PRF) and T1-based temperature mapping using a magnetic resonance imaging (MRI) system includes acquiring, using the MRI system, a set of magnetic resonance (MR) data from a region of interest of a subject by performing a variable-flip-angle multi-echo gradient-echo 3D stack-of-radial pulse sequence. The pulse sequence is configured to acquire radial k-space data in a plurality of segments, each segment acquired with each of a plurality of flip angles. The method further includes generating at least one T1 map based on the set of MR data, generating at least one PRF temperature map based on the set of MR data, generating at least one T1-based temperature map based on the set of MR data and displaying the PRF temperature map and the T1-based temperature map. In another embodiment, the MR data may be used to generate a plurality of quantitative parameter maps for each of the plurality of MR parameters such as T1, proton-density fat fraction (PDFF), and R2*.