SSFP UTE MRI with 3D Spiral Encoding for High-Field Diffusion
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Solution Overview
Problem
Magnetic resonance imaging (MRI) at high magnetic fields, such as 7 Tesla, suffers from issues like geometric distortion, non-uniform image sensitivity, and limited imaging depth due to RF transmission inhomogeneity and echo time limitations, which affect diffusion imaging quality.
Innovation Solution
Employing steady-state free procession (SSFP) with ultra-short echo time (UTE) and UTE-based magnetization transfer MRI, using 3D spiral trajectories and 30-degree RF pulses to enhance diffusion-weighted MRI, reducing geometric distortion and improving signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high magnetic field strength (7 Tesla) is used to obtain images with sharper details and better contrast, then image quality and contrast are improved, but geometric distortion due to magnetic field inhomogeneity worsens
Solution Approach 1:
The patent changes the echo time parameter to ultra-short echo time (UTE) range to capture signals before significant T2* decay and geometric distortion occur. This parameter change allows imaging at high field strengths while minimizing the harmful effects of field inhomogeneity on image geometry
Solution Approach 2:
The patent employs dynamic trajectory adjustment in k-space sampling, using spiral or radial trajectories that can be optimized to minimize distortion effects. The readout gradient dynamics are adjusted to balance between acquisition speed and geometric accuracy
2Measurement precision
If high magnetic field strength (7 Tesla) is used to improve image contrast, then contrast quality is improved, but non-uniform image sensitivity due to RF transmission inhomogeneity worsens
Solution Approach 1:
The patent divides the imaging volume into multiple segments or slices, each with optimized RF pulse parameters. By segmenting the excitation process, the system can compensate for B1 inhomogeneity across different regions of the imaging volume, ensuring more uniform sensitivity
Solution Approach 2:
The patent adjusts RF pulse parameters such as flip angle and pulse duration as functions of spatial position to compensate for transmission inhomogeneity. This parameter optimization ensures uniform signal intensity across the image field-of-view despite variations in RF field distribution
3Measurement precision
If conventional diffusion imaging sequence is used at high magnetic field strength, then diffusion weighting is applied, but spatial uniformity of diffusion weighting deteriorates due to severe RF transmission inhomogeneity
Solution Approach 1:
The patent optimizes the RF pulse parameters specifically for diffusion-weighted imaging at high fields, adjusting flip angles and pulse timings to ensure uniform diffusion weighting across the field-of-view. The gradient pulse parameters are also optimized to work synergistically with the RF pulses
Solution Approach 2:
The patent introduces an intermediary calibration step using phantom measurements or reference scans to map the actual RF field distribution. This information is then used to adjust the diffusion weighting parameters, serving as a mediator between the ideal sequence design and the actual hardware performance
4Measurement precision
If higher-frequency RF pulses are used at high magnetic field strength to maintain resolution, then image resolution is maintained, but penetration depth into tissue is limited
Solution Approach 1:
The patent adjusts the RF frequency and pulse duration parameters to optimize the balance between penetration depth and resolution. By using longer pulse durations at optimized frequencies, the system achieves both adequate penetration and maintained resolution
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
Enhances MRI image quality at high magnetic fields by minimizing geometric distortion, ensuring uniform image sensitivity, and allowing deeper tissue penetration, facilitating detailed imaging of tissues with fast T2 relaxation times.
Implementation Method 1
Magnetic resonance imaging (MRI) is a widely deployed medical imaging in biomedical research and in clinics
Implementation Method 2
applying a three-dimension (3D) magnetic gradient within the imaging volume, wherein the 3D magnetic gradient comprises a 3D spiral pulse
Implementation Method 3
enhancement of diffusion-weighted (DW) magnetic resonance imaging (MRI) using steady-state free procession (SSFP) of ultra-short echo time (UTE)
Implementation Method 4
facilitating detailed imaging of tissues with fast T2 relaxation times
Implementation Method 5
enhancement of UTE-based magnetization transfer MRI
Data Source
AI summary
Methods, apparatus, and storage medium for enhancing diffusion-weighted magnetic resonance imaging (MRI) by using steady-state free procession (SSFP) of ultra-short echo time (UTE) and UTE-based magnetization transfer MRI. One method includes, for each of a plurality of data acquisition sequences: for each of a plurality of data acquisition sequences: applying a set of radio-frequency (RF) pulses to interact with transverse magnetization within an imaging volume of an object in a magnetic field, applying a three-dimension (3D) magnetic gradient within the imaging volume, wherein the 3D magnetic gradient comprises a 3D spiral pulse, and acquiring, during the 3D spiral pulse, raw imaging data from the imaging volume; and constructing a raw MRI image based on the raw imaging data acquired from the plurality of data acquisition sequences.