bT1RESS MRI Pulse Sequence for Contrast-Enhanced Angiography
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Solution Overview
Problem
Current MRI techniques for contrast-enhanced magnetic resonance angiography (MRA) face challenges in efficiently suppressing fluid signal and achieving optimal tissue contrast, particularly with the use of gadolinium-based contrast agents, which can lead to image artifacts and increased scan time, and there is a need for methods that do not rely on these agents due to safety concerns.
Innovation Solution
A balanced T1 relaxation enhanced steady-state pulse sequence is employed, incorporating a T1-weighted magnetization preparation and a single-shot balanced steady-state free precession (bSSFP) readout, with a time interval determined by the T1 relaxation time of the contrast-enhanced blood pool and the flip angle of the contrast-modifying RF pulses, to maximize contrast between enhanced blood and other tissues, allowing for efficient acquisition of MR data during the equilibrium phase of contrast enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gadolinium-based contrast agents are used for contrast-enhanced MRA, then image contrast and vascular conspicuity are improved, but safety risks increase due to nephrogenic systemic fibrosis
Solution Approach 1:
The patent removes the harmful contrast agent (gadolinium-based agent) from the imaging process while maintaining the ability to visualize vascular structures. It achieves this by using intrinsic T1 relaxation properties of blood and tissues, extracting the contrast enhancement mechanism from the external agent and relying on natural physiological differences and steady-state magnetization effects.
Solution Approach 2:
The imaging technique uses the body's own physiological properties (T1 relaxation times, blood flow characteristics, steady-state magnetization) to generate contrast without requiring external contrast agents. The system leverages the natural differences in relaxation properties between vascular and non-vascular tissues to achieve diagnostic-quality images.
2Measurement precision
If conventional contrast-enhanced MRA techniques are used, then vascular conspicuity is improved, but scan time increases and fluid signal suppression becomes difficult
Solution Approach 1:
The patent applies a contrast-modifying RF pulse before the steady-state free precession readout to pre-establish the desired magnetization state and T1 weighting. This preliminary action optimizes the contrast between enhanced blood and surrounding tissues before data acquisition begins, eliminating the need for lengthy acquisition periods to achieve adequate contrast.
Solution Approach 2:
The technique modifies the magnetization state and relaxation parameters through the contrast-modifying RF pulse, changing the T1 weighting and magnetization orientation before the steady-state readout. This parameter change enables optimal tissue contrast and fluid signal suppression within a single rapid acquisition, dramatically reducing scan time compared to conventional methods.
3Measurement precision
If T1-weighted magnetization preparation is applied, then tissue contrast is improved, but additional RF pulses and timing intervals are required
Solution Approach 1:
The patent combines the T1-weighted magnetization preparation and the steady-state free precession readout into a single integrated pulse sequence. The contrast-modifying RF pulse is seamlessly incorporated into the steady-state acquisition, merging the contrast enhancement function with the imaging function into one unified sequence that achieves optimal tissue contrast without requiring separate preparation and acquisition steps.
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 enhances image quality and vascular conspicuity, providing diagnostic-quality angiographic images with improved contrast-to-noise ratio and reduced scan time, comparable to CT angiography, while avoiding the need for contrast agents and cardiac synchronization.
Implementation Method 1
A balanced T1 relaxation enhanced steady-state pulse sequence is employed, incorporating a T1-weighted magnetization preparation
Implementation Method 2
The balanced T1 relaxation enhanced steady-state pulse sequence includes a T1-weighted magnetization preparation comprising at least one contrast modifying (CM) radio frequency (RF) pulse
Implementation Method 3
a single-shot balanced steady-state free precession (bSSFP) readout applied after T1-weighted magnetization preparation
Implementation Method 4
the individual magnetic moments of the nuclei in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 5
The goal of this contrast enhanced (CE) MRA method is to acquire the central k-space views at the moment the bolus of contrast agent is flowing through the vasculature of interest
Implementation Method 6
The time interval is determined based on a T1 relaxation time of a contrast-enhanced blood pool
Data Source
AI summary
A method for equilibrium phase contrast-enhanced magnetic resonance (MR) angiography using an extracellular MR contrast agent administered to a subject includes performing a balanced T1 relaxation enhanced steady-state (bT1RESS) pulse sequence to acquire MR data from a region of interest of the subject during an equilibrium phase of contrast enhancement after a first pass of the extracellular contrast agent through the region of interest. The bT1RESS pulse sequence includes a T1-weighted magnetization preparation including at least one contrast modifying (CM) radio frequency (RF) pulse, a single-shot balanced steady-state free precession (bSSFP) readout, and a time interval between the T1-weighted magnetization preparation and the acquisition of a center of k-space. The time interval is determined based on a T1 relaxation time of a contrast-enhanced blood pool and a flip angle of the at least one CM RF pulse. The method further includes generating an angiographic image of the region of interest.