Parallel T1 Mapping via Offset Gradient Echo Sequences
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Solution Overview
Problem
Conventional methods for spatially resolved T1 relaxation time quantification in magnetic resonance imaging are limited by their inability to achieve artifact-free volumetric scanning of the beating heart, as they can only acquire one slice per breath hold phase, leading to movement artifacts when attempting to cover the heart volumetrically.
Innovation Solution
A method involving parallel imaging of at least two slices using gradient echo sequences with temporally offset acquisition sequences, including inversion pulses and readout steps, allowing for volumetric representation by overlapping sequences by at least 50% and utilizing cardiac triggering to synchronize readout steps, enabling multiple slices to be scanned within a single breath hold phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional T1 quantification methods are used to depict cardiac muscle, then T1 relaxation time can be measured, but heart beat and breathing movement cause artifacts that prevent accurate volumetric representation
Solution Approach 1:
The patent divides the volumetric heart imaging into multiple sequential 2D slices that are acquired in parallel during a single breath-hold phase. Each slice is independently imaged using separate acquisition sequences, allowing the volumetric data to be constructed from multiple planar segments without motion artifacts between slices.
Solution Approach 2:
The patent implements continuous parallel acquisition of multiple slices within a single breath-hold phase using temporally offset acquisition sequences. This continuous parallel imaging approach eliminates gaps between slice acquisitions that would otherwise allow motion artifacts to occur, maintaining uninterrupted data collection throughout the volumetric scan.
2Volume of moving object
If multiple slices are acquired sequentially in separate breath hold phases, then volumetric coverage of the heart can be achieved, but movement artifacts occur between slices and cannot be directly associated for volumetric presentation
Solution Approach 1:
The patent merges multiple 2D slice acquisitions into a single parallel imaging process that completes all slice data collection within one breath-hold phase. The temporally offset acquisition sequences for different slices are synchronized and combined to form a complete volumetric dataset, eliminating the need for multiple separate breath-hold phases and the associated motion artifacts.
3Loss of time
If the MOLLI method is used to acquire T1 data within a breath hold phase, then only one slice can be acquired, but volumetric coverage of the heart is not possible
Solution Approach 1:
The patent transitions from single-slice 2D imaging to multi-slice 3D volumetric imaging by introducing parallel acquisition sequences that simultaneously image multiple slices along the through-plane direction. This dimensional extension allows volumetric coverage to be achieved within the same breath-hold time frame that previously only supported single-slice acquisition.
Solution Approach 2:
The patent employs dynamic temporal offsetting of acquisition sequences for different slices, where each slice is imaged at a slightly different time within the breath-hold phase. This dynamic timing strategy allows multiple slices to be captured sequentially yet simultaneously within the same breath-hold window, enabling volumetric coverage without extending the total acquisition time beyond a single breath-hold duration.
4Manufacturing precision
If conventional sequential slice acquisition is used, then each slice can be imaged with adequate resolution, but the total acquisition time exceeds a single breath hold phase
Solution Approach 1:
The patent implements dynamic temporal offsetting where acquisition sequences for different slices are staggered in time but overlap significantly (at least 50% overlap). This dynamic timing allows each slice to receive adequate imaging resources for high spatial resolution while the parallel execution across multiple slices reduces the total acquisition time to fit within a single breath-hold phase.
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 allows for precise, artifact-free volumetric quantification of T1 relaxation times, enabling the generation of T1 maps for the heart by acquiring multiple slices simultaneously, thereby reducing movement artifacts and improving temporal and spatial resolution.
Implementation Method 1
Magnetic resonance tomography (MRT) is an examination modality with which regions inside an examination subject can be shown with high resolution and good contrast
Implementation Method 2
The spin lattice relaxation time T1 is characteristic of a process that produces the reestablishment of the longitudinal steady state magnetization that appears in an applied basic magnetic field B0
Implementation Method 3
The MOLLI (Modified Look-Locker Inversion Recovery) method is known in order to quantify the T1 relaxation time in the myocardium. The method is based on an inversion recovery method in which the steady state magnetization is inverted by means of a 180° pulse
Implementation Method 4
spatially resolved quantification of the T1 relaxation time with a gradient echo method
Data Source
AI summary
In a method and apparatus for MR imaging, a data acquisition sequence is executed wherein at least two slices of an examination subject are imaged in parallel with a gradient echo method for spatially resolved quantification of the T1 relaxation time. At least one first acquisition sequence is implemented to acquire MR data from a first slice of the examination subject and at least one second acquisition sequence is implemented to acquire MR data from a second slice of the examination subject. The acquisition sequences each include an inversion pulse and at least two successive readout steps. The first and second acquisition sequences are temporally offset from one another such that they at least partially overlap.