TSE Reference Scan for SMS MRI Artifact Reduction
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Solution Overview
Problem
Conventional gradient echo (GRE) reference scans in simultaneous multislice (SMS) turbo spin echo (TSE) MR data acquisition are prone to slice crosstalk and fat ring ghosting artifacts, limiting their application in clinical practice due to inconsistencies with TSE imaging scans.
Innovation Solution
Implementing a turbo spin echo (TSE)-based reference scan, such as a RARE or HASTE sequence, instead of the conventional GRE reference scan, to improve image quality by reducing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional GRE reference scan is used in SMS TSE data acquisition, then the reference scan can be quickly acquired, but slice crosstalk and fat ring ghosting artifacts occur
Solution Approach 1:
The patent changes the fundamental parameters of the reference scan by switching from a GRE sequence to a TSE sequence. This parameter change fundamentally alters the pulse sequence characteristics, including the use of 90° excitation pulses followed by 180° refocusing pulses, different echo time structures, and distinct k-space sampling patterns. These parameter changes eliminate the inconsistencies between reference scan and imaging scan that cause slice crosstalk and fat ring ghosting artifacts, while maintaining acceptable acquisition speed through optimized TSE echo train length and parallel imaging techniques.
2Loss of time
If a GRE reference scan is used, then acquisition time is reduced, but image quality deteriorates due to artifacts
Solution Approach 1:
The patent applies parameter changes by transitioning from GRE to TSE sequence parameters for the reference scan. This includes changing the pulse sequence type, flip angles, echo time structures, and k-space sampling methods. These parameter changes improve image quality by eliminating artifacts while the TSE sequence is optimized with appropriate echo train length and parallel imaging factors to maintain reasonable acquisition time, thus resolving the contradiction between speed and quality.
3Manufacturing precision
If a TSE-based reference scan is implemented, then image quality improves by reducing artifacts, but acquisition time increases
Solution Approach 1:
The patent applies partial action by acquiring only a subset of k-space lines in the TSE reference scan rather than complete images. By using partial Fourier techniques and parallel imaging reconstruction, the reference scan acquires sufficient data to generate accurate sensitivity maps and reference images without requiring full TSE echo trains for all k-space lines. This reduces the acquisition time penalty while maintaining the artifact-reduction benefits of TSE sequencing.
Solution Approach 2:
The reference scan is performed as a preliminary step before the main SMS TSE imaging acquisition. By completing the reference scan with TSE sequence first, the system establishes accurate baseline images and sensitivity maps that are then reused during the main imaging process. This preliminary action with optimized TSE parameters minimizes the time impact on the overall imaging protocol while ensuring high image quality through artifact-free reference data.
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
The TSE-based reference scan significantly reduces slice crosstalk and ghosting artifacts, resulting in more homogeneous image intensity and improved image quality compared to conventional GRE reference scans.
Implementation Method 1
the examination object (a patient, in the case of medical magnetic resonance imaging) is exposed to a strong and constant basic magnetic field (called the B0 field), by the operation of a basic field magnet of an MR scanner
Implementation Method 2
The magnetic resonance signals are produced by the radiation of radio-frequency (RF) pulses from an RF radiator, such as one or more antennas, in the MR scanner. These RF pulses excite nuclear spins in the examination object, and are therefore often called excitation pulses. As the nuclear spins relax, while returning to alignment in the basic magnetic field, they emit MR signals
Implementation Method 3
The MR scanner also has a gradient coil arrangement that is operated in order to activate gradient fields that spatially encode the magnetic resonance signals
Implementation Method 4
After the nuclear spins have been flipped by the RF excitation pulse, the resulting MR signal exhibits an exponential decay in strength as the excited nuclear spins relax. This decaying signal is referred to as an echo signal, or simply as an echo
Data Source
AI summary
In a method and apparatus for acquiring magnetic resonance (MR) data, an MR data acquisition scanner is operated, while a subject is situated therein to execute a simultaneous multislice (SMS) turbo spin echo (TSE) sequence by implementing a TSE-based reference scan to acquire reference data and an imaging scan, to acquire raw MR data from the subject. The reference data and the raw MR data are entered into a memory organized as k-space. A computer accesses the memory in order to make the k-space data, composed of said reference data and said image data, available in electronic form, as at least one data file.