Spatial Fat Suppression in Multi-Contrast SMS MRI
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Solution Overview
Problem
Current simultaneous multi-slice (SMS) magnetic resonance imaging techniques struggle to achieve significant acceleration in data acquisition for multiple contrasts, such as T2-weighted and fat-saturated images, due to limitations in reducing repetition time without compromising image contrast or introducing slice-crosstalk artifacts.
Innovation Solution
The method employs single-band binomial pulses to selectively excite fat in some slices while leaving water in others, followed by spoiler gradients to dephase fat protons, allowing for simultaneous acquisition of fat-saturated and conventional images, and enables multiple contrasts in a single scan with reduced RF peak power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If repetition time is reduced to accelerate data acquisition, then productivity is improved, but image contrast deteriorates
Solution Approach 1:
The patent segments the image acquisition into multiple slices that are excited simultaneously using multi-band RF pulses. Each slice is assigned a specific fat suppression scheme, allowing parallel acquisition of multiple contrasts across different slices while maintaining adequate TR for each slice's contrast requirements.
Solution Approach 2:
Different fat suppression schemes are applied locally to different slices based on their specific contrast requirements. Some slices receive fat-saturated imaging while others receive conventional imaging, allowing each region to be optimized for its intended contrast without compromising overall acquisition efficiency.
2Manufacturing precision
If multiple contrasts are acquired sequentially, then image quality is maintained, but loss of time increases
Solution Approach 1:
The patent merges multiple contrast acquisitions into a single simultaneous multi-slice scan. Multiple slices are excited at the same time with different fat suppression schemes, allowing T2-weighted, fat-saturated, and other contrast types to be acquired in parallel within the same TR period, dramatically reducing total acquisition time.
Solution Approach 2:
The simultaneous multi-slice acquisition enables continuous data collection across multiple slices throughout the TR period. Instead of sequentially acquiring different contrasts with gaps between scans, the system continuously populates k-space for multiple contrasts in parallel, maximizing the utilization of available scan time.
3Manufacturing precision
If fat suppression is applied uniformly across all slices, then fat saturation is achieved, but loss of energy increases due to higher RF peak power
Solution Approach 1:
Fat suppression is applied selectively only to those slices that require fat-saturated imaging, rather than uniformly to all slices. Conventional slices without fat suppression use lower RF power, reducing the overall peak power requirements while still achieving fat saturation where clinically needed.
Solution Approach 2:
Instead of applying full fat suppression across all slices, the patent applies partial fat suppression only to the necessary slices. This reduces the RF energy burden while maintaining adequate fat saturation for the specific clinical requirements of each slice.
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 enables simultaneous acquisition of multiple contrasts independently of the SMS sequence, reducing acquisition time and peak RF power, while maintaining clinically acceptable image quality by achieving spatial fat suppression and allowing for flexible contrast adjustments.
Implementation Method 1
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
Implementation Method 2
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 3
An MB RF pulse is generated by the superimposition of a number of individual single band (SB) RF pulses, of the type that are typically used to excite nuclear spins in a single selected slice in conventional magnetic resonance imaging
Implementation Method 4
As the nuclear spins relax, while returning to alignment in the basic magnetic field, they emit MR signals (which are also RF signals), which are received by suitable RF reception antennas in the MR scanner
Data Source
AI summary
In a method and imaging apparatus for acquiring multi-contrast magnetic resonance (MR) data, a data acquisition scanner is operated in a simultaneous multislice data acquisition sequence to radiate at least one single-band binomial radio-frequency (RF) pulse, that excites fat protons in at least some slices of an examination subject from which MR raw data are to be acquired simultaneously, and leaving water in a longitudinal plane for those at least some slices, and leaving all spin species in a longitudinal plane in others of the slices that are to be acquired simultaneously. A spoiler gradient is subsequently activated that dephases the fat protons that were excited. The scanner is then operated to execute an MR data acquisition sequence with excitation by radiation of multi-band RF pulses. MR raw data resulting from excitation of the fat protons, and MR raw data acquired with said multi-band RF excitation, are compiled in respective data files.