MRI Phase Correction via Look-Up Tables
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Solution Overview
Problem
Conventional magnetic resonance imaging (MRI) systems using the fast spin echo (FSE) method face image quality deterioration due to zeroth-order phase shifts caused by Maxwell terms and zeroth-order eddy currents, which can lead to reduced signal-to-noise ratio, ghosts, and uneven sensitivity, and require time-consuming pre-scans for phase correction.
Innovation Solution
An MRI apparatus that calculates and corrects the phase shift amounts for refocusing pulses in real-time during the FSE method without a pre-scan, using stored look-up tables for phase shift data and simulation calculations to align spin echo and stimulated echo components, thereby eliminating the need for a pre-scan and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pre-scan phase correction is performed to correct zeroth-order phase shifts, then image quality is improved, but imaging time is increased
Solution Approach 1:
The patent pre-calculates and stores phase shift amounts for different refocusing pulse phases in look-up tables before actual imaging. This preliminary preparation eliminates the need for time-consuming pre-scans during imaging, as the correction data is already available for immediate application.
Solution Approach 2:
The patent creates look-up tables that store pre-calculated phase shift amounts, serving as reference copies that can be quickly queried during imaging. This copying approach replaces the need for real-time pre-scan measurements, significantly reducing imaging time while maintaining correction accuracy.
2Productivity
If conventional FSE method is used without phase correction, then imaging time is short, but image quality deteriorates due to zeroth-order phase shifts
Solution Approach 1:
The patent replaces the mechanical pre-scan measurement process with a computational approach using look-up tables. Phase shift corrections are obtained through table lookup and calculation rather than physical pre-scan measurements, maintaining fast imaging speeds while improving image quality.
Solution Approach 2:
The patent changes the approach from real-time pre-scan parameter measurement to pre-calculated parameter storage. By storing phase shift amounts for various refocusing pulse phases in advance, the system可以快速 apply corrections without performing time-consuming pre-scans, thus maintaining fast imaging while improving quality.
3Adaptability or versatility
If multiple shots are used in FSE method, then coverage is improved, but phase shift variations between shots increase
Solution Approach 1:
The patent applies local quality correction by calculating and applying phase shift corrections specific to each shot based on its refocusing pulse phase. The look-up tables store phase shift amounts for different phases, allowing each shot to receive tailored correction, ensuring phase consistency across multiple shots with different phases.
Solution Approach 2:
The patent implements a feedback mechanism where the actual refocusing pulse phase is determined for each shot, and the corresponding pre-calculated phase shift amount is retrieved from the look-up table. This feedback loop ensures that each shot receives the appropriate correction, maintaining phase consistency across multiple shots.
Data Source
AI summary
A magnetic resonance imaging apparatus according to an embodiment includes a calculation unit, a collecting unit, and an execution unit. The calculation unit calculates, based on a pulse sequence used in data collection by fast spin echo method, a phase shift amount on at least one echo component included in each of a plurality of echo signals. The correcting unit corrects, based on the calculated phase shift amount, phases of refocusing pulses applied in the pulse sequence such that phases match at least one of between spin echo components, between stimulated echo components, and between a spin echo component and a stimulated echo component. The execution unit executes the pulse sequence in which the refocusing pulses of the corrected phases are applied.