MRI Phase Correction via Stable Echo Pre-Scan
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Solution Overview
Problem
Conventional magnetic resonance imaging (MRI) techniques using the Fast Spin Echo method face challenges in maintaining image quality due to varying phase differences among echo signals, leading to sensitivity unevenness and ghost phenomena, which are not adequately corrected by pre-scans.
Innovation Solution
An MRI apparatus and method that perform a pre-scan to calculate stable phase differences between echo signals, excluding initial time period signals, and use these calculations to correct the pulse sequence for the main scan, ensuring accurate phase correction and improved image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-scan is performed to measure phase differences among echo signals, then image quality degradation is prevented, but the phase differences may still vary depending on the image taking method, leading to improper correction
Solution Approach 1:
The patent performs a pre-scan before the main scan to measure phase differences among echo signals. This preliminary measurement allows the system to calculate correction amounts and adjust the pulse sequence for the main scan, ensuring that phase differences are compensated in advance to prevent image quality degradation
Solution Approach 2:
The patent changes parameters of the pulse sequence based on measured phase differences. Specifically, it adjusts the timing and phases of RF pulses and gradient magnetic fields to cancel out stimulated echoes and correct phase shifts, thereby adapting the imaging parameters to the actual phase conditions
2Quantity of substance
If multiple RF pulses are applied to collect echo signals, then more echo signals are obtained, but stimulated echoes are generated causing phase shifts and image quality degradation
Solution Approach 1:
The patent converts the harmful stimulated echo into a beneficial measurement tool. By intentionally generating stimulated echoes during a pre-scan and measuring their phase differences, the system calculates correction amounts that are then applied to the main scan to eliminate the harmful effects of stimulated echoes on image quality
Solution Approach 2:
The patent applies preliminary corrective actions during the pre-scan to counteract the harmful effects of stimulated echoes. By measuring phase differences caused by stimulated echoes in advance and calculating appropriate correction amounts, the system prepares compensation parameters that prevent image quality degradation during the main scan
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 effectively prevents image quality degradation caused by varying phase differences, resulting in improved sensitivity and reduced sensitivity unevenness, as demonstrated by enhanced phantom images.
Implementation Method 1
a method called 'Fast Spin Echo (FSE) method' is conventionally known. The FSE method is an image taking method by which a plurality of echo signals called an echo train are collected by applying a flip pulse to an examined subject and then sequentially applying a plurality of flop pulses to the examined subject. In this situation, the flip pulse is a Radio Frequency (RF) pulse used for exiting atomic nuclear spins within the examined subject. The flop pulses are RF pulses used for refocusing phases of the atomic nuclear spins.
Implementation Method 2
a stimulated echo is generated together with a spin echo
Implementation Method 3
a stimulated echo is generated together with a spin echo
Data Source
AI summary
A magnetic resonance imaging apparatus according to an embodiment includes an executing unit, a calculating unit, and a correcting unit. The executing unit executes a pre-scan while using a pulse sequence by which a plurality of echo signals are collected. The calculating unit calculates a phase difference between at least two echo signals of which a fluctuation of phase differences is stable and that are selected out of the plurality of echo signals collected during the pre-scan and are selected while excluding echo signals collected during an initial time period. The correcting unit that corrects a pulse sequence used for a main scan, based on the phase difference calculated by the calculating unit.