MRI Spoiler Gradient Control for FID Artifact Reduction
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Solution Overview
Problem
Conventional magnetic resonance imaging (MRI) techniques using spin echo sequences require high-strength spoiler gradient magnetic fields to reduce Free Induction Decay (FID) artifacts, which limits the ability to shorten echo space and maintain image resolution.
Innovation Solution
The MRI apparatus employs a hybrid spoiling method that maintains equal or higher strengths of both the spoiler and rewind gradient magnetic fields during slice encodings, using a combination of no-spoiling and constant flop-spoiling methods to control these fields, thereby reducing FID artifacts without increasing the spoiler gradient magnetic field's strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a high-strength spoiler gradient magnetic field is applied to remove FID artifacts, then FID artifacts are reduced, but the echo space cannot be shortened and image resolution deteriorates
Solution Approach 1:
The patent divides the gradient magnetic field control into two independent components: a spoiler gradient magnetic field for eliminating FID artifacts and a rewind gradient magnetic field for maintaining echo spacing. By segmenting the control function, each component can be optimized independently - the spoiler field strength can be reduced while the rewind field maintains appropriate strength to preserve resolution.
Solution Approach 2:
The rewind gradient magnetic field acts as an intermediary mechanism that compensates for the reduced spoiler gradient strength. By introducing this intermediate control element, the system can achieve FID artifact reduction without sacrificing image resolution, as the rewind field maintains the necessary magnetic field strength for proper echo spacing.
2Object-affected harmful factors
If a high-strength spoiler gradient magnetic field is applied to remove FID artifacts, then FID artifacts are reduced, but the echo space is lengthened
Solution Approach 1:
The patent separates the functions of FID artifact elimination and echo spacing maintenance into different gradient magnetic field components. The spoiler gradient handles artifact elimination while the rewind gradient maintains echo spacing, allowing independent optimization of each function without compromise.
Solution Approach 2:
The rewind gradient magnetic field serves as an intermediary that preserves echo spacing despite reduced spoiler gradient strength. This intermediate mechanism ensures that the echo space remains appropriate for image quality while the spoiler field strength is reduced for artifact minimization.
3Object-affected harmful factors
If the strength of spoiler gradient magnetic field is increased to remove FID artifacts, then FID artifacts are reduced, but the device complexity increases
Solution Approach 1:
The patent segments the gradient magnetic field control into independent spoiler and rewind components, each with dedicated control. This segmentation simplifies the overall control strategy by allowing independent optimization of each field's strength and timing, rather than requiring complex coordinated control of a single field.
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 the acquisition of images with reduced FID artifacts while preventing the need for high-strength spoiler gradients, enabling shorter echo spaces and improved slice resolution.
Implementation Method 1
a spoiler gradient magnetic field for canceling an FID signal produced by a flop pulse is applied after a flop pulse for refocusing
Implementation Method 2
a rewind gradient magnetic field before applying the flop pulse
Implementation Method 3
a flip pulse for exciting spin of nuclei inside a subject body
Data Source
AI summary
According to a magnetic resonance imaging apparatus according to an embodiment, a Radio Frequency (RF) pulse applying unit applies to a subject a flip pulse for exciting spin of nuclei inside a subject body, and a flop pulse for refocusing the phase of the spin. A gradient magnetic-field applying unit applies a spoiler gradient magnetic field onto the subject after the flop pulse is applied, and applies a rewind gradient magnetic field before applying the flop pulse. A control unit executes a pulse sequence of controlling the gradient magnetic-field applying unit so as to keep each of the strengths of the spoiler gradient magnetic field and the rewind gradient magnetic field at respective predetermined values or higher with respect to each of a plurality of slice encodings.