MRI Image Reconstruction Using Scattering-Based Region Selection
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Solution Overview
Problem
Current methods for generating image data of moving subjects within the body, such as the heart, suffer from significant movement artifacts due to breathing and cardiac movements, requiring lengthy measurement times and additional navigator data for correction, which is inefficient and not universally applicable.
Innovation Solution
A method that acquires raw data at various measurement points in time, using position overview data to identify and select optimal test regions with high scattering for movement detection, allowing for image reconstruction without additional navigator measurements, thereby improving image quality and reducing measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If raw data are acquired during movement cycles without phase-specific triggering, then measurement time is reduced, but movement artifacts increase significantly
Solution Approach 1:
The patent segments the k-space data acquisition into multiple passes, where each pass acquires data at a specific cardiac phase (e.g., early diastole, mid-diastole, early systole). This segmentation allows the system to collect complete k-space data across different movement phases without requiring all data to be acquired simultaneously, thereby reducing total measurement time while maintaining image quality through phase-specific acquisition.
Solution Approach 2:
The patent employs periodic triggering based on EKG signals to acquire raw data at specific cardiac phases. The system uses periodic cardiac cycles to synchronize data acquisition with the heart's rhythmic movement, ensuring that data is collected when the heart is in a relatively stable diastolic phase. This periodic action allows repeated sampling across multiple cardiac cycles, enabling complete k-space filling while minimizing movement artifacts.
2Manufacturing precision
If additional navigator measurements are used for movement correction, then image quality improves, but measurement time increases and device complexity increases
Solution Approach 1:
The patent makes the raw data acquisition process multi-functional by simultaneously serving two purposes: (1) acquiring the necessary k-space data for image reconstruction, and (2) collecting position overview data for movement detection and correction. By integrating these functions into a single acquisition process, the system eliminates the need for separate navigator measurements, thereby improving image quality without increasing measurement time or device complexity.
Solution Approach 2:
The patent implements self-service by using the raw data itself to generate position overview data for movement correction. Instead of requiring separate navigator acquisitions, the system extracts movement information from the raw k-space data through processing of position overview data. This self-service approach allows the same data acquisition process to serve both image reconstruction and movement correction needs, eliminating additional measurement time.
3Manufacturing precision
If data acquisition is triggered at specific cardiac phases, then movement artifacts are reduced, but measurement time increases due to incomplete k-space filling
Solution Approach 1:
The patent divides the k-space acquisition into multiple segments corresponding to different cardiac phases. Each segment is acquired during a specific phase (e.g., early diastole, mid-diastole, early systole), and the segments are later combined through reconstruction. This segmentation allows the system to fill k-space completely across multiple cardiac cycles while triggering data acquisition at optimal phases to minimize movement artifacts.
Solution Approach 2:
The patent maintains continuous k-space filling across multiple cardiac cycles by systematically acquiring data segments at different phases. The useful action of k-space data collection continues uninterrupted across multiple heartbeats, with each cycle contributing to the complete dataset. This continuous acquisition strategy ensures that all necessary k-space data is collected while utilizing the natural periodicity of cardiac movement to minimize artifacts.
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 significantly improves image quality by automatically determining the best test regions for movement detection, reducing movement artifacts and measurement time, and enabling the generation of high-quality volume images of the heart without the need for navigator measurements.
Implementation Method 1
the body or the body part to be examined must initially be exposed to an optimally homogeneous, static basic magnetic field (most often designated as a B0 field). Nuclear spins in the subject are thereby aligned parallel to the direction of the B0 field
Implementation Method 2
radio-frequency pulses are radiated into the examination subject with radio-frequency antennas, the frequency of the radio-frequency pulses being at or approximately at the resonance frequency (known as the Larmor frequency) of the nuclei to be excited
Implementation Method 3
By means of these radio-frequency pulses, nuclear spins of the atoms in the examination subject are excited such that they are deflected by an amount known as an 'excitation flip angle' out of their steady state
Implementation Method 4
The magnetic flux density of these radio-frequency pulses is typically designated with B1. By means of these radio-frequency pulses, nuclear spins of the atoms in the examination subject are excited such that they are deflected by an amount known as an 'excitation flip angle' out of their steady state (parallel to the basic magnetic field B0). The nuclear spins then initially precess around the z-direction and relax again bit by bit.
Implementation Method 5
Spatial coding of the magnetic resonance signals takes place with the use of rapidly switched (activated) gradient magnetic fields that are superimposed on the basic magnetic field during the emission of the magnetic resonance radio-frequency pulses and/or the acquisition of the raw data.
Data Source
AI summary
In a method and apparatus for the generation of image data of a moving subject inside a body, raw data are initially acquired for a region encompassing the subject at different measurement points in time, and position overview data for the different measurement points in time are generated on the basis of at least a portion of the raw data. A scattering of the position overview data is then determined, which scattering is dependent on the measurement point in time. Spatial test regions within the position overview data are selected depending on the scattering. Trust parameter values are determined for the individual test regions, and a reconstruction of image data then takes place on the basis of the raw data under consideration of the trust parameter values of the different test regions.