Electronic Calibration of Magnetic Particle Imaging System
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Solution Overview
Problem
Current magnetic particle imaging (MPI) calibration methods are time-consuming and inefficient, particularly for large field of views, due to mechanical scanning requirements and limited signal-to-noise ratios, which hinder practical adoption in clinical settings.
Innovation Solution
An electronic coded calibration scene is proposed, utilizing multiple nanoparticle samples with electromagnets to create virtual position changes, allowing for faster calibration through compressed sensing methods without mechanical scanning, and enhancing signal-to-noise ratios by distributing nanoparticles randomly or pseudo-randomly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical scanning is used to calibrate the MPI system at each grid point, then calibration data can be obtained with sufficient signal-to-noise ratio, but the calibration time becomes extremely long (9.75 hours for 30×30×30 grid points)
Solution Approach 1:
The calibration process is segmented into two parts: (1) a fast pre-calibration phase using a small nanoparticle sample scanned at reduced resolution to obtain initial system matrix elements, and (2) a refinement phase using compressed sensing with randomly positioned nanoparticle samples to complete the calibration. This segmentation allows the system to achieve sufficient measurement precision without requiring exhaustive scanning at full resolution, thereby reducing calibration time from hours to minutes.
Solution Approach 2:
Instead of performing complete calibration measurements at all N grid points, the invention uses partial action by measuring only M measurements where M << N (typically 10-30% of total voxels). The compressed sensing algorithm then reconstructs the full system matrix from these partial measurements, achieving adequate signal-to-noise ratio without the excessive time cost of full scanning.
2Productivity
If the nanoparticle sample is scanned at random positions using compressed sensing, then the number of measurements is reduced by 80-90%, but the signal-to-noise ratio decreases due to fewer nanoparticles in the sample
Solution Approach 1:
A small nanoparticle sample is first scanned at reduced resolution to perform preliminary calibration and obtain initial system matrix elements. This preliminary action provides a foundation that allows subsequent compressed sensing measurements to be performed with fewer nanoparticles, as the initial calibration data compensates for the lower signal strength in the reduced sample, thereby maintaining acceptable signal-to-noise ratio while achieving high calibration speed.
3Measurement precision
If multiple data acquisition at the same position is performed to increase signal-to-noise ratio, then measurement precision improves, but the mechanical scanner must stop at every grid point, limiting calibration speed
Solution Approach 1:
The invention transitions from static, discrete point-by-point scanning to a dynamic approach where the nanoparticle sample is continuously moved through random positions in the field of view. Multiple measurements are acquired during continuous motion rather than at stopped positions, enabling the system to maintain high signal-to-noise ratio through temporal averaging while achieving continuous scanning speeds that dramatically reduce calibration time.
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 reduces calibration time, improves image quality, and eliminates the need for mechanical scanning, enabling faster and more efficient system calibration with fewer measurements.
Implementation Method 1
Electronic coded calibration scene includes nanoparticle samples at multiple positions. There are one or more electromagnets around the nanoparticle samples that create a magnetic field at the desired amplitude.
Implementation Method 2
By controlling the currents of the electromagnets, the magnetic field is adjusted so that the nanoparticles behave as if they are in a different position.
Data Source
AI summary
A method for electronic calibration of a magnetic particle imaging system is provided by proposing a coded calibration scene that contains multiple nanoparticle samples distributed randomly or pseudo-randomly inside a volume of the coded calibration scene where nanoparticle positions are changed virtually multiple times to create different calibration scenes. Virtual effect is created with current carrying electromagnets surrounding the nanoparticle samples. The method comprises: placing a plurality of nanoparticle samples inside a calibration scene; surrounding the plurality of nanoparticle samples with one or more electromagnets; applying a current to the one or more electromagnets to cause a magnetic field offset at a desired amplitude to virtually move the plurality of nanoparticle samples to a desired position; generating a system matrix with compressed sensing methods by using measurements taken for different current excitations of the one or more electromagnets, wherein the plurality of nanoparticles samples are virtually in different positions.