Joint Multiresolution Magnetic Particle Imaging and System Matrix Compression

Marco Maass, Christian Mink, Alfred Mertins


Magnetic particle imaging (MPI) is a tracer-based medicalimaging method that is based on the nonlinearmagnetization characteristics of super-paramagneticironoxide nanoparticles (SPIOs) [1]. With differentaccelerated and static magnetic fields, the MPI-scannergenerates a small area in which the magnetic fieldsneutralize each other. The area is called the fieldfreepoint (FFP). The FFP is normally periodically movedon apre-defined trajectory over the whole field of view(FOV).The change of magnetization leads to an induced voltagein a receive coil, where, due to the nonlinearmagnetization characteristics of the SPIOs, only SPIOsfrom the vicinity of the FFP contribute significantly to themeasured signal. For MPI-scanners with a LissajousFFP-trajectory, the system response normally has to bemeasured. For this, a probe of SPIOs material is placed ondifferent spatial positions, and the responses aresaved in aso-called system matrix. With help of the system matrix,the inverse problem of estimating the SPIOs’ distributionfrom the voltage signal can be solved. Unfortunately, thesystem matrix can be very dense and huge in size. For adense matrix, the reconstruction process can be very slow.In [2], it was observed that the system matrix of MPI-scanners with a FFP traveling along a Lissajous-trajectorycan be highly compressed by the discrete cosine transform(DCT) followed by thresholding. Recently, a work formatrix compression was published on a non-Euclidiangrid, where the Chebyshev transform becomes orthogonaland the compression performance is even improved [3]. Inthis work, we develop a multiresolution representation forthe system matrix. In particular, we use a combination ofthe DCT-II and the discrete wavelet transform (DWT)forthe joint system-matrix compression and multiresolutionreconstruction.
Original languageEnglish
Title of host publicationInternational Workshop on Magnetic Particle Imaging
EditorsTobias Knopp, Thorsten Buzug
Number of pages2
Place of PublicationHamburg, Germany
PublisherInfinite Science Publishing
Publication date01.03.2018
ISBN (Print) 978-3-945954-48-5
Publication statusPublished - 01.03.2018
Event8th International Workshop on Magnetic Particle Imaging, IWMPI 2018
- Hamburg, Germany
Duration: 22.03.201824.03.2018


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