Iron core coil designs for MPI

In Magnetic Particle Imaging, much of the power consumed during an imaging sequence is used for the generation of the selection and focus fields. In today’s MPI scanners three different concepts are applied to generate the gradient fields: Air coils, permanent magnets and coils with soft iron. Air coils and permanent magnets have the great advantage of good calculability by the Biot-Savart Law. On the way to a clinical imaging modality, the needed power for sufficient gradient strength demand the use of soft iron. In order to make good use of the ferromagnetic amplification properties, much more complex simulations have to be done. A recently published head scanner uses a soft iron yoke for field generation. In this study, we investigated different coil geometries with soft iron with respect to this head scanner.   Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009042, DOI: 10.18416/IJMPI.2020.200904

MPIMeasurements.jl: An Extensible Julia Framework for Composable Magnetic Particle Imaging Devices

Magnetic particle imaging (MPI) is a pre-clinical imaging modality, whose system design is still evolving, in particular towards human studies and clinical use. Therefore, many MPI scanners are custom-made distributed systems, both on the hard- and the software side. In this work we present the open-source Julia framework MPIMeasurements.jl, which implements a composable representation of imaging systems. It also offers flexible data structures that allow the implementation of specific imaging protocols, such as online/offline measurements, repeated measurements and system matrix calibrations. %that are reusable across systems. The project is designed to be expanded to new systems through community development and component reuse. To showcase the versatility of the software package, we give an overview of four very different MPI systems, which were realized with MPIMeasurements.jl

Organ specific mouse head coil for improved image quality in magnetic particle imaging

Magnetic particle imaging is a very useful tool in the detection of stroke. To study the ability of stroke in a mouse model the data acquisition is challenging as a mouse brain contains only a very small ratio of blood compared to large animals or humans. The effective concentration within the whole organ is therefore very small, especially compared to the heart or the liver. Typical MPI receiver coils however cover a sensitive region of around 30 mm to 50 mm and have a bore size of above 40 mm. This leads on the one hand to non-optimal signal coupling due to the distance to the particles and on the other hand strong signals from the heart can cause artifacts in the low signal regions. In this work we present a coil optimized for mouse brain imaging, which due to its small size, also dampens signal from regions outside of the coil

Receive path calibration to exchange system matrix data of different receivers

In Magnetic Particle Imaging the determination of the system matrix is a time-consuming process. As the transfer function differs depending on the electronics of the receive chain, a system matrix recorded with one chain cannot be used for reconstruction of measurement data using a different receive chain. This leads to huge amounts of data as system matrices have to be recorded for every set of drive field strength, particle system and receiver chain setting. In this paper the complexity of this is reduced by the factor of the receiver electronics. For each receive path of our MPI system the transfer function is recorded and stored on the measurement device. When loading the data, the transfer-function is corrected which allows the exchange of the system matrices data between receiver chains. To demonstrate this system matrix data is compared and a successful reconstruction of an in vivo dataset is shown.     Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009044, DOI: 10.18416/IJMPI.2020.200904