Simultaneous imaging of widely differing particle concentrations in MPI: problem statement and algorithmic proposal for improvement

TY - JOUR

T1 - Simultaneous imaging of widely differing particle concentrations in MPI: problem statement and algorithmic proposal for improvement

AU - Boberg, Marija

AU - Gdaniec, Nadine

AU - Szwargulski, Patryk

AU - Werner, Franziska

AU - Möddel, Martin

AU - Knopp, Tobias

N1 - © 2021 Institute of Physics and Engineering in Medicine.

PY - 2021/4/23

Y1 - 2021/4/23

N2 - Magnetic particle imaging (MPI) is a tomographic imaging technique for determining the spatial distribution of superparamagnetic nanoparticles. Current MPI systems are capable of imaging iron masses over a wide dynamic range of more than four orders of magnitude. In theory, this range could be further increased using adaptive amplifiers, which prevent signal clipping. While this applies to a single sample, the dynamic range is severely limited if several samples with different concentrations or strongly inhomogeneous particle distributions are considered. One scenario that occurs quite frequently in pre-clinical applications is that a highly concentrated tracer bolus in the vascular system 'shadows' nearby organs with lower effective tracer concentrations. The root cause of the problem is the ill-posedness of the MPI imaging operator, which requires regularization for stable reconstruction. In this work, we introduce a simple two-step algorithm that increases the dynamic range by a factor of four. Furthermore, the algorithm enables spatially adaptive regularization, i.e. highly concentrated signals can be reconstructed with maximum spatial resolution, while low concentrated signals are strongly regularized to prevent noise amplification.

AB - Magnetic particle imaging (MPI) is a tomographic imaging technique for determining the spatial distribution of superparamagnetic nanoparticles. Current MPI systems are capable of imaging iron masses over a wide dynamic range of more than four orders of magnitude. In theory, this range could be further increased using adaptive amplifiers, which prevent signal clipping. While this applies to a single sample, the dynamic range is severely limited if several samples with different concentrations or strongly inhomogeneous particle distributions are considered. One scenario that occurs quite frequently in pre-clinical applications is that a highly concentrated tracer bolus in the vascular system 'shadows' nearby organs with lower effective tracer concentrations. The root cause of the problem is the ill-posedness of the MPI imaging operator, which requires regularization for stable reconstruction. In this work, we introduce a simple two-step algorithm that increases the dynamic range by a factor of four. Furthermore, the algorithm enables spatially adaptive regularization, i.e. highly concentrated signals can be reconstructed with maximum spatial resolution, while low concentrated signals are strongly regularized to prevent noise amplification.

KW - Algorithms

KW - Magnetite Nanoparticles

KW - Tomography

U2 - 10.1088/1361-6560/abf202

DO - 10.1088/1361-6560/abf202

M3 - SCORING: Journal article

C2 - 33765669

VL - 66

JO - PHYS MED BIOL

JF - PHYS MED BIOL

SN - 0031-9155

IS - 9

M1 - 095004

ER -