Volume 46, Issue 3 p. 1371-1383
Research Article

Bimodal intravascular volumetric imaging combining OCT and MPI

Sarah Latus

Sarah Latus

Institute of Medical Technology, Hamburg University of Technology, Hamburg, 21073 Germany

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Florian Griese

Corresponding Author

Florian Griese

Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, 20246 Germany

Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, 21073 Germany

Author to whom correspondence should be addressed. Electronic mail: [email protected].Search for more papers by this author
Matthias Schlüter

Matthias Schlüter

Institute of Medical Technology, Hamburg University of Technology, Hamburg, 21073 Germany

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Christoph Otte

Christoph Otte

Institute of Medical Technology, Hamburg University of Technology, Hamburg, 21073 Germany

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Martin Möddel

Martin Möddel

Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, 20246 Germany

Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, 21073 Germany

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Matthias Graeser

Matthias Graeser

Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, 20246 Germany

Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, 21073 Germany

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Thore Saathoff

Thore Saathoff

Institute of Medical Technology, Hamburg University of Technology, Hamburg, 21073 Germany

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Tobias Knopp

Tobias Knopp

Section for Biomedical Imaging, University Medical Center Hamburg-Eppendorf, Hamburg, 20246 Germany

Institute for Biomedical Imaging, Hamburg University of Technology, Hamburg, 21073 Germany

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Alexander Schlaefer

Alexander Schlaefer

Institute of Medical Technology, Hamburg University of Technology, Hamburg, 21073 Germany

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First published: 18 January 2019
Citations: 4
*Authors contributed equally

Abstract

Purpose

Intravascular optical coherence tomography (IVOCT) is a catheter-based image modality allowing for high-resolution imaging of vessels. It is based on a fast sequential acquisition of A-scans with an axial spatial resolution in the range of 5–10 μm, that is, one order of magnitude higher than in conventional methods like intravascular ultrasound or computed tomography angiography. However, position and orientation of the catheter in patient coordinates cannot be obtained from the IVOCT measurements alone. Hence, the pose of the catheter needs to be established to correctly reconstruct the three-dimensional vessel shape. Magnetic particle imaging (MPI) is a three-dimensional tomographic, tracer-based, and radiation-free image modality providing high temporal resolution with unlimited penetration depth. Volumetric MPI images are angiographic and hence suitable to complement IVOCT as a comodality. We study simultaneous bimodal IVOCT MPI imaging with the goal of estimating the IVOCT pullback path based on the 3D MPI data.

Methods

We present a setup to study and evaluate simultaneous IVOCT and MPI image acquisition of differently shaped vessel phantoms. First, the influence of the MPI tracer concentration on the optical properties required for IVOCT is analyzed. Second, using a concentration allowing for simultaneous imaging, IVOCT and MPI image data are acquired sequentially and simultaneously. Third, the luminal centerline is established from the MPI image volumes and used to estimate the catheter pullback trajectory for IVOCT image reconstruction. The image volumes are compared to the known shape of the phantoms.

Results

We were able to identify a suitable MPI tracer concentration of 2.5 mmol/L with negligible influence on the IVOCT signal. The pullback trajectory estimated from MPI agrees well with the centerline of the phantoms. Its mean absolute error ranges from 0.27 to 0.28 mm and from 0.25 mm to 0.28 mm for sequential and simultaneous measurements, respectively. Likewise, reconstructing the shape of the vessel phantoms works well with mean absolute errors for the diameter ranging from 0.11 to 0.21 mm and from 0.06 to 0.14 mm for sequential and simultaneous measurements, respectively.

Conclusions

Magnetic particle imaging can be used in combination with IVOCT to estimate the catheter trajectory and the vessel shape with high precision and without ionizing radiation.