Advances in Vascular Diagnostics using Magnetic Particle Imaging MPI for Blood Circulation Assessment, 2024, Pacheco et al.

Advances in Vascular Diagnostics using Magnetic Particle Imaging MPI for Blood Circulation Assessment
Marisa O Pacheco; Isabelle K Gerzenshtein; Whitney L Stoppel; Carlos M Rinaldi-Ramos

Rapid and accurate assessment of conditions characterized by altered blood flow, cardiac blood pooling, or internal bleeding is crucial for diagnosing and treating various clinical conditions. While widely used imaging modalities such as magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound offer unique diagnostic advantages, they fall short for specific indications due to limited penetration depth and prolonged acquisition times.

Magnetic particle imaging (MPI), an emerging tracer-based technique, holds promise for blood circulation assessments, potentially overcoming existing limitations with reduction in background signals and high temporal and spatial resolution, below the millimeter scale. Successful imaging of blood pooling and impaired flow necessitates tracers with diverse circulation half-lives optimized for MPI signal generation.

Recent MPI tracers show potential in imaging cardiovascular complications, vascular perforations, ischemia, and stroke. The impressive temporal resolution and penetration depth also position MPI as an excellent modality for real-time vessel perfusion imaging via functional MPI (fMPI).

This review summarizes advancements in optimized MPI tracers for imaging blood circulation and analyzes the current state of pre-clinical applications. This work discusses perspectives on standardization required to transition MPI from a research endeavor to clinical implementation and explore additional clinical indications that may benefit from the unique capabilities of MPI.

Link | PDF (Advanced Healthcare Materials)

 

Original description of technique —

Tomographic imaging using the nonlinear response of magnetic particles (2005)
Gleich, Bernhard; Weizenecker, Jürgen

The use of contrast agents and tracers in medical imaging has a long history1–7 . They provide important information for diagnosis and therapy, but for some desired applications, a higher resolution is required than can be obtained using the currently available medical imaging techniques. Consider, for example, the use of magnetic tracers in magnetic resonance imaging: detection thresholds for in vitro 8 and in vivo 9 imaging are such that the background signal from the host tissue is a crucial limiting factor.

A sensitive method for detecting the magnetic particles directly is to measure their magnetic fields using relaxometry10 ; but this approach has the drawback that the inverse problem (associated with transforming the data into a spatial image) is ill posed and therefore yields low spatial resolution. Here we present a method for obtaining a high-resolution image of such tracers that takes advantage of the nonlinear magnetization curve of small magnetic particles.

Initial ‘phantom’ experiments are reported that demonstrate the feasibility of the imaging method. The resolution that we achieve is already well below 1 mm. We evaluate the prospects for further improvement, and show that the method has the potential to be developed into an imaging method characterized by both high spatial resolution as well as high sensitivity.

Link | PDF (Nature)