Research

Magnetic Particle Imaging in Research

MPI is the first molecular imaging technique simultaneously capable of: nanomolar sensitivity, absolute quantitation, resolution independent of depth, and with tracer detection from weeks to months. MPI excels in:

Sensitivity        Absolute Quantitation        Ease of Use       Flexible Tracers

Figure 1

Figure 1: Comparison of MPI to optical and MRI imaging. Fiducial markers containing 2 μL fluorescent (Cy5.5) probe and SPIO tracer mixture were implanted 1.0 and 2.8 mm below the skin. Optical imaging (left panel) shows signal attenuation with probe depth, while MRI slices (right panel) show signal dropouts from SPIOs, which are difficult to distinguish from areas of low signal intensity such as air. MPI (middle panel) maintains resolution, contrast and signal strength irregardless of tissue depth.

 

MPI is Fundamentally a Molecular Imaging Technique

MPI is complementary to existing molecular imaging techniques, giving scientists a versatile new tool when working with cancer imaging, cell tracking, and angiography.

Sensitivity

For the first time, scientists will be able to see less than 100 tagged cells and track them anywhere in body. MPI is able to harness the longevity of SPIO nanoparticles as a vascular or functional tracer, enabling imaging models that can quantitatively track disease development over time. These ground-breaking attributes will accelerate cell therapy research (Figure 2).

Figure 2

Figure 2: Tracking tail vein injected mesenchymal stem cells which directly lodge into the lungs.

Functional Imaging Anatomical Imaging
MPI PET OPTICAL MRI CT
Deep Tissue Imaging
Quantitative
< 100 cell sensitivity at any
depth, key for cell tracking
Vascular, functional and
cell based technologies
Translatable to the clinic
Exquisite resolution (≤ 1 mm)
Long term tracer stability

Table 1: Advantages of MPI in preclinical applications.

 

Absolute Quantitation

MPI is a positive contrast modality and measures an absolute linear quantitation of SPIO particles regardless of depth. This is key to longitudinal and reproducible data.

Figure 3

Figure 3: The signal in MPI is perfectly linear (R² = 0.99) with iron quantity, i.e., the input nanoparticle quantity. (Saritas et al., Journal of Magnetic Resonance, 229, 2013).

Ease of Use

MPI has the ease of use and workflow similar to optical imaging based on its speed and application workflow. MPI can image in milliseconds, supporting real-time imaging applications in cardiovascular and perfusion research at depths exceeding ultrasound’s abilities. The MPI workflow is straightforward and has simple acquisition settings to acquire quantitative data (i.e., no pulse sequences or radio).

Flexible Tracers

The strength of MPI lies in the flexibility, safety, and longevity of its tracers. For decades, researchers have worked with nanoparticles in MRI and CT, and many groups have demonstrated nanoparticles targeting inflammation, atherosclerotic plaques, and cancers, among others. MPI can perform these same experiments, but with greater contrast, sensitivity, and quantitation over MRI and CT. MPI tracers are also safe and translatable. Clinically approved iron oxide tracers are also available.