Mechanical resonance frequencies in rat and human tissue samples. (a) Rat muscle and (b) rat lung tissue. (c) Human adipose tissue and tumor. The red and blue boxes indicate the spatial regions from which the displacement amplitudes shown in the plots were calculated. (d) MM-OCE images of human adipose and tumor. At low magnetomotive frequency (20 Hz shown) the adipose is highlighted while at higher frequencies (160 Hz shown) the stiffer tumor region gives a higher magnetomotive signal.
Many diseases cause a change in the mechanical properties of body tissues. Tumor tissues and inflamed regions are stiffer than healthy tissues, thus allowing physicians to make preliminary diagnosis of patients’ condition by using their hands to feel.
Researchers from the University of Illinois at Urbana-Champaign have discovered a way to identify the boundary of tumor tissue by detecting the difference in viscoelastic properties between diseased and healthy tissues. Using a spectroscopic approach in a method termed magnetomotive optical coherence elastography (MM-OCE), the team has successfully revealed the geometry of a heterogeneous tumor sample, as published in the journal Physics in Medicine and Biology.
To achieve this, cells in a tissue mass are labeled with magnetic nanoparticles, which are subsequently excited with an external magnetic field. This enables scientists to monitor the dynamics of the tissue’s response and determine its elastic properties.
In this study, the researchers evaluated the utility of spectroscopic MM-OCE in tissue phantoms, as well as biological tissues from humans and rats. When electromagnetic fields at different excitation frequencies were applied, the scientists were able to measure the tissues’ response as changes in mechanical vibration spectrum, by using optical coherence tomography. As the vibration spectrum is dependent on the elasticity of the sample, edges between different types of tissue could be detected, regardless of whether they were located side-by-side, or on top of one another. This technology could one day be utilized to reveal how far a cancer has metastasized, or to isolate a mass of tumor before surgery.
However, a major challenge of translating this discovery into human clinical settings remains in the need for loading of magnetic nanoparticles into human tissues. Further studies are required to better understand the kinetics of magnetic nanoparticles inside the human body, and establish the safety profile of such technique. Nonetheless, this technology can provide additional information in situations whereby tissues are already loaded with magnetic nanoparticles, for instance, in magnetic hyperthermia therapy, or in MRI requiring magnetic nanoparticles for contrast enhancement. Already, certain class of nanoparticles such as iron oxide nanoparticles, have been certified safe for human application by the US Food and Drug Administration (FDA).
Study in Physics in Medicine and Biology: Mechanical contrast in spectroscopic magnetomotive optical coherence elastography…
