Single-shot two-dimensional spectroscopic magnetomotive optical coherence elastography with graphics processing unit acceleration

Abstract

Biomechanical contrast within tissues can be assessed based on the resonant frequency probed by spectroscopic magnetomotive optical coherence elastography (MM-OCE). However, to date, in vivo MM-OCE imaging has not been achieved, mainly due to the constraints on imaging speed. Previously, spatially-resolved spectroscopic contrast was achieved in a “multiple-excitation, multiple-acquisition” manner, where seconds of coil cooling time set between consecutive imaging frames lead to total acquisition times of tens of minutes. Here, we demonstrate an improved data acquisition speed by providing a single chirped force excitation prior to magnetomotion imaging with a BM-scan configuration. In addition, elastogram reconstruction was accelerated by exploiting the parallel computing capability of a graphics processing unit (GPU). The accelerated MM-OCE platform achieved data acquisition in 2.9 s and post-processing in 0.6 s for a 2048-frame BM-mode stack. In addition, the elasticity sensing functionality was validated on tissue-mimicking phantoms with high spatial resolution. For the first time, to the best of our knowledge, MM-OCE images were acquired from the skin of a living mouse, demonstrating its feasibility for in vivo imaging.

Magnetic particles in motion: magneto-motive imaging and sensing

“…More specifically, shear wave propagation, i.e. velocity, varies according to elastic properties of tissue, and magnetically-induced tissue motion is a suitable option to generate shear waves 149 , 150 . Pulsed magnetic excitation can generate shear waves for localized tissue elastography.…”

“…Recent research shows the first successful in vivo demonstrations of MM-OCE 149 , 151 . Previously, one major constraint of MM-OCE for in vivo applications was long image acquisition, which was caused by long inter-frame wait time to prevent coil overheating from repeated magnetic excitation.…”

“…Previously, one major constraint of MM-OCE for in vivo applications was long image acquisition, which was caused by long inter-frame wait time to prevent coil overheating from repeated magnetic excitation. By instead using a broadband magnetic force in a chirped waveform, mouse skin was imaged in vivo and results demonstrated an increased speed of at least 414x for acquisition and 131x for post-processing compared to previous methods 149 . In another study, MM-OCE was employed to assess heat-induced stiffness changes following magnetic hyperthermia treatment in a melanoma mouse model, showing theranostic potential of MNPs combined with MM-OCE 151 .…”

Existing and Potential Applications of Elastography for Measuring the Viscoelasticity of Biological Tissues In Vivo

“…One common imaging modality that magnetic actuation, whether static or dynamic, can be implemented with is OCT. Collectively, this technique is referred to as magnetomotive OCE (MM-OCE) [95][96][97]. MM-OCE allows for contactless manipulation, through which local MNP displacement in the subnanometer range can be detected.…”

Biomechanical sensing of in vivo magnetic nanoparticle hyperthermia-treated melanoma using magnetomotive optical coherence elastography

“…As a functional extension, the viscoelasticity of the specimen can be extracted as MM-OCE further analyzes the temporal characteristics of the magnetomotion (e.g. mechanical resonant frequency 44 , 50 , 51 , natural frequency 43 , 52 , or elastic wave propagation velocity 35 , 45 ).…”