Single-shot 3-D wide-field fluorescence imaging with a computational miniature mesoscope

Single-shot 3D wide-field fluorescence imaging with a Computational Miniature Mesoscope
Online cover – a Computational Miniature Mesoscope (CM2). Image credit: Xue et al., Science Advances, doi:10.1126/sciadv.abb7508

The online feature cover photograph on Science Advances this week displays fluorescence imaging with a computational miniature mesoscope (CM2). The technique of fluorescence imaging is an essential tool for biologists and neuroscientists; however, conventional microscopes and miniaturized microscopes (miniscopes) are constrained by limited space-bandwidth product—a measurement of the information capacity of an optical system, shallow depth of field and an inability to resolve three-dimensional (3-D) distributed emitters. To overcome existing limits, Yujia Xue and a team of researchers in electrical and computer engineering, biology, neurophotonics and biomedical engineering at Boston University, U.S., developed a light and compact mesoscope known as the computational miniature mesoscope (CM2).

The new platform integrated a microlens for imaging and an LED array for excitation within the same setup. The device performed single-shot 3-D imaging and facilitated a 10-fold field-of-view gain and a 100-fold depth-of-field improvement, compared to existing miniscopes. Xue et al. tested the device with fluorescent beads and fibers alongside phantom experiments to measure the effects of bulk scattering and background fluorescence. The team discusses the practicality of this mesoscope for broad applications in biomedicine and 3-D neural recording.

Advancing fluorescence microscopy

Fluorescence microscopy is a key technique in fundamental biology and systems neuroscience. Recent technological developments are aimed at overcoming barriers of scale to investigate individual neurons of only a few microns in size. For example, macroscopes, mesolens microscopes and two-photon microscopes have begun to bridge this scale; however, the development of such imaging systems is limited by scale-dependent geometric aberrations of optical elements. The achievable field of view (FOV) is also limited by the system’s shallow depth of field in many bioimaging applications. Researchers are also focused on miniaturizing the technology to allow in vivo imaging in freely behaving animals. For example, miniaturized microscopes known as ‘miniscopes’ have gained unprecedented access to neural signals, although the systems remain restricted by their optics, much like their fluorescence microscopy counterparts. Xue et al. therefore introduced and demonstrated a computational miniature microscope (CM2) with large-scale, 3-D fluorescence measurements on a compact, light-weight platform.

Single-shot 3D wide-field fluorescence imaging with a Computational Miniature Mesoscope
Single-shot 3D fluorescence CM2. (A) The CM2 combines an MLA optics and light-emitting diode (LED) array excitation in a compact and lightweight platform. (B) Picture of the CM2 prototype (the electric wires and the sensor driver are omitted). Photo credit: Yujia Xue, Boston University. (C) CM2 measurement on 100-μm fluorescent particles suspended in clear resin. (D) Projected view of the CM2 reconstructed volume (7.0 mm by 7.3 mm by 2.5 mm) and three zoom-in regions with orthogonal views. Scale bars, 500 μm. CMOS, complementary metal-oxide semiconductor. Credit: Science Advances, doi: 10.1126/sciadv.abb7508

The mechanism-of-action of the computational miniature mesoscope (CM2)

The team used simple optics in the setup to accomplish space-bandwidth product (SBP) improvement and 3-D imaging capabilities without the need for mechanical scanning. The technique bypassed the physical limits of the integrated optics by jointly designing the hardware

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