Optimization of a flexible fiber-optic probe for epi-mode quantitative phase imaging

Quantitative Phase Imaging IX

Kaza

et al. 2023

Self Cite

Quantitative Phase Imaging (QPI) has become a mainstay imaging technique in the biomedical sciences to study cells and other biological processes. Traditional QPI techniques are transmission-based and, thus, limited to thin samples. Over the past few years, multiple 3D QPI tools have emerged attempting to overcome this limitation and provide cross-sectional phase information of thicker samples. However, most of these techniques remain transmission-based, which constrains their ability to image samples thicker than a few mean free scattering lengths. Recently, we have developed quantitative oblique back-illumination microscopy (qOBM) as an epimode technique that enables label-free quantitative phase imaging of thick samples with tomographic crosssectioning. Like in most 3D QPI instances, qOBM requires multiple captures to render a quantitative phase image. Specifically, qOBM requires four raw captures, obtained by illuminating the sample obliquely from four different directions, to reconstruct the quantitative phase. This muti-capture scheme hinders qOBM’s ability to investigate valuable fast dynamic processes, such as blood flow, as well as its usability in some in-vivo applications. Here, we present a deep-learning enabled single-capture version of qOBM that quadruples the system’s imaging speed and prevents motion artifacts. To this end, we have trained a U-Net GAN to learn the qOBM reconstruction from a single capture obtained with oblique illumination. We show the capabilities and limitations of this approach, as well as some of the novel applications that this system enables, such as in-vivo high-resolution non-invasive blood flow quantitative phase imaging.

Section: Discussionmentioning

confidence: 99%

Single capture quantitative phase imaging with tomographic sectioning

Quantitative Phase Imaging IX

Kaza

et al. 2023

Self Cite

“…To test the phase staining effect of AA, we use a qOBM setup with an inverted microscopy geometry [1][2][3][4], as shown in Figure 1(a). Four LEDs at 720nm serve as the illumination light sources, and they are connected to four multimode fibers, forming 90 degrees in the azimuthal angle from each other, as viewed from the top of the setup (Figure 1(a) bottom-right inset).…”

Section: Methodsmentioning

confidence: 99%

“…Quantitative oblique back-illumination microscopy (qOBM) enables quantitative phase imaging (QPI) of arbitrarily thick scattering biological samples by using oblique back-illumination derived from multiply scattered light within thick samples [1][2][3][4][5]. Even though qOBM can conveniently access the refractive index information in-vivo by working in epi-mode, it it possesses the same low contrast for cell nuclei as QPI.…”

Section: Introductionmentioning

confidence: 99%

Quantitative oblique back-illumination microscopy with enhanced nuclear phase contrast using acetic acid

Jacobs

Quantitative Phase Imaging IX

et al. 2023

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Quantitative oblique back-illumination microscopy (qOBM) enables quantitative phase imaging (QPI) in thick samples using epi-illumination. While qOBM offers unprecedented access to refractive index (RI) information in arbitrarily thick scattering samples, QPI-based (or RI index based) imaging still suffers from low cell nuclear contrast, which important for disease detection, including cancer. In this work, we use the acetowhitening effect of acetic acid to enhance the nuclear phase contrast of thick fresh tissue samples. Imaging results from brain samples are presented. Acetic acid phase staining may have important implications for in-vivo QPI-based disease detection

“…To overcome the important limitation, we have introduced a technique called Quantitative Oblique Back-illumination Microscopy (qOBM) which achieves quantitative phase imaging and refractive index tomography in thick scattering tissues [2][3][4][5]. Specifically, quantitative phase can be reconstructed by deconvolving captured differential phase images with optical transfer functions derived from the pupil function of the system and the angular distribution of light at the focal plane [2][3][4][5]. In this work, we report a compact handheld qOBM imaging system, suitable for real-time in-vivo clinical inspection and diagnosis of diseases.…”

Section: Introductionmentioning

confidence: 99%

“…The system works with epi-illumination from LEDs, which offers direct access to cellular/sub-cellular information in contact mode. The high-resolution (0.7NA) handheld probe is optimized for phase signal-to-noise ratio [5]. Here we summarize the handheld system characteristics and show results comprising images of a 9L gliosarcoma rat brain tumor mode acquired with the handheld probe.…”

Section: Introductionmentioning

confidence: 99%

Handheld quantitative phase imaging probe for in-vivo brain tumor margin assessment

Label-Free Biomedical Imaging and Sensing (LBIS) 2023

Jacobs

et al. 2023

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Quantitative phase imaging (QPI) enables label-free optical-path-length measurement of biological samples with nanometer-scale sensitivity, which offers unparalleled access to important histological and biophysical properties of cells and tissues. However, traditional QPI methods require a transmission-based optical geometry and are thus restricted to thin samples, which prevents the use of QPI for in-vivo applications. In this work, we present the design, characterization, and experimental validation of a handheld rigid probe for QPI with epi-illumination, using an optimized lighting configuration to achieve high phase-contrast sensitivity. The approach is based on a recently developed technology called quantitative oblique back illumination microscopy (qOBM). We demonstrate the real-time operation of our system with the future goal of applying it to help guide human brain tumor margin assessment intraoperatively in vivo, among many other potential applications.