Volume 28 Issue 2 | Journal of Biomedical Optics

Journal of Biomedical Optics

VOL. 28 · NO. 2 | February 2023

CONTENTS

IN THIS ISSUE

General (2)

Imaging (4)

Microscopy (3)

Errata (1)

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General

Development of a platform for broadband, spectra-fitted, tissue optical phantoms

Alec Walter, E. Duco Jansen

Journal of Biomedical Optics, Vol. 28, Issue 02, 025001, (February 2023) https://doi.org/10.1117/1.JBO.28.2.025001

TOPICS: Pigments, Absorption, Tissues, Optical properties, Scattering, Diffuse reflectance spectroscopy, Skin, Optical phantoms, Light absorption, Epoxies

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Open-sourced Raman spectroscopy data processing package implementing a baseline removal algorithm validated from multiple datasets acquired in human tissue and biofluids

Guillaume Sheehy, Fabien Picot, Frédérick Dallaire, Katherine Ember, Tien Nguyen, Kevin Petrecca, Dominique Trudel, Frédéric Leblond

Journal of Biomedical Optics, Vol. 28, Issue 02, 025002, (February 2023) https://doi.org/10.1117/1.JBO.28.2.025002

TOPICS: Raman spectroscopy, Data processing, Tissues, Equipment, Bubbles, Biological samples, Raman scattering, Fluorescence, Aluminum, Spectroscopy

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Imaging

Periodic-net: an end-to-end data driven framework for diffuse optical imaging of breast cancer from noisy boundary data

Nazish Murad, Min-Chun Pan, Ya-Fen Hsu

Journal of Biomedical Optics, Vol. 28, Issue 02, 026001, (February 2023) https://doi.org/10.1117/1.JBO.28.2.026001

TOPICS: Image restoration, Education and training, Scattering, Absorption, Diffuse optical imaging, Data modeling, Optical properties, Medical image reconstruction, Reconstruction algorithms, Deep learning

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Improved in vivo optical coherence tomography imaging of animal peripheral nerves using a prism nerve holder

Ilyas Saytashev, Yong-Chul Yoon, Benjamin Vakoc, Srikanth Vasudevan, Daniel Hammer

Journal of Biomedical Optics, Vol. 28, Issue 02, 026002, (February 2023) https://doi.org/10.1117/1.JBO.28.2.026002

TOPICS: Nerve, Prisms, Optical coherence tomography, Animals, In vivo imaging, Coherence imaging, Biomedical optics, Optical imaging, Mirrors, Nervous system

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Significance

Modern optical volumetric imaging modalities, such as optical coherence tomography (OCT), provide enormous information about the structure, function, and physiology of living tissue. Although optical imaging achieves lateral resolution on the order of the wavelength of light used, and OCT achieves axial resolution on a similar micron scale, tissue optical properties, particularly high scattering and absorption, limit light penetration to only a few millimeters. In addition, in vivo imaging modalities are susceptible to significant motion artifacts due to cardiac and respiratory function. These effects limit access to artifact-free optical measurements during peripheral neurosurgery to only a portion of the exposed nerve without further modification to the procedure.

Aim

We aim to improve in vivo OCT imaging during peripheral neurosurgery in small and large animals by increasing the amount of visualized nerve volume as well as suppressing motion of the imaged area.

Approach

We designed a nerve holder with embedded mirror prisms for peripheral nerve volumetric imaging as well as a specific beam steering strategy to acquire prism and direct view volumes in one session with minimal motion artifacts.

Results

The axially imaged volumes from mirror prisms increased the OCT signal intensity by >22 dB over a 1.25-mm imaging depth in tissue-mimicking phantoms. We then demonstrated the new imaging capabilities in visualizing peripheral nerves from direct and side views in living rats and minipigs using a polarization-sensitive OCT system. Prism views have shown nerve fascicles and vasculature from the bottom half of the imaged nerve which was not visible in direct view.

Conclusions

We demonstrated improved OCT imaging during neurosurgery in small and large animals by combining the use of a prism nerve holder with a specifically designed beam scanning protocol. Our strategy can be applied to existing OCT imaging systems with minimal hardware modification, increasing the nerve tissue volume visualized. Enhanced imaging depth techniques may lead to a greater adoption of structural and functional optical biomarkers in preclinical and clinical medicine.

Multimodal fluorescence lifetime imaging and optical coherence tomography for longitudinal monitoring of tissue-engineered cartilage maturation in a preclinical implantation model

Xiangnan Zhou, Anne Haudenschild, Cai Li, Laura Marcu

Journal of Biomedical Optics, Vol. 28, Issue 02, 026003, (February 2023) https://doi.org/10.1117/1.JBO.28.2.026003

TOPICS: Tissues, Optical coherence tomography, Cartilage, Biological samples, In vivo imaging, Fluorescence, Quantum channels, In vitro testing, Fluorescence lifetime imaging, Nondestructive evaluation

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Significance

Cartilage tissue engineering is a promising strategy for effective curative therapies for treatment of osteoarthritis. However, tissue engineers depend predominantly on time-consuming, expensive, and destructive techniques as quality control to monitor the maturation of engineered cartilage. This practice can be impractical for large-scale biomanufacturing and prevents spatial and temporal monitoring of tissue growth, which is critical for the fabrication of clinically relevant-sized cartilage constructs. Nondestructive multimodal imaging techniques combining fluorescence lifetime imaging (FLIm) and optical coherence tomography (OCT) hold great potential to address this challenge.

Aim

The feasibility of using multimodal FLIm–OCT for nondestructive, spatial, and temporal monitoring of self-assembled cartilage tissue maturation in a preclinical mouse model is investigated.

Approach

Self-assembled cartilage constructs were developed for 4 weeks in vitro followed by 4 weeks of in vivo maturation in nude mice. Sterile and nondestructive in situ multispectral FLIm and OCT imaging were carried out at multiple time points (t = 2, 4, and 8 weeks) during tissue development. FLIm and 3D volumetric OCT images were reconstructed and used for the analysis of tissue biochemical homogeneity, morphology, and structural integrity. A biochemical homogeneity index was computed to characterize nonhomogeneous tissue growth at different time points. OCT images were validated against histology.

Results

FLIm detects heterogenous extracellular matrix (ECM) growth of tissue-engineered cartilage. The outer edge of the tissue construct exhibited longer fluorescence lifetime in 375 to 410 and 450 to 485 nm spectral channels, indicating increase in collagen content. Significant (p < 0.05) decrease of construct homogeneity index was observed between t = 2 weeks and t = 4 weeks. Both FLIm and OCT images revealed defects (voids) at the center of the tissue construct during in vitro culture (t = 2 and 4 weeks). Cyst formation during in vivo culture was detected by OCT and confirmed with histology.

Conclusions

The ability of multimodal FLIm–OCT to nondestructively monitor the heterogenous growth of engineered tissue constructs in situ is demonstrated. Spatial and temporal variation of construct ECM component was detected by FLIm. OCT reveals structural defects (voids and cysts). This multimodal approach has great potential to replace costly destructive tests in the manufacturing of tissue-engineered medical products, facilitating their clinical translation.

X-ray Cherenkov-luminescence tomography reconstruction with a three-component deep learning algorithm: Swin transformer, convolutional neural network, and locality module

Jinchao Feng, Hu Zhang, Mengfan Geng, Hanliang Chen, Kebin Jia, Zhonghua Sun, Zhe Li, Xu Cao, Brian Pogue

Journal of Biomedical Optics, Vol. 28, Issue 02, 026004, (February 2023) https://doi.org/10.1117/1.JBO.28.2.026004

TOPICS: Image restoration, Reconstruction algorithms, X-rays, Tomography, Transformers, Education and training, Image quality, Quantum deep learning, Detection and tracking algorithms, In vivo imaging

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Significance

X-ray Cherenkov–luminescence tomography (XCLT) produces fast emission data from megavoltage (MV) x-ray scanning, in which the excitation location of molecules within tissue is reconstructed. However standard filtered backprojection (FBP) algorithms for XCLT sinogram reconstruction can suffer from insufficient data due to dose limitations, so there are limits in the reconstruction quality with some artifacts. We report a deep learning algorithm for XCLT with high image quality and improved quantitative accuracy.

Aim

To directly reconstruct the distribution of emission quantum yield for x-ray Cherenkov-luminescence tomography, we proposed a three-component deep learning algorithm that includes a Swin transformer, convolution neural network, and locality module model.

Approach

A data-to-image model x-ray Cherenkov-luminescence tomography is developed based on a Swin transformer, which is used to extract pixel-level prior information from the sinogram domain. Meanwhile, a convolutional neural network structure is deployed to transform the extracted pixel information from the sinogram domain to the image domain. Finally, a locality module is designed between the encoder and decoder connection structures for delivering features. Its performance was validated with simulation, physical phantom, and in vivo experiments.

Results

This approach can better deal with the limits to data than conventional FBP methods. The method was validated with numerical and physical phantom experiments, with results showing that it improved the reconstruction performance mean square error (>94.1 % ), peak signal-to-noise ratio (>41.7 % ), and Pearson correlation (>19 % ) compared with the FBP algorithm. The Swin-CNN also achieved a 32.1% improvement in PSNR over the deep learning method AUTOMAP.

Conclusions

This study shows that the three-component deep learning algorithm provides an effective reconstruction method for x-ray Cherenkov-luminescence tomography.

Microscopy

Hardware-software co-design of an open-source automatic multimodal whole slide histopathology imaging system

Bin Li, Michael S. Nelson, Jenu V. Chacko, Nathan Cudworth, Kevin W. Eliceiri

Journal of Biomedical Optics, Vol. 28, Issue 02, 026501, (February 2023) https://doi.org/10.1117/1.JBO.28.2.026501

TOPICS: Education and training, Histopathology, Image resolution, Imaging systems, Denoising, Second harmonic generation, Image enhancement, Image quality, Data modeling, Tissues

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Multifaceted mirror array illuminator for fluorescence excitation-scanning spectral imaging microscopy

Marina Parker, Samuel A. Mayes, Craig Browning, Joshua Deal, Samantha Gunn-Mayes, Naga Annamdevula, Thomas Rich, Silas Leavesley

Journal of Biomedical Optics, Vol. 28, Issue 02, 026502, (February 2023) https://doi.org/10.1117/1.JBO.28.2.026502

TOPICS: Light emitting diodes, Microscopes, Fluorescence, Mirrors, Signal to noise ratio, Tunable filters, Imaging systems, Prototyping, Autofluorescence, Optical filters

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Significance

Hyperspectral imaging (HSI) technologies offer great potential in fluorescence microscopy for multiplexed imaging, autofluorescence removal, and analysis of autofluorescent molecules. However, there are also associated trade-offs when implementing HSI in fluorescence microscopy systems, such as decreased acquisition speed, resolution, or field-of-view due to the need to acquire spectral information in addition to spatial information. The vast majority of HSI fluorescence microscopy systems provide spectral discrimination by filtering or dispersing the fluorescence emission, which may result in loss of emitted fluorescence signal due to optical filters, dispersive optics, or supporting optics, such as slits and collimators. Technologies that scan the fluorescence excitation spectrum may offer an approach to mitigate some of these trade-offs by decreasing the complexity of the emission light path.

Aim

We describe the development of an optical technique for hyperspectral imaging fluorescence excitation-scanning (HIFEX) on a microscope system.

Approach

The approach is based on the design of an array of wavelength-dependent light emitting diodes (LEDs) and a unique beam combining system that uses a multifurcated mirror. The system was modeled and optimized using optical ray trace simulations, and a prototype was built and coupled to an inverted microscope platform. The prototype system was calibrated, and initial feasibility testing was performed by imaging multilabel slide preparations.

Results

We present results from optical ray trace simulations, prototyping, calibration, and feasibility testing of the system. Results indicate that the system can discriminate between at least six fluorescent labels and autofluorescence and that the approach can provide decreased wavelength switching times, in comparison with mechanically tuned filters.

Conclusions

We anticipate that LED-based HIFEX microscopy may provide improved performance for time-dependent and photosensitive assays.

Cable-free brain imaging for multiple free-moving animals with miniature wireless microscopes

Yangzhen Wang, Zhongtian Ma, Wenzhao Li, Feng Su, Chong Wang, Wei Xiong, Changhui Li, Chen Zhang

Journal of Biomedical Optics, Vol. 28, Issue 02, 026503, (February 2023) https://doi.org/10.1117/1.JBO.28.2.026503

TOPICS: Animals, Microscopes, Imaging systems, Brain imaging, Neurons, Batteries, Image quality, Video, Neuroimaging, Control systems

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Errata

Tissue harvest with a laser microbiopsy (Erratum)

Jason King, Nitesh Katta, Sapun Parekh, Thomas Milner, James Tunnell

Journal of Biomedical Optics, Vol. 28, Issue 02, 029801, (February 2023) https://doi.org/10.1117/1.JBO.28.2.029801

TOPICS: Tissues, Laser cutting, Plasma, Medical laser equipment, Laser ablation, Biomedical engineering

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