Low-coherence Digital Holography Research Articles

Full-field snapshot phase-shifting low-coherence digital holography

Full-field snapshot phase-shifting low-coherence digital holography

Comparative oncology chemosensitivity assay for personalized medicine using low-coherence digital holography of dynamic light scattering from cancer biopsies

Nearly half of cancer patients who receive standard-of-care treatments fail to respond to their first-line chemotherapy, demonstrating the pressing need for improved methods to select personalized cancer therapies. Low-coherence digital holography has the potential to fill this need by performing dynamic contrast OCT on living cancer biopsies treated ex vivo with anti-cancer therapeutics. Fluctuation spectroscopy of dynamic light scattering under conditions of holographic phase stability captures ultra-low Doppler frequency shifts down to 10 mHz caused by light scattering from intracellular motions. In the comparative preclinical/clinical trials presented here, a two-species (human and canine) and two-cancer (esophageal carcinoma and B-cell lymphoma) analysis of spectral phenotypes identifies a set of drug response characteristics that span species and cancer type. Spatial heterogeneity across a centimeter-scale patient biopsy sample is assessed by measuring multiple millimeter-scale sub-samples. Improved predictive performance is achieved for chemoresistance profiling by identifying red-shifted sub-samples that may indicate impaired metabolism and removing them from the prediction analysis. These results show potential for using biodynamic imaging for personalized selection of cancer therapy.

Phase-Sensitive Intracellular Doppler Fluctuation Spectroscopy

Dynamic light scattering from three-dimensional intracellular motions in living tissues or biopsies creates dynamic speckle due to broadband Doppler shifts that are recorded as broadband spectra obtained from speckle fluctuation spectroscopy. Doppler frequency shifts from active intracellular motion extend across three orders of magnitude from 10 mHz to 10 Hz. Biodynamic imaging is a full-field optical coherence tomography technique performed with low-coherence digital holography. The holographic reconstruction allows phase recovery, but mechanical stability limitations favor homodyne detection over heterodyne detection because homodyne is relatively insensitive to phase drift. However, by obtaining phase-displacement distributions from consecutive frames, the phase excursions form a robust probability distribution. The phase-probability density function of the phase-displacement distribution captures average phase displacements over time and is used to reconstruct stable heterodyne spectra. Phase-sensitive biodynamic imaging is applied to detect Levy-stable distributions from living tissue that may reflect heavy-tailed anomalous transport within intracellular media.

Biodynamic digital holographic speckle microscopy for oocyte and embryo metabolic evaluation.

Assisted reproductive technologies seek to improve the success rate of pregnancies. Morphology scoring is a common approach to evaluate oocyte and embryo viability prior to embryo transfer in utero, but the efficacy of the method is low. We apply biodynamic imaging, based on dynamic light scattering and low-coherence digital holography, to assess the metabolic activity of oocytes and embryos. A biodynamic microscope, developed to image small and translucent biological specimens, is inserted into the bay of a commercial inverted microscope that can switch between conventional microscopy channels and biodynamic microscopy. We find intracellular Doppler spectral features that act as noninvasive proxies for embryo metabolic activity that may relate to embryo viability.

Low-coherence digital holography with a multireflection reference mirror.

A method for expanding the measurement range of low-coherence digital holography up to several times longer than the coherence length is proposed. The method was implemented with a multireflection reference mirror composed of partially and highly reflective mirrors, in conjunction with the Fourier transform method with spatial filtering for single-shot complex amplitude imaging, making it useful for observing a moving and deforming object. One of the features of the reference arm is that the measurement range is simply controlled by adjusting the position and angle of the highly reflective mirror. The measurement of objects with a general curved shape and a large step height was demonstrated.

低コヒーレンスディジタルホログラフィを用いた車体用ボディパネル中の光輝材分布の評価

低コヒーレンスディジタルホログラフィを用いた車体用ボディパネル中の光輝材分布の評価

Size measurement of Daphnia pulex using low-coherence Gabor digital holography

We measured the size of Daphnia pulex (D. pulex), which is an indicator organism used for examining toxicity, under freely-swimming and stress-free conditions, made possible by the post-focusing ability of digital holography (DH). This environmental measurement is a new application of DH. This implementation, which is a key point of this research, should be applicable to real on-site use in non-sterile and unstable mechanical situations. Through trial and error, we arrived at the simplest interferometer configuration using a single beam line that can withstand vibrations, a low-coherence light source for reducing coherent noise, and single-shot image capturing. Automatic size measurement based on DH with image processing was performed. The originality of this research is the quantitative size measurement and performance estimation achieved by comparing the results with those from conventional manual eye measurement using ordinary optical microscope observation and image processing software. The estimation also allowed us to determine the proper parameters in the image processing for DH measurement.

Intracellular Doppler Spectroscopy detects altered drug response in SKOV3 tumor spheroids with silenced or inhibited P-glycoprotein

Intracellular Doppler spectroscopy is a form of low-coherence digital holography based upon Doppler detection of scattered light that measures drug response/resistance in tumor spheroids, xenografts, and clinical biopsies. Multidrug resistance (MDR) is one of the main causes of ineffective cancer treatment. One MDR mechanism is mediated by the MDR1 gene that encodes the drug efflux pump P-glycoprotein (Pgp). Overexpression of Pgp in some cancers is associated with poor chemotherapeutic response. This paper uses intracellular Doppler spectroscopy to detect Pgp-mediated changes to drug response in 3D tissues grown from an ovarian cancer cell line (SKOV3). The SKOV3 cell line was incrementally exposed to cisplatin to create a cell line with increased Pgp expression (SKOV3cis). Subsequently, MDR1 in a subset of these cells was silenced in SKOV3cis using shRNA to create a doxycycline inducible, Pgp-silenced cell line (SKOV3cis-sh). A specific Pgp inhibitor, zosuquidar, was used to study the effects of Pgp inhibition on the Doppler spectra. Increased drug sensitivity was observed with Pgp silencing or inhibition as determined by drug IC50s of paclitaxel-response of silenced Pgp and doxorubicin-response of inhibited Pgp, respectively. These results indicate that intracellular Doppler spectroscopy can detect changes in drug response due to silencing or inhibition of a single protein associated with drug resistance with important consequences for personalized medicine.

Dual-wavelength digital holography with a low-coherence light source based on a quantum dot film.

This Letter proposes a dual-wavelength, low-coherence digital holography system with a single light source, which utilizes a quantum dot (QD) film as a wavelength converter. By changing the size of the QDs, the proposed method easily yields higher and more uniform illumination of any target wavelength, compared with bandpass-filtered light-emitting diodes. Fabrication parameters of the QD film for better conversion efficiency are discussed. Using this light source with the dual-wavelength reconstruction method extends the efficiency and range of nanoscale three-dimensional height measurements.

Low coherence digital holography microscopy based on the Lorenz-Mie scattering model.

We demonstrate the use of low spatial and temporal coherence holography microscopy, based on the Lorenz-Mie model, using the standard tungsten-halogen lamp present in an inverted microscope. An optical model is put forward to incorporate the effect of spectral width and different incidence angles of the incident light determined by the aperture at the back focal plane of the condenser lens. The model is validated for 899 nm diameter polystyrene microspheres in glycerol, giving a resolution of 0.4% for the index of refraction and 2.2% for the diameter of the particles.

Biodynamic imaging for phenotypic profiling of three-dimensional tissue culture.

Three-dimensional (3-D) tissue culture represents a more biologically relevant environment for testing new drugs compared to conventional two-dimensional cancer cell culture models. Biodynamic imaging is a high-content 3-D optical imaging technology based on low-coherence interferometry and digital holography that uses dynamic speckle as high-content image contrast to probe deep inside 3-D tissue. Speckle contrast is shown to be a scaling function of the acquisition time relative to the persistence time of intracellular transport and hence provides a measure of cellular activity. Cellular responses of 3-D multicellular spheroids to paclitaxel are compared among three different growth techniques: rotating bioreactor (BR), hanging-drop (HD), and nonadherent (U-bottom, UB) plate spheroids, compared with ex vivo living tissues. HD spheroids have the most homogeneous tissue, whereas BR spheroids display large sample-to-sample variability as well as spatial heterogeneity. The responses of BR-grown tumor spheroids to paclitaxel are more similar to those of ex vivo biopsies than the responses of spheroids grown using HD or plate methods. The rate of mitosis inhibition by application of taxol is measured through tissue dynamics spectroscopic imaging, demonstrating the ability to monitor antimitotic chemotherapy. These results illustrate the potential use of low-coherence digital holography for 3-D pharmaceutical screening applications.

MFD Measurement of a Six-Mode Fiber with Low-Coherence Digital Holography

This paper presents an application of low-coherence interferometry for measurement of mode field diameters (MFDs) of a few-mode fiber and shows its performance compared with another method using a mode multiplexer.

Intracellular Doppler Signatures of Platinum Sensitivity Captured by Biodynamic Profiling in Ovarian Xenografts.

Three-dimensional (3D) tissue cultures are replacing conventional two-dimensional (2D) cultures for applications in cancer drug development. However, direct comparisons of in vitro 3D models relative to in vivo models derived from the same cell lines have not been reported because of the lack of sensitive optical probes that can extract high-content information from deep inside living tissue. Here we report the use of biodynamic imaging (BDI) to measure response to platinum in 3D living tissue. BDI combines low-coherence digital holography with intracellular Doppler spectroscopy to study tumor drug response. Human ovarian cancer cell lines were grown either in vitro as 3D multicellular monoculture spheroids or as xenografts in nude mice. Fragments of xenografts grown in vivo in nude mice from a platinum-sensitive human ovarian cell line showed rapid and dramatic signatures of induced cell death when exposed to platinum ex vivo, while the corresponding 3D multicellular spheroids grown in vitro showed negligible response. The differences in drug response between in vivo and in vitro growth have important implications for predicting chemotherapeutic response using tumor biopsies from patients or patient-derived xenografts.

Speckle Reduction in Hologram Generation Based on Spherical Waves Synthesis Using Low-Coherence Digital Holography

A speckle reduction method based on a spherical waves synthesis with low-coherence digital holography for hologram generation is proposed. An object information is experimentally obtained from a number of recorded low-coherence digital holograms. A hologram is generated by synthesizing the fields of spherical waves with the obtained information. The performance of the proposed method as hologram generation from a distribution contained spike noises like speckles is confirmed. The image quality is evaluated by the speckle contrast of the reconstructed image.

Achromatic-phase-shifting low-coherence digital holography: theoretical analyses of zero-phase-shifting error condition and linear and nonlinear calibrations

Some methods for decreasing a measurement error derived from a phase-shifting error for broadband light in phase-shifting low-coherence digital holography are proposed based on theoretical analysis and numerical calculations. It is well-known that an achromatic-phase shifter based on a rotating polarizer drastically decreases the error, but it is found that a small error remains according to the imperfection of the achromatic-phase shifter. It is also found that an ideal achromatic-phase shifter perfectly eliminates the error only when the light source has a symmetrical spectrum. Furthermore, it is demonstrated that a simple linear calibration method decreases the error in a narrow range of optical path differences if a light source with an asymmetrical spectrum is used. Finally, a nonlinear calibration method that can further decrease the error in a wide range of optical path differences is discussed.

Simultaneous measurement of refractive index and thickness distributions using low-coherence digital holography and vertical scanning

The simultaneous measurement method of a refractive index distribution and a thickness distribution using low-coherence digital holography with a vertical scanning is proposed. The proposed method consists of a combination of digital holography and low-coherence interferometry. The introduction of a datum plane enables the measurement of both a refractive index distribution and a thickness distribution. By the optical experiment, the potential of the proposed method is confirmed.

Synthesis method from low-coherence digital holograms for improvement of image quality in holographic display

In holographic displays, it is undesirable to observe the speckle noises with the reconstructed images. A method for improvement of reconstructed image quality by synthesizing low-coherence digital holograms is proposed. It is possible to obtain speckleless reconstruction of holograms due to low-coherence digital holography. An image sensor records low-coherence digital holograms, and the holograms are synthesized by computational calculation. Two approaches, the threshold-processing and the picking-a-peak methods, are proposed in order to reduce random noise of low-coherence digital holograms. The reconstructed image quality by the proposed methods is compared with the case of high-coherence digital holography. Quantitative evaluation is given to confirm the proposed methods. In addition, the visual evaluation by 15 people is also shown.

Live tissue viability and chemosensitivity assays using digital holographic motility contrast imaging

Holographic optical coherence imaging is an en face form of optical coherence tomography that uses low-coherence digital holography as a coherence gate to select light from a chosen depth inside scattering tissue. By acquiring successive holograms at a high camera frame rate at a fixed depth, dynamic speckle provides information concerning dynamic light scattering from intracellular motility. Motility contrast imaging (MCI) uses living motion as a label-free and functional biomarker. MCI provides a new form of viability assay and also is applicable for proliferation and cytotoxicity assays. The results presented here demonstrate that low-coherence digital holography can extract viability information from biologically relevant three-dimensional (3D) tissue based on multicellular tumor spheroids by moving beyond the format of two-dimensional cell culture used for conventional high-content analysis. This paper also demonstrates the use of MCI for chemosensitivity assays on tumor exgrafts of excised ovarian cancer tumors responding to standard-of-care cisplatin chemotherapy. This ex vivo application extends the applicability of MCI beyond 3D tissue culture grown in vitro.

Selectable-wavelength low-coherence digital holography with chromatic phase shifter

We propose a new digital holography method using an ultra-broadband light source and a chromatic phase-shifter. The chromatic phase-shifter gives different frequency shifts for respective spectral frequencies so that the spectrum of the light reflected from the object can be measured to reveal the spectral property of the object, and arbitrary selection of signals in the temporal frequency domain enables single- and multi-wavelength measurements with wide dynamic range. A theoretical analysis, computer simulations, and optical experiments were performed to verify the advantages of the proposed method.