High-speed spectral domain polarization- sensitive optical coherence tomography using a single camera and an optical switch at 1.3 mum.

Lee, Sang-Won,Jeong, Hyun-Woo,Kim, Beop-Min SPIE--the International Society for Optical Engine 2010 JOURNAL OF BIOMEDICAL OPTICS Vol.15 No.1

<P>We propose high-speed spectral domain polarization-sensitive optical coherence tomography (SD-PS-OCT) using a single camera and a 1 x 2 optical switch at the 1.3-mu m region. The PS-low coherence interferometer used in the system is constructed using free-space optics. The reflected horizontal and vertical polarization light rays are delivered via an optical switch to a single spectrometer by turns. Therefore, our system costs less to build than those that use dual spectrometers, and the processes of timing and triggering are simpler from the viewpoints of both hardware and software. Our SD-PS-OCT has a sensitivity of 101.5 dB, an axial resolution of 8.2 mu m, and an acquisition speed of 23,496 A-scans per second. We obtain the intensity, phase retardation, and fast axis orientation images of a rat tail tendon ex vivo. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3277668]</P>

Application of Cerenkov radiation generated in plastic optical fibers for therapeutic photon beam dosimetry.

Jang, Kyoung Won,Yagi, Takahiro,Pyeon, Cheol Ho,Yoo, Wook Jae,Shin, Sang Hun,Jeong, Chiyoung,Min, Byung Jun,Shin, Dongho,Misawa, Tsuyoshi,Lee, Bongsoo SPIE--the International Society for Optical Engine 2013 Journal of biomedical optics Vol.18 No.2

<P>A Cerenkov fiber-optic dosimeter (CFOD) is fabricated using plastic optical fibers to measure Cerenkov radiation induced by a therapeutic photon beam. We measured the Cerenkov radiation generated in optical fibers in various irradiation conditions to evaluate the usability of Cerenkov radiation for a photon beam therapy dosimetry. As a results, the spectral peak of Cerenkov radiation was measured at a wavelength of 515 nm, and the intensity of Cerenkov radiation increased linearly with increasing irradiated length of the optical fiber. Also, the intensity peak of Cerenkov radiation was measured in the irradiation angle range of 30 to 40 deg. In the results of Monte Carlo N-particle transport code simulations, the relationship between fluxes of electrons over Cerenkov threshold energy and energy deposition of a 6 MV photon beam had a nearly linear trend. Finally, percentage depth doses for the 6 MV photon beam could be obtained using the CFOD and the results were compared with those of an ionization chamber. Here, the mean dose difference was about 0.6%. It is anticipated that the novel and simple CFOD can be effectively used for measuring depth doses in radiotherapy dosimetry.</P>

Cerebral hemodynamic responses to seizure in the mouse brain: simultaneous near-infrared spectroscopy-electroencephalography study.

Lee, Seungduk,Lee, Mina,Koh, Dalkwon,Kim, Beop-Min,Choi, Jee Hyun SPIE--the International Society for Optical Engine 2010 JOURNAL OF BIOMEDICAL OPTICS Vol.15 No.3

<P>We applied near-infrared spectroscopy (NIRS) and electroencephalography (EEG) simultaneously on the mouse brain and investigated the hemodynamic response to epileptic episodes under pharmacologically driven seizure. gamma-butyrolactone (GBL) and 4-aminopyridine (4-AP) were applied to induce absence and tonic-clonic seizures, respectively. The epileptic episodes were identified from the single-channel EEG, and the corresponding hemodynamic changes in different regions of the brain were characterized by multichannel frequency-domain NIRS. Our results are the following: (i) the oxyhemoglobin level increases in the case of GBL-treated mice but not 4-AP-treated mice compared to the predrug state; (ii) the dominant response to each absence seizure is a decrease in deoxyhemolobin; (iii) the phase shift between oxy- and deoxyhemoglobin reduces in GBL-treated mice but no 4-AP-treated mice; and (iv) the spatial correlation of hemodynamics increased significantly in 4-AP-treated mice but not in GBL-treated mice. Our results shows that spatiotemporal tracking of cerebral hemodynamics using NIRS can be successfully applied to the mouse brain in conjunction with electrophysiological recording, which will support the study of molecular, cellular, and network origin of neurovascular coupling in vivo.</P>

Comparison of light-transmission and -backscattering methods in the measurement of red blood cell aggregation.

Nam, Jeong-Hun,Yang, Yijie,Chung, Seok,Shin, Sehyun SPIE--the International Society for Optical Engine 2010 JOURNAL OF BIOMEDICAL OPTICS Vol.15 No.2

<P>Light-transmission and light-backscattering methods are commonly used to determine red-blood-cell (RBC) aggregation. Even though the results reveal good correlations between the parameters that are measured by these two methods, the methods themselves yield quite different values. The objective of this research is to investigate and delineate the characteristics of the two optical methods. We measured RBC aggregation by using a newly developed microchip-based aggregometer. An orthogonal polarization technique, wherein multiple scattering causes polarized light to be depolarized and passed through an orthogonal polarizer, was applied to the backscattering method. Our results were also compared to those of conventional aggregometers [laser-assisted optical rotational cell analyzer (LORCA)], and revealed that the backscattering method yielded higher aggregation indices than the transmission method and LORCA. However, the backscattering method with orthogonal polarization yielded the same values of aggregation indices as the transmission method. These agreements between the two methods were also found in measurements of RBC aggregability in various concentrations of dextran solutions.</P>

Silver nanoparticle-induced degranulation observed with quantitative phase microscopy.

Yang, Wenzhong,Lee, Seungrag,Lee, Jiyong,Bae, Yoonsung,Kim, Dugyoung SPIE--the International Society for Optical Engine 2010 JOURNAL OF BIOMEDICAL OPTICS Vol.15 No.4

<P>Monitoring a degranulation process in a live mast cell is a quite important issue in immunology and pharmacology. Because the size of a granule is normally much smaller than the resolution limit of an optical microscope system, there is no direct real-time live cell imaging technique for observing degranulation processes except for fluorescence imaging techniques. In this research, we propose optical quantitative phase microscopy (QPM) as a new observation tool to study degranulation processes in a live mast cell without any fluorescence labeling. We measure the cell volumes and the cross sectional profiles (x-z plane) of an RBL-2H3 cell and a HeLa cell, before and after they are exposed to calcium ionophore A23187 and silver nanoparticles (AgNPs). We verify that the volume and the cross sectional line profile of the RBL-2H3 cell were changed significantly when it was exposed to A23187. When 50 microg/mL of AgNP is used instead of A23187, the measurements of cell volume and cross sectional profiles indicate that RBL-2H3 cells also follow degranulation processes. Degranulation processes for these cells are verified by monitoring the increase of intracellular calcium ([Ca(2+)](i)) and histamine with fluorescent methods.</P>

Effect of cross-linking with riboflavin and ultraviolet A on the chemical bonds and ultrastructure of human sclera.

Jung, Gyeong-Bok,Lee, Hui-Jae,Kim, Ji-Hye,Lim, Jin Ik,Choi, Samjin,Jin, Kyung-Hyun,Park, Hun-Kuk SPIE--the International Society for Optical Engine 2011 Journal of biomedical optics Vol.16 No.12

<P>This study examined the effect of the cross-linking with riboflavin-ultraviolet A (UVA) irradiation on the chemical bonds and ultrastructural changes of human sclera tissues using Raman spectroscopy and atomic force microscopy (AFM). Raman spectroscopy of the normal and cross-linked human sclera tissue revealed different types of the riboflavin-UVA and collagen interactions, which could be identified from their unique peaks, intensity, and shape. Raman spectroscopy can prove to be a powerful tool for examining the chemical bond of collagenous tissues at the molecular level. After riboflavin-UVA treatment, unlike a regular parallel arrangement of normal collagen fibrils, the AFM image revealed interlocking arrangements of collagen fibrils. The observed changes in the surface topography of the collagen fibrils, as well as in their chemical bonds in the sclera tissue, support the formation of interfibrilar cross-links in sclera tissues.</P>

Measurement of anisotropic reflection of flowing blood using optical coherence tomography.

Nam, Kweon-Ho,Jeong, Bosu,Jung, In Oh,Ha, Hojin,Kim, Ki Hean,Lee, Sang Joon SPIE--the International Society for Optical Engine 2011 JOURNAL OF BIOMEDICAL OPTICS Vol.16 No.12

<P>Light reflectance of blood is a complex phenomenon affected by hematocrit and red blood cell (RBC) aggregation (rouleaux formation). According to the hypothesis that RBC rouleaux are aligned with the direction of blood flow, the spatial alignment of RBC rouleaux, as well as their size and quantity in the blood, may also affect light reflectance. The present study aims to investigate the effect of the spatial alignment and distribution of RBC rouleaux on light reflection using optical coherence tomography (OCT). Blood flow velocity and reflectance profiles in a rat jugular-femoral bypass loop were simultaneously measured using a Doppler swept-source OCT system at various incident angles from -30 to +30 deg. The reflectance profiles of flowing blood show nonmonotonous decay with a local negative peak at the center of the tube. The profiles vary depending on the incident angle. This angular dependence is stronger at a higher angle of incidence. The anisotropic reflectance of flowing blood is consistent with the hypothesis on the spatial alignment of RBC rouleaux.</P>

In vivo imaging of human burn injuries with polarization-sensitive optical coherence tomography.

Kim, Ki Hean,Pierce, Mark C,Maguluri, Gopi,Park, B Hyle,Yoon, Sang June,Lydon, Martha,Sheridan, Robert,de Boer, Johannes F SPIE--the International Society for Optical Engine 2012 Journal of biomedical optics Vol.17 No.6

<P>The accurate determination of burn depth is critical in the clinical management of burn wounds. Polarization-sensitive optical coherence tomography (PS-OCT) has been proposed as a potentially non-invasive method for determining burn depth by measuring thermally induced changes in the structure and birefringence of skin, and has been investigated in pre-clinical burn studies with animal models and ex vivo human skin. In this study, we applied PS-OCT to the in-vivo imaging of two pediatric burn patients. Deep and superficial burned skins along with contralateral controls were imaged in 3D. The imaging size was 8 mm 6 mm 2 mm in width, length, and depth in the air respectively, and the imaging time was approximately 6 s per volume. Superficially burned skins exhibited the same layered structure as the contralateral controls, but more visible vasculature and reduced birefringence compared to the contralateral controls. In contrast, a deeply burned skin showed loss of the layered structure, almost absent vasculature, and smaller birefringence compared to superficial burns. This study suggested the vasculature and birefringence as parameters for characterizing burn wounds.</P>

Label-free optical control of arterial contraction.

Choi, Myunghwan,Yoon, Jonghee,Choi, Chulhee SPIE--the International Society for Optical Engine 2010 JOURNAL OF BIOMEDICAL OPTICS Vol.15 No.1

<P>The diameters of blood vessels, especially in the brain, change dynamically over time to provide sufficient blood supply as needed. No existing technique allows noninvasive control of vascular diameter in vivo. We report that label-free irradiation with a femtosecond pulsed laser can trigger blood vessel contraction in vivo. In response to laser irradiation, cultured vascular smooth muscle cells showed a rapid increase in calcium concentration, followed by cell contraction. In a murine thinned skull window model, laser irradiation focused in the arterial vessel wall caused localized vascular contraction, followed by recovery. The nonlinear nature of the pulsed laser allowed highly specific targeting of subcortical vessels without affecting the surrounding region. We believe that femtosecond pulsed laser irradiation will become a useful experimental tool in the field of vascular biology.</P>

Label-free optical activation of astrocyte in vivo.

Choi, Myunghwan,Yoon, Jonghee,Ku, Taeyun,Choi, Kyungsun,Choi, Chulhee SPIE--the International Society for Optical Engine 2011 Journal of biomedical optics Vol.16 No.7

<P>As the most abundant cell type in the central nervous system, astrocyte has been one of main research topics in neuroscience. Although various tools have been developed, at present, there is no tool that allows noninvasive activation of astrocyte in vivo without genetic or pharmacological perturbation. Here we report a noninvasive label-free optical method for physiological astrocyte activation in vivo using a femtosecond pulsed laser. We showed the laser stimulation robustly induced astrocytic calcium activation in vivo and further verified physiological relevance of the calcium increase by demonstrating astrocyte mediated vasodilation in the brain. This novel optical method will facilitate noninvasive physiological study on astrocyte function.</P>