scholarly journals Annular Beam Shaping in Multiphoton Microscopy to Reduce Out-of-Focus Background

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Johan Borglin ◽  
Danni Wang ◽  
Nicholas J. Durr ◽  
Dag Hanstorp ◽  
Adela Ben-Yakar ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Multiphoton Microscopy ◽  
Laser Beams ◽  
Limiting Factor ◽  
Multiphoton Processes ◽  
Light Modulator ◽  
Annular Beam ◽  
Tissue Phantom ◽  
Imaging Depth ◽  
Annular Laser

Despite the inherent spatial confinement of multiphoton processes that arises from focusing through an objective, the maximum imaging depth in conventional multiphoton microscopy is ultimately limited by noise from out-of-focus fluorescence. This is particularly evident when imaging beyond shallow depths in highly scattering tissue as increased laser powers are necessary. The out-of-focus signal originates from multiphoton processes taking place primarily at shallow depths and deteriorates contrast and limits imaging depth. In this paper, annular laser beams are explored as a concept to reduce this background signal in multiphoton microscopy. The approach is theoretically verified by data from simulations and proof of principle is demonstrated on a custom-built experimental multiphoton microscopy platform. Annular laser beams were created by adopting wavefront control using a spatial light modulator and implemented for imaging tissue phantoms simulating turbid media and human skin ex vivo. The signal-to-background ratios were calculated and compared to images acquired with a traditional, filled-aperture Gaussian beam. Experiments in tissue phantom show an improvement in signal-to-background ratio of about 30% when using annular beam illumination in comparison to Gaussian illumination at specific depths. When laser power is not the limiting factor, this approach is expected to provide even greater benefits.

scholarly journals Towards Transabdominal Functional Photoacoustic Imaging of the Placenta: Improvement in Imaging Depth Through Optimization of Light Delivery

2021 ◽  
Author(s):  
Kristie Huda ◽  
Kenneth F. Swan ◽  
Cecilia T. Gambala ◽  
Gabriella C. Pridjian ◽  
Carolyn L. Bayer
Keyword(s):  
Delivery System ◽  
Light Propagation ◽  
Ex Vivo ◽  
Photoacoustic Imaging ◽  
Incidence Angle ◽  
Incident Angle ◽  
Placental Tissue ◽  
Light Delivery ◽  
Imaging Depth ◽  
The Impact

AbstractFunctional photoacoustic imaging of the placenta could provide an innovative tool to diagnose preeclampsia, monitor fetal growth restriction, and determine the developmental impacts of gestational diabetes. However, transabdominal photoacoustic imaging is limited in imaging depth due to the tissue’s scattering and absorption of light. The aim of this paper was to investigate the impact of geometry and wavelength on transabdominal light delivery. Our methods included the development of a multilayer model of the abdominal tissue and simulation of the light propagation using Monte Carlo methods. A bifurcated light source with varying incident angle of light, distance between light beams, and beam area was simulated to analyze the effect of light delivery geometry on the fluence distribution at depth. The impact of wavelength and the effects of variable thicknesses of adipose tissue and muscle were also studied. Our results showed that the beam area plays a major role in improving the delivery of light to deep tissue, in comparison to light incidence angle or distance between the bifurcated fibers. Longer wavelengths, with incident fluence at the maximum permissible exposure limit, also increases fluence within deeper tissue. We validated our simulations using a commercially available light delivery system and ex vivo human placental tissue. Additionally, we compared our optimized light delivery to a commercially available light delivery system, and conclude that our optimized geometry could improve imaging depth more than 1.6×, bringing the imaging depth to within the needed range for transabdominal imaging of the human placenta.

scholarly journals Correction of spherical aberration in multi-focal multiphoton microscopy with spatial light modulator

2017 ◽  
Vol 25 (6) ◽  
pp. 7055 ◽  
Author(s):  
Naoya Matsumoto ◽  
Alu Konno ◽  
Yasushi Ohbayashi ◽  
Takashi Inoue ◽  
Akiyuki Matsumoto ◽  
...  
Keyword(s):  
Spatial Light Modulator ◽  
Spherical Aberration ◽  
Multiphoton Microscopy ◽  
Light Modulator

scholarly journals Imaging depth extension of optical coherence tomography in rabbit eyes using optical clearing agents

2020 ◽  
Vol 245 (18) ◽  
pp. 1629-1636
Author(s):  
Ruiming Kong ◽  
Wenjuan Wu ◽  
Rui Qiu ◽  
Lei Gao ◽  
Fengxian Du ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Ex Vivo ◽  
Light Attenuation ◽  
Anterior Segment ◽  
Posterior Segment ◽  
Glycerol Solution ◽  
Optical Coherence ◽  
Optical Clearing ◽  
Imaging Depth

Optical coherence tomography has become an indispensable diagnostic tool in ophthalmology for imaging the retina and the anterior segment of the eye. However, the imaging depth of optical coherence tomography is limited by light attenuation in tissues due to optical scattering and absorption. In this study of rabbit eye both ex vivo and in vivo, optical coherence tomography imaging depth of the anterior and posterior segments of the eye was extended by using optical clearing agents to reduce multiple scattering. The sclera, the iris, and the ciliary body were clearly visualized by direct application of glycerol at an incision on the conjunctiva, and the posterior boundary of sclera and even the deeper tissues were detected by submerging the posterior segment of eye in glycerol solution ex vivo or by retro-bulbar injection of glycerol in vivo. The ex vivo rabbit eyes recovered to their original state in 60 s after saline-wash treatment, and normal optical coherence tomography images of the posterior segment of the sample eyes proved the self-recovery of in vivo performance. Signal intensities of optical coherence tomography images obtained before and after glycerol treatment were compared to analysis of the effect of optical clearing. To the best of our knowledge, this is the first study for imaging depth extension of optical coherence tomography in both the anterior and posterior segments of eye by using optical clearing agents.

scholarly journals Coherent combining of 49 laser beams from a multiple core optical fiber by a spatial light modulator

2010 ◽  
Vol 18 (5) ◽  
pp. 4783 ◽  
Author(s):  
J. Lhermite ◽  
E. Suran ◽  
V. Kermene ◽  
F. Louradour ◽  
A. Desfarges-Berthelemot ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Spatial Light Modulator ◽  
Laser Beams ◽  
Light Modulator ◽  
Coherent Combining

scholarly journals SipA Activation of Caspase-3 Is a Decisive Mediator of Host Cell Survival at Early Stages of Salmonella enterica Serovar Typhimurium Infection

2017 ◽  
Vol 85 (9) ◽  
Author(s):  
Anne McIntosh ◽  
Lynsey M. Meikle ◽  
Michael J. Ormsby ◽  
Beth A. McCormick ◽  
John M. Christie ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Actin Polymerization ◽  
Caspase 3 ◽  
Ex Vivo ◽  
Cell Types ◽  
Laser Scanning Microscopy ◽  
Limiting Factor ◽  
Dual Function ◽  
Content Type

ABSTRACT Salmonella invasion protein A (SipA) is a dual-function effector protein that plays roles in both actin polymerization and caspase-3 activation in intestinal epithelial cells. To date its function in other cell types has remained largely unknown despite its expression in multiple cell types and its extracellular secretion during infection. Here we show that in macrophages SipA induces increased caspase-3 activation early in infection. This activation required a threshold level of SipA linked to multiplicity of infection and may be a limiting factor controlling bacterial numbers in infected macrophages. In polymorphonuclear leukocytes, SipA or other Salmonella pathogenicity island 1 effectors had no effect on induction of caspase-3 activation either alone or in the presence of whole bacteria. Tagging of SipA with the small fluorescent phiLOV tag, which can pass through the type three secretion system, allowed visualization and quantification of caspase-3 activation by SipA-phiLOV in macrophages. Additionally, SipA-phiLOV activation of caspase-3 could be tracked in the intestine through multiphoton laser scanning microscopy in an ex vivo intestinal model. This allowed visualization of areas where the intestinal epithelium had been compromised and demonstrated the potential use of this fluorescent tag for in vivo tracking of individual effectors.

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