3D resolved mapping of optical aberrations in thick tissues (original) (raw)
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Enhancing image quality in cleared tissue with adaptive optics
Journal of biomedical optics, 2016
Our ability to see fine detail at depth in tissues is limited by scattering and other refractive characteristics of the tissue. For fixed tissue, we can limit scattering with a variety of clearing protocols. This allows us to see deeper but not necessarily clearer. Refractive aberrations caused by the bulk index of refraction of the tissue and its variations continue to limit our ability to see fine detail. Refractive aberrations are made up of spherical and other Zernike modes, which can be significant at depth. Spherical aberration that is common across the imaging field can be corrected using an objective correcting collar, although this can require manual intervention. Other aberrations may vary across the imaging field and can only be effectively corrected using adaptive optics. Adaptive optics can also correct other aberrations simultaneously with the spherical aberration, eliminating manual intervention and speeding imaging. We use an adaptive optics two-photon microscope to ...
Image reconstruction of optical attenuation coefficient variation in biological tissues
2003
A procedure for non-invasive imaging of the optical attenuation coefficient variation of in vivo thick organs/tissues is developed. The laser back-scattered surface profiles at various locations of human forearm, by multi-probe reflectometer, are measured. These profiles are matched by iterative procedure, with that as obtained by Monte Carlo simulation and the corresponding values of attenuation coefficient (equal to the sum of absorption and reduced scattering coefficients) are determined. By interpolation of this data a 100 x 100 grid is constructed and after median filtering of this data a color-coded image of the variability of the optical attenuation coefficient of the forearm is obtained. These images in different subjects show variation due to change in overall tissue composition and blood pooling. This non-invasive imaging procedure may help in identifying the diseased affected regions in healthy tissues and in application of photodynamic therapy.
Applied Optics, 2010
We report on a novel aberration correction technique that uses the sequential combination of two different aberration measurement methods to correct for setup-induced and specimen-induced aberrations. The advantages of both methods are combined and, thus, the measurement time is strongly reduced without loss of accuracy. The technique is implemented using a spatial-light-modulator-based wide-field microscope without the need for additional components (e.g., a Shack-Hartmann sensor). The aberrations are measured without a reference object by directly using the specimen to be imaged. We demonstrate experimental results for technical as well as biological specimens.
Optics Express, 2011
In imaging and focusing applications, spherical aberration induces axial broadening of the point spread function (PSF). A transparent medium between lens and object of interest induces spherical aberration. We propose a method that first obtains both the physical thickness and the refractive index of the aberration inducing medium in situ by measuring the induced focal shifts for paraxial and large angle rays. Then, the fourth order angle dependence of the optical path difference inside the medium is used to correct the spherical aberration using a phase-only spatial light modulator. The obtained measurement accuracy of 3% is sufficient for a complete compensation as demonstrated in a model microscope with NA 0.3 with glass plate induced axial broadening of the PSF by a factor of 5.
Computational adaptive optics for live three-dimensional biological imaging
Proceedings of The National Academy of Sciences - PNAS, 2001
Light microscopy of thick biological samples, such as tissues, is often limited by aberrations caused by refractive index variations within the sample itself. This problem is particularly severe for live imaging, a field of great current excitement due to the development of inherently fluorescent proteins. We describe a method of removing such aberrations computationally by mapping the refractive index of the sample using differential interference contrast microscopy, modeling the aberrations by ray tracing through this index map, and using space-variant deconvolution to remove aberrations. This approach will open possibilities to study weakly labeled molecules in difficult-to-image live specimens. www.pnas.org͞cgi͞doi͞10.1073͞pnas.071275698
Distortion matrix concept for deep optical imaging in scattering media
2020
In optical imaging, light propagation is affected by the inhomogeneities of the medium. Sample-induced aberrations and multiple scattering can strongly degrade the image resolution and contrast. Based on a dynamic correction of the incident and/or reflected wave-fronts, adaptive optics has been employed to compensate for those aberrations. However, it only applies to spatially-invariant aberrations or to thin aberrating layers. Here, we propose a global and non-invasive approach based on the distortion matrix concept. This matrix basically connects any focusing point of the image with the distorted part of its wave-front in reflection. A singular value decomposition of the distortion matrix allows to correct for high-order aberrations and forward multiple scattering over multiple isoplanatic modes. Proof-of-concept experiments are performed through biological tissues including a turbid cornea. We demonstrate a Strehl ratio enhancement up to 2500 and recover a diffraction-limited res...
Confocal imaging through weakly aberrating media
Applied Optics, 2000
The effect on confocal imaging of spherical aberration caused by a weak refractive-index mismatch is discussed. Aberration balancing that uses a change in the objective’s tube length is studied. It is found that the range of depths that can be imaged satisfactorily by a high-numerical-aperture objective with compensation is an order of magnitude greater than that without compensation. The aberration balancing tends to break down for extremely high numerical apertures.
Advances in 3D Optical Imaging Quantification and Sensitivity
2011
Advances in the detection and quantification for 3D optical tomography of bioluminescent and fluorescent reporters to quantify in terms of either cell number or absolute pmol concentration will be discussed. These methods include enhancing the detected signal levels using slight compression which reduces the amount of tissue light propagates through. Calibration techniques to improve signal location by reducing the excitation light artifacts, the amount of detected autofluorescence and techniques to quantify 3D reconstruction results in terms of biological activity will be demonstrated.