Complementary use of polarization-sensitive and standard OCT metrics for enhanced intraoperative differentiation of breast cancer.

We report the development and implementation of an intraoperative polarization-sensitive optical coherence tomography (PS-OCT) system for enhancing breast cancer detection. A total of 3440 PS-OCT images were intraoperatively acquired from 9 human breast specimens diagnosed by H&E histology as healthy fibro-adipose tissue (n = 2), healthy stroma (n = 2), or invasive ductal carcinoma (IDC, n = 5). A standard OCT-based metric (coefficient of variation (CV)) and PS-OCT-based metrics sensitive to biological tissue from birefringence (i.

Local wavefront mapping in tissue using computational adaptive optics OCT.

The identification and correction of wavefront aberrations is often necessary to achieve high-resolution optical images of biological tissues, as imperfections in the optical system and the tissue itself distort the imaging beam. Measuring the localized wavefront aberration provides information on where the beam is distorted and how severely. We have recently developed a method to estimate the single-pass wavefront aberrations from complex optical coherence tomography (OCT) data.

Combined hardware and computational optical wavefront correction.

In many optical imaging applications, it is necessary to overcome aberrations to obtain high-resolution images. Aberration correction can be performed by either physically modifying the optical wavefront using hardware components, or by modifying the wavefront during image reconstruction using computational imaging. Here we address a longstanding issue in computational imaging: photons that are not collected cannot be corrected.

Wavefront measurement using computational adaptive optics.

In many optical imaging applications, it is necessary to correct for aberrations to obtain high quality images. Optical coherence tomography (OCT) provides access to the amplitude and phase of the backscattered optical field for three-dimensional (3D) imaging samples. Computational adaptive optics (CAO) modifies the phase of the OCT data in the spatial frequency domain to correct optical aberrations without using a deformable mirror, as is commonly done in hardware-based adaptive optics (AO).

Computational optical coherence tomography [Invited].

Optical coherence tomography (OCT) has become an important imaging modality with numerous biomedical applications. Challenges in high-speed, high-resolution, volumetric OCT imaging include managing dispersion, the trade-off between transverse resolution and depth-of-field, and correcting optical aberrations that are present in both the system and sample. Physics-based computational imaging techniques have proven to provide solutions to these limitations.

Computed Optical Interferometric Imaging: Methods, Achievements, and Challenges.

Three-dimensional high-resolution optical imaging systems are generally restricted by the trade-off between resolution and depth-of-field as well as imperfections in the imaging system or sample. Computed optical interferometric imaging is able to overcome these longstanding limitations using methods such as interferometric synthetic aperture microscopy (ISAM) and computational adaptive optics (CAO) which manipulate the complex interferometric data. These techniques correct for limited depth-of-field and optical aberrations without the need for additional hardware.

Automated computational aberration correction method for broadband interferometric imaging techniques.

Numerical correction of optical aberrations provides an inexpensive and simpler alternative to the traditionally used hardware-based adaptive optics techniques. In this Letter, we present an automated computational aberration correction method for broadband interferometric imaging techniques. In the proposed method, the process of aberration correction is modeled as a filtering operation on the aberrant image using a phase filter in the Fourier domain.

Intraoperative optical coherence tomography for assessing human lymph nodes for metastatic cancer.

Background: Evaluation of lymph node (LN) status is an important factor for detecting metastasis and thereby staging breast cancer. Currently utilized clinical techniques involve the surgical disruption and resection of lymphatic structure, whether nodes or axillary contents, for histological examination. While reasonably effective at detection of macrometastasis, the majority of the resected lymph nodes are histologically negative.

Computational high-resolution optical imaging of the living human retina.

High-resolution imaging is of great importance for the fields of biology and medicine. The introduction of hardware-based adaptive optics (HAO) has pushed the limits of optical imaging, enabling high-resolution near diffraction-limited imaging of previously unresolvable structures. In ophthalmology, when combined with optical coherence tomography, HAO has enabled a detailed three-dimensional visualization of photoreceptor distributions and individual nerve fibre bundles in the living human retina.

Correction of aberrations in the human eye using computational methods.

Phase-sensitive imaging and computational correction of patient-specific optical aberrations enable high-resolution imaging of the human retina to aid diagnosis and treatment of eye diseases.

Polarization-sensitive interferometric synthetic aperture microscopy.

Three-dimensional optical microscopy suffers from the well-known compromise between transverse resolution and depth-of-field. This is true for both structural imaging methods and their functional extensions. Interferometric synthetic aperture microscopy (ISAM) is a solution to the 3D coherent microscopy inverse problem that provides depth-independent transverse resolution.

Real-time Imaging of the Resection Bed Using a Handheld Probe to Reduce Incidence of Microscopic Positive Margins in Cancer Surgery.

Wide local excision (WLE) is a common surgical intervention for solid tumors such as those in melanoma, breast, pancreatic, and gastrointestinal cancer. However, adequate margin assessment during WLE remains a significant challenge, resulting in surgical reinterventions to achieve adequate local control. Currently, no label-free imaging method is available for surgeons to examine the resection bed in vivo for microscopic residual cancer.

Three-dimensional motion correction using speckle and phase for in vivo computed optical interferometric tomography.

Over the years, many computed optical interferometric techniques have been developed to perform high-resolution volumetric tomography. By utilizing the phase and amplitude information provided with interferometric detection, post-acquisition corrections for defocus and optical aberrations can be performed. The introduction of the phase, though, can dramatically increase the sensitivity to motion (most prominently along the optical axis).

Differentiation of ex vivo human breast tissue using polarization-sensitive optical coherence tomography.

Successful treatment of breast cancer typically requires surgical removal of the tumor. Optical coherence tomography (OCT) has been previously developed for real-time imaging of the surgical margin. However, it can be difficult to distinguish between normal stromal tissue and cancer tissue based on scattering intensity and structure alone.

Stability in computed optical interferometric tomography (Part II): in vivo stability assessment.

Stability is of utmost importance to a wide range of phase-sensitive processing techniques. In Doppler optical coherence tomography and optical coherence elastography, in addition to defocus and aberration correction techniques such as interferometric synthetic aperture microscopy and computational/digital adaptive optics, a precise understanding of the system and sample stability helps to guide the system design and choice of imaging parameters. This article focuses on methods to accurately and quantitatively measure the stability of an imaging configuration in vivo.

Stability in computed optical interferometric tomography (part I): stability requirements.

As imaging systems become more advanced and acquire data at faster rates, increasingly dynamic samples can be imaged without concern of motion artifacts. For optical interferometric techniques such as optical coherence tomography, it often follows that initially, only amplitude-based data are utilized due to unstable or unreliable phase measurements. As systems progress, stable phase maps can also be acquired, enabling more advanced, phase-dependent post-processing techniques.

The effect of age of acquisition on older individuals with and without cognitive impairments.

The present study compared the effects of age of acquisition (AoA) on object naming across groups of older individuals with cognitive impairments, healthy older controls, and young healthy controls. All participants named a set of 80 pictures, within which both AoA and frequency were manipulated orthogonally. Early-acquired objects were named faster than late-acquired objects across all groups.

Vascular smooth muscle responsiveness in a hibernator: effects of season and temperature.

To determine the effects of season, acclimation state, and hibernation on the reactivity of vascular smooth muscle from a hibernant species, strips of thoracic aorta, renal and femoral arteries, and portal vein obtained from adult woodchucks, Marmota monax, were suspended for isometric tension measurements in physiological salt solution. These blood vessels exhibited no seasonal variation in resting tension, connective tissue content, or maximum tension developed to norepinephrine. However, the concentration-response curves to norepinephrine in both aortic and portal vein strips from animals tested in May and June were shifted to the left of those from animals tested in either August or November through February.

Circannual renal function and plasma electrolytes of the marmot.

Studies with unanesthetized active (non-lethargic) marmots demonstrated circannual rhythms of renal function (clearances of p-aminohippurate, creatinine, and inulin), plasma osmolality, and plasma sodium and potassium concentrations. Effective renal plasma flow, glomerular filtration rate, the clearance of creatinine, and plasma potassium were highest in spring and lowest in the fall and winter. Plasma osmolality and plasma sodium concentrations tended to be highest during the winter months and lowest in the spring and summer.

Maintenance of ion concentration gradients in the cold in aorta from rat and ground squirrel.

Cell water and ionic content were measured in aortic smooth muscle from rats and ground squirrels during 48 h of incubation in oxygenated Krebs solution held at low temperatures. Cells from the ground squirrel, a hibernator, maintained sodium and potassium contents near normal levels during incubation at 7 degrees C. In sharp contrast, cells from the rat lost potassium and gained sodium with half times of 14 and 11 h, respectively.

Spinal cord, hypothalamic, and air temperature: interaction with arousal states in the marmot.

Yellow-bellied marmots, Marmota flaviventris, prepared with U-shaped thermodes in the epidural space of the thoracic vertebral canal, a thermode in the preoptic hypothalamus, and cortical surface and hippocampal electrodes, were used to investigate the interaction of arousal states with temperature regulation. It was found that arousal state of the animal influences the thermoregulatory responses initiated in either the spinal cord or hypothalamus. Further, changes in ambient temperature affected both the gain and the threshold of these responses.