Evaluation of at-home methods for N95 filtering facepiece respirator decontamination.

N95 filtering facepiece respirators (FFRs) are essential for the protection of healthcare professionals and other high-risk groups against Coronavirus Disease of 2019 (COVID-19). In response to shortages in FFRs during the ongoing COVID-19 pandemic, the Food and Drug Administration issued an Emergency Use Authorization permitting FFR decontamination and reuse. However, although industrial decontamination services are available at some large institutions, FFR decontamination is not widely accessible. To be effective, FFR decontamination must (1) inactivate the virus; (2) preserve FFR integrity, specifically fit and filtering capability; and (3) be non-toxic and safe. Here we identify and test at-home heat-based methods for FFR decontamination that meet these requirements using common household appliances. Our results identify potential protocols for simple and accessible FFR decontamination, while also highlighting unsuitable methods that may jeopardize FFR integrity.

Simple wavefront correction framework for two-photon microscopy of in-vivo brain.

We present an easily implemented wavefront correction scheme that has been specifically designed for in-vivo brain imaging. The system can be implemented with a single liquid crystal spatial light modulator (LCSLM), which makes it compatible with existing patterned illumination setups, and provides measurable signal improvements even after a few seconds of optimization. The optimization scheme is signal-based and does not require exogenous guide-stars, repeated image acquisition or beam constraint. The unconstrained beam approach allows the use of Zernike functions for aberration correction and Hadamard functions for scattering correction. Low order corrections performed in mouse brain were found to be valid up to hundreds of microns away from the correction location.

Time resolved optical tomography of the human forearm.

A 32-channel time-resolved optical imaging instrument has been developed principally to study functional parameters of the new-born infant brain. As a prelude to studies on infants, the device and image reconstruction methodology have been evaluated on the adult human forearm. Cross-sectional images were generated using time-resolved measurements of transmitted light at two wavelengths. All data were acquired using a fully automated computer-controlled protocol. Images representing the internal scattering and absorbing properties of the arm are presented, as well as images that reveal physiological changes during a simple finger flexion exercise. The results presented in this paper represent the first simultaneous tomographic reconstruction of the internal scattering and absorbing properties of a clinical subject using purely temporal data, with additional co-registered difference images showing repeatable absorption changes at two wavelengths in response to exercise.

Three-dimensional time-resolved optical tomography of a conical breast phantom.

A 32-channel time-resolved imaging device for medical optical tomography has been employed to evaluate a scheme for imaging the human female breast. The fully automated instrument and the reconstruction procedure have been tested on a conical phantom with tissue-equivalent optical properties. The imaging protocol has been designed to obviate compression of the breast and the need for coupling fluids. Images are generated from experimental data with an iterative reconstruction algorithm that employs a three-dimensional (3D) finite-element diffusion-based forward model. Embedded regions with twice the background optical properties are revealed in separate 3D absorption and scattering images of the phantom. The implications for 3D time-resolved optical tomography of the breast are discussed.

Multiple-slice imaging of a tissue-equivalent phantom by use of time-resolved optical tomography.

Following several years of development the construction of a multichannel time-resolved imaging device for medical optical tomography has been completed. Images are reconstructed from time-resolved measurements by use of a scheme that employs a finite-element diffusion-based forward model and an iterative reconstruction solver. Prior to testing on clinical subjects the fully automated instrument and the reconstruction software are evaluated with tissue-equivalent phantoms. We describe our first attempt to generate multiple-slice images of a phantom without uniform properties along the axial direction, while still using a computationally fast two-dimensional reconstruction algorithm. The image quality is improved by the employment of an approximate correction method that uses scaling factors derived from the ratios of finite-element forward simulations in two and three spatial dimensions. The 32-channel system was employed to generate maps of the internal scattering and the absorption properties at 14 different transverse planes across the phantom. The images clearly reveal the locations of small inhomogeneous regions embedded within the phantom. These results were obtained by use of purely temporal data and without resource to reference measurements.

Simultaneous reconstruction of absorption and scattering images by multichannel measurement of purely temporal data.

We present what is believed to be the first simultaneous reconstruction of the internal scattering and absorbing properties of a highly scattering medium by use of purely temporal data. These results are also the first acquired with the multichannel time-resolved imaging system developed at University College London.