https://www.nmr.mgh.harvard.edu/optics/PDF/Strangman_BiolPsychiatry_52_679_2002.pdf

Non-invasive neuroimaging using near-infrared light

Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted considerable interest due to their superior physicochemical features, such as large anti-Stokes shifts, low autofluorescence background, low toxicity and high penetration depth, which make them extremely suitable for use as alternatives to conventional downshifting luminescence bioprobes like organic dyes and quantum dots for various biological applications. A fundamental understanding of the photophysics of lanthanide-doped UCNPs is of vital importance for discovering novel optical properties and exploring their new applications. In this review, we focus on the most recent advances in the development of lanthanide-doped UCNPs as potential luminescent nano-bioprobes by means of our customized lanthanide photophysics measurement platforms specially designed for upconversion luminescence, which covers from their fundamental photophysics to bioapplications, including electronic structures (energy levels and local site symmetry of emitters), excited-state dynamics, optical property designing, and their promising applications for in vitro biodetection of tumor markers. Some future prospects and efforts towards this rapidly growing field are also envisioned.

Lanthanide-doped upconversion nano-bioprobes: electronic structures, optical properties, and biodetection

An ultrahigh-speed spectral domain optical coherence tomography (SD-OCT) system is presented that achieves acquisition rates of 29,300 depth profiles/s. The sensitivity of SD-OCT and time domain OCT (TD-OCT) are experimentally compared, demonstrating a 21.7-dB improvement of SD-OCT over TD-OCT. In vivo images of the human retina are presented, demonstrating the ability to acquire high-quality structural images with an axial resolution of 6 microm at ultrahigh speed and with an ocular exposure level of less than 600 microW.

/pdf/in-vivo-human-retinal-imaging-by-ultrahigh-speed-spectral-5g5jdzd3ja.pdf

In vivo human retinal imaging by ultrahigh-speed spectral domain optical coherence tomography

Photoacoustics has been broadly studied in biomedicine, for both human and small animal tissues. Photoacoustics uniquely combines the absorption contrast of light or radio frequency waves with ultrasound resolution. Moreover, it is non-ionizing and non-invasive, and is the fastest growing new biomedical method, with clinical applications on the way. This review provides a brief recap of recent developments in photoacoustics in biomedicine, from basic principles to applications. The emphasized areas include the new imaging modalities, hybrid detection methods, photoacoustic contrast agents and the photoacoustic Doppler effect, as well as translational research topics.

/pdf/photoacoustic-tomography-and-sensing-in-biomedicine-3bw24bh0og.pdf

Photoacoustic tomography and sensing in biomedicine

Retinal vascular diseases are important causes of vision loss. A detailed evaluation of the vascular abnormalities facilitates diagnosis and treatment in these diseases. Optical coherence tomography (OCT) angiography using the highly efficient split-spectrum amplitude decorrelation angiography algorithm offers an alternative to conventional dye-based retinal angiography. OCT angiography has several advantages, including 3D visualization of retinal and choroidal circulations (including the choriocapillaris) and avoidance of dye injection-related complications. Results from six illustrative cases are reported. In diabetic retinopathy, OCT angiography can detect neovascularization and quantify ischemia. In age-related macular degeneration, choroidal neovascularization can be observed without the obscuration of details caused by dye leakage in conventional angiography. Choriocapillaris dysfunction can be detected in the nonneovascular form of the disease, furthering our understanding of pathogenesis. In choroideremia, OCT's ability to show choroidal and retinal vascular dysfunction separately may be valuable in predicting progression and assessing treatment response. OCT angiography shows promise as a noninvasive alternative to dye-based angiography for highly detailed, in vivo, 3D, quantitative evaluation of retinal vascular abnormalities.

/pdf/quantitative-optical-coherence-tomography-angiography-of-4h4s7i0f3u.pdf

Quantitative optical coherence tomography angiography of vascular abnormalities in the living human eye

The current national consensus standard for laser safety in the United States is the American National Standard for Safe Use of Lasers (ANSI Z136.1). Over the past few years, a comprehensive rewrite of this standard has been conducted. The updated version of the standard (Z136.1-2000) incorporates a wealth of new bioeffects data and establishes a number of new maximum permissible exposure (MPE) limits for laser safety. The updated standard also includes new procedures for the computation of MPE values, which must be understood by health physicists, laser safety officers, and others in the field of occupational safety. Here we present the first in a series of tutorial articles to clarify laser safety analysis procedures under this new standard. This article deals with the proper application of three rules for determining the appropriate MPE values for repetitively pulsed lasers or repeated exposures from laser beams.

A procedure for multiple-pulse maximum permissible exposure determination under the Z136.1-2000 American National Standard for Safe Use of Lasers

Over the past few years, a comprehensive rewrite of the American National Standard for Safe Use of Lasers (ANSI Z136.1) has been conducted. The ANSI Z136.1 is a user standard, as opposed to a manufacturer standard like the Federal Laser Product Performance Standard. As such, differing philosophies for hazard classification and application of safety control measures apply, based upon the user’s perspective. Here we present the second in a series of tutorial articles designed to clarify laser hazard analysis procedures under this new ANSI Standard. The procedure presented allows the reader to effectively determine the appropriate hazard classification for a small-source laser by using known laser output parameters in a step-by-step analysis.

A procedure for laser hazard classification under the Z136.1-2000 American National Standard for Safe Use of Lasers

The current national consensus standard for laser safety in the United States is the American National Standard for Safe Use of Lasers (ANSI Z1361) The most recent standard, Z1361-2000, incorporates a wealth of recent bioeffects data and established a number of new maximum permissible exposure (MPE) limits for laser safety The standard also includes recent procedures for the computation of MPE values from large or extended diffusely scattering sources, which must be understood by health physicists, laser safety officers, and others in the field of occupational safety Here we present the fourth in a series of tutorial articles, written to clarify laser safety analysis procedures under this standard, with an emphasis on the MPE computation methods related to extended sources, and the determination of nominal hazard zones

Procedure for the computation of hazards from diffusely scattering surfaces under the Z136.1-2000 American National Standard for Safe Use of Lasers

Hazard evaluation methods for lasers, with wavelengths greater than 1.4 microns (mostly in the middle infrared), have changed significantly in the current version of the American National Standard for the Safe Use of Lasers, ANSI Z136.1-1993. A correct evaluation involves comparing the hazard potential based on two evaluation models; one based on individual pulses and the other based on an equivalent continuous-wave exposure. An example of the hazard evaluation method within this spectral region is provided.

Laser hazard evaluation method for middle infrared laser systems.

Over the past few years, a comprehensive rewrite of the American National Standard for Safe Use of Lasers (ANSI Z136.1) has been conducted [American National Standards Institute, Z136.1-2000 American National Standard for Safe Use of Lasers (American National Standards Institute, New York, 2000)]. Important parts of many laser safety evaluations are the determination of the maximum distance at which the laser presents a hazard and the computation of optical density requirements for eye protection. In the ANSI Z136.1-2000 Standard, two approaches for the computation of hazard distance are presented. We specifically address the derivation of these two methodologies including the effects of atmospheric attenuation and optically aided viewing. In addition, these methodologies may be applied to the computation of visual interference distance as described in the ANSI Z136.6-2000 Standard [American National Standards Institute, Z136.6-2000 American National Standard for Use of Lasers Outdoors (American National Standards Institute, New York, 2000)]. This publication represents the third in a series of tutorial articles designed to clarify laser hazard analysis procedures under these ANSI Standards [R. J. Thomas, B. A. Rockwell, W. J. Marshall, R. C. Aldrich, S. A. Zimmerman, and R. J. Rockwell, Jr., J. Laser Appl. 13, 134–140 (2001); 14, 57–66 (2002)].

Robert C. Aldrich

Papers

A procedure for multiple-pulse maximum permissible exposure determination under the Z136.1-2000 American National Standard for Safe Use of Lasers

A procedure for laser hazard classification under the Z136.1-2000 American National Standard for Safe Use of Lasers

Procedure for the computation of hazards from diffusely scattering surfaces under the Z136.1-2000 American National Standard for Safe Use of Lasers

Laser hazard evaluation method for middle infrared laser systems.

A procedure for the estimation of intrabeam hazard distances and optical density requirements under the ANSI Z136.1-2000 Standard