Publications & Presentations

Historical Perspective of PDT Light Sources

Y. Zhao, M. Hinds, T. Moritz, J. Gunn, B. W. Pogue, and S. J. Davis
17th International Photodynamic Association World Congress, Cambridge, MA, 3 July 2019
SPIE Paper Number: 11070-174

PDT light sources have advanced from high power discharge lamps to miniature coherent and incoherent fiber-coupled devices.
Progress in these light sources have greatly advanced both our understanding of the PDT mechanisms and kinetics.
Modern light sources are facilitating both laboratory studies and clinical treatments.

High speed VNIR/SWIR HSI sensor for vegetation trait mapping

High speed VNIR/SWIR HSI sensor for vegetation trait mapping
Julia R. Dupuis; S. Chase Buchanan; Stephanie Craig; J. D. Rameau; David Mansur
SPIE Defense and Commercial Sensing 2019, Baltimore, MD, April 14-18, 2019
Algorithms, Technologies, and Applications for Multispectral and Hyperspectral Imagery XXV

A high-speed visible/near infrared, shortwave infrared (VNIR/SWIR) hyperspectral imaging (HSI) sensor for airborne, dynamic, spatially-resolved vegetation trait measurements in support of advanced terrestrial modeling is presented.

The VNIR/SWIR-HSI sensor employs a digital micromirror device as an agile, programmable entrance slit into VNIR (0.5–1μm) and SWIR (1.2–2.4μm) grating spectrometer channels, each with a two-dimensional focal plane array. The sensor architecture, realized in a 13 lb package, is specifically tailored for deployment on a small rotary wing (hovering) unmanned aircraft system (UAS). The architecture breaks the interdependency between aircraft speed, frame rate, and spatial resolution characteristic of push-broom HSI systems. The approach enables imaging while hovering as well as flexible revisit and/or foveation over a region of interest without requiring cooperation by the UAS. Hyperspectral data cubes are acquired on the second timescale which alleviates the position accuracy requirements on the UAS’s GPS-IMU. The sensor employs a simultaneous and boresighted visible context imager for pan sharpening and orthorectification. The data product is a 384×290 (spatial) ×340 (spectral) format calibrated, orthorectified spectral reflectivity data cube with a 26×20° field of view. The development, characterization, and a series of capability demonstrations of an advanced prototype VNIR/SWIR HSI sensor are presented. Capability demonstrations include ground-based testing as well as flight testing from a commercial rotary wing UAS with remote operation of the HSI sensor via a dedicated ground station.

Instrument for measurement of singlet oxygen for studies of skin under UVA irradiation

S. J. Davis, D. I. Rosen, R. K. Sivimani, and W. Burney
SPIE Photonics West 2019, SPIE Paper No. 10851-18, 2-7 February, 2019, San Francisco, CA

In this paper we will describe a non-intrusive, optically-based instrument that can quantitatively measure singlet molecular oxygen, a constituent of reactive oxygen species (ROS) produced by irradiation of human skin by the longer wavelength UV radiation known as UVA. UVA is causally associated with DNA damage and subsequent development of melanoma.

We will present data from healthy human subjects that show formation of singlet molecular oxygen and concomitant production of thymine dimers, indicative of DNA damage. We will also discuss how this instrument may be a valuable tool for the development of more effective sunblock formulations for UVA.

A 2-D imaging dosimeter for photodynamic therapy

Y. Zhao, M. Hinds, J. Gunn, B. W. Pogue, and S. J. Davis
SPIE Photonics West 2019, SPIE Paper No. 10860-23, 2-7 February, 2019, San Francisco, CA

Photodynamic Therapy (PDT) is a promising modality for cancer treatment. Typically, a laser is used to photo-excite a photosensitizer (PS) that subsequently collides with oxygen molecules promoting them to the metastable singlet delta state O2. Singlet oxygen molecules are believed to be the species that destroys cancerous cells during PDT.

In this paper we describe a novel 2D imaging sensor for photosensitizer fluorescence and singlet oxygen luminescence. We describe our instrument and initial results from both in-vitro and in-vivo studies that indicate that this system may be a valuable dosimeter for both PDT researchers and eventually for clinical application.

Applications of the Tunable Diode Laser Absorption Spectroscopy: In-Process Estimation of Primary Drying Heterogeneity and Product Temperature During Lyophilization

Applications of the Tunable Diode Laser Absorption Spectroscopy In-Process Estimation of Primary Drying Heterogeneity and Product Temperature During Lyophilization
Puneet Sharma, William J. Kessler, Robin Bogner, Meena Thakur, and Michael J. Pikal
Journal of Pharmaceutical Sciences 108 (2019) 416-430

The aim of this research was to evaluate the impact of variability in ice sublimation rate (dm/dt) measurement and vial heat transfer coefficient (Kv) on product temperature prediction during the primary drying phase of lyophilization. The mathematical model used for primary drying uses dm/dt and Kv as inputs to predict product temperature.

A second-generation tunable diode laser absorption spectroscopy (TDLAS)ebased sensor was used to measure dm/dt. In addition, a new approach to calculate drying heterogeneity in a batch during primary drying is described. The TDLAS dm/dt measurements were found to be within 5%-10% of gravimetric measurement for laboratory- and pilot-scale lyophilizers. Intersupplier variability in Kv was high for the same “type” of vials, which can lead to erroneous product temperature prediction if “one value” of vial heat transfer coefficient is used for “all vial types” from different suppliers. Studies conducted in both a laboratory- and a pilot-scale lyophilizer showed TDLAS product temperature to be within ±1 C of average thermocouple temperature during primary drying. Using TDLAS data and calculations to estimate drying heterogeneity (number of vials undergoing primary drying), good agreement was obtained between theoretical and experimental results, demonstrating usefulness of the new approach.

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