08/13/2021
By Tyler Iorizzo

The Kennedy College of Sciences, Department of Physics & Applied Physics, invites you to attend a master's thesis defense by Tyler Iorizzo on "Spectroscopic Techniques for Phototherapeutic Applications."

Candidate Name: Tyler Iorizzo
Degree: Master's
Defense Date: Tuesday, Aug. 24, 2021
Time: 11 a.m.
Location: Zoom. Anyone interested in attending should email tyler_iorizzo@student.uml.edu for the Zoom link.

Thesis Title: Spectroscopic Techniques for Phototherapeutic Applications

Advisor: Anna Yaroslavsky, Ph.D., Associate Professor, Department of Physics & Applied Physics, University of Massachusetts Lowell

Committee Members: 

  • Erno Sajo, Ph.D., Professor, Director – Medical Physics, Department of Physics & Applied Physics, University of Massachusetts Lowell
  • Javed Mannan, MD, MPH, Assistant Professor, Department Pediatrics, UMass Memorial Medical Center , University of Massachusetts Medical School

Abstract:

The goal of this thesis was to determine the optical properties of materials to improve dosimetry and safety of clinical phototherapy procedures. Chapter 2 describes the methodology utilized in chapters 3 and 4. Integrating sphere spectrophotometry was used to measure transmittance and reflectance of the samples in the visible and infrared spectral range. An inverse hybrid Monte Carlo method was employed to calculate the spectral dependence of absorption coefficients, scattering coefficients, and anisotropy factors of the target tissues. Chapter 3 presents the first study that comprehensively quantified temperature induced changes of the in vivo tissue optical properties. The absorption, scattering and anisotropy of the in vivo skin were evaluated and analyzed in the spectral range from 400 to 1650 nm as tissue temperature increased from 25°C to 60°C. Skin temperature was controlled using an automated heater equipped with a feed-back sensor. Reflectance confocal microscopy was used for monitoring tissue changes. The results demonstrated that overall absorption and scattering coefficients increased while anisotropy factors decreased as the temperature of skin increased. Absorption spectra revealed deoxygenation of hemoglobin and a blue shift in water absorption bands as skin temperature reached 60°C. Confocal microscopy presented morphological tissue transformations that were in concordance with spectroscopic findings. The results of the study indicate that monitoring spectral responses of tissue during phototherapeutic procedures may enable accurate light dosimetry. In Chapter 4, the methods for selecting and testing the materials for a blue light phototherapy shield were proposed and implemented. Four biocompatible fabrics and two reflective materials were investigated. Optical properties of the four fabrics and transmittance of the two foils were determined in the 400-500 nm range. The highest attenuating materials were selected, a two-layer prototype was assembled and tested under clinical exposure conditions. The proposed methodology to test and optimize the optical and thermal responses of shield materials can be implemented for a wide range of clinical procedures.