School of Mechanical Engineering Seminar
Wednesday, June 6, 2018 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Finite Element Modeling Guided Laser Therapy ­ Improves Control of Locally Advanced Tumors

Prof. Gal Shafirstein

Professor of Oncology and full Member

Director of Photodynamic Therapy (PDT) Clinical Research

PDT Center at the Department of Cell Stress Biology

Roswell Park Comprehensive Cancer Center, Buffalo, NY, USA

Patients with locally advanced cancerous tumors who failed to respond to standard treatment have very limited treatment options. Several studies suggest that interstitial photodynamic therapy (I-PDT) is a promising treatment modality to control locally advanced cancer. The administration of laser light in I-PDT requires careful treatment planning to maximize tumor ablation while minimizing damage to normal tissue. To that end, we developed a customized finite element modeling (FEM) approach to guide laser light administration in I-PDT.

In this talk, a brief overview of I-PDT will be given. The rationale for the use of FEM will be presented and discussed. This talk will review the modeling approach, validation and translation from the clinic to the laboratory and back to the clinic. Examples of the FEM use to evaluate the feasibility of treating locally advanced head and neck and non-small cell lung cancer will be shown. Pretreatment planning of bone tumors in preclinical settings will be presented. The FEM successful implementation to improve local control and cure of locally advanced squamous cell carcinoma in animal models will be discussed. A clinical study using the FEM to guide I-PDT in the treatment of patients with locally advanced head neck cancer will be presented.

About the Lecturer

Prof. Shafirstein earned his B.Sc. in the department of materials science at the Ben-Gurion University (1986), his M.Sc. (1988) and D.Sc. (1992) in the department of materials science and engineering at the Technion. He then moved to England to work at the United Kingdom National Physical Laboratory (1992-1995), and to Israel and USA to work in industry (1995-2001). He returned to academia in 2001, and joined the department of otolaryngology-head and neck surgery at the University of AR for Medical Sciences, where he was an associated Prof. and the director of translational research. In 2012, he was recruited as a full Prof. of Oncology and member at the photodynamic therapy (PDT) center of Roswell Park Comprehensive Cancer Center, Buffalo, NY. The PDT center at Roswell Park is a world leader in the field of PDT. It is where the modern PDT was initiated in 1970s', and the first FDA approved PDT drug for cancer therapy was developed. Prof. Shafirstein serves as the director of PDT clinical research since 2015. He is responsible for developing and supporting multiple clinical studies in PDT. His research is supported, primarily, with competitive awards from the National Cancer Institute at the National Institute of Health, USA. His research focuses on developing laser therapies for patients with cancer that have no good treatment options.

School of Mechanical Engineering Seminar
Wednesday, October 17, 2018 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Models and Simulations of the Surfactant-Driven

Fracture of Particle Rafts

John E. Dolbow

Professor of Civil and Environmental Engineering,

Mechanical Engineering and Materials Science,

and Mathematics

Duke University

When a densely packed monolayer of hydrophobic particles is placed on a uid surface

the particles interact through capillary bridges, leading to the formation of a particle raft or

\praft" for short. Densely packed monolayers exhibit a two-dimensional elastic response, and

they are capable of supporting both tension and compression. The introduction of a controlled

amount of surfactant generates a surface tension gradient, producing Marangoni forces and

causing the surfactant to spread, fracturing the monolayer. These systems are of interest to

materials scientists and engineers because they provide an idealized setting for investigating the

interplay between uid ow and fracture. Previous studies of the surfactant-induced fracture

of prafts have examined the role of viscosity and the initial packing fraction on the temporal

and spatial evolution of the fractures. The potentially important role of di_erences in surface

tension between the surfactant and the underlying uid has not been explored.

This seminar will describe a new continuum-based model and simulations that account for

the interplay between the pressure exerted by a spreading surfactant and the elastic response

of the praft, including the fracture resistance. This is e_ected through the use of a surfactant

damage _eld that serves as both an indicator function for the surfactant concentration, as well

as the damage to the monolayer. Stochastic aspects of the particle packing are incorporated into

the model through a continuum mapping approach. The model gives rise to a coupled system

of nonlinear partial di_erential equations, with an irreversibility constraint. We recast the

model in variational form and discretize the system with an adaptive _nite element method. A

comparison between model-based simulations and existing experimental observations indicates

a qualitative match in both the fracture patterns and temporal scaling of the fracture process.

Based on the model, we determine a dimensionless parameter that characterizes the ratio

between this driving force and the fracture resistance of the praft. Interestingly, while our

results indicate that the stochastic aspects of the packing are important to the fracture process,

we _nd that regimes of fracture are largely governed by di_erences in surface tension. Finally,

we support our _ndings with newly designed experiments that validate the model and con_rm

the trends inferred from the simulations.