Biomedical Applications of AgClBr Optical Fibers: Laser Bonding of Tissues. Early Detection of Skin Cancer

Svetlana Basov, Department of Biomedical Engineering.

Work done under the supervision of Prof. Amit Gefen and Prof. Abraham Katzir

Abstract.

Standard optical fibers are completely opaque in the mid-IR in the spectral range 3-30µm. In our group we developed special crystalline fibers, made of silver halide (AgClBr), which are flexible, non-toxic, bio-compatible and highly transparent in the mid-IR.

In this work I participated in the fabrication of these fibers and used them for two completely different applications.

Laser Bonding of Incisions: A system based on silica fibers, AgClBr fibers, an IR laser and a control system, made it possible to heat a spot on tissue under close temperature control. It was found that this may be used for laser soldering of incisions. In this case the approximated edges of an incision are covered by Albumin and they are heated, spot by spot, so that each spot is heated for 60C for 10sec. The bonding is strong and there is almost no scarring.

We successfully laser soldered incisions in the corneas of pigs, in vitro, and then measured the burst pressure P_B needed to break open the bonded incisions. This pressure was quite high. We then carried out experiments on the corneas of mid-size live pigs, that we euthanized after few weeks. These soldered corneas showed strong bonding, with no thermal damage. This proved that laser soldering would be a very promising method for corneal transplantation. This method could be used by less experienced surgeons, reducing the load of the highly skilled ones.

In addition, we integrated our laser soldering system with a robotic system at the lab. of Prof. Nisky at Ben Gurion University. We there carried out robotic laser soldering, where robotic arms moved the distal ends of the fibers for heating spots on the approximated edges of an incisions in skin. The procedure was carried out automatically! This would probably the way laser soldering will be carried out in the future, again, making it possible for less experienced surgeons to obtain excellent retults.

Early Detection of Skin Cancer: Melanoma is a very dangerous skin cancer. If its thickness is d <1mm, when detected, and it is removed – almost all patients survive. If d>1mm, almost all patients die. A dermatologist looking at lesions on the skin must distinguish immediately if a lesion is suspicious and send it to pathology to determine if it is indeed melanoma. This requires many years of experience, and a less experienced dermatologist may miss the suspicious lesions which may lead to serious effect. It seems that there is no approved method for the automatic detection of melanoma.

We developed a system that incorporated AgClBr fibers and made it possible to carry out spectroscopic measurements in the mid-IR on lesions on the skins of patients. Clinical measurements were carried out at the Dermatology Department at the Ichilov Hospital. Expert dermatologists detected suspicious lesions and we carried out measurement on each lesion and on neighboring skin. Measurements were done on 90 patients and only 5 lesions were found to be melanoma (by histopathology). We made a great effort to to analyze the results and to see differences in the mid-IR spectra of the melanoma lesions and the benign lesions. Only lately we found a mathematical algorithm that seems to do the job. However, our statistics is insufficient. We plan to carry out many more measurements in the department of Prof. Scope at the Sheba Hospital. If our algorithm indeed works, it will open the way for an automatic early detection of melanoma, without relying on the skill of the examining dermatologist.

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SCHOOL OF MECHANICAL ENGINEERING SEMINAR
Wednesday, March 18, 2020 at 14:00 
Wolfson Building of Mechanical Engineering, Room 206

Beneficial Utilization of Strong Nonlinearity in Dynamics and Acoustics

Alexander F. Vakakis
University of Illinois at Urbana - Champaign, USA
avakakis@illinois.edu

In this lecture we discuss certain examples of beneficial utilization of intentional strong nonlinearity in dynamical and acoustical systems across different scales. Central to this concept is the inducement of irreversible nonlinear energy transfers from large-to-small scales that induce effects such as passive break reciprocity in controlled and predictable ways or broadband / narrowband energy redirection in preferential paths/modes in structures and metamaterials. These non-reciprocal energy transfers mimic analogous energy cascades that occur often in Nature (e.g., in turbulent flows or granular media), and, as such, benefit from the well-known robust and enhanced dissipative features exhibited by these natural phenomena. Our approach dictates advanced theoretical modeling and analysis, but also nonlinear system identification and reduced-order modeling to characterize the experimental realizations that validate the theoretical predictions. In the presented applications, we’ll discuss new approaches for designing, analyzing, characterizing and experimentally testing passive blast mitigation systems, non-reciprocal lattice metamaterials, and fluid control in flow-structure interaction problems. The aim is to translate these methods to new technologies and devices that exploit and showcase intentional strong nonlinearity.
This work is funded in part by National Science Foundation Emerging Frontiers Research Initiative Grant 1741565. Any opinion, findings, conclusions or recommendations expressed are those of the presenter and do not necessarily reflect the views of the National Science Foundation.
Short Bio: Alexander F. Vakakis received his Ph.D. from Caltech (1990), M.Sc. from Imperial College, London (1985), and Diploma in Mechanical Engineering from the University of Patras, Greece (1984). He is the Donald Biggar Willett Professor of the College of Engineering of the University of Illinois where he co-directs the Linear and Nonlinear Dynamics and Vibrations Laboratory (http://lndvl.mechse.illinois.edu/), and currently the Edmond J. Safra Visiting Professor at Technion. Among other awards, he is the recipient of an Alexander von Humboldt Research Award (2019), the ASME Thomas K. Caughey Award in nonlinear dynamics (2014), and since 2015 acts as a National High-End Foreign Expert in China. He has published over 300 archival publications, holds two patents, and has authored or edited 6 technical texts and monographs. His research interests center on nonlinear dynamics, vibrations and acoustics.