Ultraviolet Photoacoustic Remote Sensing Microscopy

• Author / Creator

  Haven, Nathaniel

• Cancer is currently one of the leading causes of death globally. In dealing with certain cancers, the recommended treatment is often surgery. In order to determine if the entirety of the cancerous mass has been removed, tumor resection margins are assessed after surgical resection, as it is difficult to differentiate cancerous from health tissue without micro-scale observation. Presently, the current gold-standard for tissue biopsy and tumor resection margin analysis is formalin-fixed paraffin-embedded hematoxylin & eosin (H&E) histology. Though, this process is both time consuming and labor intensive as well as being a significant burden on the healthcare economy. Unfortunately, there are currently no intraoperative techniques capable of reproducing reliable post-operative H&E histology output, this results in many patients having to undergo secondary surgeries, leading to unnecessary emotional and physical trauma for patients, as well as higher risks of worsened prognosis. Here we report the development of an ultraviolet excitation photoacoustic remote sensing microscopy system capable of producing images of cell nuclei within cell cultures and tissue samples. This was achieved in two iterations. The first iteration utilized a parabolic focusing element along with mechanical stage scanning to obtain images of sectioned HT1080 CAM tumors, as well as HeLa cell cultures, demonstrating the ability to observe individual cell nuclei with good comparison to H&E histology. However, the resolution of this system, determined to be 0.70-µm, could be improved and mechanical stage scanning resulted in slow acquisition speeds. In order to improve on these shortcomings, the second iteration moved towards a reflective objective focusing element, along with galvanometer optical scanning, able to clearly image cell nuclei in a variety of tissue samples with a determined resolution of 0.39-µm. The by-product of using a higher numerical aperture objective resulted in a tighter depth-of-focus, permitting the demonstration of superficial optical sectioning within tissue samples, where individual cell layers could be observed whilst rejecting background signal from cell layers outside the focal plane. In order to move closer towards an intraoperative translation goal, preliminary work was conducted in the direction of faster wide-field imaging with this system. This work showcased the widefield scanning abilities of focusing prior to optical scanning, as well as miniaturization capabilities using MEMS based optical scanners. Overall, the system presented has real potential to develop into a solution to the tumor resection margin analysis problem.

• Subjects / Keywords

  • Microscopy
  • Histopathology
  • Photoacoustic Imaging
  • Ultraviolet

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-b6v5-fq68

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.