Light dosimetry technique for endoscopic PDT using microlens optical fiber

Steven L. Jacques

Research output: Contribution to journalConference articlepeer-review

1 Scopus citations


A simple procedure is presented for determining the irradiance of light striking tissues during light delivery using a microlens optical fiber via an endoscope. The particular example is photodynamic therapy (PDT) of laryngeal cancer. A microlens optical fiber is an optical fiber with a small lens assembly at its terminus which magnifies the image of the end of the fiber yielding a uniform irradiance in a plane distant from the fiber. Prior to the therapy, the relation between fiber-target distance, h [cm], and the diameter of the uniform beam, d(h) [cm], was established and the area of the beam was calculated: A(h) = πd(h)2/4. The laser power P [W] required to achieve a desired irradiance E [W/cm2] was P(h) = EA(h), and this relation was prepared as a simple graph for routine use in the clinic. During the therapy, the doctor advances the optical fiber through the working channel of the endoscope to touch the target tissue site while observing through the optical channel, and marks the fiber on the outside of the endoscope. The doctor then retracts the fiber until an aiming beam transmitted through the fiber fully illuminates the desired target area, and again marks the fiber on the outside of the endoscope. The difference in the two marks on the fiber outside the endoscope yields h, the height of the fiber above the target tissue. The laser operator then uses the P(h) = EA(h) graph to select the proper laser power to achieve the desired E. Although trivially simple, this dosimetry procedure was critical to the proper implementation of PDT for laryngeal cancer.

Original languageEnglish (US)
Pages (from-to)455-462
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - Jan 1 1999
EventProceedings of the 1999 Laser-Tissue Interaction X: Photochemical, Photothermal, and Photomechanical - San Jose, CA, USA
Duration: Jan 24 1999Jan 27 1999

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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