Fast and optimal broad-band Stokes/Mueller polarimeter design by the use of a genetic algorithm

A fast multichannel Stokes/Mueller polarimeter with no mechanically moving parts has been designed to have close to optimal performance from 430-2000 nm by applying a genetic algorithm. Stokes (Mueller) polarimeters are characterized by their ability to analyze the full Stokes (Mueller) vector (matrix) of the incident light. This ability is characterized by the condition number, $\kappa$, which directly influences the measurement noise in polarimetric measurements. Due to the spectral dependence of the retardance in birefringent materials, it is not trivial to design a polarimeter using dispersive components. We present here both a method to do this optimization using a genetic algorithm, as well as simulation results. Our results include fast, broad-band polarimeter designs for spectrographic use, based on 2 and 3 Ferroelectric Liquid Crystals, whose material properties are taken from measured values. The results promise to reduce the measurement noise significantly over previous designs, up to a factor of 4.5 for a Mueller polarimeter, in addition to extending the spectral range.Comment: 10 pages, 6 figures, submitted to Optics Expres

Cherenkov luminescence imaging – an aid in intraocular tumour treatment

Masteroppgave i fysikkPHYS399MAMN-PHY

Cherenkov luminescence imaging for assessment of radioactive plaque position in brachytherapy of uveal melanoma: An in vivo feasibility study

Purpose: To study the feasibility of using Cherenkov luminescence imaging (CLI) to evaluate and document ruthenium-106 plaque position during brachytherapy of uveal melanoma. Methods: Ruthenium-106 decays by emitting high-energy beta particles. When the electrons pass through the eye, Cherenkov radiation generates a faint light that can be captured by highly sensitive cameras. Patients undergoing ruthenium-106 plaque brachytherapy for posteriorly located choroidal melanoma were examined by CLI, which was performed in complete darkness with an electron multiplying charged-coupled device camera mounted on a fundus camera modified for long exposures. Results: Ten patients with tumors ranging from 5.8 to 13.0 mm in largest basal diameter and 2.0 to 4.6 mm in height were included. The plaques had an activity between 0.035 and 0.089 MBq/mm2 at the time of examination (1–4 days after implantation). CLI revealed the actual plaque position by displaying a circular area of light in the fundus corresponding with the plaque area. The Cherenkov light surrounded the tumor as a halo, which showed some asymmetry when the plaque was slightly displaced. The light intensity correlated positively with plaque activity and negatively with tumor pigmentation. Exposure times between 30 and 60 seconds were required to display the plaque position and delineate the tumor area. The long exposures made it difficult to maintain stable eye fixation and optimal image quality. Conclusions: CLI is a novel method to assess and document ruthenium-106 plaque position in brachytherapy for uveal melanoma. Translational Relevance: Ocular CLI may provide relevant radiation data during and after implantation of radioactive plaques, thus improving the accuracy of episcleral brachytherapy