A Polymer-Gel Eye-Phantom for 3D Fluorescent Imaging of Millimetre Radiation Beams

Abstract

We have filled a 24 mm diameter glass sphere with a transparent polymer-gel that is radio-fluorogenic, i.e. it becomes (permanently) fluorescent when irradiated, with an intensity proportional to the local dose deposited. The gel consists of >99.9% tertiary-butyl acrylate (TBA) pre-polymerized to ~15% conversion, and ~100 ppm maleimido-pyrene (MPy). Its dimensions and physical properties are close to those of the vitreous body of the human eye. We have irradiated the gel with a 3 mm diameter, 200 kVp X-ray beam with a dose rate of ~1 Gy/min. A 3D (video) view of the beam within the gel has been constructed from tomographic images obtained by scanning the sample through a thin sheet of UV light. To minimize optical artifacts, the cell was immersed in a square tank containing a refractive-index-matching medium. The 20%-80% penumbra of the beam was determined to be ~0.4 mm. The research was a preparatory investigation of the possibility of using the method to monitor the millimetre diameter proton pencil beams used in ocular radiotherapy.

Low-cost fabrication of PPIX liquid phantoms for use in fluorescence measurements

“…The manufactured phantoms can be different in structure, depending on the specific research tasks, where for fluorescence imaging systems solid elastic samples with stable mechanical and temperature properties are most preferable, as for example presented in our previous work 7 . However, to reproduce fluorescent properties, the simplest variant is liquid optical phantoms consisting, for example, of aqueous colloidal solutions, with the addition of absorbing dyes, as well as substances having pronounced intrinsic fluorescence when excited in the desired wavelength range 8,9 . Such phantoms allow the use of buffer solutions with the required pH value as a matrix material to provide an environment compatible with the natural structure of organic molecules that simulate certain properties of a biotissue 10 .…”