The amount of radiation a tumor absorbs during therapy sessions is currently estimated rather than measured. Estimates are often wrong, resulting in excessive or insufficient amount of radiotherapy that can let a tumor propagate or result in unwelcome side effects from the therapy itself.
At the FEMTO-ST Institute, a facility associated with French National Center for Scientific Research (CNRS), researchers have developed a radiation sensor that is little more than a modified fiber optic cable, thin enough for minimally invasive applications.
It is made by modifying an optical fiber to introduce a scintillating material near the tip. Scintillators release photons when they’re showered with ionizing radiation. As the scintillator is irradiated and begins to glow, the photons travel down the optical fiber where a photodetector measures the amount of light they produce. Since the amount of photons released is proportional to the radiation absorbed, the reading from the photodetector is indicative of the delivered radioactivity.
The only problem is that a scintillator releases photons in all directions and a scintillator inside a optic fiber is so small that not many photons are released, making detection difficult. To direct most of the photons down the optic fiber and toward the photodetector, the researchers relied on so-called “optical antennas”. These devices are also tiny and can be used to focus the photons in one direction. Such an antenna, only a few microns in diameter, was placed between the scintillator and the optical fiber, directing enough photons so that the photodetector can actually measure them.
Study in journal Optics Letters: Ultracompact x-ray dosimeter based on scintillators coupled to a nano-optical antenna…
Via: The Optical Society…
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