Researchers in the US [including Dartmouth engineering professor Brian Pogue] have unveiled a fast and flexible way to profile the imparted dose from an X-ray photon linac beam in two dimensions in a proof-of-concept study published in Physics in Medicine and Biology. With further refinement to permit three-dimensional dosimetry, the technique could rival today's ionization chamber measurements performed during linac installation and routine quality assurance (Phys. Med. Biol. 58 601).

The simple method exploits the Cerenkov effect, and uses just a water tank, a standard commercial CMOS camera and a fluorescent dye dissolved in tap water. As the X-ray beam is incident on the water, Cerenkov light is generated, which excites the dissolved fluorophore. The fluorophore emits a characteristic fluorescent signal that is acquired by the camera. These optical images of Cerenkov-stimulated fluorescence are then equated back to the deposited dose in water.

"Although other methods such as scintillation and gel dosimetry have been proposed with the same goal in mind, this is the first demonstration of using only the fluorescence induced by the inherent Cerenkov radiation to measure the deposited dose," explained Adam Glaser from Dartmouth's Thayer School of Engineering. "We hope that the method will become an important tool for research and potentially clinical applications."