In an article on Cerenkov fluorescence published today by medicalphysicsweb.com, Dartmouth PhD candidate Adam Glaser explains how the light imaging technique can be used to measure an imparted dose from an X-ray photon linac beam.
The technique developed by Glaser and his Dartmouth colleagues has been verified through a series of experiments using a clinical linac from Varian Medical Systems. The first step in the process is to fill a water tank with tap water and dissolve the fluorophore (quinine sulphate) to a concentration of 1.0 g/l. Then, a standard commercial CMOS camera is positioned at a given distance from the water tank, perpendicular to the incident beam, and focused to the beam’s isocentre.
When the beam is turned on, a 2D projection image is captured using a 10 s exposure time, and an equivalent image with the beam off is recorded and subtracted to isolate the Cerenkov-excited fluorescence for direct correlation to the deposited dose.
“Each image is immediately downloaded from the camera to a computer and can be viewed in real time,” explained Glaser. “Our experiments in this proof-of-concept study show that the strength of the fluorescence signal equates near-linearly to the dose imparted in the water. We believe this is the first demonstration of using Cerenkov light to indirectly determine the spatial distribution of a charged particle’s energy deposition within a medium.”
For more on Glaser’s research, read the article on medicalphysicsweb.com.