A depth-dose measuring device using a multichannel scintillating fiber array for electron beam therapy

The development of a new depth-dose measuring device for electron beam therapy is described. The device employs plastic scintillating fiber detectors inserted in a polymethylmethacrylate (PMMA) phantom in line along an incident electron beam. Output photons from a fiber, the number of which is proportional to the absorbed dose at each depth of the phantom, were converted to an electric signal with a photodiode. Each signal from the photodiode was transmitted to a personal computer through a multichannel analog-digital converter, and was processed to draw a depth-dose curve on the computer display. A depth-dose curve could be obtained in a measuring time of 5 s for each incident electron beam with an energy range between 4 and 21 MeV. The mean electron energies estimated using the curves and the depth-scaling factor for PMMA were consistent with those obtained from conventional depth-dose measurements using an ion chamber and a water phantom. The newly developed system, being simple and not time consuming, could be used routinely for quality assurance purposes in electron beam therapy.