In proton therapy, a beam of protons is used to irradiate cancerous tissue, damaging its DNA and ultimately eliminating the cancer cells. Conventional dosimetry for proton therapy involves a scintillator, which is less than ideal because protons can temporarily damage (quench) the scintillator’s organic molecules; the result is that complicated formulas must be used to correct for the scintillator’s output errors. As an alternate approach, researchers at Konkuk University (Chungju, South Korea) and the National Cancer Center (Goyang, South Korea) are using the Cerenkov radiation produced in plastic fibers as a signal.
Cerenkov radiation occurs when a charged particle travels through a medium at a speed faster than the speed of light in the medium. It is not generated from scintillation, and is not quenched (in this case, it is actually generated by secondary electrons produced by the proton’s passage). The resulting fiber-optic Cerenkov radiation sensor, with the Cerenkov radiation measured by a photomultiplier tube, has a linear dose measurement as a function of dose, as determined using a 7-cm-diameter, 180 MeV proton beam measured at a depth of 15 cm in water (1 Gy = 1 J/kg). The researchers are working on using shorter lengths of fiber for higher spatial resolution, and note that the technique can be used for dosimetry of other heavy particles used in cancer therapy. Contact Bongsoo Lee at [email protected].
