Universal MV-kV imager for radiotherapy[1]

Electronic portal mega-electronvolt (MV) monitoring for radiation therapy is very important for tumor localization. Furthermore, in the latest systems, before the radiation treatment, the patient is also positioned on the treatment bed with a flat-panel detector (FPD) based kilo-electronvolt (kV) CT scan for better soft tissue visibility. In the article we prove by measurement and imaging that a regular Cu-GOS scintillator combination on an a-Si TFT + photodiode FPD can work in reverse direction with the same efficiency as in forward direction at high energy (MV) imaging. More importantly, in reverse mode it can be used also as a kV imager because the Cu plate, which contributes towards improved imaging at MV energy, does not block the kV X-ray beams in this direction. So we can have a universal MV-kV imager integrated into one.