In radiation therapy patients are treated by high energy x-ray beams with complex setup and treatment plans. Because of the nature of the setup and delivery, it is not possible to know the dose delivered, rather the clinic relies upon complex simulations and careful pre-treatment human setup steps. But the ability to image the treatment delivery by capturing the Cherenkov emission allows the treatment team to see the actually daily delivery to each patient, for the first time. Cherenkov cameras are time-gated image-intensified CMOS cameras that capture the small bursts of Cherenkov emission that occur in each 4 microsecond pulse of the linear accelerator. The cameras have been designed to self trigger on the scattered radiation, and the image intensifier only activates during the pulses, thereby suppressing ambient room lights significantly. The use of filtering and lens choice also maximize the sensitivity to achieve single-photon level imaging of Cherenkov emissions, with the room lights being present. The recent optimizations to the cameras and their use cases will be reviewed to illustrate the technical improvements and the value of this imaging to the clinical team.
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