Using a reflectance-based correction on Cherenkov images to strengthen correlation with radiation surface dose in an anthropomorphic breast phantom

Cherenkov imaging during radiotherapy is a method by which an optical analog for the high-energy radiation beam can be observed directly on the surface of the patient. While simple geometries and volumes demonstrate a strong correlation between Cherenkov emission intensity and surface dose, in vivo data collected from 14 whole-breast patients has not exhibited the same correlation. The purpose of this anthropomorphic phantom study was to investigate a new method for improving the in vivo correlation based on a pixel-by-pixel correction from a reference reflectance image. The pixel intensities in Cherenkov images of a phantom were correlated with the surface dose measured from thermoluminescent dosimeters (TLDs) placed on the phantom's surface. Because the phantom had homogeneous optical properties, results show a no appreciable change in correlation between Cherenkov intensity and surface dose when using the correction method on images of an anthropomorphic solid silicone phantom, nor a change in the dose fall-off at the edges of the phantom. The method may improve correlation with in vivo data.