Since the .his format images captured by Elekta aren’t recognized by Pylinac, I have to use TIFF format instead. However, when using TIFF, I need to provide the DPI (dots per inch). My question is, should the DPI correspond to the physical size of the imaging plate, or should it be scaled to the size at the isocenter (SAD = 100 cm)?
If you’re using the tiff_to_dicom function or FileImage, there is an sid parameter, which will correct the pixel size back to the SAD. So enter the physical distance between pixels on the panel.