Option B Medical Physics Chapter 5 X-ray imaging Word X-ray electromagnetic wave wavelength photographic film ionise X-ray tube filament anode step-up transformer rotor coil stator coil focal spot intensity photon potential difference (pd) work done continuous spectrum outer shell electron conduction electron electronvolt (eV) electron beam current efficiency attenuation intensity attenuation coefficient half-value thickness mass attenuation coefficient atomic number image sharpness focal spot image contrast lead collimator grid contrast medium beam definers metal filter intensifying screen Definition fluorescent image intensifier photocathode electrode computed tomography (CT) scanner positron voxel monochromatic