Infographics / Fluoroscopy

Electronic magnification mode

Two side-by-side cutaways of the same image intensifier tube. In normal mode the whole input phosphor is focused by the electron lens through a crossover onto the fixed output phosphor. In magnification mode a stronger focusing-electrode voltage selects only the central part of the input phosphor and maps it onto the same output phosphor, shifting the crossover away from the output. The result is higher spatial resolution but lower minification gain, so automatic brightness control raises tube output and patient skin dose rises. The tube geometry and patient position are unchanged.