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Exposure indicators
EI estimates receptor exposure; DI tells you how far it is from target, and plus 3 means double.
The rule
An exposure indicator is a number the digital system reports after each exposure, estimating how much radiation reached the detector in the anatomy of interest. It is not patient dose. Older systems used vendor-specific scales, some rising and some falling with exposure. The standardized system uses three terms: the exposure index, EI, which rises in proportion to receptor exposure; the target exposure index, the value the department wants for that exam; and the deviation index, DI, which tells you how far this image is from target.