Helical computed tomography: patient exposure and appropriate use

Helical CT is the imaging modality that delivers the highest exposure to pa tients. For each acquisition, the average radiation dose is between 20 and 30 mGy. This dose can potentially be reduced by decreasing the intensity or voltage and by increasing the pitch. Helical data can be reformatted to ob tain images with smaller increment or multiplanar reconstructions, hence re ducing the need for additional acquisitions. Hardware and software devices designed for dose reduction must be systematically used. Operators of CT un its should be aware of the radiation dose delivered with helical CT and mus t carefully assess the need of each additional acquisition. Obsolete protoc ols such as angulation of the gantry for lumbar CT, which increases patient exposure, should no longer be used. Rational use of helical CT decreases r adiation exposure and is faster, whereas improper use increases radiation e xposure without added benefit.