Gantry angulation in brain CT: dosage implications, effect on posterior fossa artifacts, and current international practice.

The aim of this study was first to determine the effect of use of different scan planes at computed tomography (CT) of the brain on lens radiation dose and on severity of posterior fossa artifact. Twenty patients requiring nonenhanced and contrast material-enhanced brain CT scanning were selected. Each was scanned with two different beam angulations, one passing through the eyes and one avoiding them, and the resulting radiation doses were measured. Angling of the beam to avoid the orbit reduced the dose by 87%, while the severity of posterior fossa artifacts was not significantly different. Second, the implications of these results was assessed by means of an international questionnaire survey of current scanning technique. Only 32% of the respondents routinely avoided the eye during brain CT. No single scan plane was accepted by the respondents as being superior in terms of minimizing posterior fossa artifact. The authors conclude that the potential exists for a reduction in lens dose after reappraisal of radiologic practice in brain CT.