Image noise and radiation dose using an automatic tube current modulation technique at 64-detector computed tomography: effect of off-center patient position, bowtie filter type, and scan projection radiograph.

We describe the effect of the off-center position, the bowtie filter type, and the direction of scan projection radiograph on the radiation dose and image noise of 64-detector computed tomographic scans using the automatic tube current modulation technique. On anteroposterior scan projection radiographs, the tube current ratio increased, with an increase in the off-center position of the phantom irrespective of the filter size. On lateral scan projection radiographs, it remained constant with each bowtie filter type regardless of the off-center phantom position.