Dose reduction in computed tomography by attenuation-based on-line modulation of tube current: evaluation of six anatomical regions

This study investigated the potential of attenuation-based on-line modulati on of tube current to reduce the dose of computed tomography (in milliamper es) without loss in image quality. The dose can be reduced for non-circular patient cross-sections by reducing the tube current at the angular positio ns at which the diameter through the patient diameter smallest. We investig ated a new technical approach with attenuation-based on-line modulation of tube current. Computed tomographic projection data were analyzed to determi ne the optimal milliampere for each projection angle in real time, instead performing prior measurements with localizer radiographs. We compared image quality, noise pattern dose for standard scans and for scans with attenuat ion-based on-line modulation of tube current group of 30 radiation therapy patients. Six different anatomical regions were examined: head, shoulder, t horax, abdomen, pelvis, and extremities (knee). Image quality was evaluated by four radiologists in a blinded fashion. We found the dose to be reduced typically by 15-50%. In general, no deterioration in quality was observed. Thus the dose in computed tomography be reduced substantially by technical measures without sacrificing image quality. Attenuation-based on-line modu lation of tube current is an efficient and practical means for this.