A uniform focal spot X-ray tube with improved MTF and kW rating

Focal spots of conventional x-ray tubes have a "twin-peaked" intensity distribution perpendicular to the axis of the tube. This results in a poorer modulation transfer function (MTF) than would be obtained with a uniform intensity distribution having the same input power rating (kW). It is demonstrated that such an intensity distribution can be obtained by employing a ribbon-shaped filament. Experimental results are presented for both the ribbon filament and a conventional helical coil using a stationary anode. For a 0.3-mm focal spot spatial frequency of 2.0 c/mm, a uniform intensity distribution gave an MTF of about 50%, compared to 20% for a conventional tube at the same kW rating.