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

Abstract

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.

Monte Carlo studies on the influence of focal spot size and intensity distribution on spatial resolution in magnification mammography

“…Muntz and Logan (1979) studied experimentally the effect of magnification on image quality characteristics utilizing a focal spot of 0.15 mm, while Funke et al (1998) tried to construct a microfocus which would result in a higher spatial resolution. As far as the focal spot intensity distribution is concerned, only a few studies have been published, referring to its experimental measurement and its effect on spatial resolution, utilizing phantoms containing bar patterns, mainly for contact mammography (Matsui and Katsuhiro 1985, Nickoloff et al 1990, Prasad et al 1976, Spyrou et al 2002. However, to our knowledge, no studies have been performed regarding the effect of both focal spot size and focus intensity distribution on spatial resolution towards the direction of magnification, utilizing Monte Carlo simulation and the edge method instead of bar patterns.…”

Optimization of magnification mammography using monte carlo simulation techniques

“…Regarding the image quality, contrast to noise ratio (CNR) and spatial resolution are the most common quantities considered by most of the authors. Especially spatial resolution is directly connected to the focal spot size and the x-ray intensity distribution (Law 1993, Matsui and Katsuhiro 1985, Sickles 1980. The x-ray intensity distribution, also called focus intensity distribution, is a crucial parameter regarding the image quality in contact and magnification mammography (Nickoloff et al 1990, Prasad et al 1976.…”