American Association of Physicists in Medicine, 35th Annual Meeting, Washington D.C., 8-12 August. Medical Physics, 20(3):921, May/June 1993.
Geometric magnification of 1.3X to 18.X is now performed in mammography and angiography using rotating anode x-ray tubes having measured focal spot sizes of .13 to .16 mm. Substantially smaller focal spot sizes are achieved with magnetically focused x-ray tubes. 10X specimen radiographs made with a .01 mm focal spot size and high efficiency detector have low noise and high resolution for a technique of 0.2 mA, 1 sec, 30 kVp. 5X radiographs of phantoms simulating the breats and extremities have good quality for 1.0 mA, 1 sec, 50 kVp techniques and a .05 mm focal spot size. A perrformance advantage relative to contact radiography performed with the same subject dose is achieved by using high DQE, low detail detectors. A thermal advantage is experienced because the tube power limit for microfocus tubes is proportional to focal spot size, whereas the quantum flux through the object improves as the square of the source to object distance. Application of these methods for in-vivo evaluation of suspicious breast masses, orthopedic stress fractures, and bone demineralization is suggested.