Ionization produced by electron beams beneath curved surfaces.

Ionization produced by high-energy (6-18 MeV) electrons beneath cylindrical surfaces has been measured and compared to ionization at corresponding locations under a flat surface. Results are reported as ionization ratios over a range of depths, off-axis distances, radii of curvature, and electron energies. Phantoms with cylindrical entrance surfaces (radii 6-15 cm) were utilized to simulate patient contours.

Problems with contrast-detail curves for CT performance evaluation.

Contrast-detail curves have been used frequently to describe the low contrast performance characteristics of computed tomography (CT) scanners. However, such curves can produce misleading conclusions if the effects of all variables influencing CT images are not considered. As shown in this experimental study, improperly designed contrast-detail curves disguise differences in CT performance when the same object is imaged with different x-ray spectra.