Simulation of subtle lung nodules in projection chest radiography.

Abstract

To measure the radiologic characteristics of subtle lung nodules and develop nodule phantoms that simulate these characteristics. From a database of chest radiographs, 16 radiographs that showed confirmed subtle lung nodules were selected. The optical density values surrounding each nodule were obtained, and the radiologic characteristic of the nodules were evaluated. A set of Teflon nodule phantoms with similar x-ray transmission and variability was designed and fabricated. The contrast characteristics of the images of the nodule phantoms were measured. Most of the subtle nodules appeared to have diffuse edges with Gaussian-like contrast profiles. The contrast and size characteristics of the nodule phantom images fulfilled the design criteria within a 4% deviation. The radiologic pattern of subtle lung nodules is poorly simulated by nodule phantoms with simple spherical or disk shapes. The nodule phantoms in this study produce realistic radiographic patterns with an energy-dependent attenuation equivalent to that of tissue. The nodule phantoms are intended for use in experiments involving human subjects.