Project: Research project

Project Details


This proposal addresses the marriage of two novel technologies, with the
overall objective to develop a practical single- and dual-energy digital
radiography system, dedicated and optimized for chest imaging. A filter
wheel equalization system compensates for over- and under-penetrated
areas in the image, by reducing or increasing the entrance exposure to
those areas. A series of computer controlled wheels are mounted near the
x-ray tube, and the filter wheels have organ-specific compensation
patterns, determined by analysis of numerous chest images, machined into
them. A low-dose prescan image is acquired with only
homogeneous-filtration present, and based on analysis of the prescan
image the computer automatically rotates the most appropriate filter
wheel patterns into position to achieve compensation and the radiographic
exposure is acquired. The heart, left lung and right lung are the
principle thoracic features which demand enormous detector latitude;
independent compensation of these structures will reduce the exposure
dynamic range and will yield better uniformity in the signal-to-noise
performance of the system. This will improve the detectability of pulmo-
nary nodules since detectability is fundamentally related to the signal
to noise ratio. The proposed detector is a novel dual phosphor (binary)
screen system, composed of two phosphors differing in energy-dependent
x-ray absorption (different k-edges), but also differing in their optical
emission properties. One phosphor (Gd2O2S:Eu, k-edge = 50 keV) emits
principally at 624 nm, and the other (y2O3:Gd, k-edge = 17 keV) emits at
315 nm. Using optical filtration, dual CCD cameras are individually
tuned to the optical emission spectrum of each phosphor, thereby allowing
the low energy and high energy images to be acquired simultaneously
during one x-ray pulse. The marriage of the filter wheel equalization
system with the binary screen detector will result in a synergistic and
comprehensive approach to chest radiography. The research methodology
includes the acquisition of a large data base of chest images (digitized
from film) to facilitate a statistical approach to the compensation
pattern design and analysis, computer simulation and design optimization
of both the compensation and detector subsystems, construction and
testing of a prototype system including image performance
characterization (MTF & DQE), and ROC analysis of experimentally acquired
images. The comprehensive approach to digital chest imaging proposed
here should increase the effectiveness of chest radiography, by
increasing the sensitivity and specificity to pulmonary nodules and other
chest pathologies.
Effective start/end date8/1/917/31/95


  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health


  • Medicine(all)


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