Using both contrast detail and receiver operating characteristic (ROC) evaluation tests, we evaluated different quality images, produced with different film-screen combinations. ROC curves were obtained for six observers who were attempting to detect lung nodules and pulmonary infiltrates. The contrast detail curves were obtained from images of regular circular test patterns of differing contrast, which had been presented to the observers. Our results indicate that contrast detail tests can be used for relative ranking of image systems prior to detailed ROC testing.
Detection of lung nodules was assessed using a series of radiographs which were either normal or showed only one nodule. Stereoscopic pairs were obtained in 26 cases (10 positive and 16 normal). A "singles" series comprising one radiograph from each pair was presented to each observer on three occasions. The pairs were later presented side by side and finally were viewed stereoscopically. The results indicate that a second shifted radiograph improves detection of lung nodules enough to be cost-effective. The shifted radiographs do not need to be viewed stereoscopically.
The effectiveness of a shaped filter in improving nodule and infiltrate detection was measured by observer performance testing. Seven observers read 152 test radiographs of the chest obtained from human volunteers. Half the test radiographs had target images. Observer performance in detecting nodule or infiltrate images was compared with the shaped-filter system and with a conventional chest imaging system. The results were analyzed using receiver operating characteristic (ROC) techniques and indicate that the filter technique was not significantly different from the conventional technique in infiltrate depiction. Observer performance in detecting nodules was slightly worse on images obtained with the shaped-filter system.
Agent Orange exposure and its long-term health consequences on Vietnam veterans have been widely discussed in the past few years. Myriad physical and mental disabilities have been studied with regard to exposure to various herbicides. The number of persons potentially exposed is large, since 2.4-2.8 million U.S. military personnel served in Vietnam. A case-control study was undertaken to determine if persons who served in the U.S. military in Vietnam have either cardiovascular or pulmonary effects that can be demonstrated on long-term follow-up chest radiographs. Information regarding military service in Vietnam was obtained from interviews and, in some cases, review of military records. Vietnam veterans did not have an increased prevalence of abnormalities on follow-up chest radiographs. A subset of Vietnam veterans who had greater estimated opportunities for Agent Orange exposure also did not appear to be at greater risk than the control population.
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