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Nodule detection in digital chest radiography: part of image background acting as pure noise.

Journal article
Authors Magnus Båth
Markus Håkansson
Sara Börjesson
Susanne Kheddache
François O Bochud
Francis R Verdun
Lars Gunnar Månsson
Published in Radiation protection dosimetry
Volume 114
Issue 1-3
Pages 102-8
ISSN 0144-8420
Publication year 2005
Published at Institute of Selected Clinical Sciences, Department of Radiation Physics
Institute of Selected Clinical Sciences, Department of Radiology
Pages 102-8
Language en
Keywords Artifacts, Humans, Image Processing, Computer-Assisted, Lung, pathology, radiography, Lung Neoplasms, diagnosis, radiography, Models, Anatomic, ROC Curve, Radiographic Image Enhancement, methods, Radiographic Image Interpretation, Computer-Assisted, methods, Radiography, methods, Radiography, Thoracic, methods, Scattering, Radiation, Software, X-Rays
Subject categories Radiology, Radiological physics


There are several factors that influence the radiologist's ability to detect a specific structure/lesion in a radiograph. Three factors that are commonly known to be of major importance are the signal itself, the system noise and the projected anatomy. The aim of this study was to determine to what extent the image background acts as pure noise for the detection of subtle lung nodules in five different regions of the chest. A receiver operating characteristic (ROC) study with five observers was conducted on two different sets of images, clinical chest X-ray images and images with a similar power spectrum as the clinical images but with a random phase spectrum, resulting in an image background containing pure noise. Simulated designer nodules with a full-width-at-fifth-maximum of 10 mm but with varying contrasts were added to the images. As a measure of the part of the image background that acts as pure noise, the ratio between the contrast needed to obtain an area under the ROC curve of 0.80 in the clinical images to that in the random-phase images was used. The ratio ranged from 0.40 (in the lateral pulmonary regions) to 0.83 (in the hilar regions) indicating that there was a large difference between different regions regarding to what extent the image background acted as pure noise; and that in the hilar regions the image background almost completely acted as pure noise for the detection of 10 mm nodules.

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