The primary aim of the present work was to analyze the effects of varying scatter-to-primary ratios on the appearance of
simulated nodules in chest tomosynthesis section images. Monte Carlo simulations of the chest tomosynthesis system
GE Definium 8000 VolumeRAD (GE Healthcare, Chalfont St. Giles, UK) were used to investigate the variation of
scatter-to-primary ratios between different angular projections. The simulations were based on a voxel phantom created
from CT images of an anthropomorphic chest phantom. An artificial nodule was inserted at 80 different positions in the
simulated phantom images, using five different approaches for the scatter-to-primary ratios in the insertion process. One
approach included individual determination of the scatter-to primary-ratio for each projection image and nodule location,
while the other four approaches were using mean value, median value and zero degree projection value of the scatter-toprimary
ratios at each nodule position as well as using a constant scatter-to-primary ratio of 0.5 for all nodule positions.
The results indicate that the scatter-to-primary ratios vary up to a factor of 10 between the different angular
tomosynthesis projections (±15°). However, the error in the resulting nodule contrast introduced by not taking all
variations into account is in general smaller than 10 %.
ViewDEX (Viewer for Digital Evaluation of X-ray images) is a Java-based DICOM-compatible software tool for
observer performance studies that can be used to display medical images with simultaneous registration of the observer's
response. The current release, ViewDEX 2.0 is a development of ViewDEX 1.0, which was released in 2007. Both
versions are designed to run in a Java environment and do not require any special installation. For example, the program
can be located on a memory stick or stand alone hard drive and be run from there. ViewDEX is managed and configured
by editing property files, which are plain text files where users, tasks (questions, definitions, etc.) and functionality
(WW/WL, PAN, ZOOM, etc.) are defined. ViewDEX reads all common DICOM image formats and the images can be
stored in any location connected to the computer. ViewDEX 2.0 is designed so that the user in a simple way can alter if
the questions presented to the observers are related to localization or not, enabling e.g. free-response ROC, standard
ROC and visual grading studies, as well as combinations of these, to be conducted in a fast and efficient way. The
software can also be used for bench marking and for educational purposes. The results from each observer are saved in a
log file, which can be exported for further analysis. The software is freely available for non-commercial purposes.
Observer performance studies are time-consuming tasks, both for the participating observers and for the scientists
collecting and analyzing the data. A possible way to optimize such studies is to perform the study in a completely digital
environment. A software tool - ViewDEX (Viewer for Digital Evaluation of X-ray images) - has been developed in Java,
enabling it to function on almost any computer. ViewDEX is a DICOM-compatible software tool that can be used to
display medical images with simultaneous registration of the observer's response. ViewDEX is designed so that the user
in a simple way can alter the types of questions and images presented to the observers, enabling ROC, MAFC and visual
grading studies to be conducted in a fast and efficient way. The software can also be used for bench marking and for
educational purposes. The results from each observer are saved in a log file, which can be exported for further analysis.
The software is freely available for non-commercial purposes.
The aim of this work was to investigate and quantify the effects of system noise, nodule location, anatomical noise and anatomical background on the detection of lung nodules in different regions of the chest x-ray. Simulated lung nodules of diameter 10 mm but with varying detail contrast were randomly positioned in four different kinds of images: 1) clinical images collected with a 200 speed CR system, 2) images containing only system noise (including quantum noise) at the same level as the clinical images, 3) clinical images with removed anatomical noise, 4) artificial images with similar power spectrum as the clinical images but random phase spectrum. An ROC study was conducted with 5 observers. The detail contrast needed to obtain an Az of 0.80, C0.8, was used as measure of detectability. Five different regions of the chest x-ray were investigated separately. The C0.8 of the system noise images ranged from only 2% (the hilar regions) to 20% (the lateral pulmonary regions) of those of the clinical images. Compared with the original clinical images, the C0.8 was 16% lower for the de-noised clinical images and 71% higher for the random phase images, respectively, averaged over all five regions. In conclusion, regarding the detection of lung nodules with a diameter of 10 mm, the system noise is of minor importance at clinically relevant dose levels. The removal of anatomical noise and other noise sources uncorrelated from image to image leads to somewhat better detection, but the major component disturbing the detection is the overlapping of recognizable structures, which are, however, the main aspect of an x-ray image.
Thirty images with added simulated pathological lesions at two different dose levels (100% and 10% dose) were evaluated with the free-response forced error experiment by nine experienced radiologists. The simulated pathological lesions present in the images were classified according to four different parameters: the position within the lumbar spine, possibility to perform a symmetrical (left-right) comparison, the lesion contrast, and the complexity of the surrounding background where the lesion was situated. The detectability of each lesion was calculated as the fraction of radiologists who successfully detected the lesion before a false positive error was made. The influence of each of the four parameters on lesion detectability was investigated. The results of the study show that the influence of lesion contrast is the most important factor for detectability. Since the dose level had a limited effect on detectability, large dose savings can be made without reducing the detectability of pathological lesions in lumbar spine radiography.
To evaluate the image quality of clinical radiographs with two different methods, and to find correlations between the two methods.
Based on fifteen lumbar spine radiographs, two new sets of images were created. A hybrid image set was created by adding two distributions of artificial lesions to each original image. The image quality parameters spatial resolution and noise were manipulated and a total of 210 hybrid images were created. A set of 105 disease-free images was created by applying the same combinations of spatial resolution and noise to the original images. The hybrid images were evaluated with the free-response forced error experiment (FFE) and the normal images with visual grading analysis (VGA) by nine experienced radiologists. The VGA study showed that images with low noise are preferred over images with higher noise levels. The alteration of the MTF had a limited influence on the VGA score. For the FFE study the visibility of the lesions was independent of the spatial resolution and the noise level. In this study we found no correlation between the two methods, probably because the detectability of the artificial lesions was not influenced by the manipulations of noise level and resolution. Hence, the detection of lesions in lumbar spine radiography may not be a quantum-noise limited task. The results show the strength of the VGA technique in terms of detecting small changes in the two image quality parameters. The method is more robust and has a higher statistical power than the ROC related method and could therefore, in some cases, be more suitable for use in optimization studies.
A physical and clinical evaluation of four different display systems intended for the presentation of medical x-ray images was performed. State-of-the-art b/w display devices were studied as well as a low-cost color display. The systems tested were: a) CRT 21' b/w 1K, b) CRT 21' b/w, 2K, c) CRT 21' color, 1K, d) LCD 20.8' b/w, 1.5K. All displays were, as far as possible, adjusted to conform to DICOM 3.0 part 14. The physical evaluation included quantities such as resolution, flickering and uniformity. The clinical evaluation was performed by 15 radiologists using visual grading analysis of one phantom chest image and 12 clinical images of the chest and small bones. One subtle pathological structure and one anatomical structure were rated. The CRT b/w 1K display was used as the reference display system. All displays were evaluated at two different luminance levels (160 and 320 cd/m2) and viewed under two different ambient light conditions (10 and 40 lux). The LCD 1.5K display was rated best and the color CRT display was rated worst for both luminance levels. The result for the color CRT display - unable to produce more than 120 cd/m2 - at the high ambient light setting was very poor.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.