Mr. John G. Stowe Profile

John G. Stowe

at Univ College Dublin

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Publications (2)

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Proceedings Article | 13 March 2009 Paper

The impact of faceplate surface characteristics on detection of pulmonary nodules

R. Toomey, J. Ryan, M. McEntee, J. McNulty, M. Evanoff, F. Cuffe, T. Yoneda, J. Stowe, P. Brennan

Proceedings Volume 7263, 726307 (2009) https://doi.org/10.1117/12.813505

KEYWORDS: Reflection, Light sources and illumination, Specular reflections, Chest, Radiology, Statistical analysis, Diffusion, Light scattering, Calibration, Medical imaging

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Introduction In order to prevent specular reflections, many monitor faceplates have features such as tiny dimples on their surface to diffuse ambient light incident on the monitor, however, this "anti-glare" surface may also diffuse the image itself. The purpose of the study was to determine whether the surface characteristics of monitor faceplates influence the detection of pulmonary nodules under low and high ambient lighting conditions. Methods and Materials Separate observer performance studies were conducted at each of two light levels (<1 lux and >250 lux). Twelve examining radiologists with the American Board of Radiology participated in the darker condition and eleven in the brighter condition. All observers read on both smooth "glare" and dimpled "anti-glare" faceplates in a single lighting condition. A counterbalanced methodology was utilized to minimise memory effects. In each reading, observers were presented with thirty chest images in random order, of which half contained a single simulated pulmonary nodule. They were asked to give their confidence that each image did or did not contain a nodule and to mark the suspicious location. ROC analysis was applied to resultant data. Results No statistically significant differences were seen in the trapezoidal area under the ROC curve (AUC), sensitivity, specificity or average time per case at either light level for chest specialists or radiologists from other specialities. Conclusion The characteristics of the faceplate surfaces do not appear to affect detection of pulmonary nodules. Further work into other image types is being conducted.

Proceedings Article | 6 March 2008 Paper

Visual adaptation: softcopy image contribution to the observer's field of view

R. Toomey, K. Curran, C. D'Helft, M. Joyce, J. Stowe, J. Ryan, M. McEntee, D. Manning, P. Brennan

Proceedings Volume 6917, 69170O (2008) https://doi.org/10.1117/12.770305

KEYWORDS: Eye, Visualization, Light sources and illumination, LCDs, Radiology, Medical imaging, Diagnostics, Reflection, Image visualization, Medicine

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Purpose Detection of low-contrast details is highly dependent on the adaptation state of the eye. It is important therefore that the average luminance of the observer's field of view (FOV) matches those of softcopy radiological images. This study establishes the percentage of FOV filled by workstations at various viewing distances. Methods Five observers stood at viewing distances of 20, 30 and 50cm from a homogenous white surface and were instructed to continuously focus on a fixed object at a height appropriate level. A dark indicator was held at this object and then moved steadily until the observer could no longer perceive it in his/her peripheral vision. This was performed at 0°, 90°, 180° and 270° clockwise from the median sagittal plane. Distances were recorded, radii calculated and observer and mean FOV areas established. These values were then compared with areas of typical high and low specification workstations. Results Individual and mean FOVs were 7660, 15463 and 30075cm² at viewing distances of 20, 30 and 50cm respectively. High and low specification monitors with respective areas of 1576.25 and 921.25cm² contributed between 5 to 21% and 3 to 12% respectively to the total FOV depending on observer distance. Limited inter-observer variances were noted. Conclusions Radiology workstations typically comprise between only 3 and 21% of the observer's FOV. This demonstrates the importance of measuring ambient light levels and surface reflection coefficients in order to maximise adaptation and observer's perception of low contrast detail and minimise eye strain.

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