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.
Radiation doses for 3 common types of cardiac radiological examinations where
investigated: coronary angiography (CA), percutaneous coronary intervention (PCI) and
pacemaker insertions (PPI). 22 cardiac imaging suites participated in the study. Radiation
dose was monitored for 1804 adult patients using dose area product (DAP) meters.
Operational and examination details such as cardiologist grade, patient details and
examination complexity were recorded for each examination. Both intra and inter-hospital variations where demonstrated by the results. Individual patient DAP values ranged from 136-23,101cGycm2, 475-41,038cGycm2 and 45- 17,192cGycm2 for CA, PCI and PPI respectively, with third quartile values of 4,173cGycm2, 8,836cGycm2 and 2,051cGycm2. Screening times varied from 0.22-27.6mins, 1.8-98mins and 0.33-54.5mins for CA, PCI and PPI respectively.
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