Background The document “European Guidelines on Quality Criteria for Diagnostic Radiographic Images” describes the visualisation of anatomical criteria to which a radiograph of diagnostic quality should comply. This research investigates the correlation between the evaluation of anatomical structures, presented in the European guidelines, and the classification of radiographs for diagnostic acceptability. Methods Sixteen radiographers classified 22 chest radiographs in terms of diagnostic acceptability using the RadLex categories, and scored the representation of five anatomical criteria on a scale from 1 to 5. All radiographs were visualised with ViewDex on a DICOM calibrated display. Observers were recruited in Belgium and Ireland. An interclass correlation coefficient was applied to evaluate internal consistency for each observer group. A Mann–Whitney U-test was applied to investigate differences in classification between countries. The relationship with the evaluation of anatomical structures was investigated with ordinal logistic regression. Results Both groups of observers performed with acceptable consistency. The Mann–Whitney U test illustrated a significant difference in classification between the two countries. The ordinal logistic regression indicated for each country a weak correlation between the RadLex and the anatomical structures. Certain factors in the radiograph, possibly others than anatomical elements, must be significantly better before the observer will attribute a higher RadLex score. Conclusion The relationship between the evaluation of anatomical criteria and the diagnostic acceptability is weak for both countries. When assigning a radiograph to a certain category of acceptability, other factors influence the decision.
Introduction: Radiographers evaluate anatomical structures to judge clinical acceptability of a radiograph. Whether a radiograph is deemed acceptable for diagnosis or not depends on the individual decision of the radiographer. Individual decisions cause variation in the accepted image quality. To minimise these variations definitions of acceptability, such as in RadLex, were developed. On which criteria radiographers attribute a RadLex categories to radiographs is unknown. Insight into these criteria helps to further optimise definitions and reduce variability in acceptance between radiographers. Therefore, this work aims the evaluation of the correlation between the RadLex classification and the evaluation of anatomical structures, using a Visual Grading Analysis (VGA) Methods: Four radiographers evaluated the visibility of five anatomical structures of 25 lateral cervical spine radiographs on a secondary class display with a VGA. They judged clinical acceptability of each radiograph using RadLex. Relations between VGAS and RadLex category were analysed with Kendall’s Tau correlation and Nagelkerke pseudo-R². Results: The overall VGA score (VGAS) and the RadLex score correlate (rτ= 0.62, p<0.01, R2=0.72) strongly. The observers’ evaluation of contrast between bone, air (trachea) and soft tissue has low value in predicting (rτ=0.55, p<0.01, R2=0.03) the RadLex score. The reproduction of spinous processes (rτ=0.67, p<0.01, R2=0.31) and the evaluation of the exposure (rτ=0.65, p<0.01, R2=0.56) have a strong correlation with high predictive value for the RadLex score. Conclusion: RadLex scores and VGAS correlate positively, strongly and significantly. The predictive value of bony structures may support the use of these in the judgement of clinical acceptability. Considerable inter-observer variations in the VGAS within a certain RadLex category, suggest that observers use of observer specific cut-off values.
A number of different viewing distances are recommended by international agencies, however none with specific reference to radiologist performance. The purpose of this study was to ascertain the extent to which radiologists performance is affected by viewing distance on softcopy skeletal reporting. Eighty dorsi-palmar (DP) wrist radiographs, of which half feature 1 or more fractures, were viewed by seven observers at 2 viewing distances, 30cm and 70cm. Observers rated the images as normal or not on a scale of 1 to 5 and could mark multiple locations on the images when they visualised a fracture. Viewing distance was measured from the centre of the face plate to the outer canthus of the eye. The DBM MRM analysis showed no statistically significant differences between the area under the curve for the two distances (p = 0.482). The JAFROC analysis, however, demonstrated a statistically significantly higher area under the curve with the 30cm viewing distance than with the 70 cm distance (p = 0.035). This suggests that while observers were able to make decisions about whether an image contained a fracture or not equally well at both viewing distances, they may have been less reliable in terms of fracture localisation or detection of multiple fractures. The impact of viewing distance warrants further attention from both clinical and scientific perspectives.
Purpose: This study examines the relationship between ambient lighting level and image manipulation. Method: Academic radiographers (n=10), with experience in observer performance studies, each assessed 70 postero-anterior projection radiographs of the wrist / scaphoid in both low (12.5 lux) and high (150 lux) ambient lighting. Half of the images featured one or more acute fractures and the remainder did not. Observers were encouraged to window the images to a level they felt was appropriate and, requested to rate their confidence that an acute fracture was present, marking the locations of any suspected acute fractures on the image. The images were displayed on a secondary-class monitor using Ziltron software, which recorded the adjustments to brightness and contrast made for each image. The images were presented in different orders for each lighting level to reduce potential memory effects. Results: Student’s t-tests were applied to compare the mean brightness and contrast adjustments made to the images in each ambient lighting level. Tests were carried out to include all images, only positive cases, and only cases where observers elected to change the brightness and/or contrast. No statistically significant differences were noted except when images where no brightness/contrast adjustments were made were discounted. In that case, mean brightness levels were slightly higher in the high ambient light level (p=0.049). Conclusion: No convincing difference in adjustments of brightness and contrast between high and low ambient lighting levels, although further research is warranted.
Eye tracking has been used by many researchers to try to shed light on the perceptual processes involved in medical image perception. Despite a large volume of data having been published regarding radiologist viewing patterns for static images, and more recently for stacked imaging modalities, little has been produced concerning angiographic images, which commonly have substantially different characteristics. A study was performed in which 7 expert radiologists viewed a range of digital subtraction angiograms of the peripheral vascular system. Initial results are presented. The observers were free to control the rate at which they viewed the images. Eye position data was recorded for each participant using Tobii TX300 eyetrackers. Analysis was performed in Tobii Studio software and included qualitative analysis of gaze pattern and analysis of metrics including first and total fixation duration etc. for areas of clinical interest. Early results indicate that experts briefly fixate on lesions but do not dwell in the area, rather continuing to inspect the more distal vascular segments before returning. Some individual variation was noted. Further research is required and ongoing.
This study reports an incidental finding from a larger work. It examines the relationship between spatial
resolution and nodule detection for chest radiographs. Twelve examining radiologists with the
American Board of Radiology read thirty chest radiographs in two conditions - full (1500 × 1500
pixel) resolution, and 300 × 300 pixel resolution linearly interpolated to 1500 × 1500 pixels. All
images were surrounded by a 10-pixel sharp grey border to aid in focussing the observer's eye when
viewing the comparatively unsharp interpolated images. Fifteen of the images contained a single
simulated pulmonary nodule. Observers were asked to rate their confidence that a nodule was present
on each radiograph on a scale of 1 (least confidence, certain no lesion is present) to 6 (most confidence,
certain a lesion was present). All other abnormalities were to be ignored. No windowing, levelling or
magnification of the images was permitted and viewing distance was constrained to approximately
70cm. Images were displayed on a 3 megapixel greyscale monitor. Receiver operating characteristic
(ROC) analysis was applied to the results of the readings using the Dorfman-Berbaum-Metz multiplereader,
multiple-case method. No statistically significant differences were found with either readers
and cases treated as random or with cases treated as fixed. Low spatial frequency information appears
to be sufficient for the detection of chest lesion of the type used in this study.
This study aimed to measure the sound levels in Irish x-ray departments. The study then established whether these levels
of noise have an impact on radiologists performance
Noise levels were recorded 10 times within each of 14 environments in 4 hospitals, 11 of which were locations where
radiologic images are judged. Thirty chest images were then presented to 26 senior radiologists, who were asked to
detect up to three nodular lesions within 30 posteroanterior chest x-ray images in the absence and presence of noise at
amplitude demonstrated in the clinical environment.
The results demonstrated that noise amplitudes rarely exceeded that encountered with normal conversation with the
maximum mean value for an image-viewing environment being 56.1 dB. This level of noise had no impact on the ability
of radiologists to identify chest lesions with figure of merits of 0.68, 0.69, and 0.68 with noise and 0.65, 0.68, and 0.67
without noise for chest radiologists, non-chest radiologists, and all radiologists, respectively. the difference in their
performance using the DBM MRMC method was significantly better with noise than in the absence of noise at the 90%
confidence interval (p=0.077). Further studies are required to establish whether other aspects of diagnosis are impaired
such as recall and attention and the effects of more unexpected noise on performance.
Dynamic cueing is an effective way of stimulating perception of regions of interest within radiological images. This
study explores the impact of a novel teaching tool using dynamic cueing for lesion detection on plain chest radiographs.
Materials and methods
Observer performance studies were carried out where 36 novices examined 30 chest images in random order. Half of
these contained between one and three simulated pulmonary nodules. Three groups were investigated: A (control: no
teaching tool), B (retested immediately after undergoing the teaching tool) and C (retested a week after undergoing the
teaching tool). The teaching tool involved dynamically displaying the same images with and without lesions. Results
were compared using Receiver Operating Characteristics (ROC), sensitivity and specificity analyses.
The second reading showed significantly greater area under the ROC curve (Az value) (p<0.0001) and higher sensitivity
value (p=0.004) compared to the first reading for Group B. No differences between readings were demonstrated for
groups A or C. When the magnitudes of the above changes were compared between Group B and the other two groups,
greater changes in Az value for Group B were noted (B vs. A:p=0.0003, B vs. C:p=0.0005). For sensitivity, when Group
B was compared to Group A, the magnitude of the change was significantly greater (p=0.0029) whereas when Group B
was compared to Group C, the magnitude change demonstrated a level approaching significance (p=0.0768).
The novel teaching tool improves identification of pulmonary nodular lesions on chest radiographs in the short term.
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.
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.
The characteristics of the faceplate surfaces do not appear to affect detection of pulmonary nodules. Further work into
other image types is being conducted.
Visualisation of anatomical or pathological image data is highly dependent on the eye's ability to discriminate between
image brightnesses and this is best achieved when these data are presented to the viewer at luminance levels to which the
eye is adapted. Current ambient light recommendations are often linked to overall monitor luminance but this relies on
specific regions of interest matching overall monitor brightness.
The current work investigates the luminances of specific regions of interest within three image-types: postero-anterior
(PA) chest; PA wrist; computerised tomography (CT) of the head. Luminance levels were measured within the hilar
region and peripheral lung distal radius and supra-ventricular grey matter. For each image type average monitor
luminances were calculated with a calibrated photometer at ambient light levels of 0, 100 and 400 lux. Thirty samples of
each image-type were employed, resulting in a total of over 6,000 measurements.
Results demonstrate that average monitor luminances varied from clinically-significant values by up to a factor of 4, 2
and 6 for chest, wrist and CT head images respectively. Values for the thoracic hilum and wrist were higher and for the
peripheral lung and CT brain lower than overall monitor levels. The ambient light level had no impact on the results.
The results demonstrate that clinically important radiological information for common radiological examinations is not
being presented to the viewer in a way that facilitates optimised visual adaptation and subsequent interpretation. The
importance of image-processing algorithms focussing on clinically-significant anatomical regions instead of radiographic
projections is highlighted.
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.
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
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.
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.