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Visual Search in Abdominopelvic CT Interpretation

Rationale and Objectives

The objective of this study was to compare reader accuracy and time efficiency between coronal reformats of abdominopelvic computed tomography (CT) and axial images, by means of a visual search task.

Materials and methods

In this experimental crossover study, a novel visual search task, containing targets placed on actual CT images, was constructed to assess reader performance on both planes. Six trials were shown to participants in each plane, at a fixed time of 0.5 seconds per slice. The task was presented to 43 junior doctors. On each trial, participants were assessed for accuracy and confidence in finding the target on a five-point scale. Statistical analysis was performed using the Wilcoxon signed rank test, and Fleiss kappa.

Results

Coronal images took 40% less time to view overall. No significant difference was found in reader accuracy or reader confidence between the two planes. Interrater agreement was observed as fair, across a very large number of raters (43).

Conclusions

Target identification in the coronal plane is extremely similar to the axial plane on abdominopelvic CT in this study and offers a substantial time benefit. A perceptual limit to visual processing of CT images may contribute to this similarity. Greater use of coronal reformats in day-to-day practice could substantially improve radiologist workflow.

The amount of computed tomography (CT) scans performed in Australia increases at a rate of around 12% per year . Increasing CT examinations translates into an increased radiologist workload, in a throughput-driven work environment.

Scan volumes have been further increased by improvements in CT technology, particularly multidetector-row CT (MDCT). MDCT can acquire several thin slices in one rotation of the x-ray tube, resulting in speed of acquisition, high spatial resolution, and anatomic detail. Sixty-four (or greater)–slice MDCT can generate images with a spatial resolution of less than 1 mm . Use of MDCT has created a much larger volume of images to be viewed in the axial plane, mainly because of the generation of thin slices . This influx of images to the radiology workstation can create workflow problems for radiologists as a result of “image overload” .

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Materials and methods

Participants

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Technique

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Figure 1, Typical target stimuli. Note the presence of a square in the posterobasal segment of the right lower lobe (a) and an “x” in the bladder anterior wall (b) .

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Statistical Analysis

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Results

Speed

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Accuracy

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Reader Confidence

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Table 1

Distribution of Confidence Scores for 43 Participants Across 12 Trials

Confidence Score Coronal Plane Axial Plane Target Present No Target Target Present No Target 1 29 12 28 13 2 42 17 34 23 3 25 29 40 24 4 42 22 33 20 5 34 6 37 6

No differences found to be significant (all P > .05).

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Interrater Agreement

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Discussion

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Study Limitations

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Implications

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Conclusions

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Acknowledgments

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