Image Size Influences Visual Search and Perception of Hemorrhages When Reading Cranial CT: An Eye-Tracking Study.

OBJECTIVE: The aim of this study was to explore reader gaze, performance, and preference during interpretation of cranial computed tomography (cCT) in stack mode at two different sizes. BACKGROUND: Digital display of medical images allows for the manipulation of many imaging factors, like image size, by the radiologists, yet it is often not known what display parameters better suit human perception. METHOD: Twenty-one radiologists provided informed consent to be eye tracked while reading 20 cCT cases. Half of these cases were presented at a size of 14 × 14 cm (512 × 512 pixels), half at 28 × 28 cm (1,024 × 1,024 pixels). Visual search, performance, and preference for the two image sizes were assessed. RESULTS: When reading small images, significantly fewer, but longer, fixations were observed, and these fixations covered significantly more slices. Time to first fixation of true positive findings was faster in small images, but dwell time on true findings was longer. Readers made more false positive decisions in small images, but no overall difference in either jackknife alternative free-response receiver operating characteristic or reading time was found. CONCLUSION: Overall performance is not affected by image size. However, small-stack-mode cCT images may better support the use of motion perception and acquiring an overview, whereas large-stack-mode cCT images seem better suited for detailed analyses. APPLICATION: Subjective and eye-tracking data suggest that image size influences how images are searched and that different search strategies might be beneficial under different circumstances.

Review of prospects and challenges of eye tracking in volumetric imaging.

While eye tracking research in conventional radiography has flourished over the past decades, the number of eye tracking studies that looked at multislice images lags behind. A possible reason for the lack of studies in this area might be that the eye tracking methodology used in the context of conventional radiography cannot be applied one-on-one to volumetric imaging material. Challenges associated with eye tracking in volumetric imaging are particularly associated with the selection of stimulus material, the detection of events in the eye tracking data, the calculation of meaningful eye tracking parameters, and the reporting of abnormalities. However, all of these challenges can be addressed in the design of the experiment. If this is done, eye tracking studies using volumetric imaging material offer almost unlimited opportunity for perception research and are highly relevant as the number of volumetric images that are acquired and interpreted is rising.

Does preference influence performance when reading different sizes of cranial computed tomography?

Radiology practice is based on the implicit assumption that the preference for a particular presentation mode goes hand in hand with superior performance. The present experiment tests this assumption in what pertains to image size. Forty-three radiologists were asked to identify intracranial hemorrhages on 20 cranial computed tomography scans in two image sizes, [Formula: see text] and [Formula: see text]. They were asked to indicate which size they preferred and subsequently rated each size on a continuous scale in terms of how much they liked them. The results show no correlation between the jackknife free-response receiver operating characteristic figure of merit and preference rated on a continuous scale (large image: [Formula: see text], [Formula: see text]; small images: [Formula: see text], [Formula: see text]). Similarly, there was no significant correlation between the time a radiologist took to read a case and preference rated on the continuous scale (large image: [Formula: see text], [Formula: see text]; small images: [Formula: see text], [Formula: see text]). When dividing radiologists into two groups according to their size preference, there was no significant difference in performance between groups with regard to either large or small images. The results suggest that the preference for an image size and performance with regard to it are not related.