Dell's Axim PDA and Apple's iPod Touch hold up well against off-the-shelf monitors for reading some CT images, according to a paper in the February issue of American Journal of Roentgenology.

In the study, radiologists were just as good, and sometimes slightly better, at identifying wrist or brain injuries on CT slices using the handheld devices as they were with so-called secondary-class monitors.

This suggests handhelds might have a useful clinical role. Secondary-class monitors, off-the-shelf monitors that do not meet the more demanding specifications for primary diagnoses by radiologists, are common in many parts of the hospital, such as emergency rooms, according to Rachel Toomey, lead author of the study and a researcher at the University College Dublin School of Medicine in Dublin, Ireland. She notes treatment decisions are often based on them.

"For instance, clinicians in emergency departments, clinics and intensive care units might all view radiological images on standard, off-the-shelf displays," she tells DOTmed News by email.

HOW THE STUDY WAS DONE

In the study, conducted during American Board of Radiology examinations in Louisville, Kentucky, board-certified radiologists examined 30 CT wrist and 30 brain images, with about half the slices showing lesions. Forty-nine rads had to make "diagnoses" on the images on both PDA and monitors, while 35 rads had to use the iPod Touch and monitors.

The physicians' readings on handheld devices and monitors were almost equally accurate, with some rads using the Dell PDA slightly better at finding or ruling out lesions on the brain CT slices than with the monitors. No significant difference was found on readings between monitors and iPods in the trials.

Toomey doesn't know why some of the results were significantly better with the PDA and not the iPod, but she suspects it has something to do with the lighting of the screen and the better resolution of the PDA, at least on the initial view. Although radiologists could zoom in on images displayed on the iPod Touch, the first view is set at a lower resolution, and some doctors might have chosen not to enlarge the pictures.

IS SMALLER BETTER?

While no one knows for sure, some scientists have suggested that smaller images might actually improve diagnostic accuracy. And all for a curious reason: the fovea-to-image ratio.

Because our vision is sharpest for objects presented to a very small area, around the foveal region of the retina, showing the whole image on a smaller screen might allow more of it to fall on that region of the eye, thus giving viewers more spatial detail, Toomey explains.

"This might be particularly pertinent in the very early stages of viewing, as it has been shown that radiologists' visual search is influenced by their first global impression of an image," she tells DOTmed News.

Nonetheless, Toomey cautions that this idea is only a suggestion: so far, reports on image size in the literature have had mixed results, and more evidence is needed before most scientists would accept it as an explanation.

FUTURE STUDIES

Toomey hopes to continue the research on handheld devices and see if the findings apply to other diagnostic imaging exams.

She also wants to see how the products measure up when image processing bells and whistles are turned on. In the study, the researchers deactivated image manipulation features on the monitors, and pictures were viewed on the handheld devices' standard picture viewing software.

The study was also carried out before sophisticated medical imaging software became available for some portable systems.

"Some major developments have occurred in radiological image viewing on handheld devices since we collected our data," Toomey notes. "For example, Osirix is now available as an iPhone application, and permits a wide range of image processing."