Merits of usability testing for PACS selection.

Objectives: To compare the usability of different Picture Archiving and Communication System (PACS) workstations, determine whether a usability test has added value with respect to the traditional way of comparing PACSs based on functional requirements, and to evaluate the appropriateness of a task-based methodology for a PACS usability test.

Methods: A task-based usability test of four PACS workstations was performed. Radiologists' subjective responses to the PACSs and their performance on the tasks were measured. To mimic the traditional PACS selection process, two functional requirements were defined which the PACSs met in varying degrees. The focus of the usability test was on the aspects of the PACS related to these requirements. The usability results were compared to the PACSs' ability to meet the functional requirements.

Results: One PACS outperformed the other PACSs both in terms of subjective preference and task performance, indicating its superior usability. There were differences in usability between PACSs with identical functionality. Also, a PACS with theoretically advantageous functionality for a given task did not necessarily have better usability for this task than a PACS without this functionality. There was a discrepancy between participants' subjective preferences and their task performance, which indicates that it is vital to include performance measures in the usability assessment so that it accurately reflects the efficiency of interaction.

Conclusions: The differences in usability between PACSs with identical functionality indicate that functional requirements alone are insufficient to determine a PACS's overall quality. A usability test should therefore be used in addition to a functional requirement list in a PACS selection process to ensure that a hospital buys the PACS with the highest quality. A task-based usability evaluation methodology, which yields both subjective preference data and objective performance data of radiologists interacting with the PACS, is very suitable for such a usability test.