Exploring Remote Images:
A Telepathology Workstation

Catherine Plaisant , David A. Carr and Hiroaki Hasegawa*

Human-Computer Interaction Laboratory
Center for Automation Research
University of Maryland
College Park, MD 20742
Tel. (301) 405-2768

* on visit from Sony Corp. Japan

Telemedicine is the practice of medicine over communication links. The physician being consulted and the patient are in two different locations. A first telepathology system has been developed by Corabi Telemetrics. It allows a pathologist to render a diagnosis by examining tissue samples or body fluids under a remotely located microscope.

Figure 1: Simplified diagram of a telepathology system.

Of course it would seem natural to digitize the entire specimen at the highest magnification and then leisurely explore the transmitted image. But this is not currently practical because the specimens are very high definition 3D color objects requiring too long to digitize and having impractical storage requirements. Therefore the specimen still needs today to be explored under a microscope.

The consulting pathologist sits at the receiving workstation, remotely manipulates the microscope and looks at the high resolution image of the magnified sample, transmitted via satellite, microwave or cable. A scanned low resolution global view of the whole slide is displayed on the control screen. A red rectangle indicates the position of the microscope stage which can be moved by dragging the rectangle. These actions can be handled with direct manipulation principles. Unfortunately, several limiting factors exists: time delays (about 1.5 seconds for transmission and activation of a command), inadequate position feedback, and increased probability of breakdown. Those factors lead us to the notion of remote direct manipulation [1]. We are exploring various interfaces and conducting experiments to determine which configuration will beneficially replace the existing interface. A satisfactory interface also has to let the pathologist manipulate the main controls while still looking at the high resolution image.

At first two prototypes were built on our simulator. A start-stop interface using a keypad (users specify a start command followed by a stop command), similar to the existing interface, and a proportional commands interface using a trackball (users specify movement commands incremental and directly proportional to the input device movement). We conducted a pilot study to determine the effect of time delays on performance using the two interfaces. The initial results [2] showed the benefits of the direct manipulation of the red rectangle on the global view when the time delays are very long but our trackball interface didnít seem to be helpful. On the other hand users comments suggested that providing more feedback would improve the performance. These improvements were made and the improved interface was tested in the same conditions. With the feedback improvement the trackball interface exhibited the best properties and was significantly faster for expert users.

A second experiment was performed to estimate the benefits of providing an intermediate local map for navigation at high magnification. Our experience shows that an intermediate view should be introduced when the ratio overview-to-detail is above 1:20. Certainly, by the time the ratio reaches 1:40 users have serious difficulties and the global overview is more of a hindrance than a help.

Current references:

1. Keil-Slawik et al. Remote direct manipulation: A case study of a telemedicine workstation. In Bullinger H.-J. (Ed.), Proc. of the 4th Int. Conf. on HCI, Stuttgart (Sept. 91). Amsterdam, Elsevier. pp. 1006-1011.

2. Carr, D., Hasegawa, H., Lemmon, D., Plaisant, C. The effects of time delays on a telepathology user interface, in Proc. of 16th AMIA SCAMC conference, Baltimore (Nov.92). New York, McGraw-Hill, Health Professions Division, pp. 256-260.


We appreciate the support of the State of Maryland MIPS program, Corabi Telemetric and the System Research Center of the University of Maryland.

ACM INTERCHI ë93 Conference Proc., (Amsterdam, Netherlands, April 24-29, 1993) 518, video available through SIGGRAPH Video Review, issue # 88-89.