DYNAMIC VS. STATIC-IMAGE TELEPATHOLOGY

Ronald S. Weinstein, M.D. Department of Pathology and Arizona Telemedicine Program, University of Arizona College of Medicine, Tucson, AZ.

Telepathology is the practice of pathology at a distance, viewing images on a video monitor rather than directly through a light microscope. The transmitted images may be used for primary diagnosis, consultation, quality assurance, proficiency testing, and distance learning.

Dynamic and static imaging have been described as competing technologies.(Table 1) In time, it is likely that both dynamic and static imaging will have roles in various telepathology applications. Furthermore, these technologies are not mutually exclusive. Some telepathology programs use equipment that integrates dynamic imaging, static imaging, and robotic microscopy into hybrid systems.

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Table 1 Comparison of Static and Dynamic Telepathology Systems^a

Static Imaging Robotic-Dynamic Imaging

_______________ ____________________

Image system still live

Robotic remote control no yes

Images per average case 5 unlimited

Image selection referring telepathologist

pathologist consultant

Transmission time/image 1 minute 1/15 second

Average time/diagnosis 15 minutes 3 to 10 minutes

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^a - Commonest configurations

The relative merits of dynamic-robotic and static-image telepathology have been debated. Some studies suggest that pathologists using dynamic-robotic telepathology, with or without static imaging, may achieve higher levels of diagnostic accuracy than those using static-image telepathology alone.

Feasibility and clinical studies

Diagnostic performance studies fall into two broad categories: feasibility studies and clinical studies. Feasibility studies are performed before telepathology practices begin operation. Validation studies use essentially the same protocol as feasibility studies but are used for the retrospective appraisal of the diagnostic accuracy of established telepathology practices. For feasibility and validation studies, sets of archival cases are assembled and examined by both telepathology (or video microscopy) and light microscopy by the same pathologists at separate diagnostic sessions. Clinical studies involve actual on-line telepathology practices.

Table 2 shows the results of studies on the diagnostic accuracy of dynamic and static-image telepathology. These studies indicate that field selection can be a significant problem with static-image telepathology and underline the importance of the referring pathologist in the static-image mode. Video image quality may be of lesser importance in either imaging mode. Errors of interpretation may be partially related to study design and case mix.

The reason why dynamic-robotic telepathology may outperform static-image telepathology is attributed, in part, to differences in video image acquisition methods. With dynamic-robotic telepathology, the teleconsultant serves as the telepathology system operator who controls all microscopy functions including stage movements. The telepathologist views sections on all glass slides in their entirety. This is in contrast to static-image telepathology in which the referring pathologist captures a small set of digital images which are then transmitted to the consultant who views them on a video

monitor. Static-image sampling is highly selective. Viewing a small set of video images on a monitor, the telepathologist can underestimate the complexity of some cases. Problems caused by inadequate or inappropriate selection of tissue fields for video imaging by the referring pathologist may account, in part, for the somewhat lower diagnostic accuracy rates associated with static-imaging telepathology.

Table 2 Surgical Pathology Diagnostic Error Rates

Reasons for Errors (%)

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Interpretation Image Field

Quality Selection

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Dynamic- 1.5 1.0 ----

robotic TP^a

Static- 7.5 3.0 5.0

image TP^b

Static- 9.0 ---- 6.3

image TP^c

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Abbreviations: TP = telepathology

a - feasibility study on routine surgical pathology cases.

(Dunn et al., Hum Pathol, in press)

b - validation study on routine surgical pathology cases.

(Weinberg et al., Hum Pathol 27: 111-118, 1996)

c - clinical study on consultation cases.

(Halliday et al., Hum Pathol, in press)