Remote Interpretation of Whole Slide Imaging
The term telepathology was coined three decades ago by Dr. Ronald Weinstein to describe the delivery of pathology services over a distance. A more current definition would specifically refer to making use of the internet to link a pathologist to a glass slide.
Telepathology involves digitizing histological or macroscopic images and transmitting them along telecommunication pathways for diagnosis or consultation. It can also be useful for continuing medical education. Over the past few decades the concept of visualizing and interpreting surgical pathology cases and frozen sections from remote locations has encompassed a range of technological tools, including video telemicroscopy, transmission of selected static images, use of a robotic microscope, and high-resolution scanners with images viewed over the internet.
Robotic microscopy tends to be much slower than light microscopy, requiring patience on the part of the pathologist to render an accurate diagnosis. Effective communication and planning is required at several levels in order for a telepathology frozen section program to function smoothly.
Whole Slide Imaging Compared to Light Microscopy
The Cleveland Clinic system includes a dozen regional affiliated hospitals and ambulatory surgery centers, prompting them to incorporate a whole slide imaging service which could providing surgical pathology consultations. As required by the College of American Pathologist recommendations, the clinic went through a revalidation process to verify that whole slide imaging yielded comparable results to the microscopic slide system previously employed. They found a diagnostic concordance rate of 98.6% when only major discrepancies were included (one major),and a concordance rate of 97.1% (one major and one minor) when both major and minor discrepancies were included.
Although the Cleveland Clinic noticed that whole slide imaging took longer to review than a microscope slides, they anticipated that efficiency would improve with additional experience. They found screening lymph nodes in search of metastatic carcinoma and viewing the peri-prosthetic fibrous tissue to rule out acute inflammation to be especially time-consuming.
On the other hand, they found that using annotation tools to measure distances made it easier and faster to judge the depth of invasion as compared to the use of a microscope alone. They were able to save time by directing dissection and viewing the frozen sections from the pathologist’s office instead of having to walk to and from the frozen section area near the operating room, which was often in another building. Overall, they concluded that digital pathology could balance out the extra time needed for interpretation.
High-resolution scanners can capture images of microscope slides for remote interpretation. The imaging technology used for telepathology has evolved significantly from low-resolution videotelemicroscopy to include static microscopy involving the transmission of selected images and dynamic robotic microscopy. Whole slide imaging has now advanced to the point where it is comparable to evaluation performed by light microscopy at different magnifications.
A solo pathologist is often called on to provide diagnostic services without the support of immediate second or expert consultation during an intraoperative consultation. The U.S. Army Medical Department developed a system of real-time, dynamic remote control of a robotic microscope over standard Internet connections. The use of telepathology is attractive because it provides an opportunity for pathologists to obtain immediate consultation.
Virtual Slide Imaging for Telepathology
The development of virtual slide technology represents a marked advance in the remote assessment of histologic slides. University Hospital Network (Toronto, Ontario, Canada) decided to implement telepathology in order to improve the efficiency of pathologists working in a multisite teaching hospital. They found that the ability of a virtual slide system to obtain rapid consultation on challenging cases gave it an advantage over light microscopy.
Telepathology can provide an alternative to having on-site pathology services for rural and regional hospitals. Telepathology diagnosis of parathyroidectomy frozen sections through small-footprint desktop systems has been shown to be accurate, reliable, and comparable with in-house direct microscopy. Compact desktop systems can be a cost-effective way to provide remotely controlled imaging.
University Hospital found that travel time and scheduling could extend the time for frozen section analysis by two hours. Using virtual slide technology for primary frozen section diagnosis has allowed the hospital system to provide an essential service while removing the disruptions in daily workflow.