Jackie Cuda, BS, SCT(ASCP)CM
Walid E. Khalbuss, MD, PhD
Digital images are increasingly being used in the field of cytopathology for telecytology, E-education, clinical consultation, Web-based learning, quality assurance, and secondary applications such as image analysis. Whole-slide imaging (WSI) is a digital imaging modality that uses computerized technology to scan and convert pathology and cytology glass slides into digital images (digital slides) that can be viewed on a computer using viewing software. Viewing the digital images mimics that which is done with a light microscope, which allows a user to scan from field to field and increase or decrease (zoom in/out) the magnification. Therefore, this is also known as “virtual microscopy.” Virtual microscopy is defined as the simulation of microscopy on a computer monitor without the need for a microscope.
As with any cytologic slide, the screener is responsible for every cell that is present on an imaged slide. Whole-slide imaging is a new technology for many cytotechnologists. The first challenge the user must overcome is establishing a technique for systematically reviewing the entire imaged slide and dotting selected abnormal or significant findings. This can be done in a number of ways:
- Auto panning (Fig. 1) is a convenient feature. By right clicking anywhere on the image, one can choose the auto pan feature. Once selected, two triangles will appear; one is a negative image, as seen in the picture, and the other will be a solid image. The distance and direction the solid triangle is moved from the negative image determines the speed with which the slide will be reviewed and the direction in which it will be reviewed.
- Another navigational method involves moving the cursor to any edge of the image. This will cause a directional arrow to appear (Fig. 2). Once the arrow is visible, pressing and holding the right mouse button will move the image in the direction of the arrow. Additionally, users can simply drag and pull the image using the mouse.
- The most systematic navigational option requires the use of the keyboard. Holding the “shift” key along with any directional arrow will advance the image one tile, or field of view (Fig. 3).
Once the user has developed a method of navigating through the slide, the tracking feature will help the user verify coverage of the entire digital slide.
A valuable feature of Aperio ImageScope software is its tracker capabilities (Fig. 4). This feature allows reviewers to feel confident they have covered all areas of the slide. It can also be useful for quality assurance purposes because it provides a permanent record of what areas of the slide were viewed. To use the tracking feature, open Aperio ImageScope and then choose the tracker option under the “view” menu. This will bring up the tracker tool. At this point, users can open an imaged slide, hit the record button on the tracker tool, and begin recording their movements on the slide. Using the thumbnail in the upper-right-hand corner of the slide, users can watch the areas they have covered turn from grey to white. The intensity of the white coloring is proportional to the magnification at which an area was screened. The higher the magnification at which an area is screened, the brighter white the track will be. The track can be saved at any point during screening. These tracks are saved under the annotations tab. For interrupted screening, these tracks are a tool to help users pick up where they left off. Once a track is completed, it can be saved for future review purposes.
Whole-slide imaging allows for annotations/dotting to be made and saved with an image. An unlimited number of annotations can be used in a variety of colors (Fig. 5). From the toolbar, the user can select a number of marking tools: the rectangle tool, ellipse tool, an arrow tool, or a freehand pen tool. Once an area has been marked, text can be added under the annotations tab to describe what exactly is being marked. This is a valuable tool for screeners to use to communicate findings to final reviewers. It can also be used as an educational tool. After annotations are made, they can be hidden, to be revealed only after a case has been screened. The layers (annotations) are saved in a small file called XML that can be hidden. This provides teachers with a built-in testing mechanism.
Simultaneous slide review is another interesting feature of ImageScope software. This function allows the user to simultaneously open two or more cases. This is particularly useful when one wants to display multiple features of an entity side by side; for example, the intracytoplasmic vacuoles and pigmented cytoplasm characteristic of malignant melanoma. This feature is also useful for reviewing histology (H&E slide) with cytology (cytology-histology correlation) or immunohistochemical stain slide. Additionally, this feature allows users to compare benign versus malignant entities simultaneously, and squamous versus glandular lesions for teaching purposes (Fig. 6). To use this feature, the user simply needs to open the cases of interest and select tile horizontal or vertical under the “windows” tab. This will open both cases side by side, at which point they can be reviewed independently or synchronously. To view the cases synchronously, the user needs to establish a starting point on each case and then click the “manual synchronize” tab on the toolbar. Once this feature is activated, any navigational movement or changes in magnification will be applied to both images.