A method for quantitative analysis of clump thickness in cervical cytology slides

Abstract

A c c e p t e d M a n u s c r i p tWe developed an algorithm to estimate the thickness of cervical cytology specimens.The proposed algorithm reached an accuracy of 1 micron at 90% of times.The algorithm was used to quantitatively analysis of ten normal Thin-prep cervical cytology slides.It was found that the distribution of cells is skewed towards the cover-slip (top of the slide).It was also proved that considering the thickness of focal points produced focus maps in superior qualities compared to conventional ones. Highlights (for review)Page 2 of 28 A c c e p t e d M a n u s c r i p t AbstractKnowledge of the spatial distribution and thickness of cytology specimens is critical to the development of digital slide acquisition techniques that minimise both scan times and image file size. In this paper, we evaluate a novel method to achieve this goal utilising an exhaustive high-resolution scan, an over-complete wavelet transform across multi-focal planes and a clump segmentation of all cellular material on the slide. The method is demonstrated with a quantitative analysis of ten normal, but difficult to scan Pap stained, Thin-prep, cervical cytology slides. We show that with this method the top and bottom of the specimen can be estimated to an accuracy of 1 micron in 88% and 97% of the fields of view respectively. Overall, cellar material can be over 30 microns thick and the distribution of cells is skewed towards the cover-slip (top of the slide). However, the median clump thickness is 10 microns and only 31% of clumps contain more than three nuclei. Therefore, by finding a focal map of the specimen the number of 1 micron spaced focal planes that are required to be scanned to acquire 95% of the in-focus material can be reduced from 25.4 to 21.4 on average. In addition, we show that by considering the thickness of the specimen, an improved focal map can be produced which further reduces the required number of 1 micron spaced focal planes to 18.6. This has the potential to reduce scan times and raw image data by over 25%.

Why is digital pathology in cytopathology lagging behind surgical pathology?

“…Even with liquid-based samples in which monolayers are generated, cell clumping still occurs. 10 With the use of flat tissue sections in surgical pathology, there are fewer topographic variations, with the exception of occasional tissue folds. Hence, it is more important to be able to observe cytologic material in both horizontal (x and y) and vertical (z) axes.…”

“…However, this may not always be possible when cytology slides have thick smears and/or specimens contain 3‐dimensional cell groups. Even with liquid‐based samples in which monolayers are generated, cell clumping still occurs . With the use of flat tissue sections in surgical pathology, there are fewer topographic variations, with the exception of occasional tissue folds.…”

Current state of whole slide imaging use in cytopathology: Pros and pitfalls

“…However, the common characteristic of cytological preparation is a non-uniform 3D distribution of groups of cells, with the presence of cell clusters, that is maximal in manual smears and minimal but not negligible in LBC preparation. 5 Moreover, cytological specimens can contain obscuring material (eg, blood, mucus, inflammatory cells, ultrasound gel) not usually present in histology.…”

High throughput slanted scanning whole slide imaging system for digital pathology

“…In cytopathology, the accurate evaluation of a digital cytological slide requires that all of the cells present is viewable and in focus. According to previous studies, the median thickness of this type of specimen is 9 μm and 95% of cell clumps have a thickness of about 19 μm [4]. This means cytological specimens always contain 3D cell groups that cannot be viewed in a single focal plane [5].…”