High Dynamic Range Images as a Basis for Detection of Argyrophilic Nucleolar Organizer Regions Under Varying Stain Intensities

Abstract

Silver staining of cytopathologic specimens offers advantages in cancer diagnostics. A difficulty with such stained cell specimens is the very high dynamic range needed by the imaging system to appropriately cover the varying stain intensities. Beside those images of cell nuclei that can be used for the diagnostic interpretation, there are nuclei that appear too dark to observe their relevant properties, the so-called argyrophilic nucleolar organizer regions (AgNORs), which appear as spot-like areas darker than their immediate surroundings. We therefore show how high dynamic range images of nuclei can help to correctly segment the AgNORs. To this end, we acquire a sequence of differently exposed images, which are then combined into a high dynamic range image. Based on the dynamic range of the image signal within the segmented cell area, we compute another image which provides optimal contrast over this area of interest. To further increase the contrast for dark objects, a suitable nonlinear point transform is simultaneously applied. We provide examples of the thus generated images and their corresponding segmentations.

Toward a multimodal cell analysis of brush biopsies for the early detection of oral cancer

“…A considerable improvement in the diagnostic performance of AgNOR analysis is expected from a novel, automatic AgNOR segmentation process, which not only counts but also will yield area measurements of AgNORs. This new procedure makes use of high‐dynamic‐range images 23…”

“…We applied the MMCA process to smears from oral brush biopsies, combining conventional cytology with the more quantifiable DNA content, followed by a count of argyrophilic nucleolar organizing regions (AgNORs) to identify early malignant transformation 14‐20. Recent studies have demonstrated that the number and/or size of AgNORs correlate with the ribosomal gene activity and, therefore, with cellular proliferation and consequent malignant potential 21‐24…”

Multispectral high dynamic range imaging

“…An alternative weighting function is the derivative of the CTF f (), 1, 13 which is similar to our weighting function. However, since our CTF is rather linear, the critical border areas would have a too strong influence and so we use the more stringent weighting function in (13) instead.…”

Segmentation and Detection of Nuclei in Silver Stained Cell Specimens for Early Cancer Diagnosis

“…of the group g i , the covariance matrix C C = 1 μ 00 μ 20 μ 11 μ 11 μ 02 (5) and the corresponding larger eigenvalue λ 1 and eigenvector v 1 , with C · v 1 = λ 1 · v 1 , can be calculated. This then allows to estimate the orientation of an elliptic approximation for g i by…”

“…In previous work we have developed methods to automatically analyze AgNORs [5,6]. This analysis in turn requires that the nuclei have to be segmented and detected within the microscopy images first.…”