Peter Schwarzmann

The false negative rate in cervical cytology. Comparison of monolayers to conventional smears.

OBJECTIVE To compare cervical monolayers prepared by a density gradient technique to conventional smears. STUDY DESIGN The study evaluated 2,863 patient samples. After conventional smears were prepared, the residual samples (collected in preservative fluid) were processed by the monolayer preparation system, which disaggregates the cells, removes nonclinical debris and layers the diagnostic material onto a microscopic slide. Slides were screened in Germany and the United States in masked studies. RESULTS In the U.S. study, the false negative rate for the conventional smears was 9.4% when endocervical components were present and 16.7% when absent. The false negative rate for the monolayer preparation was 4.0% when endocervical components were present and 5.7% when absent. A comparison of the diagnostic results showed that the monolayer made possible the detection of 48 cases of low grade disease or higher that were not found on the conventional smear. The German study was independent but used the same samples. The results, although based upon the Papanicolaou classification, were similar. CONCLUSION Cervical samples that are preserved in a liquid suspension and prepared using the density gradient monolayer technology have many advantages over conventional cervical cytologic smear preparations. The quality of cell preservation and presentation is superior. Elimination of obscuring material, homogeneity of the sample and standardized quality work together to produce preparations that can be effectively and reliably screened by cytotechnologists. These preparations should greatly enhance the reliability of machine-based screening in the future.

The validity of telepathological frozen section diagnosis with ISDN-mediated remote microscopy.

Abstract We investigated 109 randomly selected frozen section specimens from lung surgery patients in a retrospective blind mode using telepathology equipment. The telepathology system applied (HISTKOM) used one ISDN B-channel and telemicroscopy with a remotely operated robotic microscope. The performance of telepathological frozen section diagnosis was compared with that of conventional frozen section diagnosis. The false-positive rate achieved was identical for both methods. The sensitivity (P=0.03), but not the specificity, was significantly lower for the telepathological method. The time needed to establish a diagnosis with the remote microscope was too high; therefore, upgrading to multichannel technology is recommended. The quality of the images transmitted was judged to be sufficient by the pathologists involved in the study. In conclusion, with further technical improvements in telemicroscopy and additional experience in telepathology, remote diagnosis seems to be feasible.

Reliability of Telepathology for Frozen Section Service

One of the most promising applications of telepathology (pathology at a distance by electronic transmission of images in pathology) is frozen section diagnosis, especially because by means of this tool operations requiring an intraoperative histopathological diagnosis are feasible at hospitals without a pathologist on‐site. For the introduction of this diagnostic tool into pathologists daily practice the evidence of its diagnostic accuracy comparable to that of the conventional frozen section diagnosis is crucial. For this purpose the literature on the diagnostic accuracy of telepathological frozen section diagnosis was reviewed. In a metaanalysis these studies and reports, in which a total of more than 1290 cases had been examined, showed a slightly lower overall diagnostic accuracy (of the telepathological frozen section diagnosis) of about 0.91 than the conventional frozen section diagnosis with an average accuracy of about 0.98 found in an analysis of several studies (on frozen section diagnosis of different organs). This difference is at least predominantly caused by a higher rate of deferred and false negative frozen section diagnoses in the telepathological method, while the specificity of both methods, each more than 0.99 was not significantly different. In conclusion, the introduction of a telepathological frozen section diagnosis for hospitals without an acceptable access to a pathologist is justifiable already at the current state of the technological development especially when considering the advantages (time saving, reduction in costs) compared to the alternative of surgical interventions without access to an intraoperative diagnosis.

Image processing to overcome channel capacity limitations in telemicroscopy

Telemicroscopy is the central tool to establish a net for telepathology services. To operate such a net in an economical and general available manner the public phone net is selected as communication link. To overcome some of the limitations imposed by the small channel capacity of todays ISDN phone nets with respect to image transmission, an improved handling of the image data stream is mandatory. A flexible, variable and self adapting strategy to compress and reduce image data according to the activity of the operator is described. A further reduction of the data stream is achieved by an autofocus procedure avoiding the transmission of unfocused image data during the focusing process. The remote operator can orient himself in the slide by means of a macro-image with a telecursor to avoid unnecessary image transmission just for orientation. With the help of an intelligent management of the transmitted image data stream an online impression including the movement of the slide under the remote microscope can be provided. To meet legal requirements in medicine tools are provided to record the inspection process for later archiving and documentation in the patient record file.

Nonlinear approach to the 3-D reconstruction of microscopic objects

The 3-D reconstruction of light microscopic objects has been extensively investigated in the past, but fundamental problems remain. The real object under observation does not normally have high transparency, and light transmission will be attenuated introducing nonlinearities in the imaging process. A nonlinear approach to this problem has been developed. In this nonlinear approach the authors regard the 3-dimensional spatially resolved light absorption coefficient as the object information of interest. A nonlinear equation system modeling the imaging process is proposed.

Justierung von Bildpaaren ohne Verwendung von Paßpunkten

Es wird ein Verfahren vorgestellt, Bildpaare unterschiedlichen Inhalts nach Masgabe einer Paslage eines ahnlichen Musterbildpaares aufeinander zu justieren, ohne Paspunkte zu verwenden; es wird vielmehr der gesamte Bildinhalt zur Feststellung der Paslage herangezogen.

Paßpunktfreie Justierung von Bildern

Das Aufsuchen korrespondierender Bildteile in Bildpaaren ist von Bedeutung sowohl in der Objekterkennung, als auch bei der Justierung von Bildern gegenuber einer Musterlage. Wird eine solche Justierung uber Korrelationsverfahren vorgenommen, tragt der gesamte Bildbereich zum Ergebnis bei, wohingegen Paspunktverfahren sich nur auf sehr kleine Bildbereiche stutzen mussen.

Automatische Wolkenbildanalyse aus Satellitenbildern

Fur die automatische Bestimmung des Wolkenbedeckungsgrades aus Satellitenbildern wird ein Verfahren beschrieben, das Information aus spektralen Bildern(sichtbar und infrarot) verwendet. Zusatzlich werden durch Anwendung lokaler Operatoren strukturspezifische Elemente angehoben oder unterdruckt. Dadurch ist es moglich fur die Gebietsbestimmung der Wolkenfelder neben den spektralen auch strukturbeschreibende Merkmale zu verwenden.