Denoising diffusion-based MR to CT image translation enables whole spine vertebral segmentation in 2D and 3D without manual annotations

Background: Automated segmentation of spinal MR images plays a vital role both scientifically and clinically. However, accurately delineating posterior spine structures presents challenges. Methods: This retrospective study, approved by the ethical committee, involved translating T1w and T2w MR image series into CT images in a total of n=263 pairs of CT/MR series. Landmark-based registration was performed to align image pairs. We compared 2D paired (Pix2Pix, denoising diffusion implicit models (DDIM) image mode, DDIM noise mode) and unpaired (contrastive unpaired translation, SynDiff) image-to-image translation using "peak signal to noise ratio" (PSNR) as quality measure. A publicly available segmentation network segmented the synthesized CT datasets, and Dice scores were evaluated on in-house test sets and the "MRSpineSeg Challenge" volumes. The 2D findings were extended to 3D Pix2Pix and DDIM. Results: 2D paired methods and SynDiff exhibited similar translation performance and Dice scores on paired data. DDIM image mode achieved the highest image quality. SynDiff, Pix2Pix, and DDIM image mode demonstrated similar Dice scores (0.77). For craniocaudal axis rotations, at least two landmarks per vertebra were required for registration. The 3D translation outperformed the 2D approach, resulting in improved Dice scores (0.80) and anatomically accurate segmentations in a higher resolution than the original MR image. Conclusion: Two landmarks per vertebra registration enabled paired image-to-image translation from MR to CT and outperformed all unpaired approaches. The 3D techniques provided anatomically correct segmentations, avoiding underprediction of small structures like the spinous process.Comment: 35 pages, 7 figures, Code and a model weights available https://doi.org/10.5281/zenodo.8221159 and https://doi.org/10.5281/zenodo.819869

KI-Modelle in den Sozialwissenschaften: logische Struktur und wissensbasierte Systeme von Balancetheorien

Gegenstand der Untersuchung ist die Anwendung nicht-numerischer, wissensbasierter Verfahren der Künstlichen Intelligenz (KI) auf die Modellierung sozialwissenschaftlicher Theorien. Ziel ist es zu zeigen, daß der Einsatz von KI-Programmen eine fruchtbare methodische Erweiterung für die Sozialwissenschaften darstellt. Die wissensbasierte Modellierung erfolgt auf dem Hintergrund logisch rekonstruierter Theorien im Rahmen eines neueren wissenschaftstheoretischen Ansatzes, der strukturalistischen Theorienkonzeption. In einem ersten Teil werden Grundlagen der Computermodellierung, Wissensverarbeitung und Wissenschaftstheorie behandelt. Auf dieser Basis wird in einem zweiten Teil die wissensbasierte Modellierung von Theorien erörtert. Dies geschieht am Beispiel von Heiders Balancetheorie in ihrer von Abelson und Rosenberg verallgemeinerten Form. In der Weiterentwicklung der Balancetheorien stehen vor allem graphentheoretische Überlegungen im Vordergrund. Abschließend fragt der Verfasser nach dem wissenschaftstheoretischen Status der dargestellten Balancetheorien, wobei vor allem intertheoretische Relationen sowie die Evolution der Gleichgewichtstheorien im Vordergrund stehen. (ICE2

De-Gendering informatischer Artefakte: Grundlagen einer kritisch-feministischen Technikgestaltung

Gender studies in computer science was only recently established at German universities. This research area is often understood as either addressing the problem of getting more women into IT professions or focussing on alleged gender differences in the design and use of IT. In contrast, the main objective of this dissertation is to identify and systemize gendering processes in products, theories, methods and assumptions of computer science (i.e. computational artifacts), in order to propose technology design methods, which aim at de-gendering these artefacts. The thesis focuses on three topics of inquiry: 1. Theoretical foundation: How can gendering and de-gendering processes of computational artifacts be theorized? 2. Practices of gendering: What are dimensions and mechanisms of gendering computational computational artifacts? 3. Methodological concepts for de-gendering: How can computational artefacts be designed, which can be characterized as de-gendered technologie