On the Benefit of Dual-domain Denoising in a Self-supervised Low-dose CT Setting

Computed tomography (CT) is routinely used for three-dimensional non-invasive imaging. Numerous data-driven image denoising algorithms were proposed to restore image quality in low-dose acquisitions. However, considerably less research investigates methods already intervening in the raw detector data due to limited access to suitable projection data or correct reconstruction algorithms. In this work, we present an end-to-end trainable CT reconstruction pipeline that contains denoising operators in both the projection and the image domain and that are optimized simultaneously without requiring ground-truth high-dose CT data. Our experiments demonstrate that including an additional projection denoising operator improved the overall denoising performance by 82.4-94.1%/12.5-41.7% (PSNR/SSIM) on abdomen CT and 1.5-2.9%/0.4-0.5% (PSNR/SSIM) on XRM data relative to the low-dose baseline. We make our entire helical CT reconstruction framework publicly available that contains a raw projection rebinning step to render helical projection data suitable for differentiable fan-beam reconstruction operators and end-to-end learning.Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Noise2Contrast: Multi-Contrast Fusion Enables Self-Supervised Tomographic Image Denoising

Self-supervised image denoising techniques emerged as convenient methods that allow training denoising models without requiring ground-truth noise-free data. Existing methods usually optimize loss metrics that are calculated from multiple noisy realizations of similar images, e.g., from neighboring tomographic slices. However, those approaches fail to utilize the multiple contrasts that are routinely acquired in medical imaging modalities like MRI or dual-energy CT. In this work, we propose the new self-supervised training scheme Noise2Contrast that combines information from multiple measured image contrasts to train a denoising model. We stack denoising with domain-transfer operators to utilize the independent noise realizations of different image contrasts to derive a self-supervised loss. The trained denoising operator achieves convincing quantitative and qualitative results, outperforming state-of-the-art self-supervised methods by 4.7-11.0%/4.8-7.3% (PSNR/SSIM) on brain MRI data and by 43.6-50.5%/57.1-77.1% (PSNR/SSIM) on dual-energy CT X-ray microscopy data with respect to the noisy baseline. Our experiments on different real measured data sets indicate that Noise2Contrast training generalizes to other multi-contrast imaging modalities

MUDs - Ergänzung oder Ersatz traditioneller Bindungen bei jungen Erwachsenen?

Zusammenfassung. In der Diskussion über die Auswirkungen der Partizipation an virtuellen Gemeinschaften haben sich zwei entgegengesetzte, empirisch jedoch jeweils kaum überprüfte, Positionen herauskristallisiert, die man grob als die kulturpessimistische und die kulturoptimistische bezeichnen kann. Beide postulieren Auswirkungen auf politisches und gesellschaftliches Engagement, Bedeutung der Region und Wertorientierung. Diese Studie vergleicht Mitglieder eines Typs virtueller Gemeinschaften (multi-user-dungeons, MUDs) mit einer bezüglich soziodemografischer Charakteristika parallelisierten Stichprobe von Personen ohne Erfahrung mit virtuellen Gemeinschaften. Innerhalb der Gruppe der MUDder wurde geprüft, ob sich Unterschiede zwischen niedrig und hoch mit der virtuellen Gemeinschaft Identifizierten ergeben. Aus den Ergebnissen wird deutlich, dass virtuelle Gemeinschaften dem Trend zur Individualisierung und freien Wählbarkeit von Bindungen entgegenkommen. Das gesellschaftliche Engagement selbst der hoch identifizierten MUDder lässt nicht nach. Die Generalisierbarkeit der Ergebnisse auf andere virtuelle Gemeinschaften wird diskutiert

Effects of passion for massively multiplayer online role-playing games on interpersonal relationships

Game research suffers from using a variety of concepts to predict the (often negative) effects of playing games. These concepts often overlap (e.g., addiction or pathological gaming), include negative consequences in their definition, or are very game-specific (e.g., collective play). We argue that the field would benefit from using concepts that are well-established in other domains. Extending earlier work to the interpersonal domain, we examined the effects of obsessive and harmonious passion for massively multiplayer online role-playing games (MMORPGs) on the number and quality of online and offline friendships. Obsessive passion describes an irrepressible urge to engage in an activity, whereas harmonious passion describes the voluntary engagement in an activity. In an online survey of 406 MMORPG players, we found differential relationships between obsessive and harmonious passion and the number and quality of online and offline friendships. The results confirmed the usefulness of the dualistic model of passion for consequences of online gaming

Internet use and online social support among same sex attracted individuals of different ages

The current research addressed age differences in internet use among Same Sex Attracted (SSA) individuals. In general, online communities are found to be a source of social support, especially for minority group members. However, it is unclear whether younger and older SSA people differ in their use of these communities. The present research examined age differences in use of online communities, hypothesizing that young SSA people primarily use these for social interaction and support, whereas older SSA people use online communities to seek sexual contacts. Study 1 examined age differences in motives to start using these websites. Study 2 examined age differences in use of online profiles and online social support. Results of both studies confirmed our hypotheses. Younger compared to older SSA people are found to receive more online social support, whereas older SSA use the internet more for sexual purposes. Our findings provide first time evidence of the relation between sexual orientation, age and internet use

Effects of macroconsumers on benthic communities: Rapid increases in dry-season accrual of calcium in a tropical karst stream.

Species loss from upper trophic levels can result in some major changes in community structure and ecosystem functions. Here, we experimentally excluded macroconsumers (e.g., fish and shrimp) in a Brazilian karst tropical stream during the dry season to investigate if their loss affected the accrual of calcium, dry mass (DM) and ash-free dry mass (AFDM) of sediment, benthic invertebrates, and chlorophyll-a. We found that the exclusion of macroconsumers decreased accrual of calcium. The absence of fish and shrimp may have promoted increased grazing by mayflies and snails in the electrified treatment as expressed by the depressed calcium accrual and shift in periphyton community composition. However, the exclusion of macroconsumers had no effect on DM and AFDM, chlorophyll-a, or total abundance of invertebrates. Our findings shed new light on the impact of macroconsumer loss and consequences for calcium accrual in karstic streams