Three-dimensional cascaded system analysis of a 50 µm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis.

High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 µm pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30°. The cascaded system model was extended to the 3D spatial frequency space in combination with the filtered back-projection (FBP) reconstruction method to calculate the 3D and in-plane MTF, NNPS and DQE parameters. The results demonstrate that the beam obliquity blurs the 2D MTF and DQE in the high spatial frequency range. However, this effect can be eliminated after FBP image reconstruction. In addition, impacts of the image acquisition geometry and detector parameters were evaluated using the 3D cascaded system analysis for DBT. The result shows that a wider projection angle range (e.g. ±30°) improves the low spatial frequency (below 5 mm-1) performance of the CMOS APS detector. In addition, to maintain a high spatial resolution for DBT, a focal spot size of smaller than 0.3 mm should be used. Theoretical analysis suggests that a pixelated scintillator in combination with the 50 µm pixel pitch CMOS APS detector could further improve the 3D image resolution. Finally, the 3D imaging performance of the CMOS APS and an indirect amorphous silicon (a-Si:H) thin-film transistor (TFT) passive pixel sensor (PPS) detector was simulated and compared.

[Seasonal affective depression in 2 German speaking university centers: Bonn, Vienna. Clinical and demographic characteristics]. / Saisonal abhängige Depression in zwei deutschsprachigen Universitätszentren: Bonn, Wien. Klinische und demographische Charakteristika.

Six hundred ten patients with seasonal affective disorder (SAD) were diagnosed and treated at the university hospitals for psychiatry in Bonn, Germany (1989-1992) and Vienna, Austria (1993-2001). The aim of this study was to compare our sample with other SAD populations in the literature and to investigate differences between the two study locations. We found female:male sex ratios of 5.0:1.0 in unipolar depressives and 1.5:1.0 in patients with bipolar affective disorder. Of our patients, 21.7% suffered from bipolar II disorder, and 1.3% were diagnosed as having bipolar I. Our patients obtained a mean global seasonality score (GSS) of 15.4. Women had a higher GSS than men (t = 2.127, P = 0.035), and Viennese patients had higher scores than patients in Bonn (t = 3.104, P = 0.002). Totals of 66.3% of all patients suffered from atypical depression and 17.8% from melancholic depression. Patients with atypical depression were more frequent in Vienna, whereas patients with melancholic depression predominated in Bonn (chi 2 = 54.952, df = 2, P < 0.001). The demographic and clinical characteristics of the patients described in this article confirm the findings of other epidemiological investigations obtained in non-German-speaking samples.

Changes of clinical pattern in seasonal affective disorder (SAD) over time in a German-speaking sample.

OBJECTIVE: The goals of this study are to provide estimates of clinical and demographic variables of patients with seasonal affective disorder (SAD) in Germany and Austria, to compare our results with those of previously published SAD studies, and to find out whether the clinical pattern of SAD remained stable over several years. METHOD: We investigated 610 SAD patients from the outpatient clinics in Bonn (n = 190) and Vienna (n = 420). Patients in Bonn were recruited in the fall-winter season of the years 1989-1992, those in Vienna in the years 1993-2001. RESULTS: We observed a change in the clinical pattern in our patients: patients from Bonn, who were diagnosed and treated about 5 years earlier, were more likely to suffer from melancholic depression, whereas Viennese patients rather suffered from atypical depression (chi(2) = 54.952, df = 2, p < 0.001). The symptoms of hypersomnia, daytime fatigue, increased eating and carbohydrate-craving were more frequent in the Viennese sample, anxiety and deterioration of patients' capacity to perform at work predominated in Bonn. In addition, patients from Vienna obtained a higher GSS (global seasonality score, measured by the SPAQ - Seasonal Pattern Assessment Questionnaire) than those from Bonn (15.7 +/- 3.3 and 14.6 +/- 4.1 respectively; t = 3.104, p = 0.002). Taken together, our results were in good accordance to other published SAD materials, but we were able to demonstrate that our patients reported "feeling worst" (measured by item 13H of the SPAQ) in November and December, whereas SAD patients in the USA clearly had their worst months in January and February. CONCLUSIONS: We suggest that an increase in awareness of fall-winter depression in the last decade by both doctors, who referred patients, as well as patients or the entire population must have caused patients to sign up for light therapy at the Viennese SAD clinic because of having heard about the atypical symptom profile. This increased awareness of SAD can also be measured by a statistically significant reduction in the diagnostic latency (from the age of onset to the diagnosis of SAD) when comparing the two study locations.

Monoaminergic function in the pathogenesis of seasonal affective disorder.

Seasonal affective disorder/winter type (SAD) is characterized by recurrent depressive episodes during autumn and winter alternating with non-depressive episodes during spring and summer. Light therapy with full-spectrum, bright white light has been shown to be effective for this condition. Several hypotheses have been discussed in the literature about the pathogenesis of SAD. The most prominent includes disturbances in central monoaminergic transmission. Evidence can be inferred from studies showing a seasonal rhythm of central and peripheral serotonergic functioning which may be a predisposing factor for SAD. Some of the symptoms of SAD are believed to represent an attempt to overcome a putative deficit in brain serotonergic transmission. Moreover, 5-HT receptor challenge studies suggest altered activity at or downstream to central 5-HT receptors. Monoamine depletion studies support hypotheses about serotonergic and catecholaminergic dysfunctions in SAD and suggest that light therapy may well compensate for this underlying deficit. Further, albeit indirect, support for the importance of monoaminergic mechanisms in SAD and its involvement in the mechanism of the action of light therapy comes from studies showing antidepressant efficacy of serotonergic and noradrenergic antidepressants in the treatment of SAD. Altogether, disturbances in brain monoaminergic transmission seem to play a key role in the pathogenesis of SAD; monoaminergic systems may also play an important role in the mechanisms of the action of light therapy.

Artificial secondary caries around two new F-containing restoratives.

Replacement of restorations due to secondary caries is a continuing problem in restorative dentistry. This investigation evaluated the ability of two new light-cured fluoride-containing restorative materials to inhibit caries in vitro. Class 5 cavities were prepared in buccal and lingual surfaces of 20 extracted premolars. The occlusal cavosurface margin of each preparation was on enamel and the gingival cavosurface margin was on root surface. The four materials used were: glass-ionomer cement (Fuji II), composite resin (Silux Plus), light-cured glass ionomer (Vitremer), and compomer (Dyract). After 5 weeks in an acid gel for caries-like lesion formation, the teeth were sectioned longitudinally and examined with polarized light. The results showed that use of a light-cured glass ionomer and/or compomer may prevent both secondary caries around restorations and primary caries in surface enamel adjacent to the restorations.