Smartphone-based multimodal tethered capsule endoscopic platform for white-light, narrow-band, and fluorescence/autofluorescence imaging.

Multimodal low-cost endoscopy is highly desirable in poor resource settings such as in developing nations. In this work, we developed a smartphone-based low-cost, reusable tethered capsule endoscopic platform that allows white-light, narrowband, and fluorescence/autofluorescence imaging of the esophagus. The ex-vivo studies of swine esophagus were performed and compared with a commercial endoscope to test the white-light imaging capabilities of the endoscope. The efficacy of the capsule for narrow-band imaging was tested by imaging the vascularization of the tongue. To determine the autofluorescence/fluorescence capability of the endoscope, fluorescein dye with different concentrations was imaged. Furthermore, swine esophagus injected with fluorescein dye was imaged using the fluorescence/autofluorescence and the white-light imaging modules, ex-vivo. The overall cost of the capsules is approximately 12 €, 15 €, and 42 € for the white light imaging, the narrow-band imaging, and the fluorescence/autofluorescence imaging respectively. In addition, the cost of the laser source module required for the narrow-band imaging and the fluorescence/autofluorescence imaging is approximately 218 €. This device will open the possibility of imaging the esophagus in underprivileged areas.

Novel input polarisation independent endoscopic cross-polarised optical coherence tomography probe.

Lead by the original idea to perform noninvasive optical biopsies of various tissues, optical coherence tomography found numerous medical applications within the last two decades. The interference based imaging technique opens the possibility to visualise subcellular morphology up to an imaging depth of 3 mm and up to micron level axial and lateral resolution. The birefringence properties of the tissue are visualised with enhanced contrast using polarisation sensitive or cross-polarised optical coherence tomography (OCT) techniques. Although, it requires strict control over the polarisation states, resulting in several polarisation controlling elements. In this work, we propose a novel input-polarisation independent endoscopic system based on cross-polarised OCT. We tested the feasibility of our approach by measuring the polarisation change from a quarter-wave plate for different rotational angles. Further performance tests reveal a lateral resolution of 30 µm and a sensitivity of 103 dB. Images of the human nail bed and cow muscle tissue demonstrate the potential of the system to measure structural and birefringence properties of the tissue endoscopically.

Input polarization-independent polarization-sensitive optical coherence tomography using a depolarizer.

Polarization-sensitive optical coherence tomography is gaining attention because of its ability to diagnose certain pathological conditions at an early stage. The majority of polarization-sensitive optical coherence tomography systems require a polarization controller and a polarizer to obtain the optimal polarization state of the light at the sample. Such systems are prone to misalignment since any movement of the optical fiber normally coupled to the light source will change the polarization state of the incident beam. We propose and demonstrate an input polarization-independent polarization-sensitive optical coherence tomography system using a depolarizer that works for any input polarization state of the light source. The change in the optical power at the sample for arbitrary input polarized light for the standard polarization-sensitive optical coherence tomography system was found to be approximately 84% compared to 9% for our proposed method. The developed system was used to measure the retardance and optical axis orientation of a quarter-wave plate and the obtained values matched closely to the expectation. To further demonstrate the capability of measuring the birefringent properties of biological samples, we also imaged the nail bed. We believe that the proposed system is a robust polarization-sensitive optical coherence tomography system and that it will improve the diagnostic capabilities in clinical settings.

Bono Bo and Fla Mingo: Reflections of Speech Prosody in German Second Graders' Writing to Dictation.

Written German is characterized by an underrepresentation of prosody. During writing acquisition, children have to tackle the question which prosodic features are realized by what means - if any. We examined traces of speech prosody in German children's writing to dictation. A sample of 79 second graders were asked to write down eight sentences to dictation. We analyzed three potential reflections of speech prosody in children's dictations: (a) Merging of preposition and definite article, potentially preferred after monosyllabic prepositions as in this case preposition and article may melt to the canonical trochaic foot in German. (b) The introduction of orthographically inadequate graphemic border markings within trisyllabic animal names, respecting borders of prosodic units like foot or syllable. (c) Omissions of the definite article in non-optimal prosodic positions, deviating from the preferred strong-weak rhythm. The occurrence of border markings was evaluated via graded perceptual judgments. We found no evidence for inter-word border markings being influenced by prosodic context, probably due to a ceiling effect. However, word-internal markings within animal names, although rarely occurring in general, were clearly influenced by prosodic structure: Most of them were produced at borders of feet or syllables, while significantly fewer markings were perceived at borders of syllable constituents or within consonant clusters. Moreover, we observed significantly more omissions of the definite article in non-optimal prosodic positions compared to potentially optimal positions. Thus, our results provide first evidence from writing acquisition for prosodic influences on writing in a language with scarce graphemic marking of prosody.