Towards Invisible Eye Tracking with Lens-Coupled Lateral Photodetectors

A novel low-power and easy to integrate sensing configuration for wearable eye tracking is presented. Within the context of infrared oculography based on individual photosensors, we proposed to couple a set of photodetectors to the lateral edges of a standard lens, acting as waveguide for the IR light, instead of directing them towards the eyeball. This allows to embed the detectors in the rim, thus being fully hidden in the eyewear, invisible to the user and robustly integrated with the glasses. A preliminary setup with four photodiodes whose signals are processed by an agile two-layer neural network was realized and characterized. Here we demonstrate both experimentally and by means of simulations the feasibility of this patent-pending approach. Detected maps of light patterns respond to different impinging light orientations. An angular resolution of about 5 degrees is achieved with only 4 individual photodetectors coupled to a thick rectangular glass lens. A larger number of detectors would provide better resolutions. The parameters of ray-tracing simulations were first adjusted to match the experimental data from a simplified geometry. Then, simulations were used to estimate the expected signals with an eye model, paving the way to a promising outlook. The combination of hardware and software solutions here presented aims at addressing the trade-off between power consumption and angular resolution in the estimation of the direction of gaze which is crucial for pervasive eye tracking

First Simultaneous Acquisition of a Clinical SPECT-MRI Brain INSERT

The INSERT (INtegrated SPECT/MRI for Enhanced stratification of brain tumours in Radio-chemoTherapy) is currently the only MRI-compatible SPECT stationary system for clinical application, in particular for brain multimodal imaging with an inner bore of 28 cm and a field of view of 20 cm (transaxial) × 10 cm (axial). The intrinsic spatial resolution is 1 mm and the extrinsic one is 10 mm. This modular scanner fits in an unmodified MRI scanner and is a scale-up of a smaller preclinical version, whose mutual compatibility with MRI was extensively characterized. It is composed of 20 detection modules (with 8-mm thick CsI:Tl scintillators of 5 cm 10 cm area read by an array of SiPM) and a massive multi-mini×slit-slat collimator, realized in tungsten. Here we report the first demonstration of successful simultaneous SPECT/MRI acquisition of phantoms (hot rods) using a commercial transceiver coil in a Siemens Biograph mMR scanner

Challenges in Acquiring Clinical Simultaneous SPECT-MRI on a PET-MRI Scanner

The INSERT is the world’s first clinical SPECTMRI brain imaging system based on scintillation detectors with a SiPM readout. Here we demonstrate its use within a clinical MRI environment for the first time. Using a standard transmit-receive head coil, and with an appropriate selection of a custom MRI sequence (GRE), we overcome mutual interference. The INSERT and its bulky 50 kg tungsten collimator introduce magnetic field inhomogeneity. Due to the specific MRI-compatible collimator design, inhomogeneity is compensated by shimming, leading to simultaneous acquisition. We process the SPECT data acquired alongside the MRI sequence to evaluate the SPECT system performance and the impact of the MRI. Finally, we present a set of simultaneous SPECT-MRI acquisitions, demonstrating multimodal imaging capabilities, albeit with a limited MRI sequence

Adhesion of Immature and Mature T Cells Induces in Human Thymic Epithelial Cells (TEC) Activation of IL-6 Gene Trascription Factors (NF-κB And NF-IL6) and IL-6 Gene Expression : Role of αtβ1 and α6β4 Integrins

T cell precursors homed to thymus develop in close contact with stromal cells. Among them, thymic epithelial cells (TEC) are known to exert dominant roles in their survival and functional shaping. Key molecules mediating TEC/thymocytes interactions include cytokines and growth factors secreted by the two cell types and adhesion receptors mediating cell contact. Signaling events triggered in thymocytes by adhesion to epithelial cells have been extensively investigated, whereas little is known on the opposite phenomenon. We have previously investigated this issue in a co-culture system composed of TEC cultures derived from human normal thymus and heterologous thymocytes. We demonstrated that thymocytes adhere to TEC involving β1 and β4 integrins and induce the clustering of (α3β1 and α6β4 heterodimers at the TEC surface. In addition thymocyte adhesion was followed by activation of NF-κB and NF-IL6 gene transciption factors and enhanced IL-6 production. The two latter phenomena were reproduced by the cross-linking of the α3, α6, β1 and β4 integrins, thus implying that the α3β1 and α6β4 heterodimers can signal during thymocyte adhesion. We have extended our previous work investigating in the same experimental setting the inducing activity of non stimulated or activated policlonal or clonal mature T cells as representative of the more mature thymocyte subset. We found that adhesion of unstimulated T cell i) involved β1, but not β4 integrin functions at the surface ii) induced the clustering of α3β1 , but not α2β1 heterodimers at the TEC surface and iii) up-regulated the nuclear binding activity of NF-κB transcription factor and the IL-6 secretion. We propose that α3β1 and α6β4 heterodimers are induced to cluster at the TEC surface recognizing yet unknown cellular ligands differentially expressed during T cell development