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Objectives: To validate near infra-red (NIR) based optical spectroscopy measurements of hepatic fat content using a minimally invasive needle-like probe with integrated optical fibers. The results were compared with magnetic resonance spectroscopy (MRS) as validation and with histopathology, being the clinical golden standard. Additionally, ex vivo magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy and high performance thin layer chromatography (HPTLC) were performed for comparison. Materials and Methods: Ten mice were used for the study of which half received a regular chow diet and the other half a high fat diet to induce obesity and hepatosteatosis. The mice were imaged with a clinical 3-Tesla MR to select a region of interest (ROI) within the right and left lobes of the liver, where MRS measurements were acquired in vivo. Subsequently, optical spectra were measured at the surface of the liver at six different positions after opening of the chest. Additionally, hepatic fat was determined by MAS-NMR spectroscopy and HPTLC. Histopathologic analyses were performed and used as the reference standard. Pearson's correlation and linear regression analysis were done to assess the correlation of the various techniques with NIR. A one-way analysis of variance including post hoc Tukey's multiple comparison tests were used to study the difference in fat estimation between the various techniques. Results: For both of the mice groups, the estimated fat fractions bythe various techniques were significantly similar, P = 0.072 and 0.627 for chow diet and high fat diet group, respectively. The Pearson's correlation value between NIR and the other techniques for fat determination showed the same strong linear correlation (P above 0.990, P < 0.001) except for histopathology (P = 0.925, P < 0.001) which is a rather qualitative measure. Linear regression coefficient computed to compare NIR to the other techniques resulted in values close to unity with MRS having the narrowest confidence interval (CI) (r =0.935, 95% CI: [0.860-1.009]) demonstrating very comparable results between NIR and MRS. Conclusions: NIR spectroscopy measurements from a needle-like probe with integrated optical fibers for sensing at the tip of the needle can quickly and accurately determine hepatic fat content during an interventional procedure and might therefore be a promising novel diagnosing tool in the clinic.

Fast reconstruction is crucial for the implementation of CS-SENSE onclinical scanners. Thus, improvements of the reconstruction speed are desirable, both in terms of algorithms with improved convergence and parallel implementation. In this work, we propose a modified CS-SENSE reconstruction method based on the Nesterov’s optimal gradientscheme, which is less sensitive to inaccuracies in the coil sensitivity estimation and has an improved convergence speed.

In this work, we investigate the influence of the sampling pattern on the convergence behaviour of {1-regularized SENSE reconstruction at different reduction factors. In other words, we try to answer the question what improvement can CS-SENSE provide over {1-denoised SENSE.

In this work, we present a CS reconstruction based on statistical non-local self-similarity filtering (STAINLeSS), in which the parameters are entirely determined by the noise estimation in the receive channels obtained from a standard noise measurement. The method achieves improved image quality compared to wavelet based CS reconstruction in particular in SENSE based multi-coil reconstruction due to itsadaptivity to spatially varying noise. The proposed method providesimproved robustness due to the lack of free parameters which is crucial for the clinical applicability of CS.

Statistical, iterative reconstruction techniques have become a major research topic in the CT sector. These techniques promise a better system model, which is used for the inversion of the tomographic problem, and therefore better reconstruction results. Due to the ill–posedness of these problems, regularization is required in the cost functions in order to stabilize the algorithm and to reduce the noise in the resulting images. The strength of the regularization is usually changed by using an appropriate multiplicative factor, which in most cases has to be determined empirically with major efforts. This paper describes a new automated selection of this factor by using a quality criterion and a regulator, which controls the multiplicative factor over the iterations to a desired level. The method is light–weight, robust and also applicable for other iterative methods like de–noising.

Lu3Al5O12 (LuAG) doped with Ce3+ is a promising scintillator material with a high density and a fast response time. The light output under x-ray or y-ray excitation is however well below the theoretical limit. In this paper the influence of co-doping with Tb3+ is investigated with the aim to increase the light output. For singly doped LuAG (with Ce3+ or Tb3+) high resolution spectra are reported giving insight in the energy level structure of the two ions in LuAG. For Ce3+ zero-phonon lines and vibronic structure is observed for thetwo lowest energy d-bands and the Stokes shift (2350 cm-1) and Huang-Rhys coupling parameter (S = 9) have been determined. For Tb3+ transition to the high spin (HS) and low spin (LS) states are observed (including a zero-phonon line and vibrational structure for the highspin state). The HS-LS splitting is 5400 cm-1 which is smaller thanusually observed and is explained by a reduction of the d-f exchangecoupling parameter J by covalency. Upon replacing the smaller Lu3+ion with the larger Tb3+ ion, the crystal field splitting for the lowest d-states increases and the Ce3+ emission shows a redshift, causing the lowest d-state to shift below the 5D4 state of Tb3+ and allowing for efficient energy transfer from Tb3+ to Ce3+ down to the lowest temperatures. Luminescence decay measurements confirm efficientenergy transfer from Tb3+ to Ce3+ and provide a qualitative understanding of the energy transfer process. Co-doping with Tb3+ does not result in the desired increase in light output and an explanation based on electron trapping in defects is discussed.

Source-gated transistors (SGTs) have potentially very high output impedance and low saturation voltages, which make them ideal as building blocks for high performance analog circuits fabricated in thin-film technologies. The quality of the saturation is greatly influenced by the design of the field-relief structure incorporated into the source electrode. Starting from measurements on self-aligned polysilicon structures, we show through numerical simulations how the field plate design can be improved. A simple source field plate around 1μm long situated several tens of nm above the semiconductor can increase the low-voltage intrinsic gain by more than two orders of magnitude and offers adequate tolerance to process variations in a moderately scaled thin-film SGT.

The integration of therapeutic interventions with diagnostic imaginghas been recognized as one of the next technological developments that will have a major impact on medical treatments. Therapeutic applications using ultrasound, for example thermal ablation, hyperthermia or ultrasound induced drug delivery, are examples for image-guidedinterventions that are currently investigated. While thermal ablation using MR-HIFU is entering the clinic, ultrasound mediated drug delivery is still in a research phase, but holds promise to enable newapplications in localized treatments. The use of ultrasound for thedelivery of drugs has been demonstrated in particular the field ofcardiology and oncology for a variety of therapeutics ranging from small drug molecules to biologics and nucleic acids exploiting temperature or pressure mediated delivery schemes.

Introduction: Autocompletion supports human-computer interaction in software applications that let users enter textual data. We will be inspired by the use case in which medical professionals enter ontology concepts, catering the ongoing demand for structured and standardized data in medicine. Objectives: Goal is to give an algorithmic analysis of one particular autocompletion algorithm, called multi-prefix matching algorithm, which suggests terms whose words' prefixes contain all words in the string typed by the user, e.g., in this sense, opt ner me matches optic nerve meningioma. Second we aim to investigate how well it supports users entering concepts from a large and comprehensive medical vocabulary (snomed ct). Methods: We give a concise description of the multi-prefix algorithm, and sketch how it can be optimized to meet required response time. Performance will be compared to a baseline algorithm, which gives suggestions that extend the string typed by the user to the right, e.g. optic nerve m gives optic nerve meningioma, but opt ner me does not. We conduct a user experiment in which 12 participants are invited to complete 40 snomed ct terms with the baseline algorithm and another set of 40 snomed ct terms with the multi-prefix algorithm. Results: Our results show that users need significantly fewer keystrokes when supported by the multi-prefix algorithm than when supported by the baseline algorithm. Conclusions: The proposed algorithm is a competitive candidate for searching and retrieving terms from a large medical ontology.

In a Luminescent Solar Concentrator (LSC), short-wavelength light isconverted by a luminescent material into long-wavelength light, which is guided towards a photovoltaic cell. In principle, an LSC allows for high concentration, but in practice this is prevented by lossmechanisms like limited sunlight absorption, limited quantum efficiency and high self absorption. To tackle these problems, a suitable luminescent material is needed. Another important loss mechanism is the escape of luminescent radiation into directions that do not stayinside the light guide. To reduce this amount, wavelength-selectivefilters can be applied that reflect the luminescent radiation back into the light guide while transmitting the incident sunlight. In this paper, we discuss experiments and simulations of new luminescent and filter materials. We will introduce a phosphor with close-to-optimal luminescent properties. A problem for use in an LSC is the largescattering of this material; we will discuss possible solutions forthis. Furthermore, we will discuss the use of broad-band cholesteric filters in combination with this phosphor.

Focusing of attention on a repetitive visual stimulation (RVS) at aconstant frequency, elicits the so called steady-state visual evokedpotential (SSVEP). This effect can be advantageously utilized in brain-computer interfaces (BCIs). SSVEP based BCIs can offer higher bitrates and require shorter training time as compared to other BCI modalities. Detection of the SSVEP from the EEG can be facilitated through spatial filtering (linear combination of the signals recorded at several electrodes). Literature offers several options to performthis. In this paper we propose a taxonomy to categorize these methods and we extensively evaluate them using 22 stimulation frequencies.We suggest improvements to existing methods to increase the SSVEP detection performance. We also consider practical aspects in the discussion of results.

Purpose: Treatment of malignant tumors by either hyperthermia induced drug delivery or thermal ablation requires complete coverage of the treatment area and precise control of the thermal dose.Both can be achieved by volumetric ultrasonic heating in combination with simultaneous MR-based temperature mapping. The translation ofthese techniques to the clinic requires thorough preclinical testing in large cohorts. Mouse and rat studies are preferred over largeranimals for ethical reasons as well as the larger variety of available tumor models. Our work aims to develop temperature induced drug delivery and ablation protocols in rats and to subsequently evaluatetreatment outcome using small animal imaging methods. To this end, we adapted a clinical MR-HIFU system for the treatment of rats by utilizing a dedicated small animal setup. Methods: All animals were positioned in a HIFU dedicated small animal 4-channel MR volume coil that was used as add-on to a clinical 3T Philips Sonalleve MR-HIFU system. Hyperthermia was performed for 15 min using binary temperaturecontrol on lateral gastrocnemius muscle (n = 5) and on subcutaneousinoculated tumors on the hind limb of rats (9L rat glioma; n = 5).For thermal ablation, tumors were partly heated to T = 65 °C with continuous wave ultrasound (1.44 MHz) under MR temperature monitoring(n = 5). The treatment effect was assessed with T2-weighted imagingand dynamic contrast enhanced (DCE-) MRI using Gd-DTPA as contrast agent. Excised muscle and tumors were further evaluated with histology. Results: The target temperatures were readily achieved in hyperthermia and ablation treatments while changes in body temperature remained below 1 °C. For hyperthermia treatments, no indication of tissue damage was found on MR images. Analysis of the Gd-DTPA uptake kinetics post ablation indicated a difference in non-perfused volume inthe tumor of 371 ± 123 mm3 (&#916; tissue volume with ktrans &#8805; 0.04 min-1). NADH-diaphorase staining of ablated tumors showed a sharp demarcation between viable and non-viable cells. Conclusion: These results demonstrate that both controlled hyperthermia and thermal ablation treatment of malignant tumors in small animals can be performed on a clinical MR-HIFU system. This approach provides all theadvantages of clinical MR-HIFU, such as volumetric heating, temperature feedback control and a clinical software interface, while also having many of the advantages of a dedicated small animal system. Theuse of a clinical system facilitates a rapid translation of these protocols into the clinic.

Transmission gratings that combine a large diffraction angle with ahigh diffraction efficiency and low angular and wavelength dispersion could be used to collect sunlight in a light guide. In this paperwe determine what characteristics a grating should have in order tobe useful for such a solar concentrator. To this end we compare thediffractive properties of polarization gratings and classical surface relief gratings. It is found that polarization gratings and classical surface relief gratings have qualitatively comparable diffractive properties as long as their thickness-parameters are within the same regime. The diffraction efficiency of these gratings can be closeto 100% for a broad range of incoming angles when the period is large compared to the wavelength of the incoming light. This no longerholds for small-period gratings. For solar concentrators the more easily producible surface relief gratings are preferred over polarization gratings.

We developed a tri-modality imaging system for breast cancer imagingby integrating photoacoustic (PA) and thermoacoustic (TA) imaging techniques into a modified commercial ultrasound scanner. Laser and microwave excitation pulses were interleaved to enable PA and TA dataacquisition in parallel at the rate of 10 frames per second. The performance of the tri-modality imaging system was evaluated in-vitrousing phantom samples. A plastic tube (7 mm inner diameter, 25 mm length) filled with 30 mM methylene blue dye placed at a depth of 8.4cm in chicken breast tissue was successfully detected in PA images with an ultrasonic bandwidth of 1–5 MHz. The SNR at this depth was 15dB after averaging 200 signal acquisitions. Similarly, a plastic tube (7 mm inner diameter, 25 mm length) filled with high concentration salt water placed at a depth of 5.1 cm in porcine fat tissue was successfully detected in TA images. A PA noise-equivalent-sensitivityto methylene blue solution of 260 nM was achieved in chicken tissueat a depth of 3.4 cm and with a laser fluence of 17 mJ/cm2.

Large area detector computed tomography systems with fastrotating gantries enable volumetric dynamic cardiac perfusion studies. Prospectively ECG-triggered acquisitions limit the data acquisition to a predefined cardiac phase and thereby reduce X-ray dose andlimit motion artifacts. Even in the case of highly accurate prospective triggering and stable heart rate, spatial misalignment of the cardiac volumes acquired and reconstructed per cardiac cycle may occurdue to small motion pattern variations from cycle to cycle. These misalignments reduce the accuracy of the quantitative analysis of myocardial perfusion parameters on a per voxel basis. An image based solution to this problem is elastic 3D image registration of dynamic volume sequences with variable contrast, as it is introduced in thiscontribution. After circular cone-beam CT reconstruction of cardiacvolumes covering large areas of the myocardial tissue, the completeseries is aligned with respect to a chosen reference volume. The results of the quantitative perfusion analysis are compared on pig datausing the non-registered versus the registered data set. The reduced spatial misalignment leads to an improved characterization of myocardial perfusion confirming the potential of this method. Conclusions - In conclusion, an elastic image registration-based method was proposed to improve the characterization of CT-based estimates of myocardial perfusion. The technique’s performance, that was visually and quantitatively assessed on three pig data sets, confirmed its potential. The proposed method may also be applied to other perfusion studies being limited by inconsistent motion states.

In this case study, we designed a family game to explore whether this could be an effective and fun approach for raising the awareness of family members towards their energy use and, in the long run, to provide an effective tool for affecting their habits regarding sustainable behavior. The design of the family game implemented the metaphor of electricity as flowing liquid, fostered fun experiences and supported competitive and social elements. Dutch families with children, aged 5-11 years, participated in the design and evaluation of theconcept. We obtained valuable insights into the use and understanding of electricity by the families, how the families looked at responsible behaviors around their usage and how a game could integrate into the family context in a fun way.

In four papers, a set of eleven prerequisites for affective signal processing (ASP) were identified (van den Broek et al., 2010): validation, triangulation, a physiology-driven approach, contributions ofthe signal processing community, identification of users, theoretical specification, integration of biosignals, physical characteristics, historical perspective, temporal construction, and real-world baselines. Additionally, a review (in two parts) of affective computingwas provided. Initiated by the reactions on these four papers, we now present: i) an extension of the review, ii) a post-hoc analysis based on the eleven prerequisites of Picard et al.(2001), and iii) a more detailed discussion and illustrations of temporal aspects with ASP.

We propose in this paper an approach to quantifying the rate of atrophy of the brain of patients with Alzheimer’s disease. This approachis based on Computational Anatomy which al- lows the computation ofintermediate MR brain volumes be- tween the ones of regular scans.This increases dramatically the granularity of brain structure information, without requir- ing extra scans. We define two spaces: (i) the joint brain tissue deformation displacement vector magnitude andJacobian, (ii) the joint polar angles of the displacement vector. The shape of the distribution patterns in both spaces allow us to: (i)quan- tify atrophy rates of specific brain structures, such as, theven- tricles and the hippocampus, (ii) to build up models for the in- terpolation and extrapolation of atrophy rate parameters. The novelty of this approach is that it allows us to interpolate and extrapolate atrophy rate parameters computed from the two spaces, and thusderive precise models for patient diagnosis and/or prognosis. We tested this approach on a set of ADNI patients with diagnosed Alzheimer’s disease, mild cognitive impairment, and normal controls. This approach could also be used in the diagnosis of patients with other neurodegener- ative diseases, such as, frontal lobe dementia and Schizophre- nia.

There is an increasing demand to increase the economic value of radiology services and to empower the patient in his or her care process. In this paper we propose a system that automatically generates hyperlinks from medical terms in radiology reports to Wikipedia. This will help the user to understand the medical terminology, and will subsequently increase the value of the reports. We evaluate the performance of two state-of-the-art automatic link generation systems on aset of manually annotated radiology reports, and conclude that it is non-trivial to either of this general-purpose system directly to the radiology domain. We describe an automatic link generation systemthat targets the radiology domain. Specifically, we use a conditional random field model-based sequential labeling approach to identifymedical terms from radiology reports. For each medical term identified, we use machine learning techniques to identify its target pagein Wikipedia. Empirical results show that our approach effectively improves over the state-of-the-art systems on radiology data. Further, we find that the effectiveness of an automatic link generation system is determined by its ability to identify and link the medical terms that are infrequent.