A tomographic reconstruction algorithm for cross-sectional imaging of IMRT beams from six projections.

. Patient-specific Quality Assurance (QA) measurements are of key importance in radiotherapy for safe and efficient treatment delivery and allow early detection of clinically relevant errors. Such QA processes remain challenging to implement for complex Intensity Modulated Radiation Therapy (IMRT) radiotherapy fields delivered using a multileaf collimator (MLC) which often feature small open segments and raise QA issues similar to those encountered in small field dosimetry.

A novel QA phantom based on scintillating fiber ribbons with implementation of 2D dose tomography for small-field radiotherapy.

Purpose: To develop a novel instrument for real-time quality assurance (QA) procedures in radiotherapy. The system implements a scintillation-based phantom and associated signal acquisition and processing modules and aims to monitor two-dimensional (2D) dose distributions of small fields.

Materials And Methods: For the proposed phantom, we have designed and realized a prototype implementing six high-resolution tissue-equivalent scintillating fiber ribbons stacked with in-plane 30° rotated orientations from each other.

Origin and age of an ongoing radioactive contamination of soils near La hague reprocessing plant based on Pu/Pu and Am/Pu current ratios and Sr and Ln(III) soil contents.

Nuclear reprocessing plants are sources of environmental contamination by gaseous or liquid discharges. Numerous radionuclides are of concern, with actinides and Sr being the most radiotoxic. Environmental radioactivity survey programs mostly use γ-spectrometry to track contaminations because γ-spectrometry is very cost effective and can be carried out on raw samples.

Radionuclides in the Environment in Switzerland: A Retrospective Study of Transfer from Soil to the Human Body.

Natural radionuclides are ubiquitous in the environment. In addition, artificial radionuclides are present in the Swiss environment after the fallout of the nuclear bomb tests of the 1950s and 1960s, after the accident of the Chernobyl nuclear power plant, or after authorized discharges from the Swiss nuclear power plants and research centres. These radionuclides can create a radiological hazard to the environment and humans because of the increased risk of cancer due to the ionizing radiation they produce.

SciFi detector and associated method for real-time determination of profile and output factor for small fields in stereotactic radiotherapy.

Purpose: For determining small-field profile and output factor during stereotactic radiotherapy quality assurance (QA) procedures, we propose a novel system based on the scintillating fiber (SciFi) detector with output image acquisition and processing to allow real-time monitoring of profile and output factor.

Materials And Methods: The employed detector is a SciFi detector made of tissue-equivalent scintillating plastic fibers arranged in 6-layer fiber ribbons with a fiber pitch of 275 μm in each layer. The scintillating signal at the detector output is acquired by a sCMOS (scientific complementary metal-oxide-semiconductor) camera and represents the projected field profile along the fibers axis.

Fan-Beam Based Virtual Fluoroscopy for Navigated Catheterization in Interventional Radiology.

Personalized medicine implies reducing invasiveness of therapeutic procedures. Although interventional radiology proved a very interesting alternative to surgical procedures, it still raises concerns due to the irradiation dose received by the medical team (and by the patient). We propose a novel concept allowing to reduce very significantly the irradiation dose during the phases where tools inserted in the patient have to be tracked with respect to previously acquired images.

Determination of Sr and Sr in fresh cow milk and raw urine using crystalline synthetic tunnel manganese oxides and layered metal sulfides.

Sr and Sr are both fission products of high radiotoxicity, which can be released in significant amounts in the event of a nuclear accident. Radiostrontium isotopes will follow calcium all along the food chain and, after ingestion, accumulate in the bones. Therefore, it is imperative to be able to determine Sr and Sr in raw milk samples in case of an accidental situation to evaluate the dose given by both radionuclides to the population.

Determination of Ra at low levels in environmental, urine, and human bone samples and Ra in bone biopsy using alpha-spectrometry and metrological traceability to Th/Ra or Ra.

Ra is a natural radioelement emitting α and γ radiations. It can be highly concentrated in TENORM materials from the petroleum or fertilizer industries. In Switzerland, Ra is currently a radioactive inheritance problem from the watch industry.

Design and testing of a phantom and instrumented gynecological applicator based on GaN dosimeter for use in high dose rate brachytherapy quality assurance.

Purpose: High dose rate brachytherapy (HDR-BT) is widely used to treat gynecologic, anal, prostate, head, neck, and breast cancers. These treatments are typically administered in large dose per fraction (>5 Gy) and with high-gradient-dose-distributions, with serious consequences in case of a treatment delivery error (e.g.

Preliminary testing of GaN-based dosimeters for electron beam radiotherapy.

The response of an implantable in vivo dosimetric system based on gallium nitride radioluminescence was investigated for electron beam radiotherapy using ELEKTA SLi and VARIAN Clinac 2100 CD Linear Accelerators. A bi-channel method has been implemented for fibre background rejection. The percentage depth dose (PDD) profiles were measured in polymethyl methacrylate for 6, 12 and 18 MeV electron beams.

Implementation and validation of a fluence pencil kernels model for GaN-based dosimetry in photon beam radiotherapy.

Gallium nitride (GaN), a direct-gap semiconductor that is radioluminescent, can be used as a transducer yielding a high signal from a small detecting volume and thus potentially suitable for use in small fields and for high dose gradients. A common drawback of semiconductor dosimeters with effective atomic numbers higher than soft tissues is that their responses depend on the presence of low energy photons for which the photoelectric cross section varies strongly with atomic number, which may affect the accuracy of dosimetric measurements. To tackle this 'over-response' issue, we propose a model for GaN-based dosimetry with readout correction.

Fiber background rejection and crystal over-response compensation for GaN based in vivo dosimetry.

For dosimetric measurements using an implantable optical fiber probe with GaN (Gallium Nitride) scintillator as radioluminescence (RL) transducer, a bi-channel method is proposed to reject the background contribution of the irradiated fiber segment. It is based on spectral differences between the narrow-band light emission from GaN and the large-band background from the irradiated optical fiber. Experimental validation of this method using 6 MV photon beam has shown that the remaining background contribution after subtraction is below 1.

CMOS buried quad p-n junction photodetector for multi-wavelength analysis.

This paper presents a buried quad p-n junction (BQJ) photodetector fabricated with a HV (high-voltage) CMOS process. Multiple buried junction photodetectors are wavelength-sensitive devices developed for spectral analysis applications where a compact integrated solution is preferred over systems involving bulk optics or a spectrometer due to physical size limitations. The BQJ device presented here is designed for chip-based biochemical analyses using simultaneous fluorescence labeling of multiple analytes such as with advanced labs-on-chip or miniaturized photonics-based biosensors.

Discovery of a Novel Series of CRTH2 (DP2) Receptor Antagonists Devoid of Carboxylic Acids.

Antagonism of the CRTH2 receptor represents a very attractive target for a variety of allergic diseases. Most CRTH2 antagonists known to date possess a carboxylic acid moiety, which is essential for binding. However, potential acid metabolites O-acyl glucuronides might be linked to idiosynchratic toxicity in humans.

Combining microfluidics and electrochemical detection.

This paper describes two configurations that integrate electrochemical detection into microfluidic devices. The first configuration is a low-cost approach based on the use of PCB technology. This device was applied to electrochemiluminescence detection.

Radiotherapy quality assurance by individualized in vivo dosimetry: state of the art.

The quality insurance in radiotherapy in the frame of highly complex technical process as Intensity modulated radiotherapy (IMRT) needs independent control of the delivered dose to the patient. Actually, up to now, most of the radiotherapy treatments rely only on computed dosimetry through a rather complicated series of linked simulation tool. This dosimetry approach requires also qualified treatment means based on cautious quality insurance procedures.

Amperometric quantification based on serial dilution microfluidic systems.

This paper describes a microfluidic device fabricated in poly(dimethylsiloxane) that was employed to perform amperometric quantifications using on-chip calibration curves and on-chip standard addition methods. This device integrated a network of Au electrodes within a microfluidic structure designed for automatic preparation of a series of solutions containing an electroactive molecule at a concentration linearly decreasing. This device was first characterized by fluorescence microscopy and then evaluated with a model electroactive molecule such as Fe(CN(6))(4-).

Discovery of a new class of potent, selective, and orally bioavailable CRTH2 (DP2) receptor antagonists for the treatment of allergic inflammatory diseases.

A novel chemical class of potent chemoattractant receptor-homologous expressed on Th2 lymphocytes (CRTH2 or DP2) antagonists is reported. An initial and moderately potent spiro-indolinone compound ( 5) was found during a high-throughput screening campaign. Structure-activity relationship (SAR) investigation around the carboxylic acid group revealed that changes in this part of the molecule could lead to a reversal of functional activity, yielding weakly potent agonists.

Fibrogenic fibroblasts increase intercellular adhesion strength by reinforcing individual OB-cadherin bonds.

We have previously shown that the switch from N-cadherin to OB-cadherin expression increases intercellular adhesion between fibroblasts during their transition from a migratory to a fibrogenic phenotype. Using atomic force microscopy we here show that part of this stronger adhesion is accomplished because OB-cadherin bonds resist approximately twofold higher forces compared with N-cadherin junctions. By assessing the adhesion force between recombinant cadherin dimers and between native cadherins in the membrane of spread fibroblasts, we demonstrate that cadherin bonds are reinforced over time with two distinct force increments.

Implementation of electrochemiluminescence microanalysis in PCB technology.

We present an instrumental development to implement electrochemiluminescence (ECL) microanalysis using printed circuit board (PCB) technology. PCB gold macro-(10 mm2) and micro- (0.09 mm2) electrodes and two ECL microfluidic devices are designed, fabricated and tested via luminol ECL detection.

PCB-based integration of electrochemiluminescence detection for microfluidic systems.

This communication presents an instrumental development based on the printed circuit board (PCB) technology to integrate electrochemiluminescence (ECL) analysis in microfluidic systems. PCB gold macro- (10 mm2) and micro- (0.09 mm2) electrodes and two ECL microfluidic devices are designed, fabricated and tested via luminol ECL detection.

Investigation of the mixing efficiency of a chaotic micromixer using thermal lens spectrometry.

This work investigates the efficiency of a chaotic micromixer using thermal lens spectrometry. The outlet of the mixing device was connected to a thermal lens detection head integrating the probe beam optical fibers and the sample capillary. The chaotic micromixer consisted of a Y-shaped poly(dimethylsiloxane) (PDMS) microchip in which ribbed herringbone microstructures were etched on the floor of the main channel.

Focal adhesion size controls tension-dependent recruitment of alpha-smooth muscle actin to stress fibers.

Expression of alpha-smooth muscle actin (alpha-SMA) renders fibroblasts highly contractile and hallmarks myofibroblast differentiation. We identify alpha-SMA as a mechanosensitive protein that is recruited to stress fibers under high tension. Generation of this threshold tension requires the anchoring of stress fibers at sites of 8-30-microm-long "supermature" focal adhesions (suFAs), which exert a stress approximately fourfold higher (approximately 12 nN/microm2) on micropatterned deformable substrates than 2-6-microm-long classical FAs.

Discovery and development of a new class of potent, selective, orally active oxytocin receptor antagonists.

We report a novel chemical class of potent oxytocin receptor antagonists showing a high degree of selectivity against the closely related vasopressin receptors (V1a, V1b, V2). An initial compound, 7, was shown to be active in an animal model of preterm labor when administered by the intravenous but not by the oral route. Stepwise SAR investigations around the different structural elements revealed one position, the arenesulfonyl moiety, to be amenable to structural changes.

Evidence for signaling via gap junctions from smooth muscle to endothelial cells in rat mesenteric arteries: possible implication of a second messenger.

We investigated heterocellular communication in rat mesenteric arterial strips at the cellular level using confocal microscopy. To visualize Ca(2+) changes in different cell populations, smooth muscle cells (SMCs) were loaded with Fluo-4 and endothelial cells (ECs) with Fura red. SMC contraction was stimulated using high K(+) solution and Phenylephrine.