Dual-comb spectroscopy of ammonia formation in non-thermal plasmas.

Plasma-activated chemical transformations promise the efficient synthesis of salient chemical products. However, the reaction pathways that lead to desirable products are often unknown, and key quantum-state-resolved information regarding the involved molecular species is lacking. Here we use quantum cascade laser dual-comb spectroscopy (QCL-DCS) to probe plasma-activated NH3 generation with rotational and vibrational state resolution, quantifying state-specific number densities via broadband spectral analysis. The measurements reveal unique translational, rotational and vibrational temperatures for NH3 products, indicative of a highly reactive, non-thermal environment. Ultimately, we postulate on the energy transfer mechanisms that explain trends in temperatures and number densities observed for NH3 generated in low-pressure nitrogen-hydrogen (N2-H2) plasmas.

Neurostimulator-induced ECG artefacts: A systematic analysis.

OBJECTIVES: Deep brain stimulation (DBS) is known to interfere with electrocardiographic (ECG) examinations. In emergency situations, such electrical interferences can not only thwart ECG diagnostics, but even induce an ECG pattern that causes the emergency medical service to initiate inadequate or even harmful therapy. Aim of this prospective study was to evaluate factors influencing ECG interpretation in DBS and to evaluate the susceptibility of ECG criteria 'frequency', 'rhythm', 'regularity', 'QRS-configuration', and 'ST-segment' on neurostimulation. PATIENTS AND METHODS: In 33 DBS patients (17 male, 16 female, mean age 64 years), limb-, 12 channel-, Nehb, and adhesive paddle-lead ECG were performed in activated (n = 33) and deactivated (n = 31) stimulation mode during outpatient follow-up examinations. The examinations were carried out using three different ECG devices (two portable emergency ECG-monitor/defibrillation/pacer-devices, one stationary hospital device), resulting in 4096 ECG leads. Statistics have been based on regression analyses and on a maximum likelihood estimation regression model. RESULTS: Monopolar settings were found to be a relevant factor interfering significantly more often with ECG recording than bipolar parameters (p < 0.0001). Due to recurring movement artefacts, deactivation of bipolar stimulation might even significantly worsen ECG quality (p < 0.0001). Interpretability of 'rhythm' (ß = -0.088, p = 0.03) and 'frequency' (ß = -0.110, p = 0.02) revealed significant negative correlation to the applied neurostimulation voltage. Nehb lead yielded in highest ECG interpretability. CONCLUSION: Bipolar neurostimulation mode barely affected the ECGs; furthermore, the suppression of motion artefacts by neurostimulation can improve ECG quality. If monopolar neurostimulation is required, at least, stimulation voltage should be as low as possible to obtain good stimulation results.

RES-Q-Trace: A Mobile CEAS-Based Demonstrator for Multi-Component Trace Gas Detection in the MIR.

Sensitive trace gas detection plays an important role in current challenges occurring in areas such as industrial process control and environmental monitoring. In particular, for medical breath analysis and for the detection of illegal substances, e.g., drugs and explosives, a selective and sensitive detection of trace gases in real-time is required. We report on a compact and transportable multi-component system (RES-Q-Trace) for molecular trace gas detection based on cavity-enhanced techniques in the mid-infrared (MIR). The RES-Q-Trace system can operate four independent continuous wave quantum or interband cascade lasers each combined with an optical cavity. Twice the method of off-axis cavity-enhanced absorption spectroscopy (OA-CEAS) was used, twice the method of optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS), respectively. Multi-functional software has been implemented (i) for the general system control; (ii) to drive the four different laser sources and (iii) to analyze the detector signals for concentration determination of several molecular species. For the validation of the versatility and the performance of the RES-Q-Trace instrument the species NO, N2O, CH4, C2H4 and C3H6O, with relevance in the fields of breath gas analysis and the detection of explosives have been monitored in the MIR with detection limits at atmospheric pressure in the ppb and ppt range.

Quantum cascade laser absorption spectroscopy as a plasma diagnostic tool: an overview.

The recent availability of thermoelectrically cooled pulsed and continuous wave quantum and inter-band cascade lasers in the mid-infrared spectral region has led to significant improvements and new developments in chemical sensing techniques using in-situ laser absorption spectroscopy for plasma diagnostic purposes. The aim of this article is therefore two-fold: (i) to summarize the challenges which arise in the application of quantum cascade lasers in such environments, and, (ii) to provide an overview of recent spectroscopic results (encompassing cavity enhanced methods) obtained in different kinds of plasma used in both research and industry.

Respiratory gating in positron emission tomography: a quantitative comparison of different gating schemes.

Respiratory gating is used for reducing the effects of breathing motion in a wide range of applications from radiotherapy treatment to diagnostical imaging. Different methods are feasible for respiratory gating. In this study seven gating methods were developed and tested on positron emission tomography (PET) listmode data. The results of seven patient studies were compared quantitatively with respect to motion and noise. (1) Equal and (2) variable time-based gating methods use only the time information of the breathing cycle to define respiratory gates. (3) Equal and (4) variable amplitude-based gating approaches utilize the amplitude of the respiratory signal. (5) Cycle-based amplitude gating is a combination of time and amplitude-based techniques. A baseline correction was applied to methods (3) and (4) resulting in two new approaches: Baseline corrected (6) equal and (7) variable amplitude-based gating. Listmode PET data from seven patients were acquired together with a respiratory signal. Images were reconstructed applying the seven gating methods. Two parameters were used to quantify the results: Motion was measured as the displacement of the heart due to respiration and noise was defined as the standard deviation of pixel intensities in a background region. The amplitude-based approaches (3) and (4) were superior to the time-based methods (1) and (2). The improvement in capturing the motion was more than 30% (up to 130%) in all subjects. The variable time (2) and amplitude (4) methods had a more uniform noise distribution among all respiratory gates compared to equal time (1) and amplitude (3) methods. Baseline correction did not improve the results. Out of seven different respiratory gating approaches, the variable amplitude method (4) captures the respiratory motion best while keeping a constant noise level among all respiratory phases.

Gated listmode acquisition with the quadHIDAC animal PET to image mouse hearts.

PURPOSE: The aim of this study was to develop ECG and respiratory gating in combination with listmode acquisition for the quadHIDAC small-animal PET scanner. METHODS: ECG and respiratory gating was realized with the help of an external trigger device (BioVET) synchronized with the listmode acquisition. Listmode data of a mouse acquisition (injected with 6.5 MBq of 18F-FDG) were sorted according to three different gating definitions: 12 cardiac gates, 8 respiratory gates and a combination of 8 cardiac and 8 respiratory gates. Images were reconstructed with filtered back-projection (ramp filter), and parameters like left ventricular wall thickness (WT), wall-to-wall separation (WS) and blood to myocardium activity ratios (BMR) were calculated. RESULTS: Cardiac gated images show improvement of all parameters (WT 2.6 mm, WS 4.1 mm, BRM 2.3) in diastole compared to ungated images (WT 3.0 mm, WS 3.4 mm, BMR 1.3). Respiratory gating had little effect on calculated parameters. CONCLUSION: ECG gating with the quadHIDAC can improve myocardial image quality in mice. This could have a major impact on the calculation of an image-derived input function for kinetic modelling.

Organ movement reduction in PET/CT using dual-gated list-mode acquisition.

PURPOSE: Imaging of moving organs using the PET leads to blurred images due to long acquisition times. Simultaneous cardiac and respiratory gating of list-mode PET/CT is evaluated with the aim to improve image quality and assess the organ movement. METHODS: We performed a N-13 ammonia PET/CT scan with a human volunteer, using the Siemens Biograph Sensation 16 scanner with list-mode acquisition. For ECG gating we used the scanner's integrated ECG device. Respiratory gating was done with the BioVet pneumatic sensor system. RESULTS: The sorting of the list-mode data post acquisition produced the desired matrix of eight cardiac times eight respiratory images. Organ movement could be measured in the series of gated PET images. The quantitation of tracer uptake in the myocardium showed artifacts due to the CT-based attenuation correction. CONCLUSION: Double gating is feasible in human PET/CT scans using a list-mode-based scan protocol. The image quality can be enhanced using double gated list-mode acquisition in PET/CT Attenuation correction protocols in PET using a single not gated fast CT introduces artifacts in moving organs.

Lung motion correction on respiratory gated 3-D PET/CT images.

Motion is a source of degradation in positron emission tomography (PET)/computed tomography (CT) images. As the PET images represent the sum of information over the whole respiratory cycle, attenuation correction with the help of CT images may lead to false staging or quantification of the radioactive uptake especially in the case of small tumors. We present an approach avoiding these difficulties by respiratory-gating the PET data and correcting it for motion with optical flow algorithms. The resulting dataset contains all the PET information and minimal motion and, thus, allows more accurate attenuation correction and quantification.

Tumor size, axillary lymph node status and steroid receptor expression in breast cancer: prognostic relevance 5 years after surgery.

Tumor size, axillary lymph node status and expression of steroid receptors are well-established prognostic factors in breast cancer. However, it is not clear if these prognostic factors are time-dependent variables and lose their significance after several years of disease-free survival. To analyse how long these factors keep their prognostic relevance survival of 1162 breast cancer patients was analysed retrospectively. The post-operative follow-up period was split into consecutive 2-year intervals and each interval was analysed for rate of recurrence and rate of tumor depending deaths. Furthermore, a multivariate analysis was performed for the total follow-up time and for the follow-up period starting 5 years after surgery. Multivariate analysis revealed tumor size, axillary lymph node status and estrogen receptor status as independent prognostic parameters. Analysing separately the rate of recurrences and tumor-related deaths during consecutive 2-year intervals, only the tumor size was a constant prognostic parameter, whereas prognostic relevance of lymph node status decreased. Estrogen receptor status associated with favourable prognosis during the first years after surgery changed to an unfavourable prognostic factor 4 years after surgery. To summarize, prognostic factors obtained at the time of surgery can lose their significance with increasing disease-free survival.

Comparison of GnRH agonists and antagonists in unselected IVF/ICSI patients treated with different controlled ovarian hyperstimulation protocols: a matched study.

OBJECTIVES: To evaluate the results of the use of GnRH antagonist (GnRHant) and GnRH analog (GnRHa) in two matched groups of unselected IVF/ICSI patients in a retrospective matched pair analysis. STUDY DESIGN: Patients (n=52) were stimulated with human menopausal gonadotropin (hMG) and/or recombinant FSH (rFSH). In Group I (n=26) a daily dose of 0.25mg of Cetrorelix (GnRHant) was administered when follicles reached a diameter of > or = 14 mm. Patients in Group II (n=26) were first desensitized with GnRHa triptorelin long protocol, which was continued during the gonadotropins treatment until the induction of ovulation. RESULTS: In both groups, serum LH levels remained low during the stimulation. The mean length of stimulation, and the dose of FSH required per patient were similar in both groups. The mean E2 level on day of hCG administration was significantly higher in the patients of Group II (2076+/-1430 versus 1145+/-605 pg/ml), however, a progressive increase in serum E2 concentration during the cycle was noted in both groups. A median of 5.38 and 6.34 mature oocytes per patient was obtained, and the fertilization rate was 59.3% in Group I and 63.6% in Group II. Pregnancy rate (PR) were better in Group II (15 versus 5%), and no severe or moderate ovarian hyperstimulation syndrome (OHSS) occurred. CONCLUSIONS: GnRHant and GnRHa provide comparable results in unselected patients, while GnRHant allows a higher flexibility in the treatment.