Simultaneous Signal Acquisition Research Articles

Simultaneous and interleaved acquisition of NMR signals from different nuclei with a clinical MRI scanner

PurposeModification of a clinical MRI scanner to enable simultaneous or rapid interleaved acquisition of signals from two different nuclei.MethodsA device was developed to modify the local oscillator signal fed to the receive channel(s) of an MRI console. This enables external modification of the frequency at which the receiver is sensitive and rapid switching between different frequencies. Use of the device was demonstrated with interleaved and simultaneous 31P and 1H spectroscopic acquisitions, and with interleaved 31P and 1H imaging.ResultsSignal amplitudes and signal‐to‐noise ratios were found to be unchanged for the modified system, compared with data acquired with the MRI system in the standard configuration.ConclusionInterleaved and simultaneous 1H and 31P signal acquisition was successfully demonstrated with a clinical MRI scanner, with only minor modification of the RF architecture. While demonstrated with 31P, the modification is applicable to any detectable nucleus without further modification, enabling a wide range of simultaneous and interleaved experiments to be performed within a clinical setting. Magn Reson Med 76:1636–1641, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Chemiresistive and Gravimetric Dual-Mode Gas Sensor toward Target Recognition and Differentiation.

We demonstrate a dual-mode gas sensor for simultaneous and independent acquisition of electrical and mechanical signals from the same gas adsorption event. The device integrates a graphene field-effect transistor (FET) with a piezoelectric resonator in a seamless manner by leveraging multiple structural and functional synergies. Dual signals resulting from independent physical processes, i.e., mass attachment and charge transfer can reflect intrinsic properties of gas molecules and potentially enable target recognition and quantification at the same time. Fabrication of the device is based on standard Integrated Circuit (IC) foundry processes and fully compatible with system-on-a-chip (SoC) integration to achieve extremely small form factors. In addition, the ability of simultaneous measurements of mass adsorption and charge transfer guides us to a more precise understanding of the interactions between graphene and various gas molecules. Besides its practical functions, the device serves as an effective tool to quantitatively investigate the physical processes and sensing mechanisms for a large library of sensing materials and target analytes.

Multimodal optical coherence tomography and fluorescence lifetime imaging with interleaved excitation sources for simultaneous endogenous and exogenous fluorescence.

Multimodal imaging probes a variety of tissue properties in a single image acquisition by merging complimentary imaging technologies. Exploiting synergies amongst the data, algorithms can be developed that lead to better tissue characterization than could be accomplished by the constituent imaging modalities taken alone. The combination of optical coherence tomography (OCT) with fluorescence lifetime imaging microscopy (FLIM) provides access to detailed tissue morphology and local biochemistry. The optical system described here merges 1310 nm swept-source OCT with time-domain FLIM having excitation at 355 and 532 nm. The pulses from 355 and 532 nm lasers have been interleaved to enable simultaneous acquisition of endogenous and exogenous fluorescence signals, respectively. The multimodal imaging system was validated using tissue phantoms. Nonspecific tagging with Alexa Flour 532 in a Watanbe rabbit aorta and active tagging of the LOX-1 receptor in human coronary artery, demonstrate the capacity of the system for simultaneous acquisition of OCT, endogenous FLIM, and exogenous FLIM in tissues.

Methods and Best Practice to Intercompare Dissolved Oxygen Sensors and Fluorometers/Turbidimeters for Oceanographic Applications

In European seas, ocean monitoring strategies in terms of key parameters, space and time scale vary widely for a range of technical and economic reasons. Nonetheless, the growing interest in the ocean interior promotes the investigation of processes such as oxygen consumption, primary productivity and ocean acidity requiring that close attention is paid to the instruments in terms of measurement setup, configuration, calibration, maintenance procedures and quality assessment. To this aim, two separate hardware and software tools were developed in order to test and simultaneously intercompare several oxygen probes and fluorometers/turbidimeters, respectively in the same environmental conditions, with a configuration as close as possible to real in-situ deployment. The chamber designed to perform chlorophyll-a and turbidity tests allowed for the simultaneous acquisition of analogue and digital signals of several sensors at the same time, so it was sufficiently compact to be used in both laboratory and onboard vessels. Methodologies and best practice committed to the intercomparison of dissolved oxygen sensors and fluorometers/turbidimeters have been used, which aid in the promotion of interoperability to access key infrastructures, such as ocean observatories and calibration facilities. Results from laboratory tests as well as field tests in the Mediterranean Sea are presented.

Simultaneous Scanning Electron Microscope Imaging of Topographical and Chemical Contrast Using In-Lens, In-Column, and Everhart-Thornley Detector Systems.

The scanning electron microscope provides a platform for subnanometer resolution characterization of material morphology with excellent topographic and chemical contrast dependent on the used detectors. For imaging applications, the predominantly utilized signals are secondary electrons (SEs) and backscattered electrons (BSEs) that are emitted from the sample surface. Recent advances in detector technology beyond the traditional Everhart-Thornley geometry have enabled the simultaneous acquisition and discrimination of SE and BSE signals. This study demonstrates the imaging capabilities of a recently introduced new detector system that consists of the combination of two in-lens (I-L) detectors and one in-column (I-C) detector. Coupled with biasing the sample stage to reduce electron-specimen interaction volumes, this trinity of detector geometry allows simultaneous acquisition of signals to distinguish chemical contrast from topographical changes of the sample, including the identification of surface contamination. The I-C detector provides 4× improved topography, whereas the I-L detector closest to the sample offers excellent simultaneous chemical contrast imaging while not limiting the minimization of working distance to obtain optimal lateral resolution. Imaging capabilities and contrast mechanisms for all three detectors are discussed quantitatively in direct comparison to each other and the conventional Everhart-Thornley detector.

Toward a Smartphone Application for Estimation of Pulse Transit Time.

Pulse transit time (PTT) is an important physiological parameter that directly correlates with the elasticity and compliance of vascular walls and variations in blood pressure. This paper presents a PTT estimation method based on photoplethysmographic imaging (PPGi). The method utilizes two opposing cameras for simultaneous acquisition of PPGi waveform signals from the index fingertip and the forehead temple. An algorithm for the detection of maxima and minima in PPGi signals was developed, which includes technology for interpolation of the real positions of these points. We compared our PTT measurements with those obtained from the current methodological standards. Statistical results indicate that the PTT measured by our proposed method exhibits a good correlation with the established method. The proposed method is especially suitable for implementation in dual-camera-smartphones, which could facilitate PTT measurement among populations affected by cardiac complications.

Determination of Intermolecular Interactions Using Polarization Compensated Heteronuclear Overhauser Effect of Hyperpolarized Spins.

The nuclear Overhauser effect (NOE) has long been used as a selective indicator for intermolecular interactions. Due to relatively small changes of signal intensity, often on the order of several percent, quantitative NOE measurements can be challenging. Hyperpolarization of nuclear spins can dramatically increase the NOE intensity by increasing population differences, but poses its own challenge in quantifying the original polarization level. Here, we demonstrate a method for the accurate measurement of intermolecular heteronuclear cross-relaxation rates by simultaneous acquisition of signals from both nuclei. Using this method, we measure cross-relaxation rates between water protons and (19)F of trifluoroacetic acid at concentrations ranging from 23 to 72 mM. A concentration-independent value of 2.46 × 10(-4) ± 1.02 × 10(-5) s(-1) M(-1) is obtained at a temperature of 301 K and validated using a nonhyperpolarized measurement. In a broader context, accurate measurement of heteronuclear cross-relaxation rates may enable the study of intermolecular interactions including those involving macromolecules where (19)F atoms can be introduced as site-selective labels.

Super-resolution discrete Fourier transform spectroscopy beyond time-window size limitation using precisely periodic pulsed radiation

Fourier transform spectroscopy (FTS) has been widely used in a variety of fields in research, industry, and medicine due to its high signal-to-noise ratio, simultaneous acquisition of signals in a broad spectrum, and versatility for different radiation sources. Further improvement of the spectroscopic performance will widen its scope of applications. Here, we demonstrate improved spectral resolution by overcoming the time window limitation using discrete Fourier transform spectroscopy (dFTS) with precisely periodic pulsed terahertz (THz) radiation. Since infinitesimal resolution can be achieved at periodically discrete frequencies when the time window size is exactly matched to the repetition period T, a combination of THz-dFTS with a spectral interleaving technique achieves a spectral resolution only limited by the spectral interleaving interval. Linewidths narrower than 1/(50T) are fully resolved allowing the attribution of rotational-transition absorption lines of low-pressure molecular gases within a 1.25 MHz band. The proposed method represents a powerful tool to improve spectrometer performance and accelerate the practical use of various types of FTS.

Accuracy and Precision of Head Motion Information in Multi-Channel Free Induction Decay Navigators for Magnetic Resonance Imaging.

Free induction decay (FID) navigators were found to qualitatively detect rigid-body head movements, yet it is unknown to what extent they can provide quantitative motion estimates. Here, we acquired FID navigators at different sampling rates and simultaneously measured head movements using a highly accurate optical motion tracking system. This strategy allowed us to estimate the accuracy and precision of FID navigators for quantification of rigid-body head movements. Five subjects were scanned with a 32-channel head coil array on a clinical 3T MR scanner during several resting and guided head movement periods. For each subject we trained a linear regression model based on FID navigator and optical motion tracking signals. FID-based motion model accuracy and precision was evaluated using cross-validation. FID-based prediction of rigid-body head motion was found to be with a mean translational and rotational error of 0.14±0.21 mm and 0.08±0.13°, respectively. Robust model training with sub-millimeter and sub-degree accuracy could be achieved using 100 data points with motion magnitudes of ±2 mm and ±1° for translation and rotation. The obtained linear models appeared to be subject-specific as inter-subject application of a "universal" FID-based motion model resulted in poor prediction accuracy. The results show that substantial rigid-body motion information is encoded in FID navigator signal time courses. Although, the applied method currently requires the simultaneous acquisition of FID signals and optical tracking data, the findings suggest that multi-channel FID navigators have a potential to complement existing tracking technologies for accurate rigid-body motion detection and correction in MRI.

An integrated bioimpedance—ECG gating technique for respiratory and cardiac motion compensation in cardiac PET

Respiratory motion may degrade image quality in cardiac PET imaging. Since cardiac PET studies often involve cardiac gating by ECG, a separate respiratory monitoring system is required increasing the logistic complexity of the examination, in case respiratory gating is also needed. Thus, we investigated the simultaneous acquisition of both respiratory and cardiac gating signals using II limb lead mimicking electrode configuration during cardiac PET scans of 11 patients. In addition to conventional static and ECG-gated images, bioimpedance technique was utilized to generate respiratory- and dual-gated images. The ability of the bioimpedance technique to monitor intrathoracic respiratory motion was assessed estimating cardiac displacement between end-inspiration and -expiration. The relevance of dual gating was evaluated in left ventricular volume and myocardial wall thickness measurements. An average 7.6 ± 3.3 mm respiratory motion was observed in the study population. Dual gating showed a small but significant increase (4 ml, p = 0.042) in left ventricular myocardial volume compared to plain cardiac gating. In addition, a thinner myocardial wall was observed in dual-gated images (9.3 ± 1.3 mm) compared to cardiac-gated images (11.3 ± 1.3 mm, p = 0.003). This study shows the feasibility of bioimpedance measurements for dual gating in a clinical setting. The method enables simultaneous acquisition of respiratory and cardiac gating signals using a single device with standard ECG electrodes.

Multi-range sensors for the measurement of liquid film thickness distributions based on electrical conductance

The paper presents an approach toward an enhancement of the measuring range of high-speed sensors for the measurement of liquid film thickness distributions based on electrical conductance. This type of sensors consists of electrodes mounted flush to the wall. The sampling of the current generated between a pair of neighboring electrode is used as a measure of the film thickness. Such sensors have a limited measuring range, which is proportional to the lateral distance between the electrodes. The range is therefore coupled to the spatial resolution. The proposed new design allows an extension of the film thickness range by combining electrode matrices of different resolution in one and the same sensor. In this way, a high spatial resolution is reached with a small thickness range, whereas a film thickness that exceeds the range of the high resolution measurement can still be acquired even though on the costs of a lower spatial resolution. A simultaneous signal acquisition with a sampling frequency of 3.2kHz combines three measuring ranges for the characterization of a two-dimensional film thickness distribution: (1) thickness range 0–600µm, lateral resolution 2×2mm2, (2) thickness range 400–1300µm, lateral resolution 4×4mm2, and (3) thickness range 1000–3500µm, lateral resolution 12×12mm2. The functionality of this concept sensor is demonstrated by tests in a horizontal wavy stratified air–water flow at ambient conditions. Using flexible printed circuit board technology to manufacture the sensor makes it possible to place the sensor at the inner surface of a circular pipe.

Optical mapping of optogenetically shaped cardiac action potentials.

Light-mediated silencing and stimulation of cardiac excitability, an important complement to electrical stimulation, promises important discoveries and therapies. To date, cardiac optogenetics has been studied with patch-clamp, multielectrode arrays, video microscopy, and an all-optical system measuring calcium transients. The future lies in achieving simultaneous optical acquisition of excitability signals and optogenetic control, both with high spatio-temporal resolution. Here, we make progress by combining optical mapping of action potentials with concurrent activation of channelrhodopsin-2 (ChR2) or halorhodopsin (eNpHR3.0), via an all-optical system applied to monolayers of neonatal rat ventricular myocytes (NRVM). Additionally, we explore the capability of ChR2 and eNpHR3.0 to shape action-potential waveforms, potentially aiding the study of short/long QT syndromes that result from abnormal changes in action potential duration (APD). These results show the promise of an all-optical system to acquire action potentials with precise temporal optogenetics control, achieving a long-sought flexibility beyond the means of conventional electrical stimulation.

Poster — Thur Eve — 18: Cherenkov Emission By High‐Energy Radiation Therapy Beams: A Characterization Study

We investigate Cherenkov emission (CE) by radiotherapy beams via radiation dose‐versus‐CE correlation analyses, CE detection optimization by means of a spectral shift towards the near‐infrared (NIR) window of biological tissue, and comparison of CE to on‐board MV imaging. Dose‐CE correlation was investigated via simulation and experiment. A Monte Carlo (MC) CE simulator was designed using Geant4. Experimental phantoms include: water; tissue‐simulating phantom composed of water, Intralipid®, and beef blood; plastic phantom with solid water insert. The detector system comprises an optical fiber and diffraction‐grating spectrometer incorporating a front/back‐illuminated CCD. The NIR shift was carried out with CdSe/ZnS quantum dots (QDs), emitting at (650±10) nm. CE and MV images were acquired with a CMOS camera and electronic portal imaging device.MC and experimental studies indicate a strong linear dose‐CE correlation (Pearson coefficient > 0.99). CE by an 18‐MeV beam was effectively NIR‐shifted in water and a tissue‐simulating phantom, exhibiting a significant increase at 650 nm for QD depths up to 10 mm. CE images exhibited relative contrast superior to MV images by a factor of 30. Our work supports the potential for application of CE in radiotherapy online imaging for patient setup and treatment verification, since CE is intrinsic to the beam and non‐ionizing and QDs can be used to improve CE detectability, potentially yielding image quality superior to MV imaging for the case of low‐density‐variability, low‐optical‐attenuation materials (ex: breast/oropharynx). Ongoing work involves microenvironment functionalization of QDs and application of multi‐channel spectrometry for simultaneous acquisition of dosimetric and tumor oxygenation signals.

20: Targeted Gold Nanoparticles as Vascular Disrupting Agents during Radiotherapy

towards the near-infrared (NIR) window of biological tissue, and in tissues of low density variability and low optical attenuation, such as breast or oropharyngeal cavities, it can provide contrast superior to MV imaging. Materials/Methods: Dose-CE correlation was investigated via both simulation and experiment. A Monte Carlo (MC) CE simulator was designed using Geant4. Experimental phantoms include: a water tank; a tissue-simulating phantom composed of water, a fat emulsion, and beef blood; and a Poly(methyl methacrylate) (PMMA) phantom with a solid insertion radiologically equivalent to water. The optical spectrometry system consists of a multi-mode optical fiber, connected to a diffraction grating spectrometer incorporating a frontor back-illuminated chargecoupled device (CCD). CdSe/ZnS core-shell quantum dots (QDs), emitting at (650 10) nm, were used to achieve a NIR shift of the CE signal. CE and MV images were acquired with a complementary metal-oxide-semiconductor (CMOS) camera and an amorphous silicon electronic portal imaging device (EPID), respectively. Results: MC analyses indicate a strong linear correlation between radiation dose and CE (Pearson coefficient r > 0.99). Dose-CE correlation was investigated experimentally via water tank ion chamber and optical fiber scans. The effective points of measurement of dose by our optical system for 18, 12, and 6 MeV clinical electron beams were at 1.7, 0.8, and 0.1 cm, respectively, downstream from the fiber axis (r > 0.99). CE by an 18 MeV beam was effectively shifted toward 650 nm in a water tank, confirming its capacity to stimulate CdSe/ZnS photoluminescence, and in a tissuesimulating phantom, exhibiting a 30% increase at QD depths of w3 mm. CE images exhibited 30x better relative contrast than EPID images. Conclusions: Our work validates the potential for application of CE in RT online imaging for patient setup and treatment verification, since CE is intrinsic to the beam and non-ionizing and QDs can be used to improve CE detectability, yielding image quality superior to MV imaging for the case of a low density variability and low optical attenuation material, which is the case for breast or oropharyngeal cavities. Future work involves modification of QDs to capture microenvironment parameters and the use of a multi-channel spectrometer for simultaneous acquisition of dosimetric and tumor oxygenations signals. Author Disclosure: Y. Zlateva: None. N. Quitoriano: None. S. Davis: None. I. El Naqa: None.

An Innovative Strategy for Correctly Interpreting Simultaneous Acquisition of EEG Signals and FMRI Images

Cognitive event-related measurements of the human brain are performed by measuring electrical signals and electromagnetic fields (electroencephalography, EEG, and magnetoencephalography, MEG) and hemodynamic responses (measured by fMRI and PET). The EEG and MEG reflect synchronized electrical activity of neurons, and then show the same timescale as neurocognitive processes. The fMRI is related to the power consumption of groups of neurons and registers a signal on a timescale of several seconds. Unlike fMRI, MEG and EEG are not imaging methods. It is our opinion that the combination of MEG or EEG with the fMRI therefore would be very useful to reach a high resolution, both in time and space, of brain functions. It is not assured however that all measured events during an EEG acquisition and cognitive process-related produce measurable changes of the BOLD signal-and vice versa. In this paper, a new strategy of combining signals (electric and hemodynamic responses) simultaneously acquired from different clinical methodologies is performed and tested in order to produce more reliable information about brain activity. Two different algorithms are explored and compared via repeatability standard deviation estimations of fMRI images.

Monitoring intracellular oxidative events using dynamic spectral unmixing microscopy

There is increasing interest in using live cell imaging to monitor not just individual intracellular endpoints, but to investigate the interplay between multiple molecular events as they unfold in real time within the cell. A major impediment to simultaneous acquisition of fluorescent signals from multiple probes is that emission spectra of many fluorophores overlap, often with maxima that are only a few nanometers apart. Spectral acquisition of mixed fluorescence signals captured within a dedicated scanning range can be used to quantitatively separate signals into component spectra. We report here the development of a novel live cell application of spectral unmixing for the simultaneous monitoring of intracellular events reported by closely-emitting fluorophores responding dynamically to external stimuli. We validate the performance of dynamic spectral unmixing microscopy (DynSUM) using genetically encoded sensors to simultaneously monitor changes in glutathione redox potential (Egsh) and H2O2 production in living cells exposed to oxidizing and reducing agents. We further demonstrate the utility of the DynSUM approach to observe the relationship between the increases in Egsh and H2O2 generation induced in airway epithelial cells exposed to an environmental electrophile.

Simulation of A/D Conversion with LabView

Simulation technology was a very important technology in the parallel signal processing research. A type of antomatic controlling simulation system was introduced, which was built by taking LabVIEW as the software platform, using LabVIEW user interface interacting with the Simulink model. Simulation of processing often requires algorithm and performance evaluation of parallel environment. Signal processing often requires simultaneous acquisition of multi-channel analog signals. Taking dual-channel A/D conversion processes as an example, using LabVIEW with VC, it achieves a simulation of parallel signal process of A/D conversion process.

Compressive Imaging - Image Sensing with Simultaneous Compression and Acquisition of Signals -

Compressive Imaging - Image Sensing with Simultaneous Compression and Acquisition of Signals -

Bioimpedance-based measurement method for simultaneous acquisition of respiratory and cardiac gating signals

Respiratory and cardiac motion artefacts impair the quality and reliability of medical imaging, particularly in nuclear medicine. At worst, the interpretation of distorted images may lead to inadequate or unnecessary treatment. Image artefacts can be minimized by gating the image acquisition according to respiratory phase and cardiac contractions. However, currently there are no clinically established dual-gating methods in nuclear medicine imaging. The aim of this study is to validate a previously determined optimized bioimpedance measurement configuration against traditional respiratory and cardiac measurement systems in 12 volunteers. High agreement and excellent correlations (r = 0.944–0.999) were found between respiratory peak-to-peak amplitudes as well as temporal respiratory and cardiac intervals. Above all, good quality respiratory and cardiac gating signals were obtained from all test subjects with a fairly regular sinus rhythm. Importantly, both signals were acquired simultaneously with a single device. Due to the simplicity of this inexpensive method, the technique has high potential to be adopted for dual-gating in clinical practice in the future.

Quantification of venous vessel size in human brain in response to hypercapnia and hyperoxia using magnetic resonance imaging

Hypercapnia and hyperoxia give rise to vasodilation and vasoconstriction, respectively. This study investigates the influence of hypercapnia and hyperoxia on venous vessel size in the human brain. Venous vessel radii were measured in response to hypercapnia and hyperoxia. The venous vessel radii were determined by calculation of the changes in R2 * and R2 that are induced by breathing 6% CO2 or pure oxygen. The experimental paradigm consisted of two 3-min intervals of inhaling 6% CO2 or 100% O2 interleaved with three 2-min intervals of breathing air. Hypercapnic and hyperoxic experiments were performed on eight subjects on a 3T scanner. Parametric maps of mean venous vessel radius were calculated from the changes in R2 * and R2 , which were measured by simultaneous acquisition of gradient-echo and spin-echo signals. The mean venous vessel radii in hypercapnia were 7.3±0.3 μm in gray matter and 6.6±0.5 μm in white matter. The corresponding vessel radii in hyperoxia were 5.6±0.2 μm in gray matter and 5.4±0.2 μm in white matter. These results show that the venous vessel radius was larger in hypercapnia than that in hyperoxia in both gray matter and white matter (P<0.005), which agrees with the hypothesis that hypercapnia causes vasodilation and hyperoxia induces vasoconstriction.