Root Mean Square Noise Research Articles

High-speed bioimpedance-based gating system for radiotherapy: Prototype and proof of principle.

To investigate a novel bioimpedance-based respiratory gating system (BRGS) designed for external beam radiotherapy and to evaluate its technical characteristics in comparison with existing similar systems. The BRGS was tested on three healthy volunteers in free breathing and breath-hold patterns under laboratory conditions. Its parameters, including the time delay (TD) between the actual impedance change and the gating signal, temperature drift, root mean square (RMS) noise, and signal-to-noise ratio (SNR), were measured and analyzed. The gate-on TD and the gate-off TD were found to be 9.0±2.0ms [mean±standard deviation (M±SD)] and 7.2±1.3ms, respectively. The temperature drift of the BRGS output signal was 0.02 Ω after 30 min of operation. RMS noise averaged 0.14±0.05 Ω (M±SD) for all subjects and varied from 0.08 to 0.20 Ω with repeated measurements. A significant difference in SNR (p<0.001) was observed between subjects, ranging from 4 to 15. The evaluated bioimpedance-based gating system showed a high performance in real-time respiratory monitoring and may potentially be used as an external surrogate guidance for respiratory-gated external beam radiotherapy. Direct comparison with commercially available systems, 4D correlation studies, and expansion of the patient sample are goals for future preclinical studies.

RFSoC-based front-end electronics for pulse detection

Radiation measurement relies on pulse detection, which can be performed using various configurations of high-speed analog-to-digital converters (ADCs) and field-programmable gate arrays (FPGAs). For optimal power consumption, design simplicity, system flexibility, and the availability of DSP slices, we consider the Radio Frequency System-on-Chip (RFSoC) to be a more suitable option than traditional setups. To this end, we have developed custom RFSoC-based electronics and verified its feasibility. The ADCs on RFSoC exhibit a flat frequency response of 1–125 MHz. The root-mean-square (RMS) noise level is 2.1 ADC without any digital signal processing. The digital signal processing improves the RMS noise level to 0.8 ADC (input equivalent 40 μVrms). Baseline correction via digital signal processing can effectively prevent photomultiplier overshoot after a large pulse. Crosstalk between all channels is less than -55 dB. The measured data transfer speed can support up to 32 kHz trigger rates (corresponding to 750 Mbps). Overall, our RFSoC-based electronics are highly suitable for pulse detection, and after some modifications, they will be employed in the Kamioka Liquid Scintillator Anti-Neutrino Detector (KamLAND).

Model-based deep CNN-regularized reconstruction for digital breast tomosynthesis with a task-based CNN image assessment approach

Objective. Digital breast tomosynthesis (DBT) is a quasi-three-dimensional breast imaging modality that improves breast cancer screening and diagnosis because it reduces fibroglandular tissue overlap compared with 2D mammography. However, DBT suffers from noise and blur problems that can lower the detectability of subtle signs of cancers such as microcalcifications (MCs). Our goal is to improve the image quality of DBT in terms of image noise and MC conspicuity. Approach. We proposed a model-based deep convolutional neural network (deep CNN or DCNN) regularized reconstruction (MDR) for DBT. It combined a model-based iterative reconstruction (MBIR) method that models the detector blur and correlated noise of the DBT system and the learning-based DCNN denoiser using the regularization-by-denoising framework. To facilitate the task-based image quality assessment, we also proposed two DCNN tools for image evaluation: a noise estimator (CNN-NE) trained to estimate the root-mean-square (RMS) noise of the images, and an MC classifier (CNN-MC) as a DCNN model observer to evaluate the detectability of clustered MCs in human subject DBTs. Main results. We demonstrated the efficacies of CNN-NE and CNN-MC on a set of physical phantom DBTs. The MDR method achieved low RMS noise and the highest detection area under the receiver operating characteristic curve (AUC) rankings evaluated by CNN-NE and CNN-MC among the reconstruction methods studied on an independent test set of human subject DBTs. Significance. The CNN-NE and CNN-MC may serve as a cost-effective surrogate for human observers to provide task-specific metrics for image quality comparisons. The proposed reconstruction method shows the promise of combining physics-based MBIR and learning-based DCNNs for DBT image reconstruction, which may potentially lead to lower dose and higher sensitivity and specificity for MC detection in breast cancer screening and diagnosis.

Ensuring fair assessment of solid-state nanopore sensors with reporting baseline current

In developing solid-state nanopore sensors for single molecule detection, comprehensive evaluation of the nanopore quality is important. Existing studies typically rely on comparing the noise root mean square or power spectrum density values. Nanopores exhibiting lower noise values are generally considered superior. This evaluation is valid when the single molecule signal remains consistent. However, the signal can vary, as it is strongly related to the solid-state nanopore size, which is hard to control during fabrication consistently. This work emphasized the need to report the baseline current for evaluating solid-state nanopore sensors. The baseline current offers insight into several experimental conditions, particularly the nanopore size. Our experiments show that a nanopore sensor with more noise is not necessarily worse when considering the signal-to-noise ratio (SNR), particularly when the pore size is smaller. Our findings suggest that relying only on noise comparisons can lead to inaccurate evaluations of solid-state nanopore sensors, considering the inherent variability in fabrication and testing setups among labs and measurements. We propose that future studies should include reporting baseline current and sensing conditions. Additionally, using SNR as a primary evaluation tool for nanopore sensors could provide a more comprehensive understanding of their performance.

Readout Electronics for the Zero Degree Calorimeter at HIRFL-CEE Experiment

The CSR External-target Experiment (CEE) at the Heavy Ion Research Facility at Lanzhou (HIRFL) will be the first GeV large-scale nuclear physics experiment developed independently in China. The primary physics goal of the CEE is to study the nuclear equation of state, hyper nuclei, and radioactive ion beam physics. The Zero Degree Calorimeter (ZDC) of CEE measures the centrality and reaction plane of the nuclear-nuclear collision relative to the hadron background. It consists of 192 roughly trapezoidal Plastic Scintillator (PS) crystal blocks coupled with PMT (Photo Multiplier Tube) to convert charged particles into electrical signals. The readout electronics consists of 12 FEE (Front End Electronics), the sub-trigger module, and the sub-clock module. In addition, one HV (High Voltage) crate provides a high voltage power supply for the PMTs. According to the electrical test on the electronics, the RMS (Root Mean Square) noise is less than 0.4 mV, and the nonlinearity is less than 0.06%. The heavy-ion beam test shows that the ZDC can measure particles up to Z=7, which meets the physics requirements.

Impacts of different reconstruction methods on the image quality of cadmium-zinc-telluride-based single photon emission computed tomography/computed tomography pulmonary perfusion imaging.

The objective was to evaluate the impacts of different reconstruction methods [filtered back projection (FBP) and ordered subset expectation maximization (OSEM)] and different filters (Butterworth filter and Gaussian filter) on the image quality in cadmium-zinc-telluride (CZT)-based single photon emission computed tomography (SPECT)/computed tomography (CT) pulmonary perfusion imaging. A combinations including FBP with Butterworth filter, OSEM with Butterworth filter (OSEM + Butterworth filter ), and OSEM with Gaussian filter (OSEM + Gaussian filter) were used during SPECT image reconstruction. Visual and quantitative parameters [root mean square (RMS) noise, contrast and contrast-to-noise ratio (CNR)] were used to evaluate image quality. The OSEM + Gaussian filter had better RMS noise and CNR than those of the FBP + Butterworth filter or OSEM + Butterworth filter, while the OSEM + Butterworth filter had the best contrast. The highest visual scores were obtained by OSEM + Gaussian filter ( P < 0.0001). In the lesion size <2 cm group, the contrast ( P < 0.01) and visual scores ( P < 0.001) of OSEM + Butterworth filter were better than those of the other two groups. In the lesion size ≥2 cm group, the RMS noise and visual scores of OSEM + Gaussian filter were better than those of the other two groups. In CZT SPECT/CT pulmonary perfusion imaging, this study recommended the clinical use of the OSEM + Gaussian filter combination for reconstruction in both conventional and larger lesions, the OSEM + Butterworth filter image postprocessing method might be advantageous in small lesions.

Optimization of image reconstruction method of cerebral blood flow perfusion imaging with digital CZT SPECT.

The purpose of this study is to evaluate the effects of filtered back projection (FBP), ordered subset expectation maximisation (OSEM), and different filters on cadmium zinc telluride single-photon emission computed tomography [CZT single-photon emission computed tomography (SPECT)] cerebral blood perfusion image quality to optimise the image reconstruction method. Under routine clinical conditions, tomographic imaging was performed on the phantom and patients. Image processing included image reconstruction using FBP and OSEM, and the filtering method used Butterworth (Bw) and Gaussian (Gs) filters. Visual and semi-quantitative parameters [integral uniformity, root mean square (RMS) noise and contrast and contrast-to-noise ratio (CNR)] were used to evaluate image quality to optimise image reconstruction parameters. One-way and two-way analysis of variance were used to process phantom and clinical data. In the tomographic images of the phantom, the semi-quantitative analysis showed that the integral uniformity of FBP+Bw was better than that of OSEM+Bw and OSEM+Gs (P < 0.05), and that the RMS noise of FBP+Bw was lower than that of OSEM+Bw and OSEM+Gs (P < 0.001). The contrast of FBP+Bw and OSEM+Bw in the cold area diameter ≥2 cm group was higher than that of OSEM+Gs (P < 0.001), whereas the CNR of FBP+Bw was higher than that of OSEM+Bw and OSEM+Gs (P < 0.001); the contrast of OSEM+Bw cold area diameter <2 cm was higher than that of FBP+Bw (P < 0.01). The semi-quantitative analysis results of the clinical images were consistent with the phantom's. In CZT SPECT cerebral blood flow perfusion imaging, it is suggested that the image postprocessing method of FBP+Bw (fc = 0.40; n = 10) should be used routinely in clinical application, and if there are uncertain small lesions in the processed image, it is suggested to use the reconstruction method of OSEM+Bw (EM-equivalent iterations = 60; fc = 0.45; n = 10) instead.

Magnetic Flux Density Superposition in Nonlinear Anisotropic Ferromagnetic Material and Resulting Magnetic Barkhausen Noise

Tetrapole probes, also known as double-core probes, which consist of two pairs of orthogonal electromagnets, apply orthogonal magnetic fields to the surface of a ferrous sample and rotate the field by superposition of these fields. Tetrapole probes have the potential to perform rapid characterization of the magnetic anisotropy of ferromagnetic materials. Conventional understanding dictates that magnetic field superposition is linear. However, superposition in ferromagnetic materials is inherently nonlinear. In this work, an equation for the magnetic flux density generated by superposition of orthogonal fields from a tetrapole probe in a ferromagnetic, anisotropic, single net easy-axis material, is derived, along with an equation for magnetic Barkhausen noise root mean square (rms) and energy, for application to materials with flat surfaces. The model approximates the nonlinear superposition as cubic, inline with analogous optics results, and is accurate for low applied fields. Data, which are accurately fit with the model, are shown. The model facilitates useful analyses of measurements made by tetrapole probes and addresses the inherent nonlinearity of magnetic fields applied to ferromagnetic materials.

Sapphire-supported nanopores for low-noise DNA sensing

Solid-state nanopores have broad applications from single-molecule biosensing to diagnostics and sequencing. The high capacitive noise from conventionally used conductive silicon substrates, however, has seriously limited both their sensing accuracy and recording speed. A new approach is proposed here for forming nanopore membranes on insulating sapphire wafers to promote low-noise nanopore sensing. Anisotropic wet etching of sapphire through micro-patterned triangular masks is used to demonstrate the feasibility of scalable formation of small (<25 μm) membranes with a size deviation of less than 7 μm over two 2-inch wafers. For validation, a sapphire-supported (SaS) nanopore chip with a 100 times larger membrane area than conventional nanopores was tested, which showed 130 times smaller capacitance (10 pF) and 2.6 times smaller root-mean-square (RMS) noise current (18–21 pA over 100 kHz bandwidth, with 50–150 mV bias) when compared to a silicon-supported (SiS) nanopore (~1.3 nF, and 46–51 pA RMS noise). Tested with 1k base-pair double-stranded DNA, the SaS nanopore enabled sensing at microsecond speed with a signal-to-noise ratio of 21, compared to 11 from a SiS nanopore. This SaS nanopore presents a manufacturable nanoelectronic platform feasible for high-speed and low-noise sensing of a variety of biomolecules.

Low Noise VCSEL Driver for SERF Atomic Magnetometer

A new type of VCSEL (Vertical-Cavity Surface-Emitting Laser) which uses Pt1000 as a temperature sensitive component and non-magnetic heating membrane as a temperature actuator is designed for SERF (Spin-Exchange Relation-Free) atomic magnetometer, which can decrease the magnetic interference produced while heating or cooling VCSEL. Therefore a low noise driver for this kind of VCSEL is necessary. A driver for the novel VCSEL is designed in this paper. The output current is adjustable from 0 to 4.5 mA, and RMS (Root Mean Square) noise of current is less than 80 nA. The operating temperature of the VCSEL is adjustable between 30-110 °C and RMS noise of temperature is less than 0.6 mK. So that it can be ensured that the VCSEL outputs a laser with stable optical power and wavelength.

Emission and vibration characteristics of Niger seed oil biodiesel fueled diesel engine

The present investigation dwells the experimental investigation for the assessment of emission, vibration, and noise parameters of single-cylinder, DI diesel engine functioning through the blends of conventional diesel and Niger seed oil methyl ester (NSOME) at different engine operating loads namely 25%, 50%, 75%, and 100% at a constant speed. The carbon monoxide (CO), unburnt hydrocarbons (UHC), and smoke opacity emissions have come down significantly for all the blends of NSOME namely B10, B20, and B40 while the NOx increased marginally. Besides, the vibration and noise extremity of the engine was lowered while operating with biodiesel blends as compared to conventional diesel. B20 has specified a significant reduction in emission, vibration, and noise too at all the loads range from minimum to maximum. At maximum load condition the CO, UHC, smoke opacity, root mean square (RMS) velocity, and RMS noise of B20 have reduced by 93.9%, 37.87%, 5.54%, 45.78%, and 26.15% respectively even as the NOx was increased by 12.76% compared to standard.

Noise in nanopore sensors: Sources, models, reduction, and benchmarking

Label-free nanopore sensors have emerged as a new generation technology of DNA sequencing and have been widely used for single molecule analysis. Since the first α-hemolysin biological nanopore, various types of nanopores made of different materials have been under extensive development. Noise represents a common challenge among all types of nanopore sensors. The nanopore noise can be decomposed into four components in the frequency domain (1/f noise, white noise, dielectric noise, and amplifier noise). In this work, we reviewed and summarized the physical models, origins, and reduction methods for each of these noise components. For the first time, we quantitatively benchmarked the root mean square (RMS) noise levels for different types of nanopores, demonstrating a clear material-dependent RMS noise. We anticipate this review article will enhance the understanding of nanopore sensor noises and provide an informative tutorial for developing future nanopore sensors with a high signal-to-noise ratio.

Factors influencing assessment in a TDC-based ranging system

Light detection and ranging (LiDAR), based on a time-to-digital converter (TDC) is an important technique for measuring the distance between a laser transmitter and its target. It is known that by decreasing the probability of trigger error, ranging precision will be improved. Based on a lab-designed APD detection circuit, noise analysis was deduced. Based on statistics and probability theory, the relationships among the probability of noise trigger error, reference voltage and noise were established. Then a given desired error probability (estimated via theoretical time jitter), the reference voltage of a TDC-based ranging system, can be properly designed based on the root mean square (RMS) noise. Extensive simulation and experimental results indicated that the reference voltage involved in a lab-scale TDC-based ranging system should be set to larger than five times RMS noise for an acceptable error probability of 0.01%. Thus, reasonable circuit parameter design can decrease time jitter, reduce the likelihood of noise trigger error, and further improve the ranging precision of a LiDAR system.

Characterizing the Seasonal Hydrological Loading Over the Asian Continent Using GPS, GRACE, and Hydrological Model

Based on combined data of the Global Positioning System (GPS), Global Land Data Assimilation System (GLDAS), and Gravity Recovery and Climate Experiment (GRACE), the seasonal hydrological loading over the Asian continent is characterized in this study. The hydrological loading effects over the Asian continent display strong latitude dependence. The significant hydrological loading effects appear at the GPS stations situated in the coastal areas, some regions near large rivers and lakes, and high-latitude areas in Russia, as evidenced by the fact that a large root mean square (RMS) and high percentage of the variance related to the annual signal modeled by singular spectrum analysis (SSA) for each measurement are cumulated at the stations located in these regions. In contrast, the hydrological loading effects are not pronounced in mid-latitude areas of the Asian continent (e.g., Central Asia, northern and plateau regions of China), which is due to the high topographical variability and scarce water resources in these regions. Then, the cross wavelet transform (XWT) is used to quantify the consistency between different data sets. For the data sets of GPS/GLDAS, the XWT-based semblance for 64% of the stations reaches above 0.8, while it reaches above 0.8 for 48% for the data sets of GPS/GRACE, indicating that the data sets of GPS/GLDAS present better consistency. In addition, we also discuss the effects of hydrological loading on GPS observations from the RMS value, noise characteristic, and velocity uncertainty. After applying the hydrological loading correction, the RMS values of almost all GPS observations are reduced with different amplitudes, implying that the hydrological loading correction can reduce the RMS values of most GPS observations in the Asian continent. Meanwhile, the variations of noise and velocity uncertainty suggest that hydrological loading has changed the noise characteristic of almost all GPS observations, and thus lead to the overestimation of velocity uncertainty.

A charge amplifier with noise peaking suppression and gain drop compensation utilizing a Quasi-Miller RC network

A charge amplifier with noise peaking suppression and gain drop compensation is proposed. By utilizing the proposed Quasi-Miller RC network, the noise peaking is suppressed and gain drop is compensated, which alleviates the design trade-off between charge gain and output root-mean-square (RMS) noise, therefore obtains an improved sensitivity. Meanwhile, the Quasi-Miller RC network permits the charge amplifier to support ultra-low frequency operation without using a huge resistor, which is normally required by the charge amplifier. The fabricated charge amplifier demonstrates an input-referred RMS noise charge of 909 aC, a charge gain of 10.2 V/pC and a 3-dB bandwidth from 80 Hz to 38 MHz. Low noise and high charge gain are obtained simultaneously. Meanwhile, extremely low cut-off frequency is also obtained, which is beneficial to maintain the signal integrity.

Fast Padé transform for increasing the signal to noise ratio of spectra provided by STEAM pulse sequence.

There are two routine pulse-sequences for single voxel spectroscopy (SVS), point resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM). Although STEAM has several advantages in comparison to PRESS, signal/noise ratio (SNR) superiority of PRESS makes it the first choice for SVS. Application of fast Padé transform (FPT) instead of Fast Furrier transform (FFT) might increase the SNR of the signal produced by STEAM pulse-sequence and therefore allows the benefits of its advantages. We aimed to evaluate and compare the noise root mean square (RMS) and SNR provided by STEAM pulse-sequence using both FPT and FFT. A gelatin-based phantom was constructed in a 19-cm acrylic cylinder. The phantom had two normal/tumoral parts. The SVS was performed using a 3T MRI scanner. STEAM pulse-sequence were used with the following parameters: TR = 2000ms, TM = 10ms, and three TEs of 20, 135 and 270ms with two data-points of 1024 and 512 and voxel-size of 1cm3. The raw data were extracted and processed using both FFT and FPT estimators to produce the spectrum. The noise RMS and SNR of Cho and Cr metabolites were assessed. According to the results, noise RMS of spectra provided by FPT were decreased between 3619.01-14252.94% in comparison to FFT (p< 0.00001). The SNR of Cr1 and Cho peaks of the spectra provided by FPT were increased more than 96.80 and 97.18, respectively (0.00006 <p< 0.02). The difference of noise RMS's provided by FPT are thousands percent less than FFT. This enormous decrease in noise provides a good increase of SNR. While the range of Cr1 and Cho SNR by FFT are between 41.55-120.32 the range of SNRs of these peaks provided by FPT are between 1719.99-9744.79, which implies a significant difference between the efficiency of FPT and FFT. This study showed that application of FPT in comparison to FFT can increase the spectra SNR and so that its usage can be helpful during the application of STEAM pulse-sequence which results in lower SNR in comparison to PRESS pulse-sequence. Thus, we should make use of the advantages of STEAM pulse-sequence.

A wide band, low direct current drift, low noise preamplifier for a quadrupole mass spectrometer.

In order to measure the low current in the quadrupole mass spectrometer (QMS), we design a novel wide band composite trans-impedance preamplifier. The noise filtering components, which built in the feedback loop of the preamplifier, are designed to reduce the noise of two-stage amplifiers. By using the package with low thermal resistance factor, reducing the power consumption of preamplifiers and reducing the feedback resistance, the temperature drift of baseline signal is reduced. Compared with the traditional composite preamplifier, the novel preamplifier reduces maximum temperature drift amplitude and reduces root mean square of noise. At last, the environmental reliability of QMS detection was improved.

Шумовые характеристики оптического отклика феррожидкостей на воздействие магнитного поля

The noise, produced by different ferrofluidic samples under their probing by optical fiber method, investigated. It is shown that the magnetic field switching on leads to its significant enhancement, which presumably connected with fluctuations, accompanying the process of aggregates formation. The dependencies of root mean square value of the noise on the field strength and the probing light intensity are obtained. The slow decrease of the noise root mean square value after the field switching off, reflecting the field formatted aggregates relaxation, revealed.

Unintentional Movements During the Use of Vitreoretinal Forceps.

PurposeIntraocular forceps used in vitreoretinal surgery are actuated by squeezing their handles. We studied the relationship between actuation and any accompanying unintentional movements of the instrument tip, and compared different handle designs and gauges.MethodsOptical sensors were used to measure involuntary movements of forceps tips while monitoring the extent of actuation. Mean root mean square (RMS) and ranges of signals obtained from sensors were computed before and after applying high (7–13 Hz) and low (<5 Hz) frequency filters. Four handle designs, two gauge sizes, and two users were compared to each other.ResultsIn the absence of human contact, mean RMS of noise was 6.47 μ and mean range was 21.67 μ. When the forceps were held by the surgeon but kept motionless (no actuation), mean RMS was 58.01 μ and mean range was 156.66 μ. When the forceps were actuated, mean RMS was 214.71 μ and mean range was 566.11 μ. The differences were statistically significant (P < 0.001). The process of actuation by both users was positively correlated with unintentional movements mainly at low frequencies. No statistically significant differences were found between users and between two gauges (23 and 27) at mixed and low frequencies. Pneumatic handles showed less RMS and range values at higher frequencies compared to conventional handle designs. Eliminating human error by fixing pneumatic forceps to the model did not reduce unintentional movements, but eliminated their correlation with actuation.ConclusionsActuating forceps was associated directly with increased unintentional low frequency movements at the tip of the forceps when held by hand.Translational RelevanceA novel system of measuring unintentional forceps tip movement during actuation is described which could be used to guide improved design.

Multispectral phase imaging based on acousto-optic filtration of interfering light beams [Invited

Acousto-optic spectral selection of light is an effective technique for interference imaging at multiple wavelengths. In this paper, we show that, depending on the location of the acousto-optical tunable filter relative to the interferometer, it is possible to enhance important characteristics of the whole system: spectral contrast, insensitivity to ambient light, performance stability, and measurement accuracy. We analyze theoretically and compare experimentally a quantitative phase imaging system based on a Mach-Zehnder interferometer with one and two acousto-optical filters located in the illumination or/and in the output channels. Visibility of the interference patterns and noise root mean square in the calculated phase maps are estimated for all cases at room temperature. It is shown that acousto-optic filtration of interfering light beams in the output channel ensures better contrast of the interference pattern and, therefore, provides better stability and higher precision of the phase measurements.