Fiducial Signal Research Articles

Fiducial visibility on planar images during motion-synchronized tomotherapy treatments

Objective. Synchrony® is a motion management system on the Radixact® that uses planar kV radiographs to locate the target during treatment. The purpose of this work is to quantify the visibility of fiducials on these radiographs. Approach. A custom acrylic slab was machined to hold 8 gold fiducials of various lengths, diameters, and orientations with respect to the imaging axis. The slab was placed on the couch at the imaging isocenter and planar radiographs were acquired perpendicular to the custom slab with varying thicknesses of acrylic on each side. Fiducial signal to noise ratio (SNR) and detected fiducial position error in millimeters were quantified. Main Results. The minimum output protocol (100 kVp, 0.8 mAs) was sufficient to detect all fiducials on both Radixact configurations when the thickness of the phantom was 20 cm. However, no fiducials for any protocol were detected when the phantom was 50 cm thick. The algorithm accurately detected fiducials on the image when the SNR was larger than 4. The MV beam was observed to cause RFI artifacts on the kV images and to decrease SNR by an average of 10%. Significance. This work provides the first data on fiducial visibility on kV radiographs from Radixact Synchrony treatments. The Synchrony fiducial detection algorithm was determined to be very accurate when sufficient SNR is achieved. However, a higher output protocol may need to be added for use with larger patients. This work provided groundwork for investigating visibility of fiducial-free solid targets in future studies and provided a direct comparison of fiducial visibility on the two Radixact configurations, which will allow for intercomparison of results between configurations.

Presupernova Neutrinos: Directional Sensitivity and Prospects for Progenitor Identification

Abstract We explore the potential of current and future liquid scintillator neutrino detectors of kt mass to localize a presupernova neutrino signal in the sky. In the hours preceding the core collapse of a nearby star (at distance kpc), tens to hundreds of inverse beta decay events will be recorded, and their reconstructed topology in the detector can be used to estimate the direction to the star. Although the directionality of inverse beta decay is weak (∼8% forward−backward asymmetry for currently available liquid scintillators), we find that for a fiducial signal of 200 events (which is realistic for Betelgeuse), a positional error of ∼60° can be achieved, resulting in the possibility to narrow the list of potential stellar candidates to less than 10, typically. For a configuration with improved forward−backward asymmetry (∼40%, as expected for a lithium-loaded liquid scintillator), the angular sensitivity improves to ∼15°, and—when a distance upper limit is obtained from the overall event rate—it is in principle possible to uniquely identify the progenitor star. Any localization information accompanying an early supernova alert will be useful to multimessenger observations and to particle physics tests using collapsing stars.

Optimizing Coded Aperture Imaging techniques to allow for online tracking of fiducial markers with high-energy scattered radiation from treatment beam.

Real-time visualization of target motion using fiducial markers during radiation therapy treatment will allow for more accurate dose delivery. The purpose of this study was to optimize techniques for online fiducial marker tracking by detecting the scattered treatment beam through coded aperture imaging (CAI). Coded aperture imaging is a novel imaging technique that can allow target tracking in real time during treatment, and do so without adding any additional radiation dose, by making use of the scattered treatment beam radiation. Radiotherapy beams of various energies, incident on phantoms containing gold fiducial markers were modeled using MCNP6.2 Monte Carlo transport code. Orthogonal scatter radiographs were collected through a CAI geometry. After decoding the simulated radiograph data, the centroid location and FWHM/SNR of the fiducial signals were analyzed. The effects of properties related to the CA (rank, pattern, and physical dimensions), detector (dimensions and pixel count), position (CA and phantom), and the incident beam (spectrum and direction) were investigated. These variables were evaluated by quantifying the positional accuracy, resolution, and SNR of the fiducials' signal. The effects of phantom scatter and decoding artifacts were reduced via Fourier filtering to avoid treatment interruption and physical interaction with the coded mask. The method was able to accurately localize the markers to within 1 pixel of a simulated radiograph. A 10×10×2cm tungsten mask was chosen to attenuate >99 % of incident scatter through opaque elements, while minimizing collimation artifacts which arise from vignetting of the coded radiograph. Clear separation of centroids from fiducial signals with 2.5mm separation was maintained, and initial optimization of parameters has produced an aperture which decodes the location of multiple fiducial markers inside a human phantom properly with a high SNR in the final radiograph image. Current results show a proof of concept for a novel real-time imaging method. Coded aperture imaging is a promising technique for extracting the fiducial scatter signal from a broader Compton-scatter background. These results can be used to further optimize the CAI parameter space and guide fabrication and testing of a clinical device.

Observation of Electroweak Production of a Same-Sign W Boson Pair in Association with Two Jets in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector.

This Letter presents the observation and measurement of electroweak production of a same-sign W boson pair in association with two jets using 36.1 fb^{-1} of proton-proton collision data recorded at a center-of-mass energy of sqrt[s]=13 TeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed in the detector fiducial phase-space region, defined by the presence of two same-sign leptons, electron or muon, and at least two jets with a large invariant mass and rapidity difference. A total of 122 candidate events are observed for a background expectation of 69±7 events, corresponding to an observed signal significance of 6.5 standard deviations. The measured fiducial signal cross section is σ^{fid}=2.89_{-0.48}^{+0.51}(stat)_{-0.28}^{+0.29}(syst) fb.

Spectrally red-shifted fluorescent fiducial markers for optimal drift correction in localization microscopy

Precise drift correction is crucial for every single-molecule localization-based microscopy experiment. We evaluate commonly used fiducial markers such as gold nanoparticles, TetraSpeck microspheres, FluoSpheres and nanodiamonds. We introduce spectrally red-shifted fluorescent particles as optimal fiducial markers. Our concept exploits exciting the fluorescent particles at low efficiency far away from their absorption maximum. A fluorescent particle that is covered by a multitude of dyes will nevertheless yield a bright fiducial signal. This represents a simple yet powerful approach to alleviate common problems in drift corrections caused by photobleaching, sudden signal intensity changes or saturation effects of fiducial markers. We adapt our approach for PALM, sptPALM and DNA-PAINT experiments and demonstrate its simple use for varying imaging conditions in different spectral channels.

Mo1301 NOVEL PLATINUM FIDUCIAL SEEDS MADE IN HOUSE AND WIRE PUSH DELIVERY METHOD

Endoscopic Ultrasound (EUS) guided techniques have largely replaced percutaneous and surgical methods for fiducial implantation into deep abdominal lesions. Precise fiducial placement and detection is essential for modern stereotactic body radiation therapy (SBRT), and can be used in computed tomography (CT) and magnetic resonance imaging (MRI) for pre-treatment planning for guided radiation therapy. Gold fiducials have been used for their inertness and visibility on CT, however, platinum fiducials have recently emerged as a viable alternative. New accessories are also emerging to facilitate fiducial delivery including pre-loaded EUS fine needle implantation (FNI) needles. In this case series, we present our experience with implantation of platinum fiducials made in-house with a modified wire push technique and review the quality of pre-treatment imaging of gold coil (GC), solid gold (SG), and solid platinum seed (PS) fiducials. This single center observational case series included subjects undergoing EUS-guided fiducial implantation between January 1, 2011 and April 1, 2016 from a prospectively collected EUS database at The Ottawa Hospital (Canada). Patient demographics (age, sex), procedure details (type of fiducial), and radiologist interpretation of pre-treatment MRI/CT data (signal voids created by fiducials) was assessed using hospital records. During the study period, 17 patients underwent EUS implantation of a total of 48 fiducials with 12 patients (71%) proceeding to pre-treatment MRI/CT imaging. Pre-treatment CT scans were successful in locating the signal void in all 17 patients. Follow-up MRI showed variable results, depending on type of fiducials implanted. In the 14 patients with PS fiducials alone, 37 of 38 [98% (95% CI 92-100%)] fiducial signal voids were confirmed. For the 2 patients with only GC fiducials, a signal void was not delineated from any of the fiducials [0% (95% CI 0-39%)]. One patient received a mix, 2 PS and 2 GC fiducials, and only 2 signal voids [50% (95% CI 15-85%)] were identified. Cost analysis revealed a 20-fold decrease in price of in house made fiducials compared to commercial fiducial purchase. PS fiducials and non-preloaded fiducials were deployed by loading into the FNA needle handle and pushing fiducials through the needle using an ERCP wire. Implantation was performed by pulling the needle back while using fluoroscopy to confirm fiducial deposition. PS fiducials provide superior visibility compared to GC and SG fiducials when fused CT-MRI imaging is used for pre-treatment planning of SBRT. For SBRT in centers using fused CT-MRI imaging, PS fiducials should be the preferred choice, especially if cost-saving can be achieved with PS fiducials produced in-house. Additionally, our ERCP wire push technique is effective and less cumbersome than front-loading techniques.

Smoothing the redshift distributions of random samples for the baryon acoustic oscillations: applications to the SDSS-III BOSS DR12 and QPM mock samples

We investigate the impact of different redshift distributions of random samples on the baryon acoustic oscillations (BAO) measurements of $D_V(z)r_\mathrm{d}^\mathrm{fid}/r_\mathrm{d}$ from the two-point correlation functions (2PCF) of galaxies in the Data Release 12 (DR12) of the Baryon Oscillation Spectroscopic Survey (BOSS). Big surveys, such as BOSS, usually assign redshifts to the random samples by randomly drawing values from the measured redshift distributions of the data, which would necessarily introduce fiducial signals of fluctuations into the random samples, weakening the signals of BAO, if the cosmic variance cannot be ignored. We propose a smooth function of redshift distribution that fits the data well to populate the random galaxy samples. The resulting cosmological parameters match the input parameters of the mock catalogue very well. The significance of BAO signals has been improved by $0.33\sigma$ for a low-redshift (LOWZ) sample and by $0.03\sigma$ for a constant-stellar-mass (CMASS) sample, though the absolute values do not change significantly. Given the precision of the measurements of current cosmological parameters, it would be appreciated for the future improvements on the measurements of galaxy clustering.

Parameter estimation of gravitational waves from nonprecessing black hole-neutron star inspirals with higher harmonics: Comparing Markov-chain Monte Carlo posteriors to an effective Fisher matrix

Most calculations of the gravitational wave signal from merging compact binaries limit attention to the leading-order quadrupole when constructing models for detection or parameter estimation. Some studies have claimed that if additional ``higher harmonics'' are included consistently in the gravitational wave signal and search model, binary parameters can be measured much more precisely. Using the lalinference Markov-chain Monte Carlo parameter estimation code, we construct posterior parameter constraints associated with two distinct nonprecessing black hole--neutron star (BH-NS) binaries, each with and without higher-order harmonics. All simulations place a plausible signal into a three-detector network with Gaussian noise. Our simulations suggest that higher harmonics provide little information, principally allowing us to measure a previously unconstrained angle associated with the source geometry well but otherwise improving knowledge of all other parameters by a few percent for our loud fiducial signal ($\ensuremath{\rho}=20$). Even at this optimistic signal amplitude, different noise realizations have a more significant impact on parameter accuracy than higher harmonics. We compare our results with the ``effective Fisher matrix'' introduced previously as a method to obtain robust analytic predictions for complicated signals with multiple significant harmonics. We find generally good agreement with these predictions, confirm that intrinsic parameter measurement accuracy is nearly independent of detector network geometry, and show that uncertainties in extrinsic and intrinsic parameters can, to a good approximation, be separated. For our fiducial example, the individual masses can be determined to lie between $7.11--11.48{M}_{\ensuremath{\bigodot}}$ and $1.77--1.276{M}_{\ensuremath{\bigodot}}$ at greater than 99% confidence level, accounting for unknown BH spin. Assuming comparable control over waveform systematics, measurements of BH-NS binaries can constrain the BH and perhaps NS mass distributions. Using analytic arguments to guide extrapolation, we anticipate that higher harmonics should provide little new information about nonprecessing BH-NS binaries, for the signal amplitudes expected for the first few detections. Though our study focused on one particular example---higher harmomics---any study of subdominant degrees of freedom in gravitational wave astronomy can adopt the tools presented here ($V/{V}_{\text{prior}}$ and ${D}_{\mathrm{KL}}$) to assess whether new physics is accessible (e.g., modifications of gravity, spin-orbit misalignment) and if so precisely what information those new parameters provide.

Laser time fiducial for precise physical experiment in Shenguang-Ⅲ prototype facility

Using comb laser pulses synchronized with the main pulse output by large laser facility as time fiducial to scale the reaction process between high power laser pulse and target is very important for the realization of precise measurement and simulation in the intense field experiment. We demonstrate a fiber multiharmonic time fiducial laser pulse generation system using optic-electric modulation and optical pulse stacking. A unit optical pulse with a width of 150 ps generated by modulation was stacked in a fiber stacker to form a 1053 nm comb pulse. The pulse was then amplified and frequency-converted to generate green (527 nm) and UV (351 nm) fiducials. The system can stably provide Shenguang-Ⅲ prototype facility with multi-frequency laser time fiducials which is essential for the precise physical experiment. In addition, the system is highly adaptive since it can generate fiducial signals with variable pulse intervals and amplitudes flexibly according to the requirements of different physical experiments.

On-line temporal characterization of an X-ray streak camera

A simple system for an on-line temporal characterization of an X-ray streak camera is described. Multiple UV-transmitting fiber optic channels with known relative time delays facilitate measurements of sweep speed in addition to providing a fiducial signal. Results of measurements on variation of sweep speed across the output screen of an in-house developed X-ray streak camera of an average sweep speed of ∼24.5 ps/ mm and a temporal resolution of ∼7.5 ps are presented.

Neutron emission time measurements for ICF targets

The neutron emission time for laser-driven inertial confinement fusion targets is determined from data recorded with fast neutron and optical detector systems. Two types of neutron detectors are used. Radiation-induced conductivity devices have a 130-ps FWHM response and are sensitive to targets with yields greater than 5×1010 DT neutrons. They measure the average neutron emission time with a precision of ±50 ps and are fast enough to measure the neutron production rate within a target core as a function of time. Plastic scintillators coupled to microchannel-plate photomultiplier tubes have a 1.2-ns FWHM response and measure the average neutron emission time with a precision of ±75 ps for targets with yields greater than 106 neutrons. Streak cameras record the incident laser power. Optical fiducial signals that are injected into each detector are used to cross time between the detector systems. Measurements made on 1-mm-diam spherical targets irradiated with 23 kJ of 0.35-μm light delivered in a temporally square 1.1-ns pulse and yielding 1013 neutrons show a burn duration greater than 300 ps and an average neutron emission time of about 850 ps.

Programmable Synchronization Unit

A Programmable Synchronization Unit (PSU, 135-726) has been designed as an element of the new timing system for the Stanford Linear Collider (SLC) project to provide synchronization signals needed for various apparatus in the SLC Damping Ring, or anywhere it is necessary to monitor longer than the fiducial period (?2.8 ?s). A 119 MHz pulse train derived from the 476 MHz main drive line and superimposed with 360 Hz fiducial signal is the frequency source. Following a programmable delay D of up to 4.4 ?s, the PSU can deliver N pulses of width W (in increments of 8.4 ns) with a pulse period of P (in increments of 58.8 ns, the damping ring half period). The device may be programmed at any time during the interfiducial period.

Focal plane instrumentation: A very high resolution MWPC system for inclined tracks

A focal plane system has been developed for the MIT energy-loss magnetic spectrometer. The arrival time information from adjacent wires of one MWPC ( s = 2 mm), is used to trace particle trajectories with a position resolution of 120 μm (2σ) and an angular resolution of less than 17 mrad (2σ). The tracks are inclined to the MWPC at about 45°. The readout uses 3 delay lines connected to successive sence wires in a cyclical pattern. Coarse wire positions are determined by differences and drift times by sums of signal arrival times at the ends of the delay lines. A Cherenkov counter provides a fiducial signal. Interpolation is independent of drift velocity since the drift is normal to the sense plane. A similar readout with a second chamber provides position information perpendicular to momentum plane. This information is used to correct on-line for focal plane curvatures and other spectrometer aberrations. Final momentum resolution is about 10 −4.

A method of calibrating standard-signal generators and radio-frequency attenuators

The relative magnitudes of radio-frequency signals are measured by passing the signals through a linear heterodyne frequency-convertor and comparing the magnitudes of the resulting intermediate-frequency signals with those of signals from a standard i.f. generator of known performance. Standard-signal generators are calibrated in this way with respect to relatively large fiducial signals. The standard i.f. generator includes an H11-mode piston attenuator excited through a filter designed to reduce errors due to the transmission of energy in other modes. The signals from the frequency convertor and standard generator are compared by means of a linear amplifier with a square-law output meter, which enables accurate measurements to be made with signals below noise level. Signal ratios up to 90 db can be measured directly with the equipment described; the range of indirect measurement is substantially greater. Signal ratios up to 10 db can be measured to 0.02 db, and greater ratios to within 0.2% of their decibel values. Signals 16 db below noise can be measured to 0.5 db. The method has been used at frequencies between 3 and 3000 Mc/s, and can be used for both lower and higher frequencies.