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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

High resolution stationary digital breast tomosynthesis using distributed carbon nanotube x-ray source array

Purpose: The purpose of this study is to investigate the feasibility of increasing the system spatial resolution and scanning speed of Hologic Selenia Dimensions digital breast tomosynthesis (DBT) scanner by replacing the rotating mammography x-ray tube with a specially designed carbon nanotube (CNT) x-ray source array, which generates all the projection images needed for tomosynthesis reconstruction by electronically activating individual x-ray sources without any mechanical motion. The stationary digital breast tomosynthesis (s-DBT) design aims to (i) increase the system spatial resolution by eliminating image blurring due to x-ray tube motion and (ii) reduce the scanning time. Low spatial resolution and long scanning time are the two main technical limitations of current DBT technology. Methods: A CNT x-ray source array was designed and evaluated against a set of targeted system performance parameters. Simulations were performed to determine the maximum anode heat load at the desired focal spot size and to design the electron focusing optics. Field emission current from CNT cathode was measured for an extended period of time to determine the stable life time of CNT cathode for an expected clinical operation scenario. The source array was manufactured, tested, and integrated with a Selenia scanner. An electronic control unit was developed to interface the source array with the detection system and to scan and regulate x-ray beams. The performance of the s-DBT system was evaluated using physical phantoms. Results: The spatially distributed CNT x-ray source array comprised 31 individually addressable x-ray sources covering a 30 angular span with 1 pitch and an isotropic focal spot size of 0.6 mm at full width at half-maximum. Stable operation at 28 kV(peak) anode voltage and 38 mA tube current was demonstrated with extended lifetime and good source-to-source consistency. For the standard imaging protocol of 15 views over 14, 100 mAs dose, and 2 x 2 detector binning, the projection resolution along the scanning direction increased from 4.0 cycles/mm [at 10% modulation-transfer-function (MTF)] in DBT to 5.1 cycles/mm in s-DBT at magnification factor of 1.08. The improvement is more pronounced for faster scanning speeds, wider angular coverage, and smaller detector pixel sizes. The scanning speed depends on the detector, the number of views, and the imaging dose. With 240 ms detector readout time, the s-DBT system scanning time is 6.3 s for a 15-view, 100 mAs scan regardless of the angular coverage. The scanning speed can be reduced to less than 4 s when detectors become faster. Initial phantom studies showed good quality reconstructed images. Conclusions: A prototype s-DBT scanner has been developed and evaluated by retrofitting the Selenia rotating gantry DBT scanner with a spatially distributed CNT x-ray source array. Preliminary results show that it improves system spatial resolution substantially by eliminating image blur due to x-ray focal spot motion. The scanner speed of s-DBT system is independent of angular coverage and can be increased with faster detector without image degration. The accelerated lifetime measurement demonstrated the long term stability of CNT x-ray source array with typical clinical operation lifetime over 3 years.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

X-ray spectral measurements for tungsten-anode from 20 to 49 kVp on a digital breast tomosynthesis system

Purpose: This paper presents new spectral measurements of a tungsten-target digital breast tomosynthesis (DBT) system, including spectra of 43-49 kVp. Methods: Raw x-ray spectra of 20-49 kVp were directly measured from the tube port of a Selenia Dimensions DBT system using a CdTe based spectrometer. Two configurations of collimation were employed: one with two tungsten pinholes of 25{mu}m and 200{mu}m diameters, and the other with a single pinhole of 25{mu}m diameter, for acquiring spectra from the focal spot and from the focal spot as well as its vicinity. Stripping correction was applied to the measured spectra to compensate distortions due to escape events. The measured spectra were compared with the existing mammographic spectra of the TASMIP model in terms of photon fluence per exposure, spectral components, and half-value layer (HVL). HVLs were calculated from the spectra with a numerical filtration of 0.7 mm aluminum and were compared against actual measurements on the DBT system using W/Al (target-filter) combination, without paddle in the beam. Results: The spectra from the double-pinhole configuration, in which the acceptance aperture pointed right at the focal spot, were harder than the single-pinhole spectra which include both primary and off-focus radiation. HVL calculated from the single-pinhole setup agreed with the measured HVL within 0.04 mm aluminum, while the HVL values from the double-pinhole setup were larger than the single-pinhole HVL by at most 0.1 mm aluminum. The spectra from single-pinhole setup agreed well with the TASMIP mammographic spectra, and are more relevant for clinical purpose. Conclusions: The spectra data would be useful for future research on DBT system with tungsten targets.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Small field segments surrounded by large areas only shielded by a multileaf collimator: Comparison of experiments and dose calculation

Purpose: Complex radiotherapy fields delivered using a tertiary multileaf collimator (MLC) often feature small open segments surrounded by large areas of the beam only shielded by the MLC. The aim of this study was to test the ability of two modern dose calculation algorithms to accurately calculate the dose in these fields which would be common, for example, in volumetric modulated arc treatment (VMAT) and study the impact of variations in dosimetric leaf gap (DLG), focal spot size, and MLC transmission in the beam models. Methods: Nine test fields with small fields (0.6-3 cm side length) surrounded by large MLC shielded areas (secondary collimator 12 Multiplication-Sign 12 cm{sup 2}) were created using a 6 MV beam from a Varian Clinac iX linear accelerator with 120 leaf MLC. Measurements of output factors and profiles were performed using a diamond detector (PTW) and compared to two dose calculations algorithms anisotropic analytical algorithm [(AAA) and Acuros XB] implemented on a commercial radiotherapy treatment planning system (Varian Eclipse 10). Results: Both calculation algorithms predicted output factors within 1% for field sizes larger than 1 Multiplication-Sign 1 cm{sup 2}. For smaller fields AAA tended to underestimate the dose. Profiles were predicted well for all fields except for problems of Acuros XB to model the secondary penumbra between MLC shielded fields and the secondary collimator. A focal spot size of 1 mm or less, DLG 1.4 mm and MLC transmission of 1.4% provided a generally good model for our experimental setup. Conclusions: AAA and Acuros XB were found to predict the dose under small MLC defined field segments well. While DLG and focal spot affect mostly the penumbra, the choice of correct MLC transmission will be essential to model treatments such as VMAT accurately.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

SU-E-I-29: Generalized Relative Object Detectability (G-ROD): A Metric for Comparing X-Ray Imaging Detector Systems

Purpose: To determine the relative task-specific performance of two x-ray imaging detectors including the effect of other components of the imaging chain. Methods: The relative object detectability (ROD) was defined as the ratio of the integral of the detective-quantum efficiency (DQE) of a detector weighted by the square of the Fourier Transform (or frequency spectrum) of the object to the same integral for a second detector. The generalized ROD (G-ROD) is calculated by replacing DQE by the generalized DQE (GDQE) which includes geometric unsharpness and scatter to evaluate the total imaging chain. The G-ROD was calculated for the micro-angiographic fluoroscope (MAF) relative to a flat-panel detector (FPD) for low (1.05) and high (1.2) magnifications with two focal-spot sizes, small (0.3 mm) and medium (0.5 mm), and for the same value of scatter fraction. Solid spheres from 50 to 600 microns were simulated as the objects for this evaluation. The G-ROD results were compared with those of the ROD which considers the detectors alone. Results: For 50-micron spheres, the ROD is 7.93 and, for the small [medium] focus, the G-ROD is 6.74 [5.22] at low magnification and 3.03 [1.66] at high magnification, indicating superior performance of the MAF particularly at low magnification. Both ROD and G-ROD decrease monotonically with size and remain around one above 400-microns. The G-ROD decreases more dramatically with low compared to high magnification for both focal spots. Conclusion: In all cases, the MAF performs better than the FPD and the decreasing trend of the G-ROD indicates that the performance of both detectors becomes similar as the object size increases and becomes nearly equal above 400-micron diameter sphere size. Finally, increased magnification and focal-spot size decrease the G-ROD, indicting that they degrade the performance of the MAF more than that of the FPD for a small-object viewing task. Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

SU-E-J-34: Clinical Evaluation of Targeting Accuracy and Tractogrphy Delineation of Radiosurgery

Purpose: Focal radiosurgery is a common treatment modality for trigeminal neuralgia (TN), a neuropathic facial pain condition. Assessment of treatment effectiveness is primarily clinical, given the paucity of investigational tools to assess trigeminal nerve changes. The efficiency of radiosurgery is related to its highly precise targeting. We assessed clinically the targeting accuracy of radiosurgery with Gamma knife. We hypothesized that trigeminal tractography provides more information than 2D-MR imaging, allowing detection of unique, focal changes in the target area after radiosurgery. Methods: Sixteen TN patients (2 females, 4 male, average age 65.3 years) treated with Gamma Knife radiosurgery, 40 Gy/50% isodose line underwent 1.5Tesla MR trigeminal nerve . Target accuracy was assessed from deviation of the coordinates of the target compared with the center of enhancement on post MRI. Radiation dose delivered at the borders of contrast enhancement was evaluated Results: The median deviation of the coordinates between the intended target and the center of contrast enhancement was within 1mm. The radiation doses fitting within the borders of the contrast enhancement the target ranged from 37.5 to 40 Gy. Trigeminal tractography accurately detected the radiosurgical target. Radiosurgery resulted in 47% drop in FA values at the target with no significant change in FA outside the target, suggesting that radiosurgery primarily affects myelin. Tractography was more sensitive, since FA changes were detected regardless of trigeminal nerve enhancement Conclusion: The median deviation found in clinical assessment of gamma knife treatment for TN Is low and compatible with its high rate of efficiency. DTI parameters accurately detect the effects of focal radiosurgery on the trigeminal nerve, serving as an in vivo imaging tool to study TN. This study is a proof of principle for further assessment of DTI parameters to understand the pathophysiology of TN and treatment effects.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

SU-E-T-08: A Convolution Model for Head Scatter Fluence in the Intensity Modulated Field

Purpose: To efficiently calculate the head scatter fluence for an arbitrary intensity-modulated field with any source distribution using the source occlusion model. Method: The source occlusion model with focal and extra focal radiation (Jaffray et al, 1993) can be used to account for LINAC head scatter. In the model, the fluence map of any field shape at any point can be calculated via integration of the source distribution within the visible range, as confined by each segment, using the detector eye's view. A 2D integration would be required for each segment and each fluence plane point, which is time-consuming, as an intensity-modulated field contains typically tens to hundreds of segments. In this work, we prove that the superposition of the segmental integrations is equivalent to a simple convolution regardless of what the source distribution is. In fact, for each point, the detector eye's view of the field shape can be represented as a function with the origin defined at the point's pinhole reflection through the center of the collimator plane. We were thus able to reduce hundreds of source plane integration to one convolution. We calculated the fluence map for various 3D and IMRT beams and various extra-focal source distributions using both the segmental integration approach and the convolution approach and compared the computation time and fluence map results of both approaches. Results: The fluence maps calculated using the convolution approach were the same as those calculated using the segmental approach, except for rounding errors (<0.1%). While it took considerably longer time to calculate all segmental integrations, the fluence map calculation using the convolution approach took only ∼1/3 of the time for typical IMRT fields with ∼100 segments. Conclusions: The convolution approach for head scatter fluence calculation is fast and accurate and can be used to enhance the online process.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

WE-G-BRE-01: A High Power Nanotube X-Ray Microbeam Irradiator for Preclinical Brain Tumor Treatment

Purpose: Microbeam radiation therapy (MRT) is a new type of cancer treatment undergoing studies at various synchrotron facilities. The principle of MRT is using arrays of microscopically small, low-energy X-radiation for the treatment of various radio-resistant, deep-seated tumors. Our motivation is to develop a compact and inexpensive image guided MRT irradiator to use in the research lab setting. After a successful initial demonstration, here we report a second generation carbon nanotube (CNT) cathode based MRT tube, capable of producing multiple microbeam lines with an anticipated dose rate of 11 Gy/min per line. Methods: The system uses multiple line CNT source arrays to generate multiple focal lines on the anode. The increase in dose-rate, compared to our first generation system, is achieved by increasing the operating voltage from 160 kVp to 225kVp, adding multiple simultaneous focal lines on the anode, and a more efficient cooling mechanism using a 6kW oil-cooled anode. Results: This work will present the design and development process, challenges and solutions to meeting operating specifications, and the final design of the tube and collimator, along with optimization and stabilization of its use. A detailed characterization of its capabilities will be included with a comprehensive measurement of its X-ray focal line dimensions, an evaluation of its collimator alignment and microbeam dimensions, and phantom-based quantification of its dosimetric output. Conclusion: The development of a second generation, compact, multiple line MRT device using carbon nanotube (CNT) cathode based X-ray technology and a novel oil cooled anode design is presented here. With this new source, we are capable of delivering a total microbeam radiation dose comparable to the low end of the synchrotron based MRT systems for small animal brain tumor models.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-P-16: A Feasibility Study of Using Eclipse AAA for SRS Treatement

Purpose: To commission Varian Eclipse AAA for SRS treatment and compare the accuracy with Brainlab iPlan system for clinical cases measured with radiochromic film. Methods: A 6MV AAA clinical model for a Varian TrueBeam STx is used as baseline. The focal spot and field size of the baseline model(BASE) are (1.75,0.75) and 40×40cm{sup 2} respectively. Maximum field sizes, output factors(S{sub t}), FWHM focal spot and secondary source sizes are systematically adjusted to obtain an optimized model(OPT) by comparing the calculated PDD’s, profiles, and output factors with measurements taken with a stereotactic diode(SD) and, cc01 and cc04 ion chambers in Blue Phantom. In-phantom dose distributions of clinical SRS fields are calculated using the OPT and the clinical Brainlab iPlan pencil-beam. Within the 90% isodose-line(ROI), the average dose difference between the calculations and radiochromic film measurements are assessed. Results: The maximum field, focal spot and secondary source sizes for the OPT are 15×15cm{sup 2}, (0,0), and 32.3mm respectively. The OPT St input at 1.0 and 2.0cm fields are increased by 4.5% and 1.5% from BASE. The calculated output of the BASE and OPT underestimate by 16.1%–3.2% respectively at 0.5×0.5cm{sup 2} field and 3.1%−0.02% respectively at 1.0×1.0cm{sup 2} field. The depth doses at 10cm are within 3.5% and 0.4% of measurements for 0.5×0.5 and 1.0×1.0cm{sup 2}. The ROI dose of OPT and iPlan are within 1.6% and 0.6% of film measurements for 3.0cm clinical fields. For 1.0cm fields, the ROI dose of OPT underestimate 0.0–2.0% and iPlan overestimates 1.7–2.9% relative to measurements. Conclusion: The small field dose calculation of Eclipse AAA algorithm can be significantly improved by carefully adjusting the input parameters. The larger deviation of the OPT for 0.5×0.5cm{sup 2} field from measurements can be attributed to the lowest 1.0cm field size input limit of AAA. The OPT compares reasonably well with the iPlan pencil-beam and measurements.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Intercostal high intensity focused ultrasound for liver ablation: The influence of beam shaping on sonication efficacy and near-field risks

Purpose: One of the major issues in high intensity focused ultrasound ablation of abdominal lesions is obstruction of the ultrasound beam by the thoracic cage. Beam shaping strategies have been shown by several authors to increase focal point intensity while limiting rib exposure. However, as rib obstruction leaves only part of the aperture available for energy transmission, conserving total emitted acoustic power, the intensity in the near-field tissues inherently increases after beam shaping. Despite of effective rib sparing, those tissues are therefore subjected to increased risk of thermal damage. In this study, for a number of clinically representative intercostal sonication geometries, modeling clinically available hardware, the effect of beam shaping on both the exposure of the ribs and near-field to acoustic energy was evaluated and the implications for the volumetric ablation rate were addressed. Methods: A relationship between rib temperature rise and acoustic energy density was established by means of in vivo MR thermometry and simulations of the incident acoustic energy for the corresponding anatomies. This relationship was used for interpretation of rib exposure in subsequent numerical simulations in which rib spacing, focal point placement, and the focal point trajectory were varied. The time required to heat a targeted region to 65 °C was determined without and with the application of beam shaping. The required sonication time was used to calculate the acoustic energy density at the fat–muscle interface and at the surface of the ribs. At the fat–muscle interface, exposure was compared to available literature data and rib exposure was interpreted based on the earlier obtained relation between measured temperature rise and simulated acoustic energy density. To estimate the volumetric ablation rate, the cool-down time between periods of energy exposure was estimated using a time-averaged power limit of 100 kJ/h. Results: At the level of the ribs, the temperature rise–energy density proportionality constant was estimated to be 6.0–7.6 °C/(J/mm{sup 2}). Beam shaping by the geometric shadow method typically reduces the acoustic intensity a factor of 2, considering the 1 cm{sup 2} with the highest exposure. For a 4 mm diameter circular sonication trajectory, the near-field energy limit of 2.5 J/mm{sup 2} was exceeded for all considered geometries. The estimated rib temperature was in all but one (sonication 50 mm behind the ribs, with 15 mm rib spacing and a 4 mm diameter circular sonication trajectory) of the considered scenarios within acceptable limits. For those sonication scenarios where a single sonication is considered safe both in terms of near-field as well as rib heating, volumetric ablation rates in the order of 1 ml/h are estimated. Conclusions: Intercostal sonication is associated with an increased risk of near-field overheating. This risk is strongly dependent on the considered rib spacing, the placement of the focus behind the ribs, and the selected sonication trajectory. For the hardware under simulation, obstruction by the thoracic cage renders ablations of clinically relevant volumes within a practical time-frame unfeasible in a large part of the liver. Improvements maybe expected from transducer designs with a larger active surface and/or nonlinear sonication strategies.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-J-160: Clinical Evaluation of Targeting Accuracy in Radiosurgery Using Tractography

Purpose: Focal radiosurgery is a common treatment modality for trigeminal neuralgia (TN), a neuropathic facial pain condition. Assessment of treatment effectiveness is primarily clinical, given the paucity of investigational tools to assess trigeminal nerve changes. The efficiency of radiosurgery is related to its highly precise targeting. We assessed clinically the targeting accuracy of radiosurgery with Gamma knife. We hypothesized that trigeminal tractography provides more information than 2D-MR imaging, allowing detection of unique, focal changes in the target area after radiosurgery. Methods: Sixteen TN patients (2 females, 4 males, average age 65.3 years) treated with Gamma Knife radiosurgery, 40 Gy/50% isodose line underwent 1.5Tesla MR trigeminal nerve. Target accuracy was assessed from deviation of the coordinates of the target compared with the center of enhancement on post MRI. Radiation dose delivered at the borders of contrast enhancement was evaluated. Results: The median deviation of the coordinates between the intended target and the center of contrast enhancement was within 1mm. The radiation doses fitting within the borders of the contrast enhancement the target ranged from 37.5 to 40 Gy. Trigeminal tractography accurately detected the radiosurgical target. Radiosurgery resulted in 47% drop in FA values at the target with no significant change in FA outside the target, suggesting that radiosurgery primarily affects myelin. Tractography was more sensitive, since FA changes were detected regardless of trigeminal nerve enhancement. Conclusion: The median deviation found in clinical assessment of gamma knife treatment for TN Is low and compatible with its high rate of efficiency. DTI parameters accurately detect the effects of focal radiosurgery on the trigeminal nerve, serving as an in vivo imaging tool to study TN. This study is a proof of principle for further assessment of DTI parameters to understand the pathophysiology of TN and treatment effects.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Photon noise correlations in millimeter-wave telescopes

Many modern millimeter and submillimeter (“mm-wave”) telescopes for astronomy are deploying more detectors by increasing the detector pixel density and, with the rise of lithographed detector architectures and high-throughput readout techniques, it is becoming increasingly practical to overfill the focal plane. However, when the pixel pitch p pix is small compared to the product of the wavelength λ and the focal ratio F , or p pix ≲1.2 F λ , the Bose term of the photon noise correlates between neighboring detector pixels due to the Hanbury Brown and Twiss (HBT) effect. When this HBT effect is non-negligible, the array-averaged sensitivity scales with the detector count N det less favorably than the uncorrelated limit of N det −1/2 . In this paper, we present a general prescription to calculate this HBT correlation based on a quantum optics formalism and extend it to polarization-sensitive detectors. We then estimate the impact of HBT correlations on the sensitivity of a model mm-wave telescope and discuss the implications for a focal plane design.

Hill, Charles A. (ORCID:0000000226416878)↗
DOE OSTI2015

Diffraction properties of multilayer Laue lenses with an aperture of 102 µm and WSi 2 /Al bilayers

We report on the characterization of a multilayer Laue lens (MLL) with large acceptance, made of a novel WSi 2 /Al bilayer system. Fabrication of multilayers with large deposition thickness is required to obtain MLL structures with sufficient apertures capable of accepting the full lateral coherence length of x-rays at typical nanofocusing beamlines. To date, the total deposition thickness has been limited by stress-buildup in the multilayer. We were able to grow WSi2/Al with low grown-in stress, and asses the degree of stress reduction. X-ray diffraction experiments were conducted at beamline 1-BM at the Advanced Photon Source. We used monochromatic x-rays with a photon energy of 12 keV and a bandwidth of $ΔE/\atop {E}$ = 5.4 • 10 -4 . The MLL was grown with parallel layer interfaces, and was designed to have a large focal length of 9.6 mm. The mounted lens was 2.7 mm in width. We found and quantified kinks and bending of sections of the MLL. Sections with bending were found to partly have a systematic progression in the interface angles. We observed kinking in some, but not all, areas. The measurements are compared with dynamic diffraction calculations made with Coupled Wave Theory. Data are plotted showing the diffraction efficiency as a function of the external tilting angle of the entire mounted lens. This way of plotting the data was found to provide an overview into the diffraction properties of the whole lens, and enabled the following layer tilt analyses.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Snapshot multifocal light field microscopy

Light field microscopy (LFM) is an emerging technology for high-speed wide-field 3D imaging by capturing 4D light field of 3D volumes. However, its 3D imaging capability comes at a cost of lateral resolution. In addition, the lateral resolution is not uniform across depth in the light field dconvolution reconstructions. To address these problems, here, we propose a snapshot multifocal light field microscopy (MFLFM) imaging method. The underlying concept of the MFLFM is to collect multiple focal shifted light fields simultaneously. We show that by focal stacking those focal shifted light fields, the depth-of-field (DOF) of the LFM can be further improved but without sacrificing the lateral resolution. Also, if all differently focused light fields are utilized together in the deconvolution, the MFLFM could achieve a high and uniform lateral resolution within a larger DOF. We present a house-built MFLFM system by placing a diffractive optical element at the Fourier plane of a conventional LFM. The optical performance of the MFLFM are analyzed and given. Both simulations and proof-of-principle experimental results are provided to demonstrate the effectiveness and benefits of the MFLFM. We believe that the proposed snapshot MFLFM has potential to enable high-speed and high resolution 3D imaging applications.

He, Kuan↗
DOE OSTI2013

The Interaction of Vinculin with Actin

Vinculin can interact with F-actin both in recruitment of actin filaments to the growing focal adhesions and also in capping of actin filaments to regulate actin dynamics. Using molecular dynamics, both interactions are simulated using different vinculin conformations. Vinculin is simulated either with only its vinculin tail domain (Vt), with all residues in its closed conformation, with all residues in an open I conformation, and with all residues in an open II conformation. The open I conformation results from movement of domain 1 away from Vt; the open II conformation results from complete dissociation of Vt from the vinculin head domains. Simulation of vinculin binding along the actin filament showed that Vt alone can bind along the actin filaments, that vinculin in its closed conformation cannot bind along the actin filaments, and that vinculin in its open I conformation can bind along the actin filaments. The simulations confirm that movement of domain 1 away from Vt in formation of vinculin 1 is sufficient for allowing Vt to bind along the actin filament. Simulation of Vt capping actin filaments probe six possible bound structures and suggest that vinculin would cap actin filaments by interacting with both S1 and S3 of the barbed-end, using the surface of Vt normally occluded by D4 and nearby vinculin head domain residues. Simulation of D4 separation from Vt after D1 separation formed the open II conformation. Binding of open II vinculin to the barbed-end suggests this conformation allows for vinculin capping. Three binding sites on F-actin are suggested as regions that could link to vinculin. Vinculin is suggested to function as a variable switch at the focal adhesions. The conformation of vinculin and the precise F-actin binding conformation is dependent on the level of mechanical load on the focal adhesion.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Evaluation of an autonomous acoustic surveying technique for grassland bird communities in Nebraska

Monitoring trends in wildlife communities is integral to making informed land management decisions and applying conservation strategies. Birds inhabit most niches in every environment and because of this they are widely accepted as an indicator species for environmental health. Traditionally, point counts are the common method to survey bird populations, however, passive acoustic monitoring approaches using autonomous recording units have been shown to be cost-effective alternatives to point count surveys. Advancements in automatic acoustic classification technologies, such as BirdNET, can aid in these efforts by quickly processing large volumes of acoustic recordings to identify bird species. While the utility of BirdNET has been demonstrated in several applications, there is little understanding of its effectiveness in surveying declining grassland birds. We conducted a study to evaluate the performance of BirdNET to survey grassland bird communities in Nebraska by comparing this automated approach to point count surveys. We deployed ten autonomous recording units from March through September 2022: five recorders in row-crop fields and five recorders in perennial grassland fields. During this study period, we visited each site three times to conduct point count surveys. We compared focal grassland bird species richness between point count surveys and the autonomous recording units at two different temporal scales and at six different confidence thresholds. Total species richness (focal and non-focal) for both methods was also compared at five different confidence thresholds using species accumulation curves. The results from this study demonstrate the usefulness of BirdNET at estimating long-term grassland bird species richness at default confidence scores, however, obtaining accurate abundance estimates for uncommon bird species may require validation with traditional methods.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Wasatch Fault Structure from Machine Learning Arrival Times and High-Precision Earthquake Locations

Abstract On 18 March 2020, a magnitude 5.7 earthquake hit the Salt Lake valley in the state of Utah, United States. Using a dense geophone deployment and machine learning (ML), an additional several thousand events were detected and located. Currently, both the mainshock and the majority of the aftershocks are suspected to have occurred on or near a deeper portion of the Salt Lake segment of the Wasatch fault—part of a large range-bounding fault system thought to be capable of generating an Mw 7.2 earthquake. However, a small subset of aftershocks may have occurred on a portion of the more steeply, eastward dipping, and poorly understood West Valley fault. Unfortunately, the catalog locations and lack of focal mechanisms for this subset of aftershocks provide only a crude constraint on the true fault structure. To better illuminate fault structure, we relocate the ML-generated catalog with a range of magnitudes from −2 to 4.6, using: (1) NonLinLoc, a nonlinear location algorithm, (2) source-specific station terms, and (3) waveform coherence. We further compute first-motion focal mechanisms for 68 events. Results of the relocation suggest a simpler, minimally listric Wasatch fault geometry, contrary to what has been previously proposed. We also find that analysis of the focal mechanisms and waveform similarity indicates minimal event similarity throughout the Magna sequence, suggesting a highly complex and heterogeneous rupture zone, as opposed to rupture on a single plane. These findings suggest an increased seismic hazard due to the overall shallowness of the earthquake sequence and highly varied rupture mechanisms.

Geochemistry & Geophysics↗
DOE OSTI2025

A Deep Learning-Aided Workflow for Decoding the Stress Regime of Southern Nevada

The Rock Valley fault zone in southern Nevada has a notable history of seismic activity and is the site of a future direct comparison experiment of explosion and earthquake sources. This study aims to gain insight into regional tectonic processes by leveraging recent advances in seismic monitoring capabilities to elucidate the local stress regime. A crucial step in this investigation is the accurate determination of P-wave first-motion polarities, which play a vital role in resolving earthquake focal mechanisms of small earthquakes. Here, we deploy a deep learning-based method for automatic determination of first-motion polarities to vastly expand the polarity dataset beyond what has been reviewed by human analysts. By the integrating P-wave polarities with new measurements of S/P amplitude ratios, we obtain robust focal mechanism estimates for 1306 earthquakes with a local magnitude of 1 and above occurring between 2010 and 2023 in southern Nevada. We then use the focal mechanism catalog to examine the regional stress orientation, confirming an overall trans-tensional stress regime with smaller scale complexities illuminated by individual earthquake sequences. These findings demonstrate how detailed analyses of small earthquakes can provide fundamental information for understanding earthquake processes in the region and inform future experiments at the Nevada National Security Site.

58 GEOSCIENCES↗
DOE OSTI2015

Impacts of electromagnetic fields associated with marine and hydrokinetic surrogate technologies on fish movements and behaviors.

Marine and hydrokinetic energy (MHK) and offshore wind devices are being developed and deployed in U.S. and international waters. Electric current flowing through subsea transmission cables associated with these devices will generate electromagnetic fields (EMF), which may interact with, and potentially impact, marine fishes. Some marine fishes can detect electric and/or magnetic fields and use them to navigate, orientate, and sense prey, mates and predators. Over the past five years there have been multiple comprehensive reviews and studies evaluating the potential vulnerability of marine fishes to EMF produced by MHK devices. Most documented effects involve sub-lethal behavioral responses of individual fish when in close proximity to EMF (e.g., fish being repelled by or attracted to fields). These reviews reach conclusions that the current state of research on this topic is still in its infancy and evaluations of potential impacts are associated with great uncertainty. A variety of MHK technologies are likely to be considered for deployment offshore of the Hawaiian Islands, and there is a need to be able to better predict and assess potential associated environmental impacts. The goal of this study was to provide a complementary piece to these previous reviews (e.g., Normandeau et al. 2011) by focusing on marine fish species in the Hawaii region. We compiled the relevant available information, then prioritized fish species as candidates for various paths of future research. To address this, we first developed a list of Hawaii Region Focal Species, which included fishes that are more likely to be sensitive to EMF. We then compiled species-specific information available in the literature on their sensitivity to EMF, as well as life history, movement and habitat use information that could inform an analysis of their likelihood of encountering EMF from subsea cables associated with MHK devices. Studies have only documented EMF sensitivity in 11 of the marine fish species in this region. There was also relatively little detailed information on fish movement and habitat use patterns for most of the focal species. Our last objective was to develop recommendations for research needs to close the important knowledge gaps. We describe species-independent baseline research that primarily consists of in situ quantification of EMF generated by MHK devices and undersea cables that can occur as pilot and commercial scale MHK devices are deployed in Hawaii. Then we propose a simple approach for prioritizing Hawaii Region Focal Species (ranked relative to each other) as candidates in multiple related research paths. The prioritization approach incorporates EMF sensitivity information with the likelihood of interacting with EMF generated undersea transmission cables associated with MHK devices. Finally, we discuss the types of research needed to help fill gaps in the scientific knowledge base for this region. These involve studies to better define species-specific EMF sensitivity thresholds under various environmental conditions, studies of life history, movement and habitat use patterns to improve our understanding of the likelihood and frequency fishes may be in the vicinity of EMF generated by subsea transmission cables, and studies of the potential for related population, community or ecosystem impacts. Many of these studies can and should occur opportunistically as pilot and commercial scale MHK devices are deployed in Hawaii.

59 BASIC BIOLOGICAL SCIENCES↗