Results for “Reasoning” — Page 51

DOE OSTI2015

WE-AB-213-03: Challenges and Opportunities

AAPM projects and collaborations in Africa Adam Shulman (AA-SC Chair) The African Affairs Subcommittee (AA-SC) of the AAPM will present a multi-institutional approach to medical physics support in Africa. Current work to increase the quality of care and level of safety for the medical physics practice in Senegal, Ghana, and Zimbabwe will be presented, along with preliminary projects in Nigeria and Botswana. Because the task of addressing the needs of medical physics in countries across Africa is larger than one entity can accomplish on its own, the AA-SC has taken the approach of joining forces with multiple organizations such as Radiating Hope and TreatSafely (NGO’s), the IAEA, companies like BrainLab, Varian and Elekta, medical volunteers and academic institutions such as NYU and Washington University. Elements of current projects include: 1) Distance training and evaluation of the quality of contouring and treatment planning, teaching treatment planning and other subjects, and troubleshooting using modern telecommunications technology in Senegal, Ghana, and Zimbabwe; 2) Assistance in the transition from 2D to 3D in Senegal and Zimbabwe; 3) Assistance in the transition from 3D to IMRT using in-house compensators in Senegal; 4) Modernizing the cancer center in Senegal and increasing safety and; 5) Training on on 3D techniques in Ghana; 6) Assisting a teaching and training radiation oncology center to be built in Zimbabwe; 7) Working with the ISEP Program in Sub-Saharan Africa; 8) Creating instructional videos on linac commissioning; 9) Working on a possible collaboration to train physicists in Nigeria. Building on past achievements, the subcommittee seeks to make a larger impact on the continent, as the number and size of projects increases and more human resources become available. The State of Medical Physics Collaborations and Projects in Latin America Sandra Guzman (Peru) The lack of Medical Physicists (MP) in many Latin American (LA) countries leads to recruitment of professionals with incomplete education. In most LA countries only one MP responsible for each Center is currently mandated. Currently there is a large disparity among MP training programs and there is significant debate about the standards of MP graduate education in many LA countries. There are no commonly recognized academic programs, not enough clinical training sites and clinical training is not typically considered as part of the MP work. Economic pressures and high workloads also impede the creation of more training centers. The increasing need of qualified MPs require establishing a coordinated system of national Education & Training Centers (ETC), to meet the international standards of education and training in Medical Physics. This shortfall calls for support of organizations such as the IOMP, AAPM, ALFIM, IAEA, etc. Examples from various LA countries, as well as some proposed solutions, will be presented. In particular, we will discuss the resources that the AAPM and its members can offer to support regional programs. The ‘Medical Imaging’ physicist in the emerging world: Challenges and opportunities - Caridad Borrás (WGNIMP Chair) While the role of radiation therapy physicists in the emerging world is reasonably well established, the role of medical imaging physicists is not. The only perceived needs in radiology departments are equipment quality control and radiation protection, tasks that can be done by a technologist or a service engineer. To change the situation, the International Basic Safety Standard, which is adopted/adapted world-wide as national radiation protection regulations, states: “For diagnostic radiological procedures and image guided interventional procedures, the requirements of these Standards for medical imaging, calibration, dosimetry and quality assurance, including the acceptance and commissioning of medical radiological equipment, are fulfilled by or under the oversight of, or with the documented advice of a medical physicist, whose degree of involvement is determined by the complexity of the radiological procedures and the associated radiation risks”. Details on how these requirements can be carried out in resource-limited settings will be described. IAEA support to medical physics in Africa and Latin America: achievements and challenges Ahmed Meghzifene (IAEA) Shortage of clinically qualified medical physicists in radiotherapy and imaging, insufficient and inadequate education and training programs, as well as a lack of professional recognition were identified as the main issues to be addressed by the IAEA. The IAEA developed a series of integrated projects aiming specifically at promoting the essential role of medical physicists in health care, developing harmonized guidelines on dosimetry and quality assurance, and supporting education and clinical training programs. The unique feature of the IAEA approach is support it provides for implementation of guidelines and education programs in Member States through its technical cooperation project. The presentation will summarize IAEA support to Latin America and Africa in the field of medical physics and will highlight how the new International Basic Safety Standards are expected to impact the medical physics practice in low and middle income countries. Learning Objectives: Learn about the shortage of qualified Medical Physicists in Africa and Latin America. Understand the reasons of this shortage. Learn about the ways to improve the situation and AAPM role in this process.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

WE-AB-213-04: IAEA Support to Medical Physics in Africa and Latin America: Achievements and Challenges

AAPM projects and collaborations in Africa Adam Shulman (AA-SC Chair) The African Affairs Subcommittee (AA-SC) of the AAPM will present a multi-institutional approach to medical physics support in Africa. Current work to increase the quality of care and level of safety for the medical physics practice in Senegal, Ghana, and Zimbabwe will be presented, along with preliminary projects in Nigeria and Botswana. Because the task of addressing the needs of medical physics in countries across Africa is larger than one entity can accomplish on its own, the AA-SC has taken the approach of joining forces with multiple organizations such as Radiating Hope and TreatSafely (NGO’s), the IAEA, companies like BrainLab, Varian and Elekta, medical volunteers and academic institutions such as NYU and Washington University. Elements of current projects include: 1) Distance training and evaluation of the quality of contouring and treatment planning, teaching treatment planning and other subjects, and troubleshooting using modern telecommunications technology in Senegal, Ghana, and Zimbabwe; 2) Assistance in the transition from 2D to 3D in Senegal and Zimbabwe; 3) Assistance in the transition from 3D to IMRT using in-house compensators in Senegal; 4) Modernizing the cancer center in Senegal and increasing safety and; 5) Training on on 3D techniques in Ghana; 6) Assisting a teaching and training radiation oncology center to be built in Zimbabwe; 7) Working with the ISEP Program in Sub-Saharan Africa; 8) Creating instructional videos on linac commissioning; 9) Working on a possible collaboration to train physicists in Nigeria. Building on past achievements, the subcommittee seeks to make a larger impact on the continent, as the number and size of projects increases and more human resources become available. The State of Medical Physics Collaborations and Projects in Latin America Sandra Guzman (Peru) The lack of Medical Physicists (MP) in many Latin American (LA) countries leads to recruitment of professionals with incomplete education. In most LA countries only one MP responsible for each Center is currently mandated. Currently there is a large disparity among MP training programs and there is significant debate about the standards of MP graduate education in many LA countries. There are no commonly recognized academic programs, not enough clinical training sites and clinical training is not typically considered as part of the MP work. Economic pressures and high workloads also impede the creation of more training centers. The increasing need of qualified MPs require establishing a coordinated system of national Education & Training Centers (ETC), to meet the international standards of education and training in Medical Physics. This shortfall calls for support of organizations such as the IOMP, AAPM, ALFIM, IAEA, etc. Examples from various LA countries, as well as some proposed solutions, will be presented. In particular, we will discuss the resources that the AAPM and its members can offer to support regional programs. The ‘Medical Imaging’ physicist in the emerging world: Challenges and opportunities - Caridad Borrás (WGNIMP Chair) While the role of radiation therapy physicists in the emerging world is reasonably well established, the role of medical imaging physicists is not. The only perceived needs in radiology departments are equipment quality control and radiation protection, tasks that can be done by a technologist or a service engineer. To change the situation, the International Basic Safety Standard, which is adopted/adapted world-wide as national radiation protection regulations, states: “For diagnostic radiological procedures and image guided interventional procedures, the requirements of these Standards for medical imaging, calibration, dosimetry and quality assurance, including the acceptance and commissioning of medical radiological equipment, are fulfilled by or under the oversight of, or with the documented advice of a medical physicist, whose degree of involvement is determined by the complexity of the radiological procedures and the associated radiation risks”. Details on how these requirements can be carried out in resource-limited settings will be described. IAEA support to medical physics in Africa and Latin America: achievements and challenges Ahmed Meghzifene (IAEA) Shortage of clinically qualified medical physicists in radiotherapy and imaging, insufficient and inadequate education and training programs, as well as a lack of professional recognition were identified as the main issues to be addressed by the IAEA. The IAEA developed a series of integrated projects aiming specifically at promoting the essential role of medical physicists in health care, developing harmonized guidelines on dosimetry and quality assurance, and supporting education and clinical training programs. The unique feature of the IAEA approach is support it provides for implementation of guidelines and education programs in Member States through its technical cooperation project. The presentation will summarize IAEA support to Latin America and Africa in the field of medical physics and will highlight how the new International Basic Safety Standards are expected to impact the medical physics practice in low and middle income countries. Learning Objectives: Learn about the shortage of qualified Medical Physicists in Africa and Latin America. Understand the reasons of this shortage. Learn about the ways to improve the situation and AAPM role in this process.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

WE-AB-213-05: Closing Remarks

AAPM projects and collaborations in Africa Adam Shulman (AA-SC Chair) The African Affairs Subcommittee (AA-SC) of the AAPM will present a multi-institutional approach to medical physics support in Africa. Current work to increase the quality of care and level of safety for the medical physics practice in Senegal, Ghana, and Zimbabwe will be presented, along with preliminary projects in Nigeria and Botswana. Because the task of addressing the needs of medical physics in countries across Africa is larger than one entity can accomplish on its own, the AA-SC has taken the approach of joining forces with multiple organizations such as Radiating Hope and TreatSafely (NGO’s), the IAEA, companies like BrainLab, Varian and Elekta, medical volunteers and academic institutions such as NYU and Washington University. Elements of current projects include: 1) Distance training and evaluation of the quality of contouring and treatment planning, teaching treatment planning and other subjects, and troubleshooting using modern telecommunications technology in Senegal, Ghana, and Zimbabwe; 2) Assistance in the transition from 2D to 3D in Senegal and Zimbabwe; 3) Assistance in the transition from 3D to IMRT using in-house compensators in Senegal; 4) Modernizing the cancer center in Senegal and increasing safety and; 5) Training on on 3D techniques in Ghana; 6) Assisting a teaching and training radiation oncology center to be built in Zimbabwe; 7) Working with the ISEP Program in Sub-Saharan Africa; 8) Creating instructional videos on linac commissioning; 9) Working on a possible collaboration to train physicists in Nigeria. Building on past achievements, the subcommittee seeks to make a larger impact on the continent, as the number and size of projects increases and more human resources become available. The State of Medical Physics Collaborations and Projects in Latin America Sandra Guzman (Peru) The lack of Medical Physicists (MP) in many Latin American (LA) countries leads to recruitment of professionals with incomplete education. In most LA countries only one MP responsible for each Center is currently mandated. Currently there is a large disparity among MP training programs and there is significant debate about the standards of MP graduate education in many LA countries. There are no commonly recognized academic programs, not enough clinical training sites and clinical training is not typically considered as part of the MP work. Economic pressures and high workloads also impede the creation of more training centers. The increasing need of qualified MPs require establishing a coordinated system of national Education & Training Centers (ETC), to meet the international standards of education and training in Medical Physics. This shortfall calls for support of organizations such as the IOMP, AAPM, ALFIM, IAEA, etc. Examples from various LA countries, as well as some proposed solutions, will be presented. In particular, we will discuss the resources that the AAPM and its members can offer to support regional programs. The ‘Medical Imaging’ physicist in the emerging world: Challenges and opportunities - Caridad Borrás (WGNIMP Chair) While the role of radiation therapy physicists in the emerging world is reasonably well established, the role of medical imaging physicists is not. The only perceived needs in radiology departments are equipment quality control and radiation protection, tasks that can be done by a technologist or a service engineer. To change the situation, the International Basic Safety Standard, which is adopted/adapted world-wide as national radiation protection regulations, states: “For diagnostic radiological procedures and image guided interventional procedures, the requirements of these Standards for medical imaging, calibration, dosimetry and quality assurance, including the acceptance and commissioning of medical radiological equipment, are fulfilled by or under the oversight of, or with the documented advice of a medical physicist, whose degree of involvement is determined by the complexity of the radiological procedures and the associated radiation risks”. Details on how these requirements can be carried out in resource-limited settings will be described. IAEA support to medical physics in Africa and Latin America: achievements and challenges Ahmed Meghzifene (IAEA) Shortage of clinically qualified medical physicists in radiotherapy and imaging, insufficient and inadequate education and training programs, as well as a lack of professional recognition were identified as the main issues to be addressed by the IAEA. The IAEA developed a series of integrated projects aiming specifically at promoting the essential role of medical physicists in health care, developing harmonized guidelines on dosimetry and quality assurance, and supporting education and clinical training programs. The unique feature of the IAEA approach is support it provides for implementation of guidelines and education programs in Member States through its technical cooperation project. The presentation will summarize IAEA support to Latin America and Africa in the field of medical physics and will highlight how the new International Basic Safety Standards are expected to impact the medical physics practice in low and middle income countries. Learning Objectives: Learn about the shortage of qualified Medical Physicists in Africa and Latin America. Understand the reasons of this shortage. Learn about the ways to improve the situation and AAPM role in this process.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

Bowtie filters for dedicated breast CT: Analysis of bowtie filter material selection

Purpose: For a given bowtie filter design, both the selection of material and the physical design control the energy fluence, and consequently the dose distribution, in the object. Using three previously described bowtie filter designs, the goal of this work is to demonstrate the effect that different materials have on the bowtie filter performance measures. Methods: Three bowtie filter designs that compensate for one or more aspects of the beam-modifying effects due to the differences in path length in a projection have been designed. The nature of the designs allows for their realization using a variety of materials. The designs were based on a phantom, 14 cm in diameter, composed of 40% fibroglandular and 60% adipose tissue. Bowtie design #1 is based on single material spectral matching and produces nearly uniform spectral shape for radiation incident upon the detector. Bowtie design #2 uses the idea of basis-material decomposition to produce the same spectral shape and intensity at the detector, using two different materials. With bowtie design #3, it is possible to eliminate the beam hardening effect in the reconstructed image by adjusting the bowtie filter thickness so that the effective attenuation coefficient for every ray is the same. Seven different materials were chosen to represent a range of chemical compositions and densities. After calculation of construction parameters for each bowtie filter design, a bowtie filter was created using each of these materials (assuming reasonable construction parameters were obtained), resulting in a total of 26 bowtie filters modeled analytically and in the PENELOPE Monte Carlo simulation environment. Using the analytical model of each bowtie filter, design profiles were obtained and energy fluence as a function of fan-angle was calculated. Projection images with and without each bowtie filter design were also generated using PENELOPE and reconstructed using FBP. Parameters such as dose distribution, noise uniformity, and scatter were investigated. Results: Analytical calculations with and without each bowtie filter show that some materials for a given design produce bowtie filters that are too large for implementation in breast CT scanners or too small to accurately manufacture. Results also demonstrate the ability to manipulate the energy fluence distribution (dynamic range) by using different materials, or different combinations of materials, for a given bowtie filter design. This feature is especially advantageous when using photon counting detector technology. Monte Carlo simulation results from PENELOPE show that all studied material choices for bowtie design #2 achieve nearly uniform dose distribution, noise uniformity index less than 5%, and nearly uniform scatter-to-primary ratio. These same features can also be obtained using certain materials with bowtie designs #1 and #3. Conclusions: With the three bowtie filter designs used in this work, the selection of material is an important design consideration. An appropriate material choice can improve image quality, dose uniformity, and dynamic range.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

Detector dose response in megavoltage small photon beams. I. Theoretical concepts

Purpose: To explain the reasons for significant quality correction factors in megavoltage small photon fields and clarify the underlying concepts relevant to dosimetry under such conditions. Methods: The validity of cavity theory and the requirement of charged particle equilibrium (CPE) are addressed from a theoretical point of view in the context of nonstandard beams. Perturbation effects are described into four main subeffects, explaining their nature and pointing out their relative importance in small photon fields. Results: It is demonstrated that the failure to meet classical cavity theory requirements, such as CPE, is not the reason for significant quality correction factors. On the contrary, it is shown that the lack of CPE alone cannot explain these corrections and that what matters most, apart from volume averaging effects, is the relationship between the lack of CPE in the small field itself and the density of the detector cavity. The density perturbation effect is explained based on Fano’s theorem, describing the compensating effect of two main contributions to cavity absorbed dose. Using the same approach, perturbation effects arising from the difference in atomic properties of the cavity medium and the presence of extracameral components are explained. Volume averaging effects are also discussed in detail. Conclusions: Quality correction factors of small megavoltage photon fields are mainly due to differences in electron density between water and the detector medium and to volume averaging over the detector cavity. Other effects, such as the presence of extracameral components and differences in atomic properties of the detection medium with respect to water, can also play an accentuated role in small photon fields compared to standard beams.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2016

SU-C-BRB-02: Automatic Planning as a Potential Strategy for Dose Escalation for Pancreas SBRT?

Purpose: Stereotactic body radiation therapy (SBRT) has been suggested to provide high rates of local control for locally advanced pancreatic cancer. However, the close proximity of highly radiosensitive normal tissues usually causes the labor-intensive planning process, and may impede further escalation of the prescription dose. The present study evaluates the potential of an automatic planning system as a dose escalation strategy. Methods: Ten pancreatic cancer patients treated with SBRT were studied retrospectively. SBRT was delivered over 5 consecutive fractions with 6 ∼ 8Gy/fraction. Two plans were generated by Pinnacle Auto-Planning with the original prescription and escalated prescription, respectively. Escalated prescription adds 1 Gy/fraction to the original prescription. Manually-created planning volumes were excluded in the optimization goals in order to assess the planning efficiency and quality simultaneously. Critical organs with closest proximity were used to determine the plan normalization to ensure the OAR sparing. Dosimetric parameters including D100, and conformity index (CI) were assessed. Results: Auto-plans directly generate acceptable plans for 70% of the cases without necessity of further improvement, and two more iterations at most are necessary for the rest of the cases. For the pancreas SBRT plans with the original prescription, autoplans resulted in favorable target coverage and PTV conformity (D100 = 96.3% ± 1.48%; CI = 0.88 ± 0.06). For the plans with the escalated prescriptions, no significant target under-dosage was observed, and PTV conformity remains reasonable (D100 = 93.3% ± 3.8%, and CI = 0.84 ± 0.05). Conclusion: Automatic planning, without substantial human-intervention process, results in reasonable PTV coverage and PTV conformity on the premise of adequate OAR sparing for the pancreas SBRT plans with escalated prescription. The results highlight the potential of autoplanning as a dose escalation strategy for pancreas SBRT treatment planning. Further investigations with a larger number of patients are necessary. The project is partially supported by Philips Medical Systems.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

SU-F-J-125: Effects of Couch Position Variability On Dosimetric Accuracy with An MRI-Guided Co-60 Radiation Therapy Machine

Purpose: Magnetic resonance imaging (MRI) guidance in radiation therapy brings real-time imaging and adaptive planning into the treatment vault where it can account for interfraction and intrafraction movement of soft tissue. The only commercially-available MRI-guided radiation therapy device is a three-head 60Co and MRI system with an integrated treatment planning system (TPS). An up to 20% attenuation of the beam by the couch is well modeled in the TPS. However, variations in the patient’s day-to-day position introduce discrepancies in the actual couch position relative its location as modeled in the treatment plan. For this reason, our institution avoids plans with beams that pass through or near the couch edges. This study looks at plans without restriction on beam angles and investigates the effects of couch shift by simulating shifts of the couch relative to the patient, in order to determine whether couch edge avoidance restrictions can be lifted. Methods: A total of 27 plans from 23 patients were investigated. Couch shifts of 1 and 2 cm were introduced in combinations of lateral and vertical direction to simulate variations in patient positioning on the couch giving 16 shifted plans per reference plan. The shift values of 1 and 2 cm were based on shifts recorded in 320 treatment fractions. Results: Measured couch attenuation versus TPS modeled agreed within 2.1%. Planning Target Volume (PTV) D95 changed less than 1% for 1 and 2 cm couch shifts in only the x-direction and less than 3% for all directions. Conclusion: The dosimetry of all plans with shifts up to ±2 cm was within reasonable clinical tolerances. Robustness of a plan to couch shifts can be tested in the TPS. Inclusion of beams traversing the couch edges should be considered if an improvement in plan quality or delivery time can be achieved.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

SU-F-T-39: Comparing Nomograms for Ordering of Palladium-103 Seeds for Dynamic Intraoperative Prostate Seed Implantation

Purpose: Several nomograms exist for the purpose of ordering palladium- 103 seeds for permanent prostate seed implants. Excess seeds pose additional radiation safety risks and increase the cost of care. This study compared three seed ordering nomograms with seed counts from dynamic intra-operative PSI to determine (1) the cause of excess seeds and (2) the optimal nomogram for our institution. Methods: Pre-operative and intra-operative clinical data were collected for 100 Gy (n=151) and 125 Gy (n=224) prostate seed implants. The number of implanted seeds which would have given D90=100% was normalized to that criteria and seed strength of 2U. This was plotted against intra-operative prostate volume and compared to two previously published nomograms and an in-house nomogram. A linear fit was produced and confidence intervals were calculated. The causes of excess seeds were assessed by comparing pre- and intra-operative prostate volumes, variability of D90 around 100%, and variance of seed strength from 2U. Results: Of the 375 total cases, 97.6% had excess seeds. On average, 27.17±12.91% of ordered seeds were wasted. Of this percentage, 6.98±5.47% of excess seeds were due to overestimation of pre-operative prostate volume, 1.10±0.88% were due to D90<100%, 1.17±0.67% were due to seed strength over 2U, and 17.36±7.79% could not be directly attributed to a specific reason. The latter percentage may be due to overestimation of the in-house nomogram. Two of three nomograms substantially overestimated the number of seeds required. The third nomogram underestimated the required seed number for smaller prostate treatment volume. A linear fit to the clinical data was derived and 99.9% confidence intervals were calculated. Conclusion: Over 85% of clinical cases wasted over 15% of ordered seeds. Two of three nomograms overestimated the required number of seeds. The upper 99.9% C.I. of the clinical data may provide a more reasonable nomogram for Pd-103 seed ordering.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

SU-G-IeP4-11: Monitoring Tumor Growth in Subcutaneous Murine Tumor Model in Vivo: A Comparison Between MRI and Small Animal CT

Purpose: The purpose of the study is to compare the volume measurement of subcutaneous tumors in mice with different imaging platforms, namely a GE MRI and a Sofie-Biosciences small animal CT scanner. Methods: A549 human lung carcinoma cells and FaDu human head and neck squamous cell carcinoma cells were implanted subcutaneously into flanks of nude mice. Three FaDu tumors and three A549 tumors were included in this study. The MRI scans were done with a GE Signa 1.5 Tesla MR scanner using a fast T2-weighted sequence (70mm FOV and 1.2mm slice thickness), while the CT scans were done with the CT scanner on a Sofie-Biosciences G8 PET/CT platform dedicated for small animal studies (48mm FOV and 0.2mm slice thickness). Imaging contrast agent was not used in this study. Based on the DICOM images from MRI and CT scans, the tumors were contoured with Philips DICOM Viewer and the tumor volumes were obtained by summing up the contoured area and multiplied by the slice thickness. Results: The volume measurements based on the CT scans agree reasonably with that obtained with MR images for the subcutaneous tumors. The mean difference in the absolute tumor volumes between MRI- and CT-based measurements was found to be −6.2% ± 1.0%, with the difference defined as (VMR – VCT)*100%/VMR. Furthermore, we evaluated the normalized tumor volumes, which were defined for each tumor as V/V{sub 0} where V{sub 0} stands for the volume from the first MR or CT scan. The mean difference in the normalized tumor volumes was found to be 0.10% ± 0.96%. Conclusion: Despite the fact that the difference between normal and abnormal tissues is often less clear on small animal CT images than on MR images, one can still obtain reasonable tumor volume information with the small animal CT scans for subcutaneous murine xenograft models.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

Enhanced nearfield acoustic holography for larger distances of reconstructions using fixed parameter Tikhonov regularization

This paper evaluates the performance of various regularization parameter choice methods applied to different approaches of nearfield acoustic holography when a very nearfield measurement is not possible. For a fixed grid resolution, the larger the hologram distance, the larger the error in the naive nearfield acoustic holography reconstructions. These errors can be smoothed out by using an appropriate order of regularization. In conclusion, this study shows that by using a fixed/manual choice of regularization parameter, instead of automated parameter choice methods, reasonably accurate reconstructions can be obtained even when the hologram distance is 16 times larger than the grid resolution.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2020

Multichannel spectral estimation in acoustics: A state-space approach

Spectral estimation is a necessary methodology to analyze the frequency content of noisy data sets especially in acoustic applications. Many spectral techniques have evolved starting with the classical Fourier transform methods based on the well-known Wiener-Khintchine relationship relating the covariance-to-spectral density as a transform pair culminating with more elegant model-based parametric techniques that apply prior knowledge of the data to produce a high-resolution spectral estimate. Multichannel spectral representations are a class of both nonparametric, as well as parametric, estimators that provide improved spectral estimates. In any case, classical nonparametric multichannel techniques can provide reasonable estimates when coupled with peak-peaking methods as long as the signal levels are reasonably high. Furthermore, parametric multichannel methods can perform quite well in low signal level environments even when applying simple peak-picking techniques. In this paper, the performance of both nonparametric (periodogram) and parametric (state-space) multichannel spectral estimation methods are investigated when applied to both synthesized noisy structural vibration data as well as data obtained from a sounding rocket flight. It is demonstrated that for the multichannel problem, state-space techniques provide improved performance, offering a parametric alternative compared to classical methods.

42 ENGINEERING↗

DOE OSTI2018

Erratum to: “The Fluorescence and Electronic Structure of Phenyl-Substituted Tetraazachlorin Molecules” [Optics and Spectroscopy 117, 722 (2014)]

should read “porphyrazine” instead of “porphyrazin”;should read “intersystem crossing” instead of “intercombinational conversion”;should read “mirror-symmetrical” instead of “reflection-symmetric”;should read “fluorescence enhancement” instead of “fluorescence buildup.”Page 722, Abstract, lines 9–10 from the top, the sentence should read:This characteristic increases upon tetrapyrrole phenylation.Page 727, left column, lines 17–18 from the top, the sentence should read:The vibronic transition parts of the emission spectrum are diffuse, (…)Page 727, left column, lines 29–30 from the top, the sentence should read:Note that the Stokes shift in these cases is relatively large.Page 729, left column, lines 8–10 from the bottom, the sentence should read:For H{sub 2}Ph{sub 8}TAC{sup mp} and H{sub 2}Ph{sub 6}TAC{sup tm}, the enhancement of fluorescence is weaker than in the former case: on cooling, τ{sub F} is increased by a factor of 4–5 in MTHF and by a factor of only 2.6–3 in toluene.Page 729, right column, lines 9–10 from the footnote, the sentence should read:It is seen from Table 1 that our results agree reasonably well with previously reported data.Page 730, left column, lines 16–19 from the top, the sentence should read:The lifetime for the outgassed H{sub 2}TAP solution intoluene (τ{sub T}{sup 0}) was measured by A.S. Stasheuski as phosphorescence decay at λ{sub reg} = 1070 nm using the setup described in [29].Page 730, left column, lines 20–23 from the top, the sentence should read:The τ{sub T} value derived from the kinetics of the rise of singlet oxygen luminescence [26] for the nonoutgassed solution at λ{sub reg} = 1272 nm is 162 ns;Page 730, right column, lines 25–27 from the top, the sentence should read:Therefore, for H{sub 2}TAP (λ{sub F}{sup 00}≈ 620 nm), the internal conversion probability should not be high.Page 731, left column, the heading of Table 2 should read:Bond lengths in the porphine macrocycle (Å).Page 731, left column, lines 3–6 from the top, the sentence should read:For elucidating the mechanism of the deactivation of the S{sub 1} state, it was of essential interest to see whether the enhancement of H{sub 2}TAP fluorescence would be observed at 77 K.Page 733, left column, lines 2–3 from the top, the sentence should read:The corresponding difference for the H{sub 2}P–H{sub 2}C pair is 0.013 Å.Page 733, left column, lines 14–16 from the top, the sentence should read:The macrocycle undergoes additional contraction, and the symmetry of its conjugated system is very close to D{sub 2h}.Page 733, right column, line 21 from the top should read:Replacement of the methine bridges (…)Page 734, left column, lines 8–11 from the figure caption, the sentence should read:This is the main reason of the large bathochromic shift of the Soret band of H{sub 2}Ph{sub 8}TAP and MgPh{sub 8}TAP [16] relative to H{sub 2}TAP and MgTAP, respectively.Page 734, left column, lines 1–4 from the bottom, the sentence should read:The complete INDO/Sm calculation yields the corresponding quantitative characteristics, which are in good agreement with experimental data (see below).Page 740, left column, reference no. 25 should read:25. V. A. Galievsky, A. S. Stasheuski, V. V. Kiselyov, A. I. Shabusov, M. V. Belkov, and B. M. Dzhagarov, Instrum. Exp. Tech. 53, 568 (2010).25. V. A. Galievsky, A. S. Stasheuski, V. V. Kiselyov, A. I. Shabusov, M. V. Belkov, and B. M. Dzhagarov, Instrum. Exp. Tech. 53, 568 (2010).30. V. L. Ermolaev and E. B. Sveshnikova, Acta Phys. Pol. 34, 771 (1968).

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2018

Effect of Cr Spacer on Structural and Magnetic Properties of Fe/Gd Multilayers

Here, we analyze the role of a thin Cr spacer between Fe and Gd layers on the structure and magnetic properties of a [Fe(35 Å)/Cr(t Cr )/Gd(50 Å)/Cr(t Cr )] 12 superlattice. Samples without the Cr spacer (t Cr = 0) and with a thin spacer (t Cr = 4 Å) are investigated using X-ray diffraction, polarized neutron and resonance X-ray magnetic reflectometry, static magnetometry, magneto-optical Kerr effect, and ferromagnetic resonance techniques. Magnetic properties are studied experimentally in a wide temperature range 4–300 K and analyzed theoretically using numerical simulation on the basis of the mean-field model. We show that a reasonable agreement with the experimental data can be obtained considering temperature dependence of the effective field parameter in gadolinium layers. In conclusion, the analysis of the experimental data shows that besides a strong reduction of the antiferromagnetic coupling between Fe and Gd, the introduction of Cr spacers into Fe/Gd superlattice leads to modification of both structural and magnetic characteristics of the ferromagnetic layers.

36 MATERIALS SCIENCE↗

DOE OSTI2012

Exotic states and rare B {sub s }-decays in the covariant quark model

The consequences of treating X(3872) meson as a tetraquark bound state are explored. The covariant quark model that effectively includes infrared confinement is employed as a dynamical framework. The strong decay widths of observed channels X → J/Ψ + 2π(3π) and X → + D-bar {sup 0} + D{sup 0} + π{sup 0} are calculated via the intermediate off-shell states X → J/Ψ + ρ(ω) and X → D + D*. For reasonable values of the size parameter Λ{sub X }of X(3872) meson the results are found to be consistent with the available experimental data. The possible impact of X(3872) on the behavior of the total cross section of J/Ψ dissociation by light particles within the framework of the s-channel dominance description is also discussed. The single-photon decay X → γ + J/Ψ is then analyzed. To introduce electromagnetic interactions, a nonlocal effective Lagrangian, which describes an interaction of X(3872) meson with its four constituent quarks, is gauged by using the P-exponential path-independent formalism. The matrix element of the transition X → γ + J/Ψ is evaluated and its gauge invariance is proved. The decay width of X → γ + J/Ψ and longitudinal/transverse composition of J/Ψ in this decay are calculated. For a reasonable value of the size parameter Λ{sub X }of X(3872) meson, the results are found to be consistent with the available experimental data. The helicity and multipole amplitudes of the process are computed as well, and the procedure of obtaining them from the covariant transition amplitude by using the covariant projection is described. Considering the surge of great interest to the problem of CP violation recently observed in a B {sub s }−{ie749-2} system, decays of B {sub s }to D-{ie749-3} and color suppressed decay B {sub s }→ J/Ψ ϕ attracted the attention of both theorists and experimentalists. We find new values for the covariant quark model parameters (with built-in infrared confinement) in the meson sector by fitting the leptonic decay constants and a number of electromagnetic decays, and then evaluate in a parameter-free way the form factors of B(B {sub s }) → P(V) transitions within an entire kinematic range of the momentum transfer. Our results are applied to calculating the widths of nonleptonic B {sub s }decays to D{sup −}{sub s }D{sup +}{sub s }, {ie749-4}, and {ie749-5}. The largest contribution to Δγ for B {sub s }-{ie749-6} system comes from these modes. The nonleptonic decay B {sub s }→ J/Ψϕ is also considered. Though this decay mode is color suppressed it has important implications in the search for possible CP-violating novel physics effects in B {sub s }-{ie749-7} mixing.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

The electromagnetic Sigma-to-Lambda hyperon transition form factors at low energies

Using dispersion theory the low-energy electromagnetic form factors for the transition of a Sigma to a Lambda hyperon are related to the pion vector form factor. The additionally required input, i.e. the two-pion-Sigma-Lambda amplitudes are determined from relativistic next-to-leading-order (NLO) baryon chiral perturbation theory including the baryons from the octet and optionally from the decuplet. Pion rescattering is again taken into account by dispersion theory. It turns out that the inclusion of decuplet baryons is not an option but a necessity to obtain reasonable results. The electric transition form factor remains very small in the whole low-energy region. The magnetic transition form factor depends strongly on one not very well determined low-energy constant of the NLO Lagrangian. Furthermore, one obtains reasonable predictive power if this low-energy constant is determined from a measurement of the magnetic transition radius. Such a measurement can be performed at the future Facility for Antiproton and Ion Research (FAIR).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Diffeomorphism invariance and quantum mechanical paradoxes

Paradoxes in gravitational physics, such as grandfather paradoxes with closed timelike curves or the AMPS paradox, are often constructed in a weak gravity regime but upon further examination engender strong gravitational responses such as unstable Cauchy horizons or firewalls. In contrast, some proposed paradoxes in nonrelativistic quantum mechanics ignore gravity completely. Such nonrelativistic proposed paradoxes are often not gauge invariant — they use local operators which should be forbidden by diffeomorphism-invariant quantum gravity. Ignoring this complication is reasonable if there is a consistent weak gravity regime where the paradox can be formulated with gauge invariant observables up to some order in Newton’s constant. Here, we show that this approach remains inconsistent due to a lack of analyticity of the necessary solutions. As a consequence, there is no consistent weak gravity, diffeomorphism invariant embedding of such paradoxes—just as in other gravitational paradoxes they generate a strong gravitational response and are in principle sensitive to quantum gravity.

quantum gravity↗

DOE OSTI2026

Emerging Flexible Designs for Geospatial Multimodal Foundation Models

Foundation models are rapidly transforming Earth observation by enabling scalable pretraining across diverse unlabeled geospatial modalities. However, their architectural diversity—ranging from encoder-only to encoder-decoder and masked autoencoding paradigms—makes it challenging to assess performance trade-offs in a consistent manner. In this work, we present an apples-to-apples comparison of leading FM architectures designed for geospatial multimodal reasoning, with a particular focus on flexibility across varied spectral band configurations. We standardize pretraining using identical self-supervised learning objectives and training datasets, and evaluate all models under consistent parameterization on the GEOBench benchmark across classification and segmentation tasks. Our results offer new insights into the design trade-offs between model flexibility, modality alignment, and downstream task performance. By highlighting architectural strengths and limitations under controlled conditions, this study provides practical guidance for building next-generation geospatial foundation models capable of robust multimodal reasoning.

Ambrozio Dias, Philipe [ORNL] (ORCID:0000000194277↗

DOE OSTI2021

Effects of Radiation-Induced Defects on Corrosion

The next generation of nuclear reactors will expose materials to conditions that, in some cases, are even more extreme than those in current fission reactors, inevitably leading to new materials science challenges. Radiation-induced damage and corrosion are two key phenomena that must be understood both independently and synergistically, but their interactions are often convoluted. In the light water reactor community, a tremendous amount of work has been done to illuminate irradiation-corrosion effects, and similar efforts are under way for heavy liquid metal and molten salt environments. While certain effects, such as radiolysis and irradiation-assisted stress corrosion cracking, are reasonably well established, the basic science of how irradiation-induced defects in the base material and the corrosion layer influence the corrosion process still presents many unanswered questions. In this review, we summarize the work that has been done to understand these coupled extremes, highlight the complex nature of this problem, and identify key knowledge gaps.

36 MATERIALS SCIENCE↗