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DOE OSTI2011

CONSTRAINED-TRANSPORT MAGNETOHYDRODYNAMICS WITH ADAPTIVE MESH REFINEMENT IN CHARM

We present the implementation of a three-dimensional, second-order accurate Godunov-type algorithm for magnetohydrodynamics (MHD) in the adaptive-mesh-refinement (AMR) cosmological code CHARM. The algorithm is based on the full 12-solve spatially unsplit corner-transport-upwind (CTU) scheme. The fluid quantities are cell-centered and are updated using the piecewise-parabolic method (PPM), while the magnetic field variables are face-centered and are evolved through application of the Stokes theorem on cell edges via a constrained-transport (CT) method. The so-called multidimensional MHD source terms required in the predictor step for high-order accuracy are applied in a simplified form which reduces their complexity in three dimensions without loss of accuracy or robustness. The algorithm is implemented on an AMR framework which requires specific synchronization steps across refinement levels. These include face-centered restriction and prolongation operations and a reflux-curl operation, which maintains a solenoidal magnetic field across refinement boundaries. The code is tested against a large suite of test problems, including convergence tests in smooth flows, shock-tube tests, classical two- and three-dimensional MHD tests, a three-dimensional shock-cloud interaction problem, and the formation of a cluster of galaxies in a fully cosmological context. The magnetic field divergence is shown to remain negligible throughout.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Effect of lithium coating on long pulse high performance plasma discharges in EAST

Control of impurities, fuel recycling and hydrogen content by lithium evaporative coatings and real-time lithium powder injection (LPI) in EAST are studied for high performance H-mode discharges of up to ~100 s. The results show that the lithium evaporative coatings significantly reduced both the low-Z impurity carbon and high-Z impurity tungsten as well as molybdenum concentration in the plasmas, and the impurities concentration significantly reduced with the accumulated lithium coatings and maintained well afterwards. Specifically the high-Z tungsten core impurity concentration was maintained between 3 ppm–15 ppm during the 101 s H-mode discharge, which is acceptable for the long pulse operation. In addition, real-time wall conditioning via LPI successfully reduced the core high-Z metal impurities by 50% during ~35 s long pulse H-mode discharge, exhibiting strong compatibility between real-time LPI with long pulse discharges. In addition, evaporative lithium coatings demonstrated fuel recycling control, with fuel recycling obviously reducing with lithium coatings and maintaining well afterwards. Also, the lithium evaporative coatings reduced the hydrogen minority species content, represented by the density ratio H/(H + D), from ~50% down to ~5% with accumulated lithium coatings; low hydrogen fraction improved the ICRF minority heating efficiency. Finally the real-time LPI reduced the recycling coefficient R global from 0.95 to 0.82. With these wall conditionings help, the plasma density controlled well during the 101 s long pulse H-mode discharge. Furthermore, these results provide valuable references on impurities, fuel recycling and hydrogen content control for future longer pulse high performance H-mode operation (≥400 s) in EAST and future fusion devices.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

Compatibility of divertor detachment and ELM suppression in DIII-D high- β p plasmas with ITER-similar shape

Abstract Integration of transient and steady-state divertor heat fluxes control with a high-performance core is necessary for future fusion reactors. In recent DIII-D high- β p experiments, divertor detachment and simultaneous edge localized mode (ELM) suppression are demonstrated while the plasma confinement quality is maintained high in ITER-similar shape. By optimizing the neon injection in high- β p scenario with ITER-similar shape, deep detachment and ELM suppression are achieved with a high-performance core ( β N ∼ 2.8, β p ∼ 2.3) at q 95 ∼ 7.5. Partial divertor detachment and suppression of large ELMs are achieved at q 95 ∼ 6. The stability analyses suggest that with low neon injection, the density pedestal becomes higher and steeper and the T i profile also increases, therefore the increased edge pressure and higher current density destabilize the Peeling-Ballooning mode (PBM), which would lead to a large ELM collapse. With strong neon gas puffing, the significantly reduced pedestal pressure and current density, due to the degraded T e pedestal, lead to the stabilization of PBM and ELMs are suppressed. For both cases, the coupling between the large radius internal transport barrier (ITB) and edge pedestal is the key reason for maintaining high global performance. The formation of large radius ITB compensates for pedestal degradation. Such results could provide an attractive scenario to well control the transient and steady-state heat flux onto the divertor plates while maintaining good plasma performance, which is an important step toward the steady-state operation of future fusion reactors.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2025

Benchmarking the design of the cryogenics system for the underground argon in DarkSide-20k

DarkSide-20k (DS-20k) is a dark matter detection experimentunder construction at the Laboratori Nazionali del Gran Sasso (LNGS)in Italy. It utilises ∼ 100 t of low radioactivity argon from anunderground source (UAr) in its inner detector, with half serving astarget in a dual-phase time projection chamber (TPC). The UArcryogenics system must maintain stable thermodynamic conditionsthroughout the experiment's lifetime of over10 years. Continuous removal ofimpurities and radon from the UAr is essential for maximising signalyield and mitigating background. We are developing an efficient andpowerful cryogenics system with a gas purification loop with atarget circulation rate of1000 slpm. Central to itsdesign is a condenser operated with liquid nitrogen which is pairedwith a gas heat exchanger cascade, delivering a combined coolingpower of more than 8 kW. Here wepresent the design choices in view of the DS-20k requirements, inparticular the condenser's working principle and the coolingcontrol, and we show test results obtained with a dedicatedbenchmarking platform at CERN and LNGS. We find that the thermalefficiency of the recirculation loop, defined in terms of nitrogenconsumption per argon flow rate, is95 % and the pressure in the testcryostat can be maintained within±(0.1–0.2) mbar. Wefurther detail a 5-day cool-down procedure of the test cryostat,maintaining a cooling rate typically within-2 K/h, as required for theDS-20k inner detector. Additionally, we assess the circuit's flowresistance, and the heat transfer capabilities of two heat exchangergeometries for argon phase change, used to provide gas forrecirculation. We conclude by discussing how our findings influencethe finalisation of the system design, including necessarymodifications to meet requirements and ongoing testing activities.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2011

THE STEPPENWOLF: A PROPOSAL FOR A HABITABLE PLANET IN INTERSTELLAR SPACE

Rogue planets have been ejected from their planetary system. We investigate the possibility that a rogue planet could maintain a liquid ocean under layers of thermally insulating water ice and frozen gas as a result of geothermal heat flux. We find that a rogue planet of Earth-like composition and age could maintain a subglacial liquid ocean if it were {approx}3.5 times more massive than Earth, corresponding to {approx}8 km of ice. Suppression of the melting point by contaminants, a layer of frozen gas, or a larger complement of water could significantly reduce the planetary mass that is required to maintain a liquid ocean. Such a planet could be detected from reflected solar radiation, and its thermal emission could be characterized in the far-IR if it were to pass within O(1000) AU of Earth.

42 ENGINEERING↗

DOE OSTI2024

Interaction of N-methylmesoporphyrin IX with a hybrid left-/right-handed G-quadruplex motif from the promoter of the SLC2A1 gene

Abstract Left-handed G-quadruplexes (LHG4s) belong to a class of recently discovered noncanonical DNA structures under the larger umbrella of G-quadruplex DNAs (G4s). The biological relevance of these structures and their ability to be targeted with classical G4 ligands is underexplored. Here, we explore whether the putative LHG4 DNA sequence from the SLC2A1 oncogene promoter maintains its left-handed characteristics upon addition of nucleotides in the 5′- and 3′-direction from its genomic context. We also investigate whether this sequence interacts with a well-established G4 binder, N-methylmesoporphyrin IX (NMM). We employed biophysical and X-ray structural studies to address these questions. Our results indicate that the sequence d[G(TGG)3TGA(TGG)4] (termed here as SLC) adopts a two-subunit, four-tetrad hybrid left-/right-handed G4 (LH/RHG4) topology. Addition of 5′-G or 5′-GG abolishes the left-handed fold in one subunit, while the addition of 3′-C or 3′-CA maintains the original fold. X-ray crystal structure analyses show that SLC maintains the same hybrid LH/RHG4 fold in the solid state and that NMM stacks onto the right-handed subunit of SLC. NMM binds to SLC with a 1:1 stoichiometry and a moderate-to-tight binding constant of 15 μM−1. This work deepens our understanding of LHG4 structures and their binding with traditional G4 ligands.

Seth, Paul↗

DOE OSTI2020

Bacterial Community Members Increase Bacillus subtilis Maintenance on the Roots of Arabidopsis thaliana

Plant-growth-promoting bacteria (PGPB) are used to improve plant health and promote crop production. However, because some PGPB (including Bacillus subtilis) do not maintain substantial colonization on plant roots over time, it is unclear how effective PGPB are throughout the plant growing cycle. A better understanding of the dynamics of plant root community assembly is needed to develop and harness the potential of PGPB. Although B. subtilis is often a member of the root microbiome, it does not efficiently monoassociate with plant roots. We hypothesized that B. subtilis may require other primary colonizers to efficiently associate with plant roots. We utilized a previously designed hydroponic system to add bacteria to Arabidopsis thaliana roots and monitor their attachment over time. We inoculated seedlings with B. subtilis and individual bacterial isolates from the native A. thaliana root microbiome either alone or together. We then measured how the coinoculum affected the ability of B. subtilis to colonize and maintain on A. thaliana roots. We screened 96 fully genome-sequenced strains and identified five bacterial strains that were able to significantly improve the maintenance of B. subtilis. Three of these rhizobacteria also increased the maintenance of two strains of B. amyloliquefaciens commonly used in commercially available bioadditives. These results not only illustrate the utility of this model system to address questions about plant–microbe interactions and how other bacteria affect the ability of PGPB to maintain their relationships with plant roots but also may help inform future agricultural interventions to increase crop yields.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2012

Architecture-based multiscale computational modeling of plant cell wall mechanics to examine the hydrogen-bonding hypothesis of cell wall network structure model

A primary plant cell wall network was computationally modeled using the finite element approach to study the hypothesis of hemicellulose (HC) tethering with the cellulose microfibrils (CMFs) as one of the major load-bearing mechanisms of the growing cell wall. A computational primary cell wall network fragment (10 × 10 μm) comprising typical compositions and properties of CMFs and HC was modeled with well-aligned CMFs. The tethering of HC to CMFs is modeled in accordance with the strength of the hydrogen bonding by implementing a specific load-bearing connection (i.e. the joint element). The introduction of the CMF-HC interaction to the computational cell wall network model is a key to the quantitative examination of the mechanical consequences of cell wall structure models, including the tethering HC model. When the cell wall network models with and without joint elements were compared, the hydrogen bond exhibited a significant contribution to the overall stiffness of the cell wall network fragment. When the cell wall network model was stretched 1% in the transverse direction, the tethering of CMF-HC via hydrogen bonds was not strong enough to maintain its integrity. When the cell wall network model was stretched 1% in the longitudinal direction, the tethering provided comparable strength to maintain its integrity. This substantial anisotropy suggests that the HC tethering with hydrogen bonds alone does not manifest sufficient energy to maintain the integrity of the cell wall during its growth (i.e. other mechanisms are present to ensure the cell wall shape).

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2025

Reducing Communication Overhead in Federated Learning for Network Anomaly Detection with Adaptive Client Selection

Communication overhead in federated learning (FL) poses a significant challenge for network anomaly detection systems, where the myriad of client configurations and network conditions can severely impact system efficiency and detection accuracy. While existing approaches attempt to address this through individual optimization techniques, they often fail to maintain the delicate balance between reduced overhead and detection performance. This paper presents an adaptive FL framework that dynamically combines batch size optimization, client selection, and asynchronous updates to achieve efficient anomaly detection. Through extensive profiling and experimental analysis on two distinct datasets-UNSW-NBIS for general network traffic and ROAD for automotive networks-our framework reduces communication overhead by 97.6%; (from 700.0s to 16.8s) compared to synchronous baseline approaches while maintaining comparable detection accuracy (95.10%; vs. 95.12%;). Statistical validation using Mann-Whitney U test confirms significant improvements (p < 0.05) over existing FL approaches across both datasets, demonstrating the framework's adaptability to different network security contexts. Detailed profiling analysis reveals the efficiency gains through dramatic reductions in GPU operations and memory transfers while maintaining robust detection performance under varying client conditions.

Marfo, William [University of Texas at El Paso]↗

DOE OSTI2022

Machine Learning Based Network Parameter Estimation Using AMI Data

The expansion of distribution power system and the growing penetration of distributed energy resources present new challenges for situational awareness. Calibrating the extended system model with sensor measurements and maintaining the usability is critical for utilities. This paper presents a distribution network parameter estimation (DNPE) approach using machine learning (ML) and metering data that improve the quality of extended distribution power system modeling. The reliability model can improve the ability of endpoint data to be translated into network-level situational awareness in real time and help distribution system operators (DSOs) solve branch flow and voltage problems. In addition, a data analytic and automate processing scheme is proposed to improve the sensor data quality and prevent misleading information. The effectiveness of the proposed method is verified with actual advanced metering infrastructure (AMI) data on a real utility feeder model, while considering the higher penetration of photovoltaic power generation. The test of DNPE and study results are demonstrated in this paper.

Parameter estimation, machine learning, power dist↗

DOE OSTI2017

Optimal Load-Side Control for Frequency Regulation in Smart Grids

Frequency control rebalances supply and demand while maintaining the network state within operational margins. It is implemented using fast ramping reserves that are expensive and wasteful, and which are expected to become increasingly necessary with the current acceleration of renewable penetration. The most promising solution to this problem is the use of demand response, i.e., load participation in frequency control. Yet it is still unclear how to efficiently integrate load participation without introducing instabilities and violating operational constraints. In this paper, we present a comprehensive load-side frequency control mechanism that can maintain the grid within operational constraints. In particular, our controllers can rebalance supply and demand after disturbances, restore the frequency to its nominal value, and preserve interarea power flows. Furthermore, our controllers are distributed (unlike the currently implemented frequency control), can allocate load updates optimally, and can maintain line flows within thermal limits. We prove that such a distributed load-side control is globally asymptotically stable and robust to unknown load parameters. We illustrate its effectiveness through simulations.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2016

Application of extremum seeking for time-varying systems to resonance control of RF cavities

A recently developed form of extremum seeking for time-varying systems is implemented in hardware for the resonance control of radio-frequency cavities without phase measurements. Normal conducting RF cavity resonance control is performed via a slug tuner, while superconducting TESLA-type cavity resonance control is performed via piezo actuators. The controller maintains resonance by minimizing reflected power by utilizing model-independent adaptive feedback. Unlike standard phase-measurement-based resonance control, the presented approach is not sensitive to arbitrary phase shifts of the RF signals due to temperature-dependent cable length or phasemeasurement hardware changes. The phase independence of this method removes common slowly varying drifts and required periodic recalibration of phase-based methods. A general overview of the adaptive controller is presented along with the proof of principle experimental results at room temperature. Lastly, this method allows us to both maintain a cavity at a desired resonance frequency and also to dynamically modify its resonance frequency to track the unknown time-varying frequency of an RF source, thereby maintaining maximal cavity field strength, based only on power-level measurements.

47 OTHER INSTRUMENTATION↗

DOE OSTI2024

Fast Neutron Irradiation of a Multichannel JFET-Based Optical Encoder

Modern electrical components are susceptible to damage from high levels of radiation and extreme temperatures found near reactors in terrestrial nuclear power plants and in aerospace applications. Radiation-hardened electronics are being developed, largely for the aerospace industry, but they sometimes rely on application-specific, small-batch semiconductor fabrication processes. These processes tend to be prohibitively expensive to develop and maintain outside major industrial facilities or governmental agencies. Recently, commercially available, nonradiation-rated junction-gate field-effect transistors (JFETs) were shown to maintain their functionality at gamma doses exceeding 1 MGy, suggesting that nonrated, commercially available electrical components could be used to develop systems that are tolerant to ionizing radiation. However, gamma ray survival is not indicative of neutron dose survival, and few studies characterize JFETs under neutron irradiation. To address this knowledge gap, a JFET-based analog multiplexer and optical pulsewidth modulation (PWM) encoder was developed and irradiated using a 252 Cf source to 1.6×10 13 n/cm 2 . The multiplexed optical encoder (MOE) system maintained functionality throughout testing and showed little evidence of radiation effects. These results indicate that circuitry tolerant to fast neutron damage can be developed using low-cost, nonradiation-rated, commercially available JFETs, which could provide a lower production cost alternative to specialized semiconductor processes when designing and building electronics better able to survive neutron irradiation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Tritium Transport Modeling at the Pore Scale in Ceramic Breeder Materials Using TMAP8

Fusion reactors depend on the blanket material to breed and release tritium at the same rate or faster than it is consumed by the fusion reaction. Cellular ceramic breeders (CCBs) are dense materials that can maintain a high tritium breeding ratio while promoting tritium release because of highly connected pores. Assessing the tritium breeding capabilities of these materials requires a combination of extensive experimental and modeling efforts. In this work, we develop and calibrate a multiphysics model of tritium transport. This novel model accounts for ceramic and pore diffusion, trapping and detrapping, and several surface reactions at the pore surface. We perform a sensitivity analysis and calibrate the model by comparing its predictions against experimental measurements of deuterium absorption. The calibrated model is then used to model tritium absorption in samples with different pore microstructures to investigate the effect of pore interconnectivity on tritium absorption. The model is part of the development of the multiscale, multiphysics framework for tritium transport [i.e., the Tritium Migration Analysis Program (TMAP8)], which is itself built on top of the finite-element multiphysics framework multiphysics object-oriented simulation environment (MOOSE). This study demonstrates some of TMAP8’s capabilities and is the first step toward assessing the tritium breeding capabilities of ceramic breeder material designs.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Preserving Command Line Workflow for a Package Management System using ASCII DAG Visualization

Package managers provide ease of access to applications by removing the time-consuming and sometimes completely prohibitive barrier of successfully building, installing, and maintaining the software for a system. A package dependency contains dependencies between all packages required to build and run the target software. Package management system developers, package maintainers, and users may consult the dependency graph when a simple listing is insufficient for their analyses. However, users working in a remote command line environment must disrupt their workflow to visualize dependency graphs in graphical programs, possibly needing to move files between devices or incur forwarding lag. Such is the case for users of Spack, an open source package management system originally developed to ease the complex builds required by supercomputing environments. To preserve the command line workflow of Spack, we develop an interactive ASCII visualization for its dependency graphs. Through interviews with Spack maintainers, we identify user goals and corresponding visual tasks for dependency graphs. We evaluate the use of our visualization through a command line-centered study, comparing it to the system's two existing approaches. We observe that despite the limitations of the ASCII representation, our visualization is preferred by participants when approached from a command line interface workflow.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2022

Contribution of Tibetan Plateau ecosystems to local and remote precipitation through moisture recycling

The ecosystems of the Tibetan Plateau (TP) provide multiple important ecosystem services that benefit both local populations and those beyond, such as through climate regulation services on precipitation for East Asia and China. However, the precipitation regulation service of the TP ecosystems for supplying moisture and maintaining precipitation is yet to be evaluated. In this study, we used the moisture recycling framework and a moisture tracking model to quantify the precipitation regulation services of TP ecosystems for their contribution to precipitation. We found TP ecosystems contributed substantially to local and downwind precipitation, with a declined contribution from 221 mm/year for the TP and neighboring areas, to <10 mm/year for eastern China and other surrounding countries. Among ecosystem types, grassland contributed most to precipitation, followed by barren and snow lands, forests, and shrublands. In terms of seasonality, precipitation contribution from TP ecosystems was greater in summer months than in non-summer months for western China, while the opposite was true for eastern China – though the magnitude was much smaller. Over the past two decades, the significant evapotranspiration increases in TP translated to a widespread increase in precipitation contribution for TP and downwind beneficiary regions from 2000 to 2020. Our study provides a quantitative way to understand the precipitation regulation services of TP ecosystems through moisture recycling, substantiating their key role to safeguard precipitation and the water cycle for downwind regions– effectively acting as an ecological security shelter that could be perceived by the public.

Li, Yan↗

DOE OSTI2011

Evaluation of the dosimetric impact of interfractional anatomical variations on prostate proton therapy using daily in-room CT images

Purpose: To quantify interfractional anatomical variations and their dosimetric impact during the course of fractionated proton therapy (PT) of prostate cancer and to assess the robustness of the current treatment planning techniques. Methods: Simulation and daily in-room CT scans from ten prostate carcinoma patients were analyzed. PT treatment plans (78 Gy in 39 fractions of 2 Gy) were created on the simulation CT, delivering 25 fractions to PTV1 (expanded from prostate and seminal vesicles), followed by 14 boost fractions to PTV2 (expanded from prostate). Plans were subsequently applied to daily CT, with beams aligned to the prostate center in the sagittal plane. For five patients having a sufficiently large daily imaging volume, structure contours were manually drawn, and plans were evaluated for all CT sets. For the other five patients, the plans were evaluated for six selected fractions. The daily CT was matched to the simulation CT through deformable registration. The registration accuracy was validated for each fraction, and the three patients with a large number of accurately registered fractions were used for dose accumulation. Results: In individual fractions, the coverage of the prostate, seminal vesicles, and PTV1 was generally maintained at the corresponding prescription dose. For PTV2, the volume covered by the fractional prescription dose of 2 Gy (i.e., V2) was, on average, reduced by less than 3% compared to the simulation plan. Among the 225 (39 x 5 + 6 x 5) fractions examined, 15 showed a V2 reduction larger than 5%, of which ten were caused by a large variation in rectal gas, and five were due to a prostate shift in the craniocaudal direction. The fractional dose to the anterior rectal wall was found to increase for one patient who had large rectal gas volume in 25 of the 39 fractions, and another who experienced significant prostate volume reduction during the treatment. The fractional bladder dose generally increased with decreasing fullness. In the total accumulated dose for the three patients after excluding a few fractions with inaccurate registration due to a large amount of rectal gas (a condition inconsistent with RTOG protocol), 98.5%, 96.6%, and 98.2% of the PTV2 received the prescription dose of 78 Gy. The V75 and V70 of the anterior rectal wall and bladder both remained within tolerance. Conclusions: The results confirm that the PT planning techniques and dose constraints used at our institution ensure that target coverage to the prescription dose is maintained in the presence of interfractional anatomical variations. Dose coverage in individual fractions can be compromised, and normal tissue dose increased, due to deviations in the bladder and rectal volume compared to the simulation plans or progressive changes in the prostate volume during the treatment. Deviations from the plan can be reduced with efforts aimed at maintaining consistent daily patient anatomy.

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2011

A method for patient dose reduction in dynamic contrast enhanced CT study

Purpose: In dynamic contrast enhanced CT (DCE-CT) study, prolonged CT scanning with high temporal resolution is required to give accurate and precise estimates of kinetic parameters. However, such scanning protocol could lead to substantial radiation dose to the patient. A novel method is proposed to reduce radiation dose to patient, while maintaining high accuracy for kinetic parameter estimates in DCE-CT study. Methods: The method is based on a previous investigation that the arterial impulse response (AIR) in DCE-CT study can be predicted using a population-based scheme. In the proposed method, DCE-CT scanning is performed with relatively low temporal resolution, hence, giving rise to reduction in patient dose. A novel method is proposed to estimate the arterial input function (AIF) based on the coarsely sampled AIF. By using the estimated AIF in the tracer kinetic analysis of the coarsely sampled DCE-CT study, the calculated kinetic parameters are able to achieve a high degree of accuracy. The method was tested on a DCE-CT data set of 48 patients with cervical cancer scanned at high temporal resolution. A random cohort of 34 patients was chosen to construct the orthonormal bases of the AIRs via singular value decomposition method. The determined set of orthonormal bases was used to fit the AIFs in the second cohort (14 patients) at varying levels of down sampling. For each dataset in the second cohort, the estimated AIF was used for kinetic analyses of the modified Tofts and adiabatic tissue homogeneity models for each of the down-sampling schemes between intervals from 2 to 15 s. The results were compared with analyses done with the ''raw'' down-sampled AIF. Results: In the first group of 34 patients, there were 11 orthonormal bases identified to describe the AIRs. The AIFs in the second group were estimated in high accuracy based on the 11 orthonormal bases established in the first group along with down-sampled AIFs. Using the 11 orthonormal bases, the estimated AIFs for the second group were found to have an averaged maximal percentage error of 3.4%{+-} 7.5% in all sampling schemes up to 15 s. The results of kinetic analysis with the proposed method compared with down sampling alone showed that the proposed method is superior in maintaining the accuracy in volume transfer constant (K{sup trans} ) after 9 s down-sampling interval, blood volume (v{sub b} ) for almost all down-sampling intervals, and blood flow (F) after 11 s down-sampling interval. The preliminary results suggested that the proposed method is able to support scanning intervals of 10-15 s at a cost of 6.2%-10.0% loss in accuracy of K{sup trans} and 10.9%-19.4% in v{sub b}, and the scanning intervals of 12-15 s at a cost of 9.7%-14.6% for F in DEC-CT studies for patients with cervix cancer. Conclusions: The proposed method of AIF estimation allows low scanning frequency in DCE-CT study to reduce radiation dose to patient, while maintaining relatively high accuracy in the kinetic parameter estimates. The initial results suggested that the method is applicable for DCE-CT studies for patients with cervical cancer.

60 APPLIED LIFE SCIENCES↗