Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ABSTRACT”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Improving perfusion defect detection with respiratory motion correction in cardiac SPECT at standard and reduced doses

Background: In cardiac SPECT perfusion imaging, respiratory motion can cause non-uniform blurring in the reconstructed myocardium. We investigate the potential benefit of respiratory correction with respiratory-binned acquisitions, both at standard dose and at reduced dose, for defect detection and for left ventricular (LV) wall resolution. Methods: We applied two reconstruction methods for respiratory motion correction: post-reconstruction motion correction (PMC) and motion-compensated reconstruction (MCR), and compared with reconstruction without motion correction (Non-MC). We quantified the presence of perfusion defects in reconstructed images by using the total perfusion deficit (TPD) scores and conducted receiver-operating-characteristic (ROC) studies using TPD. We quantified the LV spatial resolution by using the FWHM of its cross-sectional intensity profile. Results: The values in the area-under-the-ROC-curve (AUC) achieved by MCR, PMC, and Non-MC at standard dose were 0.835, 0.830, and 0.798, respectively. Similar AUC improvements were also obtained by MCR and PMC over Non-MC at 50%, 25%, and 12.5% of full dose. Improvements in LV resolution were also observed with motion correction. Conclusions: Respiratory-binned acquisitions can improve perfusion-defect detection accuracy over traditional reconstruction both at standard dose and at reduced dose. Motion correction may contribute to achieving further dose reduction while maintaining the diagnostic accuracy of traditional acquisitions. [French] French Abstract: Contexte: Les mouvements respiratoires peuvent entrainer des artefacts de uniformité lors de la reconstruction des images de perfusion myocardique en SPECT. Dans cet article, nous rapportons nos résultats sur le bénéfice potentiel du « gating » respiratoire avec des doses standards et réduites de radio-pharmaceutiques pour la détection des anomalies de perfusion et les mesures de la paroi ventriculaire gauche. Méthodes: Nous avons appliqué deux méthodes de reconstruction pour la correction du mouvement respiratoire: la première fait appel a une correction après reconstruction des images (PMC) ; la seconde fait appel à la correction des images avant reconstruction (MRC). Les deux approches ont été comparées à la reconstruction sans correction de mouvement (Non-MC). Nous avons quantifié les déficits de perfusion myocardiques sur les images reconstruites avec le système des scores de déficit de perfusion et analysé les résultats en utilisant les courbes ROC. Nous avons quantifié la résolution spatiale du VG en utilisant le FWHM du profil d’intensité de sa section transversale. Résultats: Les valeurs des surfaces en dessous des courbes ROC (AUC) obtenues par MCR, PMC et Non-MC avec doses standard de radio-pharmaceutiques étaient de 0,835, 0,830 et 0,798, respectivement. Des améliorations similaires de l’AUC ont également été obtenues par MCR et PMC sur Non-MC avec 50%, 25% et 12,5% des doses entières. Les mesures de résolution spatiale de la paroi du VG ont également été améliorées avec la correction des mouvements respiratoires. Conclusions: La correction des images de perfusion myocardiques en SPECT par « gating » respiratoire paraît améliorer la quantification des déficits perfusionels à la fois à dose standard et à dose réduite de radio-pharmaceutiques. L’application de cette correction devrait permettre de réduire les doses de radio-pharmaceutiques utilisées tout en maintenant la précision diagnostique des acquisitions traditionnelles. [Spanish] Spanish Abstract: Antecedentes: En los estudios de perfusión cardiaca por SPECT, los movimientos respiratorios pueden causar distorsión no uniforme en el miocardio reconstruido. Investigamos el beneficio potencial de la corrección respiratoria con adquisición de imágenes sincronizadas con la respiración, tanto a dosis estándar como a dosis reducida, para detección de defectos y para resolución de pared de ventrículo izquierdo (VI). Métodos: Aplicamos dos métodos de reconstrucción para corrección de movimientos respiratorios: Corrección de movimiento post reconstrucción (PMC) y reconstrucción compensada a movimiento (MCR), y los comparamos con la reconstrucción sin corrección de movimiento (Non-MC). Cuantificamos la presencia de defectos de perfusión en las imágenes reconstruidas usando los scores de déficit total de perfusión (TPD) y análisis ROC usando el TPD. Cuantificamos la resolución espacial del VI usando la anchura a media altura de su perfil de intensidad transversal. Resultados: Los valores en el área bajo la curva ROC (ABC) obtenidos por MCR, PMC y Non-MC a dosis estándar fueron 0.835, 0.830 y 0.798, respectivamente. Mejorías similares del ABC también se obtuvieron por MCR y PMC, sobre Non-MC a 50%, 25% y 12.5% de la dosis completa. Las mejorías en la resolución del VI fueron observadas también con corrección del movimiento. Conclusiones: Las adquisiciones sincronizadas con la respiración pueden mejorar la precisión de la detección de defectos de perfusión sobre las reconstrucciones tradicionales tanto a dosis estándar como a dosis reducida. La corrección de movimiento puede contribuir a lograr mayor reducción de la dosis manteniendo la precisión diagnóstica de las adquisiciones tradicionales. [Chinese] Chinese Abstract: 背景: 在心脏 SPECT 灌注成像中, 呼吸运动会导致心肌重建的不均匀模糊。我们研究了无论是标准剂量还是减少剂量的情况下, 呼吸跟踪采集的呼吸校正用于图像缺损检测和左心室 (LV) 室壁分辨率的潜在益处。 方法: 我们使用了两种呼吸运动校正的重建方法:重建后运动校正 (PMC) 和运动补偿重建 (MCR), 并与没有运动校正的重建 (Non-MC) 进行比较。 通过总灌注缺损 (TPD) 评分和其接受者操作特性曲线 (ROC) 来量化重建图像中的灌注缺陷。通过LV横截面强度分布的 FWHM来量化 LV 空间分辨率。 结果: MCR, PMC 和 Non-MC 在标准剂量下所获得的 ROC 曲线下面积 (AUC) 的值分别为0.835, 0.830 和 0.798。 在全剂量下, MCR, PMC和 Non-MC也获得类似的 AUC 提高, 分别为 50%, 25% 和 12.5%。 在运动校正下, LV的分辨率也得到了改善。 结论: 在标准剂量和减少剂量的情况下, 呼吸跟踪采集可以改善灌注缺损检测的准确性。 运动校正可能有助于进一步实现减少剂量的目标, 同时保证通过传统检测方法的诊断准确性。.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

The utility of {sup 82}Rb PET for myocardial viability assessment: Comparison with perfusion-metabolism {sup 82}Rb-{sup 18}F-FDG PET

Background: {sup 82}Rb kinetics may distinguish scar from viable but dysfunctional (hibernating) myocardium. We sought to define the relationship between {sup 82}Rb kinetics and myocardial viability compared with conventional {sup 82}Rb and {sup 18}F-fluorodeoxyglucose (FDG) perfusion-metabolism PET imaging. Methods: Consecutive patients (N = 120) referred for evaluation of myocardial viability prior to revascularization and normal volunteers (N = 37) were reviewed. Dynamic {sup 82}Rb 3D PET data were acquired at rest. {sup 18}F-FDG 3D PET data were acquired after metabolic preparation using a standardized hyperinsulinemic-euglycemic clamp. {sup 82}Rb kinetic parameters K{sub 1}, k{sub 2}, and partition coefficient (KP) were estimated by compartmental modeling Results: Segmental {sup 82}Rb k{sub 2} and KP differed significantly between scarred and hibernating segments identified by Rb-FDG perfusion-metabolism (k{sub 2}, 0.42 ± 0.25 vs. 0.22 ± 0.09 min{sup −1}; P < .0001; KP, 1.33 ± 0.62 vs. 2.25 ± 0.98 ml/g; P < .0001). As compared to Rb-FDG analysis, segmental Rb KP had a c-index, sensitivity and specificity of 0.809, 76% and 84%, respectively, for distinguishing hibernating and scarred segments. Segmental k{sub 2} performed similarly, but with lower specificity (75%, P < .001) Conclusions: In this pilot study, {sup 82}Rb kinetic parameters k{sub 2} and KP, which are readily estimated using a compartmental model commonly used for myocardial blood flow, reliably differentiated hibernating myocardium and scar. Further study is necessary to evaluate their clinical utility for predicting benefit after revascularization. [French] French Abstract: Contexte: La cinétique du {sup 82}Rb pourrait être utilisée pour distinguer la fibrose myocardique des zones viables mais dysfonctionnelles (en hibernation). Dans cette étude, nous avons cherché à définir la relation entre la cinétique du {sup 82}Rb et la viabilité myocardique en comparant les images de perfusion et métabolisme myocardique utilisant le {sup 82}Rb et le {sup 18}F-fluorodésoxyglucose (FDG) Méthodes: les données obtenues chez 120 patients consécutifs (N = 120) référés pour évaluation de la viabilité du myocarde avant revascularisation et 37 volontaires considérés normaux (N = 37) ont été étudieés. Les données TEP 3D dynamiques {sup 82}Rb ont été acquises au repos. Les données TEP 3D au {sup 18}F-FDG ont été acquises après préparation métabolique utilisant une pince hyperinsulémique-euglycémique normalisée. Les paramètres k1, k2 et le coefficient de partage (KP) de la cinétique du {sup 82}R bont été évalues par modélisation compartimentale. Résultats: les paramètres k2 et KP de distribution du {sup 82}Rb se sont révélés significativement différent entre les zones tissulaires cicatricielles fibreuses et celles en hibernation identifiées par étude métabolique au FDG (k2, 0,42 ± 0,25 vs. 0,22 ± 0,09 min{sup −1}; P < 0,0001; KP, 1,33 ± 0,62 vs. 2,25 ± 0,98 ml/g; P < 0,0001). Par rapport aux données FDG, le paramètre KP du rubidium a révélé un indice de concordance de 0,809 et une sensibilité et spécificité de 76% et 84%, pour la distinction des segments en hibernation et cicatrisés. Les résultats du paramètre k2 se sont révélés similaires, mais avec une spécificité plus faible calculée à 75% (P < 0,001). Conclusions: Dans cette étude pilote, les paramètres cinétiques k2 et KP de perfusion myocardique au {sup 82}Rb, qui sont facilement estimés à l’aide d’un modèle compartimental couramment utilisé pour flux sanguin myocardique, ont permis de différencier de manière fiable le myocarde cicatricielle des zones myocardiques hibernantes. Une étude plus approfondie est souhaitable pour valider leur utilité clinique en revacularisation. [Spanish] Spanish Abstract: Antecedentes: La cinética con {sup 82}Rb puede distinguir las cicatrices miocárdicas del tejido viable pero disfuncional (hibernante). Buscamos definir la relación entre la cinética del {sup 82}Rb y la viabilidad miocárdica comparada con las imágenes convencionales de PET con {sup 82}Rb y {sup 18}F-flurodeoxyglucosa (FDG). Métodos: se evaluaron a Pacientes Consecutivos (N = 120) referidos para evaluación de viabilidad miocárdica previos a revascularización y voluntarios normales (N = 37). Los datos de PET 3D dinámico con {sup 82}Rb fueron adquiridos en reposo. Los datos de {sup 18}F-FDG 3D PET fueron adquiridos posterior a la preparación metabólica usando un clamp hiperinsulínico-euglucémico. Los patrones cinéticos K1, k2 y el coeficiente de partición (KP) fueron estimados por el modelo compartimental. Resultados: el k2 y KP del {sup 82}Rb permitueron distinguier el tejido cicatricial de los segmentos hibernados identificados por la vía perfusión metabolismo de Rb-FDG (k{sub 2}, 0.42 ± 0.25 vs. 0.22 ± 0.09 min-1; P < .0001; KP, 1.33 ± 0.62 vs. 2.25 ± 0.98 ml/g; P < .0001). En comparación con el análisis de Rb-FDG, el KP segmentario del Rb tuvo un índice-c, sensbilidad y especificidad de 0.809 76 y 84%, respectivamente, para distinguir segmentos hibernantes y cicatriciales. k2 Segmentario tuvo un desempeño similar pero con una menor especificidad (75%, P < .001). Conclusiones: En este estudio piloto, los parámetros cinéticos k2 y KP del {sup 82}Rb, los cuales son estimados usando un modelo compartimental usado comúnmente para flujo sanguíneo miocárdico, diferenciaron el miocardio hibernante del cicatricial. Se necesita estudiar más a fondo para evaluar la utilidad clínica para la predicción del beneficio posterior a la revascularización [Chinese] Chinese Abstract: 背景: 铷-82({sup 82}Rb)药代动力学可能区分梗死与功能受损但存活的心肌(冬眠心肌)。我们将探讨{sup 82}Rb药代动力学与存活心肌的关系,并与常规的{sup 82}Rb和{sup 18}F-氟脱氧葡萄糖(FDG)灌注-代谢PET显像进行比较。 方法: 连续纳入120名血运重建前评估存活心肌的患者和37名正常志愿者。获得静息{sup 82}Rb 3D-PET动态采集数据;采用标准化的高胰岛素 - 正葡萄糖钳夹试验得到{sup 18}F-FDG 3D PET代谢显像数据; 通过房室模型计算{sup 82}Rb动力学参数k{sub 1},k{sub 2}和分配系数(KP)。 结果: 以Rb-FDG灌注代谢显像鉴定疤痕心肌组和冬眠心肌组,两组的{sup 82}Rb节段性 k{sub 2}值和KP值有明显差异(k{sub 2}, 0.42 ± 0.25 vs 0.22 ± 0.09 min{sup −1}; P < .0001; KP, 1.33 ± 0.62 vs 2.25 ± 0.98 ml/g; P < .0001)。以Rb-FDG灌注代谢显像为诊断标准,{sup 82}Rb节段性 KP对疤痕和冬眠心肌鉴别效能的c指数,敏感性和特异性分别是0.809, 76%和84%。节段性k{sub 2}的鉴别效能与KP相似,但特异性较低(75%,P < .001)。 结论: 在本试验性研究中,通过常规用于{sup 82}Rb心肌血流量测定的房室模型计算出的{sup 82}Rb动力学参数k{sub 2}和KP,可以有效的区分冬眠心肌和瘢痕心肌。 但需要进一步的研究来评估其对预测血运重建是否获益的临床价值。.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Left ventricular ejection fraction determined with the simulation of a very low-dose CZT-SPECT protocol and an additional count-calibration on planar radionuclide angiographic data

Purpose: To determine whether the left ventricular ejection fractions (EFs), measured on a high-sensitivity CZT single photon emission computed tomography (SPECT)-camera with a 70% reduction in recording times and a prevention of EF overestimation through an additional count-calibration, are concordant with reference EF from planar radionuclide angiography (2D-RNA). Methods: An additional 10-minute CZT-SPECT recording was performed in patients referred to 2D-RNA for cardiomyopathy (n = 23) or chemotherapy monitoring (n = 50) with an in vivo red blood cell labeling with 850 MBq {sup 99m}TcO{sub 4}{sup −}. The EF, obtained from CZT-SPECT with 100% (SPECT100) or 30% (SPECT30) projection times and with a SPECT-count calibration on the 2D-RNA counts of corresponding cavity volumes, were compared to EF from 2D-RNA. Results: Strong and equivalent relationships were documented between the EF from 2D-RNA and the calibrated EF from SPECT100 (y = 0.89x + 6.62; R{sup 2} = 0.87) and SPECT30 (y = 0.87x + 8.40; R{sup 2} = 0.85), and the mean EF from SPECT100 (54% ± 15%) and SPECT30 (53% ± 16%) were close to that from 2D-RNA (55% ± 15%). However, upward shifts in these mean values were documented in the absence of count calibration for both SPECT100 (60% ± 18%) and SPECT30 (60% ± 18%). Conclusion: Left ventricular EF may be determined on a high-sensitivity CZT-camera, a 70% reduction in injected activities, and an additional count-calibration for further enhancing the concordance with 2D-RNA values. [French] French Abstract: Objectif: Déterminer si les fractions d'éjection ventriculaire gauche (EF) mesurées sur une caméra CZT SPECT à haute sensibilité avec une réduction de 70% des temps d'enregistrement et une prévention de la surestimation de l'EF grâce à un étalonnage supplémentaire des coups concordent avec les EF de référence obtenues par angiographie scintigraphique planaire (2D-RNA). Méthodes: Un enregistrement CZT-SPECT supplémentaire de 10 minutes a été réalisé chez les patients référés pour évaluation de cardiomyopathie (n=23) ou suivi de chimiothérapie (n = 50) par angiographie scintigraphique planaire (2D-RNA) au globules rouges marqués avec 850 MBq 99mTcO4-. Les EF, obtenues au moyen d’une caméra CZT-SPECT avec 100% (SPECT100) ou 30% (SPECT30) de temps d’acquisition et avec étalonnage des coups SPECT sur les images 2D-RNA des volumes de cavité correspondants ont été comparés aux EF à partir de 2D-RNA. Résultats: une corrélation significative existe entre les EF obtenues par 2D-RNA et les EF étalonnées obtenues par SPECT100 (y = 0,89x + 6,62; R2 = 0,87) et SPECT30 (y = 0,87x + 8,40; R2 = 0,85). Les EF moyennes de SPECT100 (54 ± 15%) et SPECT30 (53 ± 16%) sont similaires à celles obtenues par 2D-RNA (55 ± 15%). En l'absence d'étalonnage de comptage des études SPECT100 (60 ± 18%) et SPECT30 (60 ± 18%), ces valeurs moyennes d’EF sont généralement plus élevées. Conclusion: La fonction ventriculaire gauche peut être déterminée avec une caméra CZT à haute sensibilité, une réduction des activités injectées et un étalonnage supplémentaire des coups pour améliorer la concordance avec les valeurs obtenues par 2D-RNA. [Spanish] Spanish Abstract: Propósito: Determinar si la fracción de eyección del ventrículo izquierdo, medida con la cámara CZT-SPECT con una reducción del 70% en tiempo de grabación y con la prevención de la sobreestimación mediante una calibración de cuentas adicional, que sea concordante con el valor referencia de fracción de eyección mediante radiografía planar de radionucleidos. (2D-RNA). Métodos: Una grabación adicional de 10 minutos con CZT-SPECT se realizo en pacientes referidos a radiografía planar de radionucleidos (2D-RNA) por miocardiopatías. (n = 23) o para monitorizar las quimioterapias (n = 50) con marcaje de glóbulos rojos con 850 MBq 99m TcO4. La fracción de eyección obtenida por CZT-SPECT con 100% (SPECT100) o 30% (SPECT30) de tiempo de proyección, y con SPECT con calibración de cuentas con el 2D-RNA, los volúmenes de cavidades fueron comparados con fracción de eyección . Relaciones fuertes y equivalentes fueron documentados entre fracción de eyección del 2D-RNA, y la forma calibrada de la fracción de eyección SPECT100 (y = 0.89x + 6.62; R2 = 0.87) y SPECT30 y = 0.87x + 8.40; R2 = 0.85), y la media de fracción de eyección de SPECT100 (54 ± 15%) and SPECT30 (53 ± 16%) fueron cercanos a la de el 2D-RNA (55 ± 15%). Aunque, aumentos en estas medias se documentaron en la ausencia de la calibración de cuentas para SPECT100 (60 ± 18%) y SPECT30 (60 ± 18%). Conclusión: La fracción de eyección del ventrículo izquierdo puede ser determinada con una cámara CZT de alta sensibilidad, una reducción del 70% en actividades inyectadas y la calibración de cuentas adicional para realzar la concordancia con los valores de 2D-RNA. [Chinese] Chinese Abstract: 目的: 以平面放射性核素血管造影 (2D-RNA) 测定左心室射血分数 (EF) 作为参考标准,为确定利用高灵敏度 CZT SPECT 相机在减少 70% 的记录时间, 并结合计数校准防止高估情况下测量的 EF值, 是否与 2D-RNA 测得的 EF 值一致。 方法: 对心肌病 (n = 23) 或化疗监测 (n = 50) 的患者采用体内标记法注射 850 MBq {sup 99m}TcO{sub 4} 标记的红细胞进行 2D-RNA ,随后再采集 10 分钟 CZT-SPECT。 对 CZT-SPECT 100% 投影时间 (SPECT100) 或 30% 投影时间 (SPECT30) 获得的图像进行重建, 并进行计数校准 (对相应容积获得的 2D-RNA 计数通过 SPECT 校准)获得 EF 值, 与 2D-RNA 测定的 EF 的进行比较。 结果: 2D-RNA 测定的 EF 值与 SPECT100 校准后测定的 EF 值 (y = 0.89x + 6.62; R{sup 2} = 0.87) 及 SPECT30 (y = 0.87x + 8.40; R{sup 2} = 0.85) 校准后 EF 值具有高度相关性, 并且 SPECT100 (54 ± 15%) 和 SPECT30 (53 ± 16%) 测定的 EF 平均值与 2D-RNA 测定的 EF 平均值 (55 ± 15%) 非常接近。 但是, 在没有计数校准的情况下, SPECT100 (60 ± 18%) 和 SPECT30 (60 ± 18%) 测定的 EF 平均值会被高估。 结论: 高灵敏度 CZT 相机可在减少 70% 的注射剂量情况下测定左心室 EF 值, 结合计数校准可进一步提高与 2D-RNA测得的 EF 值的一致性。 关键词: 放射性核素血管造影; 血池 SPECT; CZT 相机; 左心室射血分数; 校准曲线。.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Impact of regadenoson-induced myocardial creep on dynamic Rubidium-82 PET myocardial blood flow quantification

Background: Repositioning of the heart during myocardial perfusion imaging (MPI) using Rubidium-82 (Rb-82) PET may occur when using regadenoson. Our aim was to determine the prevalence and the effect of correcting for this myocardial creep on myocardial blood flow (MBF) quantification. Methods: We retrospectively included 119 consecutive patients who underwent dynamic rest- and regadenoson-induced stress MPI using Rb-82 PET. The presence of myocardial creep was visually assessed in the dynamic stress PET series by identifying differences between the automatically drawn myocardium contour and the activity. Uncorrected and corrected stress MBFs were compared for the three vascular territories (LAD, LCX, and RCA) and for the whole myocardium. Results: Myocardial creep was observed in 52% of the patients during stress. Mean MBF values decreased after correction in the RCA from 4.0 to 2.7 mL/min/g (P < 0.001), in the whole myocardium from 2.7 to 2.6 mL/min/g (P = 0.01), and increased in the LAD from 2.5 to 2.6 mL/min/g (P = 0.03) and remained comparable in the LCX (P = 0.3). Conclusions: Myocardial creep is a frequent phenomenon when performing regadenoson-induced stress Rb-82 PET and has a significant impact on MBF values, especially in the RCA territory. As this may hamper diagnostic accuracy, myocardial creep correction seems necessary for reliable quantification. [French] French Abstract: Contexte: Un repositionnement du cœur lors de l’imagerie de perfusion myocardique (MPI) à l’aide de la TEP au rubidium-82 (RB-82) peut survenir lors de l’utilisation du regadenoson. Notre objectif était de déterminer la prévalence et l’effet de la correction du fluage sur la quantification du débit sanguin myocardique (DSM). Méthodes: dans cette étude rétrospective, nous avons inclus 119 patients consécutifs ayant beneficié d’un examen au repos suivi d’un stress pharamacologique au régadénoson en utilisant le RB-82. La présence de fluage myocardique a été évaluée visuellement sur les images TEP de stress dynamique en utilisant les différences entre les contours automatiques et les images myocardiques. Les DSM de stress non corrigés et corrigés ont été comparés pour les trois territoires vasculaires (coronaire gauche-CG, la circonflexe-CX, et coronaire droite-CD) et pour l’ensemble du myocarde. Résultats: le fluage myocardique a été observé chez 52% des patients sur les examens de stress. Les valeurs moyennes de DSM ont diminué après correction dans le territoire de la CD de 4,0 à 2,7 mL/min/g (p < 0,001), dans le myocarde entier de 2,7 à 2,6 mL/min/g (p = 0,01) et augmenté dans le territoire de la CG de 2,5 à 2,6 mL/min/g (p = 0,03) et est resté comparable dans le territoire de la CX (p = 0,3). Conclusions: le fluage myocardique est un phénomène fréquent lors de l’exécution du stress phramacologique au régadénoson à l’aide du RB-82. Il a un impact significatif sur les valeurs de DSM, en particulier dans le territoire de la CD. La correction du fluage myocardique semble donc nécessaire pour une quantification fiable des flux coronariens. [Spanish] Spanish Abstract: Antecedentes: El movimiento del corazón durante la imagen de perfusión miocárdica usando Rubidio-82 (Rb-82) PET puede ocurrir cuando se usa regadenosón. Nuestro enfoque fue determinar la prevalencia y efecto de la corrección de este Artefacto de movimiento en la cuantificación del flujo sanguíneo miocárdico. Métodos: Se incluyeron de forma retrospectiva 119 pacientes que se realizaron estudio dinámico en reposo y estudio de perfusión miocárdica en estrés inducido por regadenosón usando Rb-82 PET. La presencia de el artefacto de movimiento fue evaluado visualmente en el estudio en serie de PET dinámico en estrés identificando las diferencias entre el contorno miocárdico dibujado automáticamente y la actividad. La perfusión miocárdica en estrés corregida y sin corregir se compararon para los tres territorios vasculares (Descendente Anterior, Circunfleja, Coronaria Derecha) y para todo el miocardio. Resultados: El artefacto de movimiento miocárdico se observo en un 52% de los pacientes durante el estrés. El promedio de los valores de flujo sanguíneo miocárdico disminuyen después de la corrección en la arteria coronaria derecha de 4.0 a 2.7 ml/min/g (p < 0.001), en todo el miocardio de 2.7 a 2.6 mL/min/g (p = 0.01) y un aumento en la arteria descendente anterior de 2.5 a 2.6 mL/min/g (p = 0.03) y se mantuvo comparable en la arteria circunfleja (p = 0.3). Conclusiones: El artefacto de movimiento miocárdico es un fenómeno frecuente cuando se realiza la prueba de estrés inducido con regadenosón Rb-82 PET y tiene un impacto significativo en los valores de flujo sanguíneo miocárdico, principalmente en el territorio de la coronaria derecha. Esto puede disminuir la precisión diagnostica, la corección del artefacto de movimiento es necesario para una cuantificación confiable. [Chinese] Chinese Abstract: 背景: 铷-82 (Rb-82) PET心肌灌注成像 (MPI) 过程在使用类伽腺苷时可能会发生心脏重定位。我们的目的是确定心肌蠕动 (myocardial creep) 校正对心肌血流灌注定量的影响及其普遍性。 方法: 我们连续回顾了119 名使用 Rb-82 PET 进行动态的静息与类伽腺苷负荷MPI的患者。通过识别自动绘制的心肌轮廓和心肌活动之间的差异, 在动态负荷 PET 检查中肉眼评估心肌蠕动的存在。分别在已校正和未校正的负荷 MBF上, 对三个血管区域 (LAD, LCX, RCA) 和整个心肌灌注情况进行比较。 结果: 负荷检查中, 52% 的患者观察到心肌蠕动。 RCA 校正后平均MBF值从4.0降至 2.7 mL / min / g (p <0.001), 整个心肌从 2.7降至 2.6 mL / min / g (p = 0.01) , LAD 从 2.5 升至 2.6mL / min / g (p = 0.03) 并且在LCX中保持不变 (p = 0.3) 。 结论: 类伽腺苷负荷 Rb-82 PET 检查中, 心肌蠕动是一种常见的现象, 并且对 MBF 值有显著影响, 特别在 RCA 区域。这可能妨碍诊断准确性, 因此心肌蠕动校正是准确定量的必要条件。.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

pyomo.dae: a modeling and automatic discretization framework for optimization with differential and algebraic equations

We describe pyomo.dae, an open source Python-based modeling framework that enables high-level abstract specification of optimization problems with differential and algebraic equations. The pyomo.dae framework is integrated with the Pyomo open source algebraic modeling language, and is available at http://www.pyomo.org. One key feature of pyomo.dae is that it does not restrict users to standard, predefined forms of differential equations, providing a high degree of modeling flexibility and the ability to express constraints that cannot be easily specified in other modeling frameworks. Other key features of pyomo.dae are the ability to specify optimization problems with high-order differential equations and partial differential equations, defined on restricted domain types, and the ability to automatically transform high-level abstract models into finite-dimensional algebraic problems that can be solved with off-the-shelf solvers. Moreover, pyomo.dae users can leverage existing capabilities of Pyomo to embed differential equation models within stochastic and integer programming models and mathematical programs with equilibrium constraint formulations. Collectively, these features enable the exploration of new modeling concepts, discretization schemes, and the benchmarking of state-of-the-art optimization solvers.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2026

Graph-Based Modeling and Decomposition of Hierarchical Optimization Problems

We present a graph-theoretic modeling approach for hierarchical optimization that leverages the OptiGraph abstraction implemented in the Julia package Plasmo.jl. We show that the abstraction is flexible and can effectively capture complex hierarchical connectivity that arises from decision-making over multiple spatial and temporal scales (e.g., integration of planning, scheduling, and operations in manufacturing and infrastructures). We also show that the graph abstraction facilitates the conceptualization and implementation of decomposition and approximation schemes. Specifically, we propose a graph-based Benders decomposition (gBD) framework that enables the exploitation of hierarchical (nested) structures and that uses graph aggregation/partitioning procedures to discover such structures. In addition, we provide a Julia implementation of gBD, which we call PlasmoBenders.jl. We illustrate the capabilities using examples arising in the context of energy and power systems.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2014

Crystal structure of glycoside hydrolase family 127 β-L-arabinofuranosidase from Bifidobacterium longum

Graphical abstract: - Highlights: • HypBA1 β-L-arabinofuranosidase belongs to glycoside hydrolase family 127. • Crystal structure of HypBA1 was determined. • HypBA1 consists of a catalytic barrel and two additional β-sandwich domains. • The active site contains a Zn{sup 2+} coordinated by glutamate and three cysteines. • A possible reaction mechanism involving cysteine as the nucleophile is proposed. - Abstract: Enzymes acting on β-linked arabinofuranosides have been unknown until recently, in spite of wide distribution of β-L-arabinofuranosyl oligosaccharides in plant cells. Recently, a β-L-arabinofuranosidase from the glycoside hydrolase family 127 (HypBA1) was discovered in the newly characterized degradation system of hydroxyproline-linked β-L-arabinooligosaccharides in the bacterium Bifidobacterium longum. Here, we report the crystal structure of HypBA1 in the ligand-free and β-L-arabinofuranose complex forms. The structure of HypBA1 consists of a catalytic barrel domain and two additional β-sandwich domains, with one β-sandwich domain involved in the formation of a dimer. Interestingly, there is an unprecedented metal-binding motif with Zn{sup 2+} coordinated by glutamate and three cysteines in the active site. The glutamate residue is located far from the anomeric carbon of the β-L-arabinofuranose ligand, but one cysteine residue is appropriately located for nucleophilic attack for glycosidic bond cleavage. The residues around the active site are highly conserved among GH127 members. Based on biochemical experiments and quantum mechanical calculations, a possible reaction mechanism involving cysteine as the nucleophile is proposed.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Structural and biochemical studies on the role of active site Thr166 and Asp236 in the catalytic function of D-Serine deaminase from Salmonella typhimurium

Highlights: • The crystal structure of T166A determined at 2.7 Å resolution represents the first PLP bound form of the StDSD enzyme. • Mutation of Thr166 to Ala and Asp236 to Leu results in the inactivation of the enzyme. • Thr166 might abstract Cα proton of D-Ser to carry out catalysis and Asp236 might stabilize the internal aldimine form. • Conformational changes are important for bringing Thr166 to a position favorable for proton abstraction. D-Serine deaminase (DSD) degrades D-Ser to pyruvate and ammonia. Uropathogenic bacteria survive in the toxic D-Ser containing mammalian urine because of DSD activity. The crystal structure of the apo form of Salmonella typhimurium DSD (StDSD) has been reported earlier. In the present work, we have investigated the role of two active site residues, Thr166 and Asp236 by site directed mutagenesis (T166A and D236L). The enzyme activity is lost upon mutation of these residues. The 2.7 Å resolution crystal structure of T166A DSD with bound PLP reported here represents the first structure of the holo form of StDSD. PLP binding induces small changes in the relative dispositions of the minor and major domains of the protein and this inter-domain movement becomes substantial upon interaction with the substrate. The conformational changes bring Thr166 to a position at the active site favorable for the degradation of D-Ser. Examination of the different forms of the enzyme and comparison with structures of homologous enzymes suggests that Thr166 is the most probable base abstracting proton from the Cα atom of the substrate and Asp236 is crucial for binding of the cofactor.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Machine-learning error models for approximate solutions to parameterized systems of nonlinear equations

Here, this work proposes a machine-learning framework for constructing statistical models of errors incurred by approximate solutions to parameterized systems of nonlinear equations. These approximate solutions may arise from early termination of an iterative method, a lower-fidelity model, or a projection-based reduced-order model, for example. The proposed statistical model comprises the sum of a deterministic regression-function model and a stochastic noise model. The method constructs the regression-function model by applying regression techniques from machine learning (e.g., support vector regression, artificial neural networks) to map features (i.e., error indicators such as sampled elements of the residual) to a prediction of the approximate-solution error. The method constructs the noise model as a mean-zero Gaussian random variable whose variance is computed as the sample variance of the approximate-solution error on a test set; this variance can be interpreted as the epistemic uncertainty introduced by the approximate solution. This work considers a wide range of feature-engineering methods, data-set-construction techniques, and regression techniques that aim to ensure that (1) the features are cheaply computable, (2) the noise model exhibits low variance (i.e., low epistemic uncertainty introduced), and (3) the regression model generalizes to independent test data. Finally, numerical experiments performed on several computational-mechanics problems and types of approximate solutions demonstrate the ability of the method to generate statistical models of the error that satisfy these criteria and significantly outperform more commonly adopted approaches for error modeling.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

A framework for modeling and optimizing dynamic systems under uncertainty

Algebraic modeling languages (AMLs) have drastically simplified the implementation of algebraic optimization problems. However, there are still many classes of optimization problems that are not easily represented in most AMLs. These classes of problems are typically reformulated before implementation, which requires significant effort and time from the modeler and obscures the original problem structure or context. In this work we demonstrate how the Pyomo AML can be used to represent complex optimization problems using high-level modeling constructs. We focus on the operation of dynamic systems under uncertainty and demonstrate the combination of Pyomo extensions for dynamic optimization and stochastic programming. We use a dynamic semibatch reactor model and a large-scale bubbling fluidized bed adsorber model as test cases.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

ADAM: A web platform for graph-based modeling and optimization of supply chains

Modeling and optimization are essential tasks that arise in the analysis and design of supply chains (SCs). SC models are essential for understanding emergent behavior such as transactions between participants, inherent value of products exchanged, as well as impact of externalities (e.g., policy and climate) and of constraints. Unfortunately, most users of SC models have limited expertise in mathematical optimization, and this hinders the adoption of advanced decision-making tools. Here, in this work, we present ADAM, a web platform that enables the modeling and optimization of SCs. ADAM facilitates modeling by leveraging intuitive and compact graph-based abstractions that allow the user to express dependencies between locations, products, and participants. ADAM model objects serve as repositories of experimental, technology, and socio-economic data; moreover, the graph abstractions facilitate the organization and exchange of models and provides a natural framework for education and outreach. Here, we discuss the graph abstractions and software design principles behind ADAM, its key functional features and workflows, and application examples.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

PlasmoData.jl — A Julia framework for modeling and analyzing complex data as graphs

Datasets encountered in scientific and engineering applications appear in complex formats (e.g., images, multivariate time series, molecules, video, text strings, networks). Graph theory provides a unifying framework to model such datasets and enables the use of powerful tools that can help analyze, visualize, and extract value from data. In this work, we present PlasmoData.jl, an open-source, Julia framework that uses concepts of graph theory to facilitate the modeling and analysis of complex datasets. The core of our framework is a general data modeling abstraction, which we call a DataGraph. We show how the abstraction and software implementation can be used to represent diverse data objects as graphs and to enable the use of tools from topology, graph theory, and machine learning (e.g., graph neural networks) to conduct a variety of tasks. We illustrate the versatility of the framework by using real datasets: (i) an image classification problem using topological data analysis to extract features from the graph model to train machine learning models; (ii) a disease outbreak problem where we model multivariate time series as graphs to detect abnormal events; and (iii) a technology pathway analysis problem where we highlight how we can use graphs to navigate connectivity. Further, our discussion also highlights how PlasmoData.jl leverages native Julia capabilities to enable compact syntax, scalable computations, and interfaces with diverse packages. Overall, we show that the DataGraph abstraction and PlasmoData.jl Julia package are able to model data within graphs and enable useful analysis.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗
DOE OSTI2015

Metallic phase change material thermal storage for Dish Stirling

Dish-Stirling systems provide high-efficiency solar-only electrical generation and currently hold the world record at 31.25%. This high efficiency results in a system with a high possibility of meeting the DOE SunShot goal of $0.06/kWh. However, current dish-Stirling systems do not incorporate thermal storage. For the next generation of non-intermittent and cost-competitive solar power plants, we propose adding a thermal energy storage system that combines latent (phase-change) energy transport and latent energy storage in order to match the isothermal input requirements of Stirling engines while also maximizing the exergetic efficiency of the entire system. This paper reports current findings in the area of selection, synthesis and evaluation of a suitable high performance metallic phase change material (PCM) as well as potential interactions with containment alloy materials. The metallic PCM's, while more expensive than salts, have been identified as having substantial performance advantages primarily due to high thermal conductivity, leading to high exergetic efficiency. Systems modeling has indicated, based on high dish Stirling system performance, an allowable cost of the PCM storage system that is substantially higher than SunShot goals for storage cost on tower systems. Several PCM's are identified with suitable melting temperature, cost, and performance.

14 SOLAR ENERGY↗
DOE OSTI2025

Corrigendum to ‘Under-capacitated and over-powered? Rural austerity and asymmetrical negotiating relationships in US wind energy development’ [J. Rural Stud., 119 (2025) 1–14]

The authors regret that there is an incomplete sentence in the abstract of the article, and request that the portion “, and counties incre” be deleted from the abstract (found at the end of the sentence beginning with “However …”). The portion to be deleted is underlined and bolded below. The authors would like to apologise for any inconvenience caused. Current abstract: Though rural local governments are central actors in renewable energy development, local governments in the United States (US) remain systematically under-funded. This paper considers what the manifestations of austerity in local governments broadly and rural localities specifically mean for renewable energy development and for energy transitions. Drawing on a survey of 262 elected county officials with experience with wind energy in eight US states, this paper asks how local officials understand the impacts of wind development, how local governments are involved in wind energy negotiations, how the resources and expertise needed to navigate negotiations are distributed among counties, and analyze the relationship between local capacity, access to resources, and involvement in negotiations. We find that local officials express simultaneously affective and material concerns with the impacts of wind development and see negotiations with the developer as central to realizing local benefits. However, the expertise and staffing needed to negotiate with developers is less accessible to poorer or sparsely populated counties, and counties with lower overall revenues have narrower scopes of negotiation, and counties incre. Our results suggest that uneven rural capacity heightens an already asymmetrical relationship between localities and developers. In analyzing how infrastructure developments are shaped by relationships between localities and developers that are conditioned by austerity and (under)capacity, this paper contributes to and bridges scholarly discussions on rural austerity, rescaling, and renewable energy transitions. These results challenge conventional wisdoms around centralizing energy siting processes, contextualize popular and academic debates about opposition to renewable energy development, and highlight the need for rural reinvestment to realize meaningfully participatory energy developments.

Elmallah, Salma↗
DOE OSTI2012

Introduction of oxygen vacancies and fluorine into TiO{sub 2} nanoparticles by co-milling with PTFE

Solid-state processes of introducing oxygen vacancies and transference of fluorine to n-TiO{sub 2} nanoparticles by co-milling with poly(tetrafluoroethylene) (PTFE) powder were examined by diffuse reflectance spectroscopy (DRS) of UV, visual, near- and mid-IR regions, thermal analyses (TG-DTA), energy-dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The broad absorption peak at around 8800 cm{sup -1} (1140 nm) was attributed to the change in the electronic states, viz. electrons trapped at the oxygen vacancies (Vo) and d-d transitions of titanium ions. Incorporation of fluorine into n-TiO{sub 2} was concentrated at the near surface region and amounted to ca. 40 at% of the total fluorine in PTFE, after co-milling for 3 h, as confirmed by the F1s XPS spectrum. The overall atomic ratio, F/Ti, determined by EDXS was 0.294. By combining these analytical results, a mechanism of the present solid state processes at the boundary between PTFE and n-TiO{sub 2} was proposed. The entire process is triggered by the partial oxidative decomposition of PTFE. This is accompanied by the abstraction of oxygen atoms from the n-TiO{sub 2} lattices. Loss of the oxygen atoms results in the formation of the diverse states of locally distorted coordination units of titania, i.e. TiO{sub 6-n}Vo{sub n}, located at the near surface region. This leads subsequent partial ligand exchange between F and O, to incorporate fluorine preferentially to the near surface region of n-TiO{sub 2} particles, where local non-crystalline states predominate. - Graphical abstract: Scheme of the reaction processes: (a) pristine mixture, (b) oxygen abstraction from TiO{sub 2} and (c) fluorine migration from PTFE to TiO{sub 2}. Highlights: Transfer of fluorine from PTFE to n-TiO{sub 2} in a dry solid state process was confirmed. Black-Right-Pointing-Pointer 40% of F in PTFE was incorporated to the near surface region of n-TiO{sub 2} nanoparticles. Black-Right-Pointing-Pointer The transfer process is triggered by the oxidative decomposition of PTFE. Black-Right-Pointing-Pointer Fluorine incorporation is mediated by the formation of oxygen vacancies. Black-Right-Pointing-Pointer The sequential mechanisms are verified by XPS, EDXS, HRTEM, TG and DRS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗