Publications by authors named "Hongyu An"

113 Publications

Deteriorated regional calf microcirculation measured by contrast-free MRI in patients with diabetes mellitus and relation with physical activity.

Diab Vasc Dis Res 2021 Jul-Aug;18(4):14791641211029002

The Program in Physical Therapy, Washington University School of Medicine, St. Louis, MO, USA.

Objective: To evaluate regional calf muscle microcirculation in people with diabetes mellitus (DM) with and without foot ulcers, compared to healthy control people without DM, using contrast-free magnetic resonance imaging methods.

Methods: Three groups of subjects were recruited: non-DM controls, DM, and DM with foot ulcers (DM + ulcer), all with ankle brachial index (ABI) > 0.9. Skeletal muscle blood flow (SMBF) and oxygen extraction fraction (SMOEF) in calf muscle were measured at rest and during a 5-min isometric ankle plantarflexion exercise. Subjects completed the Yale physical activity survey.

Results: The exercise SMBF (ml/min/100 g) of the medial gastrocnemius muscle were progressively impaired: 63.7 ± 18.9 for controls, 42.9 ± 6.7 for DM, and 36.2 ± 6.2 for DM + ulcer,  < 0.001. Corresponding exercise SMOEF was the lowest in DM + ulcers (0.48 ± 0.09). Exercise SMBF in the soleus muscle was correlated moderately with the Yale physical activity survey ( = 0.39,  < 0.01).

Conclusions: Contrast-free MR imaging identified progressively impaired regional microcirculation in medial gastrocnemius muscles of people with DM with and without foot ulcers. Exercise SMBF in the medial gastrocnemius muscle was the most sensitive index and was associated with HbA1c. Lower exercise SMBF in the soleus muscle was associated with lower Yale score.
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http://dx.doi.org/10.1177/14791641211029002DOI Listing
July 2021

A Path to Qualification of PET/MR Scanners for Multicenter Brain Imaging Studies: Evaluation of MR-based Attenuation Correction Methods Using a Patient Phantom.

J Nucl Med 2021 Jul 22. Epub 2021 Jul 22.

University of California, San Francisco.

Positron emission tomography and magnetic resonance imaging (PET/MRI) scanners cannot be qualified in the manner adopted for hybrid PET and computed tomography (CT) devices. The main hurdle with qualification in PET/MRI is that attenuation correction (AC) cannot be adequately measured in conventional PET phantoms due to the difficulty in converting the MRI images of the physical structures (e.g., plastic) into electron density maps. Over the last decade, a plethora of novel MR-based algorithms have been developed to more accurately derive the attenuation properties of the human head, including the skull. Although very promising, none of these techniques has yet emerged as an optimal and universally adopted strategy for AC in PET/MRI. In this work, we propose a path for PET/MRI qualification for multicenter brain imaging studies. Specifically, our solution is to separate the head attenuation correction from the other factors that affect PET data quantification and use a patient as a phantom to assess the former. The emission data collected on the integrated PET/MRI scanner to be qualified should be reconstructed using both MR- and CT-based AC methods and whole-brain qualitative and quantitative (both voxel-wise and regional) analyses should be performed. The MR-based approach will be considered satisfactory if the PET quantification bias is within the acceptance criteria specified herein. We have implemented this approach successfully across two PET/MRI scanner manufacturers at two sites.
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http://dx.doi.org/10.2967/jnumed.120.261881DOI Listing
July 2021

Cerebral Oxygen Metabolic Stress, Microstructural Injury, and Infarction in Adults With Sickle Cell Disease.

Neurology 2021 Jun 25. Epub 2021 Jun 25.

Department of Neurology, Washington University School of Medicine, St. Louis, MO;

Objective: To determine the patient- and tissue-based relationships between cerebral hemodynamic and oxygen metabolic stress, microstructural injury, and infarct location in adults with sickle cell disease (SCD).

Methods: Control and SCD participants underwent brain MRI to quantify cerebral blood flow (CBF), oxygen extraction fraction (OEF), mean diffusivity (MD), and fractional anisotropy (FA) within normal-appearing white matter (NAWM), and infarcts on FLAIR. Multivariable linear regression examined the patient- and voxel-based associations between hemodynamic and metabolic stress (defined as elevated CBF and OEF, respectively), white matter microstructure, and infarct location.

Results: Of 83 control and SCD participants, adults with SCD demonstrated increased CBF (50.9 vs 38.8 mL/min/100g, 0.001), increased OEF (0.35 vs 0.25, 0.001), increased MD (0.76 vs 0.72 x 10mm s, =0.005), and decreased FA (0.40 vs 0.42, =0.021) within NAWM compared to controls. In multivariable analysis, increased OEF (β=0.19, =0.035), but not CBF (β=0.00, =0.340), independently predicted increased MD in the SCD cohort, while neither were predictors in controls. On voxel-wise regression, the SCD cohort demonstrated widespread OEF elevation, encompassing deep white matter regions of elevated MD and reduced FA, which spatially extended beyond high density infarct locations from the SCD cohort.

Conclusion: Elevated OEF, a putative index of cerebral oxygen metabolic stress, may provide a metric of ischemic vulnerability which could enable individualization of therapeutic strategies in SCD. The patient- and tissue-based relationships between elevated OEF, elevated MD, and cerebral infarcts suggest that oxygen metabolic stress may underlie microstructural injury prior to the development of cerebral infarcts in SCD.
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http://dx.doi.org/10.1212/WNL.0000000000012404DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8408504PMC
June 2021

Identifying key mononuclear Fe species for low-temperature methane oxidation.

Chem Sci 2021 Jan 8;12(9):3152-3160. Epub 2021 Jan 8.

CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China

The direct functionalization of methane into platform chemicals is arguably one of the holy grails in chemistry. The actual active sites for methane activation are intensively debated. By correlating a wide variety of characterization results with catalytic performance data we have been able to identify mononuclear Fe species as the active site in the Fe/ZSM-5 zeolites for the mild oxidation of methane with HO at 50 °C. The 0.1% Fe/ZSM-5 catalyst with dominant mononuclear Fe species possess an excellent turnover rate (TOR) of 66 mol mol h, approximately 4 times higher compared to the state-of-the-art dimer-containing Fe/ZSM-5 catalysts. Based on a series of advanced spectroscopic studies and H- and C- nuclear magnetic resonance (NMR), we found that methane activation initially proceeds on the Fe site of mononuclear Fe species. With the aid of adjacent Brønsted acid sites (BAS), methane can be first oxidized to CHOOH and CHOH, and then subsequently converted into HOCHOOH and consecutively into HCOOH. These findings will facilitate the search towards new metal-zeolite combinations for the activation of C-H bonds in various hydrocarbons, for light alkanes and beyond.
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http://dx.doi.org/10.1039/d0sc06067dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8179404PMC
January 2021

Phase2Phase: Respiratory Motion-Resolved Reconstruction of Free-Breathing Magnetic Resonance Imaging Using Deep Learning Without a Ground Truth for Improved Liver Imaging.

Invest Radiol 2021 May 19. Epub 2021 May 19.

From the Mallinckrodt Institute of Radiology Department of Computer Science & Engineering Department of Biomedical Engineering Department of Surgery Department of Electrical and System Engineering, Washington University in St. Louis, Missouri Siemens Healthcare GmbH, Erlangen, Germany Siemens Healthineers, St. Louis, Missouri Department of Neurology, Washington University in St. Louis, Missouri.

Objectives: Respiratory binning of free-breathing magnetic resonance imaging data reduces motion blurring; however, it exacerbates noise and introduces severe artifacts due to undersampling. Deep neural networks can remove artifacts and noise but usually require high-quality ground truth images for training. This study aimed to develop a network that can be trained without this requirement.

Materials And Methods: This retrospective study was conducted on 33 participants enrolled between November 2016 and June 2019. Free-breathing magnetic resonance imaging was performed using a radial acquisition. Self-navigation was used to bin the k-space data into 10 respiratory phases. To simulate short acquisitions, subsets of radial spokes were used in reconstructing images with multicoil nonuniform fast Fourier transform (MCNUFFT), compressed sensing (CS), and 2 deep learning methods: UNet3DPhase and Phase2Phase (P2P). UNet3DPhase was trained using a high-quality ground truth, whereas P2P was trained using noisy images with streaking artifacts. Two radiologists blinded to the reconstruction methods independently reviewed the sharpness, contrast, and artifact-freeness of the end-expiration images reconstructed from data collected at 16% of the Nyquist sampling rate. The generalized estimating equation method was used for statistical comparison. Motion vector fields were derived to examine the respiratory motion range of 4-dimensional images reconstructed using different methods.

Results: A total of 15 healthy participants and 18 patients with hepatic malignancy (50 ± 15 years, 6 women) were enrolled. Both reviewers found that the UNet3DPhase and P2P images had higher contrast (P < 0.01) and fewer artifacts (P < 0.01) than the CS images. The UNet3DPhase and P2P images were reported to be sharper than the CS images by 1 reviewer (P < 0.01) but not by the other reviewer (P = 0.22, P = 0.18). UNet3DPhase and P2P were similar in sharpness and contrast, whereas UNet3DPhase had fewer artifacts (P < 0.01). The motion vector lengths for the MCNUFFT800 and P2P800 images were comparable (10.5 ± 4.2 mm and 9.9 ± 4.0 mm, respectively), whereas both were significantly larger than CS2000 (7.0 ± 3.9 mm; P < 0.0001) and UNnet3DPhase800 (6.9 ± 3.2; P < 0.0001) images.

Conclusions: Without a ground truth, P2P can reconstruct sharp, artifact-free, and high-contrast respiratory motion-resolved images from highly undersampled data. Unlike the CS and UNet3DPhase methods, P2P did not artificially reduce the respiratory motion range.
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http://dx.doi.org/10.1097/RLI.0000000000000792DOI Listing
May 2021

Sub-Second Time-Resolved Surface-Enhanced Raman Spectroscopy Reveals Dynamic CO Intermediates during Electrochemical CO Reduction on Copper.

Angew Chem Int Ed Engl 2021 Jul 15;60(30):16576-16584. Epub 2021 Jun 15.

Inorganic Chemistry and Catalysis, Institute for Sustainable and Circular Chemistry, Utrecht University, Universiteitsweg 99, 3584, CG, Utrecht, The Netherlands.

The electrocatalytic carbon dioxide (CO ) reduction reaction (CO RR) into hydrocarbons is a promising approach for greenhouse gas mitigation, but many details of this dynamic reaction remain elusive. Here, time-resolved surface-enhanced Raman spectroscopy (TR-SERS) is employed to successfully monitor the dynamics of CO RR intermediates and Cu surfaces with sub-second time resolution. Anodic treatment at 1.55 V vs. RHE and subsequent surface oxide reduction (below -0.4 V vs. RHE) induced roughening of the Cu electrode surface, which resulted in hotspots for TR-SERS, enhanced time resolution (down to ≈0.7 s) and fourfold improved CO RR efficiency toward ethylene. With TR-SERS, the initial restructuring of the Cu surface was followed (<7 s), after which a stable surface surrounded by increased local alkalinity was formed. Our measurements revealed that a highly dynamic CO intermediate, with a characteristic vibration below 2060 cm , is related to C-C coupling and ethylene production (-0.9 V vs. RHE), whereas lower cathodic bias (-0.7 V vs. RHE) resulted in gaseous CO production from isolated and static CO surface species with a distinct vibration at 2092 cm .
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http://dx.doi.org/10.1002/anie.202104114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8362134PMC
July 2021

Transcriptome and lipidome profile of human mesenchymal stem cells with reduced senescence and increased trilineage differentiation ability upon drug treatment.

Aging (Albany NY) 2021 03 26;13(7):9991-10014. Epub 2021 Mar 26.

School of Life Science and Technology, Harbin Institute of Technology, Harbin 150080, Heilongjiang, China.

Human Mesenchymal stem cells (hMSCs) are multi-potential cells which are widely used in cell therapy. However, the frequently emerged senescence and decrease of differentiation capabilities limited the broad applications of MSC. Several strategies such as small molecules treatment have been widely studied and used to improve the stem characteristics bypassing the senescence but the exact mechanisms for them to reduce senescence have not been fully studied. In this study, hMSCs were treated by rapamycin, oltipraz, metformin, and vitamin C for the indicated time and these cells were subjected to senescence evaluation and trilineage differentiation. Furthermore, transcriptomics and lipidomics datasets of hMSCs after drug treatment were analyzed to interpret biological pathways responsible for their anti-senescence effects. Although four drugs exhibited significant activities in promoting MSC osteogenic differentiation, metformin is the optimal drug to promote trilineage differentiation. GO terms illustrated that the anti-aging effects of drugs were mainly associated with cellular senescence, mitotic and meiosis process. Biosynthesis of phosphatidylcholines (PC) and phosphatidylethanolamine (PE) were inhibited whereas production of phosphatidylinositols (PIs) and saturated fatty acids (SFA)/ mono-unsaturated fatty acids (MUFA) conversion was activated. Medium free fatty acids (FFA) was increased in hMSCs with different anti-aging phenotypes. Therefore, we established a comprehensive method in assessing drug intervention based on the results of transcriptomics and lipidomics. The method can be used to study different biological phenotypes upon drug intervention in MSC which will extend the clinical application of hMSCs.
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http://dx.doi.org/10.18632/aging.202759DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8064146PMC
March 2021

Pilot study of contrast-free MRI reveals significantly impaired calf skeletal muscle perfusion in diabetes with incompressible peripheral arteries.

Vasc Med 2021 Aug 22;26(4):367-373. Epub 2021 Mar 22.

Physical Therapy Program, Washington University School of Medicine, St Louis, MO, USA.

Patients with diabetes mellitus (DM) are more likely to have densely calcified lesions in the below-the-knee tibial arteries. However, the relationship between peripheral arterial calcification and local skeletal muscle perfusion has not been explored. Thirty subjects were prospectively recruited into three groups in this pilot study: (1) Non-DM: 10 people without DM; (2) DM, ABI < 1.3: 10 people with DM and normal ankle-brachial index (ABI) (0.9-1.3); and (3) DM, ABI ⩾ 1.3: 10 people with DM and ABI ⩾ 1.3. All subjects underwent calf perfusion measurements at rest and during an isometric plantarflexion contraction exercise within the magnetic resonance imaging (MRI) system. The noncontrast MRI techniques were applied to quantitatively assess skeletal muscle blood flow (SMBF) and oxygen extraction fraction (SMOEF) in medial gastrocnemius and soleus muscles. Both SMBF and SMOEF reserves were calculated as the ratio of the exercise value to the resting value. Exercise SMBF and SMOEF values in the medial gastrocnemius muscle were lower in the two DM groups than in the non-DM group ( < 0.05). The SMBF reserve in medial gastrocnemius was significantly lower in the DM, ABI ⩾ 1.3 group compared to the DM, ABI < 1.3 group ( < 0.05). This study demonstrates that people with DM and calcified arteries had lower perfusion in gastrocnemius muscle compared to those without DM and those with DM and a normal ABI.
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http://dx.doi.org/10.1177/1358863X21996465DOI Listing
August 2021

Stabilization effects in binary colloidal Cu and Ag nanoparticle electrodes under electrochemical CO reduction conditions.

Nanoscale 2021 Mar;13(9):4835-4844

Inorganic Chemistry and Catalysis group, Institute for Sustainable and Circular Chemistry, Utrecht University, 3584 CG Utrecht, The Netherlands.

Nanoparticle modified electrodes constitute an attractive way to tailor-make efficient carbon dioxide (CO2) reduction catalysts. However, the restructuring and sintering processes of nanoparticles under electrochemical reaction conditions not only impedes the widespread application of nanoparticle catalysts, but also misleads the interpretation of the selectivity of the nanocatalysts. Here, we colloidally synthesized metallic copper (Cu) and silver (Ag) nanoparticles with a narrow size distribution (<10%) and utilized them in electrochemical CO2 reduction reactions. Monometallic Cu and Ag nanoparticle electrodes showed severe nanoparticle sintering already at low overpotential of -0.8 V vs. RHE, as evidenced by ex situ SEM investigations, and potential-dependent variations in product selectivity that resemble bulk Cu (14% for ethylene at -1.3 V vs. RHE) and Ag (69% for carbon monoxide at -1.0 V vs. RHE). However, by co-deposition of Cu and Ag nanoparticles, a nanoparticle stabilization effect was observed between Cu and Ag, and the sintering process was greatly suppressed at CO2 reducing potentials (-0.8 V vs. RHE). Furthermore, by varying the Cu/Ag nanoparticle ratio, the CO2 reduction reaction (CO2RR) selectivity towards methane (maximum of 20.6% for dense Cu2.5-Ag1 electrodes) and C2 products (maximum of 15.7% for dense Cu1-Ag1 electrodes) can be tuned, which is attributed to a synergistic effect between neighbouring Ag and Cu nanoparticles. We attribute the stabilization of the nanoparticles to the positive enthalpies of Cu-Ag solid solutions, which prevents the dissolution-redeposition induced particle growth under CO2RR conditions. The observed nanoparticle stabilization effect enables the design and fabrication of active CO2 reduction nanocatalysts with high durability.
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http://dx.doi.org/10.1039/d0nr09040aDOI Listing
March 2021

Deep learning-based T1-enhanced selection of linear attenuation coefficients (DL-TESLA) for PET/MR attenuation correction in dementia neuroimaging.

Magn Reson Med 2021 07 8;86(1):499-513. Epub 2021 Feb 8.

Department of Neurology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA.

Purpose: The accuracy of existing PET/MR attenuation correction (AC) has been limited by a lack of correlation between MR signal and tissue electron density. Based on our finding that longitudinal relaxation rate, or R , is associated with CT Hounsfield unit in bone and soft tissues in the brain, we propose a deep learning T -enhanced selection of linear attenuation coefficients (DL-TESLA) method to incorporate quantitative R for PET/MR AC and evaluate its accuracy and longitudinal test-retest repeatability in brain PET/MR imaging.

Methods: DL-TESLA uses a 3D residual UNet (ResUNet) for pseudo-CT (pCT) estimation. With a total of 174 participants, we compared PET AC accuracy of DL-TESLA to 3 other methods adopting similar 3D ResUNet structures but using UTE , or Dixon, or T -MPRAGE as input. With images from 23 additional participants repeatedly scanned, the test-retest differences and within-subject coefficient of variation of standardized uptake value ratios (SUVR) were compared between PET images reconstructed using either DL-TESLA or CT for AC.

Results: DL-TESLA had (1) significantly lower mean absolute error in pCT, (2) the highest Dice coefficients in both bone and air, (3) significantly lower PET relative absolute error in whole brain and various brain regions, (4) the highest percentage of voxels with a PET relative error within both ±3% and ±5%, (5) similar to CT test-retest differences in SUVRs from the cerebrum and mean cortical (MC) region, and (6) similar to CT within-subject coefficient of variation in cerebrum and MC.

Conclusion: DL-TESLA demonstrates excellent PET/MR AC accuracy and test-retest repeatability.
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http://dx.doi.org/10.1002/mrm.28689DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8091494PMC
July 2021

Quantification of myocardial oxygen extraction fraction: A proof-of-concept study.

Magn Reson Med 2021 06 26;85(6):3318-3325. Epub 2021 Jan 26.

Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA.

Purpose: To demonstrate a proof of concept for the measurement of myocardial oxygen extraction fraction (mOEF) by a cardiovascular magnetic resonance technique.

Methods: The mOEF measurement was performed using an electrocardiogram-triggered double-echo asymmetric spin-echo sequence with EPI readout. Seven healthy volunteers (22-37 years old, 5 females) were recruited and underwent the same imaging scans at rest on 2 different days for reproducibility assessment. Another 5 subjects (23-37 years old, 4 females) underwent cardiovascular magnetic resonance studies at rest and during a handgrip isometric exercise with a 25% of maximal voluntary contraction. Both mOEF and myocardial blood volume values were obtained in septal regions from respective maps.

Results: The reproducibility was excellent for the measurements of mOEF in septal myocardium (coefficient of variation: 3.37%) and moderate for myocardial blood volume (coefficient of variation: 19.7%). The average mOEF and myocardial blood volume of 7 subjects at rest were 0.61 ± 0.05 and 11.0 ± 4.3%, respectively. The mOEF agreed well with literature values that were measured by PET in healthy volunteers. In the exercise study, there was no significant change in mOEF (0.61 ± 0.06 vs 0.62 ± 0.07) or myocardial blood volume (12 ± 6% vs 13 ± 4%) from rest to exercise, as expected.

Conclusion: The implemented cardiovascular magnetic resonance method shows potential for the quantitative assessment of mOEF in vivo. Future technical work is needed to improve image quality and to further validate mOEF measurements.
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http://dx.doi.org/10.1002/mrm.28673DOI Listing
June 2021

Bulk volume susceptibility difference between deoxyhemoglobin and oxyhemoglobin for HbA and HbS: A comparative study.

Magn Reson Med 2021 06 21;85(6):3383-3393. Epub 2021 Jan 21.

Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA.

Purpose: Sickle cell anemia is a blood disorder that alters the morphology and the oxygen affinity of the red blood cells. Cerebral oxygen extraction fraction measurements using quantitative BOLD contrast have been used for assessing inadequate oxygen delivery and the subsequent risk of ischemic stroke in sickle cell anemia. The BOLD signal in MRI studies relies on , the bulk volume susceptibility difference between fully oxygenated and fully deoxygenated blood. Several studies have measured for normal hemoglobin A (HbA). However, it is not known whether the value is different for sickle hemoglobin. In this study, was measured for both HbA and sickle hemoglobin.

Methods: Six sickle cell anemia patients and 6 controls were recruited. Various blood oxygenation levels were achieved through in vivo manipulations to keep the blood close to its natural state. To account for the differences in oxygen affinity, Hill's equations were used to translate partial pressure of oxygen to oxygen saturation for HbA, sickle hemoglobin, and fetal hemoglobin (HbF) separately. The pH and PCO corrections were performed. Temperature and magnetic field drift were controlled for. A multivariate generalized linear mixed model with random participant effect was used.

Results: Assuming that is similar for HbA and HbF and that is 5/4 of for HbA, it was found that the values for HbA and sickle hemoglobin were not statistically significantly different from each other.

Conclusion: The same value can be used for both types of hemoglobin in quantitative BOLD analysis.
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http://dx.doi.org/10.1002/mrm.28668DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7945010PMC
June 2021

Obesity and White Matter Neuroinflammation Related Edema in Alzheimer's Disease Dementia Biomarker Negative Cognitively Normal Individuals.

J Alzheimers Dis 2021 ;79(4):1801-1811

Mallinckrodt Institute of Radiology, Division of Neuroradiology, Washington University in St. Louis, St. Louis, MO, USA.

Background: Obesity is related to quantitative neuroimaging abnormalities including reduced gray matter volumes and impaired white matter microstructural integrity, although the underlying mechanisms are not well understood.

Objective: We assessed influence of obesity on neuroinflammation imaging that may mediate brain morphometric changes. Establishing the role of neuroinflammation in obesity will enhance understanding of this modifiable disorder as a risk factor for Alzheimer's disease (AD) dementia.

Methods: We analyzed brain MRIs from 104 cognitively normal participants (CDR = 0) and biomarker negativity for CSF amyloid or tau. We classified body mass index (BMI) as normal (BMI <25, N = 62) or overweight and obese (BMI ≥25, N = 42). Blood pressure was measured. BMI and blood pressure classifications were related to neuroinflammation imaging (NII) derived edema fraction in 17 white matter tracts. This metric was also correlated to hippocampal volumes and CSF biomarkers of inflammation and neurodegeneration: YKL-40, SNAP25, VILIP, tau, and NFL.

Results: Participants with BMI <25 had lower NII-derived edema fraction, with protective effects of normal blood pressure. Statistically significant white matter tracts included the internal capsule, external capsule, and corona radiata, FDR correc-ted for multiple comparisons to alpha = 0.05. Higher NII-derived edema fractions in the internal capsule, corpus callosum, gyrus, and superior fronto-occipital fasciculus were related with smaller hippocampal volumes only in individuals with BMI ≥25. There were no statistically significant correlations between NII-derived edema fraction and CSF biomarkers.

Conclusion: We demonstrate statistically significant relationships between neuroinflammation, elevated BMI, and hippocampal volume, raising implications for neuroinflammation mechanisms of obesity-related brain dysfunction in cognitively normal elderly.
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http://dx.doi.org/10.3233/JAD-201242DOI Listing
September 2021

Cerebral oxygen extraction fraction (OEF): Comparison of challenge-free gradient echo QSM+qBOLD (QQ) with O PET in healthy adults.

J Cereb Blood Flow Metab 2021 07 27;41(7):1658-1668. Epub 2020 Nov 27.

Department of Radiology, Weill Cornell Medical College, New York, USA.

We aimed to validate oxygen extraction fraction (OEF) estimations by quantitative susceptibility mapping plus quantitative blood oxygen-level dependence (QSM+qBOLD, or QQ) using O-PET. In ten healthy adult brains, PET and MRI were acquired simultaneously on a PET/MR scanner. PET was acquired using C[O], O[O], and H[O]. Image-derived arterial input functions and standard models of oxygen metabolism provided quantification of PET. MRI included T1-weighted imaging, time-of-flight angiography, and multi-echo gradient-echo imaging that was processed for QQ. Region of interest (ROI) analyses compared PET OEF and QQ OEF. In ROI analyses, the averaged OEF differences between PET and QQ were generally small and statistically insignificant. For whole brains, the average and standard deviation of OEF was 32.8 ± 6.7% for PET; OEF was 34.2 ± 2.6% for QQ. Bland-Altman plots quantified agreement between PET OEF and QQ OEF. The interval between the 95% limits of agreement was 16.9 ± 4.0% for whole brains. Our validation study suggests that respiratory challenge-free QQ-OEF mapping may be useful for non-invasive clinical assessment of regional OEF impairment.
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http://dx.doi.org/10.1177/0271678X20973951DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8221765PMC
July 2021

Optimal co-clinical radiomics: Sensitivity of radiomic features to tumour volume, image noise and resolution in co-clinical T1-weighted and T2-weighted magnetic resonance imaging.

EBioMedicine 2020 Sep 2;59:102963. Epub 2020 Sep 2.

Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, MO USA. Electronic address:

Background: Radiomics analyses has been proposed to interrogate the biology of tumour as well as to predict/assess response to therapy in vivo. The objective of this work was to assess the sensitivity of radiomics features to noise, resolution, and tumour volume in the context of a co-clinical trial.

Methods: Triple negative breast cancer (TNBC) patients were recruited into an ongoing co-clinical imaging trial. Sub-typed matched TNBC patient-derived tumour xenografts (PDX) were generated to investigate optimal co-clinical MR radiomic features. The MR imaging protocol included T1-weighed and T2-weighted imaging. To test the sensitivity of radiomics to resolution, PDX were imaged at three different resolutions. Multiple sets of images with varying signal-to-noise ratio (SNR) were generated, and an image independent patch-based method was implemented to measure the noise levels. Forty-eight radiomic features were extracted from manually segmented 2D and 3D segmented tumours and normal tissues of T1- and T2- weighted co-clinical MR images.

Findings: Sixteen radiomics features were identified as volume dependent and corrected for volume-dependency following normalization. Features from grey-level run-length matrix (GLRLM), grey-level size zone matrix (GLSZM) were identified as most sensitive to noise. Radiomic features Kurtosis and Run-length variance (RLV) from GLSZM were most sensitive to changes in resolution in both T1w and T2w MRI. In general, 3D radiomic features were more robust compared to 2D (single slice) measures, although the former exhibited higher variability between subjects.

Interpretation: Tumour volume, noise characteristics, and image resolution significantly impact radiomic analysis in co-clinical studies.
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http://dx.doi.org/10.1016/j.ebiom.2020.102963DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7479492PMC
September 2020

Lesion evolution and neurodegeneration in RVCL-S: A monogenic microvasculopathy.

Neurology 2020 10 4;95(14):e1918-e1931. Epub 2020 Sep 4.

From the Department of Neurology (A.L.F., V.W.C., S.F., M.B.M., A.M.B., V.B., Y.T., P.K., Y.C., J.H., J.-M.L.), Mallinckrodt Institute of Radiology (A.L.F., J.-M.L., H.A.), Department of Ophthalmology (M.G.G.), and Department of Medicine (M.B., M.K.L., D.H., J.J.M., J.P.A.), Division of Rheumatology, Washington University School of Medicine, St. Louis, MO; Department of Radiology (D.L.), The Johns Hopkins University School of Medicine, Baltimore, MD; and Department of Neurology (J.C.J.), Icahn School of Medicine at Mount Sinai, New York, NY.

Objective: To characterize lesion evolution and neurodegeneration in retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) using multimodal MRI.

Methods: We prospectively performed MRI and cognitive testing in RVCL-S and healthy control cohorts. Gray and white matter volume and disruption of white matter microstructure were quantified. Asymmetric spin echo acquisition permitted voxel-wise oxygen extraction fraction (OEF) calculation as an in vivo marker of microvascular ischemia. The RVCL-S cohort was included in a longitudinal analysis of lesion subtypes in which hyperintense lesions on fluid-attenuated inversion recovery (FLAIR), T1-postgadolinium, and diffusion-weighted imaging were delineated and quantified volumetrically.

Results: Twenty individuals with RVCL-S and 26 controls were enrolled. White matter volume and microstructure declined faster in those with RVCL-S compared to controls. White matter atrophy in RVCL-S was highly linear (ρ = -0.908, < 0.0001). Normalized OEF was elevated in RVCL-S and increased with disease duration. Multiple cognitive domains, specifically those measuring working memory and processing speed, were impaired in RVCL-S. Lesion volumes, regardless of subtype, progressed/regressed with high variability as a function of age, while FLAIR lesion burden increased near time to death ( < 0.001).

Conclusion: RVCL-S is a monogenic microvasculopathy affecting predominantly the white matter with regard to atrophy and cognitive impairment. White matter volumes in RVCL-S declined linearly, providing a potential metric against which to test the efficacy of future therapies. Progressive elevation of white matter OEF suggests that microvascular ischemia may underlie neurodegeneration in RVCL-S.
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http://dx.doi.org/10.1212/WNL.0000000000010659DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7682842PMC
October 2020

Functional Connectivity Decreases with Metabolic Stress in Sickle Cell Disease.

Ann Neurol 2020 11 16;88(5):995-1008. Epub 2020 Sep 16.

Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA.

Objective: Children with sickle cell disease (SCD) experience cognitive deficits even when unaffected by stroke. Using functional connectivity magnetic resonance imaging (MRI) as a potential biomarker of cognitive function, we tested our hypothesis that children with SCD would have decreased functional connectivity, and that children experiencing the greatest metabolic stress, indicated by elevated oxygen extraction fraction, would have the lowest connectivity.

Methods: We prospectively obtained brain MRIs and cognitive testing in healthy controls and children with SCD.

Results: We analyzed data from 60 participants (20 controls and 40 with sickle cell disease). There was no difference in global cognition or cognitive subdomains between cohorts. However, we found decreased functional connectivity within the sensory-motor, lateral sensory-motor, auditory, salience, and subcortical networks in participants with SCD compared with controls. Further, as white matter oxygen extraction fraction increased, connectivity within the visual (p = 0.008, parameter estimate = -0.760 [95% CI = -1.297, -0.224]), default mode (p = 0.012, parameter estimate = -0.417 [95% CI = -0.731, -0.104]), and cingulo-opercular (p = 0.009, parameter estimate = -0.883 [95% CI = -1.517, -0.250]) networks decreased.

Interpretation: We conclude that there is diminished functional connectivity within these anatomically contiguous networks in children with SCD compared with controls, even when differences are not seen with cognitive testing. Increased white matter oxygen extraction fraction was associated with decreased connectivity in select networks. These data suggest that elevated oxygen extraction fraction and disrupted functional connectivity are potentially presymptomatic neuroimaging biomarkers for cognitive decline in SCD. ANN NEUROL 2020;88:995-1008.
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http://dx.doi.org/10.1002/ana.25891DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7592195PMC
November 2020

Quantification of brain oxygen extraction and metabolism with [O]-gas PET: A technical review in the era of PET/MRI.

Neuroimage 2020 10 4;220:117136. Epub 2020 Jul 4.

Department of Radiology, Stanford University, Stanford, CA, USA.

Oxygen extraction fraction (OEF) and the cerebral metabolic rate of oxygen (CMRO) are key cerebral physiological parameters to identify at-risk cerebrovascular patients and understand brain health and function. PET imaging with [O]-oxygen tracers, either through continuous or bolus inhalation, provides non-invasive assessment of OEF and CMRO. Numerous tracer delivery, PET acquisition, and kinetic modeling approaches have been adopted to map brain oxygenation. The purpose of this technical review is to critically evaluate different methods for [O]-gas PET and its impact on the accuracy and reproducibility of OEF and CMRO measurements. We perform a meta-analysis of brain oxygenation PET studies in healthy volunteers and compare between continuous and bolus inhalation techniques. We also describe OEF metrics that have been used to detect hemodynamic impairment in cerebrovascular disease. For these patients, advanced techniques to accelerate the PET scans and potential synthesis with MRI to avoid arterial blood sampling would facilitate broader use of [O]-oxygen PET for brain physiological assessment.
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http://dx.doi.org/10.1016/j.neuroimage.2020.117136DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7592419PMC
October 2020

Magnetic resonance safety assessment of a new trend: magnetic eyelashes.

J Appl Clin Med Phys 2020 Aug 20;21(8):323-325. Epub 2020 Jun 20.

Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, USA.

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http://dx.doi.org/10.1002/acm2.12952DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7484819PMC
August 2020

Evaluating the Use of rCBV as a Tumor Grade and Treatment Response Classifier Across NCI Quantitative Imaging Network Sites: Part II of the DSC-MRI Digital Reference Object (DRO) Challenge.

Tomography 2020 06;6(2):203-208

Division of Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ.

We have previously characterized the reproducibility of brain tumor relative cerebral blood volume (rCBV) using a dynamic susceptibility contrast magnetic resonance imaging digital reference object across 12 sites using a range of imaging protocols and software platforms. As expected, reproducibility was highest when imaging protocols and software were consistent, but decreased when they were variable. Our goal in this study was to determine the impact of rCBV reproducibility for tumor grade and treatment response classification. We found that varying imaging protocols and software platforms produced a range of optimal thresholds for both tumor grading and treatment response, but the performance of these thresholds was similar. These findings further underscore the importance of standardizing acquisition and analysis protocols across sites and software benchmarking.
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http://dx.doi.org/10.18383/j.tom.2020.00012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7289259PMC
June 2020

3D pediatric cranial bone imaging using high-resolution MRI for visualizing cranial sutures: a pilot study.

J Neurosurg Pediatr 2020 Jun 12:1-7. Epub 2020 Jun 12.

2Mallinckrodt Institute of Radiology, and.

Objective: There is an unmet need to perform imaging in young children and obtain CT-equivalent cranial bone images without subjecting the patients to radiation. In this study, the authors propose using a high-resolution fast low-angle shot golden-angle 3D stack-of-stars radial volumetric interpolated breath-hold examination (GA-VIBE) MRI sequence that is intrinsically robust to motion and has enhanced bone versus soft-tissue contrast.

Methods: Patients younger than 11 years of age, who underwent clinical head CT scanning for craniosynostosis or other cranial malformations, were eligible for the study. 3D reconstructed images created from the GA-VIBE MRI sequence and the gold-standard CT scan were randomized and presented to 3 blinded reviewers. For all image sets, each reviewer noted the presence or absence of the 6 primary cranial sutures and recorded on 5-point Likert scales whether they recommended a second scan be performed.

Results: Eleven patients (median age 1.8 years) underwent MRI after clinical head CT scanning was performed. Five of the 11 patients were sedated. Three clinicians reviewed the images, and there were no cases, either with CT scans or MR images, in which a reviewer agreed a repeat scan was required for diagnosis or surgical planning. The reviewers reported clear imaging of the regions of interest on 99% of the CT reviews and 96% of the MRI reviews. With CT as the standard, the sensitivity and specificity of the GA-VIBE MRI sequence to detect suture closure were 97% and 96%, respectively (n = 198 sutures read).

Conclusions: The 3D reconstructed images using the GA-VIBE sequence in comparison to the CT scans created clinically acceptable cranial images capable of detecting cranial sutures. Future directions include reducing the scan time, improving motion correction, and automating postprocessing for clinical utility.
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http://dx.doi.org/10.3171/2020.4.PEDS20131DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7736460PMC
June 2020

Bone material analogues for PET/MRI phantoms.

Med Phys 2020 Jun 13;47(5):2161-2170. Epub 2020 Mar 13.

Department of Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, CA, 94143, USA.

Purpose: To develop bone material analogues that can be used in construction of phantoms for simultaneous PET/MRI systems.

Methods: Plaster was used as the basis for the bone material analogues tested in this study. It was mixed with varying concentrations of an iodinated CT contrast, a gadolinium-based MR contrast agent, and copper sulfate to modulate the attenuation properties and MRI properties (T1 and T2*). Attenuation was measured with CT and Ge transmission scans, and MRI properties were measured with quantitative ultrashort echo time pulse sequences. A proof-of-concept skull was created by plaster casting.

Results: Undoped plaster has a 511 keV attenuation coefficient (~0.14 cm ) similar to cortical bone (0.10-0.15 cm ), but slightly longer T1 (~500 ms) and T2* (~1.2 ms) MR parameters compared to bone (T1 ~ 300 ms, T2* ~ 0.4 ms). Doping with the iodinated agent resulted in increased attenuation with minimal perturbation to the MR parameters. Doping with a gadolinium chelate greatly reduced T1 and T2*, resulting in extremely short T1 values when the target T2* values were reached, while the attenuation coefficient was unchanged. Doping with copper sulfate was more selective for T2* shortening and achieved comparable T1 and T2* values to bone (after 1 week of drying), while the attenuation coefficient was unchanged.

Conclusions: Plaster doped with copper sulfate is a promising bone material analogue for a PET/MRI phantom, mimicking the MR properties (T1 and T2*) and 511 keV attenuation coefficient of human cortical bone.
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http://dx.doi.org/10.1002/mp.14079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7901472PMC
June 2020

Internal-Field-Enhanced Charge Separation in a Single-Domain Ferroelectric PbTiO Photocatalyst.

Adv Mater 2020 Feb 13;32(7):e1906513. Epub 2020 Jan 13.

State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, 730000, China.

Ferroelectric materials with spontaneous polarization-induced internal electric fields have drawn increasing attention in solar fuel production due to the intrinsic polarized structure. However, the origination of charge separation in these materials at the nano/microlevel is ambiguous owing to the complexity of the multielectric fields. Besides, the observed charge separation ability is far from theoretical expectation. Herein, by spatially resolved surface photovoltage spectroscopy, it is clearly demonstrated that the depolarization field in single-domain ferroelectric PbTiO (PTO) nanoplates is the main driving force for charge separation and it can effectively drive photogenerated electrons and holes to the positive and negative polarization facets, respectively. Moreover, the charge separation ability of PTO nanoplates increases with increasing particle size along the polarization direction, due to the increasing potential difference between the opposite polarization facets. Furthermore, this driving force for charge separation directly contributes to the enhancement of the photocatalytic hydrogen evolution reaction activity in ferroelectrics. Finally, it is proved that the screening field compensates part of the depolarization field and can be diminished by adding a dielectric layer on the ferroelectric surface. These findings demonstrate the importance of increasing the depolarization field and decreasing the screening field for efficient charge separation in ferroelectric semiconductor photocatalysts.
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http://dx.doi.org/10.1002/adma.201906513DOI Listing
February 2020

Spin-orbit torque manipulated by fine-tuning of oxygen-induced orbital hybridization.

Sci Adv 2019 11 1;5(11):eaax4278. Epub 2019 Nov 1.

Department of Applied Physics and Physico-Informatics, Keio University, Yokohama 223-8522, Japan.

Current-induced spin-orbit torques provide an effective way to manipulate magnetization in spintronic devices, promising for fast switching applications in nonvolatile memory and logic units. Recent studies have revealed that the spin-orbit torque is strongly altered by the oxidation of heterostructures with broken inversion symmetry. Although this finding opens a new field of metal-oxide spin-orbitronics, the role of the oxidation in the spin-orbit physics is still unclear. Here, we demonstrate a marked enhancement of the spin-orbit torque induced by a fine-tuning of oxygen-induced modification of orbital hybridization. This is evidenced by a concomitant enhancement of the interface spin-orbit torque, interface spin loss, and interface perpendicular magnetic anisotropy within a narrow range of the oxidation level of metallic heterostructures. This result reveals the crucial role of the atomic-scale effects in the generation of the spin-orbit torques, opening the door to atomic-level engineering of the spin-orbit physics.
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http://dx.doi.org/10.1126/sciadv.aax4278DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6824862PMC
November 2019

Repeatability of Quantitative Brown Adipose Tissue Imaging Metrics on Positron Emission Tomography with F-Fluorodeoxyglucose in Humans.

Cell Metab 2019 07 20;30(1):212-224.e4. Epub 2019 Jun 20.

Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, USA. Electronic address:

Brown adipose tissue (BAT) is a promising target for anti-obesity interventions. This prospective test-retest study assessed the repeatability of several important quantitative BAT metrics. After cold activation, 24 subjects underwent positron emission tomography (PET)/computed tomography (CT) and PET/magnetic resonance imaging (MRI), utilizing F-fluorodeoxyglucose. Repeat imaging occurred within 14 days per an identical protocol. BAT volumes were strongly correlated between sessions for PET/CT (intraclass correlation coefficient [ICC], 0.85) and PET/MRI (ICC, 0.82). BAT maximum lean-body-mass-adjusted standardized uptake values (SUL) were also strongly correlated between sessions for both PET/CT (ICC, 0.74) and PET/MRI (ICC, 0.83). Much longitudinal variability in BAT metrics was likely due to biological factors intrinsic to BAT, whole-body metabolic fluctuations, or temporal differences in cold-activation efficacy, rather than imaging factors. Future studies utilizing these imaging metrics to track the response BAT to interventions should incorporate this variation into sample-size considerations and response criteria.
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http://dx.doi.org/10.1016/j.cmet.2019.05.019DOI Listing
July 2019

Hydroxyurea reduces cerebral metabolic stress in patients with sickle cell anemia.

Blood 2019 05 11;133(22):2436-2444. Epub 2019 Mar 11.

Department of Neurology.

Chronic transfusion therapy (CTT) prevents stroke in selected patients with sickle cell anemia (SCA). We have shown that CTT mitigates signatures of cerebral metabolic stress, reflected by elevated oxygen extraction fraction (OEF), which likely drives stroke risk reduction. The region of highest OEF falls within the border zone, where cerebral blood flow (CBF) nadirs; OEF in this region was reduced after CTT. The neuroprotective efficacy of hydroxyurea (HU) remains unclear. To test our hypothesis that patients receiving HU therapy have lower cerebral metabolic stress compared with patients not receiving disease-modifying therapy, we prospectively obtained brain magnetic resonance imaging scans with voxel-wise measurements of CBF and OEF in 84 participants with SCA who were grouped by therapy: no disease-modifying therapy, HU, or CTT. There was no difference in whole-brain CBF among the 3 cohorts ( = .148). However, whole-brain OEF was significantly different ( < .001): participants without disease-modifying therapy had the highest OEF (median 42.9% [interquartile range (IQR) 39.1%-49.1%]), followed by HU treatment (median 40.7% [IQR 34.9%-43.6%]), whereas CTT treatment had the lowest values (median 35.3% [IQR 32.2%-38.9%]). Moreover, the percentage of white matter at highest risk for ischemia, defined by OEF greater than 40% and 42.5%, was lower in the HU cohort compared with the untreated cohort ( = .025 and = .034 respectively), but higher compared with the CTT cohort ( = .018 and = .029 respectively). We conclude that HU may offer neuroprotection by mitigating cerebral metabolic stress in patients with SCA, but not to the same degree as CTT.
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http://dx.doi.org/10.1182/blood-2018-09-876318DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6543515PMC
May 2019

Evaluating Multisite rCBV Consistency from DSC-MRI Imaging Protocols and Postprocessing Software Across the NCI Quantitative Imaging Network Sites Using a Digital Reference Object (DRO).

Tomography 2019 03;5(1):110-117

Division of Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ.

Relative cerebral blood volume (rCBV) cannot be used as a response metric in clinical trials, in part, because of variations in biomarker consistency and associated interpretation across sites, stemming from differences in image acquisition and postprocessing methods (PMs). This study leveraged a dynamic susceptibility contrast magnetic resonance imaging digital reference object to characterize rCBV consistency across 12 sites participating in the Quantitative Imaging Network (QIN), specifically focusing on differences in site-specific imaging protocols (IPs; n = 17), and PMs (n = 19) and differences due to site-specific IPs and PMs (n = 25). Thus, high agreement across sites occurs when 1 managing center processes rCBV despite slight variations in the IP. This result is most likely supported by current initiatives to standardize IPs. However, marked intersite disagreement was observed when site-specific software was applied for rCBV measurements. This study's results have important implications for comparing rCBV values across sites and trials, where variability in PMs could confound the comparison of therapeutic effectiveness and/or any attempts to establish thresholds for categorical response to therapy. To overcome these challenges and ensure the successful use of rCBV as a clinical trial biomarker, we recommend the establishment of qualifying and validating site- and trial-specific criteria for scanners and acquisition methods (eg, using a validated phantom) and the software tools used for dynamic susceptibility contrast magnetic resonance imaging analysis (eg, using a digital reference object where the ground truth is known).
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http://dx.doi.org/10.18383/j.tom.2018.00041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6403027PMC
March 2019

Measurement Repeatability of F-FDG PET/CT Versus F-FDG PET/MRI in Solid Tumors of the Pelvis.

J Nucl Med 2019 08 7;60(8):1080-1086. Epub 2019 Feb 7.

Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri.

Knowledge of the within-subject variability of F-FDG PET/MRI measurements is necessary for proper interpretation of quantitative PET or MRI metrics in the context of therapeutic efficacy assessments with integrated PET/MRI scanners. The goal of this study was to determine the test-retest repeatability of these metrics on PET/MRI, with comparison to similar metrics acquired by PET/CT. This prospective study enrolled subjects with pathology-proven pelvic malignancies. Baseline imaging consisted of PET/CT immediately followed by PET/MRI, using a single 370-MBq F-FDG dose. Repeat imaging was performed within 7 d using an identical imaging protocol, with no oncologic therapy between sessions. PET imaging on both scanners consisted of a list-mode acquisition at a single pelvic station. The MRI consisted of 2-point Dixon imaging for attenuation correction, standard sequences for anatomic correlation, and diffusion-weighted imaging. PET data were statically reconstructed using various frame durations and minimizing uptake time differences between sessions. SUV metrics were extracted for both PET/CT and PET/MRI in each imaging session. Apparent diffusion coefficient (ADC) metrics were extracted for both PET/MRI sessions. The study cohort consisted of 14 subjects (13 female, 1 male) with various pelvic cancers (11 cervical, 2 rectal, 1 endometrial). For SUV, the within-subject coefficient of variation (wCV) appeared higher for PET/CT (8.5%-12.8%) than PET/MRI (6.6%-8.7%) across all PET reconstructions, though with no significant repeatability differences (all values ≥ 0.08) between modalities. For lean body mass-adjusted SUV, the wCVs appeared similar for PET/CT (9.9%-11.5%) and PET/MRI (9.2%-11.3%) across all PET reconstructions, again with no significant repeatability differences (all values ≥ 0.14) between modalities. For PET/MRI, the wCV for ADC of 3.5% appeared lower than the wCVs for SUV (6.6%-8.7%) and SUL (9.2%-11.3%), though without significant repeatability differences (all values ≥ 0.23). For solid tumors of the pelvis, the repeatability of the evaluated SUV and ADC metrics on F-FDG PET/MRI is both acceptably high and similar to previously published values for F-FDG PET/CT and MRI, supporting the use of F-FDG PET/MRI for quantitative oncologic treatment response assessments.
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http://dx.doi.org/10.2967/jnumed.118.218735DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6681694PMC
August 2019

Giant Defect-Induced Effects on Nanoscale Charge Separation in Semiconductor Photocatalysts.

Nano Lett 2019 01 28;19(1):426-432. Epub 2018 Dec 28.

State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, The Collaborative Innovation Centre of Chemistry for Energy Materials ( iChEM) , Dalian Institute of Chemical Physics , Chinese Academy of Sciences, Zhongshan Road 457 , Dalian 116023 , China.

Defects can markedly impact the performance of semiconductor-based photocatalysts, where the spatial separation of photogenerated charges is required for converting solar energy into fuels. However, understanding exactly how defects affect photogenerated charge separation at nanometer scale remains quite challenging. Here, using time- and space-resolved surface photovoltage approaches, we demonstrate that the distribution of surface photogenerated charges and the direction of photogenerated charge separation are determined by the defects distributed within a 100 nm surface region of a photocatalytic CuO particle. This is enabled by the defect-induced charge separation process, arising from the trapping of electrons at the near-surface defect states and the accumulation of holes at the surface states. More importantly, the driving force for defect-induced charge separation is greater than 4.2 kV/cm and can be used to drive photocatalytic reactions. These findings highlight the importance of near-surface defect engineering in promoting photogenerated charge separation and manipulating surface photogenerated charges; further, they open up a powerful avenue for improving photocatalytic charge separation and solar energy conversion efficiency.
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http://dx.doi.org/10.1021/acs.nanolett.8b04245DOI Listing
January 2019
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