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  • 1
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    Three‐dimensional assessment of brain arterial compliance: Technical development, comparison with aortic pulse wave velocity, and age effect
    Wiley ; 2021
    In:  Magnetic Resonance in Medicine Vol. 86, No. 4 ( 2021-10), p. 1917-1928
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    In: Magnetic Resonance in Medicine, Wiley, Vol. 86, No. 4 ( 2021-10), p. 1917-1928
    Abstract: The ability to measure cerebral vascular compliance (VC) is important in the evaluation of vascular diseases. Additionally, quantification of arterial wall pulsation in the brain may be useful for understanding the driving force of the recently discovered glymphatic system. Our goal is to develop an MRI technique to measure VC and arterial wall pulsation in major intracranial vessels. Methods A total of 17 healthy subjects were studied on a 3T MRI system. The technique, called VaCom‐PCASL, uses pseudo‐continuous arterial spin labeling (PCASL) to obtain pure blood vessel signal, uses a 3D radial acquisition, and applies a golden‐angle radial sparse parallel (GRASP) algorithm for image reconstruction. The k‐space data were retrospectively sorted into different cardiac phases. The GRASP algorithm allows the reconstruction of 5D (three spatial dimensions, one control/label dimension, and one cardiac‐phase dimension) data simultaneously. The proposed technique was optimized in terms of reconstruction parameters and labeling duration. Intracranial VC was compared with aortic pulse wave velocity measured with phase‐contrast MRI. Age differences in VC were studied. Results The VaCom‐PCASL technique using 10 cardiac phases and GRASP sparsity constraints of λ label/control = 0.05 and λ cardiac = 0.05 provided the highest contrast‐to‐noise ratio. A labeling duration of 800 ms was found to yield signals comparable to those of longer duration ( P 〉 .2), whereas 400 ms yielded significant overestimation ( P 〈 .005). A significant correlation was observed between intracranial VC and aortic pulse wave velocity ( r = −0.73, P = .038, N = 8). Vascular compliance in the older group was lower than that in the younger group. Conclusion The VaCom‐PCASL‐MRI technique represents a promising approach for noninvasive assessment of arterial stiffness and pulsatility.
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Article
    DOI: 10.1002/mrm.28835
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1493786-4
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  • 2
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    Vessel‐specific quantification of neonatal cerebral venous oxygenation
    Wiley ; 2019
    In:  Magnetic Resonance in Medicine Vol. 82, No. 3 ( 2019-09), p. 1129-1139
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    In: Magnetic Resonance in Medicine, Wiley, Vol. 82, No. 3 ( 2019-09), p. 1129-1139
    Abstract: Noninvasive measurement of cerebral venous oxygenation (Y v ) in neonates is important in the assessment of brain oxygen extraction and consumption, and may be useful in characterizing brain development and neonatal brain diseases. This study aims to develop a rapid method for vessel‐specific measurement of Y v in neonates. Methods We developed a pulse sequence, named accelerated T 2 ‐relaxation‐under‐phase‐contrast (aTRUPC), which consists of velocity‐encoding phase‐contrast module to isolate pure blood signal, flow‐insensitive T 2 ‐preparation to quantify blood T 2 , and turbo‐field‐echo (TFE) scheme for rapid image acquisition, which is critical for neonatal MRI. A series of studies were conducted. First, the pulse sequence was optimized in terms of TFE factor, velocity encoding (VENC), and slice thickness for best sensitivity. Second, to account for the influence of TFE acquisition on T 2 quantification, simulation and experiments were conducted to establish the relationship between TFE‐T 2 and standard T 2 . Finally, the complete aTRUPC sequence was applied on a group of healthy neonates and normative Y v values were determined. Results Optimal parameters of aTRUPC in neonates were found to be a TFE factor of 15, VENC of 5 cm/s, and slice thickness of 10 mm. The TFE‐T 2 was on average 3.9% lower than standard T 2 . These two measures were strongly correlated (R 2 = 0.86); thus their difference can be accounted for by a correction equation, T 2,standard = 1.2002 × T 2,TFE − 10.6276. Neonatal Y v values in veins draining cortical brain and those draining central brain were 64.8 ± 2.9% and 70.2 ± 3.3%, respectively, with a significant difference (P =.02). Conclusion The aTRUPC MRI has the potential to provide vessel‐specific quantification of cerebral Y v in neonates.
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    URL: Article
    DOI: 10.1002/mrm.v82.3
    DOI: 10.1002/mrm.27788
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1493786-4
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  • 3
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    Fractional anisotropy from diffusion tensor imaging correlates with acute astrocyte and myelin swelling in neonatal swine models of excitotoxic and hypoxic‐ischemic brain injury
    Wiley ; 2021
    In:  Journal of Comparative Neurology
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    In: Journal of Comparative Neurology, Wiley
    Type of Medium: Online Resource
    ISSN: 0021-9967 , 1096-9861
    URL: Article
    DOI: 10.1002/cne.25121
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1474879-4
    SSG: 12
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  • 4
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    Cerebral oxygen extraction fraction MRI : Techniques and applications
    Wiley ; 2022
    In:  Magnetic Resonance in Medicine Vol. 88, No. 2 ( 2022-08), p. 575-600
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    In: Magnetic Resonance in Medicine, Wiley, Vol. 88, No. 2 ( 2022-08), p. 575-600
    Abstract: Click here for author‐reader discussions
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    URL: Article
    DOI: 10.1002/mrm.v88.2
    DOI: 10.1002/mrm.29272
    Language: English
    Publisher: Wiley
    Publication Date: 2022
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  • 5
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    Longitudinal changes in brain oxygen extraction fraction (OEF) in older adults: Relationship to markers of vascular and Alzheimer's pathology
    Wiley ; 2023
    In:  Alzheimer's & Dementia Vol. 19, No. 2 ( 2023-02), p. 569-577
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    In: Alzheimer's & Dementia, Wiley, Vol. 19, No. 2 ( 2023-02), p. 569-577
    Abstract: Oxygen extraction fraction (OEF) reflects the balance between oxygen delivery and consumption. We longitudinally measured OEF in older adults to examine the relationship with markers of Alzheimer's disease (AD) and vascular pathology. Methods One hundred thirty‐seven participants were studied at two time‐points at an interval of 2.16 years. OEF was measured using T 2 ‐relaxation‐under‐spin‐tagging (TRUST) magnetic resonance imaging (MRI). The association between OEF and vascular risks, white matter hyperintensities (WMH), cerebrospinal fluid (CSF) measures of amyloid beta (Aβ), total tau (t‐tau), and phosphorylated tau 181 (p‐tau181) was examined. Results OEF increased from baseline to follow‐up. The increase in OEF was more prominent in individuals with high vascular risks compared to those with low vascular risks, and was associated with progression of vascular risks and the growth in WMH volume. OEF change was not related to CSF markers of AD pathology or their progression. Discussion Longitudinal OEF change in older adults is primarily related to vascular pathology.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    URL: Article
    DOI: 10.1002/alz.v19.2
    DOI: 10.1002/alz.12727
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2201940-6
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  • 6
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    Normal variations in brain oxygen extraction fraction are partly attributed to differences in end-tidal CO 2
    SAGE Publications ; 2020
    In:  Journal of Cerebral Blood Flow & Metabolism Vol. 40, No. 7 ( 2020-07), p. 1492-1500
    Details
    In: Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, Vol. 40, No. 7 ( 2020-07), p. 1492-1500
    Abstract: Cerebral oxygen extraction fraction is an important physiological index of the brain’s oxygen consumption and supply and has been suggested to be a potential biomarker for a number of diseases such as stroke, Alzheimer’s disease, multiple sclerosis, sickle cell disease, and metabolic disorders. However, in order for oxygen extraction fraction to be a sensitive biomarker for personalized disease diagnosis, inter-subject variations in normal subjects must be minimized or accounted for, which will otherwise obscure its interpretation. Therefore, it is essential to investigate the physiological underpinnings of normal differences in oxygen extraction fraction. This work used two studies, one discovery study and one verification study, to examine the extent to which an individual’s end-tidal CO 2 can explain variations in oxygen extraction fraction. It was found that, across normal subjects, oxygen extraction fraction is inversely correlated with end-tidal CO 2 . Approximately 50% of the inter-subject variations in oxygen extraction fraction can be attributed to end-tidal CO 2 differences. In addition, oxygen extraction fraction was found to be positively associated with age and systolic blood pressure. By accounting for end-tidal CO 2 , age, and systolic blood pressure of the subjects, normal variations in oxygen extraction fraction can be reduced by 73%, which is expected to substantially enhance the utility of oxygen extraction fraction as a disease biomarker.
    Type of Medium: Online Resource
    ISSN: 0271-678X , 1559-7016
    URL: Article
    DOI: 10.1177/0271678X19867154
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
    detail.hit.zdb_id: 2039456-1
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  • 7
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    MR fingerprinting ASL: Sequence characterization and comparison with dynamic susceptibility contrast (DSC) MRI
    Wiley ; 2020
    In:  NMR in Biomedicine Vol. 33, No. 1 ( 2020-01)
    Details
    In: NMR in Biomedicine, Wiley, Vol. 33, No. 1 ( 2020-01)
    Abstract: MR Fingerprinting (MRF)‐based Arterial‐Spin‐Labeling (ASL) has the potential to measure multiple parameters such as cerebral blood flow (CBF), bolus arrival time (BAT), and tissue T 1 in a single scan. However, the previous reports have only demonstrated a proof‐of‐principle of the technique but have not examined the performance of the sequence in the context of key imaging parameters. Furthermore, there has not been a study to directly compare the technique to clinically used perfusion method of dynamic‐susceptibility‐contrast (DSC) MRI. The present report consists of two studies. In the first study ( N  = 8), we examined the dependence of MRF‐ASL sequence on TR time pattern. Ten different TR patterns with a range of temporal characteristics were examined by both simulations and experiments. The results revealed that there was a significance dependence of the sequence performance on TR pattern ( p   〈  0.001), although there was not a single pattern that provided dramatically improvements. Among the TR patterns tested, a sinusoidal pattern with a period of 125 TRs provided an overall best estimation in terms of spatial consistency. These experimental observations were consistent with those of numerical simulations. In the second study ( N  = 8), we compared MRF‐ASL results with those of DSC MRI. It was found that MRF‐ASL and DSC MRI provided highly comparable maps of cerebral blood flow (CBF) and bolus‐arrival‐time (BAT), with spatial correlation coefficients of 0.79 and 0.91, respectively. However, in terms of quantitative values, BAT obtained with MRF‐ASL was considerably lower than that from DSC ( p   〈  0.001), presumably because of the differences in tracer characteristics in terms of diffusible versus intravascular tracers. Test–retest assessment of MRF‐ASL MRI revealed that the spatial correlations of parametric maps were 0.997, 0.962, 0.746 and 0.863 for B 1 + , T 1 , CBF, and BAT, respectively. MRF‐ASL is a promising technique for assessing multiple perfusion parameters simultaneously without contrast agent.
    Type of Medium: Online Resource
    ISSN: 0952-3480 , 1099-1492
    URL: Issue
    URL: Article
    DOI: 10.1002/nbm.v33.1
    DOI: 10.1002/nbm.4202
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2002003-X
    detail.hit.zdb_id: 1000976-0
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  • 8
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    Characterization of MRI techniques to assess neonatal brain oxygenation and blood flow
    Wiley ; 2019
    In:  NMR in Biomedicine Vol. 32, No. 7 ( 2019-07)
    Details
    In: NMR in Biomedicine, Wiley, Vol. 32, No. 7 ( 2019-07)
    Abstract: There is increasing interest in applying physiological MRI in neonates, based on the premise that physiological parameters may provide an early biomarker of neonatal brain health and injury. Two commonly used techniques are oxygen extraction fraction (OEF) measurement using T 2 ‐relaxation‐under‐spin‐tagging (TRUST) MRI and cerebral blood flow measurement using phase‐contrast (PC) quantitative flow MRI, which collectively provide an assessment of the brain's oxygen consumption. However, prior research has only demonstrated proof of principle of these methods in neonates, without characterization or benchmarking of the techniques. This is because available time is limited in neonatal subjects, especially when scans are performed as add‐ons to clinical scans (typically less than 5 min). The work presented aims to examine the TRUST and PC MRI sequences systematically in normal neonates, through research‐dedicated scan sessions. A series of characterization and optimization studies were conducted in a total of 26 radiographically normal neonates on 3 T systems. Our results show that TRUST MRI at the superior sagittal sinus (SSS) provides an OEF measurement equivalent to that at the internal jugular vein ( r  = 0.80, n  = 10), yet with shorter scan time. Lower resolution provided better precision in the TRUST measurement ( p  = 0.001, n  = 9). Therefore, the preferred OEF measurement is to apply TRUST MRI at the SSS using a spatial resolution of 2.5 mm. For PC MRI, our results showed that non‐gated PC MRI yielded blood flow measurements comparable to those from the more time‐consuming gated approach in neonates ( r  = 0.89, n  = 7). It was also found that blood flow could be overestimated by 18% when imaging resolution is larger than 0.3 mm ( n  = 7). Therefore, non‐gated PC MRI with a spatial resolution of 0.3 mm is recommended for neonatal applications. In conclusion, this study verifies consistency of neonatal brain oxygenation and flow measurements across acquisition schemes and points to optimal strategies in parameter selection when using these sequences.
    Type of Medium: Online Resource
    ISSN: 0952-3480 , 1099-1492
    URL: Issue
    URL: Article
    DOI: 10.1002/nbm.v32.7
    DOI: 10.1002/nbm.4103
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2002003-X
    detail.hit.zdb_id: 1000976-0
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  • 9
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    Noncontrast assessment of blood–brain barrier permeability to water: Shorter acquisition, test–retest reproducibility, and comparison with contrast‐based method
    Wiley ; 2021
    In:  Magnetic Resonance in Medicine Vol. 86, No. 1 ( 2021-07), p. 143-156
    Details
    In: Magnetic Resonance in Medicine, Wiley, Vol. 86, No. 1 ( 2021-07), p. 143-156
    Abstract: Assessment of the blood–brain barrier (BBB) permeability without the need for contrast agent is desirable, and the ability to measure the permeability to small molecules such as water may further increase the sensitivity in detecting diseases. This study proposed a time‐efficient, noncontrast method to measure BBB permeability to water, evaluated its test–retest reproducibility, and compared it with a contrast agent–based method. Methods A single‐delay water extraction with phase‐contrast arterial spin tagging (WEPCAST) method was devised in which spatial profile of the signal along the superior sagittal sinus was used to estimate bolus arrival time, and the WEPCAST signal at the corresponding location was used to compute water extraction fraction, which was combined with global cerebral blood flow to estimate BBB permeability surface area product to water. The reliability of WEPCAST sequence was examined in terms of intrasession, intersession, and inter‐vendor (Philips [Ingenia, Best, the Netherlands] and Siemens [Prisma, Erlangen, Germany] ) reproducibility. Finally, we compared this new technique to a contrast agent–based method. Results Single‐delay WEPCAST reduced the scan duration from approximately 20 min to 5 min. Extract fraction values estimated from single‐delay WEPCAST showed good consistency with the multi‐delay method (R = 0.82, P = .004). Group‐averaged permeability surface area product values were found to be 137.5 ± 9.3 mL/100 g/min. Intrasession, intersession, and inter‐vendor coefficient of variation of the permeability surface area product values were 6.6 ± 4.5%, 6.9 ± 3.7%, and 8.9 ± 3.0%, respectively. Finally, permeability surface area product obtained from WEPCAST MRI showed a significant correlation with that from the contrast‐based method (R = .73, P = .02). Conclusion Single‐delay WEPCAST MRI can measure BBB permeability to water within 5 min with an intrasession, intersession, and inter‐vendor test–retest reproducibility of 6% to 9%. This method may provide a useful marker of BBB breakdown in clinical studies.
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    URL: Article
    DOI: 10.1002/mrm.v86.1
    DOI: 10.1002/mrm.28687
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1493786-4
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  • 10
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    Cross‐vendor harmonization of T 2 ‐relaxation‐under‐spin‐tagging (TRUST) MRI for the assessment of cerebral venous oxygenation
    Wiley ; 2018
    In:  Magnetic Resonance in Medicine Vol. 80, No. 3 ( 2018-09), p. 1125-1131
    Details
    In: Magnetic Resonance in Medicine, Wiley, Vol. 80, No. 3 ( 2018-09), p. 1125-1131
    Abstract: Cerebral venous oxygenation (Y v ) is an important physiological parameter and has potential clinical application in many brain diseases. T 2 ‐relaxation‐under‐spin‐tagging (TRUST) is a commonly used MRI method to measure Y v . Harmonization of this technique across MRI vendors is important for dissemination and multicenter studies of brain oxygenation and metabolism as a disease biomarker. Methods TRUST pulse sequence components and imaging parameters were carefully matched between two major MRI vendors, Philips and Siemens. Each subject ( N  = 10) was scanned on both scanners within a 2.5‐h period. On each scanner, the subject was scanned in two sessions to assess intersession reproducibility. A hyperoxia challenge was also included in both sessions and on both scanners to evaluate the sensitivity of the technique to Y v changes. Measured Y v values, confidence interval of Y v estimates ( ), as well as intrasession and intersession coefficient of variation (CoV) of Y v , were compared between the two scanners. Results Y v measured on the two vendors were highly compatible and strongly correlated ( R 2  = 0.957). Y v changes associated with hyperoxia challenge were significant on both scanners ( P   〈  0.001) and were also correlated across scanners ( P  = 0.007). Intrasession and intersession CoV of measured Y v were less than 3% and showed no difference between scanners. were less than 1% on both scanners and showed no difference between scanners when echo times were matched on the two scanners. Conclusion This work suggests that harmonized TRUST MRI can yield highly compatible Y v measurements across different vendors. Magn Reson Med 80:1125–1131, 2018. © 2018 International Society for Magnetic Resonance in Medicine.
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    URL: Article
    DOI: 10.1002/mrm.v80.3
    DOI: 10.1002/mrm.27080
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 1493786-4
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