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  • 1
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    Online Resource
    Segmentation of the Aorta and Pulmonary Arteries Based on 4D Flow MRI in the Pediatric Setting Using Fully Automated Multi‐Site, Multi‐Vendor, and Multi‐Label Dense U‐Net
    Wiley ; 2022
    In:  Journal of Magnetic Resonance Imaging Vol. 55, No. 6 ( 2022-06), p. 1666-1680
    Details
    In: Journal of Magnetic Resonance Imaging, Wiley, Vol. 55, No. 6 ( 2022-06), p. 1666-1680
    Abstract: Automated segmentation using convolutional neural networks (CNNs) have been developed using four‐dimensional (4D) flow magnetic resonance imaging (MRI). To broaden usability for congenital heart disease (CHD), training with multi‐institution data is necessary. However, the performance impact of heterogeneous multi‐site and multi‐vendor data on CNNs is unclear. Purpose To investigate multi‐site CNN segmentation of 4D flow MRI for pediatric blood flow measurement. Study Type Retrospective. Population A total of 174 subjects across two sites (female: 46%; N = 38 healthy controls, N = 136 CHD patients). Participants from site 1 (N = 100), site 2 (N = 74), and both sites (N = 174) were divided into subgroups to conduct 10‐fold cross validation (10% for testing, 90% for training). Field Strength/Sequence 3 T/1.5 T; retrospectively gated gradient recalled echo‐based 4D flow MRI. Assessment Accuracy of the 3D CNN segmentations trained on data from single site (single‐site CNNs) and data across both sites (multi‐site CNN) were evaluated by geometrical similarity (Dice score, human segmentation as ground truth) and net flow quantification at the ascending aorta (Qs), main pulmonary artery (Qp), and their balance (Qp/Qs), between human observers, single‐site and multi‐site CNNs. Statistical Tests Kruskal–Wallis test, Wilcoxon rank‐sum test, and Bland–Altman analysis. A P‐ value 〈 0.05 was considered statistically significant. Results No difference existed between single‐site and multi‐site CNNs for geometrical similarity in the aorta by Dice score (site 1: 0.916 vs. 0.915, P  = 0.55; site 2: 0.906 vs. 0.904, P  = 0.69) and for the pulmonary arteries (site 1: 0.894 vs. 0.895, P  = 0.64; site 2: 0.870 vs. 0.869, P  = 0.96). Qs site‐1 medians were 51.0–51.3 mL/cycle ( P  = 0.81) and site‐2 medians were 66.7–69.4 mL/cycle ( P  = 0.84). Qp site‐1 medians were 46.8–48.0 mL/cycle ( P  = 0.97) and site‐2 medians were 76.0–77.4 mL/cycle ( P  = 0.98). Qp/Qs site‐1 medians were 0.87–0.88 ( P  = 0.97) and site‐2 medians were 1.01–1.03 ( P  = 0.43). Bland–Altman analysis for flow quantification found equivalent performance. Data Conclusion Multi‐site CNN‐based segmentation and blood flow measurement are feasible for pediatric 4D flow MRI and maintain performance of single‐site CNNs. Level of Evidence 3 Technical Efficacy Stage 2
    Type of Medium: Online Resource
    ISSN: 1053-1807 , 1522-2586
    URL: Issue
    URL: Article
    DOI: 10.1002/jmri.v55.6
    DOI: 10.1002/jmri.27995
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 1497154-9
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  • 2
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    Reference Values for Fetal Cardiac Dimensions, Volumes, Ventricular Function and Left Ventricular Longitudinal Strain Using Doppler Ultrasound Gated Cardiac Magnetic Resonance Imaging in Healthy Third Trimester Fetuses
    Wiley ; 2024
    In:  Journal of Magnetic Resonance Imaging Vol. 60, No. 1 ( 2024-07), p. 365-374
    Details
    In: Journal of Magnetic Resonance Imaging, Wiley, Vol. 60, No. 1 ( 2024-07), p. 365-374
    Abstract: Recent advances in hardware and software permit the use of cardiac MRI of late gestation fetuses, however there is a paucity of MRI‐based reference values. Purpose To provide initial data on fetal cardiac MRI‐derived cardiac dimensions, volumes, ventricular function, and left ventricular longitudinal strain in healthy developing fetuses 〉 30 weeks gestational age. Study Type Prospective. Population Twenty‐five third trimester (34 ± 1 weeks, range of 32–37 weeks gestation) women with healthy developing fetuses. Field Strength/Sequence Studies were performed at 1.5 T and 3 T. Cardiac synchronization was achieved with a Doppler ultrasound device. The protocol included T2 single shot turbo spin echo stacks for fetal weight and ultrasound probe positioning, and multiplanar multi‐slice cine balanced steady state free precession gradient echo sequences. Assessment Primary analyses were performed by a single observer. Weight indexed right ventricular (RV) and left ventricular (LV) volumes and function were calculated from short axis (SAX) stacks. Cardiac dimensions were calculated from the four‐chamber and SAX stacks. Single plane LV longitudinal strain was calculated from the four‐chamber stack. Interobserver variability was assessed in 10 participants. Cardiac MRI values were compared against available published normative fetal echocardiogram data using z ‐scores. Statistical Tests Mean and SDs were calculated for baseline maternal/fetal demographics, cardiac dimensions, volumes, ventricular function, and left ventricular longitudinal strain. Bland–Altman and intraclass correlation coefficient analysis was performed to test interobserver variability. Results The mean gestational age was 34 ± 1.4 weeks. The mean RV and LV end diastolic volumes were 3.1 ± 0.6 mL/kg and 2.4 ± 0.5 mL/kg respectively. The mean RV cardiac output was 198 ± 49 mL/min/kg while the mean LV cardiac output was 173 ± 43 mL/min/kg. Data Conclusion This paper reports initial reference values obtained by cardiac MRI in healthy developing third trimester fetuses. MRI generally resulted in slightly larger indexed values (by z ‐score) compared to reports in literature using fetal echocardiography. Evidence level 1 Technical Efficacy Stage 2
    Type of Medium: Online Resource
    ISSN: 1053-1807 , 1522-2586
    URL: Issue
    URL: Article
    DOI: 10.1002/jmri.v60.1
    DOI: 10.1002/jmri.29077
    Language: English
    Publisher: Wiley
    Publication Date: 2024
    detail.hit.zdb_id: 1497154-9
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  • 3
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    Online Resource
    Calibrated bold fMRI with an optimized ASL-BOLD dual-acquisition sequence
    Elsevier BV ; 2016
    In:  NeuroImage Vol. 142 ( 2016-11), p. 474-482
    Details
    In: NeuroImage, Elsevier BV, Vol. 142 ( 2016-11), p. 474-482
    Type of Medium: Online Resource
    ISSN: 1053-8119
    URL: Article
    DOI: 10.1016/j.neuroimage.2016.08.007
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2016
    detail.hit.zdb_id: 1471418-8
    SSG: 5,2
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  • 4
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    Computed tomographic parenchymal lung findings in premature infants with pulmonary vein stenosis
    Springer Science and Business Media LLC ; 2023
    In:  Pediatric Radiology Vol. 53, No. 9 ( 2023-04-28), p. 1874-1884
    Details
    In: Pediatric Radiology, Springer Science and Business Media LLC, Vol. 53, No. 9 ( 2023-04-28), p. 1874-1884
    Type of Medium: Online Resource
    ISSN: 1432-1998
    URL: Article
    DOI: 10.1007/s00247-023-05673-y
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 1463007-2
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  • 5
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    Exercise Training Increases Resting Calf Muscle Oxygen Metabolism in Patients with Peripheral Artery Disease
    MDPI AG ; 2021
    In:  Metabolites Vol. 11, No. 12 ( 2021-11-29), p. 814-
    Details
    In: Metabolites, MDPI AG, Vol. 11, No. 12 ( 2021-11-29), p. 814-
    Abstract: Exercise training can mitigate symptoms of claudication (walking-induced muscle pain) in patients with peripheral artery disease (PAD). One adaptive response enabling this improvement is enhanced muscle oxygen metabolism. To explore this issue, we used arterial-occlusion diffuse optical spectroscopy (AO-DOS) to measure the effects of exercise training on the metabolic rate of oxygen (MRO2) in resting calf muscle. Additionally, venous-occlusion DOS (VO-DOS) and frequency-domain DOS (FD-DOS) were used to measure muscle blood flow (F) and tissue oxygen saturation (StO2), and resting calf muscle oxygen extraction fraction (OEF) was calculated from MRO2, F, and blood hemoglobin. Lastly, the venous/arterial ratio (γ) of blood monitored by FD-DOS was calculated from OEF and StO2. PAD patients who experience claudication (n = 28) were randomly assigned to exercise and control groups. Patients in the exercise group received 3 months of supervised exercise training. Optical measurements were obtained at baseline and at 3 months in both groups. Resting MRO2, OEF, and F, respectively, increased by 30% (12%, 44%) (p 〈 0.001), 17% (6%, 45%) (p = 0.003), and 7% (0%, 16%) (p = 0.11), after exercise training (median (interquartile range)). The pre-exercise γ was 0.76 (0.61, 0.89); it decreased by 12% (35%, 6%) after exercise training (p = 0.011). Improvement in exercise performance was associated with a correlative increase in resting OEF (R = 0.45, p = 0.02).
    Type of Medium: Online Resource
    ISSN: 2218-1989
    URL: Article
    DOI: 10.3390/metabo11120814
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2662251-8
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  • 6
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    High Temporal Resolution MRI Quantification of Global Cerebral Metabolic Rate of Oxygen Consumption in Response to Apneic Challenge
    SAGE Publications ; 2013
    In:  Journal of Cerebral Blood Flow & Metabolism Vol. 33, No. 10 ( 2013-10), p. 1514-1522
    Details
    In: Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, Vol. 33, No. 10 ( 2013-10), p. 1514-1522
    Abstract: We present a technique for quantifying global cerebral metabolic rate of oxygen consumption (CMRO 2 ) in absolute physiologic units at 3-second temporal resolution and apply the technique to quantify the dynamic CMRO 2 response to volitional apnea. Temporal resolution of 3 seconds was achieved via a combination of view sharing and superior sagittal sinus-based estimation of total cerebral blood flow (tCBF) rather than tCBF measurement in the neck arteries. These modifications were first validated in three healthy adults and demonstrated to produce minimal errors in image-derived blood flow and venous oxygen saturation (S v O 2 ) values. The technique was then applied in 10 healthy adults during an apnea paradigm of three repeated 30-second breath-holds. Subject-averaged baseline tCBF, arteriovenous oxygen difference (AVO 2 D), and CMRO 2 were 48.6±7.0 mL/100 g per minute, 29.4 ± 3.4%HbO 2 , and 125.1±11.4 μmol/100 g per minute, respectively. Subject-averaged maximum changes in tCBF and AVO 2 D were 43.5±9.4% and − 32.1±5.7%, respectively, resulting in a small (6.0±3.5%) but statistically significant ( P = 0.00044, two-tailed t-test) increase in average end-apneic CMRO 2 . This method could be used to investigate neurometabolic-hemodynamic relationships in normal physiology, to better define the biophysical origins of the BOLD signal, and to quantify neurometabolic responsiveness in diseases of altered neurovascular reactivity.
    Type of Medium: Online Resource
    ISSN: 0271-678X , 1559-7016
    URL: Article
    DOI: 10.1038/jcbfm.2013.110
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2013
    detail.hit.zdb_id: 2039456-1
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  • 7
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    MRI evaluation of cerebrovascular reactivity in obstructive sleep apnea
    SAGE Publications ; 2020
    In:  Journal of Cerebral Blood Flow & Metabolism Vol. 40, No. 6 ( 2020-06), p. 1328-1337
    Details
    In: Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, Vol. 40, No. 6 ( 2020-06), p. 1328-1337
    Abstract: Obstructive sleep apnea (OSA) is characterized by intermittent obstruction of the airways during sleep. Cerebrovascular reactivity (CVR) is an index of cerebral vessels' ability to respond to a vasoactive stimulus, such as increased CO 2 . We hypothesized that OSA alters CVR, expressed as a breath-hold index (BHI) defined as the rate of change in CBF or BOLD signal during a controlled breath-hold stimulus mimicking spontaneous apneas by being both hypercapnic and hypoxic. In 37 OSA and 23 matched non sleep apnea (NSA) subjects, we obtained high temporal resolution CBF and BOLD MRI data before, during, and between five consecutive BH stimuli of 24 s, each averaged to yield a single BHI value. Greater BHI was observed in OSA relative to NSA as derived from whole-brain CBF (78.6 ± 29.6 vs. 60.0 ± 20.0 mL/min 2 /100 g, P = 0.010) as well as from flow velocity in the superior sagittal sinus (0.48 ± 0.18 vs. 0.36 ± 0.10 cm/s 2 , P = 0.014). Similarly, BOLD-based BHI was greater in OSA in whole brain (0.19 ± 0.08 vs. 0.15 ± 0.03%/s, P = 0.009), gray matter (0.22 ± 0.09 vs. 0.17 ± 0.03%/s, P = 0.011), and white matter (0.14 ± 0.06 vs. 0.10 ± 0.02%/s, P = 0.010). The greater CVR is not currently understood but may represent a compensatory mechanism of the brain to maintain oxygen supply during intermittent apneas.
    Type of Medium: Online Resource
    ISSN: 0271-678X , 1559-7016
    URL: Article
    DOI: 10.1177/0271678X19862182
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
    detail.hit.zdb_id: 2039456-1
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  • 8
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    Calibrated fMRI for dynamic mapping of CMRO 2 responses using MR-based measurements of whole-brain venous oxygen saturation
    SAGE Publications ; 2020
    In:  Journal of Cerebral Blood Flow & Metabolism Vol. 40, No. 7 ( 2020-07), p. 1501-1516
    Details
    In: Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, Vol. 40, No. 7 ( 2020-07), p. 1501-1516
    Abstract: Functional MRI (fMRI) can identify active foci in response to stimuli through BOLD signal fluctuations, which represent a complex interplay between blood flow and cerebral metabolic rate of oxygen (CMRO 2 ) changes. Calibrated fMRI can disentangle the underlying contributions, allowing quantification of the CMRO 2 response. Here, whole-brain venous oxygen saturation ( Y v ) was computed alongside ASL-measured CBF and BOLD-weighted data to derive the calibration constant, M, using the proposed Y v -based calibration. Data were collected from 10 subjects at 3T with a three-part interleaved sequence comprising background-suppressed 3D-pCASL, 2D BOLD-weighted, and single-slice dual-echo GRE (to measure Y v via susceptometry-based oximetry) acquisitions while subjects breathed normocapnic/normoxic, hyperoxic, and hypercapnic gases, and during a motor task. M was computed via Y v -based calibration from both hypercapnia and hyperoxia stimulus data, and results were compared to conventional hypercapnia or hyperoxia calibration methods. Mean M in gray matter did not significantly differ between calibration methods, ranging from 8.5 ± 2.8% (conventional hyperoxia calibration) to 11.7 ± 4.5% (Y v -based calibration in response to hyperoxia), with hypercapnia-based M values between ( p = 0.56). Relative CMRO 2 changes from finger tapping were computed from each M map. CMRO 2 increased by ∼20% in the motor cortex, and good agreement was observed between the conventional and proposed calibration methods.
    Type of Medium: Online Resource
    ISSN: 0271-678X , 1559-7016
    URL: Article
    DOI: 10.1177/0271678X19867276
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
    detail.hit.zdb_id: 2039456-1
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  • 9
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    Online Resource
    Effects of exercise training on calf muscle oxygen extraction and blood flow in patients with peripheral artery disease
    American Physiological Society ; 2017
    In:  Journal of Applied Physiology Vol. 123, No. 6 ( 2017-12-01), p. 1599-1609
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 123, No. 6 ( 2017-12-01), p. 1599-1609
    Abstract: We employed near-infrared optical techniques, diffuse correlation spectroscopy (DCS), and frequency-domain near-infrared spectroscopy (FD-NIRS) to test the hypothesis that supervised exercise training increases skeletal muscle microvascular blood flow and oxygen extraction in patients with peripheral artery disease (PAD) who experience claudication. PAD patients ( n = 64) were randomly assigned to exercise and control groups. Patients in the exercise group received 3 mo of supervised exercise training. Calf muscle blood flow and oxygen extraction were optically monitored before, during, and after performance of a graded treadmill protocol at baseline and at 3 mo in both groups. Additionally, measurements of the ankle-brachial index (ABI) and peak walking time (PWT) to maximal claudication were made during each patient visit. Supervised exercise training was found to increase the maximal calf muscle blood flow and oxygen extraction levels during treadmill exercise by 29% (13%, 50%) and 8% (1%, 12%), respectively [ P 〈 0.001; median (25th percentile, 75th percentile)]. These improvements across the exercise group population were significantly higher than corresponding changes in the control group ( P 〈 0.004). Exercise training also increased PWT by 49% (18%, 101%) ( P = 0.01). However, within statistical error, the ABI, resting calf muscle blood flow and oxygen extraction, and the recovery half-time for hemoglobin\myoglobin desaturation following cessation of maximal exercise were not altered by exercise training. The concurrent monitoring of both blood flow and oxygen extraction with the hybrid DCS/FD-NIRS instrument revealed enhanced muscle oxidative metabolism during physical activity from exercise training, which could be an underlying mechanism for the observed improvement in PWT. NEW & NOTEWORTHY We report on noninvasive optical measurements of skeletal muscle blood flow and oxygen extraction dynamics before/during/after treadmill exercise in peripheral artery disease patients who experience claudication. The measurements tracked the effects of a 3-mo supervised exercise training protocol and revealed that supervised exercise training improved patient ability to increase microvascular calf muscle blood flow and oxygen extraction during physical activity.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/japplphysiol.00585.2017
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2017
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 10
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    Online Resource
    Combined diffusion and strain tensor MRI reveals a heterogeneous, planar pattern of strain development during isometric muscle contraction
    American Physiological Society ; 2011
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 300, No. 5 ( 2011-05), p. R1079-R1090
    Details
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 300, No. 5 ( 2011-05), p. R1079-R1090
    Abstract: The purposes of this study were to create a three-dimensional representation of strain during isometric contraction in vivo and to interpret it with respect to the muscle fiber direction. Diffusion tensor MRI was used to measure the muscle fiber direction of the tibialis anterior (TA) muscle of seven healthy volunteers. Spatial-tagging MRI was used to measure linear strains in six directions during separate 50% maximal isometric contractions of the TA. The strain tensor (E) was computed in the TA's deep and superficial compartments and compared with the respective diffusion tensors. Diagonalization of E revealed a planar strain pattern, with one nonzero negative strain (ε N ) and one nonzero positive strain (ε P ); both strains were larger in magnitude ( P 〈 0.05) in the deep compartment [ε N = −40.4 ± 4.3%, ε P = 35.1 ± 3.5% (means ± SE)] than in the superficial compartment (ε N = −24.3 ± 3.9%, ε P = 6.3 ± 4.9%). The principal shortening direction deviated from the fiber direction by 24.0 ± 1.3° and 39.8 ± 6.1° in the deep and superficial compartments, respectively ( P 〈 0.05, deep vs. superficial). The deviation of the shortening direction from the fiber direction was due primarily to the lower angle of elevation of the shortening direction over the axial plane than that of the fiber direction. It is concluded that three-dimensional analyses of strain interpreted with respect to the fiber architecture are necessary to characterize skeletal muscle contraction in vivo. The deviation of the principal shortening direction from the fiber direction may relate to intramuscle variations in fiber length and pennation angle.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    URL: Article
    DOI: 10.1152/ajpregu.00474.2010
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2011
    detail.hit.zdb_id: 1477297-8
    SSG: 12
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