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Ishida S, Fujiwara Y, Matta Y, Takei N, Kanamoto M, Kimura H, Tsujikawa T. Enhanced parameter estimation in multiparametric arterial spin labeling using artificial neural networks. Magn Reson Med 2024. [PMID: 38852172 DOI: 10.1002/mrm.30184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 05/16/2024] [Accepted: 05/17/2024] [Indexed: 06/11/2024]
Abstract
PURPOSE Multiparametric arterial spin labeling (MP-ASL) can quantify cerebral blood flow (CBF) and arterial cerebral blood volume (CBVa). However, its accuracy is compromised owing to its intrinsically low SNR, necessitating complex and time-consuming parameter estimation. Deep neural networks (DNNs) offer a solution to these limitations. Therefore, we aimed to develop simulation-based DNNs for MP-ASL and compared the performance of a supervised DNN (DNNSup), physics-informed unsupervised DNN (DNNUns), and the conventional lookup table method (LUT) using simulation and in vivo data. METHODS MP-ASL was performed twice during resting state and once during the breath-holding task. First, the accuracy and noise immunity were evaluated in the first resting state. Second, CBF and CBVa values were statistically compared between the first resting state and the breath-holding task using the Wilcoxon signed-rank test and Cliff's delta. Finally, reproducibility of the two resting states was assessed. RESULTS Simulation and first resting-state analyses demonstrated that DNNSup had higher accuracy, noise immunity, and a six-fold faster computation time than LUT. Furthermore, all methods detected task-induced CBF and CBVa elevations, with the effect size being larger with the DNNSup (CBF, p = 0.055, Δ = 0.286; CBVa, p = 0.008, Δ = 0.964) and DNNUns (CBF, p = 0.039, Δ = 0.286; CBVa, p = 0.008, Δ = 1.000) than that with LUT (CBF, p = 0.109, Δ = 0.214; CBVa, p = 0.008, Δ = 0.929). Moreover, all the methods exhibited comparable and satisfactory reproducibility. CONCLUSION DNNSup outperforms DNNUns and LUT with respect to estimation performance and computation time.
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Affiliation(s)
- Shota Ishida
- Department of Radiological Technology, Faculty of Medical Sciences, Kyoto College of Medical Science, Nantan, Japan
| | - Yasuhiro Fujiwara
- Department of Medical Image Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Yuki Matta
- Radiological Center, University of Fukui Hospital, Eiheiji, Japan
| | | | | | - Hirohiko Kimura
- Faculty of Medical Sciences, University of Fukui, Fukui, Japan
- Radiology Section, National Health Insurance Echizen-cho Ota Hospital, Echizen, Japan
| | - Tetsuya Tsujikawa
- Department of Radiology, Faculty of Medical Sciences, University of Fukui, Fukui, Japan
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Mahroo A, Buck MA, Huber J, Breutigam NJ, Mutsaerts HJMM, Craig M, Chappell M, Günther M. Robust Multi-TE ASL-Based Blood-Brain Barrier Integrity Measurements. Front Neurosci 2021; 15:719676. [PMID: 34924924 PMCID: PMC8678075 DOI: 10.3389/fnins.2021.719676] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 10/25/2021] [Indexed: 12/30/2022] Open
Abstract
Multiple echo-time arterial spin labelling (multi-TE ASL) offers estimation of blood–tissue exchange dynamics by probing the T2 relaxation of the labelled spins. In this study, we provide a recipe for robust assessment of exchange time (Texch) as a proxy measure of blood–brain barrier (BBB) integrity based on a test-retest analysis. This includes a novel scan protocol and an extension of the two-compartment model with an “intra-voxel transit time” (ITT) to address tissue transit effects. With the extended model, we intend to separate the underlying two distinct mechanisms of tissue transit and exchange. The performance of the extended model in comparison with the two-compartment model was evaluated in simulations. Multi-TE ASL sequence with two different bolus durations was used to acquire in vivo data (n = 10). Cerebral blood flow (CBF), arterial transit time (ATT) and Texch were fitted with the two models, and mean grey matter values were compared. Additionally, the extended model also extracted ITT parameter. The test-retest reliability of Texch was assessed for intra-session, inter-session and inter-visit pairs of measurements. Intra-class correlation coefficient (ICC) and within-subject coefficient of variance (CoV) for grey matter were computed to assess the precision of the method. Mean grey matter Texch and ITT values were found to be 227.9 ± 37.9 ms and 310.3 ± 52.9 ms, respectively. Texch estimated by the extended model was 32.6 ± 5.9% lower than the two-compartment model. A significant ICC was observed for all three measures of Texch reliability (P < 0.05). Texch intra-session CoV, inter-session CoV and inter-visit CoV were found to be 6.6%, 7.9%, and 8.4%, respectively. With the described improvements addressing intra-voxel transit effects, multi-TE ASL shows good reproducibility as a non-invasive measure of BBB permeability. These findings offer an encouraging step forward to apply this potential BBB permeability biomarker in clinical research.
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Affiliation(s)
- Amnah Mahroo
- MR Physics, Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany
| | - Mareike Alicja Buck
- MR Physics, Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany.,MR-Imaging and Spectroscopy, University of Bremen, Bremen, Germany
| | - Jörn Huber
- MR Physics, Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany
| | | | - Henk J M M Mutsaerts
- Department of Radiology and Nuclear Medicine, Amsterdam Neuroscience, Amsterdam University Medical Center, Amsterdam, Netherlands
| | - Martin Craig
- Mental Health and Clinical Neurosciences, School of Medicine, University of Nottingham, Nottingham, United Kingdom.,Sir Peter Mansfield Imaging Centre, School of Medicine, University of Nottingham, Nottingham, United Kingdom.,Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Michael Chappell
- Mental Health and Clinical Neurosciences, School of Medicine, University of Nottingham, Nottingham, United Kingdom.,Sir Peter Mansfield Imaging Centre, School of Medicine, University of Nottingham, Nottingham, United Kingdom.,Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Nottingham Biomedical Research Centre, Queens Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - Matthias Günther
- MR Physics, Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany.,MR-Imaging and Spectroscopy, University of Bremen, Bremen, Germany.,mediri GmbH, Heidelberg, Germany
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Ishida S, Kimura H, Takei N, Fujiwara Y, Matsuda T, Kanamoto M, Matta Y, Kosaka N, Kidoya E. Separating spin compartments in arterial spin labeling using delays alternating with nutation for tailored excitation (DANTE) pulse: A validation study using T 2 -relaxometry and application to arterial cerebral blood volume imaging. Magn Reson Med 2021; 87:1329-1345. [PMID: 34687085 DOI: 10.1002/mrm.29052] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 08/31/2021] [Accepted: 09/30/2021] [Indexed: 11/07/2022]
Abstract
PURPOSE To clarify the type of spin compartment in arterial spin labeling (ASL) that is eliminated by delays alternating with nutation for tailored excitation (DANTE) pulse using T2 -relaxometry, and to demonstrate the feasibility of arterial cerebral blood volume (CBVa ) imaging using DANTE-ASL in combination with a simplified two-compartment model. METHOD The DANTE and T2 -preparation modules were combined into a single ASL sequence. T2 values under the application of DANTE were determined to evaluate changes in T2 , along with the post-labeling delay (PLD) and the relationship between transit time without DANTE (TTnoVS ) and T2 . The reference tissue T2 (T2_ref ) was also obtained. Subsequently, the DANTE module was embedded into the Hadamard-encoded ASL. Cerebral blood flow (CBF) and CBVa were computed using two Hadamard-encoding datasets (with and without DANTE) in a rest and breath-holding (BH) task. RESULTS While T2 without DANTE (T2_noVS ) decreased as the PLD increased, T2 with DANTE (T2_DANTE ) was equivalent to T2_ref and did not change with the PLD. Although there was a significant positive correlation between TTnoVS and T2_noVS with short PLD, T2_DANTE was not correlated with TTnoVS nor PLD. Baseline CBVa values obtained at rest were 0.64 ± 0.12, 0.64 ± 0.11, and 0.58 ± 0.15 mL/100 g for anterior, middle, and posterior cerebral arteries, respectively. Significant CBF and CBVa elevations were observed in the BH task. CONCLUSION Microvascular compartment signals were eliminated from the total ASL signals by DANTE. CBVa can be measured using Hadamard-encoded DANTE-ASL in combination with a simplified two-compartment model.
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Affiliation(s)
- Shota Ishida
- Radiological Center, University of Fukui Hospital, Eiheiji, Fukui, Japan
| | - Hirohiko Kimura
- Department of Radiology, Faculty of Medical Sciences, University of Fukui, Eiheiji, Fukui, Japan
| | - Naoyuki Takei
- Global MR Applications and Workflow, GE Healthcare Japan, Hino, Tokyo, Japan
| | - Yasuhiro Fujiwara
- Department of Medical Image Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Tsuyoshi Matsuda
- Division of Ultra-high Field MRI, Institute for Biomedical Science, Iwate Medical University, Iwate, Japan
| | - Masayuki Kanamoto
- Radiological Center, University of Fukui Hospital, Eiheiji, Fukui, Japan
| | - Yuki Matta
- Radiological Center, University of Fukui Hospital, Eiheiji, Fukui, Japan
| | - Nobuyuki Kosaka
- Department of Radiology, Faculty of Medical Sciences, University of Fukui, Eiheiji, Fukui, Japan
| | - Eiji Kidoya
- Radiological Center, University of Fukui Hospital, Eiheiji, Fukui, Japan
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Chen X, Meng X, Zhu D, Zou X, Shen Y, Li Z, Peng J, Hu D. Hemodynamic study of unenhanced magnetic resonance angiography using spatial labeling with multiple inversion pulses sequence: a phantom study. Quant Imaging Med Surg 2021; 11:1828-1835. [PMID: 33936968 DOI: 10.21037/qims-20-633] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background This study sought to explore the functional relationship between displayed vascular length and blood suppression inversion time (BSP TI) and flow velocity in a phantom, and to provide a theoretical basis for quantitatively assessing vascular hemodynamic responses using unenhanced magnetic resonance angiography (MRA) and spatial labeling with multiple inversion pulses sequence (SLEEK). Methods A polyethylene catheter was laid in a long rectangular container filled with pork fat. The entrance of the catheter into the container was connected to a high-pressure syringe filled with normal saline. The high-pressure injector flow rates were set at 0.0, 0.2, 0.4, 0.8, 1.2, 1.6, 2.0, and 2.4 mL/s. SLEEK was performed 19 times for each flow rate with parameter BSP TI values of 50, 75, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, 1,000, 1,100, 1,200, 1,300, 1,400, 1,600, and 1,800 ms. Maximum intensity projection was employed to reconstruct all SLEEK original images to determine the measurements of the displayed vascular lengths. A regression analysis was undertaken to assess the relationship between the displayed vascular lengths and BSP TI values for each flow rate, and to assess the relationship between the displayed vascular lengths and flow rates at each BSP TI. Results The displayed vascular length had a linear relationship with BSP TI for each flow rate (P<0.05) (R2=0.754, 0.941, 0.988, 0.988, 0.977, 0.966, and 0.982 for flow rates of 0.0, 0.2, 0.4, 0.8, 1.2, 1.6, and 2.0 mL/s, respectively). The displayed vascular length also had a linear relationship with flow rate for each BSP TI value (P<0.05) (R2 =0.914, 0.912, 0.834, 0.989, 0.980, 0.996, 0.992, 0.960, 0.975, 0.979, 0.982, 0.981, 0.976, and 0.993 for BSP TI 50, 75, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, 1,000, and 1,100 ms, respectively). No significant linear relationship was found between displayed vascular length and flow rate when the BSP TI value was 1,200 ms (P>0.05). Conclusions Vascular displayed length has a linear relationship to BSP TI for flow ranges from 0.0 to 2.0 mL/s. Vascular displayed length has a linear relationship to flow rate for BSP TI values of 50 to 1,100 ms. Flow rate can be assessed in relation to vascular displayed length.
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Affiliation(s)
- Xiao Chen
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiaoyan Meng
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Di Zhu
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xianlun Zou
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yaqi Shen
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhen Li
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jian Peng
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Daoyu Hu
- Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Gregori-Pla C, Cotta G, Blanco I, Zirak P, Giovannella M, Mola A, Fortuna A, Durduran T, Mayos M. Cerebral vasoreactivity in response to a head-of-bed position change is altered in patients with moderate and severe obstructive sleep apnea. PLoS One 2018. [PMID: 29538409 PMCID: PMC5851619 DOI: 10.1371/journal.pone.0194204] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Motivation Obstructive sleep apnea (OSA) can impair cerebral vasoreactivity and is associated with an increased risk of cerebrovascular disease. Unfortunately, an easy-to-use, non-invasive, portable monitor of cerebral vasoreactivity does not exist. Therefore, we have evaluated the use of near-infrared diffuse correlation spectroscopy to measure the microvascular cerebral blood flow (CBF) response to a mild head-of-bed position change as a biomarker for the evaluation of cerebral vasoreactivity alteration due to chronic OSA. Furthermore, we have monitored the effect of two years of continuous positive airway pressure (CPAP) treatment on the cerebral vasoreactivity. Methodology CBF was measured at different head-of-bed position changes (supine to 30° to supine) in sixty-eight patients with OSA grouped according to severity (forty moderate to severe, twenty-eight mild) and in fourteen control subjects without OSA. A subgroup (n = 13) with severe OSA was measured again after two years of CPAP treatment. Results All patients and controls showed a similar CBF response after changing position from supine to 30° (p = 0.819), with a median (confidence interval) change of -17.5 (-10.3, -22.9)%. However, when being tilted back to the supine position, while the control group (p = 0.091) and the mild patients with OSA (p = 0.227) recovered to the initial baseline, patients with moderate and severe OSA did not recover to the baseline (9.8 (0.8, 12.9)%, p < 0.001) suggesting altered cerebral vasoreactivity. This alteration was correlated with OSA severity defined by the apnea-hypopnea index, and with mean nocturnal arterial oxygen saturation. The CBF response was normalized after two years of CPAP treatment upon follow-up measurements. Conclusion In conclusion, microvascular CBF response to a head-of-bed challenge measured by diffuse correlation spectroscopy suggests that moderate and severe patients with OSA have altered cerebral vasoreactivity related to OSA severity. This may normalize after two years of CPAP treatment.
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Affiliation(s)
- Clara Gregori-Pla
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels (Barcelona), Spain
- * E-mail:
| | - Gianluca Cotta
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels (Barcelona), Spain
| | - Igor Blanco
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels (Barcelona), Spain
| | - Peyman Zirak
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels (Barcelona), Spain
| | - Martina Giovannella
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels (Barcelona), Spain
| | - Anna Mola
- Department of Respiratory Medicine, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Ana Fortuna
- Department of Respiratory Medicine, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Turgut Durduran
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels (Barcelona), Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| | - Mercedes Mayos
- Department of Respiratory Medicine, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
- CIBER Enfermedades Respiratorias (CibeRes) (CB06/06), Madrid, Spain
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Hua J, Liu P, Kim T, Donahue M, Rane S, Chen JJ, Qin Q, Kim SG. MRI techniques to measure arterial and venous cerebral blood volume. Neuroimage 2018; 187:17-31. [PMID: 29458187 DOI: 10.1016/j.neuroimage.2018.02.027] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 02/12/2018] [Accepted: 02/14/2018] [Indexed: 12/14/2022] Open
Abstract
The measurement of cerebral blood volume (CBV) has been the topic of numerous neuroimaging studies. To date, however, most in vivo imaging approaches can only measure CBV summed over all types of blood vessels, including arterial, capillary and venous vessels in the microvasculature (i.e. total CBV or CBVtot). As different types of blood vessels have intrinsically different anatomy, function and physiology, the ability to quantify CBV in different segments of the microvascular tree may furnish information that is not obtainable from CBVtot, and may provide a more sensitive and specific measure for the underlying physiology. This review attempts to summarize major efforts in the development of MRI techniques to measure arterial (CBVa) and venous CBV (CBVv) separately. Advantages and disadvantages of each type of method are discussed. Applications of some of the methods in the investigation of flow-volume coupling in healthy brains, and in the detection of pathophysiological abnormalities in brain diseases such as arterial steno-occlusive disease, brain tumors, schizophrenia, Huntington's disease, Alzheimer's disease, and hypertension are demonstrated. We believe that the continual development of MRI approaches for the measurement of compartment-specific CBV will likely provide essential imaging tools for the advancement and refinement of our knowledge on the exquisite details of the microvasculature in healthy and diseased brains.
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Affiliation(s)
- Jun Hua
- Neurosection, Div. of MRI Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.
| | - Peiying Liu
- Neurosection, Div. of MRI Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Tae Kim
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Manus Donahue
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Swati Rane
- Radiology, University of Washington Medical Center, Seattle, WA, USA
| | - J Jean Chen
- Rotman Research Institute, Baycrest Centre, Canada; Department of Medical Biophysics, University of Toronto, Canada
| | - Qin Qin
- Neurosection, Div. of MRI Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Seong-Gi Kim
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea
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Hirschler L, Munting LP, Khmelinskii A, Teeuwisse WM, Suidgeest E, Warnking JM, van der Weerd L, Barbier EL, van Osch MJP. Transit time mapping in the mouse brain using time-encoded pCASL. NMR IN BIOMEDICINE 2018; 31:e3855. [PMID: 29160952 DOI: 10.1002/nbm.3855] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 09/11/2017] [Accepted: 10/02/2017] [Indexed: 06/07/2023]
Abstract
The cerebral blood flow (CBF) is a potential biomarker for neurological disease. However, the arterial transit time (ATT) of the labeled blood is known to potentially affect CBF quantification. Furthermore, ATT could be an interesting biomarker in itself, as it may reflect underlying macro- and microvascular pathologies. Currently, no optimized magnetic resonance imaging (MRI) sequence exists to measure ATT in mice. Recently, time-encoded labeling schemes have been implemented in rats and humans, enabling ATT mapping with higher signal-to-noise ratio (SNR) and shorter scan time than multi-delay arterial spin labeling (ASL). In this study, we show that time-encoded pseudo-continuous arterial spin labeling (te-pCASL) also enables transit time measurements in mice. As an optimal design that takes the fast blood flow in mice into account, time encoding with 11 sub-boli of 50 ms is proposed to accurately probe the inflow of labeled blood. For perfusion imaging, a separate, traditional pCASL scan was employed. From the six studied brain regions, the hippocampus showed the shortest ATT (169 ± 11 ms) and the auditory/visual cortex showed the longest (284 ± 16 ms). Furthermore, ATT was found to be preserved in old wild-type mice. In a mouse with an induced carotid artery occlusion, prolongation of ATT was shown. In conclusion, this study shows the successful implementation of te-pCASL in mice, making it possible, for the first time, to measure ATT in mice in a time-efficient manner.
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Affiliation(s)
- Lydiane Hirschler
- Université Grenoble Alpes, Grenoble Institut des Neurosciences, Grenoble, France
- Inserm, U1216, Grenoble, France
- Bruker Biospin, Ettlingen, Germany
- Department of Radiology, C. J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, the Netherlands
| | - Leon P Munting
- Department of Radiology, C. J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, the Netherlands
- Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
| | - Artem Khmelinskii
- Department of Radiology, Division of Image Processing, Leiden University Medical Center, Leiden, the Netherlands
- Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Wouter M Teeuwisse
- Department of Radiology, C. J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, the Netherlands
| | - Ernst Suidgeest
- Department of Radiology, C. J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, the Netherlands
| | - Jan M Warnking
- Université Grenoble Alpes, Grenoble Institut des Neurosciences, Grenoble, France
- Inserm, U1216, Grenoble, France
| | - Louise van der Weerd
- Department of Radiology, C. J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, the Netherlands
- Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
| | - Emmanuel L Barbier
- Université Grenoble Alpes, Grenoble Institut des Neurosciences, Grenoble, France
- Inserm, U1216, Grenoble, France
| | - Matthias J P van Osch
- Department of Radiology, C. J. Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, the Netherlands
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Debacker CS, Daoust A, Köhler S, Voiron J, Warnking JM, Barbier EL. Impact of tissue T 1 on perfusion measurement with arterial spin labeling. Magn Reson Med 2016; 77:1656-1664. [PMID: 27136322 DOI: 10.1002/mrm.26255] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 03/18/2016] [Accepted: 04/02/2016] [Indexed: 12/20/2022]
Abstract
PURPOSE Arterial spin labeling (ASL) may provide quantitative maps of cerebral blood flow (CBF). Because labeled water exchanges with tissue water, this study evaluates the influence of tissue T1 on CBF quantification using ASL. METHODS To locally modify T1 , a low dose of manganese (Mn) was intracerebrally injected in one hemisphere of 19 rats (cortex or striatum). Tissue T1 and CBF were mapped using inversion recovery and continuous ASL experiments at 4.7T. RESULTS Mn reduced the tissue T1 by more than 30% but had little impact on other tissue properties as assessed via dynamic susceptibility and diffusion MRI. Using a single-compartment model, the use of a single tissue T1 value yielded a mean relative ipsilateral (Mn-injected) to contralateral (noninjected) CBF difference of -34% in cortex and -22% in striatum tissue. With a T1 map, these values became -7% and +8%, respectively. CONCLUSION A low dose of Mn reduces the tissue T1 without modifying CBF. Heterogeneous T1 impacts the ASL estimate of CBF in a region-dependent way. In animals, and when T1 modifications exceed the accuracy with which the tissue T1 can be determined, an estimate of tissue T1 should be obtained when quantifying CBF with an ASL technique. Magn Reson Med 77:1656-1664, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Clément S Debacker
- INSERM U1216, Grenoble, France.,Université Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble, France.,Bruker BioSpin MRI, Ettligen, Germany
| | - Alexia Daoust
- INSERM U1216, Grenoble, France.,Université Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble, France
| | | | | | - Jan M Warnking
- INSERM U1216, Grenoble, France.,Université Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble, France
| | - Emmanuel L Barbier
- INSERM U1216, Grenoble, France.,Université Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, Grenoble, France
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9
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Zhang X, Ghariq E, Hartkamp NS, Webb AG, van Osch MJP. Fast cerebral flow territory mapping using vessel encoded dynamic arterial spin labeling (VE-DASL). Magn Reson Med 2015; 75:2041-9. [PMID: 26094586 DOI: 10.1002/mrm.25806] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 05/05/2015] [Accepted: 05/25/2015] [Indexed: 11/09/2022]
Abstract
PURPOSE Whole-brain territory mapping using planning-free vessel-encoded pseudocontinuous arterial-spin-labeling (VE-pCASL) takes approximately 5 min, which is frequently considered too long for standard clinical protocols. In this study, vessel-encoded dynamic-ASL (VE-DASL) is optimized to achieve fast (< 30 s) cerebral flow territory mapping, especially aimed for the acute setting. METHODS VE-DASL is based on the creation of a continuous stream of magnetically labeled or unlabeled blood with different encoding patterns for each feeding artery, whose inflow into the brain tissue is monitored continuously. This approach leads to unique signal fluctuation within each flow territory, enabling reconstruction of individual flow territories by means of clustering techniques followed by linear regression. RESULTS VE-DASL was implemented and validated both as single slice and whole-brain method. In vivo results showed reasonable agreement with the "gold-standard" reference maps obtained from VE-pCASL. The Dice similarity coefficient which represents the fractional overlap between VE-DASL and "gold-standard" VE-pCASL territories ranged from 83.4% to 87.7% for the right internal cerebral artery (RICA), 81.7% to 83.1% for the left internal cerebral artery (LICA) and 64.3% to 71.8% for the vertebral arteries. CONCLUSION VE-DASL has the potential to map the main flow territories with whole-brain coverage in a short scan duration (∼30 s).
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Affiliation(s)
- Xingxing Zhang
- Department of Radiology, C. J. Gorter Center for high field MRI, Leiden University Medical Center, Leiden, The Netherlands
| | - Eidrees Ghariq
- Department of Radiology, C. J. Gorter Center for high field MRI, Leiden University Medical Center, Leiden, The Netherlands
| | - Nolan S Hartkamp
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Andrew G Webb
- Department of Radiology, C. J. Gorter Center for high field MRI, Leiden University Medical Center, Leiden, The Netherlands
| | - Matthias J P van Osch
- Department of Radiology, C. J. Gorter Center for high field MRI, Leiden University Medical Center, Leiden, The Netherlands.,Leiden Institute of Brain and Cognition, Leiden, The Netherlands
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Simultaneous Imaging of CBF Change and BOLD with Saturation-Recovery-T1 Method. PLoS One 2015; 10:e0122563. [PMID: 25905715 PMCID: PMC4408048 DOI: 10.1371/journal.pone.0122563] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 02/23/2015] [Indexed: 11/19/2022] Open
Abstract
A neuroimaging technique based on the saturation-recovery (SR)-T1 MRI method was applied for simultaneously imaging blood oxygenation level dependence (BOLD) contrast and cerebral blood flow change (ΔCBF), which is determined by CBF-sensitive T1 relaxation rate change (ΔR1CBF). This technique was validated by quantitatively examining the relationships among ΔR1CBF, ΔCBF, BOLD and relative CBF change (rCBF), which was simultaneously measured by laser Doppler flowmetry under global ischemia and hypercapnia conditions, respectively, in the rat brain. It was found that during ischemia, BOLD decreased 23.1±2.8% in the cortical area; ΔR1CBF decreased 0.020±0.004s-1 corresponding to a ΔCBF decrease of 1.07±0.24 ml/g/min and 89.5±1.8% CBF reduction (n=5), resulting in a baseline CBF value (=1.18 ml/g/min) consistent with the literature reports. The CBF change quantification based on temperature corrected ΔR1CBF had a better accuracy than apparent R1 change (ΔR1app); nevertheless, ΔR1app without temperature correction still provides a good approximation for quantifying CBF change since perfusion dominates the evolution of the longitudinal relaxation rate (R1app). In contrast to the excellent consistency between ΔCBF and rCBF measured during and after ischemia, the BOLD change during the post-ischemia period was temporally disassociated with ΔCBF, indicating distinct CBF and BOLD responses. Similar results were also observed for the hypercapnia study. The overall results demonstrate that the SR-T1 MRI method is effective for noninvasive and quantitative imaging of both ΔCBF and BOLD associated with physiological and/or pathological changes.
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Roldan-Valadez E, Lopez-Mejia M. Current concepts on magnetic resonance imaging (MRI) perfusion-diffusion assessment in acute ischaemic stroke: a review & an update for the clinicians. Indian J Med Res 2015; 140:717-28. [PMID: 25758570 PMCID: PMC4365345 DOI: pmid/25758570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Recently, several medical societies published joint statements about imaging recommendations for acute stroke and transient ischaemic attack patients. In following with these published guidelines, we considered it appropriate to present a brief, practical and updated review of the most relevant concepts on the MRI assessment of acute stroke. Basic principles of the clinical interpretation of diffusion, perfusion, and MRI angiography (as part of a global MRI protocol) are discussed with accompanying images for each sequence. Brief comments on incidence and differential diagnosis are also included, together with limitations of the techniques and levels of evidence. The purpose of this article is to present knowledge that can be applied in day-to-day clinical practice in specialized stroke units or emergency rooms to attend patients with acute ischaemic stroke or transient ischaemic attack according to international standards.
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12
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Evaluation of cerebrovascular impedance and wave reflection in mouse by ultrasound. J Cereb Blood Flow Metab 2015; 35:521-6. [PMID: 25515209 PMCID: PMC4348395 DOI: 10.1038/jcbfm.2014.229] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 11/14/2014] [Accepted: 11/25/2014] [Indexed: 11/13/2022]
Abstract
Genetic and surgical mouse models are commonly used to study cerebrovascular disease, but their size makes invasive hemodynamic testing technically challenging. The purpose of this study was to demonstrate a noninvasive measurement of cerebrovascular impedance and wave reflection in mice using high-frequency ultrasound in the left common carotid artery (LCCA), and to examine whether microvascular changes associated with hypercapnia could be detected with such an approach. Ten mice (C57BL/6J) were studied using a high-frequency ultrasound system (40 MHz). Lumen area and blood flow waveforms were obtained from the LCCA and used to calculate pulse-wave velocity, input impedance, and reflection amplitude and transit time under both normocapnic and hypercapnic (5% CO2) ventilation. With hypercapnia, vascular resistance was observed to decrease by 87%±12%. Although the modulus of input impedance was unchanged with hypercapnia, a phase decrease indicative of increased total arterial compliance was observed at low harmonics together with an increased reflection coefficient in both the time (0.57±0.08 versus 0.68±0.08, P=0.04) and frequency domains (0.62±0.08 versus 0.73±0.06, P=0.02). Interestingly, the majority of LCCA blood flow was found to pass into the internal carotid artery (range=76% to 90%, N=3), suggesting that hemodynamic measurements in this vessel are a good metric for intracerebral reactivity in mouse.
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Jahanian H, Peltier S, Noll DC, Hernandez Garcia L. Arterial cerebral blood volume-weighted functional MRI using pseudocontinuous arterial spin tagging (AVAST). Magn Reson Med 2015; 73:1053-64. [PMID: 24753198 DOI: 10.1002/mrm.25220] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 02/14/2014] [Accepted: 02/25/2014] [Indexed: 02/03/2023]
Abstract
PURPOSE Neurovascular regulation, including responses to neural activation that give rise to the blood oxygenation level-dependent (BOLD) effect, occurs mainly at the arterial and arteriolar level. The purpose of this study is to develop a framework for fast imaging of arterial cerebral blood volume (aCBV) signal suitable for functional imaging studies. METHODS A variant of the pseudocontinuous arterial spin tagging technique was developed in order to achieve a contrast that depends on aCBV with little contamination from perfusion signal by taking advantage of the kinetics of the tag through the vasculature. This technique tailors the tagging duration and repetition time for each subject. The proposed technique, called AVAST, is compared empirically with BOLD imaging and standard (perfusion-weighted) arterial spin labeling (ASL) technique, in a motor-visual activation paradigm. RESULTS The average Z-scores in the activated area obtained over all the subjects were 4.25, 5.52, and 7.87 for standard ASL, AVAST, and BOLD techniques, respectively. The aCBV contrast obtained from AVAST provided 80% higher average signal-to-noise ratio and 95% higher average contrast-to-noise ratio compared with that of the standard ASL measurements. CONCLUSION AVAST exhibits improved activation detection sensitivity and temporal resolution over the standard ASL technique, in functional MRI experiments, while preserving its quantitative nature and statistical advantages. AVAST particularly could be useful in clinical studies of pathological conditions, longitudinal studies of cognitive function, and studies requiring sustained periods of the condition.
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Capron T, Troalen T, Cozzone PJ, Bernard M, Kober F. Cine-ASL: a steady-pulsed arterial spin labeling method for myocardial perfusion mapping in mice. Part II. Theoretical model and sensitivity optimization. Magn Reson Med 2012; 70:1399-408. [PMID: 23281063 DOI: 10.1002/mrm.24588] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 10/17/2012] [Accepted: 11/14/2012] [Indexed: 12/21/2022]
Abstract
In small rodent myocardial perfusion studies, the most widely used method is based on Look-Locker measurements of the magnetization recovery after FAIR preparation, which bears limitations regarding acquisition efficiency due to the pulsed arterial spin labeling nature of the sequence. To improve efficiency, this two-article set proposes a new steady-pulsed arterial spin labeling scheme using a cine readout incorporating one tagging pulse per heart cycle. In this part, we derive a theoretical description of the magnetization time evolution in such a scheme. The combination of steady-pulsed labeling and cine readout drives tissue magnetization into a stationary regime that explicitly depends on perfusion. In comparison with dedicated experiments on the mouse heart, the model is discussed and validated for perfusion quantification. The model predicts that in this regime, signal is independent of irregular dynamics occurring during acquisition, such as heart rate variations or arterial input function. Optimization of the sequence offers the possibility to increase the signal to noise ratio by efficient signal averaging. The sensitivity of this new method is shown to be more than three times larger than previously used techniques.
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Affiliation(s)
- Thibaut Capron
- Centre de Résonance Magnétique Biologique et Médicale (CRMBM), UMR CNRS N°7339, Faculté de Médecine, Aix-Marseille Université, Marseille, France
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McGehee BE, Pollock JM, Maldjian JA. Brain perfusion imaging: How does it work and what should I use? J Magn Reson Imaging 2012; 36:1257-72. [DOI: 10.1002/jmri.23645] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Accepted: 02/17/2012] [Indexed: 11/09/2022] Open
Affiliation(s)
- Blake E. McGehee
- Department of Radiology, Wake Forest University School of Medicine, Winston‐Salem, North Carolina, USA
| | - Jeffrey M. Pollock
- Department of Radiology, Oregon Health and Science University, Portland, Oregon, USA
| | - Joseph A. Maldjian
- Department of Radiology, Wake Forest University School of Medicine, Winston‐Salem, North Carolina, USA
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Koretsky AP. Early development of arterial spin labeling to measure regional brain blood flow by MRI. Neuroimage 2012; 62:602-7. [PMID: 22245338 DOI: 10.1016/j.neuroimage.2012.01.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 11/16/2011] [Accepted: 01/01/2012] [Indexed: 12/31/2022] Open
Abstract
Two major avenues of work converged in the late 1980's and early 1990's to give rise to brain perfusion MRI. The development of anatomical brain MRI quickly had as a major goal the generation of angiograms using tricks to label flowing blood in macroscopic vessels. These ideas were aimed at getting information about microcirculatory flow as well. Over the same time course the development of in vivo magnetic resonance spectroscopy had as its primary goal the assessment of tissue function and in particular, tissue energetics. For this the measurement of the delivery of water to tissue was critical for assessing tissue oxygenation and viability. The measurement of the washin/washout of "freely" diffusible tracers by spectroscopic based techniques pointed the way for quantitative approaches to measure regional blood flow by MRI. These two avenues came together in the development of arterial spin labeling (ASL) MRI techniques to measure regional cerebral blood flow. The early use of ASL to measure brain activation to help verify BOLD fMRI led to a rapid development of ASL based perfusion MRI. Today development and applications of regional brain blood flow measurements with ASL continues to be a major area of activity.
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Affiliation(s)
- Alan P Koretsky
- Laboratory of Functional and Molecular Imaging, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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17
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Meng Y, Wang P, Kim SG. Simultaneous measurement of cerebral blood flow and transit time with turbo dynamic arterial spin labeling (Turbo-DASL): application to functional studies. Magn Reson Med 2011; 68:762-71. [PMID: 22162211 DOI: 10.1002/mrm.23294] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Revised: 09/21/2011] [Accepted: 10/17/2011] [Indexed: 01/08/2023]
Abstract
A turbo dynamic arterial spin labeling method (Turbo-DASL) was developed to simultaneously measure cerebral blood flow (CBF) and blood transit time with high temporal resolution. With Turbo-DASL, images were repeatedly acquired with a spiral readout after small-angle excitations during pseudocontinuous arterial spin labeling and control periods. Turbo-DASL experiments at 9.4 T without and with diffusion gradients were performed on rats anesthetized with isoflurane or α-chloralose. We determined blood transit times from carotid arteries to cortical arterial vessels (TT(a) ) from data obtained without diffusion gradients and to capillaries (TT(c) ) from data obtained with diffusion gradients. Cerebral arterial blood volume (CBV(a) ) was also calculated. At the baseline condition, both CBF and CBV(a) in the somatosensory cortical area were 40-50% less in rats with α-chloralose than in rats with isoflurane, while TT(a) and TT(c) were similar for both anesthetics. Absolute CBF and CBV(a) were positively correlated, while CBF and TT(c) were slightly negatively correlated. During forepaw stimulation, CBF increase was 15 ± 3% (n = 7) vs. 60 ± 7% (n = 5), and CBV(a) increase was 19 ± 9% vs. 46 ± 17% under isoflurane vs. α-chloralose anesthesia, respectively; CBF vs. CBV(a) changes were highly correlated. However, TT(a) and TT(c) were not significantly changed during stimulation. Our results support that arterial CBV increase plays a major role in functional CBF changes.
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Affiliation(s)
- Yuguang Meng
- Neuroimaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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18
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Hua J, Qin Q, Pekar JJ, van Zijl PCM. Measurement of absolute arterial cerebral blood volume in human brain without using a contrast agent. NMR IN BIOMEDICINE 2011; 24:1313-25. [PMID: 21608057 PMCID: PMC3192228 DOI: 10.1002/nbm.1693] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Revised: 11/26/2010] [Accepted: 01/19/2011] [Indexed: 05/26/2023]
Abstract
Arterial cerebral blood volume (CBV(a) ) is a vital indicator of tissue perfusion and vascular reactivity. We extended the recently developed inflow vascular-space-occupancy (iVASO) MRI technique, which uses spatially selective inversion to suppress the signal from blood flowing into a slice, with a control scan to measure absolute CBV(a) using cerebrospinal fluid (CSF) for signal normalization. Images were acquired at multiple blood nulling times to account for the heterogeneity of arterial transit times across the brain, from which both CBV(a) and arterial transit times were quantified. Arteriolar CBV(a) was determined separately by incorporating velocity-dependent bipolar crusher gradients. Gray matter (GM) CBV(a) values (n=11) were 2.04 ± 0.27 and 0.76 ± 0.17 ml blood/100 ml tissue without and with crusher gradients (b=1.8 s/mm(2) ), respectively. Arterial transit times were 671 ± 43 and 785 ± 69 ms, respectively. The arterial origin of the signal was validated by measuring its T(2) , which was within the arterial range. The proposed approach does not require exogenous contrast agent administration, and provides a non-invasive alternative to existing blood volume techniques for mapping absolute CBV(a) in studies of brain physiology and neurovascular diseases.
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Affiliation(s)
- Jun Hua
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD USA
- F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD USA
| | - Qin Qin
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD USA
- F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD USA
| | - James J. Pekar
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD USA
- F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD USA
| | - Peter C. M. van Zijl
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, MD USA
- F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD USA
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Taei-Tehrani MR, Van Osch MJP, Brown TR. Pseudo-random arterial modulation (PRAM): a novel arterial spin labeling approach to measure flow and blood transit times. J Magn Reson Imaging 2011; 35:223-8. [PMID: 21990142 DOI: 10.1002/jmri.22844] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 09/21/2011] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To investigate blood flow and transit time measurement, using the pseudo-random arterial modulation (PRAM). MATERIALS AND METHODS PRAM is based on a pseudo-random sequence of inversions and noninversions of the arterial blood at a labeling plane inferior to the imaging plane. To accomplish this, a pseudo-continuous tagging is used to create inversion or noninversion prepulses before a gradient echo sequence and tested on phantoms and human volunteers. RESULTS We have shown here that the PRAM technique can measure the velocity profile and the transit time accurately and efficiently both in a phantom and in vivo in a human brain. CONCLUSION PRAM does not require separate control and label acquisition as is common in arterial spin labeling (ASL) but rather measures the distribution of transit times to a voxel within one integrated scan. The PRAM method is a model-free approach in measuring transit time distributions, and therefore ultimately should provide more accurate perfusion measurements.
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Spatiotemporal evolution of the functional magnetic resonance imaging response to ultrashort stimuli. J Neurosci 2011; 31:1440-7. [PMID: 21273428 DOI: 10.1523/jneurosci.3986-10.2011] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The specificity of the hemodynamic response function (HRF) is determined spatially by the vascular architecture and temporally by the evolution of hemodynamic changes. The stimulus duration has additional influence on the spatiotemporal evolution of the HRF, as brief stimuli elicit responses that engage only the local vasculature, whereas long stimuli lead to the involvement of remote vascular supply and drainage. Here, we used functional magnetic resonance imaging to investigate the spatiotemporal evolution of the blood oxygenation level-dependent (BOLD), cerebral blood flow (CBF), and cerebral blood volume (CBV) HRF to ultrashort forelimb stimulation in an anesthetized rodent model. The HRFs to a single 333-μs-long stimulus were robustly detected and consisted of a rapid response in both CBF and CBV, with an onset time (OT) of 350 ms and a full width at half-maximum of 1 s. In contrast, longer stimuli elicited a dispersive transit of oxygenated blood across the cortical microvasculature that significantly prolonged the evolution of the CBV HRF, but not the CBF. The CBF and CBV OTs suggest that vasoactive messengers are synthesized, released, and effective within 350 ms. However, the difference between the BOLD and CBV OT (∼100 ms) was significantly smaller than the arteriolar-venular transit time (∼500 ms), indicating an arterial contribution to the BOLD HRF. Finally, the rapid rate of growth of the active region with stimulus elongation suggests that functional hyperemia is an integrative process that involves the entire functional cortical depth. These findings offer a new view into the spatiotemporal dynamics of functional hemodynamic regulation in the brain.
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Hua J, Qin Q, Donahue MJ, Zhou J, Pekar JJ, van Zijl PCM. Inflow-based vascular-space-occupancy (iVASO) MRI. Magn Reson Med 2011; 66:40-56. [PMID: 21695719 DOI: 10.1002/mrm.22775] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 11/03/2010] [Accepted: 11/24/2010] [Indexed: 01/24/2023]
Abstract
Vascular-space-occupancy (VASO) MRI, a blood nulling approach for assessing changes in cerebral blood volume (CBV), is hampered by low signal-to-noise ratio (SNR) because only 10-20% of tissue signal is recovered when using nonselective inversion for blood nulling. A new approach, called inflow-VASO (iVASO), is introduced in which only blood flowing into the slice has experienced inversion, thereby keeping tissue and cerebrospinal fluid (CSF) signal in the slice maximal and reducing CSF partial volume effects. SNR increases of 198% ± 12% and 334% ± 9% (mean ± SD, n = 7) with respect to VASO were found at TR values of 5 s and 2 s, respectively. When using inflow approaches, data interpretation is complicated by the fact that signal changes are affected by vascular transit times. An optimal TR-range (1.5-2.5 s) was derived in which the iVASO response during activation predominantly reflects arterial/arteriolar CBV (CBV(a)) changes. In this TR-range, perfusion contributions to the signal change are negligible because arterial label has not yet undergone capillary exchange, and arterial and precapillary blood signals are nulled. For TR = 2 s, the iVASO signal change upon visual stimulation corresponded to a CBV(a) increase of 58% ± 7%, in agreement with arteriolar CBV changes previously reported. The onset of the hemodynamic response for iVASO occurred 1.2 ± 0.5 s (n = 7) faster than for conventional VASO.
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Affiliation(s)
- Jun Hua
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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Wang Y, Kim SE, DiBella EVR, Parker DL. Flow measurement in MRI using arterial spin labeling with cumulative readout pulses--theory and validation. Med Phys 2011; 37:5801-10. [PMID: 21158292 DOI: 10.1118/1.3501881] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE This article systematically examines arterial spin labeling (ASL) as a flow quantification technique through theoretical simulation, in vitro, and in vivo experiment. The authors present a novel imaging pulse sequence design consisting of a single ASL magnetization preparation followed by Look-Locker-like image readouts. Bloch-equation-based modeling has been developed and validated using a hemodialyzer as a tissue-mimicking flow phantom. METHODS After the single in-plane slice-selective double inversion magnetization preparation, multiple TFL readouts are acquired with linear k-space ordering, causing a signal variation that depends on through-slice flow velocity. Computer simulations were performed to assess the behavior of the flow-dependent ASL signal as a function of varying imaging parameters. The signal was optimized by choosing imaging parameters that maximize the simulated flow-sensitive signal. Furthermore, a hemodialyzer which mimics blood flow in human tissues was tested with a wide range of flow rates. An exponential curve fitting of the flow-sensitive dynamics to the model derived from Bloch equations provides a method to estimate through-slice velocity for varying flow rates on the hemodialyzer and in vivo human brain. RESULTS The flow dependency of the ASL signal and the sensitivity of the ASL signal to imaging parameters were demonstrated. Experimental results from a hemodialyzer when fitted with a Bloch-equation-based model provide flow measurements that are consistent with ground truth velocities. Human brain velocity mapping was obtained as well. CONCLUSIONS The results provide evidence that the proposed pulse sequence design is an effective technique to measure total fluid flow through image voxels. The unique combination of the two main features, multiple-image readout after a single ASL preparation and linear acquisition ordering in the phase encoding direction in TFL imaging, make this technique an appealing flow imaging method to quantify through-plane flow in a time-efficient manner.
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Affiliation(s)
- Yi Wang
- Department of Bioengineering, University of Utah, 729 Arapeen Drive, Salt Lake City, Utah 84108, USA
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Durduran T, Choe R, Baker WB, Yodh AG. Diffuse Optics for Tissue Monitoring and Tomography. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2010; 73:076701. [PMID: 26120204 PMCID: PMC4482362 DOI: 10.1088/0034-4885/73/7/076701] [Citation(s) in RCA: 555] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
This review describes the diffusion model for light transport in tissues and the medical applications of diffuse light. Diffuse optics is particularly useful for measurement of tissue hemodynamics, wherein quantitative assessment of oxy- and deoxy-hemoglobin concentrations and blood flow are desired. The theoretical basis for near-infrared or diffuse optical spectroscopy (NIRS or DOS, respectively) is developed, and the basic elements of diffuse optical tomography (DOT) are outlined. We also discuss diffuse correlation spectroscopy (DCS), a technique whereby temporal correlation functions of diffusing light are transported through tissue and are used to measure blood flow. Essential instrumentation is described, and representative brain and breast functional imaging and monitoring results illustrate the workings of these new tissue diagnostics.
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Affiliation(s)
- T Durduran
- ICFO- Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain
| | - R Choe
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - W B Baker
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - A G Yodh
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
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MacIntosh BJ, Filippini N, Chappell MA, Woolrich MW, Mackay CE, Jezzard P. Assessment of arterial arrival times derived from multiple inversion time pulsed arterial spin labeling MRI. Magn Reson Med 2010; 63:641-7. [PMID: 20146233 DOI: 10.1002/mrm.22256] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The purpose of this study was to establish a normal range for the arterial arrival time (AAT) in whole-brain pulsed arterial spin labeling (PASL) cerebral perfusion MRI. Healthy volunteers (N = 36, range: 20 to 35 years) provided informed consent to participate in this study. AAT was assessed in multiple brain regions, using three-dimensional gradient and spin echo (GRASE) pulsed arterial spin labeling at 3.0 T, and found to be 641 +/- 95, 804 +/- 91, 802 +/- 126, and 935 +/- 108 ms in the temporal, parietal, frontal, and occipital lobes, respectively. Mean gray matter AAT was found to be 694 +/- 89 ms for females (N = 15), which was significantly shorter than for men, 814 +/- 192 ms (N = 21; P < 0.0003), and significant after correcting for brain volume (P < 0.001). Significant AAT sex differences were also found using voxelwise permutation testing. An atlas of AAT values across the healthy brain is presented here and may be useful for future experiments that aim to quantify cerebral blood flow from ASL data, as well as for clinical comparisons where disease pathology may lead to altered AAT. Pulsed arterial spin labeling signals were simulated using an identical sampling scheme as the empiric study and revealed AAT can be estimated robustly when simulated arrival times are well beyond the normal range.
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Affiliation(s)
- Bradley J MacIntosh
- FMRIB Centre, Department of Clinical Neurology, University of Oxford, John Radcliffe Hospital, Oxford, UK.
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Use of magnetic resonance imaging to predict outcome after stroke: a review of experimental and clinical evidence. J Cereb Blood Flow Metab 2010; 30:703-17. [PMID: 20087362 PMCID: PMC2949172 DOI: 10.1038/jcbfm.2010.5] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Despite promising results in preclinical stroke research, translation of experimental data into clinical therapy has been difficult. One reason is the heterogeneity of the disease with outcomes ranging from complete recovery to continued decline. A successful treatment in one situation may be ineffective, or even harmful, in another. To overcome this, treatment must be tailored according to the individual based on identification of the risk of damage and estimation of potential recovery. Neuroimaging, particularly magnetic resonance imaging (MRI), could be the tool for a rapid comprehensive assessment in acute stroke with the potential to guide treatment decisions for a better clinical outcome. This review describes current MRI techniques used to characterize stroke in a preclinical research setting, as well as in the clinic. Furthermore, we will discuss current developments and the future potential of neuroimaging for stroke outcome prediction.
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Pollock JM, Tan H, Kraft RA, Whitlow CT, Burdette JH, Maldjian JA. Arterial spin-labeled MR perfusion imaging: clinical applications. Magn Reson Imaging Clin N Am 2009; 17:315-38. [PMID: 19406361 DOI: 10.1016/j.mric.2009.01.008] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Arterial spin labeling (ASL) imaging soon will be available as a routine clinical perfusion imaging sequence for a significant number of MR imaging scanners. The ASL perfusion technique offers information similar to that provided by conventional dynamic susceptibility sequences, but it does not require the use of an intravenous contrast agent, and the data can be quantified. The appearance of pathology is affected significantly by the ASL techniques used. Familiarity with the available sequence parameter options and the common appearances of pathology facilitates perfusion interpretation.
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Affiliation(s)
- Jeffrey M Pollock
- Department of Radiology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
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A novel continuous arterial spin labeling approach for CBF measurement in rats with reduced labeling time and optimized signal-to-noise ratio efficiency. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2008; 22:135-42. [DOI: 10.1007/s10334-008-0157-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Revised: 11/12/2008] [Accepted: 11/12/2008] [Indexed: 11/25/2022]
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Dynamic magnetic resonance imaging of cerebral blood flow using arterial spin labeling. Methods Mol Biol 2008; 489:277-95. [PMID: 18839097 DOI: 10.1007/978-1-59745-543-5_13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Modern functional neuroimaging techniques, including positron emission tomography, optical imaging of intrinsic signals, and magnetic resonance imaging (MRI) rely on a tight coupling between neural activity and cerebral blood flow (CBF) to visualize brain activity using CBF as a surrogate marker. Because the spatial and temporal resolution of neuroimaging modalities is ultimately determined by the spatial and temporal specificity of the underlying hemodynamic signals, characterization of the spatial and temporal profiles of the hemodynamic response to focal brain stimulation is of paramount importance for the correct interpretation and quantification of functional data. The ability to properly measure and quantify CBF with MRI is a major determinant of progress in our understanding of brain function. We review the dynamic arterial spin labeling (DASL) method to measure CBF and the CBF functional response with high temporal resolution.
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Abstract
While nonenhanced magnetic resonance (MR) angiographic methods have been available since the earliest days of MR imaging, prolonged acquisition times and image artifacts have generally limited their use in favor of gadolinium-enhanced MR angiographic techniques. However, the combination of recent technical advances and new concerns about the safety of gadolinium-based contrast agents has spurred a resurgence of interest in methods that do not require exogenous contrast material. After a review of basic considerations in vascular imaging, the established methods for nonenhanced MR angiographic techniques, such as time of flight and phase contrast, are considered and their advantages and disadvantages are discussed. This article then focuses on new techniques that are becoming commercially available, such as electrocardiographically gated partial-Fourier fast spin-echo methods and balanced steady-state free precession imaging both with and without arterial spin labeling. Challenges facing these methods and possible solutions are considered. Since different imaging techniques rely on different mechanisms of image contrast, recommendations are offered for which strategies may work best for specific angiographic applications. Developments on the horizon include techniques that provide time-resolved imaging for assessment of flow dynamics by using nonenhanced approaches.
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Affiliation(s)
- Mitsue Miyazaki
- Department of MRI, Toshiba Medical Research Institute USA, 990 Corporate Woods Pkwy, Vernon Hills, IL 60061, USA.
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Matsumoto S, Hyodo F, Subramanian S, Devasahayam N, Munasinghe J, Hyodo E, Gadisetti C, Cook JA, Mitchell JB, Krishna MC. Low-field paramagnetic resonance imaging of tumor oxygenation and glycolytic activity in mice. J Clin Invest 2008; 118:1965-73. [PMID: 18431513 DOI: 10.1172/jci34928] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Accepted: 03/05/2008] [Indexed: 12/16/2022] Open
Abstract
A priori knowledge of spatial and temporal changes in partial pressure of oxygen (oxygenation; pO(2)) in solid tumors, a key prognostic factor in cancer treatment outcome, could greatly improve treatment planning in radiotherapy and chemotherapy. Pulsed electron paramagnetic resonance imaging (EPRI) provides quantitative 3D maps of tissue pO(2) in living objects. In this study, we implemented an EPRI set-up that could acquire pO(2) maps in almost real time for 2D and in minutes for 3D. We also designed a combined EPRI and MRI system that enabled generation of pO(2) maps with anatomic guidance. Using EPRI and an air/carbogen (95% O(2) plus 5% CO(2)) breathing cycle, we visualized perfusion-limited hypoxia in murine tumors. The relationship between tumor blood perfusion and pO(2) status was examined, and it was found that significant hypoxia existed even in regions that exhibited blood flow. In addition, high levels of lactate were identified even in normoxic tumor regions, suggesting the predominance of aerobic glycolysis in murine tumors. This report presents a rapid, noninvasive method to obtain quantitative maps of pO(2) in tumors, reported with anatomy, with precision. In addition, this method may also be useful for studying the relationship between pO(2) status and tumor-specific phenotypes such as aerobic glycolysis.
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Affiliation(s)
- Shingo Matsumoto
- Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland 20892-1002, USA
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Luo Z, Wang Z, Yuan Z, Du C, Pan Y. Optical coherence Doppler tomography quantifies laser speckle contrast imaging for blood flow imaging in the rat cerebral cortex. OPTICS LETTERS 2008; 33:1156-1158. [PMID: 18483544 DOI: 10.1364/ol.33.001156] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A dual-imaging modality is demonstrated for high-resolution quantitative imaging of local cerebral blood flow in the rat cortex by combining simultaneous spectral-domain Doppler optical coherence tomography (SDOCT) and full-field laser speckle contrast imaging (LSCI). Preliminary studies in tissue flow phantom and cocaine-induced cerebral blood flow changes indicated that by correlating coregistered cortical arterial blood flow, the relative measurement of flow changes by LSCI could be accurately calibrated by the absolute flow imaging provided by SDOCT (least square fit, r(2) approximately 0.96). Quantitative LSCI of cerebral blood flow is crucial to the quantitative analyses of the spatiotemporal hemodynamics of functional brain activations and thus improved understanding of neural process.
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Affiliation(s)
- Zhongchi Luo
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794-8181, USA
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32
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Francis ST, Bowtell R, Gowland PA. Modeling and optimization of Look-Locker spin labeling for measuring perfusion and transit time changes in activation studies taking into account arterial blood volume. Magn Reson Med 2008; 59:316-25. [PMID: 18183614 DOI: 10.1002/mrm.21442] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This work describes a new compartmental model with step-wise temporal analysis for a Look-Locker (LL)-flow-sensitive alternating inversion-recovery (FAIR) sequence, which combines the FAIR arterial spin labeling (ASL) scheme with a LL echo planar imaging (EPI) measurement, using a multireadout EPI sequence for simultaneous perfusion and T*(2) measurements. The new model highlights the importance of accounting for the transit time of blood through the arteriolar compartment, delta, in the quantification of perfusion. The signal expected is calculated in a step-wise manner to avoid discontinuities between different compartments. The optimal LL-FAIR pulse sequence timings for the measurement of perfusion with high signal-to-noise ratio (SNR), and high temporal resolution at 1.5, 3, and 7T are presented. LL-FAIR is shown to provide better SNR per unit time compared to standard FAIR. The sequence has been used experimentally for simultaneous monitoring of perfusion, transit time, and T*(2) changes in response to a visual stimulus in four subjects. It was found that perfusion increased by 83 +/- 4% on brain activation from a resting state value of 94 +/- 13 ml/100 g/min, while T*(2) increased by 3.5 +/- 0.5%.
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Affiliation(s)
- S T Francis
- Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, UK
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Hendrikse J, Petersen ET, van Laar PJ, Golay X. Cerebral Border Zones between Distal End Branches of Intracranial Arteries: MR Imaging. Radiology 2008; 246:572-80. [DOI: 10.1148/radiol.2461062100] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Brookes MJ, Morris PG, Gowland PA, Francis ST. Noninvasive measurement of arterial cerebral blood volume using Look-Locker EPI and arterial spin labeling. Magn Reson Med 2007; 58:41-54. [PMID: 17659615 DOI: 10.1002/mrm.21199] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This paper describes a method of noninvasively measuring regional arterial cerebral blood volume fractions (CBV(a)) in vivo using the combination of Look-Locker echo-planar imaging (LL-EPI) with arterial spin labeling (ASL). Using this technique the arterial inflow curve is rapidly sampled and the regional CBV(a) is measured, while tissue perfusion signals are suppressed. Two methods of spin labeling (LL-EPI flow-sensitive alternating inversion recovery (LL-EPI-FAIR) and LL-EPI signal targeting using alternating radiofrequency (LL-EPI-STAR)) are assessed and their advantages discussed. The application of vascular crushing to LL-EPI-FAIR is described and used to validate the insensitivity of the sequence to the perfusion difference signal. LL-EPI-STAR is used to assess changes in CBV(a) in response to a finger-tapping task. LL-EPI-STAR signal difference curves are shown to have a shortened vascular transit delay and increased peak signal change on activation. A 33 +/- 14% increase in CBV(a) on activation is found. CBV(a) is measured with a 6-s temporal resolution and the temporal response is compared with the BOLD signal change. CBV(a) is shown to increase more rapidly and return to baseline significantly faster than the BOLD signal change, which supports the suggestion that a change in CBV(a) is an input to the BOLD response.
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Affiliation(s)
- M J Brookes
- Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - P G Morris
- Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - P A Gowland
- Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - S T Francis
- Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK
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Wegener S, Wu WC, Perthen JE, Wong EC. Quantification of rodent cerebral blood flow (CBF) in normal and high flow states using pulsed arterial spin labeling magnetic resonance imaging. J Magn Reson Imaging 2007; 26:855-62. [PMID: 17896389 DOI: 10.1002/jmri.21045] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To implement a pulsed arterial spin labeling (ASL) technique in rats that accounts for cerebral blood flow (CBF) quantification errors due to arterial transit times (dt)-the time that tagged blood takes to reach the imaging slice-and outflow of the tag. MATERIALS AND METHODS Wistar rats were subjected to air or 5% CO(2), and flow-sensitive alternating inversion-recovery (FAIR) perfusion images were acquired. For CBF calculation, we applied the double-subtraction strategy (Buxton et al., Magn Reson Med 1998;40:383-396), in which data collected at two inversion times (TIs) are combined. RESULTS The ASL signal fell off more rapidly than expected from TI = one second onward, due to outflow effects. Inversion times for CBF calculation were therefore chosen to be larger than the longest transit times, but short enough to avoid systematic errors caused by outflow of tagged blood. Using our method, we observed a marked regional variability in CBF and dt, and a region dependent response to hypercapnia. CONCLUSION Even when flow is accelerated, CBF can be accurately determined using pulsed ASL, as long as dt and outflow of the tag are accounted for.
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Affiliation(s)
- Susanne Wegener
- Department of Radiology, University of California San Diego, San Diego, California, USA
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36
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Wintermark M, Sesay M, Barbier E, Borbély K, Dillon WP, Eastwood JD, Glenn TC, Grandin CB, Pedraza S, Soustiel JF, Nariai T, Zaharchuk G, Caillé JM, Dousset V, Yonas H. Comparative overview of brain perfusion imaging techniques. J Neuroradiol 2006; 32:294-314. [PMID: 16424829 DOI: 10.1016/s0150-9861(05)83159-1] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are: Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), Xenon-enhanced Computed Tomography (XeCT), Dynamic Perfusion-computed Tomography (PCT), Magnetic Resonance Imaging Dynamic Susceptibility Contrast (DSC), Arterial Spin-Labeling (ASL), and Doppler Ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow (CBF) or volume (CBV). All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview, established by consensus among specialists of the various techniques. For clinicians, this paper should offers a clearer picture of the pros and cons of currently available brain perfusion imaging techniques, and assist them in choosing the proper method in every specific clinical setting.
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Affiliation(s)
- M Wintermark
- Department of Radiology, Neuroradiology Section, University of California, 505 Parnassus Avenue, Room L358, Box 0628, San Francisco, CA 94143-0628, USA.
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37
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Petersen ET, Lim T, Golay X. Model-free arterial spin labeling quantification approach for perfusion MRI. Magn Reson Med 2006; 55:219-32. [PMID: 16416430 DOI: 10.1002/mrm.20784] [Citation(s) in RCA: 244] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In this work a model-free arterial spin labeling (ASL) quantification approach for measuring cerebral blood flow (CBF) and arterial blood volume (aBV) is proposed. The method is based on the acquisition of a train of multiple images following the labeling scheme. Perfusion is obtained using deconvolution in a manner similar to that of dynamic susceptibility contrast (DSC) MRI. Local arterial input functions (AIFs) can be estimated by subtracting two perfusion-weighted images acquired with and without crusher gradients, respectively. Furthermore, by knowing the duration of the bolus of tagged arterial blood, one can estimate the aBV on a voxel-by-voxel basis. The maximum of the residue function obtained from the deconvolution of the tissue curve by the AIF is a measure of CBF after scaling by the locally estimated aBV. This method provides averaged gray matter (GM) perfusion values of 38 +/- 2 ml/min/100 g and aBV of 0.93% +/- 0.06%. The average CBF value is 10% smaller than that obtained on the same data set using the standard general kinetic model (42 +/- 2 ml/min/100 g). Monte Carlo simulations were performed to compare this new methodology with parametric fitting by the conventional model.
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38
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Thomas DL, Lythgoe MF, van der Weerd L, Ordidge RJ, Gadian DG. Regional variation of cerebral blood flow and arterial transit time in the normal and hypoperfused rat brain measured using continuous arterial spin labeling MRI. J Cereb Blood Flow Metab 2006; 26:274-82. [PMID: 16034369 PMCID: PMC2702127 DOI: 10.1038/sj.jcbfm.9600185] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Continuous arterial spin labeling (CASL) is a noninvasive magnetic resonance (MR) method for measuring cerebral perfusion. In its most widely used form, CASL incorporates a postlabeling delay to minimize the sensitivity of the technique to transit time effects, which otherwise corrupt cerebral blood flow (CBF) quantification. For this delay to work effectively, it must be longer than the longest transit time present in the system. In this work, CASL measurements were made in four coronal slices in the rat brain using a range of postlabeling delays. By doing this, direct estimation of both CBF and arterial transit time (delta(a)) was possible. These measurements were performed in the normal brain and during hypoperfusion induced by occlusion of the common carotid arteries. It was found that, in the normal rat brain, significant regional variation exists for both CBF and delta(a). Mean values of CBF and delta(a) in the selected gray matter regions of interest were 233 mL/100 g min and 266 ms, respectively, with the latter ranging from 100 to 500 ms. Therefore, use of a 500-ms postlabeling delay is suitable for any location in the normal rat brain. After common carotid artery occlusion, CBF decreased and delta(a) increased by regionally dependent amounts. In the sensory cortex, delta(a) increased to a mean value of 740 ms, significantly greater than 500 ms. These results highlight the importance of either (a) determining delta(a) as part of the CASL measurement or (b) knowing the approximate range of values delta(a) is likely to take for a given application, so that the parameters of the CASL sequence can be chosen appropriately.
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Affiliation(s)
- David L Thomas
- RCS Unit of Biophysics, Institute of Child Health, University College London, London, UK.
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Abstract
Over the past dozen years, the use of MRI techniques to map brain function (fMRI) has sparked a great deal of research. The ability of fMRI to image several different physiological processes concurrently (i.e., blood oxygenation, blood flow, metabolism) and noninvasively over large volumes make it the ideal choice for many different areas of neuroscience research in addition to countless applications in clinical settings. Furthermore, with the advent of high magnetic fields (and other hardware advancements, i.e., parallel imaging) for both human and animal research, spatial and temporal resolutions continue to be pushed to higher levels because of increases in the sensitivity as well as specificity of MR-detectable functional signals. fMRI methodology continues to grow and has the ability to cater to many different research applications. There seems to be no foreseeable end in sight to the advancement of fMRI techniques and its subsequent use in basic research as well as in clinical settings. In this work, fMRI techniques and the ongoing development of existing techniques are discussed with implications for the future of fMRI.
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Affiliation(s)
- Noam Harel
- Center for Magnetic Resonance Research (CMRR), Department of Radiology, University of Minnesota, Minneapolis, Minnesota, USA
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Kim T, Kim SG. Quantification of cerebral arterial blood volume using arterial spin labeling with intravoxel incoherent motion-sensitive gradients. Magn Reson Med 2006; 55:1047-57. [PMID: 16596632 DOI: 10.1002/mrm.20867] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Quantification of cerebral arterial blood volume (CBVa) is important for understanding vascular regulation. To enable measurement of CBVa with diffusion-weighted (DW) arterial spin labeling (ASL), a theoretical framework was developed using the effects of intravoxel incoherent motion (IVIM). The pseudo-diffusion coefficient (D*) in the IVIM model was evaluated at 9.4 T in DW-ASL of rat brain under isoflurane anesthesia by variations of both post-labeling delay (w) and magnetization transfer ratio (MTR). D* and its volume fraction decreased at values of w>or=0.3 s, and the normalized apparent diffusion coefficient (ADC) increased with MTR, suggesting that D* is closely correlated with CBVa. Thus, the difference between ASL measurements with and without DW gradients is related to CBVa. The CBVa values measured by this approach were compared with values obtained using the modulation of tissue and vessel (MOTIVE) technique with ASL, which varies MT levels without changing spin labeling efficiency. CBVa values from both methods were highly correlated. The measured CBVa values were linearly correlated with cerebral blood flow (CBF) for a PaCO2 range of 25-50 mmHg; DeltaCBVa (ml/100 g)=0.007 (min-1)xDeltaCBF (ml/100 g/min). The DW-ASL approach is simple and easy to implement for human and animal CBVa studies.
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Affiliation(s)
- Tae Kim
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15203, USA
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41
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Kim T, Kim SG. Quantification of cerebral arterial blood volume and cerebral blood flow using MRI with modulation of tissue and vessel (MOTIVE) signals. Magn Reson Med 2005; 54:333-42. [PMID: 16032688 DOI: 10.1002/mrm.20550] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Regional cerebral arterial blood volume (CBVa) and blood flow (CBF) can be quantitatively measured by modulation of tissue and vessel (MOTIVE) signals, enabling separation of tissue signal from blood. Tissue signal is selectively modulated using magnetization transfer (MT) effects. Blood signal is changed either by injection of a contrast agent or by arterial spin labeling (ASL). The measured blood volume represents CBVa because the contribution from venous blood was insignificant in our measurements. Both CBVa and CBF were quantified in isoflurane-anesthetized rats at 9.4T. CBVa obtained using a contrast agent was 1.1 +/- 0.5 and 1.3 +/- 0.6 ml/100 g tissue (N = 10) in the cortex and caudate putamen, respectively. The CBVa values determined from ASL data were 1.0 +/- 0.3 ml/100 g (N = 10) in both the cortex and the caudate putamen. The match between CBVa values determined by both methods validates the MOTIVE approach. In ASL measurements, the overestimation in calculated CBF values increased with MT saturation levels due to the decreasing contribution from tissue signals, which was confirmed by the elimination of blood with a contrast agent. Using the MOTIVE approach, accurate CBF values can also be obtained.
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Affiliation(s)
- Tae Kim
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15203, USA
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Wintermark M, Sesay M, Barbier E, Borbély K, Dillon WP, Eastwood JD, Glenn TC, Grandin CB, Pedraza S, Soustiel JF, Nariai T, Zaharchuk G, Caillé JM, Dousset V, Yonas H. Comparative overview of brain perfusion imaging techniques. Stroke 2005; 36:e83-99. [PMID: 16100027 DOI: 10.1161/01.str.0000177884.72657.8b] [Citation(s) in RCA: 328] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are positron emission tomography, single photon emission computed tomography, Xenon-enhanced computed tomography, dynamic perfusion computed tomography, MRI dynamic susceptibility contrast, arterial spin labeling, and Doppler ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow or cerebral blood volume. All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. SUMMARY OF REVIEW This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview established by consensus among specialists of the various techniques. CONCLUSIONS For clinicians, this article should offer a clearer picture of the pros and cons of currently available brain perfusion imaging techniques and assist them in choosing the proper method for every specific clinical setting.
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Affiliation(s)
- Max Wintermark
- Department of Radiology, University of California, 505 Parnassus Ave, San Francisco, CA 94143-0628, USA.
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Li KL, Zhu X, Hylton N, Jahng GH, Weiner MW, Schuff N. Four-phase single-capillary stepwise model for kinetics in arterial spin labeling MRI. Magn Reson Med 2005; 53:511-8. [PMID: 15723393 PMCID: PMC1941668 DOI: 10.1002/mrm.20390] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
An extended model for extracting measures of brain perfusion from pulsed arterial spin labeling (ASL) data while considering transit effects and restricted permeability of capillaries to blood water is proposed. We divided the time course of the signal difference between control and labeled images into four phases with respect to the arrival time of labeled blood water at the voxel of interest (t(A)), transit time through the arteries in the voxel (t(ex)), and duration of the bolus of labeled spins (tau). Dividing the labeled slab of blood water into many discrete segments, and adapting numerical integration methods allowed us to conveniently model restricted capillary-tissue exchange based on a modified distributed parameter model. We compared this four-phase single-capillary stepwise (FPSCS) model with models that treat water as a freely diffusible tracer, using both simulations and experimental ASL brain imaging data at 1.5T from eight healthy subjects (24-80 years old). The FPSCS model yielded less errors in the least-squares sense in fitting brain ASL data in comparison with freely diffusible tracer models of water (P = 0.055). These results imply that restricted permeability of capillaries to water should be considered when brain ASL data are analyzed.
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Affiliation(s)
- Ka-loh Li
- Department of Radiology, University of California-San Francisco, and VA Medical Center 114M, 4150 Clement Street, San Francisco, CA 94121, USA
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Moffat BA, Chenevert TL, Hall DE, Rehemtulla A, Ross BD. Continuous arterial spin labeling using a train of adiabatic inversion pulses. J Magn Reson Imaging 2005; 21:290-6. [PMID: 15723380 DOI: 10.1002/jmri.20268] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To develop a simple and robust magnetic resonance imaging (MRI) pulse sequence for the quantitative measurement of blood flow in the brain and cerebral tumors that has practical implementation advantages over currently used continuous arterial spin labeling (CASL) schemes. MATERIALS AND METHODS Presented here is a single-coil protocol that uses a train of hyperbolic secant inversion pulses to produce continuous arterial spin inversion for perfusion weighting of fast spin echo images. Flow maps of normal rat brains and those containing a 9L gliosarcoma orthotopic tumor model conditions were acquired with and without carbogen. RESULTS The perfusion-weighted images have reduced magnetization transfer signal degradation as compared to the traditional single-coil CASL while avoiding the use of a more complex two-coil CASL technique. Blood flow measurements in tumor and normal brain tissue were consistent with those previously reported by other CASL techniques. Contralateral and normal brain showed increased blood flow with carbogen breathing, while tumor tissue lacked the same CO(2) reactivity. CONCLUSION This variation of the CASL technique is a quantitative, robust, and practical single-coil method for measuring blood flow. This CASL method does not require specialized radiofrequency coils or amplifiers that are not routinely used for anatomic imaging of the brain, therefore allowing these flow measurements to be easily incorporated into traditional rodent neuroimaging protocols.
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Affiliation(s)
- Bradford A Moffat
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
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Abstract
Arterial spin labeling is a magnetic resonance method for the measurement of cerebral blood flow. In its simplest form, the perfusion contrast in the images gathered by this technique comes from the subtraction of two successively acquired images: one with, and one without, proximal labeling of arterial water spins after a small delay time. Over the last decade, the method has moved from the experimental laboratory to the clinical environment. Furthermore, numerous improvements, ranging from new pulse sequence implementations to extensive theoretical studies, have broadened its reach and extended its potential applications. In this review, the multiple facets of this powerful yet difficult technique are discussed. Different implementations are compared, the theoretical background is summarized, and potential applications of various implementations in research as well as in the daily clinical routine are proposed. Finally, a summary of the new developments and emerging techniques in this field is provided.
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Affiliation(s)
- Xavier Golay
- Department of Neuroradiology, National Neuroscience Institute, Singapore.
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Uğurbil K, Adriany G, Andersen P, Chen W, Garwood M, Gruetter R, Henry PG, Kim SG, Lieu H, Tkac I, Vaughan T, Van De Moortele PF, Yacoub E, Zhu XH. Ultrahigh field magnetic resonance imaging and spectroscopy. Magn Reson Imaging 2003; 21:1263-81. [PMID: 14725934 DOI: 10.1016/j.mri.2003.08.027] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Kâmil Uğurbil
- Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
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Callot V, Bennett E, Decking UKM, Balaban RS, Wen H. In vivo study of microcirculation in canine myocardium using the IVIM method. Magn Reson Med 2003; 50:531-40. [PMID: 12939761 PMCID: PMC2881595 DOI: 10.1002/mrm.10568] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The intravoxel incoherent motion (IVIM) method was implemented in closed-chest dogs to obtain measurements on microcirculation in the left ventricular wall in vivo. Specifically, it enabled us to measure the mean microflow velocity (400 +/- 40 microm/s) and the vascular volume fraction (VVF) (11.1% +/- 2.2%), and observe the directional preference of capillary orientation. The apparent diffusion coefficients (ADCs) of water along and perpendicular to myofibers were also measured. With vasodilatation by adenosine infusion, a 25% increase in the VVF and a 7% increase in the mean microflow velocity were observed, while no change in the ADC was detected. A 28.5% decrease of the ADC was observed postmortem.
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Affiliation(s)
- Virginie Callot
- Laboratory of Cardiac Energetics, NHLBI, NIH, Bethesda, Maryland 20892, USA
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48
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Utting JF, Thomas DL, Gadian DG, Ordidge RJ. Velocity-driven adiabatic fast passage for arterial spin labeling: results from a computer model. Magn Reson Med 2003; 49:398-401. [PMID: 12541264 DOI: 10.1002/mrm.10363] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Velocity-driven adiabatic fast passage (AFP) is commonly employed for perfusion imaging by continuous arterial spin labeling (CASL). The degree of inversion of protons in blood determines the sensitivity of CASL to perfusion. For this study, a computer model of the modified Bloch equations was developed to establish the optimum conditions for velocity-driven AFP. Natural variations in blood velocity over the course of the cardiac cycle were found to result in significant variations in the degree of inversion. However, the mean degree of inversion was similar to that for blood moving at a constant velocity, equal to the time-averaged mean, at peak velocities and heart rates within normal ranges. A train of RF pulses instead of a continuous RF pulse for labeling was found to result in a highly nonlinear dependence of the degree of inversion on RF duty cycle. This may have serious implications for the quantification of perfusion.
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Affiliation(s)
- Jane F Utting
- Medical Physics and Bioengineering Department, University College London, London, UK
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Restrepo L, Wityk RJ, Grega MA, Borowicz L, Barker PB, Jacobs MA, Beauchamp NJ, Hillis AE, McKhann GM. Diffusion- and perfusion-weighted magnetic resonance imaging of the brain before and after coronary artery bypass grafting surgery. Stroke 2002; 33:2909-15. [PMID: 12468790 DOI: 10.1161/01.str.0000040408.75704.15] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Coronary artery bypass grafting (CABG) is a frequently performed surgical procedure that can be associated with neurological complications. Some studies have demonstrated that new focal brain lesions, detected by MRI, can develop after CABG. Furthermore, it has been suggested that the presence of such new lesions is associated with a decline in neurocognitive test scores. Advanced MRI techniques, including diffusion- (DWI) and perfusion-weighted imaging (PWI), offer important diagnostic advantages over conventional imaging in the assessment of patients undergoing CABG. We sought to determine whether focal PWI and DWI abnormalities could occur after CABG, particularly in patients without any measurable neurological deterioration. METHODS Thirteen patients prospectively underwent MRI with DWI and PWI before and after CABG. A battery of neurocognitive tests was administered before and after surgery. Demographic, clinical, and radiographic characteristics of the patients were collected and compared. RESULTS Four patients developed new DWI defects after CABG. The lesions were small, rounded, and multiple (3 of 4 patients). One of these patients was diagnosed with stroke on clinical grounds. The patients with new lesions had a larger neurocognitive decline than their counterparts with stable MRI. Other clinical characteristics of patients with new DWI lesions, including stroke risk factors, were similar to those of patients without MRI changes. No focal perfusion abnormalities were observed on preoperative or postoperative scans. CONCLUSIONS Postoperative DWI abnormalities can occur after CABG, even in patients without overt neurological defects. The PWI scans remained unchanged. Larger prospective studies are required to determine whether the new lesions are clearly associated with neurocognitive decline or with specific perioperative stroke risk factors.
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Affiliation(s)
- Lucas Restrepo
- Departments of Neurology, Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, USA.
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Price RR, Allison J, Massoth RJ, Clarke GD, Drost DJ. Practical aspects of functional MRI (NMR Task Group #8). Med Phys 2002; 29:1892-912. [PMID: 12201436 DOI: 10.1118/1.1494990] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Functional MR imaging (fMRI) based upon the Blood Oxygen Level Dependent (BOLD) effect is currently an important new tool for understanding basic brain function and specifically allowing the correlation of physiological activity with anatomical location without the use of ionizing radiation. The clinical role of fMRI is still being defined and is the subject of much research activity. In this report we present the underlying physical, technical and mathematical principals of BOLD fMRI along with descriptions of typical applications. Our purpose in this report is to provide, in addition to basic principles, an insight into the aspects of BOLD imaging, which may be used by the medical physicist to assist in the implement of fMRI procedures in either a hospital or research environment.
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Affiliation(s)
- Ronald R Price
- Vanderbilt University Medical Center, Department of Radiology and Radiological Sciences, Nashville, Tennessee 37232-2675, USA.
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