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Stapleton D, Darmonkow A, Ravi Chandran A, Milligan N, Saghian R, Shinar S, Whitehead CL, Hobson SR, Serghides L, Macgowan CK, Sled JG, Kingdom JC, Baschat AA, Parks WT, Cahill LS. Peripheral cord insertion is associated with adverse pregnancy outcome only when accompanied by clinically significant placental pathology. Ultrasound Obstet Gynecol 2023; 62:248-254. [PMID: 36971026 DOI: 10.1002/uog.26206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 02/17/2023] [Accepted: 03/08/2023] [Indexed: 06/18/2023]
Abstract
OBJECTIVE To examine the relationship between umbilical cord insertion site, placental pathology and adverse pregnancy outcome in a cohort of normal and complicated pregnancies. METHODS Sonographic measurement of the cord insertion and detailed placental pathology were performed in 309 participants. Associations between cord insertion site, placental pathology and adverse pregnancy outcome (pre-eclampsia, preterm birth, small-for-gestational age) were examined. RESULTS A total of 93 (30%) participants were identified by pathological examination to have a peripheral cord insertion site. Only 41 of the 93 (44%) peripheral cords were detected by prenatal ultrasound. Peripherally inserted cords were associated significantly (P < 0.0001) with diagnostic placental pathology (most commonly with maternal vascular malperfusion (MVM)); of which 85% had an adverse pregnancy outcome. In cases of isolated peripheral cords, without placental pathology, the incidence of adverse outcome was not statistically different when compared to those with central cord insertion and no placental pathology (31% vs 18%; P = 0.3). A peripheral cord with an abnormal umbilical artery (UA) pulsatility index (PI) corresponded to an adverse outcome in 96% of cases compared to 29% when the UA-PI was normal. CONCLUSIONS This study demonstrates that peripheral cord insertion is often part of the spectrum of findings of MVM disease and is associated with adverse pregnancy outcome. However, adverse outcome was uncommon when there was an isolated peripheral cord insertion and no placental pathology. Therefore, additional sonographic and biochemical features of MVM should be sought when a peripheral cord is observed. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.
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Affiliation(s)
- D Stapleton
- Department of Chemistry, Memorial University of Newfoundland, St John's, NL, Canada
| | - A Darmonkow
- Department of Chemistry, Memorial University of Newfoundland, St John's, NL, Canada
| | - A Ravi Chandran
- Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, ON, Canada
| | - N Milligan
- Division of Cardiology, Department of Paediatrics, The Hospital for Sick Children, Toronto, ON, Canada
| | - R Saghian
- Mouse Imaging Centre, The Hospital for Sick Children, Toronto, ON, Canada
| | - S Shinar
- Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, ON, Canada
| | - C L Whitehead
- Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, ON, Canada
- Pregnancy Research Centre, Department of Obstetrics and Gynaecology, Royal Women's Hospital, Parkville, Australia
| | - S R Hobson
- Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, ON, Canada
| | - L Serghides
- Toronto General Hospital Research Institute, University Health Network, Toronto, ON, Canada
- Department of Immunology and Institutes of Medical Sciences, University of Toronto, Toronto, ON, Canada
- Women's College Research Institute, Women's College Hospital, Toronto, ON, Canada
| | - C K Macgowan
- Translational Medicine, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - J G Sled
- Mouse Imaging Centre, The Hospital for Sick Children, Toronto, ON, Canada
- Translational Medicine, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
- Department of Obstetrics and Gynaecology, University of Toronto, Toronto, ON, Canada
| | - J C Kingdom
- Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, ON, Canada
- Department of Obstetrics and Gynaecology, University of Toronto, Toronto, ON, Canada
| | - A A Baschat
- Center for Fetal Therapy, Johns Hopkins Medicine, Baltimore, MD, USA
| | - W T Parks
- Department of Pathology, Mount Sinai Hospital, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - L S Cahill
- Department of Chemistry, Memorial University of Newfoundland, St John's, NL, Canada
- Discipline of Radiology, Memorial University of Newfoundland, St John's, NL, Canada
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2
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Arbabi A, Spencer Noakes L, Vousden D, Dazai J, Spring S, Botelho O, Keshavarzian T, Mattingly M, Ellegood JE, Nutter LMJ, Wissmann R, Sled JG, Lerch JP, Henkelman RM, Nieman BJ. Multiple-mouse magnetic resonance imaging with cryogenic radiofrequency probes for evaluation of brain development. Neuroimage 2022; 252:119008. [PMID: 35245675 DOI: 10.1016/j.neuroimage.2022.119008] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/09/2022] [Accepted: 02/15/2022] [Indexed: 11/17/2022] Open
Abstract
Multiple-mouse magnetic resonance imaging (MRI) increases scan throughput by imaging several mice simultaneously in the same magnet bore, enabling multiple images to be obtained in the same time as a single scan. This increase in throughput enables larger studies than otherwise feasible and is particularly advantageous in longitudinal study designs where frequent imaging time points result in high demand for MRI resources. Cryogenically-cooled radiofrequency probes (CryoProbes) have been demonstrated to have significant signal-to-noise ratio benefits over comparable room temperature coils for in vivo mouse imaging. In this work, we demonstrate implementation of a multiple-mouse MRI system using CryoProbes, achieved by mounting four such coils in a 30-cm, 7-Tesla magnet bore. The approach is demonstrated for longitudinal quantification of brain structure from infancy to early adulthood in a mouse model of Sanfilippo syndrome (mucopolysaccharidosis type III), generated by knockout of the Hgsnat gene. We find that Hgsnat-/- mice have regionally increased growth rates compared to Hgsnat+/+ mice in a number of brain regions, notably including the ventricles, amygdala and superior colliculus. A strong sex dependence was also noted, with the lateral ventricle volume growing at an accelerated rate in males, but several structures in the brain parenchyma growing faster in females. This approach is broadly applicable to other mouse models of human disease and the increased throughput may be particularly beneficial in studying mouse models of neurodevelopmental disorders.
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Affiliation(s)
- A Arbabi
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada; Donders Institute for Brain, Cognition and Behaviour, Nijmegen, Netherlands
| | - L Spencer Noakes
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada; Pre-Therapeutic Target Discovery, Regeneron Pharmaceuticals, Tarrytown, NY, United States
| | - D Vousden
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada; DataKind UK, London, UK
| | - J Dazai
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada
| | - S Spring
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada
| | - O Botelho
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada
| | - T Keshavarzian
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - M Mattingly
- Bruker BioSpin Corporation, Billerica, MA, United States
| | - J E Ellegood
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada
| | - L M J Nutter
- The Centre for Phenogenomics, Hospital for Sick Children, Toronto, ON, Canada
| | - R Wissmann
- Bruker BioSpin Corporation, Ettlingen, Germany
| | - J G Sled
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada; Translational Medicine, Hospital for Sick Children, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - J P Lerch
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada; Neuroscience and Mental Health, Hospital for Sick Children, Toronto, ON, Canada; Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - R M Henkelman
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada; Translational Medicine, Hospital for Sick Children, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - B J Nieman
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada; Translational Medicine, Hospital for Sick Children, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada; Ontario Institute for Cancer Research, Toronto, ON, Canada.
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3
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Shreeve N, Traherne JA, Sovio U, Hawkes D, Depierreux D, Huhn O, Jayaraman J, Horowitz A, Ghadially H, Perry JRB, Moffett A, Sled JG, Sharkey AM, Colucci F. NKG2A educates uterine NK cells to optimise pregnancy outcomes in humans and mice. The Journal of Immunology 2021. [DOI: 10.4049/jimmunol.206.supp.55.05] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Abstract
The conserved CD94/NKG2A receptor binds HLA-E in humans and Qa-1 in mice. Besides inhibiting natural killer (NK) cell activation, NKG2A drives NK-cell education, a process influenced by HLA-B alleles that promotes NK cell function. In human populations some individuals are genetically programmed to favour NKG2A education and have more robust NK cell function. NKG2A is expressed by nearly all human and roughly half mouse uterine NK cells (uNK), but the importance of NK-cell education in physiology is unknown.
Here we show that NKG2A was required for uNK cell-education in dams. Genetic ablation of NKG2A caused sub-optimal vascular responses in pregnancy, increased rate of smaller fetuses, which grew asymmetrically with abnormal brain development, and changes in placental gene expression consistent with stress. These are features of the human syndrome pre-eclampsia. In a genome-wide association study of 7,219 cases and 155,660 control pregnancies, we found that the maternal HLA-B allele that does not favour NKG2A education, was associated with a 7% greater relative risk of pre-eclampsia (P=0.005, OR= 1.07).
These results establish the relevance of NK cell education in physiology and show that the maternal HLA-B –> HLA-E –> NKG2A pathway contributes to healthy pregnancy and may influence offspring health.
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Affiliation(s)
| | | | - U Sovio
- 1University of Cambridge, UK
| | | | | | - O Huhn
- 1University of Cambridge, UK
- 2AstraZeneca, Cambridge, UK
| | | | - A Horowitz
- 3Icahn School of Medicine at Mount Sinai, New York, USA
| | | | | | | | - JG Sled
- 4University Hospital for Sick Children, Toronto, Canada
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Mohan H, Guzman Lenis M, Laurette EY, Tejada O, Sanghvi T, Leung KY, Cahill LS, Sled JG, Delgado-Olguín P, Greene NDE, Copp AJ, Serghides L. In response to the Letter to the Editor by Romach et al. re our publication "Dolutegravir in pregnant mice is associated with increased rates of fetal defects at therapeutic but not at supratherapeutic levels". EBioMedicine 2021; 66:103334. [PMID: 33862586 PMCID: PMC8054139 DOI: 10.1016/j.ebiom.2021.103334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 03/24/2021] [Indexed: 11/25/2022] Open
Affiliation(s)
- H Mohan
- Toronto General Hospital Research Institute, University Health Network, Toronto, Canada
| | - M Guzman Lenis
- Toronto General Hospital Research Institute, University Health Network, Toronto, Canada
| | - E Y Laurette
- Toronto General Hospital Research Institute, University Health Network, Toronto, Canada
| | - O Tejada
- Toronto General Hospital Research Institute, University Health Network, Toronto, Canada
| | - T Sanghvi
- Toronto General Hospital Research Institute, University Health Network, Toronto, Canada
| | - K-Y Leung
- Developmental Biology & Cancer Department, UCL Great Ormond Street Institute of Child Health, University College London, London, UK
| | - L S Cahill
- Mouse Imaging Centre, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Chemistry, Memorial University of Newfoundland, St John's, Newfoundland and Labrador, Canada
| | - J G Sled
- Mouse Imaging Centre, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; Translational Medicine, The Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - P Delgado-Olguín
- Translational Medicine, The Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Heart & Stroke Richard Lewar Centre of Excellence, Toronto, Ontario M5S 3H2, Canada
| | - N D E Greene
- Developmental Biology & Cancer Department, UCL Great Ormond Street Institute of Child Health, University College London, London, UK
| | - A J Copp
- Developmental Biology & Cancer Department, UCL Great Ormond Street Institute of Child Health, University College London, London, UK
| | - L Serghides
- Toronto General Hospital Research Institute, University Health Network, Toronto, Canada; Department of Immunology and Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada; Women's College Research Institute, Women's College Hospital, Toronto, Ontario, Canada.
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5
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Rocca MA, Sonkin M, Copetti M, Pagani E, Arnold DL, Narayanan S, Sled JG, Banwell B, Filippi M. Diffusion tensor magnetic resonance imaging in very early onset pediatric multiple sclerosis. Mult Scler 2015. [DOI: 10.1177/1352458515596600] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Objectives: Active myelination during childhood may influence the impact of multiple sclerosis (MS) on brain structural integrity. We studied normal-appearing white matter (NAWM) in children with MS onset before age 12 years using diffusion tensor (DT) magnetic resonance imaging (MRI). Methods: DT MRI scans were obtained from 22 MS children with their first attack before age 12 years, and 31 healthy controls from two referral centers. Using probabilistic tractography, brain tissue integrity within interhemispheric, intrahemispheric, and projection tracts was compared between patients and site-matched controls. The impact of disease and age at MRI on tract NAWM fractional anisotropy (FA) and mean diffusivity (MD) values was evaluated using linear models. Results: Compared to controls, pediatric MS patients had reduced FA and increased MD of the bilateral superior longitudinal fasciculus and corpus callosum (CC), without center-by-group interaction. CC NAWM average FA was correlated with brain T2 lesion volume. In controls, the majority of the tracts analyzed showed a significant increase of FA and decrease of MD with age. Such a linear correlation was lost in patients. Conclusions: In very young pediatric MS patients, DT MRI abnormalities affect brain WM tracts differentially, and are only partially correlated with focal WM lesions. Impaired maturation of WM tracts with age may be an additional factor contributing to these findings.
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Affiliation(s)
- MA Rocca
- Neuroimaging Research Unit, San Raffaele Scientific Institute, ‘Vita-Salute’ San Raffaele University, Italy
| | - M Sonkin
- Research Institute, The Hospital for Sick Children, Canada
| | - M Copetti
- IRCCS-Ospedale Casa Sollievo della Sofferenza, Italy
| | - E Pagani
- Neuroimaging Research Unit, San Raffaele Scientific Institute, ‘Vita-Salute’ San Raffaele University, Italy
| | - DL Arnold
- McConnell Brain Imaging Center, Montreal Neurological Institute, Canada
| | - S Narayanan
- McConnell Brain Imaging Center, Montreal Neurological Institute, Canada
| | - JG Sled
- Research Institute, The Hospital for Sick Children, Canada
| | - B Banwell
- Research Institute, The Hospital for Sick Children, Canada/The Children’s Hospital of Philadelphia, USA
| | - M Filippi
- Neuroimaging Research Unit, San Raffaele Scientific Institute, ‘Vita-Salute’ San Raffaele University, Italy
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Verhey LH, van Pelt-Gravesteijn ED, Ketelslegers IA, Neuteboom RF, Catsman-Berrevoets CE, Feldman BM, Streiner DL, Sled JG, Hintzen RQ, Banwell B. Validation of MRI predictors of multiple sclerosis diagnosis in children with acute CNS demyelination. Mult Scler Relat Disord 2013; 2:193-9. [PMID: 25877725 DOI: 10.1016/j.msard.2012.12.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 12/05/2012] [Accepted: 12/11/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND In a recent Canadian prospective study of children with acute demyelinating syndromes (ADS), we demonstrated that the presence of T2 periventricular and T1-hypointense lesions predicted MS diagnosis. We aimed to validate these predictors in a Dutch cohort of children with ADS. METHODS Participants with ADS were identified from a prospective cohort or archived dataset. MS was diagnosed based on clinical or MRI evidence of relapsing disease. Baseline MRI scans were evaluated for the presence of the two predictive parameters. Sensitivity, specificity, positive (LR+) and negative likelihood ratios (LR-), and positive (PPV) and negative predictive value (NPV) were calculated to evaluate the performance of the MRI parameters at classifying children as having MS or monophasic demyelination. FINDINGS Of 115 children identified with ADS between December 1993 and December 2009, MRI scans from 87 children (45 prospective; 47 archived) were evaluated; scans of 28 children were excluded due to incomplete or poor quality imaging. Mean duration of observation was longer in the archived group (7.1 years, SD 3.5) than the prospective cohort (3.3 years, SD 1.4). 30 children were diagnosed with MS. Performance of the parameters was not statistically different between the prospective cohort (sensitivity 93.3% [68.1-99.8]; specificity 86.7% [69.3-96.2]; LR+ 7.0 [2.8-17.6]; LR- 0.08 [0.01-0.5]; PPV 77.8% [52.4-93.6]; NPV 96.3% [81.0-99.9]) and archived group (sensitivity 66.7% [38.4-88.2]; specificity 85.2% [66.3-95.8]; LR+ 4.5 [1.7-11.9]; LR- 0.4 [0.2-0.8]; PPV 71.4% [41.9-91.6]; NPV 82.1% [63.1-93.9]). INTERPRETATION In an independent Dutch cohort, we confirm that the presence of ≥1 T2 periventricular and ≥1 T1-hypointense lesions reliably identifies children with MS. FUNDING Dutch MS Research Foundation.
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Affiliation(s)
- L H Verhey
- Program in Neuroscience & Mental Health, The Hospital for Sick Children, Toronto, Canada; Institute of Medical Science, University of Toronto, Toronto, Canada
| | | | | | - R F Neuteboom
- Department of Pediatric Neurology, Erasmus MC, Sophia Children's Hospital, Rotterdam, The Netherlands
| | - C E Catsman-Berrevoets
- Department of Pediatric Neurology, Erasmus MC, Sophia Children's Hospital, Rotterdam, The Netherlands
| | - B M Feldman
- Division of Rheumatology, Department of Pediatrics, The Hospital for Sick Children, Toronto, Canada; Institute of Health Policy, Management & Evaluation, University of Toronto, Toronto, Canada; Department of Medicine, University of Toronto, Toronto, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
| | - D L Streiner
- Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada; Department of Psychiatry & Behavioural Neurosciences, McMaster University, Hamilton, Canada; Department of Psychiatry, University of Toronto, Toronto, Canada
| | - J G Sled
- Department of Medical Biophysics, University of Toronto, Toronto, Canada; Program in Physiology & Experimental Medicine, The Hospital for Sick Children, Toronto, Canada
| | - R Q Hintzen
- Department of Neurology, Erasmus MC, Rotterdam, The Netherlands; Department of Pediatric Neurology, Erasmus MC, Sophia Children's Hospital, Rotterdam, The Netherlands
| | - B Banwell
- Program in Neuroscience & Mental Health, The Hospital for Sick Children, Toronto, Canada; Institute of Medical Science, University of Toronto, Toronto, Canada; Division of Neurology, Department of Pediatrics, The Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, USA.
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7
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Verhey LH, Branson HM, Laughlin S, Shroff MM, Benseler SM, Feldman BM, Streiner DL, Sled JG, Banwell B. Development of a standardized MRI scoring tool for CNS demyelination in children. AJNR Am J Neuroradiol 2013; 34:1271-7. [PMID: 23348761 DOI: 10.3174/ajnr.a3382] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND AND PURPOSE The degree to which MR imaging is useful in the diagnosis of MS is predicated on standardized and reliable evaluation of MR imaging parameters. We aimed to devise items for an MR imaging scoring tool that would have high inter-rater agreement and would be straightforward to apply. MATERIALS AND METHODS On the basis of a literature search and consensus of an expert panel, we identified 48 parameters that describe acute CNS demyelination, predict MS diagnosis, or characterize demyelinating disorder mimics. MR images of children with clinically confirmed MS, monophasic ADEM, and angiography-negative biopsy-positive small-vessel primary angiitis of the CNS were scored by 2 neuroradiologists independently, using the preliminary 48-parameter tool. Parameters with Cohen κ ≥ 0.6 and deemed important in predicting diagnosis were retained. Parameters not visualized on routine clinical imaging or not important in differentiating MS, ADEM, and SV-cPACNS were discarded. RESULTS Of 65 eligible patients, 55 children were enrolled (16 with monophasic ADEM, 27 with MS, 12 with SV-cPACNS); 10 were excluded (6 had hard-copy films, 4 did not meet MR imaging quality requirements). Of the 48 parameters, 16 were retained in the final scoring tool. The remaining 28 parameters were discarded: 4 had κ < 0.6 and were not deemed useful in predicting diagnosis; 9 were not visible on routinely acquired clinical images; and 15 had inter-rater agreement ≥0.6 but were not useful in differentiating monophasic ADEM, MS, and SV-cPACNS. CONCLUSIONS We propose a 16-parameter MR imaging scoring tool that is straightforward to apply in the clinical setting and demonstrates high inter-rater agreement.
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Affiliation(s)
- L H Verhey
- Program in Neuroscience and Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada
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8
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Verhey L, Branson H, Shroff M, Callen D, Sled J, Narayanan S, Bar-Or A, Sadovnick D, Arnold D, Marrie RA, Banwell B. MRI Features Distinguish Monophasic ADEM from MS: Findings from a Canadian Cohort of Children with Incident CNS Demyelination (S50.002). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.s50.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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9
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Sonkin M, Tipu V, Banwell B, Narayanan S, Ghassemi R, Arnold D, Sled J. Diffusion Tensor Imaging: Abnormal White Matter at the Time of a First Attack Distinguishes Children with Multiple Sclerosis from Children with Monophasic Demyelination and from Healthy Children (S50.007). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.s50.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Sadaka Y, Verhey L, Shroff M, Branson H, Arnold D, Narayanan S, Sled J, Bar-Or A, Sadovnick D, McGowan M, Ann Marrie R, Banwell B. 2010 McDonald Criteria for Diagnosing Pediatric Multiple Sclerosis (P01.155). Neurology 2012. [DOI: 10.1212/wnl.78.1_meetingabstracts.p01.155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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11
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Kerbrat A, Aubert-Broche B, Fonov V, Narayanan S, Sled JG, Arnold DA, Banwell B, Collins DL. Reduced head and brain size for age and disproportionately smaller thalami in child-onset MS. Neurology 2012; 78:194-201. [PMID: 22218275 DOI: 10.1212/wnl.0b013e318240799a] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE Whole brain and regional volume measurement methods were used to quantify white matter, gray matter, and deep gray matter structure volumes in a population of patients with pediatric-onset multiple sclerosis (MS). METHODS Subjects included 38 patients (mean age 15.2 ± 2.4 years) and 33 age- and sex-matched healthy control (HC) participants. MRI measures included intracranial volume, normalized brain volume, normalized white and gray matter volume, and volumes of the thalamus, globus pallidus, putamen, and caudate. Because these volumes vary across age and sex in children, we normalized the volume measurements for MS and control groups by computing z scores using normative values obtained from healthy children enrolled in the MRI Study of Normal Brain Development. RESULTS The intracranial volume z score was significantly lower in the patients with MS (-0.45 ± 1.16; mean ± SD) compared with the HC participants (+0.25 ± 0.98; p = 0.01). Patients with MS also demonstrated significant decreases in normalized brain volume z scores (-1.09 ± 1.49 vs -0.05 ± 1.22; p = 0.002). After correction for global brain volume, thalamic volumes in the MS population remained lower than those of HCs (-0.68 ± 1.72 vs 0.15 ± 1.35; p = 0.02), indicating an even greater loss of thalamic tissue relative to more global brain measures. Moderate correlations were found between T2-weighted lesion load and normalized thalamic volumes (r = -0.44, p < 0.01) and normalized brain volume (r = -0.47, p < 0.01) and between disease duration and normalized thalamic volume (r = -0.58, p < 0.001) and normalized brain volume (r = -0.46, p < 0.01). CONCLUSIONS When compared with age- and sex-matched control subjects, the onset of MS during childhood is associated with a smaller overall head size, brain volume, and an even smaller thalamic volume.
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Affiliation(s)
- A Kerbrat
- McConnell Brain Imaging Center , Montreal Neurological Institute, McGill University, Montreal, Canada
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12
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Till C, Ghassemi R, Aubert-Broche B, Kerbrat A, Collins DL, Narayanan S, Arnold DL, Desrocher M, Sled JG, Banwell BL. MRI correlates of cognitive impairment in childhood-onset multiple sclerosis. Neuropsychology 2011; 25:319-32. [PMID: 21534686 DOI: 10.1037/a0022051] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
OBJECTIVE Brain MRI measures were correlated with neuropsychological function in 35 pediatric-onset multiple sclerosis (MS) patients and 33 age- and sex-matched healthy controls. METHOD Mean age of MS patients was 16.3 ± 2.3 years with average disease duration of 4.3 ± 3.1 years. Cortical gray matter, thalamic, and global brain volumes were calculated for all participants using a scaling factor computed using normalization of atrophy method to normalize total and regional brain volumes for head size. T1- and T2-weighted lesion volumes were calculated for MS patients. RESULTS Cognitive impairment (CI) was identified in 29% of the MS cohort. Cognitive deficits predominantly involved attention and processing speed, expressive language, and visuomotor integration. Relative to controls, the MS group showed significantly lower thalamic volume (p < .001), total brain volume (p < .008), and gray matter volume (p < .015). Corpus callosum area and thalamic volume differentiated patients identified as having CI from those without CI (p < .05). Regression models controlling for disease duration and age indicated that thalamic volume accounted for significant incremental variance in predicting global IQ, processing speed, and expressive vocabulary (ΔR2 ranging from .43 to .60) and was the most robust MRI predictor of cognition relative to other MRI metrics. CONCLUSIONS The robust association between cognitive function and reduced size of thalamus and global brain volume in pediatric-onset MS patients implicate neurodegenerative processes early in the disease course, and suggest that plasticity of an immature central nervous system is not sufficient to protect patients from the deleterious consequences of MS on cognitive neural networks. (PsycINFO Database Record (c) 2011 APA, all rights reserved).
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Affiliation(s)
- C Till
- Department of Psychology, York University, Toronto, Ontario, Canada.
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13
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Aubert-Broche B, Fonov V, Ghassemi R, Narayanan S, Arnold DL, Banwell B, Sled JG, Collins DL. Regional brain atrophy in children with multiple sclerosis. Neuroimage 2011; 58:409-15. [PMID: 21414412 DOI: 10.1016/j.neuroimage.2011.03.025] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 03/04/2011] [Accepted: 03/08/2011] [Indexed: 11/17/2022] Open
Abstract
We used cross-sectional tensor-based morphometry to visualize reduced volume in the whole brains of pediatric patients with multiple sclerosis, relative to healthy controls. As a marker of local volume difference, we used the Jacobian determinant of the deformation field that maps each subject to a standard space. To properly assess abnormal differences in volume in this age group, it is necessary to account for the normal, age-related differences in brain volume. This was accomplished by computing normalized z-score Jacobian determinant values at each voxel to represent the local volume difference (in standard deviations) between an individual subject and an age- and sex-matched healthy normal population. Compared with healthy controls, pediatric patients with multiple sclerosis exhibited significantly reduced volumes within the thalamus and the splenium of the corpus callosum and significant expansions in the ventricles. While T2-weighted lesion volume was correlated with reduced splenium volume, no correlation was found between T2-weighted lesion volume and reduced thalamic volume. Reduced volumes of the optic pathways, including that of the optic tracts and optic radiations, correlated with disease duration. Our results suggest that focal inflammatory lesions may play an important role in tract degeneration, including transsynaptic degeneration.
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Affiliation(s)
- B Aubert-Broche
- McConnell Brain Imaging Center, Montreal Neurological Institute, McGill University, Montreal, Canada
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14
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Zamyadi M, Baghdadi L, Lerch JP, Bhattacharya S, Schneider JE, Henkelman RM, Sled JG. Mouse embryonic phenotyping by morphometric analysis of MR images. Physiol Genomics 2010; 42A:89-95. [PMID: 20682847 PMCID: PMC2957795 DOI: 10.1152/physiolgenomics.00091.2010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A new method is described for automatic detection of subtle morphological phenotypes in mouse embryos. Based on high-resolution magnetic resonance imaging scanning and nonlinear image alignment, this method is demonstrated by comparing the morphology of two inbred strains, C57BL/6J and 129Sv/S1ImJ, at 15.5 days postconception. Mouse embryo morphology was found to be highly amenable to this kind of analysis with very low levels (on average 110 μm) of residual anatomical variation within strains after linear differences in pose and scale are removed. Mapping of local size differences showed that C57BL/6J embryos were larger than 129Sv/S1ImJ embryos, although these differences were not uniformly distributed across the anatomy. Expressed in terms of organ volumes, heart and lung were larger in C57BL/6J embryos, while brain and liver were comparable in volume between strains. The positive relationship between organ size and embryo size was consistent for the two strains but differed by organ, with the brain and liver being the least variable. Together these findings suggest the power of this technique for detecting subtle phenotypic differences arising from mutated genes.
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Affiliation(s)
- M Zamyadi
- Department of Medical Biophysics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada
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15
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Dudani A, Ghassemi R, Narayanan S, Arnold DL, Sled JG, Banwell B, Till C. Pediatric Multiple Sclerosis and Executive Function. Paediatr Child Health 2010. [DOI: 10.1093/pch/15.suppl_a.60ab] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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16
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Abstract
The availability of detailed three-dimensional images of vascular trees from mammalian organs provides a wealth of essential data for understanding the processes and mechanisms of vascular patterning. Using this detailed geometric data requires the ability to compare individual representations of vascular trees in statistically meaningful ways. This article provides some comparisons of geometry and also of simulated hemodynamics, enabling the identification of similarities and differences among 10 individual specimens (5 placenta specimens and 5 lung specimens). Similar comparisons made with a series of models (starting with the simplest and increasing in complexity) enable the identification of essential features that are needed to account for the patterns and function of vascular arborization.
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Affiliation(s)
- J Yang
- Mouse Imaging Centre, The Hospital for Sick Children, Toronto, Ontario, Canada
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17
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Xie G, Clapcote SJ, Nieman BJ, Tallerico T, Huang Y, Vukobradovic I, Cordes SP, Osborne LR, Rossant J, Sled JG, Henderson JT, Roder JC. Forward genetic screen of mouse reveals dominant missense mutation in the P/Q-type voltage-dependent calcium channel, CACNA1A. Genes, Brain and Behavior 2007; 6:717-27. [PMID: 17376154 DOI: 10.1111/j.1601-183x.2007.00302.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Dominant mutations of the P/Q-type Ca(2+) channel (CACNA1A) underlie several human neurological disorders, including episodic ataxia type 2, familial hemiplegic migraine 1 (FHM1) and spinocerebellar ataxia 6, but have not been found previously in the mouse. Here we report the first dominant ataxic mouse model of Cacna1a mutation. This Wobbly mutant allele of Cacna1a was identified in an ethylnitrosourea (ENU) mutagenesis dominant behavioral screen. Heterozygotes exhibit ataxia from 3 weeks of age and have a normal life span. Homozygotes have a righting reflex defect from postnatal day 8 and later develop severe ataxia and die prematurely. Both heterozygotes and homozygotes exhibit cerebellar atrophy with focal reduction of the molecular layer. No obvious loss of Purkinje cells or decrease in size of the granule cell layer was observed. Real-time polymerase chain reaction revealed altered expression levels of Cacna1g, Calb2 and Th in Wobbly cerebella, but Cacna1a messenger RNA and protein levels were unchanged. Positional cloning revealed that Wobbly mice have a missense mutation leading to an arginine to leucine (R1255L) substitution, resulting in neutralization of a positively charged amino acid in repeat III of voltage sensor segment S4. The dominance of the Wobbly mutation more closely resembles patterns of CACNA1A mutation in humans than previously described mouse recessive mutants (tottering, leaner, rolling Nagoya and rocker). Positive-charge neutralization in S4 has also been shown to underlie several cases of human dominant FHM1 with ataxia. The Wobbly mutant thus highlights the importance of the voltage sensor and provides a starting point to unravel the neuropathological mechanisms of this disease.
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MESH Headings
- Amino Acid Substitution/genetics
- Animals
- Ataxia/genetics
- Atrophy/genetics
- Calcium Channels, N-Type
- Calcium Channels, P-Type/genetics
- Calcium Channels, P-Type/metabolism
- Calcium Channels, Q-Type/genetics
- Calcium Channels, Q-Type/metabolism
- Cerebellum/metabolism
- Cerebellum/pathology
- Dystonia/genetics
- Female
- Gait/genetics
- Genes, Dominant/genetics
- Male
- Mice
- Mice, Inbred C3H
- Mice, Mutant Strains
- Mutation, Missense/genetics
- Polymorphism, Single Nucleotide/genetics
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Affiliation(s)
- G Xie
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada
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18
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Dorr A, Sled JG, Kabani N. Three-dimensional cerebral vasculature of the CBA mouse brain: A magnetic resonance imaging and micro computed tomography study. Neuroimage 2007; 35:1409-23. [PMID: 17369055 DOI: 10.1016/j.neuroimage.2006.12.040] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Revised: 12/07/2006] [Accepted: 12/08/2006] [Indexed: 11/15/2022] Open
Abstract
Studies of mouse cerebral vasculature to date have focused on the circle of Willis without examining the morphological distribution of blood vessels through the rest of the brain. Since mouse models are frequently used in brain-related studies, there is a need for a comprehensive cerebral vasculature atlas for the mouse with an emphasis on the location of vessels with respect to neuroanatomical structures, the watershed regions associated with specific arteries, as well as a consistent nomenclature of the cerebral vessels. This article describes such an atlas, based on a combination of magnetic resonance and computed tomography technology to yield high-resolution volumetric and vasculature data on CBA mouse. This three-dimensional vasculature dataset provides an anatomical resource for future mouse studies.
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Affiliation(s)
- A Dorr
- Sunnybrook Health Sciences Centre, 3080 Yonge Street, Suite 6020, P.O. Box 89, Toronto, ON, Canada M4N 3N1
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19
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Rennie MY, Whiteley KJ, Kulandavelu S, Adamson SL, Sled JG. 3D visualisation and quantification by microcomputed tomography of late gestational changes in the arterial and venous feto-placental vasculature of the mouse. Placenta 2007; 28:833-40. [PMID: 17324457 DOI: 10.1016/j.placenta.2006.12.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2006] [Revised: 11/24/2006] [Accepted: 12/18/2006] [Indexed: 10/23/2022]
Abstract
This study evaluates microcomputed tomography (micro-CT) as a method to obtain quantitative three-dimensional (3D) information on the arterial and venous vasculature of the mouse placenta. Surface renderings at embryonic days (E) 13.5, 15.5, and 18.5 (full term) revealed that the arterial and venous vasculature branched within the chorionic plate whereas only the arterial vasculature deeply penetrated the placenta. Umbilical vessel diameters measured by micro-CT did not significantly differ from those measured non-invasively in vivo by ultrasound biomicroscopy. Variability in umbilical diameters, and surface area and volume measurements of arterial and venous vascular trees due to experimental error was low relative to biological variability, and significant inter-litter differences within gestational ages were detected. Furthermore, umbilical vessel diameter increased significantly and incrementally to an arterial diameter of 0.631+/-0.009 mm and a venous diameter of 0.690+/-0.018 mm at E18.5. Umbilical vein diameter was 3-9% greater than the artery, and both were significantly correlated with embryonic body weight (R> or =0.96). Surface area and volume were determined for vessels greater than the minimum resolvable diameter of 0.03 mm which therefore excluded capillaries. Arterial surface area and volume were unchanged from E13.5-15.5 but then more than doubled at E18.5 (to 170+/-13 mm(2) and 7.2+/-0.8mm(3), respectively). Venous surface areas and volumes changed similarly with development although surface areas were lower than their arterial counterparts. We conclude that micro-CT has sufficient accuracy and precision to quantify late gestational changes in the 3D structure of the arterial and venous vasculature of the mouse placenta.
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Affiliation(s)
- M Y Rennie
- Department of Medical Biophysics, University of Toronto and the Mouse Imaging Centre, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada
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20
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Abstract
Blood perfusion in organs has been shown to be heterogeneous in a number of cases. At the same time, a number of models of vascular structure and flow have been proposed that also generate heterogeneous perfusion. Although a relationship between local perfusion and vascular structure has to exist, no model has yet been validated as an accurate description of this relationship. A study of perfusion and three-dimensional (3D) arterial structure in individual rat kidneys is presented, which allows comparison between local measurements of perfusion and model-based predictions. High-resolution computed tomography is used to obtain images of both deposited microspheres and of an arterial cast in the same organ. Microsphere deposition is used as an estimate of local perfusion. A 3D cylindrical pipe model of the arterial tree is generated based on an image of the arterial cast. Results of a flow model are compared with local microsphere deposition. High correlation (r(2) > 0.94) was observed between measured and modeled flows through the vascular tree segments. However, the relative dispersion of the microsphere perfusion measurement was two- to threefold higher than perfusion heterogeneity calculated in the flow model. Also, there was no correlation in the residual deviations between the methods. This study illustrates the importance of comparing models of local perfusion with in vivo measurements of perfusion in the same biologically realistic vascular tree.
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Affiliation(s)
- M Marxen
- Hospital for Sick Children Mouse Imaging Centre, 555 Univ. Ave, Toronto, Ontario, Canada
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21
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Sled JG, Levesque I, Santos AC, Francis SJ, Narayanan S, Brass SD, Arnold DL, Pike GB. Regional variations in normal brain shown by quantitative magnetization transfer imaging. Magn Reson Med 2004; 51:299-303. [PMID: 14755655 DOI: 10.1002/mrm.10701] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A quantitative magnetization transfer imaging (qMTI) study, based on a two-pool model of magnetization transfer, was performed on seven normal subjects to determine, on a regional basis, normal values for the pool sizes, exchange, and relaxation parameters that characterize the MT phenomenon. Regions were identified on high-resolution anatomical scans using a combination of manual and automatic methods. Only voxels identified as pure tissue at the resolution of the quantitative scans were considered for analysis. While no left/right differences were observed, significant differences were found among white-matter regions and gray-matter regions. These regional differences were compared with existing cytoarchitectural data. In addition, the pattern and magnitude of the regional differences observed in white matter was found to be different from that reported previously for an alternative putative MRI measure of myelination, the 10-50-ms T2 component described as myelin water.
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Affiliation(s)
- J G Sled
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
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22
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Abstract
We describe a novel imaging technique that yields all of the observable properties of the binary spin-bath model for magnetization transfer (MT) and demonstrate this method for in vivo studies of the human head. Based on a new model of the steady-state behavior of the magnetization during a pulsed MT-weighted imaging sequence, this approach yields parametric images of the fractional size of the restricted pool, the magnetization exchange rate, the T(2) of the restricted pool, as well as the relaxation times in the free pool. Validated experimentally on agar gels and samples of uncooked beef, we demonstrate the method's application on two normal subjects and a patient with multiple sclerosis.
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Affiliation(s)
- J G Sled
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
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23
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Arnold JB, Liow JS, Schaper KA, Stern JJ, Sled JG, Shattuck DW, Worth AJ, Cohen MS, Leahy RM, Mazziotta JC, Rottenberg DA. Qualitative and quantitative evaluation of six algorithms for correcting intensity nonuniformity effects. Neuroimage 2001; 13:931-43. [PMID: 11304088 DOI: 10.1006/nimg.2001.0756] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The desire to correct intensity nonuniformity in magnetic resonance images has led to the proliferation of nonuniformity-correction (NUC) algorithms with different theoretical underpinnings. In order to provide end users with a rational basis for selecting a given algorithm for a specific neuroscientific application, we evaluated the performance of six NUC algorithms. We used simulated and real MRI data volumes, including six repeat scans of the same subject, in order to rank the accuracy, precision, and stability of the nonuniformity corrections. We also compared algorithms using data volumes from different subjects and different (1.5T and 3.0T) MRI scanners in order to relate differences in algorithmic performance to intersubject variability and/or differences in scanner performance. In phantom studies, the correlation of the extracted with the applied nonuniformity was highest in the transaxial (left-to-right) direction and lowest in the axial (top-to-bottom) direction. Two of the six algorithms demonstrated a high degree of stability, as measured by the iterative application of the algorithm to its corrected output. While none of the algorithms performed ideally under all circumstances, locally adaptive methods generally outperformed nonadaptive methods.
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Affiliation(s)
- J B Arnold
- Neurology Service, PET Imaging Center, Minneapolis VA Medical Center, One Veterans Drive, Minneapolis, Minnesota 55417, USA
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24
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Abstract
A method for analyzing general pulsed magnetization transfer (MT) experiments in which off-resonance saturation pulses are interleaved with on-resonance excitation pulses is presented. We apply this method to develop a steady-state signal equation for MT-weighted spoiled gradient echo sequences and consider approximations that facilitate its rapid computation. Using this equation, we assess various experimental designs for quantitatively imaging the fractional size of the restricted pool, cross-relaxation rate, and T(1) and T(2) relaxation times of the two pools in a binary spin bath system. From experiments on agar gel, this method is shown to reliably and accurately estimate the exchange and relaxation properties of a material in an imaging context, suggesting the feasibility of using this technique in vivo.
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Affiliation(s)
- J G Sled
- McConnell Brain Imaging Centre, McGill University, Montréal, Québec, H3A 2B4, Canada.
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25
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Abstract
A new method is described for compensating for the bias introduced by variations in radiofrequency (RF) field strength and main magnetic field strength when making quantitative T(2) measurements using MRI. Field measurements made during the MRI study are used in combination with a signal model for off-resonance and imperfect RF pulses to correct the estimated T(2) value at every voxel. Applicable to both multicomponent and conventional single-component T(2) studies, the method has been validated experimentally using paramagnetic salt solutions in a multicompartment phantom. Studies of the human head are used to demonstrate the method in practice.
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Affiliation(s)
- J G Sled
- McConnell Brain Imaging Centre, Montréal Neurological Institute, McGill University, Montréal, Québec, Canada.
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26
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Sled JG, Pike GB. Standing-wave and RF penetration artifacts caused by elliptic geometry: an electrodynamic analysis of MRI. IEEE Trans Med Imaging 1998; 17:653-662. [PMID: 9845320 DOI: 10.1109/42.730409] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Motivated by the observation that the diagonal pattern of intensity nonuniformity usually associated with linearly polarized radio-frequency (RF) coils is often present in neurological scans using circularly polarized coils, a theoretical analysis has been conducted of the intensity nonuniformity inherent in imaging an elliptically shaped object using 1.5-T magnets and circularly polarized RF coils. This first principle analysis clarifies, for the general case of conducting objects, the relationship between the excitation field and the reception sensitivity of circularly and linearly polarized coils. The results, validated experimentally using a standard spin-echo imaging sequence and an in vivo B1 field mapping technique, are shown to be accurate to within 1%-2% root mean square, suggesting that these electromagnetic interactions with the object account for most of the intensity nonuniformity observed.
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Affiliation(s)
- J G Sled
- McConnell Brain Imaging Centre, Montréal Neurological Institute and McGill University, Canada.
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27
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Collins DL, Zijdenbos AP, Kollokian V, Sled JG, Kabani NJ, Holmes CJ, Evans AC. Design and construction of a realistic digital brain phantom. IEEE Trans Med Imaging 1998; 17:463-8. [PMID: 9735909 DOI: 10.1109/42.712135] [Citation(s) in RCA: 941] [Impact Index Per Article: 36.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
After conception and implementation of any new medical image processing algorithm, validation is an important step to ensure that the procedure fulfills all requirements set forth at the initial design stage. Although the algorithm must be evaluated on real data, a comprehensive validation requires the additional use of simulated data since it is impossible to establish ground truth with in vivo data. Experiments with simulated data permit controlled evaluation over a wide range of conditions (e.g., different levels of noise, contrast, intensity artefacts, or geometric distortion). Such considerations have become increasingly important with the rapid growth of neuroimaging, i.e., computational analysis of brain structure and function using brain scanning methods such as positron emission tomography and magnetic resonance imaging. Since simple objects such as ellipsoids or parallelepipedes do not reflect the complexity of natural brain anatomy, we present the design and creation of a realistic, high-resolution, digital, volumetric phantom of the human brain. This three-dimensional digital brain phantom is made up of ten volumetric data sets that define the spatial distribution for different tissues (e.g., grey matter, white matter, muscle, skin, etc.), where voxel intensity is proportional to the fraction of tissue within the voxel. The digital brain phantom can be used to simulate tomographic images of the head. Since the contribution of each tissue type to each voxel in the brain phantom is known, it can be used as the gold standard to test analysis algorithms such as classification procedures which seek to identify the tissue "type" of each image voxel. Furthermore, since the same anatomical phantom may be used to drive simulators for different modalities, it is the ideal tool to test intermodality registration algorithms. The brain phantom and simulated MR images have been made publicly available on the Internet (http://www.bic.mni.mcgill.ca/brainweb).
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Affiliation(s)
- D L Collins
- Montréal Neurological Institute, McGill University, McConnell Brain Imaging Centre, Canada.
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28
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Sled JG, Zijdenbos AP, Evans AC. A nonparametric method for automatic correction of intensity nonuniformity in MRI data. IEEE Trans Med Imaging 1998; 17:87-97. [PMID: 9617910 DOI: 10.1109/42.668698] [Citation(s) in RCA: 3318] [Impact Index Per Article: 127.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
A novel approach to correcting for intensity nonuniformity in magnetic resonance (MR) data is described that achieves high performance without requiring a model of the tissue classes present. The method has the advantage that it can be applied at an early stage in an automated data analysis, before a tissue model is available. Described as nonparametric nonuniform intensity normalization (N3), the method is independent of pulse sequence and insensitive to pathological data that might otherwise violate model assumptions. To eliminate the dependence of the field estimate on anatomy, an iterative approach is employed to estimate both the multiplicative bias field and the distribution of the true tissue intensities. The performance of this method is evaluated using both real and simulated MR data.
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Affiliation(s)
- J G Sled
- McConnell Brain Imaging Centre, Montréal Neurological Institute and McGill University, Canada.
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