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Palacios EM, Martin AJ, Boss MA, Ezekiel F, Chang YS, Yuh EL, Vassar MJ, Schnyer DM, MacDonald CL, Crawford KL, Irimia A, Toga AW, Mukherjee P. Toward Precision and Reproducibility of Diffusion Tensor Imaging: A Multicenter Diffusion Phantom and Traveling Volunteer Study. AJNR Am J Neuroradiol 2016; 38:537-545. [PMID: 28007768 DOI: 10.3174/ajnr.a5025] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Accepted: 10/10/2016] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Precision medicine is an approach to disease diagnosis, treatment, and prevention that relies on quantitative biomarkers that minimize the variability of individual patient measurements. The aim of this study was to assess the intersite variability after harmonization of a high-angular-resolution 3T diffusion tensor imaging protocol across 13 scanners at the 11 academic medical centers participating in the Transforming Research and Clinical Knowledge in Traumatic Brain Injury multisite study. MATERIALS AND METHODS Diffusion MR imaging was acquired from a novel isotropic diffusion phantom developed at the National Institute of Standards and Technology and from the brain of a traveling volunteer on thirteen 3T MR imaging scanners representing 3 major vendors (GE Healthcare, Philips Healthcare, and Siemens). Means of the DTI parameters and their coefficients of variation across scanners were calculated for each DTI metric and white matter tract. RESULTS For the National Institute of Standards and Technology diffusion phantom, the coefficients of variation of the apparent diffusion coefficient across the 13 scanners was <3.8% for a range of diffusivities from 0.4 to 1.1 × 10-6 mm2/s. For the volunteer, the coefficients of variations across scanners of the 4 primary DTI metrics, each averaged over the entire white matter skeleton, were all <5%. In individual white matter tracts, large central pathways showed good reproducibility with the coefficients of variation consistently below 5%. However, smaller tracts showed more variability, with the coefficients of variation of some DTI metrics reaching 10%. CONCLUSIONS The results suggest the feasibility of standardizing DTI across 3T scanners from different MR imaging vendors in a large-scale neuroimaging research study.
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Affiliation(s)
- E M Palacios
- From the Departments of Radiology and Biomedical Imaging (E.M.P., A.J.M., F.E., Y.S.C., E.L.Y., P.M.)
| | - A J Martin
- From the Departments of Radiology and Biomedical Imaging (E.M.P., A.J.M., F.E., Y.S.C., E.L.Y., P.M.)
| | - M A Boss
- National Institute of Standards and Technology (M.A.B.), Boulder, Colorado
| | - F Ezekiel
- From the Departments of Radiology and Biomedical Imaging (E.M.P., A.J.M., F.E., Y.S.C., E.L.Y., P.M.)
| | - Y S Chang
- From the Departments of Radiology and Biomedical Imaging (E.M.P., A.J.M., F.E., Y.S.C., E.L.Y., P.M.)
| | - E L Yuh
- From the Departments of Radiology and Biomedical Imaging (E.M.P., A.J.M., F.E., Y.S.C., E.L.Y., P.M.).,Brain and Spinal Cord Injury Center (E.L.Y., M.J.V., P.M.), San Francisco General Hospital and Trauma Center, San Francisco, California
| | - M J Vassar
- Neurological Surgery and Brain and Spinal Injury Center (M.J.V.).,Brain and Spinal Cord Injury Center (E.L.Y., M.J.V., P.M.), San Francisco General Hospital and Trauma Center, San Francisco, California
| | - D M Schnyer
- Department of Psychology (D.M.S.), University of Texas, Austin, Texas
| | - C L MacDonald
- Department of Neurological Surgery (C.L.M.), University of Washington, Seattle, Washington
| | - K L Crawford
- Mark and Mary Stevens Neuroimaging and Informatics Institute (K.L.C., A.I., A.W.T.), University of Southern California, Los Angeles, California
| | - A Irimia
- Mark and Mary Stevens Neuroimaging and Informatics Institute (K.L.C., A.I., A.W.T.), University of Southern California, Los Angeles, California
| | - A W Toga
- Mark and Mary Stevens Neuroimaging and Informatics Institute (K.L.C., A.I., A.W.T.), University of Southern California, Los Angeles, California
| | - P Mukherjee
- From the Departments of Radiology and Biomedical Imaging (E.M.P., A.J.M., F.E., Y.S.C., E.L.Y., P.M.) .,Bioengineering and Therapeutic Sciences (P.M.), University of California, San Francisco, San Francisco, California.,Brain and Spinal Cord Injury Center (E.L.Y., M.J.V., P.M.), San Francisco General Hospital and Trauma Center, San Francisco, California
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Abstract
BACKGROUND Although cardiac arrest (CA) is commonly cited as a cause of amnesia, patients referred to the authors' center with a diagnosis of "amnesia" after CA rarely have isolated memory deficits. OBJECTIVE To determine whether CA is a cause of pure amnesia and to assess patterns of cognitive deficits after CA. METHODS The authors used cognitive assessment of 11 consecutive patients referred for memory deficits after CA, targeted at deficit domains identified in the literature reviews, and analysis of specific case reports and prospective studies of cognition after CA. RESULTS The most common pattern of impairment in their patients was a combination of memory and motor deficits with variable executive impairment. No patient had isolated memory impairment. The case reports do not support the claim that isolated amnesia is a residual of CA; most cases of isolated amnesia are caused by subacute episodes of anoxia or excitotoxic injury. The prospective reports identify highly variable patterns of impairment, but isolated amnesia remains rare. CONCLUSIONS Diffuse, sudden ischemic-hypoxic injury caused by cardiac arrest (CA) does not preferentially damage memory systems. Subacute or stepwise hypoxic or excitotoxic injury may cause isolated hippocampal injury and amnesia. The common pattern of impairment in the postacute phase after CA is a combination of memory, subtle motor, and variable executive deficits.
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Affiliation(s)
- C Lim
- Behavioral Neurology Unit KS-2, Department of Neurology, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA.
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Schnyer DM, Allen JJ, Kaszniak AW, Forster KI. An event-related potential examination of masked and unmasked repetition priming in Alzheimer's disease: implications for theories of implicit memory. Neuropsychology 1999. [PMID: 10447295 DOI: 10.1037//0894-4105.13.3.323] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [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
Fifteen patients diagnosed with Alzheimer's disease (AD) and 26 matched older controls engaged in a lexical-decision task with a list of words and nonwords while event-related brain potentials (ERPs) were recorded. Two repetition conditions were embedded in the list: words repeated at relatively long lags or words repeated shortly after a brief masked presentation. Although older controls displayed behavioral and ERP repetition priming for words repeated at long lags, consistent with previous studies, AD patients displayed neither. In contrast, both controls and AD patients displayed an ERP repetition priming effect for words repeated shortly after a brief masked presentation. ERP priming effects for masked and unmasked repetition differed in older controls, and additionally, the ERP masked priming effect differed between controls and AD patients. Results are discussed in the context of studies that have examined memory performance in brain-damaged populations using an impaired-intact dichotomy.
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Affiliation(s)
- D M Schnyer
- Department of Psychology, University of Arizona, Tucson 85721, USA.
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Schnyer DM, Allen JJ, Kaszniak AW, Forster KI. An event-related potential examination of masked and unmasked repetition priming in Alzheimer's disease: implications for theories of implicit memory. Neuropsychology 1999; 13:323-37. [PMID: 10447295 DOI: 10.1037/0894-4105.13.3.323] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [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: 11/08/2022] Open
Abstract
Fifteen patients diagnosed with Alzheimer's disease (AD) and 26 matched older controls engaged in a lexical-decision task with a list of words and nonwords while event-related brain potentials (ERPs) were recorded. Two repetition conditions were embedded in the list: words repeated at relatively long lags or words repeated shortly after a brief masked presentation. Although older controls displayed behavioral and ERP repetition priming for words repeated at long lags, consistent with previous studies, AD patients displayed neither. In contrast, both controls and AD patients displayed an ERP repetition priming effect for words repeated shortly after a brief masked presentation. ERP priming effects for masked and unmasked repetition differed in older controls, and additionally, the ERP masked priming effect differed between controls and AD patients. Results are discussed in the context of studies that have examined memory performance in brain-damaged populations using an impaired-intact dichotomy.
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Affiliation(s)
- D M Schnyer
- Department of Psychology, University of Arizona, Tucson 85721, USA.
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Schnyer DM, Allen JJ, Forster KI. Event-related brain potential examination of implicit memory processes: masked and unmasked repetition priming. Neuropsychology 1997; 11:243-60. [PMID: 9110331 DOI: 10.1037/0894-4105.11.2.243] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [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: 02/04/2023] Open
Abstract
The proposition that cortically based perceptual representation systems (PRSs) are responsible for some implicit priming phenomena was examined by using event-related potentials (ERPs) in repetition and masked word priming. Experiment 1 used an explicit recognition task, in which repeated words replicated previous ERP repetition priming effects, whereas masked repetition priming revealed a new ERP effect with a posterior topography. Experiment 2 demonstrated ERP and behavioral priming in a lexical decision task for repetition and masked repetition priming. Topographical mapping of ERP repetition priming effects involved both early and late effects over the right and left anterior regions, whereas masked priming produced only an early ERP effect posteriorly. These results suggest differences between early and late ERP priming effects in terms of explicit recollection. Moreover, a posterior PRS may not be involved in some longer term implicit repetition priming effects.
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Affiliation(s)
- D M Schnyer
- Department of Psychology, University of Arizona, Tucson 85721, USA.
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Abstract
Higher frequency electroencephalographic (EEG) activity around 40 Hz has been shown to play a role in cognitive functions such as attention. Furthermore, event-related brain potential (ERP) components such as N1 and P1 are sensitive to selective attention. In the present study, 40-Hz EEG measures and early ERP components were employed to relate selective attention to hypnotic response. Participants were 20 low hypnotizable individuals, half assigned as simulators, and 21 high hypnotizable individuals. Each of these groups was subsequently divided into two groups based on recognition amnesia scores. The four groups differed in 40-Hz (36-44 Hz) EEG spectral amplitude recorded during preinduction resting conditions but not in EEG amplitude postinduction. The groups also differed in N1 amplitudes recorded during hypnosis. Regression analysis revealed that these effects only distinguish the high hypnotizable participants who experienced recognition amnesia from all other groups. The findings support the role of selective attention in hypnotic responsiveness, and the utility of subdividing high hypnotizable individuals is discussed.
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