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Ishii Y, Thamm T, Guo J, Khalighi MM, Wardak M, Holley D, Gandhi H, Park JH, Shen B, Steinberg GK, Chin FT, Zaharchuk G, Fan AP. Simultaneous phase-contrast MRI and PET for noninvasive quantification of cerebral blood flow and reactivity in healthy subjects and patients with cerebrovascular disease. J Magn Reson Imaging 2019; 51:183-194. [PMID: 31044459 DOI: 10.1002/jmri.26773] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [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: 12/11/2018] [Revised: 04/16/2019] [Accepted: 04/18/2019] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND H2 15 O-positron emission tomography (PET) is considered the reference standard for absolute cerebral blood flow (CBF). However, this technique requires an arterial input function measured through continuous sampling of arterial blood, which is invasive and has limitations with tracer delay and dispersion. PURPOSE To demonstrate a new noninvasive method to quantify absolute CBF with a PET/MRI hybrid scanner. This blood-free approach, called PC-PET, takes the spatial CBF distribution from a static H2 15 O-PET scan, and scales it to the whole-brain average CBF value measured by simultaneous phase-contrast MRI. STUDY TYPE Observational. SUBJECTS Twelve healthy controls (HC) and 13 patients with Moyamoya disease (MM) as a model of chronic ischemic disease. FIELD STRENGTH/SEQUENCES 3T/2D cardiac-gated phase-contrast MRI and H2 15 O-PET. ASSESSMENT PC-PET CBF values from whole brain (WB), gray matter (GM), and white matter (WM) in HCs were compared with literature values since 2000. CBF and cerebrovascular reactivity (CVR), which is defined as the percent CBF change between baseline and post-acetazolamide (vasodilator) scans, were measured by PC-PET in MM patients and HCs within cortical regions corresponding to major vascular territories. Statistical Tests: Linear, mixed effects models were created to compare CBF and CVR, respectively, between patients and controls, and between different degrees of stenosis. RESULTS The mean CBF values in WB, GM, and WM in HC were 42 ± 7 ml/100 g/min, 50 ± 7 ml/100 g/min, and 23 ± 3 ml/100 g/min, respectively, which agree well with literature values. Compared with normal regions (57 ± 23%), patients showed significantly decreased CVR in areas with mild/moderate stenosis (47 ± 17%, P = 0.011) and in severe/occluded areas (40 ± 16%, P = 0.016). Data Conclusion: PC-PET identifies differences in cerebrovascular reactivity between healthy controls and cerebrovascular patients. PC-PET is suitable for CBF measurement when arterial blood sampling is not accessible, and warrants comparison to fully quantitative H2 15 O-PET in future studies. LEVEL OF EVIDENCE 3 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2020;51:183-194.
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Affiliation(s)
- Yosuke Ishii
- Department of Radiology, Stanford University, Stanford, California, USA.,Department of Neurosurgery, Tokyo Medical and Dental University, Tokyo, Japan
| | - Thoralf Thamm
- Department of Radiology, Stanford University, Stanford, California, USA.,Center for Stroke Research Berlin (CSB), Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jia Guo
- Department of Radiology, Stanford University, Stanford, California, USA.,Department of Bioengineering, University of California Riverside, Riverside, California, USA
| | | | - Mirwais Wardak
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Dawn Holley
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Harsh Gandhi
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Jun Hyung Park
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Bin Shen
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Gary K Steinberg
- Department of Neurosurgery, Stanford University, Stanford, California, USA
| | - Frederick T Chin
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Greg Zaharchuk
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Audrey Peiwen Fan
- Department of Radiology, Stanford University, Stanford, California, USA
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Kogan F, Fan AP, Monu U, Iagaru A, Hargreaves BA, Gold GE. Quantitative imaging of bone-cartilage interactions in ACL-injured patients with PET-MRI. Osteoarthritis Cartilage 2018; 26:790-796. [PMID: 29656143 PMCID: PMC6037170 DOI: 10.1016/j.joca.2018.04.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 02/10/2018] [Accepted: 04/04/2018] [Indexed: 02/07/2023]
Abstract
OBJECTIVE To investigate changes in bone metabolism by positron emission tomography (PET), as well as spatial relationships between bone metabolism and magnetic resonance imaging (MRI) quantitative markers of early cartilage degradation, in anterior cruciate ligament (ACL)-reconstructed knees. DESIGN Both knees of 15 participants with unilateral reconstructed ACL tears and unaffected contralateral knees were scanned using a simultaneous 3.0T PET-MRI system following injection of 18F-sodium fluoride (18F-NaF). The maximum pixel standardized uptake value (SUVmax) in the subchondral bone and the average T2 relaxation time in cartilage were measured in each knee in eight knee compartments. We tested differences in SUVmax and cartilage T2 relaxation times between the ACL-injured knee and the contralateral control knee as well as spatial relationships between these bone and cartilage changes. RESULTS Significantly increased subchondral bone 18F-NaF SUVmax and cartilage T2 times were observed in the ACL-reconstructed knees (median [inter-quartile-range (IQR)]: 5.0 [5.8], 36.8 [3.6] ms) compared to the contralateral knees (median [IQR]: 1.9 [1.4], 34.4 [3.8] ms). A spatial relationship between the two markers was also seen. Using the contralateral knee as a control, we observed a significant correlation of r = 0.59 between the difference in subchondral bone SUVmax (between injured and contralateral knees) and the adjacent cartilage T2 (between the two knees) [P < 0.001], with a slope of 0.49 ms/a.u. This correlation and slope were higher in deep layers (r = 0.73, slope = 0.60 ms/a.u.) of cartilage compared to superficial layers (r = 0.40, slope = 0.43 ms/a.u.). CONCLUSIONS 18F-NaF PET-MR imaging enables detection of increased subchondral bone metabolism in ACL-reconstructed knees and may serve as an important marker of early osteoarthritis (OA) progression. Spatial relationships observed between early OA changes across bone and cartilage support the need to study whole-joint disease mechanisms in OA.
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Affiliation(s)
- F Kogan
- Department of Radiology, Stanford University, Stanford, CA, USA.
| | - A P Fan
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - U Monu
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - A Iagaru
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - B A Hargreaves
- Department of Radiology, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA; Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - G E Gold
- Department of Radiology, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA; Department of Orthopaedic Surgery, Stanford University, Stanford, CA, USA
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Khalighi MM, Deller TW, Fan AP, Gulaka PK, Shen B, Singh P, Park JH, Chin FT, Zaharchuk G. Image-derived input function estimation on a TOF-enabled PET/MR for cerebral blood flow mapping. J Cereb Blood Flow Metab 2018; 38:126-135. [PMID: 28155582 PMCID: PMC5757438 DOI: 10.1177/0271678x17691784] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 01/04/2017] [Accepted: 01/10/2017] [Indexed: 11/15/2022]
Abstract
15O-H2O PET imaging is an accurate method to measure cerebral blood flow (CBF) but it requires an arterial input function (AIF). Historically, image-derived AIF estimation suffers from low temporal resolution, spill-in, and spill-over problems. Here, we optimized tracer dose on a time-of-flight PET/MR according to the acquisition-specific noise-equivalent count rate curve. An optimized dose of 850 MBq of 15O-H2O was determined, which allowed sufficient counts to reconstruct a short time-frame PET angiogram (PETA) during the arterial phase. This PETA enabled the measurement of the extent of spill-over, while an MR angiogram was used to measure the true arterial volume for AIF estimation. A segment of the high cervical arteries outside the brain was chosen, where the measured spill-in effects were minimal. CBF studies were performed twice with separate [15O]-H2O injections in 10 healthy subjects, yielding values of 88 ± 16, 44 ± 9, and 58 ± 11 mL/min/100 g for gray matter, white matter, and whole brain, with intra-subject CBF differences of 5.0 ± 4.0%, 4.1 ± 3.3%, and 4.5 ± 3.7%, respectively. A third CBF measurement after the administration of 1 g of acetazolamide showed 35 ± 23%, 29 ± 20%, and 33 ± 22% increase in gray matter, white matter, and whole brain, respectively. Based on these findings, the proposed noninvasive AIF method provides robust CBF measurement with 15O-H2O PET.
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Affiliation(s)
| | | | | | | | - Bin Shen
- Radiology Department, Stanford University, Stanford, CA, USA
| | - Prachi Singh
- Radiology Department, Stanford University, Stanford, CA, USA
| | - Jun-Hyung Park
- Molecular Imaging Program, Stanford University, Stanford, CA, USA
| | - Frederick T Chin
- Radiology Department, Stanford University, Stanford, CA, USA
- Molecular Imaging Program, Stanford University, Stanford, CA, USA
| | - Greg Zaharchuk
- Radiology Department, Stanford University, Stanford, CA, USA
- Molecular Imaging Program, Stanford University, Stanford, CA, USA
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Langkammer C, Bredies K, Poser BA, Barth M, Reishofer G, Fan AP, Bilgic B, Fazekas F, Mainero C, Ropele S. Fast quantitative susceptibility mapping using 3D EPI and total generalized variation. Neuroimage 2015; 111:622-30. [PMID: 25731991 DOI: 10.1016/j.neuroimage.2015.02.041] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [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: 09/03/2014] [Revised: 02/02/2015] [Accepted: 02/20/2015] [Indexed: 01/21/2023] Open
Abstract
Quantitative susceptibility mapping (QSM) allows new insights into tissue composition and organization by assessing its magnetic property. Previous QSM studies have already demonstrated that magnetic susceptibility is highly sensitive to myelin density and fiber orientation as well as to para- and diamagnetic trace elements. Image resolution in QSM with current approaches is limited by the long acquisition time of 3D scans and the need for high signal to noise ratio (SNR) to solve the dipole inversion problem. We here propose a new total-generalized-variation (TGV) based method for QSM reconstruction, which incorporates individual steps of phase unwrapping, background field removal and dipole inversion in a single iteration, thus yielding a robust solution to the reconstruction problem. This approach has beneficial characteristics for low SNR data, allowing for phase data to be rapidly acquired with a 3D echo planar imaging (EPI) sequence. The proposed method was evaluated with a numerical phantom and in vivo at 3 and 7 T. Compared to total variation (TV), TGV-QSM enforced higher order smoothness which yielded solutions closer to the ground truth and prevented stair-casing artifacts. The acquisition time for images with 1mm isotropic resolution and whole brain coverage was 10s on a clinical 3 Tesla scanner. In conclusion, 3D EPI acquisition combined with single-step TGV reconstruction yields reliable QSM images of the entire brain with 1mm isotropic resolution in seconds. The short acquisition time combined with the robust reconstruction may enable new QSM applications in less compliant populations, clinical susceptibility tensor imaging, and functional resting state examinations.
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Affiliation(s)
- Christian Langkammer
- MGH Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Boston, MA, USA; Department of Neurology, Medical University of Graz, Graz, Austria.
| | - Kristian Bredies
- Institute of Mathematics and Scientific Computing, University of Graz, Graz, Austria
| | - Benedikt A Poser
- Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Markus Barth
- Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia
| | - Gernot Reishofer
- Department of Radiology, Division of Neuroradiology, Medical University of Graz, Graz, Austria
| | - Audrey Peiwen Fan
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA; Lucas Center for Imaging, Stanford University, Stanford, CA, USA
| | - Berkin Bilgic
- MGH Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Boston, MA, USA
| | - Franz Fazekas
- Department of Neurology, Medical University of Graz, Graz, Austria
| | - Caterina Mainero
- MGH Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Boston, MA, USA
| | - Stefan Ropele
- Department of Neurology, Medical University of Graz, Graz, Austria
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Fan AP, Tran DT, Mandell GA, Su TP, Chiu AW, Kosik RO, Tsai TC, Morisky DE. The contribution of international medical students to Taiwanese medical school classes. Med Teach 2012; 35:78-79. [PMID: 22992023 DOI: 10.3109/0142159x.2012.716560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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Abstract
BACKGROUND Vietnam is one of the most populous countries in Southeast Asia, yet it displays an unsettling lack of doctors. AIMS Medical education is an important factor contributing to this issue, yet little is known about the system currently in place in Vietnam. METHODS Through an extensive literary search of medical schools' and Ministry of Health's data, we have examined the current medical education system in Vietnam. RESULTS At present, there are 12 medical universities, and the general curriculum at each university follows a national framework but tends to vary from university to university. Medical training lasts either 4 or 6 years, with competitive graduates attending residency programs following graduation. While examinations are required to graduate, the lack of a national licensing exam makes it difficult to ensure that a nation-wide standard of quality exists, both at the medical universities themselves as well as amongst the doctors graduating from them. CONCLUSIONS The development and institution of a national exam would introduce a standard of training throughout Vietnam's medical education system. Further, a substantial portion of a doctor's education is in subjects that are loosely related to medicine. When looking forward it will be important to evaluate whether or not these non-medical subjects detract from the quality of medical training.
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Affiliation(s)
- A P Fan
- Faculty of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC.
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Fan AP, Lee FY, Hou MC, Chen CH, Lee CH, Kosik RO, Tang W, Chen Q. Teaching faculty to teach: a new approach to global awareness. Med Teach 2011; 33:425-426. [PMID: 21671506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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Fan AP, Su TP, Chen YA, Chen CH, Lee CH, Tang W, Chen Q, Guo L, Kosik RO. Humanities and ethics education at Chinese medical schools. Med Teach 2011; 33:87. [PMID: 21226234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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Fan AP, Kosik RO, Su TP, Lee FY, Hou MC, Chen YA, Chen CH, Lee CH. Factors associated with suicidal ideation in Taiwanese medical students. Med Teach 2011; 33:256-257. [PMID: 21452403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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Fan AP, Chen CH, Ho LT. Interacting factors of students' perceptions on an effective curriculum. Med Educ 2004; 38:1196-1197. [PMID: 15507031 DOI: 10.1111/j.1365-2929.2004.02007.x] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
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Fan AP, Eaton WW. Longitudinal study assessing the joint effects of socio-economic status and birth risks on adult emotional and nervous conditions. Br J Psychiatry Suppl 2001; 40:s78-83. [PMID: 11315230 DOI: 10.1192/bjp.178.40.s78] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [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: 11/23/2022]
Abstract
BACKGROUND Previous investigations into the impact of birth complications and social environment have generally followed their subjects only at young ages. AIMS To assess the long-range impact of socio-economic status (SES) and birth risks on the development of emotional and nervous conditions through adulthood. METHOD The Johns Hopkins Pathways Study interviewed 1824 subjects born between 1960 and 1965. The median household income of the children at age 7-8 years was used to divide the cohort into high and low income categories. Differences in life time prevalence of emotional and nervous conditions through adulthood between the two income groups were identified. RESULTS Children in the lower income group were 1.86 times more likely to report an emotional or nervous condition as adults. Boys in the lower income group at age 7-8 years were 3.2 times more likely to do so. The risks of difficult birth for adult mental disturbance were accentuated in the low-income group. CONCLUSIONS Children who experience birth complications are at increased risk of developing adult mental disturbances; this increase is mitigated by higher SES.
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Affiliation(s)
- A P Fan
- Department of Mental Hygiene, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland, USA.
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Abstract
This paper presents an overview of the recent literature on the association between prenatal and perinatal complications (PPCs) and schizophrenia, then systematically reviews papers published later than 1965 examining the association of PPCs and bipolar disorder. Three of the four studies comparing bipolar cases with normal controls indicated a positive association of PPCs with the development of bipolar disorder in adult life; the four odds ratios ranged from 1.0 to 12.0. The proportion of PPCs among the bipolar samples without comparison subjects ranged from 3.8% to 50.0%. Issues of study design, measurement and severity of exposure, and outcome are addressed. This review suggests that further investigation of genetic interactions, gender differences, and the specificity of effects in the association between PPCs and mental disorders other than schizophrenia is warranted.
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Affiliation(s)
- S L Buka
- Department of Maternal and Child Health, Harvard School of Public Health, Boston, MA 02115, USA.
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