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Wiggermann V, Endmayr V, Hernández‐Torres E, Höftberger R, Kasprian G, Hametner S, Rauscher A. Quantitative magnetic resonance imaging reflects different levels of histologically determined myelin densities in multiple sclerosis, including remyelination in inactive multiple sclerosis lesions. Brain Pathol 2023; 33:e13150. [PMID: 36720269 PMCID: PMC10580011 DOI: 10.1111/bpa.13150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 11/16/2022] [Indexed: 02/02/2023] Open
Abstract
Magnetic resonance imaging (MRI) of focal or diffuse myelin damage or remyelination may provide important insights into disease progression and potential treatment efficacy in multiple sclerosis (MS). We performed post-mortem MRI and histopathological myelin measurements in seven progressive MS cases to evaluate the ability of three myelin-sensitive MRI scans to distinguish different stages of MS pathology, particularly chronic demyelinated and remyelinated lesions. At 3 Tesla, we acquired two different myelin water imaging (MWI) scans and magnetisation transfer ratio (MTR) data. Histopathology included histochemical stainings for myelin phospholipids (LFB) and iron as well as immunohistochemistry for myelin proteolipid protein (PLP), CD68 (phagocytosing microglia/macrophages) and BCAS1 (remyelinating oligodendrocytes). Mixed-effects modelling determined which histopathological metric best predicted MWF and MTR in normal-appearing and diffusely abnormal white matter, active/inactive, inactive, remyelinated and ischemic lesions. Both MWI measures correlated well with each other and histology across regions, reflecting the different stages of MS pathology. MTR data showed a considerable influence of components other than myelin and a strong dependency on tissue storage duration. Both MRI and histology revealed increased myelin densities in inactive compared with active/inactive lesions. Chronic inactive lesions harboured single scattered myelin fibres indicative of low-level remyelination. Mixed-effects modelling showed that smaller differences between white matter areas were linked to PLP densities and only to a small extent confounded by iron. MWI reflects differences in myelin lipids and proteins across various levels of myelin densities encountered in MS, including low-level remyelination in chronic inactive lesions.
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Affiliation(s)
- Vanessa Wiggermann
- Department of Physics and AstronomyUniversity of British ColumbiaVancouverBritish ColumbiaCanada
- Department of PediatricsUniversity of British ColumbiaVancouverBritish ColumbiaCanada
- Danish Research Centre for Magnetic ResonanceCopenhagen University Hospital Amager & HvidovreCopenhagenDenmark
| | - Verena Endmayr
- Division of Neuropathology and Neurochemistry, Department of NeurologyMedical University of ViennaViennaAustria
- Centre for Brain ResearchMedical University of ViennaViennaAustria
| | - Enedino Hernández‐Torres
- Danish Research Centre for Magnetic ResonanceCopenhagen University Hospital Amager & HvidovreCopenhagenDenmark
- Faculty of Medicine (Division Neurology)University of British ColumbiaVancouverBritish ColumbiaCanada
| | - Romana Höftberger
- Division of Neuropathology and Neurochemistry, Department of NeurologyMedical University of ViennaViennaAustria
| | - Gregor Kasprian
- Department of Biomedical Imaging and Image‐Guided TherapyMedical University of ViennaViennaAustria
| | - Simon Hametner
- Division of Neuropathology and Neurochemistry, Department of NeurologyMedical University of ViennaViennaAustria
- Centre for Brain ResearchMedical University of ViennaViennaAustria
| | - Alexander Rauscher
- Department of Physics and AstronomyUniversity of British ColumbiaVancouverBritish ColumbiaCanada
- Department of PediatricsUniversity of British ColumbiaVancouverBritish ColumbiaCanada
- Department of RadiologyUniversity of British ColumbiaVancouverBritish ColumbiaCanada
- BC Children's Hospital Research InstituteUniversity of British ColumbiaVancouverBritish ColumbiaCanada
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Shi D, Xu S, Zhuo J, McKenna MC, Gullapalli RP. White Matter Alterations in Fmr1 Knockout Mice during Early Postnatal Brain Development. Dev Neurosci 2020; 41:274-289. [PMID: 32348987 DOI: 10.1159/000506679] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 02/19/2020] [Indexed: 01/20/2023] Open
Abstract
Fragile X syndrome (FXS) is the most commonly inherited form of intellectual disability ascribed to the autism spectrum disorder. Studies with FXS patients have reported altered white matter volume compared to controls. The Fmr1 knockout (KO) mouse, a model for FXS, showed evidence of delayed myelination during postnatal brain development. In this study, we examined several white matter regions in the male Fmr1 KO mouse brain compared to male wild-type (WT) mice at postnatal days (PND) 18, 21, 30, and 60, which coincide with critical stages of myelination and postnatal brain development. White matter volume, T2 relaxation time, and magnetization transfer ratio (MTR) were measured using magnetic resonance imaging and myelin content was determined with histological staining of myelin. Differences in the developmental accumulation of white matter and myelin between Fmr1 KO and WT mice were observed in the corpus callosum, external and internal capsules, cerebral peduncle, and fimbria. Alterations were more predominant in the external and internal capsules and fimbria of Fmr1 KO mice, where the MTR was lower at PND 18, then elevated at PND 30, and again lower at PND 60 compared to the corresponding regions in WT mice. The pattern of changes in MTR were similar to those observed in myelin staining and could be related to the altered protein synthesis that is a hallmark of FXS. While no significant changes in white matter volumes and T2 relaxation time between the Fmr1 KO and WT mice were observed, the altered pattern of myelin staining and MTR, particularly in the external capsule, reflecting the abnormalities associated with myelin content is suggestive of a developmental delay in the white matter of Fmr1 KO mouse brain. These early differences in white matter during critical developmental stages may contribute to altered brain networks in the Fmr1 KO mice.
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Affiliation(s)
- Da Shi
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA.,Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Su Xu
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Jiachen Zhuo
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Mary C McKenna
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland, USA.,Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Rao P Gullapalli
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA, .,Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, USA, .,Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, USA,
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Helms G, Dathe H, Dechent P. Modeling the influence of TR and excitation flip angle on the magnetization transfer ratio (MTR) in human brain obtained from 3D spoiled gradient echo MRI. Magn Reson Med 2010; 64:177-85. [DOI: 10.1002/mrm.22379] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Abstract
We introduce the fundamental aspects of MT, of MT MR imaging, and the respective analysis techniques. We then review the applications of MT MR imaging to multiple sclerosis. Finally we review the technique's contribution to our understanding of this disease.
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Affiliation(s)
- Stefan Ropele
- Department of Neurology, Medical University Graz, Auenbruggerplatz 22, A-8036 Graz, Austria.
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Cercignani M, Symms MR, Schmierer K, Boulby PA, Tozer DJ, Ron M, Tofts PS, Barker GJ. Three-dimensional quantitative magnetisation transfer imaging of the human brain. Neuroimage 2005; 27:436-41. [PMID: 15978842 DOI: 10.1016/j.neuroimage.2005.04.031] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2005] [Revised: 04/01/2005] [Accepted: 04/05/2005] [Indexed: 11/21/2022] Open
Abstract
Quantitative magnetisation transfer (MT) analysis is based on a two-pool model of magnetisation transfer and allows important physical properties of the two proton pools to be assessed. A good signal-to-noise ratio (SNR) for the measured signal is essential in order to estimate reliably the parameters from a small number of samples, thus prompting the use of a sequence with high SNR, such as a three-dimensional spoiled gradient acquisition. Here, we show how full brain coverage can be accomplished efficiently, using a three-dimensional acquisition, in a clinically acceptable time, and without the use of large numbers of slice-selective radio-frequency pulses which could otherwise confound analysis. This acquisition was first compared in post mortem human brain tissue to established two-dimensional acquisition protocols with differing SNR levels and then used to collect data from six healthy subjects. Image data were fitted using the two pool model and showed negligible residual deviations. Quantitative results were assessed in several brain locations. Results were consistent with previous single-slice data, and parametric maps were of good quality. Further investigations are needed to interpret the regional variation of quantitative MT quantities.
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Affiliation(s)
- Mara Cercignani
- Department of Neuroinflammation, NMR Research Unit, Institute of Neurology, University College London, London WC1N 3 BG, UK.
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Reidel MA, Stippich C, Heiland S, Storch-Hagenlocher B, Jansen O, Hähnel S. Differentiation of multiple sclerosis plaques, subacute cerebral ischaemic infarcts, focal vasogenic oedema and lesions of subcortical arteriosclerotic encephalopathy using magnetisation transfer measurements. Neuroradiology 2003; 45:289-94. [PMID: 12700877 DOI: 10.1007/s00234-003-0991-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2003] [Accepted: 03/05/2003] [Indexed: 10/20/2022]
Abstract
Although multiple sclerosis (MS) plaques, subacute cerebral ischaemic infarcts, focal vasogenic brain oedema, and subcortical arteriosclerotic encephalopathy (SAE) often have typical radiological patterns, they are sometimes difficult to distinguish from each other. Our aim was to determine whether they can be differentiated by magnetisation transfer (MT) measurements. We measured MT ratios (MTR) in ten patients with plaques of MS, 11 with subacute ischaemic infarcts, 12 with focal vasogenic oedema, and ten with lesions of SAE and compared the mean MTRs statistically. The MTR of normal white matter was 47.3%; the lowest MTR was found in plaques of MS (mean 26.4%). With the exception of vasogenic oedema and subacute cerebral ischaemic infarcts the mean MTRs were significantly different between all groups. MT measurements can provide additional information for the differentiation of these conditions, but we could not distinguish vasogenic oedema from subacute cerebral ischaemic infarcts.
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Affiliation(s)
- M A Reidel
- Division of Neuroradiology, Department of Neurology, University of Heidelberg Medical Centre, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany
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Jost G, Hähnel S, Heiland S, Stippich C, Bellemann ME, Sartor K. An automated method for volumetric quantification of magnetization transfer of the brain. Magn Reson Imaging 2002; 20:593-7. [PMID: 12467866 DOI: 10.1016/s0730-725x(02)00590-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Cerebral white matter damages can be detected and characterized using magnetization transfer (MT) imaging. In this study a fully automated method of measuring and analyzing the MT of the whole human brain is presented and assessed. A 3D-FLASH sequence with off-resonance RF pulse was optimized for fast, volumetric MT measurements. The postprocessing software developed for this purpose includes a SPM99-based segmentation algorithm, a visualization tool, and a histogram-based MT parameter analysis. The reproducibility of the method was tested with phantom measures and in studies on nine healthy volunteers. Small variances (0-1.6%) and therefore, a high reproducibility of MT parameter measurements were found in vitro, slightly higher variances in volunteer investigations (0.7-4.0%). With our technique, we expect to be able to better recognize and follow up the progression of white matter diseases. Due to the high reproducibility, this volumetric approach is specifically suitable for longitudinal MT studies.
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Affiliation(s)
- Gregor Jost
- Department of Neuroradiology, University of Heidelberg Medical School, Germany.
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Rumpel H, Ho GL, Chan LL, Lim WEH, Chong VFH. Concomitant diminishing magnetization-transfer effect and increasing choline level in radiation-induced temporal-lobe changes. AUSTRALASIAN RADIOLOGY 2002; 46:340-4. [PMID: 12196251 DOI: 10.1046/j.1440-1673.2002.01034.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This article reports on the use of both magnetization-transfer (MT) imaging and 1H-MR spectroscopy in two cases of bilateral temporal-lobe changes after radiation therapy for nasopharyngeal carcinoma. In the first case, the following patterns were noted: (i) although the temporal lobes appeared relatively normal on T2-weighted MR imaging, corresponding MT imaging clearly showed signal abnormalities (decreased MT effect) consistent with alterations in macromolecular structure; and (ii) concomitant strongly elevated choline on 1H-MR spectroscopy was observed, and this is associated with metabolic changes in cell membranes. The second case presented similar characteristics. In addition, there was an increased lactate signal and T2 signal changes in keeping with established oedema. Both MT and proton-spectroscopic findings were consistent with postulated pathophysiological features of radiation injury, but their specificity for this condition remains unclear. Magnetization-transfer imaging, and possibly 1H-MR spectroscopy, might be sensitive techniques for the early detection of late radiation injury.
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Affiliation(s)
- Helmut Rumpel
- Department of Diagnostic Radiology, Singapore General Hospital, Singapore.
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Abstract
With use of an established physical model, numeric simulations were performed to evaluate current imaging protocols for the two primary applications of magnetization transfer: cerebral magnetic resonance angiography and neuroimaging of white matter disease. The authors found that the current technique is appropriate in the former but suboptimal in the latter. Further clinical investigations could potentially improve magnetization protocols for neuroimaging.
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Affiliation(s)
- S J Graham
- Department of Medical Biophysics, University of Toronto, Ontario, Canada.
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Hähnel S, Münkel K, Jansen O, Heiland S, Reidel M, Freund M, Aschoff A, Sartor K. Magnetization transfer measurements in normal-appearing cerebral white matter in patients with chronic obstructive hydrocephalus. J Comput Assist Tomogr 1999; 23:516-20. [PMID: 10433276 DOI: 10.1097/00004728-199907000-00004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE The purpose of this work was to assess the presence of subtle changes in normal-appearing white matter on T2-weighted MR images in patients with chronic obstructive hydrocephalus using magnetization transfer (MT) measurements. METHOD In 12 patients with chronic obstructive hydrocephalus, MT ratios (MTRs) of normal-appearing rostral (PR) and caudal (PC) periventricular white matter, of the genu (CG) and the splenium (CS) of the corpus callosum, and of the thalamus (TH) were measured and compared with those of 16 healthy control subjects. RESULTS We found a significantly lower MTR in chronic obstructive hydrocephalus than in the normal group for PR, PC, CG, and CS but not for TH. CONCLUSION Our study shows that MT measurements give additional information that cannot be gained by conventional SE MRI, suggesting that chronic obstructive hydrocephalus is associated with diffuse white matter damage that also affects normal-appearing cerebral white matter.
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Affiliation(s)
- S Hähnel
- Department of Neuroradiology, University of Heidelberg Medical School, Germany
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Hanyu H, Asano T, Sakurai H, Iwamoto T, Takasaki M, Shindo H, Abe K. Magnetization transfer ratio in cerebral white matter lesions of Binswanger's disease. J Neurol Sci 1999; 166:85-90. [PMID: 10475100 DOI: 10.1016/s0022-510x(99)00122-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We measured the magnetization transfer (MT) ratios in white matter lesions of Binswanger's disease (BD) and compared them with BD and with similar-appearing changes in non-demented elderly subjects and cerebral infarction. Four subject groups were studied: 30 patients with BD and periventricular hyperintensity (PVH) on MRI, 29 patients with ischemic cerebrovascular event with PVH but no dementia, 17 patients with old cerebral infarction, and 26 elderly control subjects. MT ratios were calculated for areas of PVH in BD and non-demented subjects, of infarction, and of normal-appearing white matter in controls. The decrease in MT ratios for areas in PVH of non-demented subjects and BD and in infarction compared with normal white matter in controls was 12, 20, and 35%, respectively. The MT ratio in PVH of BD was significantly lower than that in PVH of non-demented subjects, but not to the levels seen in areas of infarction. There was a significant high correlation between the Mini-Mental State Examination score and MT ratio for area of PVH (r = 0.790). MT ratio distinguishes PVH in BD patients from those in non-demented subjects, suggesting underlying histopathological differences. Tissue damage in white matter lesions of BD may be more severe than that in non-demented subjects, but not as much as with complete infarction.
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Affiliation(s)
- H Hanyu
- Department of Geriatric Medicine, Tokyo Medical University, Japan
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Berry I, Barker GJ, Barkhof F, Campi A, Dousset V, Franconi JM, Gass A, Schreiber W, Miller DH, Tofts PS. A multicenter measurement of magnetization transfer ratio in normal white matter. J Magn Reson Imaging 1999; 9:441-6. [PMID: 10194715 DOI: 10.1002/(sici)1522-2586(199903)9:3<441::aid-jmri12>3.0.co;2-r] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
To assess the importance of intercenter variations when measuring magnetization transfer ratio (MTR) in the brain, six European centers measured MTR in normal white matter. MTR ranged from 9 to 51 percent units (25 sequences). The effective flip angle of the saturating pulse divided by the pulse repetition time (ENRsat degrees/msec) was a good predictor of MTR (MTR = 3.25 ENRsat).
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Affiliation(s)
- I Berry
- Service de Neuroradiologie, University Hospitals, Toulouse, France
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Abstract
RATIONALE AND OBJECTIVES The effects of magnetic relaxation agents are explored in the context of magnetization transfer pulse sequences using cross-linked protein gels as modeled tissue systems. METHODS Magnetization transfer pulse sequences were used to study contrast agents that are designed to bind to rotationally immobilized protein targets. RESULTS The dynamic range available from contrast agents, used in conjunction with magnetization transfer pulse sequences, is comparable with or better than that based on spin-echo imaging sequences with short repetition times. Furthermore, useful changes in the intensity of water resonances may be achieved by using this combined approach even though the paramagnetic metal center may not have a free coordination position in the chelate complex for water molecule exchange. CONCLUSIONS The inclusion of magnetization transfer acquisition protocols in the context of magnetic imaging with contrast agents presents new opportunities for control of the information content of the image and for new classes of contrast agent structure and delivery.
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Affiliation(s)
- A N Danek
- Chemistry Department, University of Virginia, Charlottesville, USA
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Finelli DA, Reed DR. Flip angle dependence of experimentally determined T1sat and apparent magnetization transfer rate constants. J Magn Reson Imaging 1998; 8:548-53. [PMID: 9626867 DOI: 10.1002/jmri.1880080306] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The purpose of this work was to develop a method for determining the T1sat and magnetization transfer (MT) rate constants by analyzing the slice-select flip angle dependent MT behavior of normal white and gray matter. The technique uses a high MT power, three-dimensional (3D) gradient-recalled echo (GRE) sequence, with a well chosen MT pulse frequency offset, such that the experimental conditions closely satisfy requisite assumptions for invoking a first order rate process for MT. Integral to this method is that the T1sat and MT ratio values are obtained under explicitly identical MT saturation conditions. The T1sat of white matter was found to be approximately 300 msec, and the MT rate constant was approximately 2.0 sec(-1). The T1sat of gray matter was approximately 500 msec, and the MT rate constant was 1.1 sec(-1). We also found a strong dependence of the MT rate constant on the slice-select flip angle used for the imaging sequence, independent of the MT saturation parameters. Strongly T1-weighted imaging sequences can result in the underestimation of the MT rate constant by 50%. Practical technical suggestions for quantitative MT experiments are put forth.
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Affiliation(s)
- D A Finelli
- Department of Radiology, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, OH 44109-1998, USA
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Abstract
Using a two-pool exchange model of magnetization transfer (MT), numeric simulations were developed to predict the time dependence of longitudinal magnetization in both semisolid and liquid pools for arbitrary pulsed radiofrequency (RF) irradiation. Whereas RF excitation of the liquid pool was modeled using the time-dependent Bloch equations, RF saturation of the semisolid pool was described by a time-dependent rate proportional to both the absorption lineshape of the semisolid pool and the square of the RF pulse amplitude. Simulations show good agreement with experimental results for a 4% agar gel aqueous system in which the two-pool kinetics have been well studied previously. These simulations provide a method for interpreting pulsed MT effects, are easily extended to biologic tissues, and provide a basis for optimizing clinical imaging applications that exploit MT contrast.
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Affiliation(s)
- S J Graham
- Department of Medical Biophysics, University of Toronto, Sunnybrook Health Science Centre, Ontario, Canada.
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Mitchell JR, Jones C, Karlik SJ, Kennedy K, Lee DH, Rutt B, Fenster A. MR multispectral analysis of multiple sclerosis lesions. J Magn Reson Imaging 1997; 7:499-511. [PMID: 9170034 DOI: 10.1002/jmri.1880070309] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Although quantification of the lesion burden from serial MR examinations of patients with multiple sclerosis (MS) is a common technique to assess disease activity in clinical trials, pathologic change may occur within a lesion without a corresponding change in volume. Therefore, measures of lesion volume and composition may improve the sensitivity of detecting disease activity. A new technique has been developed that provides information about the intensity composition of MS lesions in standard spin-echo MR examinations. The new technique is based on the multispectral "feature space" intensity distributions of the lesions and normal tissues. Analysis of MR examinations of materials with known T1 and T2 times showed that feature space position from spin-echo examinations is largely determined from proton density (rho), T2, and the interecho delay. Information about intensity composition was obtained by reducing the multidimensional intensity distribution to one dimension while minimizing the loss of information. This technique was used to analyze eight lesions in standard spin-echo MR examinations of three patients with MS. Lesion distributions were compared between examinations by first calibrating the examinations based on the intensity distributions of cerebrospinal fluid (CSF), an internal reference tissue. Many of the lesion distributions had a distinctive peak at low intensity, corresponding to normal-appearing white matter (WM). Within the lesion distributions, increases in high intensity peaks generally were accompanied by reductions in the WM peak. Serial analysis of the lesion distributions revealed some dramatic fluctuations, even when lesion volume remained constant.
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Affiliation(s)
- J R Mitchell
- Department of Diagnostic Radiology and Nuclear Medicine, University of Western Ontario, London, Canada
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