title: Inversion recovery ultrashort echo time magnetic resonance imaging: A method for simultaneous direct detection of myelin and high signal demonstration of iron deposition in the brain - A feasibility study.
abstract: Multiple sclerosis (MS) causes demyelinating lesions in the white matter and increased iron deposition in the subcortical gray matter. Myelin protons have an extremely short T2* (<1ms) and are not directly detected with conventional clinical magnetic resonance (MR) imaging sequences. Iron deposition also reduces T2*, leading to reduced signal on clinical sequences. In this study we tested the hypothesis that the inversion recovery ultrashort echo time (IR-UTE) pulse sequence can directly and simultaneously image myelin and iron deposition using a clinical 3T scanner. The technique was first validated on a synthetic myelin phantom (myelin powder in D2O) and a Feridex iron phantom. This was followed by studies of cadaveric MS specimens, healthy volunteers and MS patients. UTE imaging of the synthetic myelin phantom showed an excellent bi-component signal decay with two populations of protons, one with a T2* of 1.2ms (residual water protons) and the other with a T2* of 290μs (myelin protons). IR-UTE imaging shows sensitivity to a wide range of iron concentrations from 0.5 to ~30mM. The IR-UTE signal from white matter of the brain of healthy volunteers shows a rapid signal decay with a short T2* of ~300μs, consistent with the T2* values of myelin protons in the synthetic myelin phantom. IR-UTE imaging in MS brain specimens and patients showed multiple white matter lesions as well as areas of high signal in subcortical gray matter. This in specimens corresponded in position to Perl's diaminobenzide staining results, consistent with increased iron deposition. IR-UTE imaging simultaneously detects lesions with myelin loss in the white matter and iron deposition in the gray matter.
authors.affiliation: Department of Radiology, University of California, San Diego, CA, United States.
authors.forename: Vipul R
authors.initials: VR
authors.lastname: Sheth
authors.affiliation: Department of Radiology, University of California, San Diego, CA, United States.
authors.forename: Shujuan
authors.initials: S
authors.lastname: Fan
authors.affiliation: Department of Radiology, University of California, San Diego, CA, United States.
authors.forename: Qun
authors.initials: Q
authors.lastname: He
authors.affiliation: Department of Radiology, University of California, San Diego, CA, United States.
authors.forename: Yajun
authors.initials: Y
authors.lastname: Ma
authors.affiliation: The Institute for Brain and Society, San Diego, CA, United States.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Annese
authors.affiliation: NeuroScience Associates, Inc., Knoxville, TN, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Switzer
authors.affiliation: Department of NeuroSciences, University of California, San Diego, United States.
authors.forename: Jody
authors.initials: J
authors.lastname: Corey-Bloom
authors.affiliation: Department of Radiology, University of California, San Diego, CA, United States.
authors.forename: Graeme M
authors.initials: GM
authors.lastname: Bydder
authors.affiliation: Department of Radiology, University of California, San Diego, CA, United States. Electronic address: jiangdu@ucsd.edu.
authors.forename: Jiang
authors.initials: J
authors.lastname: Du
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging*; D002102:Cadaver; D005240:Feasibility Studies; D005260:Female; D066128:Gray Matter / Q000000981:diagnostic imaging; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007501:Iron / Q000032:analysis*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000000981:diagnostic imaging*; D009186:Myelin Sheath / Q000473:pathology*; D019047:Phantoms, Imaging; D014867:Water; D066127:White Matter / Q000000981:diagnostic imaging
chemical_list: D014867:Water; D007501:Iron
keywords: Iron; Magnetic resonance imaging; Multiple sclerosis; Myelin; Ultrashort echo time