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In vivo quantification of the bound pool T1 in human white matter using the binary spin-bath model of progressive magnetization transfer saturation

Helms, Gunther LU orcid and Hagberg, Gisela E. (2009) In Physics in Medicine and Biology 54(23). p.529-540
Abstract
The relative size and relaxation of the invisible pool of bound spins (T1b) underlying magnetization transfer (MT) was quantified in eight subjects in vivo at 1.5 T from progressive saturation experiments using repetitive MT pulses. The evolution of the binary spin–bath was sampled by increasing the repetition period from 8 to 200 ms. Single-shot echo-planar images at TE=50ms were evaluated in the central white matter. Three models were fitted: the general solution, and with constraints of equal relaxation and T1b=1s for the invisible pool. The general solution of unconstrained T1b provided a significantly better fit, indicating fast-to-intermediate exchange. The bound pool fraction was 17±4%, the relaxation times T1f=1.6±0.2s for free... (More)
The relative size and relaxation of the invisible pool of bound spins (T1b) underlying magnetization transfer (MT) was quantified in eight subjects in vivo at 1.5 T from progressive saturation experiments using repetitive MT pulses. The evolution of the binary spin–bath was sampled by increasing the repetition period from 8 to 200 ms. Single-shot echo-planar images at TE=50ms were evaluated in the central white matter. Three models were fitted: the general solution, and with constraints of equal relaxation and T1b=1s for the invisible pool. The general solution of unconstrained T1b provided a significantly better fit, indicating fast-to-intermediate exchange. The bound pool fraction was 17±4%, the relaxation times T1f=1.6±0.2s for free water and T1b=171±22ms for the bound pool. The constrained models did not differ from each other, since here T1b was similar to the observed T1 of 1.1±0.1s. They underestimate the bound pool fraction and its relaxation. Thus, the standard assumption of continuous-wave MT models may underestimate the relaxation via the bound pool by more than a factor of five. (Less)
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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physics in Medicine and Biology
volume
54
issue
23
pages
529 - 540
publisher
IOP Publishing
external identifiers
  • scopus:70449715236
ISSN
1361-6560
DOI
10.1088/0031-9155/54/23/N01
language
English
LU publication?
yes
additional info
23
id
859ccde2-00a8-4021-a64c-d059925ab6b6 (old id 8773608)
date added to LUP
2016-04-01 12:14:01
date last changed
2022-03-28 22:07:47
@article{859ccde2-00a8-4021-a64c-d059925ab6b6,
  abstract     = {{The relative size and relaxation of the invisible pool of bound spins (T1b) underlying magnetization transfer (MT) was quantified in eight subjects in vivo at 1.5 T from progressive saturation experiments using repetitive MT pulses. The evolution of the binary spin–bath was sampled by increasing the repetition period from 8 to 200 ms. Single-shot echo-planar images at TE=50ms were evaluated in the central white matter. Three models were fitted: the general solution, and with constraints of equal relaxation and T1b=1s for the invisible pool. The general solution of unconstrained T1b provided a significantly better fit, indicating fast-to-intermediate exchange. The bound pool fraction was 17±4%, the relaxation times T1f=1.6±0.2s for free water and T1b=171±22ms for the bound pool. The constrained models did not differ from each other, since here T1b was similar to the observed T1 of 1.1±0.1s. They underestimate the bound pool fraction and its relaxation. Thus, the standard assumption of continuous-wave MT models may underestimate the relaxation via the bound pool by more than a factor of five.}},
  author       = {{Helms, Gunther and Hagberg, Gisela E.}},
  issn         = {{1361-6560}},
  language     = {{eng}},
  number       = {{23}},
  pages        = {{529--540}},
  publisher    = {{IOP Publishing}},
  series       = {{Physics in Medicine and Biology}},
  title        = {{In vivo quantification of the bound pool T1 in human white matter using the binary spin-bath model of progressive magnetization transfer saturation}},
  url          = {{http://dx.doi.org/10.1088/0031-9155/54/23/N01}},
  doi          = {{10.1088/0031-9155/54/23/N01}},
  volume       = {{54}},
  year         = {{2009}},
}