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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 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
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
id
859ccde2-00a8-4021-a64c-d059925ab6b6 (old id 8773608)
date added to LUP
2016-02-27 00:56:13
date last changed
2017-09-10 03:44:10
@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},
  volume       = {54},
  year         = {2009},
}