Abstract:
:The signal decay with increasing b-factor at fixed echo time from brain tissue in vivo has been measured using a line scan Stejskal-Tanner spin echo diffusion approach in eight healthy adult volunteers. The use of a 175 ms echo time and maximum gradient strengths of 10 mT/m allowed 64 b-factors to be sampled, ranging from 5 to 6000 s/ mm2, a maximum some three times larger than that typically used for diffusion imaging. The signal decay with b-factor over this extended range showed a decidedly non-exponential behavior well-suited to biexponential modeling. Statistical analyses of the fitted biexponential parameters from over 125 brain voxels (15 x 15 x 1 mm3 volume) per volunteer yielded a mean volume fraction of 0.74 which decayed with a typical apparent diffusion coefficient around 1.4 microm2/ms. The remaining fraction had an apparent diffusion coefficient of approximately 0.25 microm2/ms. Simple models which might explain the non-exponential behavior, such as intra- and extracellular water compartmentation with slow exchange, appear inadequate for a complete description. For typical diffusion imaging with b-factors below 2000 s/mm2, the standard model of monoexponential signal decay with b-factor, apparent diffusion coefficient values around 0.7 microm2/ms, and a sensitivity to diffusion gradient direction may appear appropriate. Over a more extended but readily accessible b-factor range, however, the complexity of brain signal decay with b-factor increases, offering a greater parametrization of the water diffusion process for tissue characterization.
journal_name
NMR Biomedjournal_title
NMR in biomedicineauthors
Mulkern RV,Gudbjartsson H,Westin CF,Zengingonul HP,Gartner W,Guttmann CR,Robertson RL,Kyriakos W,Schwartz R,Holtzman D,Jolesz FA,Maier SEdoi
10.1002/(sici)1099-1492(199902)12:1<51::aid-nbm546subject
Has Abstractpub_date
1999-02-01 00:00:00pages
51-62issue
1eissn
0952-3480issn
1099-1492pii
10.1002/(SICI)1099-1492(199902)12:1<51::AID-NBM546journal_volume
12pub_type
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