期刊
PHYSICS IN MEDICINE AND BIOLOGY
卷 61, 期 24, 页码 N667-N680出版社
IOP PUBLISHING LTD
DOI: 10.1088/1361-6560/61/24/N667
关键词
diffusion-weighted magnetic resonance imaging; functional magnetic resonance imaging; intravoxel incoherent motion; reproducibility of results; IVIM; T2IVIM; perfusion magnetic resonance imaging
资金
- CR-UK [C7273]
- CRUK
- EPSRC Cancer Imaging Centre in association
- MRC
- Department of Health (England) [C1060/A16464, C1060/A10334, C16412/A6269]
- NHS
- Imagine for Margo
- Cancer Research UK [16464] Funding Source: researchfish
- National Institute for Health Research [NF-SI-0512-10162] Funding Source: researchfish
The bi-exponential intravoxel-incoherent-motion (IVIM) model for diffusion-weighted MRI (DWI) fails to account for differential T(2)s in the model compartments, resulting in overestimation of pseudodiffusion fraction f . An extended model, T2-IVIM, allows removal of the confounding echo-time (TE) dependence of f, and provides direct compartment T-2 estimates. Two consented healthy volunteer cohorts (n = 5, 6) underwent DWI comprising multiple TE/b-value combinations (Protocol 1: TE = 62-102 ms, b = 0-250 mm(-2)s, 30 combinations. Protocol 2: 8 b-values 0-800 mm(-2)s at TE = 62 ms, with 3 additional b-values 0-50 mm(-2)s at TE = 80, 100 ms; scanned twice). Data from liver ROIs were fitted with IVIM at individual TEs, and with the T2-IVIM model using all data. Repeat-measures coefficients of variation were assessed for Protocol 2. Conventional IVIM modelling at individual TEs (Protocol 1) demonstrated apparent f increasing with longer TE: 22.4 +/- 7% (TE = 62 ms) to 30.7 +/- 11% (TE = 102 ms); T2-IVIM model fitting accounted for all data variation. Fitting of Protocol 2 data using T2-IVIM yielded reduced f estimates (IVIM: 27.9 +/- 6%, T2-IVIM: 18.3 +/- 7%), as well as T2 = 42.1 +/- 7 ms, 77.6 +/- 30 ms for true and pseudodiffusion compartments, respectively. A reduced Protocol 2 dataset yielded comparable results in a clinical time frame (11 min). The confounding dependence of IVIM f on TE can be accounted for using additional b/TE images and the extended T2-IVIM model.
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