Comparison of BOLD, diffusion-weighted fMRI and ADC-fMRI for stimulation of the primary visual system with a block paradigm.
The blood oxygen level-dependent (BOLD) effect is extensively used for functional MRI (fMRI) but presents some limitations. Diffusion-weighted fMRI (DfMRI) has been proposed as a method more tightly linked to neuronal activity. This work proposes a protocol of DfMRI acquired for several b-values and diffusion directions that is compared to gradient-echo BOLD (GE-BOLD) and to repeated spin-echo BOLD (SE-BOLD, acquisitions performed with b=0s/mm2), which was also used to ensure the reproducibility of the response. A block stimulation paradigm of the primary visual system (V1) was performed in 12 healthy subjects with checkerboard alternations (2Hz frequency). DfMRI was performed at 3T with 5 b-values (b=1500, 1000, 500, 250, 0s/mm2) with TR/TE=1004/93ms, Δ/δ=45.4ms/30ms, and 6 spatial directions for diffusion measures. GE-BOLD was performed with a similar block stimulation design timing. Apparent Diffusion Coefficient (ADC)-fMRI was computed with all b-values used. An identical Z-score level was used for all fMRI modalities for the comparison of volumes of activation. ADC-fMRI and SE-BOLD fMRI activation locations were compared in a voxel-based analysis to a cytoarchitectural probability map of V1. SE-BOLD activation volumes represented only 55% of the GE-BOLD activation volumes (P<0.0001). DfMRI activation volumes averaged for all b-values acquired represented only 12% of GE-BOLD (P<0.0001) and only 22% of SE-BOLD activation volumes (P<0.005). Compared to SE-BOLD-fMRI, ADC-fMRI activations showed fewer pixels outside of V1 and a higher average probability of belonging to V1. DfMRI and ADC-fMRI acquisition at 3T could be easily post-processed with common neuro-imaging software. DfMRI and ADC-fMRI activation volumes were significantly smaller than those obtained with SE-BOLD. ADC-fMRI activations were more precisely localized in V1 than those of SE-BOLD-fMRI. This validated the increased capability of ADC-fMRI compared to BOLD to enhance the precision of localizing an fMRI activation in the cyto-architectural zone V1, thereby justifying the use of ADC-fMRI for neuro-scientific studies.
Imagerie cérébrale et handicaps neurologiques, INSERM Université de Toulouse (UMR 825), F-31059 Toulouse, France; Aquitaine Institute for Cognitive and Integrative Neuroscience (INCIA), CNRS Université Bordeaux 2 (UMR 5287), F-33400 Talence, France; ARCANI, 27, rue fonfrède (N° SIRET: 803 234 715 00016), F-33800 Bordeaux, France. Electronic address: rnd.nicolas@gmail.com.
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Nicolas
Imagerie cérébrale et handicaps neurologiques, INSERM Université de Toulouse (UMR 825), F-31059 Toulouse, France.
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Gros-Dagnac
Imagerie cérébrale et handicaps neurologiques, INSERM Université de Toulouse (UMR 825), F-31059 Toulouse, France.
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Aubry
Imagerie cérébrale et handicaps neurologiques, INSERM Université de Toulouse (UMR 825), F-31059 Toulouse, France.
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Celsis
D000465:Algorithms; D001931:Brain Mapping / Q000379:methods*; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D012984:Software
D010100:Oxygen
ADC; BOLD; Block stimulation paradigm; Cytoarchitectonic; Cytoarchitecture; Diffusion-weighted functional MRI; Grey matter; IVIM; Primary visual system V1