Prog Med Phys.  2019 Mar;30(1):22-31. 10.14316/pmp.2019.30.1.22.

b0 Dependent Neuronal Activation in the Diffusion-Based Functional MRI

Affiliations
  • 1Department of Biomedical Engineering, Graduate School, Kyung Hee University, Yongin, Korea.
  • 2Department of Radiology, Kyung Hee University Hospital at Gangdong, College of Medicine, Kyung Hee University, Seoul, Korea. ghjahng@gmail.com

Abstract

PURPOSE
To develop a new diffusion-based functional MRI (fMRI) sequence to generate apparent diffusion coefficient (ADC) maps in single excitation and evaluate the contribution of b0 signal on neuronal changes.
MATERIALS AND METHODS
A diffusion-based fMRI sequence was d esigned with single measurement that can acquire images of three directions at a time, obtaining b = 0 s/mm2 during the first baseline condition (b0_b), followed by 107 diffusion-weighted imaging (DWI) with b = 600 s/mm2 during the b aseline and visual stimulation conditions, and another b = 0 s/mm2 during the last activation condition (b0_a). ADC was mapped in three different ways: 1) using b0_b (ADC_b) for all time points, 2) using b0_a (ADC_a) for all time points, and 3) using b0_b and b0_a (ADC_ba) for baseline and stimulation scans, respectively. The fMRI studies were conducted on the brains of 16 young healthy volunteers using visual stimulations in a 3T MRI system. In addition, the blood oxygen level dependent (BOLD) fMRI was also acquired to compare it with diffusion-based fMRI. A sample t-test was used to investigate the voxel-wise average between the subjects.
RESULTS
The BOLD data consisted of only activated voxels. However, ADC_ba data was observed in both deactivated and activated voxels. There were no statistically significant activated or deactivated voxels for DWI, ADC_b, and ADC_a.
CONCLUSIONS
With the new sequence, neuronal activations can be mapped with visual stimulation as compared to the baseline condition in several areas in the brain. We showed that ADC should be mapped using both DWI and b0 images acquired with the same conditions.

Keyword

Brain function; Functional MRI; Diffusion; ADC; BOLD
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