The position dependence of the apparent diffusion coefficient; signal-to-noise ratio vs B1 map

The position dependence of the ADC in magnetic resonance imaging (MRI) by EPI- and TSE-DWI was assessed using phantoms based on the relationship between SNR and B1 maps. ADC decreased with distance from the center of the magnetic field for both EPI-DWI and TSE-DWI. The Pearson correlation coefficient between ADC and FA was strong and more significant than between ADC and SNR. ADC depends on the slice position and decreases with an increase in distance from the magnetic field center. Caution should be taken when comparing and quantitatively evaluating the ADC at sites shifted in the long-axis direction.