Magnetic Resonance Imaging (MRI) Practice Test

Which of the following creates a brighter signal in diffusion MRI?

1. High cellularity

2. Low water mobility

3. High fat content

4. High signal-to-noise ratio

The correct answer is: Low water mobility

In diffusion MRI, a brighter signal is associated with low water mobility because it indicates that water molecules are restricted in their movement. This restriction often occurs in tissues with high cellularity, such as tumors or areas of inflammation, where the increased number of cells leads to less space for water molecules to move freely. As a result, the diffusion of water is hindered, creating a stronger signal on diffusion-weighted images. Low water mobility reflects a situation where the diffusion of water is impeded, leading to a greater accumulation of the diffusion-weighted signal. This allows radiologists to distinguish between different tissue types and conditions based on their cellular characteristics as seen in the MRI results. Thus, low water mobility provides critical information about the underlying tissue microenvironment, contributing to the brightness of the signal detected in diffusion MRI.