As slice thickness increases, which phenomenon occurs in MRI?

• A. Partial volume effect increases
• B. Greater coherence of signals
• C. Loss of contrast resolution
• D. Improved detail visibility

Answer: (A)

As slice thickness increases in MRI imaging, the partial volume effect becomes more pronounced. This phenomenon occurs because a thicker slice encompasses a larger volume of tissue, which can include different types of tissues or structures. When different tissues with varying magnetic properties are included within a single voxel (the smallest distinguishable box-shaped part of a three-dimensional image), the resulting signal averaged within that voxel can dilute or blur the distinct characteristics of each individual tissue. As a result, fine details may be lost, making it more challenging to identify and differentiate subtle differences in tissue types or pathology.

While greater slice thickness may enhance some aspects of signal strength and improve overall signal-to-noise ratio, the trade-off includes a decrease in spatial resolution and clarity, making the partial volume effect a crucial consideration in MRI technique selection.