Which term describes the relative difference in signal strength between two adjacent tissue types in MRI?

• A. Signal-to-noise ratio
• B. Resolution
• C. Brightness
• D. Contrast

Answer: (D)

Contrast is about how different two neighboring tissues appear relative to one another on an MRI image. It describes the relative difference in signal intensity between those tissues, which comes from the tissue properties themselves (like T1, T2, and proton density) and from the imaging parameters used (the pulse sequence, repetition time, echo time) and whether a contrast agent is employed. This differential signal is what allows distinct borders to stand out and pathologies to be identified; greater contrast makes boundaries clearer and tissue types easier to tell apart.

While signal-to-noise ratio affects overall image clarity, it measures signal strength relative to background noise and doesn’t specify how two tissues differ from each other. Brightness refers to how bright a single region appears, not the relative difference between two tissues. Resolution is about the level of spatial detail and the ability to separate adjacent structures, rather than how their signals differ.