Increasing crystal thickness for higher-energy gamma rays has what effect on spatial resolution?

Increasing crystal thickness for higher-energy gamma rays has what effect on spatial resolution?

• A. Increases stopping power and increases resolution
• B. Increases stopping power and decreases resolution
• C. Decreases stopping power and decreases resolution
• D. Decreases stopping power and increases resolution

Answer: (B)

The key idea is the trade-off between detection efficiency and depth-based uncertainty. Higher-energy gamma rays are harder to stop, so making the crystal thicker increases the chance that a gamma will interact (greater stopping power and better detection efficiency). But as the crystal gets thicker, the exact depth at which the interaction occurs becomes more uncertain, which introduces parallax and degrades the ability to pinpoint where the event happened—reducing spatial resolution. So increasing thickness for higher-energy gammas improves stopping power but lowers spatial resolution.

The key idea is the trade-off between detection efficiency and depth-based uncertainty. Higher-energy gamma rays are harder to stop, so making the crystal thicker increases the chance that a gamma will interact (greater stopping power and better detection efficiency). But as the crystal gets thicker, the exact depth at which the interaction occurs becomes more uncertain, which introduces parallax and degrades the ability to pinpoint where the event happened—reducing spatial resolution. So increasing thickness for higher-energy gammas improves stopping power but lowers spatial resolution.