The GATE Grind

GATE 2021 BM – Question 28

Medical Imaging Systems · X-Ray and Computed Tomography · 1 mark · Multiple select

Which statements about planar X-ray imaging are correct?

  1. A fast X-ray screen improves spatial resolution
  2. A fast X-ray screen worsens spatial resolution
  3. Reducing tube current decreases signal-to-noise ratio
  4. Reducing tube current increases signal-to-noise ratio

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Show answer and explanation

Correct answer: (B) A fast X-ray screen worsens spatial resolution; (C) Reducing tube current decreases signal-to-noise ratio

Explanation

A fast intensifying screen gives more light output but generally greater light spreading, trading spatial resolution for sensitivity, B. At unchanged exposure time, reducing tube current reduces detected photon count; quantum-limited SNR scales with the square root of that count, so it decreases, C. Thus B,C.

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