In CT, increasing the tube current (mAs) while keeping kVp constant will primarily:

• A Increase the mean energy of the X-ray beam
• B Increase image noise without changing patient dose
• C Increase spatial resolution by reducing focal spot size
• D Reduce image noise and increase patient dose proportionally ✓

Explanation

In CT, mAs (milliampere-seconds) determines the number of X-ray photons produced. Increasing mAs increases photon flux, reducing quantum noise (image noise ∝ 1/√mAs), and proportionally increases patient radiation dose. kVp determines photon energy spectrum (mean energy and penetration). Increasing kVp increases photon energy. Spatial resolution is determined by detector size and reconstruction kernel, not mAs. Focal spot size affects spatial resolution but is not altered by mAs changes in modern scanners.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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