Using the relation that volumetric blood flow in a straight vessel is proportional to the radius to the fourth power (Q ∝ r^4), calculate the percentage of original flow remaining if atherosclerotic plaque reduces arterial radius by 50%. Show your steps and final answer.

• A. Flow would be unchanged because compensatory vasodilation elsewhere preserves perfusion.
• B. Approximately 25% of the original flow remains since flow decreases proportional to the square of the radius.
• C. Approximately 6.25% of the original flow remains.
• D. Approximately 50% of the original flow remains because the radius decreased by half and flow scales linearly with radius.

Answer: (C)