In angiography, if the true lumen of the left ICA measures 9 mm and the residual lumen is 3 mm, what is the diameter reduction?

To determine the diameter reduction in the left internal carotid artery (ICA), the measurements of the true lumen and the residual lumen must be utilized. The true lumen measures 9 mm, while the residual lumen, which is the remaining part of the artery that is still open, measures 3 mm.

The diameter reduction is calculated using the formula:

[ \text{Diameter Reduction} = \frac{\text{True Lumen Diameter} - \text{Residual Lumen Diameter}}{\text{True Lumen Diameter}} \times 100% ]

Substituting the given values into this formula:

1. True Lumen Diameter = 9 mm
2. Residual Lumen Diameter = 3 mm

Calculating the diameter reduction:

[ \text{Diameter Reduction} = \frac{9 mm - 3 mm}{9 mm} \times 100% ] [ = \frac{6 mm}{9 mm} \times 100% ] [ = \frac{2}{3} \times 100% ] [ \approx 66.67% ]

This value rounds to approximately 67%. Therefore, the diameter reduction of the left ICA is correctly identified as 67