Definitions of outcome, response and effect in imaging research to avoid confusion.

The % change of normalized percent atheroma volume (PAV) is shown in the upper left panel and of total atheroma volume (TAV) in the upper right panel. The comparison is between segments with endothelial dysfunction and those with normal endothelial function. Representative examples of intravascular ultrasound (IVUS) findings are shown in the lower panel. Segments with endothelial dysfunction showed greater progression in PAV (*p < 0.05) and TAV (p 1⁄4 0.065) than segments with normal endothelial function from the same subject. IVUS demonstrates the progression of disease-only segments with endothelial dysfunction (lumen traced in green, external elastic membrane in yellow). Letters to the Editor J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . 7 , N O . 1 , 2 0 1 4