Figure 3. Graph shows the relationship between baseline and follow-up values of Doppler US-based intracoronary blood flow (CBF) and electron-beam CT-based perfusion (F) at rest and after adenosine. There is a good correlation between intracoronary blood flow and perfusion over the entire range of flow values. Variation of measurements around the regression line is primarily attributable to nonsimultaneous data acquisition (ie, temporal heterogeneity of myocardial perfusion) and to tomographic sampling of a myocardial subsection within the perfusion territory with electron-beam CT versus upstream assessment of blood flow through the entire perfusion bed with Doppler US (ie, spatial heterogeneity of myocardial perfusion).