FIGURE 1.

Left panel: example of TAC generated from CT images during passage of a bolus of non-ionic contrast agent injected into a cubital vein (0.25 mL kg⁻¹ of a 350 mg Iodine mL⁻¹ solution). A series of CT images (each reconstructed from scan data collected for 75 ms), of the same transaxial slices, are recorded for every cardiac cycle during a breath-hold period of 30 s. The TAC curves are generated from a region-of-interest (ROI) within this series of images, and computing the average gray scale within the ROI at each time point. Right panel shows the same TAC data plus the least squares fit of gamma variant curves, a single curve for the LV and the intravascular and extravascular curves for the myocardium as computed using Eqs. (1) and (2) respectively. The discordence between the gamma variate curves at the tail of the curves is largely due to recirculation of the contrast agent. The gamma variate curves serve, in part, to eliminate the influence of recirculation.³⁴