Plasma time-activity curve of [11
C]befloxatone concentrations in arterial and venous blood for a representative subject. The main frame shows the first 10 min; the inset magnifies the remaining part of the input function. Red curve, arterial blood; blue curve, venous blood. The venous peak was predictably much lower than the arterial one, but [11C]befloxatone concentrations were remarkably similar immediately after the peak until the end of the scan. Although compartmental modeling cannot be used with a venous input due to the different shapes of the early part of the curves, the Logan graphical analysis only depends on the total area under the curve. For this subject, the V
T error using only the venous input was 7.2% compared to the reference V
T values obtained with the arterial input.