Fig. 4

Time-activity curves for the urinary bladder illustrating the activity underestimation of the threshold VOI. Mean time-activity curves for the urinary bladder plus the measured voided activity determined from the 42% threshold VOI and the whole slice method. Error bars indicate the range of the data, and data has been offset slightly on the x-axis for clarity. The broken lines show the results of fitting the function A(t) = C + α e ^− λt (see Eq. 1). In the case of the whole slice region (C = 88, α = −88 and λ = 0.3131), the percentage of activity excreted through the renal pathway is 88%, and for the threshold VOI (C = 266, α = −266 and λ = 0.0598), the fitted parameters are not physiologically meaningful (i.e. renal excretion of 266%)