Figure 15. Results from a Monte Carlo modelling experiment to assess the accuracy of pharmacokinetic models in estimating K^trans. Graphs on the left show data with a very high signal-to-noise ratio (SNR) central graphs show data using a lower SNR and data on the right shows the results where the SNR is low. The upper series of graphs show the accuracy and standard deviations associated with fitting synthetic data using the standard Tofts and Kermode model. It can be seen that at low SNR this technique becomes highly inaccurate and imprecise. The middle row shows the effect of using the first pass pharmacokinetic model described by Li et al [43]. This model systematically underestimates high values of k_fp but shows good reproducibility even at relatively low SNRs. The lower series of graphs shows a more complex model which combines the two analysis techniques [43]. This hybrid method shows good accuracy and precision across a wide range of SNR values.