{'fraction_non_alphanumeric': 0.025664527956003668, 'fraction_numerical': 0.016498625114573784, 'mean_word_length': 5.618181818181818, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Uncertainty in the analysis of tracer kinetics using dynamic contrast‐enhanced T1‐weighted MRI

In recent years a number of physiological models have gained prominence in the analysis of dynamic contrast‐enhanced T1‐weighted MRI data. However, there remains little evidence to support their use in estimating the absolute values of tissue physiological parameters such as perfusion, capillary permeability, and blood volume. In an attempt to address this issue, data were simulated using a distributed pathway model of tracer kinetics, and three published models were fitted to the resultant concentration‐time curves. Parameter estimates obtained from these fits were compared with the parameters used for the simulations. The results indicate that the use of commonly accepted models leads to systematic overestimation of the transfer constant, Ktrans, and potentially large underestimates of the blood plasma volume fraction, Vp. In summary, proposals for a practical approach to physiological modeling using MRI data are outlined. Magn Reson Med 47:601–606, 2002. © 2002 Wiley‐Liss, Inc.