{'fraction_non_alphanumeric': 0.02692595362752431, 'fraction_numerical': 0.011967090501121914, 'mean_word_length': 6.51685393258427, '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}}
Advantages of frequency‐domain modeling in dynamic‐susceptibility contrast magnetic resonance cerebral blood flow quantification

In dynamic‐susceptibility contrast magnetic resonance perfusion imaging, the cerebral blood flow (CBF) is estimated from the tissue residue function obtained through deconvolution of the contrast concentration functions. However, the reliability of CBF estimates obtained by deconvolution is sensitive to various distortions including high‐frequency noise amplification. The frequency‐domain Fourier transform‐based and the time‐domain singular‐value decomposition‐based (SVD) algorithms both have biases introduced into their CBF estimates when noise stability criteria are applied or when contrast recirculation is present. The recovery of the desired signal components from amid these distortions by modeling the residue function in the frequency domain is demonstrated. The basic advantages and applicability of the frequency‐domain modeling concept are explored through a simple frequency‐domain Lorentzian model (FDLM); with results compared to standard SVD‐based approaches. The performance of the FDLM method is model dependent, well representing residue functions in the exponential family while less accurately representing other functions. Magn Reson Med 53:700–707, 2005. © 2005 Wiley‐Liss, Inc.