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Perfusion quantification in the lung
On gamma variate fitting for perfusion quantification in the lung.
Marta Tibiletti, Jo Naish, Matthew J. Heaton, Paul Hughes, Jim Wild, Geoff JM Parker
ISMRM Conference 2020
Imaging of the first pass of a contrast agent bolus through a tissue allows the measurement of blood flow (BF), blood volume (BV) and mean transit time (MTT). Application of first pass imaging to the lung with MRI has significant advantages over perfusion quantification with SPECT or CT. The majority of works on this topic apply a Singular Value Decomposition (SVD4) with or without a prior fit to a gamma variate (GV) function to the concentration-time curve. In this study we compare lung perfusion quantification with and without GV fitting in a population of patients with interstitial lung disease (ILD). We also compare results from two GV formulations, as described by Madsen and by Li.
The presence and choice of gamma variate fitting has an influence on perfusion parameters, but this is generally very small, except for mean transit time. GV1 is to be preferred to GV2 given the the lower dispersal of results and only minimally higher fitting residuals. Also, the observed correlations between perfusion MR parameters and lung function tests are similar between fitting with GV1 and no fit, suggesting that these approaches are broadly equivalent in practice.