A multiparametric alternative to short inversion‐time inversion recovery for imaging inflammation: T2water and fat fraction measurement using chemical shift–encoded turbo spin‐echo MRI

Abstract

PurposeShort‐inversion‐time inversion‐recovery MRI is used widely for imaging bone and soft‐tissue inflammation in rheumatic inflammatory diseases, but there is no widely available quantitative equivalent of this sequence. This limits our ability to objectively assess inflammation and distinguish it from other processes. To address this, we investigate the use of the widely available Dixon turbo spin echo (TSE Dixon) sequence as a practical approach to simultaneous water‐specific T2 (T2water) and fat fraction (FF) measurement.MethodsWe use a series of TSE Dixon acquisitions with varying effective TEs (TEeff) to quantify T2water and FF. The validity of this approach is assessed in a series of phantom and in vivo experiments, with reference values provided by Carr‐Purcell‐Meiboom‐Gill acquisitions, MRS, and phantoms. The effect of inflammation on parameter values is evaluated in patients with spondyloarthritis.ResultsThe T2water estimates obtained from TSE Dixon were accurate compared with the reference values from Carr‐Purcell‐Meiboom‐Gill and spectroscopy in both fat‐free environments and in the presence of fat. FF measurements with T2water correction from TSE Dixon were accurate from 0% to 60% FF and were not confounded by T2water variations. In vivo imaging produced good quality images that were artifact free, produced plausible T2 values, separating and quantifying the effect of inflammation on T2water and FF.ConclusionThe T2water and FF measurements based on TSE Dixon with effective TE increments are accurate over a range of T2 and FF values and could provide a widely available quantitative alternative to the short‐inversion‐time inversion‐recovery sequence for imaging inflamed tissue.