Accuracy and homogeneity of dictionary-based T2-mapping dedicated to single slice and multi-slice multi-echo...

Multi-echo turbo spin-echo (ME-TSE) sequences enable rapid T2 mapping but are prone to errors from stimulated echoes and slice cross-talk in multi-slice imaging. Moreover, the impact of different effective echo time (TEeff) selections on T2 measurement accuracy in ME-TSE remains unstudied. Therefore, the purpose of this study was to develop and validate a dictionary-based T2 mapping method for rapid multi-slice ME-TSE that accounts for slice cross-talk and to determine how TEeff selection influences mapping accuracy. Experiments were conducted in five calibrated agarose phantoms and two healthy volunteers at 3 T using an ME-TSE sequence. Nine TEeff combinations were evaluated, and experimental echo modulation curves were fitted to single-slice and multi-slice dictionaries generated via Bloch simulations involving slice interaction. Results showed that TEeff combination affected accuracy (mean relative error range: -1.97% to -6.96%) and homogeneity (SD range: 2.84-17.25 ms). Multi-slice dictionary fitting reduced inter-slice CV from 4.77% to 1.1% (phantoms) and from 1.95% to 1.04% (volunteer 1) and 1.76% to 1.11% (volunteer 2). Relative errors improved in phantoms from -19.22/-1.35% to -8.41/1.29% using multi-slice dictionaries. In conclusion, multi-slice dictionary-based fitting effectively mitigates slice cross-talk, improving T2 accuracy and inter-slice homogeneity in fast ME-TSE acquisitions. TEeff selection impacts precision, with well-separated echoes yielding superior results.