Comparison of T1-weighted turbo spin echo and out-of-phase T1-weighted gradient echo Dixon MRI for the assessment of intra-medullary length of appendicular bone tumours

Intra-medullary tumour length is accurately assessed on T1-weighted turbo spin echo (T1W TSE) MRI which can be relatively time consuming, whilst the gradient echo Dixon (T1W GrE Dixon) technique is a rapid sequence (imaging time ~ 30 s). The aim of this study was to determine if the out-of-phase Dixon (OP T1W GrE Dixon) sequence can produce equivalent measurements of intra-medullary tumour length compared to the T1W TSE sequence. Tumour length was assessed in 90 patients undergoing MRI for staging of primary bone tumours with both T1W TSE and OP T1W GrE Dixon MRI sequences at 3 T (n = 42) and 1.5 T (n = 48). Tumour length was measured independently by different observers allowing assessment of inter-observer correlation, and the correlation between measurements on T1W TSE and OP T1W GrE Dixon sequences was also determined. There were 53 males and 37 females (mean age 36.4 years; range 2–77 years). Inter-observer correlation for tumour length on both the T1W TSE and T1W OP GrE Dixon sequences was very good (ICC = 0.94–0.98), and measurement of tumour length comparing T1W TSE and T1W GrE Dixon was also very good (ICC = 0.91–0.99). In 4 cases, tumour length was significantly overestimated on T1W TSE images due to extensive reactive marrow oedema, but more accurately determined on the OP sequence when compared to resection specimens. The OP T1W GrE Dixon sequence is comparable to T1W TSE for assessment of the intra-medullary length of appendicular bone tumours, and more accurate in the presence of extensive reactive marrow oedema.