Accurate estimate of pancreatic T2* values: how to deal with fat infiltration.

PURPOSE: We examined different approaches aimed to deal with the signal fluctuation of pancreatic T2* values due to fat infiltration in order to obtain accurate estimates of iron overload.
METHODS: Pancreatic T2* values were assessed in 20 patients (13 females, 37.24 ± 9.12 years) enrolled in the Myocardial Iron Overload in Thalassemia network without and with the application of fat suppression-FS (T2*-NoFS and T2*-FS). T2* values were assessed in three different ways: (1) from the immediate fit (original T2*); (2) discarding the echoes until the achievement of a good visual concordance between the signal and the model (final_vis T2*); (3) eliminating the echoes until the achievement of a fitting error (known) <5% (final_thres T2*).
RESULTS: For the T2*-NoFS sequence the original T2* values were significantly higher than the final_vis T2* values (difference:4.8 ± 6.1 ms; P < 0.0001) and the final_thres T2* values (difference:4.3 ± 6.1 ms; P = 0.006). For the T2*-FS sequence the original T2* values were comparable to final_vis and final_thres T2* values. The original T2*-FS values were significantly different from the original T2*-NoFS values. The final_vis T2*-FS values were comparable to the final_vis T2*-NoFS values and the final_thresh T2*-FS values were comparable to the final_thresh T2*-NoFS values. For both T2*-FS and T2*-NoFS sequences, the final_thres T2* values were not significantly different from the final_vis T2* values and no bias was present.
CONCLUSIONS: In the clinical practice, an accurate pancreatic iron overload assessment should be done by applying FS and, when needed, by discarding the TEs until the fitting error goes below 5%.