T2* values were computed using Thalassemia tools (a plugin of CMRtools, Cardiovascular Imaging Solutions, 2012 version, London, UK). The value of T2* relaxation time was derived with an equation of y=Ke−TE/T2*, where K represents a constant, TE represents echo times, and y represents the image signal intensity (15). A truncation model was used to correct the bias caused by background noise at long TEs and improve the curve fit (22). The fitting quality of T2* measurements obtained by CMRtools was recorded. FF maps were calculated using the iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) algorithm (23). Region of interests (ROI) were drawn on the FF maps using image J software (NIH, Bethesda, MD) to measure the FF values. For both T2* and FF measurements, an ROI of 1–2 cm2 was manually placed on the pancreas head, body, and tail, respectively (Figure 1), as previously described (16). Only clearly identified and demarcated pancreatic tissue was considered for analysis. ROIs were drawn by 2 radiologists independently (with 5 years and 3 years of experience with abdominal MRI). The global R2* and global FF values were obtained by averaging the respective values from the pancreatic head, body, and tail. The T2* relaxation time was transformed into reciprocal R2* according to the following formula: R2* (s−1) = 1,000/T2* (ms). A global pancreatic R2* value <30 s−1 was considered normal, 30 s−1 <R2*<100 s−1 was considered mild IO, 100 s−1 <R2*<400 s−1 was considered moderate IO, and R2*>400 s−1 was considered severe IO (24). FF>0.065 was considered abnormal (25).

Axial pseudo-colorized images derived from T2* relaxometry scans in a 13-year-old female patient with thalassemia major. Three different free-hand ROIs of 1–2 cm2 were manually placed in the pancreas head (A), body (B), and tail (C), with a sufficient distance maintained from gland boundaries and vascular structures. ROI, region of interest.

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