Comparison of MOLLI and ShMOLLI at 1.5 and 3 Tesla for detection of early cardiac iron deposition in patients with transfusional siderosis

Patients receiving chronic transfusion develop iron overload in the liver, endocrine glands, and heart. Cardiac T2* has become the standard of care for detecting preclinical cardiac iron deposition and has been validated against tissue iron levels. Recent work suggests that T1 mapping can also be used to detect myocardial iron and may be more sensitive to early cardiac iron deposition. However, myocardial T1 measurements have not been as well standardized across pulse sequences, vendors, and field strengths. We compared two modified Look-Locker sequences (MOLLI and ShMOLLI) at 1.5 and 3 Tesla in patients with transfusional siderosis.

17 patients were scanned using a 16-element torso coil in a Philips Achieva 3T scanner; 9 of these were also scanned at 1.5T. MOLLI (3-3-5 sampling) and ShMOLLI (7 inversion times) images were collected from a single mid-papillary slice in a single breath-hold, with inversion times between 161 and 3900 ms. Epicardial and endocardial boundaries were traced on individual images and segmented according to the AHA 17-segment model. Median T1_MOLLI and T1_ShMOLLI were compared using Bland-Altman analysis.

T2* is gold standard for stratifying cardiac risk in iron overloaded subjects. T1 mapping could complement T2* assessment since it may have better sensitivity and specificity for detecting early cardiac iron deposition, whereas cardiac T2* assessments are more vulnerable to motion and susceptibility artifacts. T1 is also sensitive to fibrosis, and changes with contrast administration could be used to quantify extracellular volume. Unfortunately, there are many T1 mapping techniques (eg. MOLLI, ShMOLLI, SASHA) and they differ in their absolute quantification. In our implementation, ShMOLLI systematically underestimates MOLLI T1 estimates.