1356599 - Free-breathing mSASHA extracellular volume in patients is significantly lower than MOLLI in accordance with previous experimental data

Myocardial extracellular volume fraction (ECV) can be assessed non-invasively by CMR using T1 mapping pre and post contrast agent administration. However, different T1 mapping sequences can yield different ECV values that do not necessarily reflect the true ECV. A previous experimental study showed that T1 mapping using Modified Look-Locker Inversion recovery (MOLLI) overestimates ECV compared to SAturation-recovery single-SHot Acquisition (SASHA) as validated by ex vivo reference values (1). Recently, a multi-parametric SASHA (mSASHA) was introduced that enables simultaneous acquisition of T1 and T2 maps (2), which also can be acquired during free breathing (3). This enables T1 mapping and calculation of ECV also in patients unable to hold their breath, such as heart failure patients. How ECV assessed using MOLLI compared to mSASHA in a clinical context is not known. Therefore, the aim of this study was to assess to what extent ECV derived from MOLLI and mSASHA differs, and whether mSASHA acquired during free breathing differs from acquisition during breath-hold in consecutive clinical patients.

Methods:

Sixty-three consecutive patients referred for clinical CMR were included (63 [range 13-88] years old, 26 females) and all subjects were imaged at 1.5T (MAGNETOM Aera, Siemens Healthcare, Erlangen, Germany). All patients had history of suspected cardiac disease requiring an imaging protocol including contrast agent administration. A midventricular T1 map was acquired both with MOLLI and prototype mSASHA before and approximately 20 minutes after Gd-based contrast agent administration (0.15 mmol/kg; Gadoteric acid, Clariscan, GE Healthcare, Stockholm, Sweden). The MOLLI acquisition scheme was 5(3s)3 before and 4(1s)3(1s)2 after contrast agent administration, both acquired during breath-hold. The mSASHA acquisition was performed during free breathing in all patients. Further, in a subset of 16 patients, mSASHA was also acquired during breath-hold. ECV was calculated as previously described (4) where Hct is hematocrit (equation 1). 

Results:

Extracellular volume derived from mSASHA acquired in free breathing was significantly lower compared to ECV derived from MOLLI acquired during breath-hold (25±4% vs 28±4%, P< 0.001; Figure 1A, n=63). This difference is similar to previous experimental data by Nordlund et al (1) where SASHA showed less bias compared to ex vivo ECV reference. There was no difference in ECV derived from mSASHA in free breathing and during breath-hold (25±4% vs 24±4%, P=0.46; Figure 1B, n=16).

Conclusion:

Extracellular volume derived from mSASHA is significantly lower than MOLLI in consecutive clinical patients undergoing CMR, in accordance with previous experimental data. Furthermore, mSASHA can be performed during free breathing without interfering with ECV accuracy. Thus, mSASHA can be recommended for clinical implementation for assessment of ECV.