Quantitative Magnetization Transfer Imaging For Non-Contrast Enhanced Detection Of Myocardial Fibrosis

Purpose: To develop a novel gadolinium-free model-based quantitative magnetization transfer (qMT) technique to assess macromolecular changes associated with myocardial fibrosis.Methods: The proposed sequence consists of a two-dimensional breath-held dual shot interleaved acquisition of five MT-weighted (MTw) spoiled gradient echo images, with variable MT flip angles (FAs) and off-resonance frequencies. A two-pool exchange model and dictionary matching were used to quantify the pool size ratio (PSR) and bound pool T2 relaxation (T2B). The signal model was developed and validated using 25 MTw images on a bovine serum albumin (BSA) phantom and in vivo human thigh muscle. A protocol with five MTw images was optimized for single breath-hold cardiac qMT imaging. The proposed sequence was tested in 10 healthy subjects and 5 patients with myocardial fibrosis and compared to late gadolinium enhancement (LGE).Results: PSR values in the BSA phantom were within the confidence interval of previously reported values (concentration 10% BSA = 5.9 +/- 0.1%, 15% BSA = 9.4 +/- 0.2%). PSR and T2B in thigh muscle were also in agreement with literature (PSR = 10.9 +/- 0.3%, T2B = 6.4 +/- 0.4 us). In 10 healthy subjects, global left ventricular PSR was 4.30 +/- 0.65%. In patients, PSR was reduced in areas associated with LGE (remote: 4.68 +/- 0.70% vs. fibrotic: 3.12 +/- 0.78 %, n = 5, P < .002).Conclusion: In vivo model-based qMT mapping of the heart was performed for the first time, with promising results for non-contrast enhanced assessment of myocardial fibrosis.