Quantitative R 2 MRI of the liver with rician noise models for evaluation of hepatic iron overload: Simulation, phantom, and early clinical experience

• Published in: Journal of magnetic resonance imaging Vol. 42; no. 6; pp. 1544 - 1559
• Main Authors: Yokoo, Takeshi, Yuan, Qing, Sénégas, Julien, Wiethoff, Andrea J., Pedrosa, Ivan
• Format: Journal Article
• Language: English
• Published: 01.12.2015
• ISSN: 1053-1807; 1522-2586
• DOI: 10.1002/jmri.24948

Purpose To compare Rician and non‐Rician noise models for quantitative R 2 * magnetic resonance imaging (MRI), in a simulation, phantom, and human study. Materials and Methods Synthetic 12‐echo spoiled GRE (SGRE) datasets were generated with various R 2 * rates (0–2000 sec ‐1 ) at a signal‐to‐noise ratio (SNR) of 50, 20, 10, and 5. Phantoms of different MnCl 2 concentrations (0–25 mM) were constructed and imaged using a 12‐echo 3D SGRE sequence at 1.5T. Increasing levels of synthetic noise was added to the original data to simulate sequentially lower SNR conditions. Sixteen patients with suspected or known iron overload were imaged using 12‐echo 3D SGRE at 1.5T. Various R 2 * quantification methods, based on Rician and non‐Rician noise models, were compared in the simulation, phantom, and human datasets. Results Non‐Rician R 2 * estimates were variably inaccurate in the high R 2 * range (>500 sec ‐1 ), with SNR‐dependent linear goodness‐of‐fit statistic (R 2 ) of 0.373–0.999. Rician R 2 * estimates were accurate even in the high R 2 * range, with high R 2 of 0.940–0.999 regardless of SNR. Non‐Rician R 2 * estimates were variably nonlinear at high MnCl 2 concentrations, with SNR‐dependent R 2 of 0.345–0.994. Rician R 2 * estimates were linear even at high MnCl 2 concentrations, with high R 2 of 0.923–0.994 regardless of SNR. Between‐method agreement of the R 2 * estimates was excellent in patients with low ferritin but poor in patients with high ferritin. Rician R 2 * estimates had excellent correlation with ferritin ( r = 0.966 P < 0.001). Conclusion Rician R 2 * estimates were most consistent in the high R 2 * conditions and under varying SNR, and may be more reliable when high iron load is suspected. J. MAGN. RESON. IMAGING 2015;42:1544–1559.