MRI-Based Liver Iron Content Determination at 3T in Regularly Transfused Patients by Signal Intensity Ratio Using an Alternative Analysis Approach Based on R2* Theory

Abstract

▼Objectives: To evaluate the feasibility of addressing liver iron content (LIC) in regularly transfused patients by MR imaging at 3 T based on the signal intensity ratio (SIR). An innovative data analysis approach was developed for this purpose. Methods: 47 consecutive examinations of regularly transfused patients were included. In all cases, we expected high LIC levels. Patients were scanned with MRI at 3 T with multi-echo gradient echo sequences (GRE) at four different flip angles between 20°and 90°with echo times (TE) ranging from 0.9 to 9.8 ms. Spin-echo protocols were acquired to determine the LIC with a reference MRI method working at 1.5 T. 3 T GRE data were analyzed using the liver-to-muscle SIR. Since the method known for 1.5 T was not expected to be applicable for analyzing 3 T data, theoretic dependence of the SIR on the LIC was derived from the equation describing R 2 * signal decay. Obtained SIR values were correlated to reference LIC to get a relation for calculating LIC from SIR quantities. LIC values and their uncertainties were determined from GRE data and correlated to LIC reference values. For two LIC thresholds, the diagnostic accuracy was determined. Results: LIC was reliably determined from SIR in our patient cohort even for large LIC values. Median of LIC uncertainties was 10 %, and the diagnostic accuracy was 0.92 and 0.91, respectively. Conclusion: Determination of even high LIC, resulting in small SIR values, is feasible at 3 T using appropriate SIR analysis.

Liver Iron Content Determination Using a Volumetric Breath‐Hold Gradient‐Echo Sequence With In‐Line R2* Calculation

“… 22,31 Jhaveri et al, on the other hand, found that there was an almost identical R 2 *‐LIC‐calibration between monoexponential fit and the analysis accounting for effects of fat–water dephasing 20 . Our calibration of R 2 * values computed with respect to the influence of fat signal is comparable with theirs and those of other studies 16,32,33 . Sariganni et al reported GRE studies using a monoexponential fit with diagnostic accuracy worse than our results, indicating that reliability of the monoexponential approach may be impaired by the influence of fat fraction on GRE signal.…”

MRI Appearance of Focal Lesions in Liver Iron Overload

“…The most used SIR method was proposed by Gandon et al It consists of five GRE sequences acquired during separate breath holds, with a fixed TR of 120 ms, slice thickness of 10 mm, FOV of 40 cm, matrix size of 256 × 128, flip angle of 20 • and multiple increasing TEs to obtain different weighted images: T1, proton-density and T2*-weighted sequences [28]. More recently, the technique has been reproduced on 3 T scanners [29]. Acquisition protocols are available online for 1.0 T, 1.5 T, and 3.0 T scanners [30].…”

Iron deposition quantification: Applications in the brain and liver

“…Recent SIR investigations mainly concern the application for LIC quantification at 3.0T . Theoretically, 3T might show better sensitivity and accuracy than 1.5T, thereby potentially improving the diagnosis of low iron load.…”