Evaluation of two-point Dixon water-fat separation for liver specific contrast-enhanced assessment of liver maximum capacity.

Gadoxetic acid-enhanced magnetic resonance imaging has become a useful tool for quantitative evaluation of liver capacity. We report on the importance of intrahepatic fat on gadoxetic acid-supported T1 mapping for estimation of liver maximum capacity, assessed by the realtime 13C-methacetin breathing test (13C-MBT). For T1 relaxometry, we used a respective T1-weighted sequence with two-point Dixon water-fat separation and various flip angles. Both T1 maps of the in-phase component without fat separation (T1_in) and T1 maps merely based on the water component (T1_W) were generated, and respective reduction rates of the T1 relaxation time (rrT1) were evaluated. A steady considerable decline in rrT1 with progressive reduction of liver function could be observed for both T1_in and T1_W (p < 0.001). When patients were subdivided into 3 different categories of 13C-MBT readouts, the groups could be significantly differentiated by their rrT1_in and rrT1_W values (p < 0.005). In a simple correlation model of 13C-MBT values with T1_inpost (r = 0.556; p < 0.001), T1_Wpost (r = 0.557; p < 0.001), rrT1_in (r = 0.711; p < 0.001) and rrT1_W (r = 0.751; p < 0.001), a log-linear correlation has been shown. Liver maximum capacity measured with 13C-MBT can be determined more precisely from gadoxetic acid-supported T1 mapping when intrahepatic fat is taken into account. Here, T1_W maps are shown to be significantly superior to T1_in maps without separation of fat.

Hepatobiliary MRI: Signal intensity based assessment of liver function correlated to 13C-Methacetin breath test.

Gadoxetic acid (Gd-EOB-DTPA) is a paramagnetic MRI contrast agent with raising popularity and has been used for evaluation of imaging-based liver function in recent years. In order to verify whether liver function as determined by real-time breath analysis using the intravenous administration of 13C-methacetin can be estimated quantitatively from Gd-EOB-DTPA-enhanced MRI using signal intensity (SI) values. 110 patients underwent Gd-EOB-DTPA-enhanced 3-T MRI and, for the evaluation of liver function, a 13C-methacetin breath test (13C-MBT). SI values from before (SIpre) and 20 min after (SIpost) contrast media injection were acquired by T1-weighted volume-interpolated breath-hold examination (VIBE) sequences with fat suppression. The relative enhancement (RE) between the plain and contrast-enhanced SI values was calculated and evaluated in a correlation analysis of 13C-MBT values to SIpost and RE to obtain a SI-based estimation of 13C-MBT values. The simple regression model showed a log-linear correlation of 13C-MBT values with SIpost and RE (p < 0.001). Stratified by 3 different categories of 13C-MBT readouts, there was a constant significant decrease in both SIpost (p ≤ 0.002) and RE (p ≤ 0.033) with increasing liver disease progression as assessed by the 13C-MBT. Liver function as determined using real-time 13C-methacetin breath analysis can be estimated quantitatively from Gd-EOB-DTPA-enhanced MRI using SI-based indices.

Gd-EOB-DTPA-enhanced T1 relaxometry for assessment of liver function determined by real-time 13C-methacetin breath test.

OBJECTIVES: To determine whether liver function as determined by intravenous administration of 13C-methacetin and continuous real-time breath analysis can be estimated quantitatively from gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) relaxometry. METHODS: Sixty-six patients underwent a 13C-methacetin breath test (13C-MBT) for evaluation of liver function and Gd-EOB-DTPA-enhanced T1-relaxometry at 3 T. A transverse 3D VIBE sequence with an inline T1 calculation based on variable flip angles was acquired prior to (T1 pre) and 20 min post-Gd-EOB-DTPA (T1 post) administration. The reduction rate of T1 relaxation time (rrT1) and T1 relaxation velocity index (∆R1) between pre- and post-contrast images was evaluated. 13C-MBT values were correlated with T1post, ∆R1 and rrT1, providing an MRI-based estimated 13C-MBT value. The interobserver reliability was assessed by determining the intraclass correlation coefficient (ICC). RESULTS: Stratified by three different categories of 13C-MBT readouts, there was a constant increase of T1 post with increasing progression of diminished liver function (p ≤ 0.030) and a constant significant decrease of ∆R1 (p ≤ 0.025) and rrT1 (p < 0.018) with progression of liver damage as assessed by 13C-methacetin breath analysis. ICC for all T1 relaxation values and indices was excellent (> 0.88). A simple regression model showed a log-linear correlation of 13C-MBT values with T1post (r = 0.57; p < 0.001), ∆R1 (r = 0.59; p < 0.001) and rrT1 (r = 0.70; p < 0.001). CONCLUSION: Liver function as determined using real-time 13C-methacetin breath analysis can be estimated quantitatively from Gd-EOB-DTPA-enhanced MR relaxometry. KEY POINTS: • Gd-EOB-DTPA-enhanced T1 relaxometry quantifies liver function • Gd-EOB-DTPA-enhanced MR relaxometry may provide parameters for assessing liver function before surgery • Gd-EOB-DTPA-enhanced MR relaxometry may be useful for monitoring liver disease progression • Gd-EOB-DTPA-enhanced MR relaxometry has the potential to become a novel liver function index.