Overload hepatitides: quanti-qualitative analysis

Abstract

Diffuse liver diseases have a definitive radiological importance due to the ability of MR imaging to demonstrate abnormalities before the patient is symptomatic or the liver damage is advanced. Biopsy procedures are invasive, may lead to complications and have a sample bias. Imaging biomarkers target to fat, water, and iron tissue concentrations may be considered as hepatic virtual biopsies. There is a need to identify a rapid and practicable method to accurately quantify liver steatosis, differentiate steatohepatitis from simple steatosis, grade the necroinflammatory activity, calculate the liver iron burden and monitor overload progression. MR is used in the evaluation of diffuse liver disorders with accurate approaches such as the use of chemical shift, Dixon vector analysis, turbo spin echo fat suppression, and T2* gradient echo techniques. These methods are influenced by some factors like proportional ambiguity, T1 and T2* effects on signal decay, adding a significant bias in the combined fat-water-iron quantification. A GRE multi-echo chemical shift sequence was configured to independently calculate fat, water, and iron parametric liver images. It is now necessary to conduct a pilot project in order to validate this method in a group of subjects without and with different grades of fat, water, and iron liver changes.

Accurate simultaneous quantification of liver steatosis and iron overload in diffuse liver diseases with MRI

“…The 2D MECSE-MR sequence used 12 echoes (TE's = 0.99 to 8.69, short echo spacing = 0.7 ms; TR = 10 ms) with a 10°flip angle [23] to minimize T1 bias. The whole liver was covered under end-expiratory phase single breath-hold acquisition (34 slices; voxel dimensions, 3 9 3 mm; slice thickness, 7 mm; 0.3 mm gap; reconstruction voxel size, 2 9 2 mm; field of view, 375 9 302 mm; parallel imaging effective acceleration factor, 1.8; bandwidth, 2433 hertz per pixel).…”

“…The magnitude and phase reconstructions allow two fitting procedures [23,27]. The complex phase information estimates the resonance peak of the larger component, either water or fat, to generate frequency distribution maps.…”

“…The MECSE-MR results must be adjusted for those factors biasing the voxel signal intensity of fat and water, such as T1 relaxation time, T2* decay effect, eddy currents, noise, and fat spectral complexity. MECSE-MR sequences independently estimate liver fat fraction and T2*, allowing for the simultaneous assessment of liver iron [10,14,20,22,23].…”

Liver MRI: From basic protocol to advanced techniques

“…The T2* estimation is used to correct the effect of T2* in PDFF quantification. Moreover, because liver T2* is related to the amount of iron deposition, it can also be used for simultaneous quantification of iron deposits [36,[40][41][42]. Nevertheless, because large iron content lead to extremely low signal in GRE sequences, PDFF measurements may be corrupted in livers with severe iron overload [41].…”

“…As mentioned above, MECSE-MR sequences, the same as described for fat quantification, can also be used for R2* estimation and LIC quantification (Figs. 9 and 10) [40][41][42]48] while simultaneously assessing the liver fat content (Figs. 9 and 10).…”