Keywords:
Abdomen, Liver, Haematologic, MR-Elastography, MR, Elastography, Technical aspects, Technology assessment, Imaging sequences, Cirrhosis, Haematologic diseases, Tissue characterisation
Authors:
I. Mussetto, J. Matos, L. Bacigalupo, M. De Cesari, S. Perugin Bernardi, F. Paparo, G. A. Rollandi; Genoa/IT
DOI:
10.26044/ecr2019/C-0901
Methods and materials
Eighty-nine magnetic resonance elastography (MRE) examinations performed from May 2017 to March 2018 in eighty-nine consecutive patients (mean age 53 years; male patients n=71 [80%]) were retrospectively analyzed.
MRE examinations were performed on a 1.5T scanner (Signa HDx,
General Electric Medical Systems,
Milwaukee,
WI,
USA).
Patients underwent MRE to diagnose or to stage liver fibrosis.
Table 1 shows the characteristics of study populations.
Low amplitude mechanical waves at 60 Hz are generated through the liver during imaging,
using a passive driver device in contact with the anterior body wall (Fig.
1).
A two-dimensional gradient-echo sequence using motion-encoding gradients is used to map the shear waves traveling through the liver.
4 MR elastography sections are obtained in each patient during a breath-hold at the end of expiration.
4 quantitative images displaying shear stiffness (elastograms) are then generated by processing the acquired raw-data images of propagating shear waves using the direct inversion method with a commercially available software (MR Touch; GE Healthcare).
An additional confidence algorithm generated confidence maps overlayed on the elastograms,
to indicate the highest regions of statistical confidence in which is possible to place the regions of interest (ROIs) to calculate the liver stiffness (Fig.
2).
The standard MRE protocol also included T2* decay using an axial two-dimensional,
spoiled,
multiecho GRE sequence with both 8 and 16 echoes.
Technical failure was determined as no pixel value in the confidence map or disorganized wave pattern on wave image (Fig.
3 - 4).
Logistic regression analysis was performed to detect predictive factors for technical failure of MRE.
ROC curve and Youden index were used to identify a threshold value of T2* decay that maximized prediction of MRE failure.