Wei Tang1, Yao Huang1, Ning Wu1, Wenwen Lu1, Linlin Qi1, and Bing Wu2
1Diagnostic Radiology, Cancer Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China, People's Republic of, 2GE heathcare MR research China, Beijing, China, People's Republic of
Synopsis
Magnetic resonance
(MR) elastography depitcs the elastic
properties of tissues of interest has been primarily applied in the work-up of
diagnosis for hepatic fibrosis. Theoretically, interference fringes could be visualized on the elastogram due to the
miscalculation of the interaction between the attenuated propagations of shear
wave and the tissue overlying or surrounding to the investigated subject, which
might be one of the main concern that limited the clinical potentials of MRE.
We propose an investigation on the feasibility of MR elastography in
characterizing the mechanical properties of
anterior mediastinal masses with the consideration of the relatively
superficial location of these entities, therefore few interactions between the
shear wave and subject unexpected were produced during the process of
elasticity mapping. It was demonstrated in our study that anterior mediastinal
mass in various etiology of thymic carcinoma, thymoma, and lymphoma has
distinct elastic properties. MR elastography
was helpful in distinguishing the thymic carcinoma from lymphoma.Objectives
Magnetic
resonance (MR) elastography allows assessing the elasticity of interior tissues
without digital palpation. Although studies have shown its feasibilities in
neuro, abdomen, extremity and cardiac imaging, its clinical applications have
been constrained in hepatic imaging, mainly due to the constraints of imaging
setup. Anterior mediastinal masses were usually interpreted on CT and MR
imaging with an inconsistent diagnostic accuracy in the differentiation between
thymic carcinoma and primary mediastinal lymphoma, and evidence suggestive of definitive
diagnosis that strongly associated with treatment was needed to be obtained
with invasive procedure of biopsy. In this work, we attempt to extent the use
of MRE to the mediastinum, it is hoped that with the stiffness property of the
tissue revealed on elastogram, MRE may help distinguish thymic carcinoma from primary mediastinal lymphoma.
Methods
Fourteen patients presenting with anterior
mediastinal mass were enrolled in the study. Institutional review board approval and informed
consent were obtained prior to
the study. All the patients underwent MRI examination consisting of routine
protocol and MRE on a 3.0T whole body scanner equipped with an 8-channel coil. MRE setup for hepatic imaging was used in our study. Circular
or elliptical ROIs were placed on the mass at its largest axial diameter on T2-wighted imaging, covering
greater than 75% of the areas of the mass. The identical ROIs were then copied
to the corresponding elastogram slices for each lesion, and the averaged stiffness values within the ROI were
recorded. Two-way ANOVA test was used to examine the difference of stiffness
value with the correlation of pathological results.
Results
The
pathological results of those 20 patients were as following: 5 patients were
presented with thymic carcinoma, 5 were presented with thymoma,
and 4 were presented with primary mediastinal
lymphoma. The average stiffness
value was 6282.7 ± 2395.5 kPa for thymic carcinoma, 4478.7 ± 1089.2 kPa for
thymoma, 3431.1 ± 1055.1 kPa for lymphoma, respectively. It
was seen that the measured stiffness
value of thymic carcinoma was significantly higher than
that of lymphoma (
p = 0.048). However, there was
no statistical difference in the measured stiffness value between
either the groups of thymic carcinoma and thymoma (
p = 0.130), or thymoma and lymphoma (
p = 0.426).
Discussion and conclusion
In this work, the application of MR elastography
was transferred to the imaging of mediastinum, the equipment and acquisition
method were as the same as that of hepatic imaging. It was observed that elastograms
with good image quality were obtained, and the stiffness measurements on
patients with various pathologies indicated distinctive elastic properties of
these lesions. Particularly, the stiffness level of thymic carcinoma was seen to be significantly higher than that of
lymphoma. It
was demonstrated the feasibility of MRE
in distinguishing thymic carcinoma from primary mediastinal
lymphoma, which is an abtacle for conventional imaging of CT and MRI.
Acknowledgements
No acknowledgement found.References
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